THE USE OF GASIFICATION ASH IN CEMENT AND CONCRETE

THE USE OF GASIFICATION ASH IN CEMENT AND

CONCRETE

HANLI DU PLESSIS

A d isser ta t ion submit ted in par t ia l fu l f i l lment for the degree of

MASTER OF ENGINEERING (STRUCTURAL ENGINEERING)

In the

FACULTY OF ENGINEERING

UNIVERSITY OF PRETORIA

November 2005

UUnniivveerrssiittyy ooff PPrreettoorriiaa eettdd –– DDuu PPlleessssiiss HH ((22000066))

SUMMARY

THE USE OF GASIFICATION ASH IN CEMENT AND

CONCRETE

H DU PLESSIS

Superv isor : P ro fesso r E .P . Kea rs l ey

Depar tm ent : C i v i l Eng inee r i ng

Univers i ty : Un i ve r s i t y o f P re t o r i a

Degree : Mas te r o f Eng inee r i ng (S t ruc tu ra l Eng inee r i ng )

Cemen t i s an essen t i a l ma te r i a l i n t oday ’ s soc i e t y because , as a ma jo r

cons t i t uen t o f conc re te , i t f o rms a f u ndamen ta l e l emen t o f any h ous ing

o r i n f r as t ruc tu re deve lopme n t . The chem ica l p rocess o f mak ing cemen t

c l i n ke r p roduces CO 2 , a ma jo r g reenhouse gas con t r i bu t i ng t o c l ima te

change . Th i s makes i t impe ra t i ve f o r us t o f i nd ways o f us i ng t h i s

r esou rce more e f f i c i en t l y .

Us ing was te f r om o the r i ndus t r i es , as a r aw ma te r i a l i s a huge

oppo r tun i t y f o r t he cemen t i ndus t r y t o r educe i t s env i r onmen ta l impac t .

Cemen t ex tende rs a re used as a subs t i t u te f o r some o f t he Po r t l and

cemen t i n conc re te . The re asons f o r t he use o f ex tend e rs , i s a g row ing

awa reness o f t he eng inee r i ng , econom ica l and eco log i ca l bene f i t s and

t he va r i e t y o f use fu l enhancemen ts , wh i ch t hey g i ve t o t he conc re te

p rope r t i es .


The a im o f t he r e sea rch i s t o de te rm ine whe the r a ga s i f i ca t i on ash can

be used as a cemen t ex tende r i n conc re te . I n t h i s s tudy de ta i l o f t he

manu fac tu r i ng o f Po r t l and cemen t (PC) , cemen t c l asses and t he

hyd ra t i on o f cemen t w i l l be d i scussed . Cons ide ra t i on w i l l be g i ven t o

p rope r t i es l i ke t he op t im i sa t i on o f su l pha te and f i neness o f cemen t .

The pa r t i c l e s i ze d i s t r i bu t i on i s d i s cussed w i t h spec i f i c r e f e rence t o t he

Ros in -Rammle r d i s t r i bu t i on f unc t i on . The use o f coa l combus t i on by -

p roduc t s , spec i f i ca l l y f l y ash , i n conc re te w i l l be d i scussed .

Cons ide ra t i on w i l l be g i ven t o p rope r t i es l i ke shape , pa r t i c l e s i ze ,

m ine ra l og i ca l and chem ica l compos i t i on , du rab i l i t y and t he chem ica l

r equ i r emen ts f o r us i ng f l y as h as a cemen t ex tende r .

The phys i ca l p rope r t i es o f gas i f i ca t i on ash i nd i ca ted t ha t t he

gas i f i ca t i on ash , g r i nded sepa ra te and i n t e rg round had s im i l a r pa r t i c l e

s i ze d i s t r i bu t i ons . The chem ica l and m ine ra l og i ca l compos i t i on o f a

gas i f i ca t i on ash samp le was i nves t i ga ted , and i t was f ound t ha t

gas i f i ca t i on ash has an angu la r shape and a s im i l a r chem ica l

compos i t i on as f l y ash .

The chem ica l r equ i r emen ts o f t he gas i f i ca t i on ash mee t t he ma jo r i t y o f

t he r equ i r emen ts spec i f i ed f o r cemen t ex tende rs . Whe re l im i t s a re

exceeded i t i s by a ve r y na r row marg in .

The e f f ec t o f a gas i f i ca t i on ash on t he sho r t and l ong t e rm p ro pe r t i es

o f conc re te o f bo th i n t e rb l end ing and i n t e rg r i nd i ng was i nves t i ga ted .

The use o f gas i f i ca t i on as h as cemen t ex tende r does no t have a

nega t i ve impac t on t he s t r eng th deve l opmen t o f conc re te . The re was no

reduc t i on i n t he t ens i l e s t r eng th o f conc re te . Gas i f i ca t i on ash does no t

have a d e t r imen ta l e f f ec t on s t i f f ness o f conc re te , and d i d no t sh r i nk o r

c reep s i gn i f i can t l y mo re t han conc re te con ta i n i ng f l y ash .

The po ros i t y and pe rmeab i l i t y does no t i n c rease when gas i f i ca t i on ash

i s used as a cemen t ex tende r . Gas i f i ca t i on as h shou ld t he re fo re no t

dec rease t he du rab i l i t y o f conc re te .


SAMEVATTING VAN

DIE BENUTTING VAN GASIFIKASIE-AS IN SEMENT EN

BETON

H DU PLESSIS

Promoto r : P ro fesso r E .P . Kea rs l ey

Depar te ment : S i v i e l e I ngen ieu rswese

Univers i te i t : Un i ve r s i t e i t van P re to r i a

Graad: Mag i s te r van I ngen ieu rwese (S t ruk tuu r

I ngen ieu rswese )

Semen t i s ‘ n be lang r i ke ma te r i aa l i n d i e hedendaagse gemeenskap

wan t as ‘ n hoo f ve r vang ingsma te r i aa l i n be ton , vo rm d i t ‘ n be lang r i ke

e l emen t van e n ige behu i s i ng o f i n f r as t r uk tuu r on tw i kke l i ng . D ie

chem iese p roses t ydens d i e ve r vaa rd i g i ng van semen t s t e l CO 2 , ‘ n gas

wa t l e i t o t k l imaa t sve rande r i ng , v r y . H ie rd i e aspek maak d i t be l ang r i k

v i r ons om man ie re t e k r y om h ie rd i e b ron mee r e f f ek t i e f t e geb ru i k .

Benu t t i ng van a f va l ma te r i a l e van ande r i ndus t r i eë as a r ou ma te r i aa l

i s a g roo t kans v i r d i e s emen t i n dus t r i e om hu l o mgew ing s impak t e

ve rm inde r . Semen t - ve rvang e rs wo rd geb ru i k as ve rva ng ing v i r ‘ n dee l

van d i e Po r t l and Semen t i n be ton . The redes v i r d i e geb ru i k van

ve rvange rs i s ‘ n g roe iende bewusword ing van d i e i ngen ieu rs


ekonom iese en eko log iese voo rd ee l asook d i e ve r ske idenhe id

ve rbe te r i ngs wa t hu l l e byd ra t o t d i e e i enskappe van be ton .

D ie doe l van d i e navo rs i ng i s om te bepaa l o f gas i f i kas i e -as geb ru i k

kan wo rd as ‘ n semen t - ve rvange r i n be ton . I n h i e rd i e s t ud ie wo rd

i n l i g t i ng oo r d i e ve r vaa rd i g i ng van Po r t l and semen t , semen t k l asse en

d i e h i d ras i e van semen t besp reek . Kons ide ras i e wo rd gegee aan

e i enskappe soos d i e op t im i se r i ng van su l f aa t en d i e f ynh e id van

semen t . D ie pa r t i ke l g roo t te ve r sp re i d i ng wo rd besp reek me t spes i f i e ke

ve rwys ing na d i e Ros in -Rammle r ve r sp re i d i ng funks ie . D ie geb ru i k van

s teenkoo l as a f va l p roduk te , spes i f i e k V l i egas , i n be ton wo rd besp reek .

Kons ide ras i e wo rd gegee aan e i enskappe soos vo rm , pa r t i ke l g roo t t e ,

m ine ra l og ie en chem iese sames te l l i ng , duu rsaamhe id en d i e chem iese

ve re i s t es v i r d i e geb ru i k van V l i egas as ‘ n semen t - ve r vange r .

D ie f i s i ese e i enskappe va n gas i f i kas i e -as du i daa rop da t ga s i f i kas i e -

as , apa r t gemaa l en saam gemaa l d i ese l f de pa r t i ke l g roo t t e

ve r sp re i d i ngs he t . D ie chemiese en m ine ra l og iese sames te l l i ng van

gas i f i kas i e -as i s onde rsoek en daa r i s gev i nd da t gas i f i kas i e -as ‘ n

hoek ige vo rm en d i ese l f de sames te l l i ng as v l i egas he t .

The chem iese ve re i s t es v i r gas i f i kas i e as vo l doen aan d i e me e rde rhe id

van d i e ve re i s t es gespes i f i see r v i r semen t - ve r vange rs . Waa r d i e

l im ie te oo rsk re i wo rd i s d i t s l egs me t ‘ n k l e i n ma rg in .

D ie e f f ek van gas i f i kas i e as op d i e ko r t en l ang t e rmyn e i enskappe van

be ton v i r be i de saamgemen g en saamgemaa l i s onde rsoek . D ie geb ru i k

van gas i f i kas i e -as as ‘ n semen t - ve r vange r he t geen nega t i ewe impak

op d i e s te r k t e on tw i kke l i ng van be ton n i e . Daa r was geen ve rm inde r i ng

i n d i e t r eks te r k te van d i e be ton n i e . Gas i f i kas i e -as he t n i e ‘ n nade l i ge

e f f ek op d i e s t y f he id van d i e be ton en he t n i e besonde rs mee r gek r imp

o f k ru i p n i e as be ton me t v l i egas n i e .

D ie po ros i t e i t en pe rmeab i l i t e i t he t n i e ve rmee rde r as gas i f i kas i e -as

geb ru i k wo rd as ‘ n semen t - ve r vang e r n i e . Gas i f i kas i e -as sa l daa rvoo r

n i e d i e duu rsaamhe id van be ton ve rm inde r n i e .


ACKNOWLEDGEMENT

I w i sh t o exp ress my app re c i a t i on t o t he f o l l ow ing o rgan i za t i ons and

pe rsons who mad e t h i s d i sse r t a t i on poss ib l e .

a ) Saso l Techno logy Resea rch and Deve lopmen t f o r t he dona t i on o f

gas i f i ca t i on ash t es ted i n t h i s i nves t i ga t i on .

b ) P ro fesso r E .P Kea rs l ey , my p romo te r f o r he r gu idance and

suppo r t .

c ) The f o l l ow ing pe rsons f o r t he i r ass i s tance du r i ng t he cou rse o f

s t udy :

M r . D . Mos te r t

M r . H . Ma t j i e

M rs . S . Ve r r yn

M rs . J . Ca l l anan

Pe rsonne l o f t he conc re te l abo ra to r y o f t he C i v i l Eng inee r i ng

depa r tmen t o f t he Un i ve rs i t y o f P re t o r i a .

d ) My f a m i l y and f r i ends f o r t he i r encou ragemen t and suppo r t .


TABLE OF CONTENTS PAGE

1 . INTRODUCTION 1 -1

1 . 1 Backg round 1 -1

1 .2 Ob jec t i ves o f t he s t udy 1 -2

1 .3 Scope o f t he s t udy 1 -2

1 .4 Me thodo logy 1 -4

1 .5 O rgan i sa t i on o f t he r epo r t 1 -4

2. COM PON ENT S AND P ROP ERTI ES OF P ORTLA N D CE MEN T 2 -1

2 .1 I n t r oduc t i on 2 -1

2 .2 Cemen t Manu fac tu re 2 -1

2 .3 Cemen t C lasses 2 -4

2 .4 Hyd ra t i on o f Po r t l and Ceme n t 2 -5

2 . 4 .1 The hyd ra t i on o f C 3 S and C 2 S 2 - 5

2 . 4 .2 Hyd ra t i on o f C 3 A 2 -8

2 . 4 .3 Hyd ra t i on o f C 4 AF 2 -9

2 .5 Hea t o f Hyd ra t i on 2 -9

2 . 5 .1 Op t im i za t i on o f Cemen t Su lpha te 2 -10

2 .6 Spec i f i c Su r f ace A rea 2 -12

2 .7 Pa r t i c l e s i ze d i s t r i bu t i on 2 -12

2 . 7 .1 Ros in -Rammle r d i s t r i bu t i on f unc t i on 2 -13

2 .8 Conc lus i on 2 -15

3 . COMPOSIT ION AND PROPERTIES OF COAL ASH 3 -1

3 .1 In t roduc t i on 3 -1

3 .2 Coa l Ash 3 -2

3 .3 Pozzo lan i c Reac t ion 3 -4

3 .4 F l y Ash 3 -5

3 .4 .1 Phys ica l P roper t i es 3 -6

3 .4 .2 Chemica l Compos i t i on 3 -7

3 .4 .3 M inera log i ca l Compos i t i on 3 -8

3 .4 .4 Chemica l Spec i f i ca t ions 3 -8


3 .5 I n f l uence o f f l y ash on t he p rope r t i es o f conc re te 3 -9

3 .5 .1 F resh Conc re te 3 -9

3 .5 .1 .1 Wa te r Demand 3 -10

3 .5 .1 .2 Workab i l i t y 3 -11

3 .5 .2 Ha rdened Conc re te 3 -12

3 .5 .2 .1 Compres s i ve S t reng th Deve lopmen t 3 -12

3 .5 .2 .2 F l exu ra l S t r eng th 3 -15

3 .5 .2 .3 Modu lus o f E l as t i c i t y 3 -16

3 .5 .2 .4 D ry i ng Sh r i nkage 3 -17

3 .5 .2 .5 C reep 3 -18

3 .6 Durab i l i t y o f Conc re te 3 -19

3 .6 .1 Poros i t y 3 -19

3 .6 .2 Pe rmeab i l i t y 3 -19

3 .7 Advan tag es o f us i ng F l y ash i n Conc re te 3 -20

3 .8 Conc lus ion 3 -21

4 . E XPERI M ENTAL P ROGRA MME A ND TEST PROCE DURES

FOR C EM ENT 4 -1

4 . 1 I n t r oduc t i on 4 -1

4 .2 P repa ra t i on o f ma te r i a l s 4 -1

4 .3 Phys i ca l and chem ica l p rope r t i es o f gas i f i ca t i on ash 4 -4

4 .3 .1 Pa r t i c l e s i ze d i s t r i bu t i on 4 -4

4 .3 .1 .1 Pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s 4 -4

4 .3 .1 .2 Ros in -Rammle r pa r t i c l e s i ze

d i s t r i bu t i on pa rame te r s 4 -5

4 .3 .1 .3 Pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s 4 -7

4 .3 .2 Spec i f i c su r f ace a rea 4 -8

4 .3 .3 Scann ing e l ec t r on m i c roscopy (SEM) 4 -9

4 .3 .4 X - ra y f l u o rescence spec t roscopy (XRF) 4 -9

4 .3 .5 X - ra y d i f f r ac t i on spec t roscopy (XRD) 4 -10

4 .4 S tanda rd t es t s f o r cemen t i t i ous ma te r i a l s 4 -10

4 .4 .1 Su lphu r t r i o x i de con ten t

(SANS 50 196 -2 :1994 / SABS EN 196 -2 :1994 ) 4 -11

4 .4 .2 Loss on Ign i t i on

(SANS 50 196 -2 :1994 / SABS EN 196 -2 :1994 ) 4 -11


4 . 4 .3 F ree wa te r con ten t

(SANS 61 51 :1989 / SABS 11 51 :1989 ) 4 -12

4 .4 .4 Tes t f o r f i neness o f cemen t and Po r t l and cemen t

ex tende rs (SANS 6157 :2002 / SABS 1157 :2002 ) 4 -12

4 . 4 .5 Wa te r r equ i r emen t

(SANS 61 56 :1989 / SABS SM 1156 :1989 ) 4 -12

4 . 4 .6 S t r eng th f ac to r t es t

(SANS 50 196 -1 :1994 / SABS EN 196 -1 :1994 ) 4 -15

4 .4 .7 Soundness

(SANS 50 196 -3 :1994 / SABS EN 196 -3 :1994 ) 4 -17

4 .4 .8 Re la t i ve dens i t y ( LSA Me th od ) 4 -18

4 .5 Fac to r s Inves t i ga ted by Ca s t i ng Mo r ta r P r i sms 4 -18

4 .5 .1 D i f f e ren t G r i nd i ng T imes 4 -18

4 .5 .2 D i f f e ren t Gypsu m Pe rcen tages 4 -19

4 .5 .3 I so the rma l Conduc t i on Ca lo r ime t r y 4 -20

4 .5 .4 D i f f e ren t r ep lacemen ts pe rcen tages o f

Gas i f i ca t i on Ash 4 -20

5 . E XPERI M ENTAL P ROGRA MME A ND TEST PROCE DURES

FOR C ON CRETE 5 -1


5 .2 M i x des ign f o r conc re te m i xes 5 -1

5 .3 Tes t Conduc ted on F resh Conc re te M i xes 5 -2

5 .3 .1 S l ump Tes t (SANS 586 / SABS SM 8 2 :1994 ) 5 -2

5 .4 S t reng th Tes t 5 -3

5 .4 .1 Compres s i ve S t reng th Tes t

(SANS 58 63 -1 /SABS 863 -1994 ) 5 -3

5 .4 .2 Sp l i t t i ng Cy l i nde r Tes t f o r Tens i l e S t reng th

(SANS 62 5 :1994 /SABS SM 1253 :1994 ) 5 -4

5 .5 De fo rma t i on and Vo lume Ch ange o f Conc re te 5 -4

5 .5 .1 E -Va lue Tes t 5 -4

5 .5 .2 Sh r i nkage and C reep Tes t (ASTM C 512 -02 ) 5 -6

5 .6 Du rab i l i t y 5 -8

5 .6 .1 Po ros i t y Tes t 5 -8

5 .6 .2 Oxygen Pe rmeab i l i t y Tes t 5 -9


6 . TEST RESULTS AND D ISCUSSION ON CEMENT TESTS 6 -1


6 .2 Phys i ca l P rope r t i es 6 -1

6 .2 .1 Pa r t i c l e S i ze D i s t r i bu t i on Tes t 6 -1

6 .2 .2 Shape o f Pa r t i c l es 6 -10

6 .3 Chem ica l P rope r t i es 6 -12

6 .3 .1 XRF 6 -12

6 .3 .2 XRD 6 -14

6 .3 .3 S tanda rd Tes t s f o r Cemen t i t i ous Ma te r i a l s 6 -15

6 .4 E f f ec t o f G r i nd i ng t ime on t he P rope r t i es o f I n t e rb l ended

Gas i f i ca t i on Ash and Ceme n t 6 -16

6 .4 .1 Mo r ta r P r i sm Compress i ve S t reng th 6 -16

6 .4 .2 Mo r ta r P r i sms F lexu ra l S t r eng th 6 -17

6 .4 .3 Pa r t i c l e S i ze D i s t r i bu t i on 6 -19

6 .5 E f f ec t o f G r i nd i ng t ime on t he P rope r t i es o f I n t e rg round



6 .5 .2 Mo r ta r P r i sm F lexu ra l S t r eng th 6 -23


6 .6 E f f ec t o f Gypsu m Con ten t on t he P rope r t i es o f I n t e rg round




6 .6 .3 Hea t o f Hyd ra t i on 6 -29

6 .7 E f f ec t o f Rep lacemen t Leve l s on t he P rope r t i es o f

I n t e rg round Gas i f i ca t i on Ash and Cemen t 6 -32




6 .8 Compar i son be tween Manu fac tu red and Commerc i a l Cemen t 6 -38


6 .8 .2 F l exu ra l Mo r ta r P r i sm S t reng ths 6 -39

6 .8 .3 Hea t o f Hyd ra t i on 6 -41



7 . TEST RESULTS AND D ISCUSSION ON CONCRETE T ESTS 7 -1


7 .2 Tes t s Conduc ted on F resh Conc re te 7 -1

7 .2 .1 S l ump Tes t 7 -1

7 .3 S t reng th Tes t s 7 -2

7 .3 .1 Conc re te Cube Co mpress ion Tes t Resu l t s 7 -2

7 .3 .2 Tens i l e S t reng th Resu l t s 7 -3

7 .4 De fo rma t i on and Vo lume Ch ange o f Conc re te 7 -4

7 .4 .1 E - va lue t es t r esu l t s 7 -4

7 .4 .2 Sh r i nkage and C reep Tes t 7 -6

7 .5 Du rab i l i t y Tes t s 7 -9

7 .5 .1 Po ros i t y Tes t Resu l t s 7 -9

7 .5 .2 Oxygen Pe rmeab i l i t y Tes t Resu l t s 7 -11


8 . CON CLU SIONS A ND RE CO MMENDATIONS 8 -1

8 . 1 Conc lus i ons 8 -1

8 .2 Recomme nda t i ons 8 -3

9 . REFER E NCES 9 -1

APPENDI X A Cumu la t i ve Pa r t i c l e S i ze D i s t r i bu t i on o f Gas i f i ca t i on

Ash , Cemen t and Gas i f i ca t i on Ash and Ceme n t

I n t e rg round and I n te rb l ended

APPENDI X B Cumu la t i ve % Ove rs i ze Pa r t i c l e S i ze D i s t r i bu t i on f o r

Gas i f i ca t i on Ash , Cemen t a nd Gas i f i ca t i on Ash and

Cemen t I n t e rg round and I n te rb l ended

APPENDI X C Ros in -Rammle r D i s t r i bu t i on G raphs

APPENDI X D B la i ne Su r f ace A rea Ca l cu l a t i ons

APPENDI X E Mor ta r P r i sms S t reng th Summary f o r t he E f f ec t o f

G r i nd i ng T ime on t he P rope r t i es o f I n t e rb l ended

Gas i f i ca t i on Ash and Ceme n t

APPENDI X F Mor ta r P r i sms S t reng th Summary f o r t he E f f ec t o f

G r i nd i ng T ime on t he P rope r t i es o f I n t e rg round



APPENDI X G Mor ta r P r i sms S t reng th Summary f o r t he E f f ec t o f

Gypsu m Con ten t on t he P rope r t i es o f I n t e rg round


APPENDI X H Mo r ta r P r i sms S t reng th Summary f o r t he E f f ec t o f

Rep lacemen t Leve l s on t he P rope r t i es o f I n te rg round


APPENDI X I Mo r ta r P r i sms S t reng th summary f o r t he Comp ar i son

be tween Manu fac tu red and Commerc i a l Cemen t

APPENDI X J Cube S t reng th Summar y

APPENDI X K Spec i f i c C reep Summar y

APPENDI X L Po ros i t y Summary

APPENDI X M Pe rmeab i l i t y Ca l cu la t i ons


LIST OF F IGURES PAGE

F i gu re 2 .1 Cemen t manu fac tu re and t he i n f l uenced aspec t s

( f r om ww w.wbcsdcemen t . o rg , 2005 ) 2 -3

F i gu re 2 .2 Changes i n Ca 2 + i n so l u t i on cu r i ng C 3 S hyd ra t i on vs .

t ime i n t he absence and p resence o f gypsum

(F r i g i one , 1995 ) 2 -7

F i gu re 2 .3 Op t im i za t i on o f so l ub le ca l c i um su lpha te ( cemen ts )

(Newman , 2003 ) 2 -9

F i gu re 2 .4 Exa mp le o f no rma l hyd ra t i on o f Po r t l and cemen t

(Sandbe rg , 2004 ) 2 -11

F igu re 2 .5 D iag rammat i c r ep resen ta t i on o f Ros in -Ramle r

d i s t r i bu t i on f unc t i on (Wa in r i gh t and O lo runsogo ,

1999 ) 2 -15

F i gu re 3 .1 Coa l combus t i on by -p roduc t s 3 -4

F i gu re 3 .2 A mode rn pu l ve r i sed coa l - f i r ed t he rma l power s t a t i on

( f r om So u th A f r i can Coa l Ash Assoc ia t i on , 1999 ) 3 -6

F i gu re 3 .3 E l ec t r on m i c roscope pho tog raph o f f l y ash . 3 -7

F i gu re 3 .4 Re la t i onsh ip be tween wa te r r equ i r emen t and cemen t

r ep l acemen t w i t h f l y ash (Na i k , 1990 ) 3 -11

F igu re 3 .5 Deve lop men t o f compress i ve s t r eng ths o f Po r t l and

cemen t and f l y ash conc re tes ( f r om Sou th A f r i can

Coa l Ash Assoc ia t i on , 1999 ) 3 -13

F igu re 3 .6 E f f ec t o f coa rse f rac t i ons o f f l y ash on compress i ve

s t r eng th deve lopmen t o f conc re tes ( Josh i , 1982 ) 3 -14

F igu re 3 .7 Compres s i ve s t r eng ths o f PC and PC /30FA a t d i f f e ren t

t empe ra tu res (Sou th A f r i can Coa l Ash Assoc ia t i on ,

1999 ) 3 -15

F i gu re 3 .8 The i n f l uence o f FA con ten t o f t he cemen t i t i ous

ma te r i a l on t he f l exu ra l / compress i ve s t r eng th r a t i o o f

conc re te ( f r om So u th A f r i can Coa l Ash Assoc ia t i on ,

1999 ) 3 -16

F i gu re 3 .9 The i n f l uence o f FA on t he e l as t i c modu lus / compress i ve

s t r eng th o f conc re te ( f r om Sou th A f r i can Coa l Ash

Assoc ia t i on , 1999 ) 3 -17


http://www.wbcsdcement.org/

F igu re 3 .10 D ry i ng sh r i nkage o f conc re te i nco rpo ra t i ng f l y ash

(Yuan , 1983 ) 3 -18

F i gu re 4 .1 Labo ra to r y ba l l m i l l u sed i n expe r ime n t 4 -2

F i gu re 4 .2 S tee l ba l l s used f o r g r i nd i ng 4 -2

F i gu re 4 .3 Cumu la t i ve pa r t i c l e s i ze o f s t ee l ba l l s 4 -3

F i gu re 4 .4 Samp le o f gas i f i ca t i on ash c l i n ke r 4 -4

F i gu re 4 .5 Exponen t i a l f i t f o r cumu la t i ve % ove rs i ze pa r t i c l e

s i ze d i s t r i bu t i on 4 -5

F i gu re 4 .6 Ros in -Rammle r d i s t r i bu t i on g raph 4 -6

F i gu re 4 .7 Exp lana t i on o f Ros in -Rammle r d i s t r i bu t i on pa rame te r s 4 -6

F i gu re 4 .8 Cumu la t i ve % ove rs i ze d i s t r i bu t i on pa rame te r s 4 -7

F i gu re 4 .9 Cumu la t i ve % ove rs i ze i n t e r va l s f o r 3µm and 30µm 4 -8

F i gu re 4 .10 Appa ra tus t o de te rm ine spec i f i c su r face a rea 4 -9

F i gu re 4 .11 Pho to o f samp le on f l ow t ab le a f t e r mou ld i s r emoved 4 -14

F igu re 4 .12 Pho to o f d i ame te r measu remen ts o f f l ow t ab le t es t 4 -15

F igu re 4 .13 Pho to o f mou ld used 4 -15

F igu re 4 .14 Le Cha te l i e r mou lds i n hum id i t y cab ine t 4 -17

F i gu re 5 .1 Measu r i ng t he s l ump (Add i s , 2001 ) 5 -3

F i gu re 5 .2 Pho to o f l ab se t - up f o r measu r i ng sh r i nkage and

C reep 5 -7

F i gu re 5 .3 Pho to o f po ros i t y t es t se t up 5 -9

F i gu re 6 .1 G raph o f cumu la t i ve pa r t i c l e s i ze d i s t r i bu t i on o f

cemen t and gas i f i ca t i on ash (g r i nded sepa ra te and

i n t e rg round ) 6 -2

F i gu re 6 .2 Cumu la t i ve pa r t i c l e s i zes fo r gas i f i ca t i on ash and

cemen t i n t e rg round 6 -3

F i gu re 6 .3 Summary o f exponen t i a l f i t t ed f unc t i ons f o r t he

cumu la t i ve % ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on 6 -3

F i gu re 6 .4 Summary o f Ros in -Rammle r d i s t r i bu t i ons 6 -4

F i gu re 6 .5 Re la t i on be tween g r i nd i ng t ime and pos i t i on

pa rame te r X o 6 - 7

F i gu re 6 .6 Re la t i onsh ip be tween g r i nd i ng t ime and s l ope

pa rame te r ( n ) 6 -8

F i gu re 6 .7 Scann ing e l ec t r on m i c roscope pho to o f f l y ash 6 -10


F igu re 6 .8 Scann ing e l ec t r on m i c roscope pho to o f gas i f i ca t i on

a sh 6 -11

F i gu re 6 .9 G raph i nd i ca t i ng B la i ne su r f ace a rea 6 -11

F i gu re 6 .10 XRD resu l t s f o r gas i f i ca t i on ash 6 -14

F igu re 6 .11 Compres s i ve s t r eng ths f o r i n t e rb l end ing gas i f i ca t i on

ash and cemen t 6 -16

F igu re 6 .12 F l exu ra l s t r eng ths f o r i n t e rb l end ing gas i f i ca t i on ash

and cemen t 6 -18

F igu re 6 .13 Re la t i on be tween compress i ve s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on pos i t i on pa rame te r (X o )

f o r i n t e rb l end ing gas i f i ca t i on ash and cemen t 6 -19

F i gu re 6 .14 Re la t i on be tween compress ion s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on s l ope (n ) pa rame te r f o r

i n t e rb l end ing gas i f i ca t i on ash and cemen t 6 -20

F i gu re 6 .15 Re la t i on be tween compress ion s t r eng th and pa r t i c l e

s i ze d i s t r i bu t i on pa rame te r s f o r i n t e rb l end ing

gas i f i ca t i on ash and cemen t 6 -21

F igu re 6 .16 Compres s i ve S t reng th f o r i n t e rg r i nd i ng gas i f i ca t i on

ash and cemen t 6 -22

F igu re 6 .17 F l exu ra l s t r eng ths f o r i n t e rg r i nd i ng gas i f i ca t i on ash

and cemen t 6 -24

F igu re 6 .18 Re la t i on compress i ve s t r eng ths and Ros in -Rammle r

d i s t r i bu t i on pos i t i on pa rame te r (X o ) f o r i n t e rg r i nd i ng

gas i f i ca t i on ash and cemen t 6 -25

F igu re 6 .19 Re la t i on be tween 28 -day compress ion s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on s l ope (n ) pa rame te r 6 -26

F igu re 6 .20 Re la t i on be tween 28 -day compress ion s t r eng th and

pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s 6 -27

F igu re 6 .21 Compres s i ve s t r eng ths f o r gypsum con ten t 6 -28


F igu re 6 .22 F l exu ra l s t r eng ths f o r gypsum con ten t 6 -29

F igu re 6 .23 Ra te o f hea t deve lopmen t f o r d i f f e ren t gypsum

pe r cen tages 6 -30

F igu re 6 .24 The d i f f e rence i n t he r a te o f hea t evo lu t i on f o r

d i f f e ren t gypsum p e rcen tages cemen t and pu re PC

cemen t 6 -31

F igu re 6 .25 To ta l hea t o f hyd ra t i on o f d i f f e ren t gypsum pe rcen tage

cemen ts a t 25 ºC 6 -32

F igu re 6 .26 Compres s i ve s t r eng th f o r d i f f e ren t r ep lacemen t

l e ve l s o f gas i f i ca t i on ash 6 -33

F igu re 6 .27 F l exu ra l s t r eng ths f o r d i f f e ren t r ep lac emen t l eve l s o f

gas i f i ca t i on ash 6 -34


d i s t r i bu t i on pos i t i on pa rame te r (X o ) f o r r ep lacemen t

l e ve l s o f gas i f i ca t i on ash 6 -36

F igu re 6 .29 Re la t i on be tween 28 -day compress ion s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on s l ope (n ) pa rame te r 6 -36

F igu re 6 .30 Re la t i on be tween 28 -day compress ion s t r eng th and

pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s o f r ep l acemen t

l e ve l o f gas i f i ca t i on ash 6 -37

F igu re 6 .31 Compres s i ve s t r eng ths f o r manu fac tu red and

commerc i a l l y ava i l ab l e cemen t 6 -38

F igu re 6 .32 F l exu ra l s t r eng ths f o r manu fac tu red and


F igu re 6 .33 Ra te o f hea t deve lopmen t f o r manu fac tu red and


F i gu re 7 .1 S l ump t es t f o r conc re te m i xes 7 -2

F i gu re 7 .2 Conc re te cubes compress i on s t r eng th r esu l t s 7 -3

F i gu re 7 .3 Tens i l e s t r eng th r esu l t s f o r conc re te m i xes 7 -4

F i gu re 7 .4 E -va lue t es t r esu l t s f o r conc re te m i xes 7 -5

F i gu re 7 .5 Sh r i nkage and c reep resu l t s f o r i n t e rg round

gas i f i ca t i on ash m ix 7 -7

F i gu re 7 .6 Sh r i nkage and c reep resu l t s f o r i n t e rb l ended f l y

a sh m i x 7 -8


F igu re 7 .7 Sh r i nkage and c reep resu l t s f o r i n t e rb l ended

gas i f i ca t i on ash m ix 7 -8

F i gu re 7 .8 Spec i f i c c reep resu l t s f o r t he t h ree d i f f e ren t m i xes 7 -9

F i gu re 7 .7 Po ros i t y r esu l t s o f conc re te m i xes 7 -10

F igu re 7 .8 Oxygen p e rmeab i l i t y t es t r esu l t s f o r conc re te m i xes 7 -11

F igu re 7 .9 Oxygen p e rmeab i l i t y i ndex resu l t s f o r t he conc re te

m i xes 7 -12


LIST OF TABLES PAGE

Tab le 2 .1 Common Po r t l and and Po r t l and f l y ash cemen ts

( f r om SANS 50197 -1 /SABS EN 197 -1 :20001 ) 2 -4

Tab le 2 .2 Mechan i ca l and Phys i ca l r equ i r emen ts o f cemen t

( f r om SANS 50197 -1 /SABS EN 197 -1 :2000 ) 2 -5

Tab le 3 .1 Typ i ca l chem ica l compos i t i on o f f l y ash (Add i s , 2001 ) 3 -8

Tab le 3 .2 Chem ica l spec i f i ca t i ons fo r cemen t ex tende rs .

(SANS 1491 -2 :2005 / SABS 194 1 -2 :2005 ) 3 -9

Tab le 4 .1 M i x compos i t i on f o r mo r ta r p r i sms 4 -13

Tab le 4 .8 M i x compos i t i on used i n t es t 4 -13

Tab le 4 .3 Mo r ta r p r i sm m ix compos i t i on f o r i n t e rb l end ing cemen t

and Gas i f i ca t i on ash 4 -19

Tab le 4 .2 Mo r ta r p r i sm m ix compos i t i on f o r i n t e rg r i nd i ng cemen t

and Gas i f i ca t i on ash 4 -19

Tab le 4 .5 Gypsu m rep lacemen t we igh t s f o r mo r ta r p r i sms 4 -19

Tab le 5 .1 M i x compos i t i on f o r conc re te m i xes 5 -2

Tab le 5 .2 Conc re te m i x compos i t i on 5 -2

Tab le 6 .1 F i t t ed func t i ons o f ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on 6 -5

Tab le 6 .2 Ros in -Rammle r pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s 6 -6

Tab le 6 .3 Ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s 6 -9

Tab le 6 .4 XRF re su l t s 6 -13

Tab le 6 .5 Chem ica l t es t r esu l t s 6 -15

Tab le 6 .6 S t r eng th c l asses o f i n t e rb l end ing m ixes g r i nd i ng t ime 6 -17

Tab le 6 .7 Pe rcen tage o f compress i ve s t r eng th ach ieved f o r

i n t e rb l end ing 6 -18

Tab le 6 .8 S t r eng th c l asses f o r i n t e rg r i nd i ng m ixes g r i nd i ng t ime 6 -23


i n t e rg r i nd i ng 6 -24

Tab le 6 .10 S t r eng th c l asses f o r d i f f e ren t r ep l acemen t l eve l s o f



Tab le 6 .11 Pe rcen tage o f compress i ve s t r eng th ach ieved f o r d i f f e ren t

r ep l acemen t l eve l s o f gas i f i ca t i on ash 6 -35

Tab le 6 .12 S t r eng th c l asses f o r d i f f e ren t r ep l acemen t l eve l s o f


Tab le 6 .13 Pe rcen tage o f compress i ve s t r eng th ach ieved f o r d i f f e ren t

r ep l acemen t l eve l s o f gas i f i ca t i on ash 6 -40

Tab le 7 .1 Tab le compa r i ng t ens i l e and compress i ve s t r eng ths 7 -4

Tab le 7 .2 E - va lue resu l t s o f t he d i f f e ren t cy l i nde rs f o r t he

d i f f e ren t m i xes 7 -6

Tab le 7 .3 Sh r i nkage , C reep and Spec i f i c C reep Resu l t s f o r t he

d i f f e ren t m i xes 7 -6


1-1

1 . INTRODUCTION 1 .1 BAC KGR OUN D

I n r ecen t yea rs t he re has been a s i gn i f i can t i nc rease i n t he use

o f was te ma te r i a l s as bo th cemen t ex tende rs and f i l l e r s i n

conc re te (Esca lan te , 2004 ) . The reason f o r t h i s i s a g row ing

awa reness o f t he eng inee r i ng , ec onom ica l and ec o log i ca l

bene f i t s , t he use o f was te ma te r i a l s have i n t he cemen t and

conc re te i ndus t r i es . Was te ma te r i a l s can howeve r on l y be used

i n conc re te i f t hey a re no t de t r imen ta l t o t he sho r t - o r t he l ong -

t e rm p rope r t i es o f t he conc re te .

The ma in r eason f o r t he use o f ex te nde rs i n conc re te i s t he i r

va r i e t y o f use fu l enhancemen ts o f o r mod i f i ca t i ons t o t he

conc re te p rope r t i es . Cemen t ex t ende rs have two common

f ea tu res :

• t he i r pa r t i c l e s i ze r ange i s s im i l a r t o o r sma l l e r t han tha t

o f Po r t l and cemen t .

• t hey become i nvo l ved i n t he hyd ra t i on r eac t i ons .

I n b l ended cemen t p roduc t i on , ex tende rs can be i n t r oduced t o

t he cemen t by i n t e rb l end ing o r i n t e rg r i nd i ng (E rdogdu , 1999 ) .

The f eed t o Saso l gas i f i e r s p r i nc i pa l l y cons i s t s o f coa rse coa l

( >5mm) and ex t r aneous rock f r agmen ts ( s t one ) . Du r i ng t he

gas i f i ca t i on o f t h i s coa rse coa l a t e l eva ted t empe ra tu res and

p ressu re a m i x tu re o f ca rbon monox ide and hyd rogen (a l so

r e fe r red t o as syn thes i s gas ) i s p roduced . The coa rse ash i s

f o rmed a t t hese e l eva ted t empe ra tu res and p ressu re by t he

i n t e rac t i on o f i ne r t m ine ra l s p resen t i n t he coa l and s tone . The

coa rse ash i s r emoved f r o m the ga s i f i e r and d i sposed as a by -

p roduc t (Van Dyk , 2005 ) .


1-2

1 .2 OBJE CTI VES OF THE STUDY

The ma in a im o f t h i s i nves t i ga t i on i s t o de te rm ine t he

su i t ab i l i t y o f us i ng gas i f i ca t i on as h as cemen t e x tende r i n

conc re te . To mee t t h i s a im , t he ob jec t i ves o f t he i nves t i ga t i on

a re as f o l l ows :

• To i nves t i ga te t he p rope r t i es o f cemen t ma nu fac tu r i ng w i t h

spec i f i c re f e rence t o cemen t c l asses , hyd ra t i on o f cemen t ,

and t he op t im i sa t i on o f gypsum, spec i f i c su r f ace a rea and

pa r t i c l e s i ze d i s t r i bu t i on , t o eva lua te t he pe r f o rma nce o f

cemen t p roduced i n t he l abo ra to r y .

• I nves t i ga te t he phys i ca l , chemica l and m ine ra l og i ca l

compos i t i on o f a gas i f i ca t i on ash samp le t o de te rm ine i f

gas i f i ca t i on ash can be used as a ceme n t ex ten de r i n

conc re te .

• De te rm in e t he comp l i ance o f gas i f i ca t i on ash w i t h t he

r equ i r emen ts f o r us e i n cemen t .

• De te rm in e an op t imum g r i nd ing t ime f o r bo th t he

i n t e rb l end ing and i n t e rg r i nd i ng o f gas i f i ca t i on ash and

cemen t .

• De te rm in e t he e f fec t o f r ep l acemen t l eve l on t he p rope r t i es

o f i n t e rb l ended and i n t e rg round gas i f i ca t i on as h and cemen t .

• I n ves t i ga te t he e f f ec t o f i n t e rb l ended and i n t e rg round

gas i f i ca t i on ash and cemen t on t he sho r t and l ong t e rm

p rope r t i es o f conc re te .

• I n ves t i ga te t he e f f ec t o f t he gas i f i ca t i on ash on t he

du rab i l i t y o f conc re te .

1 .3 SCOPE OF THE ST UDY

Th i s s tudy w i l l cons i s t o f a l i t e ra tu re r ev i ew on t he manu fac tu re

and p rope r t i es o f cemen t . De ta i l o f d i f f e ren t coa l ash by -

p roduc t s i s d i s cussed and t he use o f f l y a sh as a cemen t

ex tende r i n conc re te i s cons ide red . Cons ide ra t i on i s g i ven t o

p rope r t i es l i ke m ine ra l og i ca l and chem ica l compos i t i on , shape ,


1-3

pa r t i c l e s i ze d i s t r i bu t i ons , chem ica l r equ i r emen ts o f us i ng f l y

ash i n conc re te , s t r eng th deve lopmen t a nd du rab i l i t y o f

conc re te .

A gas i f i ca t i on ash samp le i s t es ted to de te rm ine how th i s was te

ma te r i a l compa res t o t he ex tende rs cu r ren t l y used i n t he

cemen t i ndus t r y . Cons ide ra t i on i s g i ven t o t he chem ica l and

phys i ca l p rope r t i es o f gas i f i ca t i on as h . A l l da ta i s ana l ysed t o

ach ieve conc lus i ons on t he above -me n t i oned ob jec t i ves .

Cemen t i s manu fac tu red by g r i nd i ng c l i nke r . Pa r t i c l e s i ze

d i s t r i bu t i ons a re i nves t i ga ted and op t imum g r i nd i ng t imes i s

i nves t i ga ted . The op t im i sa t i on o f gypsum i s a l so i nves t i ga ted

w i t h r e fe rence t o t he hyd ra t i on o f cemen t . D i f f e ren t

r ep l acemen t l eve l s o f gas i f i ca t i on ash a re i nves t i ga ted t o

de te rm ine res t r i c t i on on t he use o f gas i f i ca t i on ash i n cemen t .

Gas i f i ca t i on ash i s used i n conc re te and t he s t r eng th

deve lopmen t , de fo rma t i on and du rab i l i t y o f t hese conc re te

m i xes a re exam in ed . Th i s w i l l p rov i de adequa te unde rs tand ing

o f t he advan tages t ha t was te ma te r i a l s have t o bo th t he cemen t

i ndus t r y and t he env i r onme n t .

To accu ra te l y es t ima te and p red i c t behav iou r , i t i s necessa ry t o

r epea t t es t s on as many i n dependen t samp les as poss ib l e . I n

t h i s s t udy t he t es t s we re o n l y conduc ted once . The re fo re i t i s

no t s t a t i s t i ca l l y co r rec t t o d raw f i na l conc lus i ons and p red i c t

t r ends based on t he r esu l t s .

Th i s s t udy does no t i n c l ude t he f o l l ow ing :

• The e f f ec t o f va r i ab i l i t y o f gas i f i ca t i on ash as f a r as

phys i ca l and chem ica l p rope r t i es i s conce rned .

• The response o f gas i f i ca t i on ash t o adm ix tu res .

• The e f f ec t o f gas i f i ca t i on as h on t he l ong - t e rm du rab i l i t y

o f conc re te .

• Du rab i l i t y t es t s pe r f o rmed exc l udes t he dama g ing e f f ec t s

o f u l t r a v i o l e t (UV) l i gh t and phys i ca l s cou r i ng .


1-4

1 .4 METHODOLOGY

The re we re seven p r i nc i pa l ob j ec t i ves i n t h i s r esea rch p ro j ec t .

The me t hodo logy f o l l owed i n each i s se l ec ted t o ob jec t i ve l y

eva lua te gas i f i ca t i on ash f o r i t s use i n cemen t and conc re te .

• The phys i ca l p rope r t i es o f a gas i f i ca t i on ash samp le w i l l

be i nves t i ga ted by exam in i ng t he pa r t i c l e s i ze d i s t r i bu t i on

and shape . Th i s i nc l udes de te rm in i ng an op t imu m

g r i nd i ng t ime and gypsum con ten t .

• The chemica l and m ine ra l og i ca l compos i t i on o f a

gas i f i ca t i on ash samp le i s i nves t i ga ted and compa red t o

t ha t o f ex tende rs commo n l y used t ha t a re known t o

enhance t he p rope r t i es o f conc re te .

• The comp l i ance o f a gas i f i ca t i on ash w i t h t he chem ica l

r equ i r emen ts f o r us e i n conc re te i s de te rm ined .

• The reac t i v i t y o f gas i f i ca t i on ash i s es tab l i shed by

cons ide r i ng i n t e rb l end ing and i n t e rg r i nd i ng i n mo r ta r , and

t es t i ng aga ins t f l y ash i n conc re te .

• The e f f ec t o f gas i f i ca t i on as h on t he sho r t and l ong t e rm

p rope r t i es o f conc re te i s es tab l i shed by measu r i ng

wo rkab i l i t y , s t r eng th deve lopmen t , e l as t i c i t y , sh r i nkage

and c reep , po ros i t y and pe rmeab i l i t y .

• I n conc lus i on recommenda t i ons a re made f o r t he use o f

gas i f i ca t i on ash .

1 .5 ORGANI SAT ION OF THE REPORT

The d i sse r t a t i on has been d i v i ded i n t o t he f o l l ow ing sec t i ons :

• Chap te r 1 se r ves as an i n t roduc t i on t o t he t hes i s .

• Po r t l and cemen t as we l l as p rope r t i es o f manu fac tu r i ng o f

cemen t i s d i s cussed i n chap te r 2 .

• The compos i t i on and p rope r t i es o f coa l ash a re d i scussed i n

Chap te r 3 , w i t h spec ia l r e fe rence t o t he p rope r t i es o f f l y ash .


1-5

• Chap te r 4 desc r i bes t he expe r imen ta l p rog ramme an d t es t

p rocedu res f o r cemen t .

• Expe r ime n ta l p rog ramme a nd t es t p rocedu res f o r conc re te

a re d i scussed i n Chap te r 5 .

• Chap te r 6 con ta i ns t he r esu l t s f o r t he p rope r t i es and

u t i l i sa t i on o f gas i f i ca t i on as h as a r ep l acemen t o f cemen t i n

mo r ta r p r i sms .

• The resu l t s o f us i ng gas i f i ca t i on ash as a cemen t ex tende r

i n conc re te a re eva lua ted i n Chap te r 7 .

• Chap te r 8 con ta i ns t he conc lus i ons and recommenda t i ons o f

t he s t udy .

• A l i s t o f re f e rences f o l l ows i n Chap te r 9 .

• Va r i ous r esu l t s a re p rov i ded i n t he append i ces . These

append i ces a re r e fe r red t o i n t he ma i n body o f t he

d i sse r t a t i on .


2-1

2. COMPONENTS AND PROPERTIES OF PORTLAND CEMENT

2 .1 INTRODUCTION

Globa l popu la t i on i s r i s i ng , p l ac i ng i nc reas ing p ressu re on

essen t i a l na tu ra l r esou rces such as l and and ene rgy . Th i s

makes i t impe ra t i ve f o r us t o f i nd ways o f us i ng t hese

resou rces mo re e f f i c i en t l y . Th i s need f o r mo re env i r onmen ta l l y

and soc ia l l y sus ta i nab le deve lopmen t has become a key

agenda f o r gove rnmen ts , non -gove rnmen ta l o rgan i sa t i ons

(NGO) an d bus inesses .

Cemen t i s an essen t i a l ma te r i a l i n t oday ' s soc i e t y because , as

a ma jo r cons t i t uen t o f conc re te , i t f o rms a f undamen ta l e l emen t

o f any hous ing o r i n f r as t ruc tu re deve lopme n t . The chem ica l

p rocess o f mak ing cemen t c l i nke r p roduces CO 2 , a ma jo r

g reenhouse gas con t r i bu t i ng t o c l ima te change .

I n t h i s chap te r , de ta i l o f t he manu fa c tu r i ng o f Po r t l and cemen t

(PC) , cemen t c l asses and t he hyd ra t i on o f cemen t w i l l be

d i scussed . Cons ide ra t i on w i l l be g i ven t o p rope r t i es l i ke t he

op t im i sa t i on o f su l pha te and f i neness o f cemen t . The pa r t i c l e

s i ze d i s t r i bu t i on i s d i s cussed w i t h spec i f i c r e f e rence t o t he

Ros in -Rammle r d i s t r i bu t i on f unc t i on . Th i s w i l l p rov i de adequa te

unde rs tand ing o f t he p rope r t i es o f cemen t and t he i n f l uence

b l ended cemen ts have on t he cemen t hyd ra t i on p rocess .

2 .2 CEMENT MAN UFA CTURE

SANS 50 197 -1 /SABS EN 1 97 -1 :2000 s ta tes t ha t “ cemen t i s a

hyd rau l i c b i nde r , a f i ne l y g round i no rgan i c ma te r i a l wh i ch ,

when m ixed w i t h wa te r , f o rms a pas te wh i ch se t s and ha rdens

by means o f hyd ra t i on r eac t i ons and p rocesses and wh i ch a f t e r

ha rden ing , r e ta i ns i t s s t r eng th and s tab i l i t y even unde r wa te r . ”


2-2

Cemen t i s manu fac tu red f rom fou r r aw ma te r i a l ox i des : l ime ,

s i l i ca , a lum ina and f e r r i c ox i de . L ime canno t be f ound i n na tu re

and i s p roduced by hea t i ng ca l c i um ca rbona te (Add i s , 2001 ) .

Cemen t manu fac tu r i ng cons i s t s o f qua r r y i ng o r excava t i ng r aw

ma te r i a l s . Cemen t manu fa c tu re r s ob ta i n s i l i ca , a l um ina and

f e r r i c ox i des f r om c l ay o r sha le . The raw ma t e r i a l s a re c rushed ,

b l ended , m i l l ed and p rehea ted i n a k i l n . I n t he k i l n , ca l c i um

ca rbona te i s conve r t ed t o ca l c i um ox ide a t t empe ra tu res o f

800°C t o 1000°C :

CaCO 3 → CaO + CO 2 ( equa t i on 2 .1 )

The ma te r i a l s f l ow t o a ho t te r ( 1450°C) pa r t o f t he k i l n whe re ,

t he b l end o f t he f ou r ox i des i s conve r t ed t o cemen t c l i n ke r

(Add i s , 2001 ) . The c l i nke r i s t hen g round w i t h a sma l l amoun t

o f gypsum i n to a powde r w i t h a spec i f i c su r face a rea (B la i ne )

o f 300 – 350 m² / k g t o ma ke ‘O rd ina ry Po r t l and Cemen t ’ , t he

mos t common l y used t ype o f cemen t ( o f t en re fe r red t o as

OPC) . A schema t i c p resen ta t i on o f t he cemen t manu f ac tu r i ng

p rocess can be seen i n F i gu re 2 .1 .

The CO 2 em iss i ons f r om Po r t l and cemen t manu fac tu r i ng a re

gene ra ted by two mechan i sms . These mechan i sms a re t he

ca l c i n i ng o f l imes tone ( see equa t i on 2 .1 ) and t he comb us t i on o f

f ue l s t o gene ra te ene rgy . Typ i ca l l y , Po r t l and cemen t con ta i ns

t he equ i va l en t o f abou t 63 .5 % CaO. Consequen t l y , abou t 1 .135

un i t s o f CaCO 3 a re r equ i r ed t o p roduce 1 un i t o f cemen t , and

t he amoun t o f CO 2 r e l eased i n t he ca l c i n i ng p rocess i s abou t

500 k i l og rams ( kg ) pe r me t r i c t on o f Po r t l and cemen t p roduced

(1 ,000 pounds [ l b ] pe r t on o f cemen t ) . To ta l CO 2 em iss i ons

depend on ene rgy consump t i on and gene ra l l y f a l l i n t he r ange

o f 0 . 85 to 1 .35 me t r i c t on o f CO 2 pe r me t r i c t on o f c l i n ke r

(www. wb csdcemen t . o rg , 2005 ) . Th i s means t ha t t he cemen t

i ndus t r y p roduces 5% o f g l oba l man -made CO 2 e m iss i ons , o f

wh i ch 50% i s f r om the chemica l p rocess , and 40% f r om bu rn i ng

f ue l . The rema inde r i s sp l i t be tween e l ec t r i c i t y and t r anspo r t

us es . C l ima te p ro tec t i on , and i n pa r t i c u l a r r educ t i on o f c a rbon



2-3

d iox i de (CO 2 ) e m iss i ons i s t he re fo re an i s sue wh i ch ve r y

se r i ous l y needs t o be add ressed by t he cemen t i ndus t r y .

F i gu re 2 .1 Cemen t manu fac tu re and t he i n f l uenced aspec t s

( f r om ww w.wbcsdcemen t . o rg , 2005 )

Because c l ima te p ro tec t i on has such a h i gh p ro f i l e i n t he

i ndus t r y , e f f ec t i ve s t r a teg ies f o r manag ing CO 2 e m iss i ons a re

o f c ruc i a l impo r t ance i n t he ma rke tp l ace . The reduc t i on

op t i ons a re l i ke l y t o i nc l ude : i nnova t i on i n imp rov ing t he

ene rgy e f f i c i ency o f p rocesses and equ ipmen t ; sw i t ch i ng to

l owe r ca rbon f ue l s ; us i ng a l t e rna t i ve r aw ma t e r i a l s t o r educe

l imes tone use ; deve lop ing CO 2 cap tu re and seques t ra t i on

t echn iques ; and t ak i ng advan tage o f ma rke t mechan i sms such

as em iss i ons t r ad ing and vo lun ta r y i n i t i a t i ves .

The use o f was te ma te r i a l s dec rease t he amoun t o f c l i n ke r

manu fac tu red and t hus dec reases t he amoun t o f CO 2

em iss i ons .



2-4

2 .3 CEMENT CLASSES

Tab le 2 .1 i nd i ca tes t he mo s t commo n Po r t l and and Po r t l and f l y

ash cemen t used i n Sou th A f r i ca . Tab le 2 .2 i nd i ca tes t he

mechan i ca l and phys i ca l r equ i r emen ts o f cemen t used i n Sou th

A f r i ca . These t ab l es a re used t o desc r i be t he commerc i a l l y

ava i l ab l e cemen t . The c l ass i f i ca t i on o f cemen ts i n t e rms o f

t he i r s t r eng th -g i v i ng p rope r t i es has been p rac t i sed fo r many

yea rs .

Tab le 2 .1 Common Po r t l and and Po r t l and f l y as h cemen ts ( f r om SANS

50197 -1 /SABS EN 197 -1 :2000 )

Composition (percentage by mass)

Main constituents

Pozzolana Fly ash

clinker natural natural

calcined siliceous calcer

ous

Minor additio

nal constituents Main

types Notation of the

products K P Q V W

CEM I Portland cement CEM I 95-100 - - - - 0-5

CEM II/A-V 80-94 - - 6-20 - 0-5

CEM II/B-V 65-79 - - 21-35 - 0-5

CEM II/A-W 80-94 - - - 6-20 0-5

CEM II

Portland fly ash cement CEM II/B-W 65-79 - - - 21-35 0-5


2-5

Tab le 2 .2 Mechan i ca l and Phys i ca l requ i r emen ts o f cemen t ( f r om SANS

50197 -1 /SABS EN 197 -1 :2000 )

Compressive strength MPa

Early Strength Standard Strength Strength

Class 2 Days 7 Days 28 Days

Initial setting

time

Soundness (expansion)

mm

32.5 N - ≥16.0

32.5 R ≥ 10.0 - ≥ 32.5 ≤ 52.5 ≥ 75

42.5 N ≥ 10.0 -

42.5 R ≥ 20.0 - ≥ 42.5 ≤ 62.5 ≥ 60

52.5 N ≥ 20.0 -

52.5 R ≥ 30.0 - ≥ 52.5 - ≥ 45 ≤ 10

2 . 4 HYDR ATI ON OF P ORTLA N D CE MEN T

The se t t i ng and ha rden ing o f Po r t l and cemen t occu r as a r esu l t

o f t he r e ac t i on be tween t h e compo unds o f cemen t a nd wa te r .

The ma jo r compounds o f cemen t t ha t r eac t w i t h wa te r t o

p roduce reac t i on p roduc t s a re t r i ca l c i um s i l i ca te (C 3 S ) ,

d i ca l c i um s i l i ca te (C 2 S ) , t r i ca l c i um a lum ina te (C 3 A ) , and

t e t r aca l c i um a lum i no fe r r i t e (C 4 AF ) (Nev i l l e , 1995 ) .

The p resence o f gypsum a f f ec t s t he hyd ra t i on pa t te rn o f PC

bo th k i ne t i ca l l y and t he rmo dynam ica l l y . F i r s t l y t he i n f l uence o f

gypsum on t he p r i nc i pa l i nd i v i dua l cons t i t uen t s i s d i s cussed

and t hen t he i n f l uence o f t he r eac t i ons as a who le wh i ch occu r

w i t h PC hyd ra t i on .

2 .4 .1 The h ydra t ion o f C 3 S and C 2 S

The ha rden ing o f cemen t pas te i s due ma in l y t o t he f o rma t i on

o f Ca l c i um s i l i ca te hyd ra te (CSH) , and t h i s f o rma t i on i s

a f f ec ted by t he p resence o f CaSO 4 i n t he pas te . The g ypsum i n

cemen t no t on l y a f f ec t s t he se t t i ng t ime , bu t a l so t he s t r eng th

deve lopmen t . The op t imum gypsu m con ten t i s t he va lue a t

wh i ch t he op t imum comb ina t i on o f quan t i t y and qua l i t y occu rs .


2-6

Loche r e t a l ( 1995 ) , have d i scussed f ac to r s gove rn i ng t he

op t imum gypsum con ten t and t he e f fec t s o f va r y i ng t he sou rce

o f t he su l pha te . The s i t ua t i on i s comp l i ca ted by t he f ac t t ha t ,

con t ra r y t o some ea r l y c onc lus i ons , t he amoun ts n eeded t o

op t im i se d i f f e ren t p rope r t i es , such as s t r eng th a t va r i ous ages

and d r y i ng sh r i nkage a re no t necessa r i l y t he same ; a l so , t he

amoun t needed t o op t im i se a g i ven p rope r t y i n a conc re te may

no t be t he same as t ha t requ i r ed i n a pas te o r mo r ta r (Tang

and Ga r tne r , 1988 ) .

Du r i ng t he ea r l y and m idd le pe r i ods o f r eac t i on i n a cemen t

pas te , gypsum d i sso l ve and reac t a t o r c l ose to t he su r f aces o f

t he c l i nke r g ra i ns , mo re spec i f i ca l l y t he a l um ina te and f e r r i t e

phases . The f ac to r mos t d i r ec t l y i n f l uenc ing t he cou rse o f t he

ea r l y r eac t i ons i s no t so much t he re l a t i ve amoun ts o f ca l c i um

su lpha te , a l um ina te and f e r r i t e phases , as t he r a te a t wh i ch t he

re l evan t i on i c spec ies a re made ava i l ab l e a t t he su r f ace o f t he

cemen t g ra i ns . O the r ma jo r f ac to r s a f f ec t i ng t he supp l y o f

t hese i ons a re the pa r t i c l e s i ze d i s t r i bu t i on o f t he ca l c i um

su lpha te and t he d i s t r i bu t i on i n space o f t he pa r t i c l es (Tay lo r ,

1995 ) . F r i g i one (1995 ) has , by mea s u r i ng the Ca 2 +

concen t ra t i on o f t he l i qu i d phase shown t ha t t he p resence o f

gypsum i nc reased t he C 3 S hyd ra t i on r a te , F i gu re 2 .2 .

The ca l c i um s i l i ca te hyd ra te r eac t i ons a re t he mos t i mpo r t an t

as t hese a re r espons ib l e f o r t he ma jo r i t y o f s t r eng th o f t he

ha rdened cemen t pas te ( hcp ) . The hyd ra t i o n p roduc t s o f t he

two ca l c i um s i l i ca tes a re s im i l a r and d i f f e r on l y i n t he t e rms o f

t he r a te a t wh i ch t hey oc cu r and i n t he amoun t o f ca l c i um

hyd rox i de f o rmed as seen i n equa t i on 2 .3 and 2 .4 . The reac t i on

o f t he C 3 S w i t h wa te r i s t he mo re rap id o f t he two .

2C 3 S + 6H → C 3 S 2 H 3 + 3CH ( equa t i on 2 .3 )

Al i te


2-7

F i gu re 2 .2 Changes i n Ca 2 + i n so l u t i on cu r i ng C 3 S hyd ra t i on vs .

t ime i n t he absence and p resence o f gypsum (F r i g i one , 1995 )

The C 2 S reac t i on i s s im i l a r , bu t i t t a kes p l ace a t a s l owe r r a te ,

con t r i bu tes l ess hea t t han t he C 3 S and i s r espons ib l e f o r t he

l a t e r s t r eng th deve lopmen t .

2C 2 S + 4H → C 3 S 2 H 3 + CH ( equa t i on 2 .4 )

Bel i t e

When wa te r i s added t o t he r eac t i ons above , t he ca l c i um

hyd rox i de i ons a re r ap id l y r e l eased i n t o t he so l u t i on and t he

pH o f t he so l u t i on r i ses r ap id l y t o ove r 12 . Du r i ng t h i s s t age a

cons ide rab le amoun t o f hea t i s evo l ved .

Wh i l e t he concen t ra t i on o f ca l c i um and hyd rox i de i ons a re

bu i l d i ng up , a do rman t pe r i od occu rs wh i ch co i nc i des w i t h t he

e t t r i ng i t e de lay f r o m the C 3 A reac t i on and he lps t o exp la i n why

pas te can rema in wo rkab le f o r so l ong . Once t he c r i t i ca l

concen t ra t i on o f t he i ons i s r eached t he CSH and CH s ta r t t o


2-8

c r ys ta l l i se ou t f r om the so l u t i on , s t r eng th i s deve loped and

wo rkab i l i t y i s l o s t .

2 .4 .2 Hyd ra t io n o f C 3 A

The reac t i on o f C 3 A w i t h wa te r i s ve r y f as t and i nvo l ves

r eac t i ons w i t h su l pha te i ons supp l i ed by t he d i sso lu t i on o f

gypsum ( see Equa t i ons 2 .5 and 2 .6 ) .

C 3 A + 3CSH 2 + 26H → C 3 A .3CS H 3 2 ( equa t i on 2 .5 )

Whe re :

H - Wa te r

CSH - Ca l c i um su lpha te (Gypsu m)

C 3 A .3CS H 3 2 - Ca l c i um Su lpha te A lum ina te Hyd ra te (E t t r i ng i t e )

The f o rma t i on o f e t t r i ng i t e s l ows down t he hyd ra t i on o f C 3 A by

c rea t i ng a ba r r i e r a round t he cemen t g ra i ns . A f t e r a ce r t a i n

po r t i on o f t he su l pha te has been consumed , t he e t t r i ng i t e

becomes uns tab le and a second reac t i on beg ins t o t ake p l ace

(Wa inwr i gh t , 2004 ) .

E t t r ing i t e

C 3 A + CSH + 10 H → C 3 A .CS H 1 2 ( equa t i on 2 .6 )

Mo nosu l pha te

I t i s no t un t i l t h i s second reac t i on occu rs t ha t t he pas te beg ins

t o s t i f f en s i gn i f i can t l y and wo rkab i l i t y beg ins t o d rop . The

ove ra l l C 3 A reac t i on p roduces a s i gn i f i can t quan t i t y o f hea t bu t

con t r i bu te l i t t l e t o t he s t r eng th .

An i nadequa te supp l y o f so l ub le ca l c i um su lpha te can resu l t i n

a r ap i d l oss o f wo rkab i l i t y known as f l a sh se t . Th i s i s

accompan ied by t he r e l ease o f hea t and i s i r r eve rs i b l e .

Howeve r , i f t oo h i gh a l eve l o f gyps um i s p resen t ; c r ys ta l s o f

gypsum c r ys ta l l i ze f r om the so l u t i on and cause a p l as te r o r

f a l se se t ( cemen t ) . I f m i x i ng con t i nues o r i s r esumed , t he i n i t i a l

l e ve l o r wo rkab i l i t y i s r es to red . The cemen t manu fac tu re r t hus


2-9

needs t o op t im i ze t he l eve l o f gypsum i n t he cemen t and ma tch

t h i s t o t he reac t i v i t y o f C 3 A p resen t . Th i s conc ep t i s i l l u s t r a t ed

i n F i gu re 2 .3 .

F i gu re 2 .3 Op t im i za t i on o f so l ub le ca l c i um su lpha te ( c emen ts )

(Newman , 2003 )

2 .4 .3 Hyd ra t io n o f C 4 A F

The f e r r i t e phase (C 4 AF) i s o f no g rea t impo r t ance compa red t o

t he o the rs . I t i s a s l ow reac t i on ( see equa t i on 2 .7 ) w i t h l i t t l e

hea t evo l ved and con t r i bu tes l i t t l e t o t he s t r eng th .

C 4 AF + 10H + 2CH → C 6 AFH 1 2 ( equa t i on 2 .7 )

Sulphofe r r i t e

2 .5 HEAT OF HYDR AT ION

The chem ica l r eac t i ons be tween unhyd ra ted cemen t and wa te r

du r i ng se t t i ng and ha rden ing re l ease hea t wh i ch r esu l t s i n a

r i se i n t empe ra tu re o f t he f r esh conc re te . I f op t imum

pe r f o rma nce i s t o be ach ieved f r o m the cemen t , i t i s t hough t

t ha t t he peak hyd ra t i on r a te assoc ia ted w i t h C 3 A shou ld be


2-10

de layed by SO 3 add i t i ons un t i l t he s i l i ca te hyd ra t i on r a te has

passed i t s peak .

2 . 5 .1 Opt im iza t ion o f Cement Su lpha te

Nev i l l e , ( 1995 ) sugges ted tha t t he op t imum g ypsum co n ten t be

de te rm ined by o bse rva t i on o f t h e gene ra t i on o f hea t o f

hyd ra t i on . Op t imum su lpha te w i t h r espec t t o s t r eng th

deve lopmen t and d imens iona l s t ab i l i t y occu r red when t he

dep le t i on o f so l ub le su l pha te used up by t he a l um ina te

hyd ra t i on occu r red a t a t ime l a t e r t han t he ma x imum hea t

evo lu t i on f r om th e ma in s i l i ca te hyd ra t i on peak (Sandbe rg ,

2004 ) . F i gu re 2 .4 shows an examp le o f hyd ra t i ng PC w i t h

s l i gh t l y h i ghe r t han op t imum su lpha te con ten t mon i t o red a t

r oom tempe ra tu re by an i so the rma l conduc t i on ca l o r ime te r .

The i n i t i a l peak i n F i gu re 2 .4 occu rs as soon as wa te r i s added

t o t he PC , r esu l t i ng f r om the e t t r i ng i t e be ing fo rmed i n t he C 3 A

reac t i on . The ca l c i um hyd rox ide i ons pass ing i n t o so l u t i on i n

t he cemen t m i xed w i t h wa te r i n i t i a l l y d i sp l ay s t r ong exo the rm ic

behav iou r by r ap id d i sso lu t i on and i n i t i a l hyd ra t i on o f ma in l y

t he a l um ina te phase as seen a t A i n F i gu re 2 .4 . I f s u f f i c i en t

su l f a t e i s ava i l ab l e i n t he so l u t i on , t he hyd ra t i on r a te r ap id l y

dec reases as t he a l um ina te r eac t s w i t h ca l c i um and su l f a t e t o

f o rm e t t r i ng i t e (B on t he cu r ve ) . The f o rma t i on o f e t t r i ng i t e

p reven t s f l a sh se t and a l l ows t he c onc re te t o be t r a nspo r t ed

and p l aced wh i l e i t i s s t i l l f l u i d . A f t e r some t ime t he s t r eng th

g i v i ng A l i t e hyd ra t i on t akes o f f , wh i ch r esu l t s i n a b road

exo the rm C . Se t usua l l y occu rs a t t he i n i t i a l pa r t o f t he A l i t e

exo the rm . The A l i t e and a l um ina te hyd ra t i on con t i nue i n

pa ra l l e l un t i l t he m i x tu re r uns ou t o f so l ub le su l pha te ( a t D ) ,

wh i ch i n i t i a t es t he f o rma t i on o f a l um ina tes w i t h l ess su l f a t e

t han e t t r i ng i t e (Sandbe rg , 2004 ) .


2-11

F igu re 2 .4 Exa mp le o f no rma l hyd ra t i on o f Po r t l and cemen t

(Sandbe rg , 2004 )

A f t e r t he wa te r ha s been added t o t he cemen t t he f i r s t peak i n

t he r a te o f hea t evo lu t i on i s f o l l owed by a second peak some 4

t o 10 hou rs l a t e r . W i t h t he co r rec t amoun t o f gypsum the re

shou ld be l i t t l e C 3 A ava i l ab l e f o r r eac t i on a f te r a l l t he gypsum

has comb ined and no f u r t he r peak i n t he hea t l i be ra t i on shou ld

occu r . Thus op t imum gypsu m con ten t l eads to a des i rab le r a te

o f ea r l y r eac t i on and p reven t s l oca l h i gh concen t ra t i on o f

p roduc t s o f hyd ra t i on (Nev i l l e , 1995 ) . I n consequence t he s i ze

o f po res i n hyd ra ted cemen t pas te i s r educed and s t r eng th i s

i n c reased . The amoun t o f g ypsum re qu i r ed i nc reases w i t h t he

C 3 A con ten t and a l so w i t h t he a l ka l i con ten t o f t he cemen t .

I nc reas ing t he f i neness o f cemen t has t he e f f ec t o f i nc reas ing

t he quan t i t y o f C 3 A ava i l ab l e a t ea r l y s t ages , and t h i s r a i ses

t he gypsum requ i r emen t .

The amoun t o f gypsum added t o cemen t c l i nke r i s exp ressed as

t he mass o f SO 3 p resen t ; t h i s i s l im i t ed by t he SANS 50197 -

1 /SABS EN 197 -1 :2000 t o a ma x imu m o f 3 .5 %. The re i s usua l l y

f ound t o be an op t imum SO 3 con ten t ( 2 -3% fo r b i nde rs ) , beyond

wh i ch (> 4%) , compress i ve s t r eng th beg ins t o dec l i ne ( Lea ,

1998 ) . F r i g i one con f i rmed t h i s s t a temen t us i ng ISO-R ILEM

mor ta r p r i sms , f o r cemen ts w i t h a w ide range o f pa r t i c l e s i ze


2-12

d i s t r i bu t i ons , gypsum was added t o p reg round c l i nke r , and

f ound t ha t t he max i mum i n s t r eng th was no t sens i t i ve t o

pa r t i c l e s i ze g rad ing (F r i g i one and Mara , 1976 ) . Le r ch ’ s ,

( 1946 ) t es t r esu l t s i nd i ca te t ha t 2 . 5% added SO 3 may be

su f f i c i en t t o b r i ng t he r esu l t i ng PC to op t imum SO 3 l eve l .

2 .6 SPECIF I C SURF ACE AREA

At mos t manu fac tu r i ng p l an t s a ba l l m i l l i s used t o g r i nd t he

cemen t c l i n ke r . The p r i nc i pa l t es t ca r r i ed ou t a t a cemen t m i l l

i s t he f i neness tes t i n wh i ch t he spec i f i c su r f ace a rea i s

de te rm ined . The spec i f i c g rav i t y and f i neness o f ceme n t

i nc rease w i t h an i nc rease i n t he g r i nd i ng t ime . Bouzoubaâ e t a l

( 1997 ) f ound t ha t t h i s i nc rease i n f i neness was l ess s i gn i f i can t

beyond 2 hou rs . An op t imum o f 4 hou rs g r i nd i ng t ime was

es tab l i shed by Bo uzoubaâ , beyond wh i ch t he wa te r r e qu i r emen t

i nc reased and t he s t r eng th e i t he r dec reased o r d i d no t i n c rease

s i gn i f i can t l y .

The f i neness o f cemen t i s a ma jo r f ac to r i n f l uenc ing i t s r a t e o f

hyd ra t i on , s i nce the hyd ra t i on r eac t i on occu rs a t t he i n t e r f ace

w i t h wa te r ( Lea , 1988 ) . G re a te r cemen t f i neness i nc reases t he

ra te a t wh i ch cemen t hyd ra tes and t hus acce le ra tes s t r eng th

deve lopmen t . The e f f ec t s o f g rea te r f i neness on pas te s t r eng th

a re man i f es ted p r i nc i pa l l y du r i ng t he f i r s t seven days .

Po r t l and cemen t i s usua l l y g round t o a su r face a rea i n t he

r ange 300 – 350 m 2 / kg and rap id ha rden ing Po r t l and cemen t t o

400 – 550 m 2 / kg .

2 .7 PARTICL E S IZE D ISTRIBUT ION

The pa r t i c l e s i ze d i s t r i bu t i on cu r ve o f a ma te r i a l desc r i bes two

p rope r t i es o f t he ma te r i a l name l y mean pa r t i c l e s i ze as we l l as

t he d i s t r i bu t i on o f o t he r s i zes abou t t he mean . The cu rve i s

usua l l y d rawn as t he cumu la t i ve pe rcen tage -va lues on t he y -

ax i s o f pa r t i c l es sma l l e r t han t he co r respond ing s i zes on t he x -


2-13

ax i s . The x -ax i s i s d rawn to a l og sca le t o accommod a te l a rge

ranges o f pa r t i c l e s i zes . The shape o f t he cu r ve g i ves an

i nd i ca t i on o f t he con t i nu i t y i n s i ze d i s t r i bu t i on and t he s l ope

desc r i bes t he w ideness o r range o f t he s i ze d i s t r i bu t i on .

Pa r t i c l e s i ze d i s t r i bu t i ons o f i n t e rg round b l ended cemen ts a re

d i f f e ren t t han t ha t o f sepa ra te l y g round cemen ts (E rdogdu ,

1999 ) . The pa r t i c l e s i ze d i s t r i bu t i on p roduced when a ma te r i a l

i s g round becomes w ide r as t he ma te r i a l becomes eas ie r t o

g r i nd . Du r i ng t he i n t e rg r i nd i ng o f cemen t cons t i t uen t s o f

d i f f e r i ng g r i ndab i l i t y , t he pa r t i c l e s i ze d i s t r i bu t i on o f t he

ma te r i a l wh i ch i s ha rde r t o g r i nd becomes na r rowe r , t he eas ie r

t he o the r componen t i s t o g r i nd . Conve rse l y , t he pa r t i c l e s i ze

d i s t r i bu t i on o f t he ma te r i a l wh i ch i s eas i e r t o g r i nd becomes

w ide r t he ha rde r t he o the r componen t i s t o g r i nd ( Lea , 1988 ) .

App rox ima te l y 95% o f cemen t pa r t i c l es a re sma l l e r t han 45µm,

w i t h t he ave rage pa r t i c l e a round 15µm. Bye , ( 1999 ) suppo r t ed

t he gene ra l l y he ld v i ew t ha t t he 3 -30µm f r ac t i on makes a ma jo r

con t r i bu t i on t o t he 28 -day s t r eng th . The range <3µm i s

impo r tan t f o r ach iev i ng h i gh 1 -day s t r eng ths .

2 .7 .1 Ros in -Ra mmler d is t r ibu t ion func t ion

I n sea rch ing f o r a pa rame te r , wh i ch w i l l p rov i de a mo re

r ep resen ta t i ve desc r i p t i on o f t he pa r t i c l e s i ze d i s t r i bu t i on , t h e

Ros in -Rammle r f u nc t i on was i nves t i ga ted .

F rom a p robab i l i t y po in t o f v i ew Ros in and Rammle r

i nves t i ga ted t he pa r t i c l e s i ze d i s t r i bu t i on o f c rushed coa l and

deve loped a f unc t i on t ha t desc r i bes t he d i s t r i bu t i on as (Ros in ,

1933 ) :

ƒ ( x ) = exp ( -bx n ) ( equa t i on 2 .8 )

Whe re :


2-14

b - F i neness cha rac te r i s t i c measu re o f t h e ma te r i a l be i ng

ana l ysed .

n - A mea s u re o f t he r ange o f pa r t i c l e s i zes .

Ros in and Rammle r a l so found t ha t t he f unc t i on does no t on l y

app l y t o c rushed coa l bu t a l so t o va r i ous o the r powered

ma te r i a l s .

The f unc t i on was mod i f i ed as f o l l ows :

RR = exp – (x /X o ) n ( equa t i on 2 .9 )

Whe re :

The we igh t i ng f unc t i on ƒ ( x ) i s deno ted as RR .

X o – t he abso lu te s i ze cons tan t o r pos i t i on pa rame te r ( i t

r ep resen ts t he pa r t i c l e s i ze f o r wh i ch 36 .8% o f t he pa r t i c l es

a re coa rse r ) .

Tak ing t he doub le l oga r i t hm o f equa t i on 2 .9 we ob ta i n :

l n l n (1 /RR) = n ( l nx - l nX o ) ( equa t i on 2 .10 )

Equa t i on 2 .10 desc r i bes a s t r a i gh t l i ne p l o t w i t h a coo rd i na te

sys tem made up o f a l og sca le absc i ssa f o r t he pa r t i c l e s i ze x ,

and an o rd i na te w i t h a doub le l oga r i t hm o f t he r ec i p roca l o f t he

r es i due RR. The s l ope o f t he s t r a i gh t l i ne i s n and t he l i ne

i n t e r cep t t he ho r i zon ta l ax i s a t a va l ue desc r i b i ng t he pa r t i c l e

s i ze x (O lo runsogo , 1990 ) . A h y po the t i ca l examp l e o f t he

d i ag rammat i c r ep resen ta t i on o f t he pa r t i c l e s i ze d i s t r i bu t i on by

t he Ros in -Rammle r d i s t r i bu t i on f unc t i on i s shown i n F i gu re 2 .5 .


2-15

F igu re 2 .5 D iag rammat i c r ep resen ta t i on o f Ros in -Ramle r

d i s t r i bu t i on f unc t i on (Wa inwr i gh t and O lo runsogo , 1999 )

F i gu re 2 .5 ( a ) shows t he t yp i ca l pa r t i c l e s i ze d i s t r i bu t i on o f

f ou r d i f f e ren t samp les hav ing t he same n and d i f f e ren t Xo .

Th i s i l l u s t r a t i on shows t ha t t he samp le r ep resen ted by t he f ou r

p l o t s m igh t have s im i l a r r anges o f s i ze d i s t r i bu t i on ( deno ted by

equa l n ) bu t w i t h poss ib l e va r y i ng deg rees o f f i neness

( i nd i ca ted by t he va r i ous X o ) . The samp le r ep resen ted by p l o t 1

be ing t he f i nes t and t he one by p l o t 4 t he coa rses t o f t he f ou r .

S im i l a r l y , F i gu re 2 .5 ( b ) i l l us t r a tes a s i t ua t i on whe reby t he f ou r

samp les m igh t be o f t he same f i neness (bec ause o f t he same

X o ) bu t poss ib l y w i t h d i f f e ren t s i ze r anges (Wa inwr i gh t and

O lo runsogo , 1999 ) .

2 .8 CONCLUSION

• Tes t r esu l t s i nd i ca te t ha t 2 . 5% added SO 3 may be

su f f i c i en t t o b r i ng t he r esu l t i ng PC to op t imum SO 3 l eve l .

• The spec i f i c g rav i t y and f i neness o f cemen t i nc rease w i t h

an i nc rease i n t he g r i nd i ng t ime .


2-16

• An op t imum o f 4 hou rs g r i nd i ng t ime was es tab l i shed

beyond wh i ch t he wa te r r equ i r emen t i nc rease and t he

s t r eng th e i t he r dec rease o r d i d no t i n c rease s i gn i f i can t l y .

• G rea te r cemen t f i neness i nc reases t he ra t e a t wh i ch

cemen t hyd ra tes and t hus acce le ra tes s t r eng th

deve lopmen t .

• The pa r t i c l e s i ze d i s t r i bu t i on p roduced when a ma te r i a l i s

g round becomes w ide r as t he ma te r i a l becomes eas ie r t o

g r i nd .

• App rox ima te l y 95% o f cemen t pa r t i c l es a re sma l l e r t han

45µm, w i t h t he ave rage pa r t i c l e a round 15µm.

• The 3 -30µm f r ac t i on make s a ma jo r con t r i bu t i on t o t he

28 -day s t r eng th . The range <3µm i s impo r tan t f o r

ach iev i ng h i gh 1 -day s t r eng ths .

• The Ros in -Ramml e r d i s t r i bu t i on f unc t i on can be eva lu a ted

as a me thod p rov i d i ng an easy me ans o f desc r i b i ng t he

pa r t i c l e s i ze d i s t r i bu t i on quan t i t a t i ve l y .


3-1

3. COMPOSITION AND PROPERTIES OF COAL ASH 3 .1 INTRODUCTION

Sus ta inab le deve lopment can be de f ined , as deve lopment , wh ich

meets the needs o f peop le l i v ing today w i thou t compromis ing the

ab i l i t y o f fu tu re genera t ions to mee t the i r own needs . I t requ i res

a long- te rm v i s i on o f i ndus t r ia l p rog ress , p rese rv ing the

founda t ions upon wh ich human qua l i t y o f l i f e depends : respec t

fo r bas ic human need and loca l and g loba l ecosys tems.

Us ing by -p roduc ts f rom o ther i ndus t r ies as raw ma te r ia l i s a

huge oppor tun i t y fo r the cemen t i ndus t r y to reduce i t s

env i ronmenta l impac t , because i t a l l ows compan ies to access

ma te r i a l s fo r use i n the k i l n and the m i l l w i thou t ex t rac t ing them

d i rec t l y f rom the g round . There a re a number o f m inera l by -

p roduc ts tha t con ta in use fu l ma te r ia l s tha t can be ex t rac ted f o r

use in cement p roduc t ion , o r i n mak ing concre te . Typ ica l

add i t i ves inc lude s lag , coa l ash l i ke f l y ash and bo t tom ash , by -

p roduc ts f rom b las t fu rnaces and power gene ra t ion .

Cement , a f i ne g rey powder , se ts a f te r a few hours when mixed

w i th wa te r , and then hardens in a f ew days i n to a so l i d , s t rong

ma te r i a l . V i r t ua l l y a l l t he cement p roduced g loba l l y i s m ixed w i th

sand , aggrega tes and wa te r and used to make conc re te and

mor ta rs .

Cement ex tende rs a re used as a subs t i tu te f o r some o f t he PC in

concre te . The ma in reason fo r the use o f ex tenders i s t he va r ie t y

o f use fu l enhancements , wh ich they g i ve to the concre te

p roper t i es . F l y ash i s one o f the cement ex tende rs common l y

used in Sou th A f r i ca . F l y ash cons is ts o f f i ne l y d i v i ded ashes

p roduced by bu rn ing pu lve r i sed coa l i n power s ta t i ons .

Gas i f i ca t i on ash i s a p roduced as a by -p roduc t du r ing the

gas i f i ca t i on o f coarse coa l . The p roper t i es o f f l y ash can be

used as a gu ide l ine to i nves t iga te o the r ashes fo r use as cemen t

ex tenders in conc re te .


3-2

In t h i s chap te r , the use o f coa l combus t ion by-p roduc ts ,

spec i f i ca l l y f l y ash , i n conc re te w i l l be d i scussed . Cons ide ra t ion

w i l l be g i ven to p roper t i es l i ke shape , pa r t i c le s i ze ,

m inera log ica l and chemica l compos i t i on , du rab i l i t y and the

chemica l requ i rements f o r us ing f l y ash as a cement ex tender .

Th is w i l l p rov ide adequa te unde rs tand ing o f the advan tages tha t

by -p roduc ts have to bo th the cement i ndus t ry and the

env i ronment .

3 .2 COAL ASH

Cur ren t l y , c lose to a b i l l i on tons o f coa l i s bu rned annua l l y i n

the wor ld to gene ra te e lec t r i c i t y and as a resu l t , near l y 130

m i l l i on tons o f coa l combus t ion by -p roduc ts (CCBs) a re

p roduced . One- th i rd o f t hese CCBs a re u t i l i zed , wh i l e the res t

a re d i sposed o f ma in l y i n l and f i l l s (Schwar tz , 2003) . Inc reas ing

cos ts and he igh tened regu la t ions a re mak ing the d i sposa l o f

CCBs an undes i rab le op t ion . U t i l i za t ion o f CCBs as raw

ma te r i a l s resu l t s i n numerous bene f i t s , i nc lud ing :

• A dec rease in t he demand fo r l and f i l l space

• Conserva t ion o f na tu ra l resources

• A c leaner sa fe r env i ronment

• Reduced ca rbon d iox ide emiss ions

• S ign i f i can t economic sav ings fo r end use rs

• A boos t i n economic deve lopment

• Reduced overa l l cos t o f genera t i ng e lec t r i c i t y

E lec t r i c i t y i s the fue l o f the “ In fo rmat ion age ” and power p lan ts

tha t bu rn coa l accoun t fo r more than ha l f o f the e lec t r i c i t y

p roduced . These power p lan ts a l so p roduce coa l combus t ion by -

p roduc ts l i ke f l y ash (wh ich i s cap tu re f rom the exhaus t o f t he

bo i le r ) and bo t tom ash (wh ich i s heav ie r and fa l l s to the bo t tom

o f the bo i le r ) . CCBs a re cons ide red to be fou r d i s t i nc t and


3-3

ex t reme ly d i f f e ren t mate r ia l s , as seen in F igu re 3 .1 (Amer ican

Coa l Ash Assoc ia t i on , 1997 ) .

Coa l bo t tom ash and bo i le r s lag a re the coarse , g ranu la r ,

i ncombus t ib le by -p roduc ts t ha t a re co l lec ted f rom the bo t tom o f

fu rnaces tha t bu rn coa l fo r the genera t i on o f s team and the

p roduc t ion o f e lec t r i c i t y . Bo t tom ash i s a da rk g ray , g ranu la r ,

po rous , p redominan t l y sand s i ze ( -12 .7mm) ma te r i a l (Babcock ,

1978 ) . Ma te r i a l d rops i n to a wa te r f i l l ed hopper a t the bo t tom o f

the fu rnace . The ma te r i a l i s removed by means o f h igh -p ressure

wa te r j e ts and conveyed by s lu i ceways e i the r to a d i sposa l pond

o r to a decan t bas in . F rom he re the mate r ia l i s dewate red ,

c rushed and s tockp i led fo r d i sposa l o r use (Hec t , 1975) .

Bo t tom ash app l i ca t ions a re snow and i ce con t ro l , as aggrega te

in l i gh twe igh t conc re te masonry un i t s , and raw feed mate r i a l f o r

the p roduc t ion o f PC. Bo t tom ash has a lso been used as a road

base and subbase agg rega te , s t ruc tu ra l f i l l ma te r ia l (ASTM

E1861-97 ) , and as f i ne aggrega te in aspha l t pav ing .

F l ue gas desu lphu r i sa t i on (FGD) gypsum i s a l so known as

sc rubbe r gypsum. FGD gypsum i s t he by -p roduc t o f an a i r

po l l u t i on con t ro l s ys tem th a t r emo ves su lphu r f r om th e f l ue gas

i n ca l c i um-based sc rubb ing sys tems . I t i s p roduced by

emp loy i n g f o r ced ox i da t i on i n t he sc rubbe r and i s composed

mos t l y o f ca l c i um su lpha te .

The ma jo r i t y o f FDG-p rod uced gypsum used i n t he Un i t ed

S ta tes (Amer i can Coa l Ash Assoc ia t i on , 1997 ) i s emp loyed f o r

wa l l boa rd , wh i ch reduced the need f o r m in i ng na tu ra l gypsum.

As an add i t i ve i n PC , FDG gypsum i s used t o r e ta rd se t t i ng .

Th i s enab les we t cemen t i n r eady -m ix t r uck s t o be t r anspo r t ed

g rea te r d i s t ances wh i l e rema in i ng wo rkab le . Gypsum ’s h i gh

pe rmeab i l i t y ( 10 -3cm/sec ) makes i t an exce l l en t so i l

cond i t i one r . S te f f an ( 1991 ) i nd i ca tes t ha t FGD g ypsum o f f e r s

seve ra l ma jo r be ne f i t s as a so i l amendme n t . These i nc l ude


3-4

ad jus tmen t o f so i l pH and means o f keep ing peanu t s and o the r

c rops d i sease - f r ee .

F igu re 3 .1 Coa l combus t i on by -p rodu c t s

The f ou r t h CCB i s f l y ash wh i ch i s mos t o f t en used i n conc re te

as a r ep lacemen t f o r pa r t o f t he PC i n t he m ix des ign . The use

o f f l y ash as an ex tende r i n conc re te w i l l be d i scussed l a t e r i n

t h i s chap te r .

3 .3 POZZOLANIC REACTION

The Amer i can Soc ie t y f o r Tes t i ng Ma te r i a l s (ASTM) de f i nes a

pozzo lan as ‘ a s i l i ceous o r s i l i ceous and a l um inous ma te r i a l ,

wh i ch i n i t se l f possesses l i t t l e o r no cemen t i t i ous p rope r t y bu t

wh i ch w i l l , i n f i ne l y d i v i ded f o rm and i n t he p resence o f

mo i s tu re , chem ica l l y r eac t w i t h ca l c i um hyd rox i de a t o rd i na ry

t empe ra tu re t o f o rm compounds possess ing cemen t i ng

p rope r t i es ’ .

As a pozzo lan ic ma te r i a l f l y ash con ta ins ac t i ve s i l i ca (S iO 2 ) ,

and i s no t cemen t i t i ous in i t se l f bu t w i l l chemica l l y reac t w i th

ca lc ium hydrox ide in the p resence o f mo is tu re to fo rm

cement i t i ous compounds ( I l l s ton , 2001) . When a pozzo lan ic

ma te r i a l i s used in con junc t i on w i th a PC, the ca lc ium hyd rox ide

tha t takes pa r t i n the pozzo lan ic reac t ion i s t ha t p roduced f rom


3-5

the cement hyd ra t ion . More quan t i t i es o f ca l c ium s i l i ca te

hydra te a re p roduced (see equa t ion 3 .1 ) .

2S + 3CH → C 3 S 2 H 3 (equa t ion 3 .1 )

I t i s c l ea r t ha t t he pozzo lan ic reac t ion i s secondary to t he

hydra t ion o f PC. The deg ree o f hyd ra t ion o f f l y ash i s i nc reased

in the p resence o f gypsum because the su r face i s ac t i va ted by

the des t ruc t i on o f the s t ruc tu re o f the g lass and c rys ta l l i ne

phases caused by the d i ssoc ia t ion o f A l 2 O 3 reac t i ng w i th SO 4-

(Uch ikawa, 1986) . The p roduc ts o f the pozzo lan ic reac t i on make

the i r own con t r ibu t ion to the s t reng th and o the r p roper t i es o f t he

cement and conc re te .

3 .4 FLY ASH

F l y ashes (FA ) cons i s t o f f i ne l y d i v i ded ashes p roduced by

bu rn i ng pu l ve r i sed coa l i n power s t a t i ons as seen i n F i gu re 3 .2 .

They a re r emoved f r om the combus t i on gases and co l l ec ted by

spec ia l mechan i ca l dev i ces and e l ec t r os ta t i c p rec i p i t a t o r s .

Ow ing t o t he h i gh t empe ra tu res r eached du r i ng t he

i ns tan taneous bu rn i ng o f coa l , mos t o f t he m ine ra l componen t

con ta i ned i n t he coa l me l t s and f o rms sma l l f used d rops . The

subsequen t sudden coo l i ng t r ans fo rms t hem pa r t l y o r en t i r e l y

i n t o sphe r i ca l g l ass pa r t i c l es . The recogn i t i on t ha t f l y ash

exh ib i t s pozzo lan i c p rope r t i es has l ed t o i t s use as a

cons t i t uen t o f conc re te . F l y ashes con ta i n me tas tab le

a l um inos i l i ca tes tha t w i l l r eac t w i t h ca l c i um i ons i n t he

p resence o f mo is tu re t o f o rm ca l c i um s i l i ca te hyd ra tes

(Massazza , 1998 ) . F l y ash p roduced i n Sou th A f r i ca i s a f i ne

powde r , t he pa r t i c l es o f wh i ch a re round ho l l ow sphe res ( see

F igu re 3 .3 ) .


3-6

F igu re 3 .2 A modern pu l ve r i sed coa l - f i red the rma l power s ta t ion

(K rüge r , 1999 ) .

F l y ash i s used i n conc re te e i the r as pa r t o f b lended cement o r

as a separa te componen t added a t the s tage when the concre te

m ix i s p repared . The inc lus ion o f f l y ash in conc re te a f fec ts a l l

aspec ts o f conc re te . As pa r t o f t he compos i te conc re te mass ,

f l y ash ac ts bo th as a f i ne aggrega te and as a cement i t i ous

componen t . I t i n f l uences the rheo log ica l p roper t i es o f the f res h

concre te and the s t reng th , f i n i sh , po ros i t y , and durab i l i t y o f the

ha rdened mass as we l l as the cos t and ene rgy consumed in

manu fac tu r ing the f i na l p roduc t (Massazza , 1998) .

3 .4 .1 Phys ica l Proper t ies

F ly ash par t i c les a re mos t l y spher i ca l i n shape (see F igu re 3 .3 )

w i th s i zes rang ing f rom approx ima te l y 1 to 100μm in d iamete r ,

w i th an ave rage s i ze o f 20μm (Care t te , 1986) . The su r face a rea

o f f l y ash pa r t i c l es va ry f rom 2000 cm 2 /g to 10 000 cm 2 /g

depend ing on the p ropor t i on o f f i ne pa r t i c l es in the f l y ash .

E rdogdu (1998 ) f ound tha t conc re te con ta in ing a f i ne r f rac t ion o f

f l y ash gave a be t te r compress ive s t reng th than tha t w i thou t f l y

ash o r conc re te con ta in ing coarse r f l y ash . The pa r t i c le s i ze

d i s t r i bu t i on , shape and su r face cha rac te r i s t i c s o f f l y ash have a


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cons ide rab le i n f l uence on the wa te r requ i rement and workab i l i t y

o f f resh l y made concre te and on the ra te o f s t reng th

deve lopment i n ha rdened concre te .

F igu re 3 .3 E lec t ron m ic roscope pho tograph o f f l y ash .

3 .4 .2 Chemica l Composi t ion

The chemica l compos i t i on o f f l y ash depends on the

charac te r i s t i cs and compos i t i on o f the coa l bu rned in power

s ta t ions . The chemica l ana lys is o f f l y ashes by means o f X - ray

f l uo rescence (XRF) and spec t rome t ry techn iques shows tha t

S iO 2 , A l 2 O 3 , Fe 2 O 3 , and CaO are the ma jo r cons t i tuen ts o f mos t

f l y ashes . Tab le 3 .1 shows the t yp ica l chemica l compos i t i on o f

f l y ash .


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Tab le 3 .1 Typ ica l chemica l compos i t i on o f f l y ash (Add is , 2001)

Oxide % By mass S iO 2 45-50

Al 2 O 3 25-30

CaO 4-8

FeO 9 -11

MgO 2-4

Na 2 O + 0 .658K 2 O 1 -3

3 .4 .3 Minera log ica l Compos i t ion

Both the t ype and source o f f l y ash i n f l uence i t s m inera log ica l

compos i t i on . Due to the rap id coo l i ng o f bu rned coa l i n t he

power p lan t , f l y ash cons is ts o f nonc rys ta l l i ne pa r t i c l es (≤ 90%) ,

o r g lass and a sma l l amoun t o f c r ys ta l l i ne mate r ia l .

I n add i t i on to a subs tan t i a l amoun t o f g lassy ma te r i a l , each f l y

ash may con ta in one o r more o f the fou r ma jo r c rys ta l l i ne

phases : qua r tz , mu l l i t e , magne t i te , and hemat i te . I n

subb i tuminous f l y ashes , the c rys ta l l i ne phases may inc lude C 3 A,

C 3 A 3 S , ca lc ium su lpha te , and a lka l i su lpha tes (Metha , 1989) .

The reac t i v i t y o f f l y ashes i s re la ted to t he noncrys ta l l i ne phase

o r g lass . D iamond (1981) po in ted ou t tha t t he compos i t i on o f

g lass in l ow-ca lc i um f l y ashes i s d i f fe ren t f rom tha t i n h igh -

ca lc ium f l y ashes . X- ray d i f f rac t ion (XRD) ind ica tes tha t Sou th

A f r i can f l y ash cons is ts m inera log ica l l y ma in ly o f g lass and

some low-quar tz (S iO 2 ) , mu l l i t e (A l 6 S i 2 O 1 3 ) and some qu ick l ime

(CaO) .

3 .4 .4 Chemica l Spec i f ica t ions

I n Sou th A f r i ca f l y ash shou ld comp ly w i th t he requ i rements o f

the Sou th A f r i can s tanda rd spec i f i ca t ion fo r Po r t l and cement

ex tenders (SANS 1491-2 :2005 / SABS 1941-2 :2005) . F l y ash

comp ly ing w i th SANS 149-2 may be used as a cement ex tender


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w i th Por t l and cement fo r use in conc re te when i t con fo rms to

Tab le 3 .2 .

Loss on ign i t i on , the we igh t l oss o f f l y ashes burned a t

tempera tu res ≤ 1000°C, i s re la ted to the p resence o f ca rbona tes ,

comb ined wa te r i n res idua l c lay m inera ls , and combus t ion o f

f ree ca rbon . The wa te r requ i red fo r wo rkab i l i t y o f mor ta rs and

concre tes depends on the ca rbon con ten t o f f l y ashes : the

h ighe r the ca rbon con ten t o f a f l y ash , the more wa te r i s needed

to p roduce a pas te o f no rma l cons is tency .

Tab le 3 .2 Chemica l spec i f i ca t ions fo r cement ex tenders . (SANS

1491-2 :2005 / SABS 1941-2 :2005)

Test F ly ash max a l lowed

Su lphur t r i ox ide con ten t , % (m/m) 2 .5

Loss on i gn i t i on , % (m/m) 5 .0

F ree wa te r con ten t , % (m/m) 1 .0

F ineness , res idue re ta ined on a s ieve w i th square aper tu res o f nomina l s i ze 45μm, % (m/m) 12 .5

Wate r requ i rement , % o f con t ro l 95

S t reng th fac to r , % 6

Soundness , expans ion , mm 5

3 .5 INFLUENCE OF FLY ASH ON THE PROPERTIES OF CONCRETE

3 .5 .1 Fresh Concrete

Al though concre te i s i n the f resh s ta te fo r on l y a few hours , the

p roper t i es o f f resh conc re te a re impor tan t because they

in f l uence the hand l ing o f t he conc re te , t he degree to wh ich i t

can be compac ted and the un i fo rm i t y o f d i s t r i bu t ion o f

cons t i tuen ts w i th in the conc re te .


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3 .5 .1 .1 Wate r Demand

Dav is (1937) no ted , f l y ash d i f fe rs f rom o ther pozzo lans , wh ich

inc rease the wa te r requ i rement o f conc re te m ixes . The improved

workab i l i t y a l l ows a re duc t i on in the amoun t o f wa te r used i n

conc re te . Par t i a l rep lacement o f OPC by f l y ash , i n conc re te

reduces the wa te r requ i rement to ob ta in a g i ven cons is tency

(Ma lho t ra , 1996) . Th is i s genera l l y a t t r i bu ted to t he spher i ca l

shape and smooth tex tu re o f the f l y ash pa r t i c l es .

Accord ing to Owens (1979) t he ma jo r fac to r i n f l uenc ing the

e f fec ts o f ash on the workab i l i t y o f conc re te i s the p ropor t i on o f

coarse mate r i a l (>45µm) i n the ash . Very f i ne pa r t i c l es o f f l y ash

ge t abso rbed on the oppos i te l y charged su r face o f cement

pa r t i c l es and p reven t them f rom f loccu la t ion . The cemen t

pa r t i c l es a re thus e f fec t i ve l y d i spersed and w i l l no t t rap la rge

amounts o f wa te r , wh ich means tha t the sys tem w i l l have a

reduced wa te r requ i rement fo r f l ow. I n add i t i on , Por t l and cemen t

pa r t i c l es a re mos t l y i n t he s i ze range o f 1 t o 50μm, wh ich cause

the m ic ro f i ne pa r t i c les o f f l y ash to reduce the vo id space and

co r respond ing l y the wa te r requ i rement .

The re la t ionsh ip be tween the amoun t o f wa te r and the

pe rcen tage o f f l y ash rep lacement fo r the same workab i l i t y w i th

21 , 28 and 34 MPa nomina l -s t reng th conc re te can be seen i n

F igu re 3 .4 . As the amount o f f l y ash inc reased in the m ix tu re ,

the wa te r requ i rement dec reased (Na i k , 1990) .


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F igu re 3 .4 Re la t ionsh ip be tween wa te r requ i rement and cemen t

rep lacement w i th f l y ash (Na ik , 1990 )

3 .5 .1 .2 Workab i l i t y

The ACI Commi t tee 116R-00 :2000 has p rov ided the mos t

su i tab le de f in i t i on o f workab i l i t y , wh ich reads as fo l l ows :

“ tha t p roper t y o f f resh l y m ixed concre te o r mor ta r wh ich

de te rm ines the ease and homogene i t y w i th wh ich i t can be

m ixed , p laced , conso l ida ted and f i n i shed . ”

The workab i l i t y ( f l u id i t y ) o f a Po r t l and concre te can be improved

when par t o f the OPC i s rep laced w i th f l y ash . B rown (1982 )

found tha t bo th s lump and V-B workab i l i t y improved w i th

inc reased ash subs t i tu t i ons . The ex ten t o f t he improvements

depends on the f i neness and ca rbon con ten t o f the f l y ash .

Rheo log i ca l p rope r t i es and f l u id i t y has been found to depend on

the pa r t i c le s i ze d i s t r i bu t ion o f cemen t (Gosh , 1983 ) . Lee (2002 )

found tha t the f l u i d i t y o f a f l y ash -cement sys tem inc rease as

the pa r t i c le s i ze d i s t r i bu t ion becomes w ide r . When workab i l i t y i s

kep t cons tan t t he wa te r con ten t o f a f l y ash m ix dec reases w i th

an inc rease in t he f i neness o f the f l y ash .


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3 .5 .2 Hardened Concre te

The s t reng th o f ha rdened concre te i s o f fundamenta l impor tance

to s t ruc tu ra l des igners . I t i s a l so ex tens i ve l y used as an i ndex

o f o the r p rope r t i es and o f conc re te qua l i t y .

3 .5 .2 .1 Compress i ve S t reng th Deve lopment

The measured compress i ve s t reng th o f conc re te depends on the

in t r i ns i c p roper t i es o f the concre te . Many va r i ab les i n f l uence the

s t reng th deve lopment o f f l y ash conc re te , these be ing :

• p roper t i es o f f l y ash

• chemica l compos i t i on

• pa r t i c l e s i ze

• reac t i v i t y

• t empera tu re and cu r ing cond i t i ons

A t ea r l y ages the compress ive s t reng ths (up to 28 days ) o f a l l

conc re tes con ta in ing f l y ash a re lower than tha t o f t he

co r respond ing concre te con ta in ing norma l Po r t l and cemen t .

A f te r 28 days , i f we t cu r ing i s con t inued , the compress i ve

s t reng th o f f l y ash concre te w i l l be h igher t han the Por t l and

concre te (K rüge r , 1999 ) . Th is i s demons t ra ted in F igu re 3 .5 .


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F igu re 3 .5 Deve lopment o f compress ive s t reng ths o f Por t l and

cement and f l y ash concre tes ( f rom Krüge r , 1999)

Par t i c le s i ze can in f l uence the s t reng th deve lopmen t i n two

ways . Pa r t i c les la rger t han 45μm in f luence wa te r requ i remen ts

adverse l y . They coun te rac t t o the needs o f the me thods used to

compensa te fo r the s low ra te o f reac t ion o f f l y ash a t ea r l y ages .

Cement ing ac t i v i t y occurs on the su r face o f the so l i d phases ,

th rough p rocesses invo l v i ng the d i f fus ion o f ma te r ia l s i n

concen t ra ted pas tes . F igu re 3 .6 shows tha t f i ne r f l y ashes

impar ted g rea te r compress i ve s t reng ths (Josh i , 1982) .


3-14

F igu re 3 .6 E f fec t o f coarse f rac t ions o f f l y ash on compress i ve

s t reng th deve lopment o f conc re tes (Josh i , 1982)

Conc re te con ta in ing f l y ash shows s t reng th ga in as a

consequence o f hea t ing in con t ras t to the loss o f s t reng th tha t

occurs w i th no rma l Por t l and cement (Ma lho t ra , 1996) . Th is

p roper t y o f f l y ash i s o f g rea t va lue i n the cons t ruc t i on o f mass

concre te o r i n conc re te cons t ruc t i on a t e leva ted tempera tu res .

The e f fec t o f cu r i ng tempera tu re on the s t reng th deve lopment o f

conc re te con ta in ing f l y ash can be seen in F igu re 3 .7 .


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F igu re 3 .7 Compress i ve s t reng ths o f PC and PC/30FA a t

d i f f e ren t t empera tu res (K rüger , 1999 ) .

3 .5 .2 .2 F lexura l S t rength

There i s a genera l t rend fo r the f l exu ra l to compress i ve s t reng th

ra t io t o i nc rease w i th an i nc rease in f l y ash con ten t . The resu l t s

p resen ted in F igu re 3 .8 , po in ts ou t tha t t he inc rease i s s l i gh t fo r

wa te r cement (w /c ) ra t i os a round 0 .5 . The f l exu ra l t o

compress ive s t reng th ra t io o f Por t l and cement conc re te i s

s im i l a r t o tha t o f PC/FA conc re te o f s im i l a r s t reng th . Compar ing

the f l exu ra l to compress i ve s t reng th ra t ios o f t he PC and PC/FA

mor ta r a t s im i la r compress i ve s t reng th , a l though no t reached a t

the same age , the resu l t s i nd ica te tha t the ra t io f o r t he PC/FA

mor ta r i s somewhat h ighe r t han tha t f o r the PC mor ta r .


3-16

F igure 3 .8 The in f l uence o f FA con ten t o f the cement i t i ous

ma te r i a l on the f l exu ra l / compress i ve s t reng th ra t i o o f conc re te

(K rüge r , 1999 )

3 .5 .2 .3 Modulus o f E las t ic i ty

The modu lus o f e las t i c i t y o f a mate r ia l i s de f i ned by the s t ress :

s t ra in cu rve . The h igher the e las t i c modu lus , the more res is tan t

the ma te r ia l i s t o de fo rmat ion .

There appears to be no s ign i f i can t d i f f e rence be tween the

modu lus o f e las t i c i t y o f conc re te w i th o r w i thou t f l y ash a t 28

days . However , l i ke compress ive s t reng th , conc re te w i th f l y ash

has a lower modu lus a t ea r l y age s t reng th and h ighe r modu lus

a t u l t ima te s t reng th compared w i th concre te w i thou t f l y as h

(Lane , 1982) . The e f fec t o f f l y ash con ten t on the re la t i onsh ip

be tween compress ive s t reng th and e las t i c i t y can be seen in

F igu re 3 .9 .


3-17

F igu re 3 .9 The in f l uence o f FA on the e las t i c modu lus /

compress ive s t reng th o f conc re te (K rüge r , 1999)

3 .5 .2 .4 Dry ing Shr inkage

When a hydrau l i c cemen t -bonded p roduc t such as conc re te

looses i t s f ree mo is tu re , i t sh r inks (d ry ing sh r inkage) and when

i t ga ins i n mo is tu re con ten t , i t expands (we t t i ng expans ion ) . The

d imens iona l change w i th va r ia t i on in mo is tu re con ten t o f

conc re te i s and impor tan t p rope r t y , because i f d i f f e ren t ia l

d imens iona l movement i n t he conc re te due to such a change i s

excess i ve , c rack ing may occur . I f a d imens iona l l y s tab le

aggrega te i s used , d ry ing sh r inkage and we t t i ng expans ion can

a lmos t exc lus ive l y be a t t r i bu ted to the b inder and i s a f fec ted by

fac to rs such as b inder con ten t , wa te r / cement ra t io , cu r ing and

the s t reng th o f the conc re te (Add is , 2001) .

Work by Gr ieve (1991) on concre te made w i th a Sou th A f r i can

f l y ash , showed tha t fo r s im i la r exposure cond i t i ons , the d ry ing

sh r inkage o f such conc re tes i s ve ry s im i l a r t o p la in PC, ove r a

range o f f l y ash con ten ts up to 30%. Th i s i s con f i rmed by

s tud ies o f Yuan (1983) wh ich conc luded tha t t he rep lacement o f

cement w i th f l y ash has l i t t l e i n f l uence on d ry ing sh r inkage (see

f i gu re 3 .10 ) . Ch indapras i r t (2003) f ound tha t the i nco rpora t ion

o f f l y ashes reduce the d ry ing sh r inkage in compar i son w i th tha t


3-18

o f PC. The ea r l y sh r inkage o f mor ta r w i th f i ne r f l y ash was found

to be a l i t t l e l a rge r than tha t o f the coarse r f l y ash mor ta r .

F igu re 3 .10 Dry ing sh r inkage o f conc re te inco rpo ra t i ng f l y ash

(Yuan , 1983)

3 .5 .2 .5 Creep

C reep i s de f ined as the inc rease in s t ra in (de fo rmat i on ) unde r a

sus ta ined s t ress ( l oad ) (Ho lc im, 2005) . C reep impar ts t o

conc re te a degree o f duc t i l i t y , wh ich i s des i rab le f rom the po in t

o f v iew o f s t ruc tu ra l behav iou r . However , c reep a lso has

de t r imen ta l e f fec ts on s t ruc tu res , such as inc rease de f lec t ions

wh ich can resu l t i n c rack ing , l oss o f p re -s t ress and buck l i ng o f

l ong co lumns (Add is , 2001) .

Gr i eve ’s (1991) work on concre te i nco rpora t ing f l y ash found

tha t spec i f i c c reep was reduced in f l y ash m ixes re la t i ve to p la in

m ixes w i th s im i l a r 28 -day s t reng ths . Th is con f i rms the work

done by Pandey (1983) wh ich found tha t f l y ash concre te ’s

showed l ess c reep in the ma jo r i t y o f spec imens than the

re fe rence concre te ’ s showed.


3-19

3 .6 DURABIL ITY OF CONCRETE

Durab i l i t y may be de f ined as the ab i l i t y o f conc re te to rema in

fu l l y f unc t iona l ove r an ex tended per i od under p reva i l i ng se rv i ce

cond i t i ons fo r the pu rpose fo r wh ich i t was des igned . Concre te

w i l l rema in du rab le i f movement o f aggress i ve chemica l s w i th in

i t s s t ruc tu re i s m in im ised .

Deg rada t i on o f conc re te can be a resu l t o f t he env i ronment to

wh ich the conc re te i s exposed , o r f rom in te rna l causes w i th in

the conc re te . The ra te o f degrada t ion i s con t ro l l ed by the ra te a t

wh ich mo is tu re , a i r o r o the r aggress i ve agen ts can pene t ra te t he

conc re te . Thus cons ide r i ng the va r i ous t ranspor t mechan isms

l i ke po ros i t y and permeab i l i t y th ro ugh conc re te w i l l i nd i ca te the

in f l uence on the du rab i l i t y o f conc re te .

3 .6 .1 Poros i ty

Hardened cemen t pas tes and concre te con ta in po res o f va ry ing

t ypes and s i zes , and the re fo re the t ranspor t o f ma te r i a l s th rough

concre te can be cons ide red as the phenomenon o f f l ow th rough

a po rous med ium. The ra te o f f l ow w i l l no t on ly depend on the

poros i t y , bu t on the deg ree o f con t inu i t y o f t he pores and the i r

s i ze . A low poros i t y resu l t s i n h igh s t reng ths and l ow

permeab i l i t y i n conc re te .

The pozzo lan ic reac t ion i n f l y ash p roduces more ca lc ium

s i l i ca te hyd ra te , wh ich tends to f i l l po re spaces . F l y ash have a

l ower wa te r con ten t t han PC fo r the same workab i l i t y and as a

resu l t o f these fac to rs the poros i t y o f f l y ash concre te i s l ower

then PC.

3 .6 .2 Permeabi l i ty

Permeab i l i t y can be de f ined as the ease w i th wh ich a l i qu id o r a

gas f l ows in to ( th rough ) conc re te under a p ressure d i f f e ren t ia l

ac ross the conc re te . I t i s measured by the vo lume o f l i qu id o r


3-20

gas t ransmi t ted pe r un i t a rea per t ime per un i t p ressure

d i f fe rence .

The ma jo r e f fec t on the pe rmeab i l i t y o f conc re te i s the cu r ing

reg ime . A i r exposure under d ry cond i t i ons i s the mos t

d i sadvan tageous . Wate r cu r ing g i ves the mos t impermeab le

conc re te . Ano the r e f fec t on the pe rmeab i l i t y o f conc re te i s the

s t ronger the conc re te and the lower the wa te r / cement ra t io ; t he

more impermeab le the conc re te .

F l y ash has the e f fec t o f reduc ing the pe rmeab i l i t y and vo lume

o f l a rge cap i l l a ry po res i n conc re te when compared w i th a p la in

CEM I conc re te o f s im i l a r s t reng th (Ba l im, 1993 ) . Th is e f fec t

d r i ves fo rm the f i neness o f the mate r ia l , t he pozzo lan ic reac t ion

and the reduced wa te r requ i rement o f the f l y ash m ixes . The

f l u id t ranspor t p roper t i es o f conc re te made w i th f l y ash a re

the re fo re cons ide rab ly reduced , thus enhanc ing the du rab i l i t y .

3 .7 ADVATAGES OF USING FLY ASH IN CONCRETE

The use o f f l y ash in conc re te has the fo l l ow ing advan tages :

• Reduc t ion in ma te r ia l cos t and the sav ing o f ene rgy by

sav ing on cement .

• Reduc t ion in bu i l d ing cos t because o f improved workab i l i t y

o f conc re te

• Be t te r wo rkab i l i t y and cohes iveness

• Reduced wa te r requ i rement fo r a g i ven s lump

• Improved impermeab i l i t y

• Reduced wa te r pene t ra t ion o f conc re te

• Reduc t ion in sh r inkage

• Improves the durab i l i t y o f conc re te i n agg ress ive

env i ronments


3-21

3 .8 CONCLUSION

• F l y ash i s a was te ma te r i a l o f t he combus t i on o f

pu l ve r i sed coa l i n t he rma l power p l an t s . F l y ash i s us ed

i n conc re te f o r econom ic , env i r onmen ta l and du rab i l i t y

cons ide ra t i ons as a cemen t ex tende r .

• The p roduc t s o f t he pozzo lan i c r eac t i on make t he i r own

con t r i bu t i on t o t he s t r eng th and o the r p rope r t i es o f t he

cemen t and conc re te .

• The pozzo lan i c , chem ica l , phys i ca l and du rab i l i t y

p rope r t i es o f f l y ash have l ed t o i t s use as a cemen t

ex tende r i n conc re te . The p rope r t i es o f f l y ash can be

used t o i nd i ca te whe the r a gas i f i ca t i on ash i s su i t ab l e f o r

use as a cemen t ex tende r i n conc re te .

• Po r t l and cemen t pa r t i c l es a re mos t l y i n t he s i ze r ange o f

1 t o 50μm, wh i ch cause t he m ic ro f i ne pa r t i c l es o f f l y ash

t o r educe t he vo id space and co r respond ing l y t he wa te r

r equ i r emen t .

• When wo rkab i l i t y i s kep t cons tan t t he wa te r c on ten t o f a

f l y ash m ix dec reas es w i t h an i nc rease i n t he f i neness o f

t he f l y ash .

• Conc re te con ta i n i ng f l y ash shows s t r eng th ga in as a

consequence o f hea t i ng i n con t ras t o t he l oss o f s t r eng th

t ha t occu rs w i t h no rma l Po r t l and cemen t .

• The re i s a gene ra l t r end f o r t he f l exu ra l t o compress i ve

s t r eng th r a t i o t o i nc rease w i t h an i nc rease i n f l y ash

con ten t .

• The re appea rs t o be no s i gn i f i can t d i f f e rence be tween t he

modu lus o f e l as t i c i t y o f conc re te w i t h o r w i t hou t f l y ash a t

28 days .

• The rep lacemen t o f cemen t w i t h f l y ash has l i t t l e

i n f l uence on d r y i ng sh r i nkage .


3-22

• F l y ash conc re te ’ s showed l ess c reep i n t he ma jo r i t y o f

spec imens t han t he r e fe rence conc re te ’ s showed .

• F l y ash have a l o we r wa te r con ten t t han PC fo r t he same

wo rkab i l i t y and as a r esu l t o f t hese f ac to r s t he po ros i t y o f

f l y ash conc re te i s l owe r t hen PC .

• The f l u i d t r anspo r t p rope r t i es o f conc re te made w i t h f l y

ash a re t he re fo re cons ide rab l y r educed , t hus enhanc ing

t he du rab i l i t y .

• Cons ide ra t i on o f p rope r t i es l i ke shape , pa r t i c l e s i ze ,

m ine ra l og i ca l and chem ica l compos i t i on , s t r eng th ,

e l as t i c i t y , sh r i nkage and the chem ica l r equ i r emen ts f o r

us i ng f l y ash as a cemen t e x tende r shou ld be

i nves t i ga ted when us i ng gas i f i ca t i on ash as a cemen t

ex tende r .


4-1

4. EXPERIMENTAL PROGRAMME AND TEST PROCEDURES FOR CEMENT

4 .1 INTRODUCTION

The a im o f t h i s s tudy i s t o de te rm in e whe the r gas i f i ca t i on ash

can be used as a cemen t ex tende r i n conc re te . Cu r ren t l y

pu l ve r i sed f ue l ash (a l so ca l l ed f l y ash ) i s w ide l y used as a

cemen t ex tende r i n conc re te and t he e f f ec t o f t h i s t ype o f ash

i s we l l es tab l i shed . I n t h i s s t udy t he p rope r t i es o f cemen t and

gas i f i ca t i on ash i s exam ined t o es tab l i sh pa rame te r s f o r

cemen t b l ended w i t h gas i f i ca t i on ash .

The a im o f t h i s chap te r i s t o d i scuss t he t es t i ng me thods used

i n t he p rac t i ca l ana l ys i s o f t he r ea c t i v i t y o f a gas i f i ca t i on ash .

Pa rame te rs l i ke g r i nd i ng t ime and op t imum g yp s um con ten t was

es tab l i shed f r om the phys i ca l and chem ica l p rope r t i es o f t he

gas i f i ca t i on ash by pe r f o rm ing t es t s f o r pa r t i c l e s i ze

d i s t r i bu t i ons ; s cann ing e l ec t r on m i c roscopy pho to ’ s and x - ra y

ana l ys i s . S tanda rd t es t pe r f o rmed f o r cemen t i t i ous ma te r i a l s

w i l l be d i scussed . Tes t me thods i nc l ude t he cas t i ng and

t es t i ng o f mo r ta r p r i sms and ca lo r ime t r y t es t i ng .

4 .2 PREP AR ATION OF MATE R IALS

I n an e f f o r t t o reduce t he env i r onmen ta l impac t o f cemen t

p roduc t i on , cemen t manu fa c tu re r s a re i nc reas ing t he use o f

was te ma te r i a l s t o r ep l ace a f r ac t i on o f t he cemen t c l i n ke r .

I n t h i s p ro j ec t cemen t i s manu fac tu red i n t he l abo ra to r y us i ng

cemen t c l i n ke r ob ta i ned f r om a cemen t f ac to r y . The c l i nke r was

g round i n a ba l l m i l l ( see f i gu re 4 .1 ) w i t h 25kg o f r ound s tee l

ba l l s . The s tee l ba l l s ( s ee f i gu re 4 .2 ) we re i nd i v i dua l l y

measu red and we i ghed t o de te rm ine t he i r s i ze d i s t r i bu t i on as

i nd i ca ted i n F i gu re 4 .3 .


4-2

F i gu re 4 .1 Labo ra to r y ba l l m i l l u sed i n expe r imen t

F i gu re 4 .2 S tee l ba l l s used f o r g r i nd i ng

A l l t he samp les g round we re s i eved t h rough a 1 .18µm s i eve

and s to red i n a i r - t i gh t con ta i ne rs .


4-3

0

20

40

60

80

100

1 10 100

Sieve size, mm

Cum

ulat

ive

perc

enta

ge

pass

ing

%

F i gu re 4 .3 Cumu la t i ve pa r t i c l e s i ze o f s t ee l ba l l s

Cemen t and gas i f i ca t i on ash i s g round f o r d i f f e ren t t ime

i n t e r va l s t o es tab l i sh an op t imum g r i nd i ng t ime . The g r i nd i ng

t ime i n t e r va l s we re ; 30 m inu tes , 1hou r , 1hou r 30 m inu tes , 2

hou rs , 2hou r 30 m inu tes and 4hou rs . The expe r imen t i nc l uded

i n t e rb l end ing cemen t and gas i f i ca t i on ash a f t e r g r i nd i ng each

ma te r i a l sepa ra te l y , an d i n t e rg r i nd i ng o f cemen t and

gas i f i ca t i on ash by i n t e rb l end ing t he two ma te r i a l s i n t he ba l l

m i l l and g r i nd i ng i t t oge the r . No gypsum was added t o t he

cemen t c l i n ke r i n t he ba l l m i l l .

An op t imum g r i nd i ng t ime was es tab l i shed by cons ide r i ng t he

pa r t i c l e s i ze and t he f l e xu ra l and compress i ve r esu l t s o f mo r ta r

p r i sms .

The e f f ec t o f gypsum on cemen t and gas i f i ca t i on ash was

exam ined . As gypsum has a d i r ec t i n f l uence on t he se t t i ng t ime

and hea t o f hyd ra t i on an op t imum g y psum con ten t was

es tab l i shed . To de te rm ine t he op t imum gypsu m con ten t , hea t o f

hyd ra t i on cu r ves we re es tab l i shed and i so the rma l ca l o r ime t r y

t es t s we re pe r f o rmed on samp les w i t h d i f f e ren t gypsum

rep lacemen t l eve l s .


4-4

4 .3 PHYSI CA L AND C HEMI CAL PROP ER TIES OF GASIF I C AT ION ASH

The f eed t o Saso l gas i f i e r s p r i nc i pa l l y cons i s t s o f coa rse coa l

( >5mm) and ex t r aneous rock f r agmen ts ( s t one ) . Du r i ng t he

gas i f i ca t i on o f t h i s coa rse coa l a t e l eva ted t empe ra tu res and

p ressu re a m i x tu re o f ca rbon monox ide and hyd rogen (a l so

r e fe r red t o as syn thes i s gas ) i s p roduced . The coa rse ( see

f i gu re 4 .4 ) ash i s f o rmed a t t hese e l eva ted t empe ra tu res and

p ressu re by t he i n te rac t i on o f i ne r t m ine ra l s p resen t i n t he coa l

and s tone . The coa rse ash i s r emoved f r om the gas i f i e r and

d i sposed as a by -p roduc t (Van Dyk , 2005 ) .

F i gu re 4 .4 Samp le o f gas i f i ca t i on ash c l i nke r

4 .3 .1 Pa r t i c le s i ze d is t r ibu t ion

Lase r t echno logy i s us ed t o i nves t i ga te t he pa r t i c l e s i ze

d i s t r i bu t i on o f ma te r i a l s a f t e r g r i nd i ng .

4 . 3 .1 .1 Pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

By p l o t t i ng t he i nve rse o f t he cumu la t i ve pe rcen tage

d i s t r i bu t i on , t he cumu la t i ve % ove rs i ze pa r t i c l e d i s t r i bu t i on i s

ob ta i ned . P rov i s i on was made f o r s t a t i s t i ca l ou t l i e r s by no t


4-5

tak i ng t he f i ve p e rcen t sma l l es t d i ame te r s and f i ve pe rce n t

l a rges t d i ame te r s i n t o accoun t .

Fo r each samp le a t r end l i ne i s added t o t he cumu la t i ve %

ove rs i ze g raph ( see f i gu re 4 .5 ) .

y = 0.9452e-0.0507x

R2 = 0.9978

0%10%20%30%40%50%60%70%80%90%

100%

0 20 40 60

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,2hrExpon. (GA,2hr)

F igu re 4 .5 Expon en t i a l f i t f o r cumu la t i ve % ove rs i ze pa r t i c l e

s i ze d i s t r i bu t i on

4 .3 .1 .2 Ros in -Rammle r pa r t i c l e s i ze d i s t r i bu t i on pa rame te rs

The cumu la t i ve % ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on as

d i scussed i n 4 .3 .1 .1 can be rep resen ted as a Ros in -Ramml e r

d i s t r i bu t i on .

The Ros in -Ramml e r d i s t r i bu t i on g raphs (F igu re 4 .6 and F igu re

4 .7 ) a re examp le s o f how the va lues f o r t he pa r t i c l e s i ze

d i s t r i bu t i on pa rame te rs we re de r i ved . The mod i f i ed Ros in -

Rammle r d i s t r i bu t i on g raph l n l n (1 / y ) ve rsus l nx i s p l o t t ed , w i t h

y t he f i t t ed f unc t i ons y = a exp (b x ) f o r t he cumu la t i ve %

ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on and x t he pa r t i c l e s i ze . A

l i nea r t r end l i ne and equa t i on i s a l so added to t hese g raphs

( see f i gu re 4 .6 ) . The s l ope and i n te r cep t i on w i t h t he ho r i zon ta l

ax i s o f t he l i ne i s t aken as t he n va lue and l n X o va lue o f t he

mod i f i ed Ros in -Rammle r f u nc t i on respec t i ve l y .


4-6

y = 0.9665x - 2.8296R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5

ln (Particle size(μm))

ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,2hrLinear (GA,2hr)

F igu re 4 .6 Ros in -Rammle r d i s t r i bu t i on g raph

Slope (n) = 0.9665 Ln Xo = 2.952

Position parameter Xo = 19.14 μm

W i th t h i s ana l ys i s 36 .8% o f t he pa r t i c l es (pe r mass ) a re g rea te r

t han t he X o va lue (pos i t i on pa rame te r i n μm) . Th i s pa rame te r i s

an i nd i ca to r o f t he pa r t i c l e s i ze . The n - va lue rep resen ts t he

range o f t he pa r t i c l e s i ze d i s t r i bu t i on o f t he pa r t i c l e s i zes

g rea te r t han X o ( see f i gu re 4 .7 ) .

0%10%20%30%40%50%60%70%80%90%

100%

0 10 20 30 40 50 60

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

(n) Slope indicates the range of the particle sizes greater than Xo

36.8%

Xo

F i gu re 4 .7 Exp lana t i on o f Ros in -Rammle r d i s t r i bu t i on

pa rame te rs


4-7

4 .3 .1 .3 Pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

The co r respond ing 50% ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on i n

μm can be read f rom the exponen t i a l f i t g raph (See f i gu re 4 .8 ) .

Th i s pa r t i c l e s i ze g i ves an i nd i ca t i on o f t he ave rage pa r t i c l e

s i ze o f each samp le . I n t he same way t he 10% ove rs i ze pa r t i c l e

s i ze (D10 ) , wh i ch shows the d i f f e rence i n number o f l a rge r

pa r t i c l es i n each samp le .

y = 0.9452e-0.0507x

R2 = 0.9978

0%10%20%30%40%50%60%70%80%90%

100%

0 10 20 30 40 50 60Particle size (μm)

Cum

ulat

ive

% o

vers

ize


D50 D10

F igu re 4 .8 Cumu la t i ve % ove rs i ze d i s t r i bu t i on pa rame te rs

F igu re 4 .9 i nd i ca tes t he 3 µm and the 30µm ove rs i ze pa r t i c l e s i ze

d i s t r i bu t i ons . Th i s pa r t i c l e s i ze can g i ve an i nd i ca t i on o f t he % o f t he

pa r t i c l e wh i ch l i es i n t he <3µm a nd 3 -30µm in te r va l s , wh i ch can

co r respond to t he va lues cemen t man u fac tu re r ’ s cu r ren t l y use t o l im i t

t he f i neness o f cemen t .


4-8

y = 0.9452e-0.0507x

R2 = 0.9978

0%10%20%30%40%50%60%70%80%90%

100%

0 10 20 30 40 50 60Particle size (μm)

Cum

ulat

ive

% o

vers

ize


3 µm

F igu re 4 .9 Cumu la t i ve % ove rs i ze i n te r va l s f o r 3µm and 30µm

4 .3 .2 Spec i f i c sur face a rea

A s tanda rd me thod o f de te rm in ing t he spec i f i c su r face a rea o f

cemen t wh i ch i s based on t he res i s tance t o a i r f l ow th rough a

compac t o f cemen t and was deve loped by B la ine . F igu re 4 .10

shows the appa ra tus used t o de te rm ine spec i f i c su r f ace a rea .

A cons tan t vo lume me thod whe re t he t ime , t , r equ i red t o pass a

f i xed vo lume o f a i r t h rough a compac t bed o f cemen t (12 .7 mm

d iame te r and 15 mm in dep th ) , o f s tanda rd po ros i t y i s r e l a ted

t o t he spec i f i c su r f ace o f cemen t by t he f o l l ow ing re l a t i onsh ip :

S w = K√ t ( equa t i on 4 .1 )

Where K= 281 .3915 ( cons tan t f o r appa ra tus )


4-9

F igu re 4 .10 Appa ra tus t o de te rm ine spec i f i c su r face a rea

4 . 3 .3 Scann ing e lec t ron mic roscop y (SEM)

A H i t ach i X -650 Scann ing E lec t ron M ic roana l yze r was used t o

t ake t he m ic rog raphs o f t he samp les . Samp les we re moun ted

on a lum in ium s tubs us ing conduc t i ve g lue and we re t hen

coa ted w i t h a t h i n l aye r o f go ld .

4 .3 .4 X - ra y f luorescence spec t roscop y (XRF)

An XRF Spec t rome te r was used to i nves t i ga te t he

cha rac te r i s t i c spec t ra o f e l emen ts p resen t i n t he so l i d samp le .

Fo r quan t i f i ca t i on ana l ys i s , t he i n tens i t y o f cha rac te r i s t i c l i ne

o f t he e lemen t ana l ysed was measu red .

The coa rse so l i d samp le was i n i t i a l l y g round to a pa r t i c l e s i ze

o f 100% <200µm. The powdered samp le was ca l c i ned a t 850 ºC

fo r 4 hou rs i n o rde r t o remo ve a l l o rgan i c compounds and wa te r

con ta ined i n t he samp le . The ca l c i ned samp le was conve r ted


4-10

in to a so l i d so lu t i on by f us ion w i t h l i t h i um te t ra bo ra te

(L i 2 B 4 O 7 ) . The p repa red so l i d so lu t i on and s tandard we re

p laced i n samp le ho lde rs and p laced i n t he samp le

compar tmen t o f t he XRF spec t rome te r . The i n tens i t y o f a

cha rac te r i s t i c l i ne o f t he e lemen t t o be de te rm ined was

measu red . The concen t ra t i on o f t he e lemen t i n t he samp le was

ca l cu la ted f r om the i n tens i t y measu r ed .

4 .3 .5 X - ra y d i f f rac t ion spec t roscop y (XRD)

A l l t he samp les we re rece i ved as d ry , f i ne powder . A mass o f

app rox ima te l y 4g o f each samp le , we re f u r t he r g round and

homogen i sed by hand i n an aga te mor ta r .

The add i t i ona l g r i nd ing , as requ i red f o r a quan t i t a t i ve XRD

ana l ys i s , was done us ing t he aga te segmen ts i n a McCrone

m ic ron i s ing m i l l ove r 10 m inu tes . Th i s f i ne g r i nd ing f o l l owed by

sp i k i ng t he samp les w i t h 10% (by mass ) Ca F 2 as an i n te rna l

s tanda rd , was re qu i red t o conduc t t he quan t i t a t i ve XRD

ana l yses .

App rox ima te l y 0 .5g o f t he g round samp le was p laced i n a

s ta i n l ess s tee l samp le ho lde r and exposed to t he X- ray beam

to gene ra te t he samp le ’ s d i f f r ac t i on pa t t e rn .

4 .4 STAND A RD TEST S FOR C EME NTIT IOUS MA TERIALS

F l y ash comp ly i ng w i t h t he requ i remen ts o f t he Sou th A f r i can

s tanda rd spec i f i ca t i on f o r Po r t l and cemen t ex tende rs (SANS

1491 -2 :2005 / SABS 1491 -2 :2005 ) con fo rms to t he f o l l ow ing

t es t s :

Su lphu r t r i ox i de con ten t

Loss on i gn i t i on

F ree wa te r con ten t

F ineness

Wa te r r equ i remen t


4-11

S t reng th Fac to r

Soundness

4 .4 .1 Su lphur t r iox ide con ten t (SANS 50 196 -2 :1994 / SABS EN 196 -2 :1994 )

1 g o f t he samp le i s we ighed ; 90m ℓ o f wa te r and 10 m ℓ o f HC I

i s added wh i l e s t i r r i ng v i go rous l y . The so lu t i on i s hea ted and

l e f t t o d i ges t j us t be low bo i l i ng po in t f o r 15 m inu tes . The

so lu t i on i s f i l t e red and washed whe re a f t e r t he so lu t i on i s

hea ted wh i l e BaC l 2 . 2H 2 O i s added to t he so lu t i on . The so lu t i on

i s d i ges ted f o r 12 hou rs and t hen f i l t e red and washed . Pape r

i s p l aced i n c ruc ib l e and p rec ip i t a te i s i gn i t ed t o cons tan t mass

a t 300°C . The su lpha te con ten t i s now de te rm ined f o r t he

samp le .

SO 3 content = (a - b ) x 34 .3 ( equa t i on 4 .2 )

c where :

a = mass o f ba r i um su lpha te f ound (g )

b = mass o f ba r i um su lpha te f ound i n b l ank de te rm ina t i on (g )

c = mass o f samp le t aken (g )

4 .4 .2 Loss on ign i t ion (SANS 5 0196 -2 :1994 / SABS EN 19 6 -2 :1994 )

We igh abou t 1g o f samp le i n to c ruc ib l e and i gn i t e a t 850°C fo r

15 m inu tes . A l l ow coo l i ng i n des i cca to r and asce r ta i n i ng

whe the r cons tan t mass i s ob ta ined by we i gh ing t he samp le .

De te rm in e t he LOI .

LOI % = (a - b ) x 100 ( equa t i on 4 .3 )

a

where :

a = mass o f samp le t aken (g )

b = mass o f r es idue (g )


4-12

4 .4 .3 F ree w a te r con ten t (SANS 6151 :1989 / SABS 1151 :1989 )

We igh abou t 1g o f samp le i n to c ruc ib l e and d ry t he sa mp le f o r

1 hou r i n oven a t 100°C to a cons tan t mass . A l l ow coo l i ng i n

des i cca to r and de te rm in ing t he mass o f t he d ry samp le .

Free water content % = (a - b ) x 100 ( equa t i on 4 .4 )

b where :

a = mass o f samp le (g )

b = mass o f d r i ed samp le (g )

4 .4 .4 Tes t fo r f ineness o f cement and Por t l and cement ex tenders (SANS 6 157 :2002 / SABS 1157 :2002 )

A mass o f 1 g o f t he samp le i s t aken a f t e r be ing d r i ed i n an

oven and p laced on a 45μm s ieve . The samp le i s washed w i t h

t he use o f a nozz le sp ray ing wa te r unde r a p ressu re o f 70 -

80kPa . Remo ve t he s i eve f r om und e r t he no zz le and d ry t he

s i eve w i t h t he res idue i n an oven . De te rm in e t he mass o f t he

s i eve and res idue .

Fineness, % (m/m) = c – b x 100 ( equa t i on 4 .5 )

a where :

a = d r i ed mass o f spec imen (g )

b = mass o f s i eve (g )

c = mass o f s i eve p lus res idue (g )

4 .4 .5 Wate r re qu i rement (SANS 6156 :1989 / SABS SM 115 6 :1989 )

The mor ta r was m ixed acco rd ing t o SABS Me thod 866 and the

f l ow tes t was pe r fo rmed o n t he samp le . The m ix compos i t i on

f o r mor ta r p r i sms i s seen i n Tab le 4 .1 .


4-13

Tab le 4 .1 M ix compos i t i on f o r mor ta r p r i sms

Mater ia l Quant i ty

Wate r 225 g

Cemen t 450 g

S tanda rd re fe rence sand 1350 g

I n t h i s p ro jec t 35% o f t he cemen t wa s rep laced w i t h

gas i f i ca t i on ash as can be seen i n Tab le 4 .2 .

Tab le 4 .2 M ix compos i t i on used i n t es t

Mater ia l Quant i ty

Wate r 225 g

Gas i f i ca t i on Ash 140 g

Cemen t 310 g

S tanda rd re fe rence sand 1350 g

The f l ow tab le i s d r i ed and t he mou ld i s p l aced i n t he cen t re .

The mou ld i s ha l f - f i l l ed w i t h a l aye r o f mor ta r ( 25 mm) and

t amped 20 t imes w i t h a t amper . The mou ld i s f i l l ed and aga in

t amped 20 t imes . Excess mor ta r i s cu t o f f and mou ld i s l i f t

ve r t i ca l l y . I n a pe r i od o f 25 seconds , t he t ab le i s r a i sed and

d ropped 25 t imes t h rough a he igh t o f 12 .7 mm. A pho to o f t he

f l ow tab le t es t can be seen i n F igu re 4 .11 .


4-14

F igu re 4 .11 Pho to o f samp le on f l ow tab le a f t e r mou ld i s

r emoved

The d iame te r o f t he mor ta r i s measu red a t f ou r app rox ima te l y

equa l - spaced i n te r va l s . The ave rage d iame te r i s ca l cu la ted and

t aken as t he f l ow . The i nc rease i n d i ame te r i s exp ressed as a

pe rcen tage o f t he o r i g i na l nom ina l d i ame te r o f t he l owe r pa r t o f

t he mor ta r spec imen (100 mm) . The d iame te r measu re men ts on

t he f l ow tab le can be seen i n t he pho to i n F igu re 4 .12 .

Ca l cu la te t o t he nea res t 1% the wa te r r equ i remen t o f t he

ma te r i a l as f o l l ows :

Water requi rement = Wt x 100 ( equa t i on 4 .6 )

Wr where :

Wt = mass o f wa te r t o p roduce f l ow va lue o f t he mor ta r t o

w i t h i n 5% po in t s o f t he re fe rence m ix (g )

Wr = ac tua l mass o f wa te r used i n re fe rence m ix (g )


4-15

F igu re 4 .12 Pho to o f d i ame te r measu remen ts o f f l ow tab le t es t

4 .4 .6 S t reng th fac to r t es t (SANS 50196 -1 :1994 / SABS EN 196 -1 :1994 )

The s t reng th o f cemen t can be de te rm ined by cas t i ng mor ta r

p r i sms . The spec i f i ca t i on p resc r i bes a s tanda rd m ix

compos i t i on as i nd i ca ted i n Tab le 4 .1 . The mo r ta r compos i t i on

f o r t he s t reng th t es t was as i nd i ca ted i n Tab le 4 .2 . Mor ta r was

m ixed acco rd ing t o SABS Me thod 866 . The tes t spec imens a re

40 mm x 40 mm x 160 mm p r i sms as seen i n F i gu re 4 .13 .

F i gu re 4 .13 Pho to o f mou ld used


4-16

The spec imens a re mou lde d a f t e r m ix i ng o f t he mor ta r . Mou lds

a re f i l l ed w i t h t he f i r s t o f two l aye rs o f mo r ta r , sp read equa l l y

i n each mou ld compar tmen t and t hen compac ted w i t h t he

v i b ra t i ng t ab le f o r 20 seconds . A f t e r compa c t i ng t he second

l aye r , t he su r face o f t he spec imen i s l eve l l ed and t he spec imen

a re cove red w i t h p l as t i c and p laced i n a cons tan t t empera tu re

room a t 22°C and 55% re la t i ve hum id i t y (RH) ove rn igh t .

Mo r ta r p r i sms a re cas t as f o r t he s t reng th f ac to r t es t ( see 4 .4 .6

s t reng th f ac to r t es t ) and t he f l ow tab le t es t ( see 4 .4 .5 ) i s

conduc ted on each d i f f e ren t mor ta r m ix . Ea ch ba tch o f mor ta r

i s m ixed mechan i ca l l y us ing a m ixe r . Ma te r i a l s a re added i n to

t he m ix i n g bow l and m ixed f o r a cons tan t t ime o f 30 seconds

whe re a f t e r t he wa te r i s added and m ixe d f o r a f u r t he r 90

seconds . Samp les a re cas t i n se t s o f t h ree p r i sms to ob ta in

s t reng ths on 2 , 7 , 28 days t o s tudy t he s t reng th deve lopmen t

ove r a l ong pe r i od .

Spec imens a re demou lded a f t e r 24 hou rs and p laced i n wa te r

a t 25 ˚C fo r cu r i ng .

F i r s t l y t he f l exu ra l s t r eng th i s de te rm i ned . P r i sms a re

suppo r ted on suppo r t s 100 mm apa r t and l oaded w i t h a po in t

l oad a t m idspan .

The f l exu ra l s t r eng th i s ca l cu la ted as f o l l ows :

R f = 1 .5 x F f x l ( equa t i on 4 .7 ) b 3

where :

R f = f l exu ra l s t r eng th (MPa)

F f = l oad app l i ed t o t he m idd le o f t he p r i sms ( kN)

l = d i s tance be tween the suppo r t s (mm)

b = s i de o f t he squa re sec t i on o f t he p r i sm (mm)

The same p r i sms tes ted i n t he f l exu ra l t es t a re t es ted f o r

compress i ve s t reng th . The two ha l ves o f each p r i sm a re t es ted


4-17

in t he p ress and t he ave r age o f t he s i x r esu l t s ob ta ined i s

t aken as t he compress i ve s t reng th . The compress i ve s t reng th

o f a p r i sm i s ca l cu la ted as f o l l ows :

R c = F c ( equa t i on 4 .8 )

1600

whe re :

R c = compress i ve s t reng th (MPa)

F c = ma x imum load a t f r ac tu re (N )

1600 = 40 mm x 4 0 mm, a r ea o f t he p la tens (mm)

4 .4 .7 Soundness (SANS 50196 -3 :1994 / SABS EN 196 -3 :1994 )

The pu rpose o f t h i s t es t i s t o de te rm ine t he r i s k o f expans ion

due t o hyd ra t i on . P repa re a cemen t pa s te o f s tanda rd

cons i s tency and f i l l a l i gh t l y o i l ed Le Cha te l i e r mou ld , us ing

on l y t he hands and no t v i b ra t i on . P lace t he appa ra tus i n a

hum id i t y ( 98%) cab ine t f o r 24 hou rs a t 20 °C . F igu re 4 .14

shows the Le Cha te l i e r appa ra tus i n a wa te r b a th i n a hum id i t y

cab ine t . Measu re t he d i s tance be tween the i nd i ca to r po in t s .

F i gu re 4 .14 Le Cha te l i e r mou lds i n hum id i t y cab ine t


4-18

Hea t mo u ld f o r 30 m inu tes and ma in ta in t he wa te r -ba th a t

bo i l i ng t empera tu re f o r t h ree hou rs . Mea su re t he d i s tance

be tween the i nd i ca to r po in t s and a l l ow mou ld t o coo l t o 20°C .

Measu re d i s tance be tween i nd i ca to r po in t s .

Soundness = c – a ( equa t i on 4 .9 )

whe re :

a = measu remen t a f t e r 24 hou rs i n hum id i t y cab ine t (mm)

c = measu remen t a f t e r coo l i ng spec imen to 20°C (mm)

4 .4 .8 Re la t i ve dens i ty (LSA Method)

The re la t i ve dens i t y o f t he samp le i s de te rm ined by :

Relat ive densi ty = c ( equa t i on 4 .10 )

(c + e ) - d where :

c = mass o f samp le (g )

d = mass o f f l ask and samp le and wa te r ( g )

e = mass o f pyknomete r and wa te r ( g )

4 .5 FACTOR S INVES T IGATE D BY CA S T ING MORTAR P R ISMS

4 .5 .1 D i f f e ren t Gr ind in g T imes

Mo r ta r p r i sms we re cas t f o r t he d i f f e ren t g r i nd ing t ime i n te r va l s

w i t h a cons tan t r ep lacemen t o f cemen t w i t h gas i f i ca t i on ash o f

35%. Mor ta r p r i sms we re wa te r cu red and compress i ve and

f l exu ra l s t r eng ths we re de te rm ined a f t e r 2 , 7 and 28 days . The

m ix comp os i t i on f o r bo th i n te rb lend ing cemen t and gas i f i ca t i on

ash a f t e r g r i nd ing each ma te r i a l sepa ra te l y , and i n te rg r i nd ing


4-19

o f cemen t and gas i f i ca t i on ash by i n te rb lend ing t he two

ma te r i a l s i n t he ba l l m i l l and g r i nd ing i t t oge the r i s seen i n

Tab le 4 .3 and Tab le 4 .4 . The gypsum con ten t was cons tan t a t

2 .5% rep lacemen t o f t he cemen t con ten t .

Tab le 4 .3 Mor ta r p r i sm m ix co mpos i t i on f o r i n te rb lend ing

cemen t and Gas i f i ca t i on ash

Material Mass (g) Cement 292.5 Gasification ash 157.5 Gypsum 7.31 Water 225 Standard reference sand 1350

Tab le 4 .4 Mor ta r p r i sm m ix compos i t i on f o r i n te rg r i nd ing

cemen t and Gas i f i ca t i on ash

Material Mass (g)

Cement and Gasification ash interground 450

Gypsum 7.31

Water 225

Standard reference sand 1350

4 .5 .2 D i f f e ren t Gypsum Percen tages

Mo r ta r p r i sms we re cas t f o r i n t he ba l l m i l l t o t es t t he e f f ec t o f

d i f f e ren t gypsum pe rcen tages and t o es tab l i sh t he d i f f e rence

be tween the l abo ra to ry i n te rb lended and i n te rg round cemen ts

w i t h a commerc ia l l y ava i l ab le CEM I 42 .5 . Tab le 4 .5 shows the

d i f f e ren t we igh t s f o r gypsum as a pe rcen tage o f t he cemen t

con ten t .


4-20

Tab le 4 .5 Gypsum rep lacemen t we igh t s f o r mor ta r p r i sms

Gypsum replacement %

Gypsum content (g)

0.0% 0.00 0.5% 1.46 1.0% 2.93 1.5% 4.39 2.0% 5.85 2.5% 7.31 3.0% 8.78

4 . 5 .3 I so therma l Conduc t ion Ca lo r imet ry

I n i so the rma l conduc t i on ca lo r ime t r y , t he hea t o f hyd ra t i on o f

cemen t i s d i r ec t l y measu red by mon i t o r i ng t he hea t f l ow f rom

the spec imen when bo th t he spec imen and the su r round ing

env i ronmen t a re ma in ta ined a t app rox ima te l y i so the rma l

cond i t i ons . App rox ima te l y 3g o f wa te r we re i nocu la ted i n to an

equ i va len t mass o f r eac tan t powder t ha t had been p laced i n a

coppe r samp le cup and p laced w i t h i n t he ca lo r ime t r y cav i t y .

The cups we re se a led w i t h p l as t i c f i lm t o m in im ize eva po ra t i on

o f wa te r . Each reac tan t was a l l owed to equ i l i b ra te sepa ra te l y

t o 25 ºC , p r i o r t o m i x i ng . The wa te r was equ i l i b ra ted i n a

sy r i nge and when equ i l i b r i um had been ach ieved the p las t i c

f i lm was pene t ra ted and t he wa te r i n j ec ted ove r t he so l i ds . The

ra tes o f hea t evo lu t i on , dQ/d t i n mW/g we re measu red and

reco rded us ing a compu te r da ta acqu i s i t i on sys tem.

The hea t o f hyd ra t i on o f a mor ta r m ix was a l so i nves t i ga ted .

Mor ta r m ixes we re m ixe d and cas t i n to a s tee l cy l i nde r .

The rmocoup les we re i nse r ted i n to t he pocke t o f t he s tee l

cy l i nde rs ’ l i d . The cy l i nde r and t he rmocoup le we re p laced i n to

a t empera tu re i so la t i on f l ask and l e f t i n a cons tan t t empera tu re

room a t 25 ºC .

The t he rmocoup les reco rded the t empera tu re o f t he mor ta r ove r

112 hou rs . A f t e rwa rds t he t he rmocoup les we re removed and

t he da ta we re down loaded w i t h a compu te r sys tem.


4-21

4 .5 .3 D i f f e ren t rep lacements percen tages o f Gas i f i ca t ion Ash

Mor ta r p r i sms we re cas t f o r d i f f e ren t r ep lacemen t pe r cen tages

o f Gas i f i ca t i on ash . Gas i f i ca t i on ash we re rep laced i n t he ba l l

m i l l and g rounded w i t h cemen t . These rep lacemen t pe rcen tages

we re : 0%, 10%, 20%, 35% and 55%. The rep lacemen t

pe rcen tages we re se lec ted as t he h ighes t i n te r va l cu r ren t l y

used i n commerc ia l l y ava i l ab le CEM I ( 0%) , CEM I I ( 6 - 10% and

21 -35%) and CEM IV (36 -55%) .


5-1

5. EXPERIMENTAL PROGRAMME AND TEST PROCEDURES FOR CONCRETE

5 . 1 INTRODUCTION

The a im o f t h i s s tudy i s t o de te rm in e whe the r gas i f i ca t i on ash

can be used as a cemen t ex tende r i n conc re te . Cu r ren t l y

pu l ve r i sed f ue l ash (a l so ca l l ed f l y ash ) i s w ide l y used as a

cemen t ex tende r i n conc re te and t he e f f ec t o f t h i s t ype o f ash

i s we l l es tab l i shed . I n t h i s s t udy t he p rope r t i es o f cemen t and

conc re te con ta i n ing gas i f i ca t i on ash w i l l be compa red t o t he

p rope r t i es o f cemen t and conc re te con ta i n i ng f l y ash .

The a im o f t h i s chap te r i s t o d i scuss t he t es t i ng me thods used

i n t he p rac t i ca l ana l ys i s o f t he r eac t i v i t y o f a gas i f i ca t i on ash .

The m ix des ign f o r d i f f e ren t m i xes o f conc re te w i l l be

d i scussed . The t es t i ng o f conc re te cubes , c y l i nde rs and

sh r i nkage beams w i l l be d i scussed w i t h r e fe rence t o t he t es t i ng

appa ra tus , as we l l as t he s tanda rd i sed t es t i ng me thods used .

5 .2 M IX DESI GN FOR CONCRE TE MIXE S

Conc re te was ba t ched f o r t h ree d i f f e ren t m i xes t o i nves t i ga te

cube s t r eng ths , t ens i l e s t r eng ths , E - va lues , sh r i nkage , c reep ,

po ros i t y and pe rmeab i l i t y .

Each m ix ( see Tab le 5 .1 ) had a wa te r / cemen t r a t i o o f 0 . 6 . The

agg rega te con ten t was ma de up o f do l om i t e sand and 1 /3 o f

9 . 5mm a nd 2 /3 19mm g ra n i t e s t one . A 35% subs t i t u t i on o f

cemen t i t i ous ma te r i a l s was cons ide red whe re app l i cab le f o r t he

m i xes . Th e s i ze o f t he m i xes was 43 ℓ .


5-2

Tab le 5 .1 M i x compos i t i on fo r conc re te m i xes

Mater ia ls Quant i t y 43ℓ Pe r kg /m³

Wate r 9 ℓ 210 ℓ

Cement 9 .8 kg 227 kg

Cement i t ious mate r ia l 5 . 3 kg 123 kg

Do lomi te Sand 37 .7 kg 875 kg

9 .5mm Gran i te S tone 14 .2 kg 330 kg

19mm Gran i te S tone 28 .4 kg 660 kg

The m ix compos i t i on r ema ined cons tan t and on l y t he t ype o f

cemen t i t i ous ma te r i a l used was changed . The cemen t used i n

t he m i xes can be seen i n Tab le 5 .2 .

Tab le 5 .2 Conc re te m i x compos i t i on

Mix Descr ip t ion Abbrev ia t ion

Mix 1 In te rg r in d ing o f cement and gas i f i ca t ion ash IG

M ix 2 In te rb lend ing o f cement and gas i f i ca t ion ash IB GA

Mix 3 In te rb lend ing o f cement and f l y ash IB FA

5 .3 TEST CONDUCTE D ON F R ESH CONCRETE MIXES

5 .3 .1 S lump Tes t (SANS 586 / SABS SM 82 :1994 )

The s l ump t es t i s a me thod t o meas u re t he cons i s t ency o f t h e

conc re te . I t does howeve r no t t es t a l l t he cons i s t ency

r equ i r emen ts and has a l im i t ed app l i ca t i on .

I n t he s l ump t es t t he mo u ld i s f i l l ed i n t h ree equa l l a ye rs ,

sub jec t i ng each l aye r t o 25 b l ows f r om the tamp ing rod wh i l e

t he mou ld i s f i rm l y he ld down by s tand ing on t he f oo t p i eces .

The su r f ace i s smoo thed , t he cone i s r emo ved and t he s l ump i s

measu red t o t he nea res t 5 mm. The s l ump i s t he d i s t ance


5-3

be tween t he t op o f t he i nve r t ed mou ld and t he h i ghes t po in t o f

t he conc re te as i nd i ca ted i n F i gu re 5 .1 .

F i gu re 5 .1 Measu r i ng t he s l ump (Add i s , 2001 )

5 .4 STRENGTH TEST S

5 .4 .1 Compres s ive S t reng th Tes t (SANS 5863 -1 /SABS 863 -1994 )

Tes t spec imens a re c rushed be tween two p l a tens i n a hyd rau l i c

p ress . The ra te o f l oad app l i ca t i on i n f l uences t he compress i ve

s t r eng th r esu l t s and i s spec i f i ed a t a un i f o rm ra te o f 0 . 3 MPa /s

± 0 .1 MPa /s .

A l l t he cubes we re wa te r cu red . Th ree cubes (100x100x100 )

f r om each m ix we re c rushed on 2 , 7 and 28 days and t he

ave rage o f t he t h ree cube s t r eng ths was de f i ned as the

s t r eng th . The compress i ve s t r eng th i s r eco rded t o t he nea res t

0 .5MPa .


5-4

5 .4 .2 Sp l i t t ing Cy l inder Tes t fo r Tens i l e S t reng th (SANS 625 :1994 /SABS SM 1253 :1994 )

I n Sou th A f r i ca t he t ens i l e s t r eng th o f conc re te i s de te rm ined

i nd i r ec t l y by b reak ing beam spec imens i n f l e xu re o r by sp l i t t i ng

cy l i nde rs by app l y i ng l i ne l oads .

The cy l i nde r i s p l aced w i th i t s ax i s ho r i zon ta l be tween t he

p l a tens o f t he t es t i ng mach ine , and t he l oad i s i nc reased un t i l

f a i l u re occu rs by i nd i r ec t t ens i on i n t he f o rm o f sp l i t t i ng a l ong

t he ve r t i ca l p l ane t akes p l ace . Fo r each m ix , two cy l i nd r i ca l

samp les we re sp l i t .

The f o l l ow ing equa t i on was app l i ed t o de te rm ine t he t ens i l e

s t r eng th o f t he conc re te acco rd i ng to t he e l as t i c t heo ry :

f = 2 x P ( equa t i on 5 .1 )

πdℓ

whe re :

f = t ens i l e s t r eng th (MPa)

P = compress ion l oad a t f a i l u re (N )

d = d i ame te r o f c y l i nde r (mm)

ℓ = l eng th o f c y l i nde r (mm)

A l l t he cy l i nde rs we re wa te r cu red and two cy l i nde rs f r om each

m ix we re used t o de te rm ine t he t ens i l e s t r eng th .

5 .5 DEFORMATION A ND V OLU ME C HA NGE OF CON CRE TE

5 .5 .1 E -Va lue Tes t

De fo rma t i on t akes p l ace when a l oad i s app l i ed t o a s t r uc tu ra l

ma te r i a l . I f t he r a t i o o f t he app l i ed compress i ve s t r eng th t o t he

l ong i t ud i na l s t r a i n p roduced i s cons tan t , t he cons tan t i s ca l l ed

t he modu lus o f e l as t i c i t y (Young ’ s modu lus ) .


5-5

The non - l i nea r i t y o f t he s t ress - s t r a i n r e l a t i onsh ip f o r conc re te

i s ma in l y due t o t he non - l i nea r s t r ess - s t r a i n r esponse o f t he

pas te . A po r t i on o f t he cu r ve may be rega rded as be ing

e f f ec t i ve l y l i nea r , and a t s t r esses w i t h i n t h i s r ange t he e l as t i c

modu lus may be t aken as t he s l ope o f t he l i nea r po r t i on . Fo r

t h i s po r t i on Hooke ’ s l aw may be used t o de te rm ine t he modu lus

o f e l as t i c i t y .

The re i s no SABS tes t me thod t o de te rm ine t he s ta t i c e l as t i c

modu lus o f conc re te and t he re fo re ASTM C 4 69 -02 i s used . The

t es t s de te rm ine i n i t i a l t angen t mod u lus (Young ’ s ) as we l l as

t he secan t modu lus co r respond ing t o one t h i r d o f t he

compress i ve f a i l u re s t r ess . The t es t i n vo l ves l oad ing a cy l i nde r

a t a cons tan t r a t e and reco rd i ng t he l oad ( s t r ess ) and

de fo rma t i on ( s t r a i n ) o f t he spec imen . A s t r ess - s t r a i n cu r ve i s

de te rm ined f r om wh i ch t he modu lus o f e l as t i c i t y i s de te rm ined .

The modu lus o f e l as t i c i t y was de te rm ined as f o l l ows :

∆L = G L – G F ( equa t i on 5 .2 )

2

ε = ∆L ( equa t i on 5 .3 )

L

P = (P L – P F ) x 1000 ( equa t i on 5 .4 )

A = πd 2 ( equa t i on 5 .5 )

4

σ = P ( equa t i on 5 .6 )

A

E = σ ( equa t i on 5 .7 )

ε


5-6

whe re :

G L = Las t r ead ing o f gauge (µm)

G f = F i r s t r ead ing o f gauge (µm)

L = d i s t ance be tween measu r i ng po in t s (mm)

P L = l as t s t r eng th i n t e r va l ( kN )

P F = f i r s t s t r eng th i n t e r va l ( kN )

d = d i ame te r o f c y l i nde r (mm)

E = s ta t i c modu lus o f e l as t i c i t y (GPa)

Cy l i nde rs we re wa te r cu red f o r 28 days . Fo r t he de te rm ina t i on

o f t he modu lus o f e l as t i c i t y , two cy l i nde rs o f each m ix we re

t es ted a f t e r t he 28 -day compress i ve r esu l t s o f t he cubes we re

de te rm ined .

5 .5 .2 Shr inkage and Creep Tes t (ASTM C 512 -02 )

Vo lume change occu rs i n conc re te i n bo th t he f r esh and

ha rdened s ta te . S t r uc tu ra l pe r f o rma nce i s mos t conce rned by

t he vo l ume change assoc ia ted w i t h an i n t e r change o f mo i s tu re

be tween ha rdened conc re te and t he env i r onmen t .

Swe l l i ng occu rs when t he ne t f l ow o f mo i s tu re f r om the

env i r onmen t t o t he conc re te cause a vo l ume i nc rease and

sh r i nkage occu rs when a n e t ou t f l ow f r om t he conc re te t o t he

env i r onmen t r esu l t s i n a dec rease i n vo l ume . Con ven t i ona l

conc re te usua l l y con ta i ns mo re wa te r t han wha t can be

chem ica l l y comb ined w i t h t he cemen t and t he re i s a t endency

f o r mo i s tu re t o be l os t f r om the conc re te , r esu l t i ng i n

sh r i nkage .

C reep i s de f i ned as t he i nc rease i n s t r a i n ( de fo rma t i on ) unde r

a sus ta i ned s t r ess ( l oad ) . When l oaded , conc re te expe r i ences

an i ns tan taneous e l as t i c s t r a i n , wh i ch i s r ecove rab le . I n

add i t i on , an i ne l as t i c c reep s t r a i n t akes p l ace t ha t i s on l y

pa r t i a l l y r ecove rab le .


5-7

Sh r i nkage i s t es ted i n con junc t i on w i t h c reep . Th ree cy l i nde rs

we re cas t and cu red i n wa te r f o r 28 days . Fo r t he t es t , one

cy l i nde r i s used f o r sh r i nkage and two cy l i nde rs fo r c reep

t es t i ng . The sh r i nkage t es t i s a na tu ra l d ry i ng me thod whe re

t he cy l i nde r i s d r i ed i n a con t ro l l ed env i r onmen t o f 65±5%

re l a t i ve hum id i t y and 22 ±2 ºC . Th e sh r i nkage mo vemen t i s

measu red ove r a pe r i od o f t ime .

The t es t me thod f o r c reep measu res t he l oad - i nduced t ime

dependen t compress i ve s t ra i n a t se l ec ted ages f o r conc re te .

The cube compress i ve s t r eng ths o f t he d i f f e ren t m i xes a re

de te rm ined on 28 days . The cy l i nd r i ca l samp les a re p l aced i n t o

a l oad ing f r ame a nd l oaded w i t h 40% o f t he compress i ve l oad .

S t ra i n r ead ings a re t aken immed ia te l y be fo re and a f t e r l oad ing ,

and t he rea f t e r a t r egu la r t ime i n t e r va l s .


5-8

F i gu re 5 .2 Pho to o f l ab se t - up f o r measu r i ng sh r i nkage and

c reep

5 .6 DUR ABIL ITY

Durab i l i t y can be de f i ned as , “ t he capab i l i t y o f ma in ta i n i ng t he

se r v i ceab i l i t y o f a p roduc t , componen t assemb ly o r cons t ruc t i on

ove r a spec i f i ed t ime ” .

The qua l i t y o f conc re te canno t be de te rm ined by on l y u s i ng t he

s t r eng th t es t as th i s app roach does no t g i ve an adequa te

i nd i ca t i on o f t he qua l i t y o f t he cove r conc re te . The cove r

conc re te ac t s as a ba r r i e r be tween t he r e i n fo r c i ng s t ee l and


5-9

the ex te rna l agg ress i ve env i r onmen t and i t s qua l i t y i s o f g rea t

impo r t ance i n du rab i l i t y cons ide ra t i ons .

The du rab i l i t y o f conc re te i s a f unc t i on o f po ros i t y . S t r eng th

i nc reases w i t h dec reas ing po ros i t y and po ros i t y i s a f f ec ted by

cap i l l a r y po ros i t y and a i r - vo i d po ros i t y . Po ros i t y may be

de f i ned as t he pe rcen tage vo ids i n a samp le . Vo ids , wh i ch a re

spaces f i l l ed w i t h wa te r , a re a r esu l t o f t he fa i l u re t o expe l a l l

t he a i r f r om the we t conc re te .

The me t hod t ha t has been adop ted i s t o measu re a f l u i d

t r anspo r t pa rame te r o f t he ma te r i a l such as pe rmeab i l i t y t o

l i qu i ds o r gasses . F l u i d t r anspo r t p rope r t i es a re i n f l uenced by

cap i l l a r y po ros i t y and t he deg ree o f i n t e r connec t i on cap i l l a r i es .

Pe rmeab i l i t y ma y be de f i ned as t he ease w i t h wh i ch a l i qu i d o r

gas can pass t h rough a spec i f i c ma te r i a l .

5 . 6 .1 Poros i ty Tes t

Fo r each o f t he t h ree m ixes , two wa te r - cu red samp les we re

t es ted a f t e r 28 days . A co re was d r i l l ed f r om 150x1 50 cubes

and oven -d r i ed a t a t emp e ra tu re o f 100 ˚C fo r 24 hou rs t o

ensu re tha t a l l mo i s t u re was removed . A f t e r de te rm in i ng t he

we igh t o f t he oven -d r i ed samp les , t hey we re p l aced i n a

vacuum f o r 24 hou rs . The samp les we re t hen submerged i n de -

a i r ed d i s t i l l ed wa te r and once aga in p l aced i n a vacuum fo r 3

hou rs . Th i s was done t o ensu re t ha t a l l t he vo i ds i n t he

conc re te samp les we re f i l l ed w i t h wa te r . F ina l l y t he

submerged we igh t o f t he samp les wa s de te rm ined . The po ros i t y

t es t se t up can be seen i n F i gu re 5 .3 .


5-10

F igu re 5 .3 Pho to o f po ros i t y t es t se t up

The f o l l ow ing equa t i on was app l i ed to de te rm ine t he po ros i t y o f

t he conc re te :

Porosi ty = mass s a t – mass d r y ( equa t i on 5 .8 )

mass s a t – mass w a t

whe re :

mass s a t = we igh t o f sa tu ra ted samp le ( g )

mass d r y = we igh t o f oven -d r i ed samp le ( g )

mass w a t = we igh t o f samp le i n wa te r ( g )

5 .6 .2 Ox ygen Permeab i l i t y Tes t

The oxyg en pe rme ab i l i t y o f t he conc re te was de te rm ined f o r

two samp les o f each m ix a f t e r 28 days . A co re was d r i l l ed f r om

the 150x150 cube and oven -d r i ed a t 100 ˚C fo r 24 hou rs t o

p reven t expans ion c racks , wh i ch wou ld i n f l uence t he

pe rmeab i l i t y r ead ings . The appa ra tus cons i s t s o f a se r i es o f

va l ves , wh i ch de l i ve red o x ygen a t a known p ressu re t h rough

t he samp les , and ca l i b ra ted g l ass tubes t h rough wh i ch t he r a te


5-11

a t wh i ch t he oxyg en bubb les moved cou ld be measu red w i t h a

s t opwa tch .

The f o l l ow ing equa t i on was app l i ed t o de te rm ine t he

pe rmeab i l i t y coe f f i c i en t , k , o f t he conc re te .

K = 2 x t x Q x e x P ( equa t i on 5 .9 )

A (P 22 – P 1

2 )

whe re :

t = samp le t h i c kness (m)

e = oxyg en v i s c os i t y ( 2 .02 - 5 N . s /m 2 )

K = oxygen pe rmeab i l i t y ( l /m 2 )

Q = vo lu me pe r second pass ing t h rough samp le (m /s ³ )

A = c ross sec t i ona l a rea o f samp le (m 2 )

P 1 = a tmosphe r i c p ressu re (Pa )

P 2 = app l i ed p ressu re (Pa )

The oxyg en pe rmeab i l i t y i ndex (OP I ) can be ca l cu l a ted as :

OPI = -L og 1 0 K ( equa t i on 5 .10 )


6-1

6. TEST RESULTS AND DISCUSSION ON CEMENT TESTS

6 .1 INTRODUCTION

I n chap te r 6 , t he r esu l t s o f t he expe r imen ta l t es t s d i scussed i n

chap te r 4 a re r ev i ewed and ana l ysed t o examine t he reac t i v i t y

o f a gas i f i ca t i on as h used as a cemen t ex tende r .

F i r s t l y t he phys i ca l p rope r t i es o f t he gas i f i c a t i on ash w i l l be

d i scussed w i t h r e fe rence to t he pa r t i c l e s i ze d i s t r i bu t i on and

t he shape o f t he pa r t i c l es . The chem ica l p rope r t i es o f t he

gas i f i ca t i on ash w i l l be ana l ysed by cons ide r i ng t he r esu l t s

f r om XRF , XRD an d s tanda rd t es t s f o r ex tende rs .

The rea f t e r t he resu l t s o f t he mor ta r p r i sm resu l t s f o r i n t e r va l s

o f g r i nd i ng t imes and d i f f e ren t gypsum pe rcen tages w i l l be

i l l u s t r a ted and d i scussed . The d i scuss i on o f t he r esu l t s t akes

i n t o cons ide ra t i on t ha t t es t s we re conduc ted on a s i ng l e se t o f

samp les . L im i t a t i ons t o t he t es t i ng me thod w i l l be d i scussed

and poss ib l e imp rovemen ts w i l l be r ecommend ed .

6 .2 PHYSI CAL PROP E RTIES

6 .2 .1 Pa r t i c le S i ze D is t r ibu t ion Tes t

The wa te r dema nd and wo rkab i l i t y o f cemen t pas te i s

con t ro l l ed by t he pa r t i c l e s i ze d i s t r i bu t i on . As no th i ng can be

done t o a l t e r t he m ine ra l og i ca l cha rac te r i s t i c s , t he con t ro l o f

pa r t i c l e s i ze d i s t r i bu t i on i s t he on l y p rac t i ca l me thod by wh i ch

t he cemen t i t i ous ac t i v i t y can be enhanced .

The pa r t i c l e s i ze d i s t r i bu t i on o f t he cemen t and gas i f i ca t i on

ash g round f o r a two hou r t ime i n t e r va l can be seen i n F i gu re

6 .1 . I t i s obse rved t ha t t he gas i f i ca t i on ash , g r i nded sepa ra te

and i n t e rg round w i t h cemen t had s im i l a r pa r t i c l e s i ze

d i s t r i bu t i ons . The re i s a cons ide rab le d i f f e renc e i n pa r t i c l e s i ze


6-2

be tween t he gas i f i ca t i on ash and cemen t g r i nded sepa ra te l y f o r

t he same t ime i n t e r va l . The gas i f i ca t i on ash had a pa r t i c l e s i ze

r ange be tween 0 .08 μm and 50μm, whe re t he cemen t pa r t i c l es

r anged be tween 2μm and 110 μm. The resu l t s f o r a l l t he

g r i nd i ng t ime i n t e r va l s can be seen i n Append i x A . These

resu l t s i nd i ca te tha t t he cemen t c l i n ke r i s ha rde r t han t he

gas i f i ca t i on ash c l i n ke r . The pa r t i c l e s i ze o f i n t e rg r i nd i ng 65%

cemen t and 35% gas i f i ca t i on ash shows t ha t t he pa r t i c l e s i ze

d i s t r i bu t i on f o r t ime i n t e r va l s 1 ,5 hou rs and 2 hou rs we re

i den t i ca l . Fu r t he r g r i nd i ng d i d no t r educe t he f i neness o f t he

i n t e rg round samp le s i gn i f i can t l y ( see F igu re 6 .2 ) . Thus f r om

the pa r t i c l e s i ze d i s t r i bu t i on i t i s c l ea r t ha t an op t imum

g r i nd i ng t ime can be es tab l i shed .

H ighe r f i neness p rov i des a g rea te r su r f ace a rea t o be we t t ed ,

r esu l t i ng i n an acce le ra t i on o f t he hyd ra t i on r eac t i on . I t was

t hus expec ted t ha t t he sma l l e r pa r t i c l e s i ze o f t he gas i f i ca t i on

ash shou ld r equ i r e t he same o r mo re wa te r t han f l y ash .

0

10

20

30

40

50

60

70

80

90

100

0.01 0.1 1 10 100 1000

Particle size (μm)

Cum

ulat

ive

part

icle

siz

e %

IG,2hrGA,2hrCEM,2hrFly ash

F i gu re 6 .1 G raph o f cumu la t i ve pa r t i c l e s i ze d i s t r i bu t i on o f

cemen t and gas i f i ca t i on ash (g r i nded sepa ra te and i n te rg round )


6-3

0102030405060708090

100

0.1 1 10 100 1000

Particle size (μm)

Cum

ulat

ive

part

icle

siz

e %

IG, 30min

IG,1hr

IG,1.5hr

IG,2hrIG,2.5hr

IG,4hr

F i gu re 6 .2 Cumu l a t i ve pa r t i c l e s i zes f o r gas i f i ca t i on ash and

cemen t i n t e rg round

The re l evance o f t he Ros in -Ramml e r pa r t i c l e s i ze d i s t r i bu t i on

pa rame te r s was eva lua ted by compa r i ng t he f i t t ed f unc t i ons f o r

t he cumu la t i ve % ove rs i ze pa r t i c l e s i ze d i s t r i bu t i ons f o r

d i f f e ren t g r i nd i ng t imes . Bo th t he cons tan ts i n t he equa t i on

va r y w i t h g r i nd i ng t ime an d t he re fo re t he cons tan t s as such

canno t be used t o compa re t he samp les (See t ab l e 6 .1 ) . The

f unc t i ons f o r gas i f i ca t i on ash a re p l o t t ed i n F i gu re 6 .3 . The res t

o f t he pa r t i c l e s i ze d i s t r i bu t i ons can be v i ewed i n Append i x B .

0%10%20%30%40%50%60%70%80%90%

100%

0 50 100 150 200 250

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,30minGA,1hrGA,1.5hrGA,2hrGA,2.5hrGA,4hr

F igu re 6 .3 Summary o f e xponen t i a l f i t t ed f unc t i ons f o r t he

cumu la t i ve % ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on


6-4

Acco rd i ng t o F i gu re 6 .3 t he pos i t i on pa rame te r (X o ) and

t he re fo re t he pa r t i c l e s i ze d i s t r i bu t i on dec rease as t he g r i nd i ng

t ime i nc reases f o r gas i f i ca t i on ash . I t i s c l ea r t ha t t he g r i nd i ng

t ime has a s i gn i f i can t i n f l uence on t he range o f t he pa r t i c l e

s i ze d i s t r i bu t i ons g rea te r t han t he pos i t i on pa rame te r ( X o ) . The

sho r t e r g r i nd i ng t imes seem to have more o f t he l a rge r ( coa rse )

pa r t i c l es . Th i s t r end can a l so be seen when compa r i ng t he

Ros in -Rammle r s l ope (n ) pa rame te r s ( see F igu re 6 .4 ) . See

Append i x C f o r r es t o f g raphs .

The g raph c l ea r l y i nd i ca tes t ha t t he pa r t i c l e s i ze o f gas i f i ca t i on

ash dec reases as t he g r i nd i ng t ime i nc rease . The f i t t ed t r end

l i ne t ha t bes t desc r i bes t he measu red va lues i s an exponen t i a l

f unc t i on . The s ta t i s t i ca l R -squa re va lue f o r a l l t he samp les o f

t he expo nen t i a l f i t i s be tween 0 .995 and 0 .999 . The exponen t i a l

equa t i on i s t he re fo re a t r ue r ep resen ta t i ve o f t he cumu la t i ve %

ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on .

0

0.5

1

1.5

0 1 2 3 4 5 6

ln (Particle size (μm))

ln ln

(1/c

umul

ativ

e %

ov

ersi

ze)

GA,30minGA,1hrGA,1.5hrGA,2hrGA,2.5hrGA,4hr

F i gu re 6 .4 Summa ry o f Ros in -Rammle r d i s t r i bu t i ons


6-5

Tab le 6 .1 F i t t ed f unc t i ons o f ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on

Fitted function

y = a e(bx) Sample

a b

R² Xo

IG,30 min 0.955 -0.0198 0.9996 47.90

IG,1hr 0.975 -0.0354 0.9997 28.01

IG, 1.5hr 0.9929 -0.0514 0.998 19.88

IG, 2hr 0.9835 -0.05 0.9983 20.00

IG, 2.5hr 0.9693 -0.0532 0.9986 18.20

IG, 4hr 0.9822 -0.0608 0.9963 16.69

GA,30min 0.9429 -0.0122 0.9991 78.35

GA, 1hr 0.9329 -0.0284 0.9989 33.05

GA, 1.5hr 0.9331 -0.0382 0.9986 24.51

GA, 2hr 0.9452 -0.0507 0.9978 19.14

GA, 2.5hr 0.9254 -0.0554 0.9981 16.64

GA, 4hr 0.8942 -0.0781 0.9952 10.93

Cem,30min 0.9675 -0.024 0.9936 37.71

Cem, 1hr 0.7121 -0.0144 0.8842 33.11

Cem, 1.5hr 0.9411 -0.0249 0.9858 37.29

Cem, 2hr 0.8794 -0.0237 0.9681 29.43

Cem, 2.5hr 0.9077 -0.0247 0.9791 32.04

Cem, 4hr 0.8179 -0.0179 0.9454 25.71

IB, 30 min 0.9031 -0.0165 0.9874 45.51

IB, 1hr 0.8898 -0.023 0.9792 31.66

IB, 1.5hr 0.9607 -0.03 0.9973 30.55

IB, 2hr 0.945 -0.033 0.9946 25.93

IB, 2.5hr 0.9142 -0.0321 0.9897 25.59

IB, 4hr 0.8079 -0.0256 0.9545 23.27

The va lues o f t he s l ope n and t he pos i t i on pa rame te r X o f o r a l l

t he samp les can be seen i n Tab le 6 .2 . The equa t i ons f o r t he

l i nea r t r end l i ne f i t t ed t o t he Ros in -Rammle r d i s t r i bu t i on g raph

and t he s ta t i s t i ca l R -squa re va lue o f t he l i nea r f i t a re a l so

l i s t ed i n Tab le 6 .2 .


6-6

Tab le 6 .2 Ros in -Rammle r p a r t i c l e s i ze d i s t r i bu t i on pa rame te r s

Fitted function

y = cx +d Sample

c d

R² Xo n

IG,30 min 0.9743 -3.7795 1 47.90 0.9743

IG,1hr 0.9848 -3.2664 1 28.01 0.9848

IG, 1.5hr 0.9959 -2.9494 1 19.88 0.9959

IG, 2hr 0.9902 -2.951 1 20.00 0.9902

IG, 2.5hr 0.9813 -2.8498 1 18.20 0.9813

IG, 4hr 0.9896 -2.7544 1 16.69 0.9896

GA,30min 0.9653 -4.0996 1 78.35 0.9653

GA, 1hr 0.958 -3.347 1 33.05 0.958

GA, 1.5hr 0.9589 -3.0666 1 24.51 0.9589

GA, 2hr 0.9665 -2.8296 1 19.14 0.9665

GA, 2.5hr 0.9543 -2.6897 1 16.64 0.9543

GA, 4hr 0.934 -2.2793 0.9999 10.93 0.934

Cem,30min 0.9816 -3.6309 1 37.71 0.9816

Cem, 1hr 0.816 -3.1629 0.9984 33.11 0.816

Cem, 1.5hr 0.9662 -3.5129 1 37.29 0.9662

Cem, 2hr 0.9307 -3.3684 0.9999 29.43 0.9307

Cem, 2.5hr 0.9469 -3.4172 0.9999 32.04 0.9469

Cem, 4hr 0.8908 -3.4053 0.9996 25.71 0.8908

IB, 30 min 0.9424 -3.7753 0.9999 45.51 0.9424

IB, 1hr 0.9348 -3.4207 0.9999 31.66 0.9348

IB, 1.5hr 0.9777 -3.3921 1 30.55 0.9777

IB, 2hr 0.9686 -3.2527 1 25.93 0.9686

IB, 2.5hr 0.9499 -2.0479 0.9999 25.59 0.9499

IB, 4hr 0.8839 -3.0507 0.9995 23.27 0.8839

The e f f ec t o f g r i nd i ng t ime on pa r t i c l e s i ze d i s t r i bu t i on can be

seen i n F i gu re 6 .5 . F rom t he g raph i t i s obse rved t ha t as t he

g r i nd i ng t ime i s ex tended t he pa r t i c l es become f i ne r , r esu l t i ng

i n t he pos i t i on pa rame te r dec reas ing . Th i s t r end i s p rom inen t

f o r t he gas i f i ca t i on and as we l l as t he b l ended cemen t . The

cemen t c l i n ke r a l one has no c l ea r t r end , s i nce t he pos i t i on

pa rame te r o f t he cemen t a f t e r 30 m inu tes i s l ess t han t ha t o f

i n t e rg r i nd i ng o r gas i f i ca t i on ash . A f t e r 1 hou r t he pos i t i on


6-7

pa rame te rs f o r a l l t h ree a re app rox ima te l y t h e same . He rea f t e r

gas i f i ca t i on ash and i n t e rg r i nd i ng con t i nues t o r educe as

g r i nd i ng t ime i s ex tended , wh i l e t he cemen t i nc reases s l i gh t l y .

01020

30405060

708090

0.5 1 1.5 2 2.5 4

Grinding time (hours)

Posi

tion

Para

met

er X

o (µ

m)

IG

GA

CEM

F igu re 6 .5 Re la t i on be tween g r i nd i ng t ime and pos i t i on

pa rame te r X o

The pos i t i on pa rame te r s o f cemen t r ange be tween 25μm and

38μm an d t he re i s no c l ea r t r end f o r t he pos i t i on pa rame te r o f

cemen t t o r educe w i t h i nc reased g r i nd i ng t ime . The pos i t i on

pa rame te r o f gas i f i ca t i on ash and i n t e rg r i nd i ng i s s i gn i f i can t l y

sma l l e r t han t ha t o f cemen t , even a f t e r 4 hou rs o f g r i nd i ng .

A f t e r 2 hou rs o f g r i nd i ng t he r educ t i on i n pos i t i on pa rame te r f o r

gas i f i ca t i on ash and i n t e rg r i nd i ng i s no t as no t i ceab le as

be fo re . The g raph i nd i ca tes t ha t an exponen t i a l r e l a t i on ex i s t s

be tween pa r t i c l e s i ze and g r i nd i ng t ime . I t seems as i f an

op t imum g r i nd i ng t ime can be es tab l i shed . Fo r bo th the

i n t e rg r i nd i ng and gas i f i ca t i on ash t h i s op t imum seems t o be i n

t he r eg ion o f 2 hou rs . G r i nd ing f o r l onge r t han t h i s op t imum

t ime wou ld no t dec rease t he pa r t i c l e s i ze cons ide rab l y mo re

and wou ld on l y add t o t he cos t o f g r i nd i ng .

I n F i gu re 6 .6 t he s l ope i s p l o t t ed as a f unc t i on o f t he g r i nd i ng

t ime . F rom th i s g raph i t can be seen t ha t f o r i n t e rg r i nd i ng and


6-8

gas i f i ca t i on ash t he g r i nd i ng t ime does no t have an i n f l uence

on t he s l ope (n ) va l ue , wh i ch rep resen t s t he range o f t he

pa r t i c l e s i ze d i s t r i bu t i on o f t he pa r t i c l e s i zes g rea te r t han t he

pos i t i on pa rame te r . I t i s obse rved t ha t f o r t he gas i f i ca t i on ash

and i n t e rg r i nd i ng , t he s l ope a f t e r 2 hou rs g r i nd i ng i s a

max i mum and t he rea f t e r t he s l ope dec reases . Thus a f t e r 2

hou rs t he s i ze r ange i s na r row and any i nc rease o r dec rease i n

g r i nd i ng t ime make t he s i ze r ange w ide r . Fo r cemen t t he r ange

va r i es f o r each g r i nd i ng t ime i n t e r va l . I n t e rg r i nd i ng had t he

l a rge r s l ope (n ) and wou ld have a na r rowe r d i s t r i bu t i on t han

t he gas i f i ca t i on ash and t he cemen t . Th i s d i f f e rence i n s l ope i s

howeve r ve r y sma l l and obse rved t r ends a re no t deemed t o be

s i gn i f i can t .

0

0.2

0.4

0.6

0.8

1

1.2

0.5 1 1.5 2 2.5 4


Slop

e (n

)

IG

GA

CEM

F igu re 6 .6 Re la t i onsh ip be tween g r i nd i ng t ime and s l ope

pa rame te r (n )

The va lues o f t he ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

(D50 ) an d (D10 ) can be seen i n Tab le 6 .3 . These pa rame te r s

can be compa red f o r d i f f e ren t samp les .


6-9

Tab le 6 .3 Ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

Oversize particle size distribution parameters Sample

D50 (µm) D10 (µm)

3 - 30µm (%) <3 µm (%)

IG,30 min 32.1 113.6 41.73 9.18

IG,1hr 19.4 64.2 55.20 13.76

IG, 1.5hr 14.0 44.4 62.05 18.01

IG, 2hr 13.9 45.4 62.18 18.48

IG, 2.5hr 12.7 43.1 62.74 19.65

IG, 4hr 11.6 37.3 64.44 22.07

GA,30 min 50.9 183.5 31.78 7.34

GA, 1hr 21.2 78.7 48.51 14.82

GA, 1.5hr 15.8 58.9 56.30 16.55

GA, 2hr 12.4 44.1 59.57 22.01

GA, 2.5hr 10.5 40.4 59.79 25

GA, 4hr 7.3 31.3 58.34 32.48

Cem,30 min 26.2 92.8 52.82 5.66

Cem, 1hr 22.2 100.9 57.08 6.32

Cem, 1.5hr 23.9 86.5 55.41 6.83

Cem, 2hr 21.4 83.4 57.94 7.13

Cem, 2.5hr 22.1 85.1 56.99 7.42

Cem, 4hr 22.7 106.7 53.25 7.97

The D50 and D10 resu l t s i n t he t ab l e i nd i ca te t ha t f o r

i n t e rg r i nd i ng o f 35% gas i f i ca t i on ash and 65% cemen t i n t he

ba l l m i l and f o r sepa ra te l y g rou nded gas i f i ca t i on ash and

cemen t t he ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on pa rame t e r s , D50

and D10 , dec rease f o r i nc reased g r i nd i ng t ime . Th i s t r end i s

mo re obse rvab le f o r t he gas i f i ca t i on ash . The gas i f i ca t i on ash

has a so f t e r c l i n ke r t han t h e cemen t and t h i s i s seen s i nce t he

gas i f i ca t i on ash i s eas ie r t o g r i nd . Fo r t he cemen t t he re i s no

c l ea r t r end . Th i s i s due t o t he ha rde r cemen t c l i n ke r . I t seems

t ha t i n c reased g r i nd i ng d i d no t a f f ec t t he pa r t i c l e s i ze . The

t ab le a l so i nd i ca te t he 30 -3µm and <3µm pe rcen tage pa r t i c l es .


6-10

These resu l t s i nd i ca te t ha t w i t h i nc reased g r i nd i ng t ime t he %

o f pa r t i c l es <3µm i nc rease . The cemen t r ema ine d a lmos t

cons tan t be tween 52 and 58µm. Fo r bo th t he i n t e rg r i nd ing and

gas i f i ca t i on ash t he % pa r t i c l es become more as g r i nd i ng t ime

i nc rease . A l l o f t he r esu l t s i n t he t ab l e i nd i ca te t ha t w i t h

i nc reased g r i nd i ng t ime t he pa r t i c l es become sma l l e r .

6 .2 .2 Shape o f Par t i c les

Pa r t i c l e shape has a s t r ong i n f l uence on t he wa te r r equ i r emen t

o f conc re te . The un ique sphe r i ca l shape o f f l y ash makes i t s

wa te r r equ i r emen t l owe r and t hus imp roves t he wo rkab i l i t y ( see

F igu re 6 .7 ) . The gas i f i ca t i on ash has no un ique s t r uc tu re and

cou ld be desc r i bed as angu la r as can be seen i n F i gu re 6 .8 .

Angu la r shapes have h i g he r wa te r r equ i r emen ts , and an

i nc rease i n po ros i t y and a dec rease i n s t r eng th may be

expec ted .

F i gu re 6 .7 Scann ing e l ec t ron m i c roscope pho to o f f l y ash


6-11

F igu re 6 .8 Scann ing e l ec t ron m i c roscope pho to o f gas i f i ca t i on

ash

The B la i ne su r f ace a rea (Append i x D ) f o r cemen t , gas i f i ca t i on

ash and i n t e rg round cemen t and gas i f i ca t i on ash i s seen i n

F i gu re 6 .9 .

0

100

200

300

400

500

600

700

800

30 min 1 hour 1.5 hours 2 hours 2.5 hours 4 hours


Bla

ine

Surf

ace

Are

a m

2 /g

Cement Gasification ash Intergrinding

F i gu re 6 .9 G raph i nd i ca t i ng B la i ne su r f ace a rea


6-12

F rom the g raph i t can be seen t ha t cemen t has a su r face a rea

rang ing be tween 300m 2 /g and 450m 2 /g . Th i s r ange o f su r f ace

a rea co r responds t o commerc i a l cemen t as r epo r t ed by Bha t t y

e t a l ( 2004 ) . The su r f ace a rea o f cemen t i nc rease f o r t he

g r i nd i ng t ime i n t e r va l s up t o 2 hou rs , a f t e r wh i ch t he su r f ace

a rea rema ins cons tan t f o r 2 . 5 hou rs and s l i gh t l y dec reases f o r

4 hou rs g r i nd i ng . Th i s i nd i ca tes t ha t l onge r g r i nd i ng does no t

keep i nc reas ing t he su r f ace a rea . The re seems t o be an

op t imum su r f ace a rea f o r t he cemen t . I n i t i a l l y a f t e r 30

m inu tes , gas i f i ca t i on ash has t he l owes t su r face a rea wh i l e t he

i n t e rg round samp le i s c l ose t o t he cemen t samp le . F rom 1 hou r

g r i nd i ng , bo th t he gas i f i ca t i on ash and i n t e rg round gas i f i ca t i on

ash and cemen t samp le has a h i ghe r su r f ace a rea than t he

cemen t . The gas i f i ca t i on as h and i n t e rg round gas i f i ca t i on ash

and cemen t i s app rox ima te l y t he same up t o 2 hou rs o f g r i nd i ng ,

The rea f t e r t he gas i f i ca t i on ash ’ s su r f ace a rea i nc rease more

t han t he i n t e rg round . Th i s i nd i ca tes t ha t t he su r f ac e a rea o f

gas i f i ca t i on ash i nc rease , wh i l e t he cemen t r eached an

op t imum su r f ace a rea . A f t e r 2 hou rs , when cemen t r eached an

op t imum su r f ace a rea , t he i n t e rg round gas i f i ca t i on ash and

cemen t samp le i nc reased l ess i n su r face a rea .

6 .3 CHEMICAL PROPERTIES

6 .3 .1 XRF

The XRF resu l t s o f t he gas i f i ca t i on ash p rov i ded i ns i gh t i n t o

t he behav iou r i n r eac t i v i t y i n conc re te . The chem ica l

compos i t i on o f bo th gas i f i ca t i on and f l y ash can be seen i n

Tab le 6 .4 .

These resu l t s i nd i ca te t ha t gas i f i ca t i on ash has a chem ica l

compos i t i on s im i l a r t o t ha t o f f l y as h and i t shou ld thus be

accep tab le t o use as a cemen t ex tende r i n conc re te . The re a re


6-13

th ree e l emen ts i n t he f o rm o f ox i des p resen t i n t he gas i f i ca t i on

ash (MnO, C r 2 O 3 and V 2 O 5 ) wh i ch a re no t i n f l y ash . These

e l emen ts shou ld have no e f f ec t on t he r eac t i v i t y . T he P 2 O 5 -

con ten t i s l owe r i n t he gas i f i ca t i on ash bu t was no t cons ide red

t o be s i gn i f i can t . The va ry i ng amoun t o f A l 2 O 3 w i t h i n t he ashes

i s no t so impo r t an t i n de te rm in i ng t he i n f l uence on p rope r t i es

i n conc re te , t hus the l owe r con ten t o f A l 2 O 3 i n gas i f i ca t i on ash

wou ld no t have d e t r imen ta l e f f ec t s on t he conc re te . These

resu l t s i nd i ca te t ha t gas i f i ca t i on ash shou ld be accep tab le t o

use as a cemen t ex tende r i n conc re te .

Tab le 6 .4 XRF resu l t s

E lements Gas i f i ca t ion Ash

%

T yp ica l v a lues o f South A f r i can F l y

Ash* %

Fe 2 O 3 6 .8 3 .7 -4 .7

MnO 0 .13 0

C r 2 O 3 0 .63 0

V 2 O 5 0 .02 0

T iO 2 1 .43 1 .4 -1 .9

CaO 8 .17 7 .1 -10 .5

K 2 O 0 .83 0 .5 -1 .2

P 2 O 5 0 .7 1 .1 -1 .4

S iO 2 48 .5 45 -49

A l 2 O 3 23 .5 29 -31

MgO 2 .3 1 .8 -2 .8

Na 2 O 0 .5 0 .1 -0 .8

C l 0 0

S 0 .4 0

SO 3 0 .49 0 .5 -1 .0

Loss on i gn i t i on 5 .18 5 .0

* (SANS 1491 -2 :2005 / SABS 1491 -2 :2005 )


6-14

6 .3 .2 XRD

The XR D resu l t s showed t ha t gas i f i ca t i on ash has h i gh

pe rcen tages o f qua r t z (S iO 2 ) and mu l l i t e (A l 6 S iO 1 3 ) wh i ch i s

s im i l a r t o f l y ash .

The XRD ana l ys i s o f gas i f i ca t i on as h shows t ha t ano r t h i t e ,

sod ian i n t e rmed ia te ( (Ca , Na ) (S i , A l ) 4 O 8 ) , mu l l i t e (A l 6 S iO 1 3 ) ,

a l pha -qua r t z (S iO 2 ) , we re f ound t o be t he ma jo r m ine ra l s

p resen t i n ash , d i ops i de (Ca (Mg ,A l ) (S i ,A l ) 2 O 6 ) , i nd i a l i t e

(Mg 2 A l 4 S i 5 O 1 8 ) and geh len i t e (Ca 2 A l 2 S iO 7 ) we re i den t i f i ed i n

sma l l concen t ra t i ons . These resu l t s i nd i ca te t ha t gas i f i ca t i on

ash shou ld be accep tab le f o r use as a cemen t ex tende r i n

conc re te .

GASIFICATION

00-015-0776 (I) - Mullite, syn - Al6Si2O13 - Orthorhombic - 00-018-1202 (I) - Anorthite, sodian, intermediate - (Ca,Na)(Si,Al)4O8 - Triclinic - 00-046-1045 (* ) - Quartz, syn - SiO2 - Hexagonal - I/Ic PDF 3.4 - GASIFICATION - File: HANLI04-5.raw - Type: 2Th/Th locked - Start : 5.000 ° - End: 70.000 ° - Step: 0.040 ° - Step time: 1.5 s - Temp.: 25 °C (Room) - Time Started: 0 s - 2-Theta: 5.000 ° - Theta: 2.500 ° - Chi: 0.00 ° -

Lin

(Cou

nts)

0

100

200

300

400

500

600

700

800

900

1000

1100

1200

1300

1400

1500

2 Theta (Cu K-alpha)

6 10 20 30 40 50 60 70

F i gu re 6 .10 XRD resu l t s f o r gas i f i ca t i on ash


6-15

6 .3 .3 S tandard Tes ts fo r Cement i t ious Mate r ia ls

The resu l t s o f t he s t anda rd t es t s conduc ted a re summa r i zed i n

Tab le 6 .5 . The chem ica l requ i r emen ts o f t he gas i f i ca t i on ash

comp ly w i t h t he spec i f i ca t i on as se t f o r f l y ash i n a l l bu t two

cases . The gas i f i ca t i on ash has a h i ghe r l oss on i gn i t i on

( LO I ) , due t o t he h i ghe r ca rbon con ten t , wh i ch g i ves the ash a

da rk g rey co l ou r . The wa te r r equ i r emen t o f gas i f i ca t i on ash i s

mo re t han 100% and t h i s can be exp la i ned when cons ide r i ng

t he angu la r shape o f t he gas i f i ca t i on ash . The s t r eng th f ac to r

o f gas i f i ca t i on ash i s 2% h ighe r t han f l y ash . The f ac to r s t ha t

do no t mee t t he l im i t s as se t f o r f l y ash do no t cause a g rea t

conce rn bu t i t shou ld be i nves t i ga ted .

Tab le 6 .5 Chem ica l t es t r esu l t s

Tes t Me thod Gas i f i ca t ion

ash L imi ts fo r

F l y ash

Su lphu r t r i o x i de con ten t , %

(m /m) SANS 50 196 -2 0 .49 <2 .5

Loss on i gn i t i on , % (m /m) SANS 50 196 -3 5 .18 <5 .0

F ree wa te r con ten t , %

(m /m) SANS 61 51 0 .19 1

F i neness , r es i due re ta i ned

on a s i eve w i t h squa re

ape r t u res o f nom ina l s i ze

45um, % (m /m)

SANS 61 57 6 .5 12 .5

Wa te r r equ i r emen t , % o f

con t ro l , max SANS 61 56 > 100 95

S t reng th f ac to r , % SANS 50 196 -1 8 >6

Soundness , expans ion ,

mm, ma x SANS 50 196 -3 0 <1

Re la t i ve dens i t y LSA Me th od 2 .59 2 .3

Spec i f i c su r f ace a rea ,

c m 2 /g LSA Me th od 7802

No t

quan t i f i ed


6-16

6 .4 EFFECT OF GRI N DING T I ME ON T HE PROPERTIES OF INTERBL ENDE D GASIF ICA T ION A S H AND C EME NT

6 .4 .1 Mor ta r P r ism Co mpress ive S t reng th

F i gu re 6 .11 shows t he r esu l t s f o r i n t e rb l end ing gas i f i ca t i on ash

and cemen t manu fac tu red i n t he l abo ra to r y . See Append i x E f o r

t he mo r t a r p r i sm s t r eng th summary . Bo th t h e gas i f i ca t i on ash

and cemen t c l i nke r we re g round f o r d i f f e ren t t ime i n t e r va l s . A

m i x o f cemen t g r i nded f o r 2 hou rs and no t i n t e rb l ended can

a l so be seen i n t he g raph . F rom the resu l t s i t i s obse rved t ha t

con t i nua l l y , t h roughou t t he s t r eng th deve lopmen t , t he m i x

con ta i n i ng cemen t w i t h 2 hou rs g r i nd i ng t ime had t he h i ghes t

compress i ve s t r eng th . A f t e r 28 days t he 2 .5 hou r m i x was

a lmos t equa l t o t he 2 hou r m i x . The m ix made w i t h cemen t

con ta i n i ng on l y c l i nke r ach ieved t he same compress i ve

s t r eng th a f t e r 28 days . The d i f f e rence i n compress i ve s t r eng th

o f m i xes g r i nded f o r l e ss than 2 hou rs was app rox ima te l y 10

MPa . Th i s d i f f e rence c l ea r l y i nd i ca tes t han g r i nd i ng t ime

shou ld no t be sho r te r t han 2 hou rs .

05

101520253035404550

2 days 7 days 28 days

Days

Com

pres

sive

str

engt

h M

Pa 30 min

1 hour1.5 hours

2 hours

2.5 hours4 hours

Cement (2 hrs)

F i gu re 6 .11 Compress i ve s t r eng ths fo r i n t e rb l end ing

gas i f i ca t i on ash and cemen t f o r d i f f e ren t g r i nd i ng t imes


6-17

The compress i ve s t r eng th r esu l t s o f t he mo r ta r p r i sms a re

de f i ned as a s t r eng th c l ass i n Tab le 6 .6 f r om SANS 50197 -

1 /SABS EN 197 -1 :2000 .

Tab le 6 .6 S t reng th c l asses o f i n t e rb l end ing m i xes g r i nd i ng t ime

30 min 1 hour 1.5

hours 2

hours2.5

hours 4

hours cement (2hrs)

Strength class

N/A to 32.5 N 32.5R 32.5R 42.5 R 42.5 N 42.5 N 42.5 N

Percentage strength

development after 7 days

63% 75% 71% 76% 65% 73% 70%

F rom the s t r eng th c l ass requ i r emen ts t he d i f f e rence i n t he

compress i ve mo r t a r s t r eng th f o r t he m i xes a re h i gh l i gh ted .

G r i nd i ng t imes sho r t e r t han 30 m inu tes does no t ach ieve

s t r eng ths f o r an accep tab le s t r eng th c l ass . Gr i nd i ng t imes o f 1

and 1 .5 hou rs p roduce a cemen t s t r eng th c l ass o f 32 .5R . A

cemen t s t r eng th c l ass o f 42 .5 R was p roduced f o r 2 hou rs

g r i nd i ng t ime and f o r t he g r i nd i ng t imes l onge r t han 2 hou rs

cemen t w i t h a s t r eng th c l ass o f 42 .5 N wa s ach ieved . When

cons ide ra t i on i s g i ven t o t he cemen t g r i nded f o r 2 hou rs and

no t i n t e rb l ended , i t i s c l ea r t ha t gas i f i ca t i on ash had a

con t r i bu t i on t o t he ea r l y s t r eng th deve lopme n t o f t he mo r ta r

p r i sms . Tab le 6 .6 a l so i nd i ca tes t he pe rcen tage o f 28 day

s t r eng th ga ined a f t e r 7 days , wh i ch i nd i ca tes t ha t mo s t l y 70%

o f t he s t reng th i s ach ieved a f t e r 7 days . G r i nd ing f o r 2 hou rs

i nc reased t he 7 day s t r eng th t o 76% o f t he 28 day s t r eng th .

6 .4 .2 Mor ta r P r isms F lexura l S t reng th

The f l exu ra l s t r eng ths o f t he i n t e rb l ended m ixes (F i gu re 6 .12 )

i nd i ca te the same t r end as d i d t he compress i ve s t r eng th f o r t he

m ix g r i n ded f o r 2 hou rs (Append i x E ) . A f t e r 28 days t he

i n t e rb l ended m ixes g r i nded f o r l onge r t han 2 hou rs exceeded

t he f l exu ra l s t r eng th o f t he cemen t on l y m i x . The d i f f e rence i n

f l e xu ra l s t r eng ths f o r t he m i xes was app rox ima te l y 1 MPa ,


6-18

wh i ch i s no t a cons ide rab le d i f f e rence . The f l exu ra l s t r eng th

r esu l t s shows t ha t g r i nd i ng t imes g rea te r t han 2 hou rs ach ieved

be t t e r f l exu ra l s t r eng ths .

0123456789

10


Days

Flex

ural

str

engt

h M

Pa

30 min

1 hour

1.5 hours

2 hours

2.5 hours

4 hours

Cement (2 hrs)

F i gu re 6 .12 F l exu ra l s t r eng ths f o r i n t e rb l end ing gas i f i ca t i on

ash and cemen t f o r d i f f e ren t g r i nd i ng t imes

Tab le 6 .7 g i ves a pe rcen tage o f t he compress i ve s t r eng th

ach ieved by t he f l exu ra l s t r eng th a f t e r 28 days . I t i s expec ted

t ha t t he f l e xu ra l s t r eng th shou ld be 10% o f t he compress i ve

s t r eng th . A l l o f t he m i xes had a f l e xu ra l s t r eng th o f a t l eas t

19% o f t he compress i ve s t r eng th . The resu l t s i nd i ca te t ha t

i n t e rb l end ing gas i f i ca t i on ash and cemen t ach ieved be t t e r

f l e xu ra l s t r eng ths than a cemen t on l y m i x .


i n t e rb l end ing

30 min 1 hour 1.5 hours

2 hours

2.5 hours

4 hours

cement (2hrs)

Percentage of

compressive strength achieved

24% 22% 21% 19% 19% 20% 18%


6-19

6 .4 .3 Par t i c le S i ze D is t r ibu t ion

The e f f ec t o f t he pa r t i c l e s i ze d i s t r i bu t i on on t h e 28 -day

compress i on s t r eng ths can be seen i n F i gu re 6 .13 and F igu re

6 .14 . The Ros in -Rammle r pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

( as d i scussed i n 4 .3 .1 .2 ) a re p l o t t ed as a f unc t i on o f t he 28 -

day comp ress ion s t r eng ths .

The g raph i nd i ca tes t ha t t he compress i ve s t r eng th i nc reased

w i t h dec reas ing pos i t i on pa rame te r s ( X o ) f o r i n t e rb l end ing o f

cemen t c l i n ke r and gas i f i ca t i on ash . Thus f i ne r pa r t i c le

ach ieved g rea te r s t r eng ths . The i n t e rb l ended m ix o f 4 hou rs

g r i nd i ng t ime had t he sma l l es t pos i t i on pa rame te r ( X o ) , bu t

ach ieved s l i gh t l y l owe r s t r eng ths t han t he 2 .5 hou r and 2 hou r

m i xes . I t can be seen i n F i gu re 6 .13 t ha t f o r g r i nd i ng t imes

l onge r t han 2 hou rs t he pos i t i on pa rame te r (X o ) dec reases

s l i gh t l y wh i l e no s i gn i f i can t i n c rease i n compress i ve s t r eng th i s

obse rved .

0

10

20

30

40

50

0 10 20 30 40 50

Position parameter X o (μm)

Com

pres

sive

Str

engt

h M

Pa

IB,30 minIB, 1hr

IB, 1.5hr

IB, 2hrIB, 2.5hr

IB, 4hr

F igu re 6 .13 Re la t i on be tween compress i ve s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on pos i t i on pa rame te r ( X o ) f o r

i n t e rb l end ing gas i f i ca t i on ash and cemen t


6-20

F igu re 6 .13 i nd i ca tes t ha t pos i t i on pa rame te r s l a rge r t han

30μm ac h ieved l owe r compress i ve s t r eng ths . The re was a

cons ide rab le i nc rease i n compress i ve s t r eng th f r om 30μm to

25μm. F rom the g raph i t seems as i f a peak i s r eached a t 25μm,

whe re t he h i ghes t s t r eng ths we re r eached . I t i s t hus conc luded

t ha t 25μm, and t hus 2 hou rs i s an op t imum when pos i t i on

pa rame te rs i s compa red t o t he compress i ve s t r eng th . Howeve r ,

t he d i f f e rence i n compress i ve s t r eng th be tween t he 2 , 2 . 5 and

4 hou rs a re sma l l and t hus a 2 -hou r g r i nd i ng t ime seems t he

mos t e f f ec t i ve when cons ide r i ng s t r eng th , pa r t i c l e s i zes and

cos t o f g r i nd i ng .

I n F i gu re 6 .14 t he s l ope (n ) i s p l o t t ed as a f unc t i on o f t he 28 -

day compress ion s t r eng th . The sma l l es t s l ope , a f t e r 4 hou rs

g r i nd i ng had h i gh compress i ve s t r eng th . G r i nd i ng t imes o f 2

and 2 .5 hou rs had app rox ima te l y t he s ame co mpress i ve

s t r eng ths bu t h i ghe r s l opes . The re i s no c l ea r t r end t o

es tab l i sh t ha t sma l l e r s l opes g i ve h i ghe r compress i ve s t r eng ths .

Howeve r , t he d i f f e rence i n compress ion s t r eng th be tween t he 2

and 4 hou r g r i nd i ng t ime i s sma l l and op t ima l l y t h e 2 hou r

g r i nd i ng t ime i s mos t e f f ec t i ve when s t r eng th , pa r t i c l e s i ze and

cos t o f g r i nd i ng i s cons ide red .

0

10

20

30

40

50

0.85 0.9 0.95 1

Slope (n )

Com

pres

sive

str

engt

h (M

Pa)

IB,30 min

IB, 1hr

IB, 1.5hr

IB, 2hr

IB, 2.5hr

IB, 4hr

F igu re 6 .14 Re la t i on be tween compress i on s t r eng ths and

Ros in -Rammle r d i s t r i bu t i on s l ope ( n ) pa rame te r f o r

i n t e rb l end ing gas i f i ca t i on ash and cemen t


6-21

I n F i gu re 6 .15 , t he ove rs i ze pa r t i c l e s i ze d i s t r i bu t i on

pa rame te r s (D50 ) and (D10 ) a re p l o t t ed as a f unc t i on o f t he 28 -

day compress i ve s t r eng th i n o rde r t o f i nd t he i n f l uence o f

compress i ve s t r eng th on t he pa r t i c l es s i ze d i s t r i bu t i on .

25

30

35

40

45

50

0 20 40 60 80 100 120 140

Oversize Particle size distribution parameters (μm)

Com

pres

sive

Str

engt

h (M

Pa)

IB,30 min

IB, 1hr

IB, 1.5hr

IB, 2hr

IB, 2.5hr

IB, 4hr

F igu re 6 .15 Re la t i on be tween compress ion s t r eng th and

pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s f o r i n t e rb l end ing

gas i f i ca t i on ash and cemen t

As t he ave rage pa r t i c l e s i ze becomes sma l l e r t he 28 -day

compress ion s t r eng th i nc reases . As t he 10% l a rges t pa r t i c l e

s i ze f o r d i f f e ren t g r i nd i ng t imes become sma l l e r compress i ve

s t r eng ths a l so i nc reases . A f t e r 2 h ou rs g r i nd i ng t he max i mum

compress i ve s t r eng th i s ob ta i ned . The d i f f e rence i n

compress i ve s t r eng th be tween 2 , 2 . 5 and 4 hou rs i s sma l l and

t hus an op t imum l im i t i s r eac hed a f t e r 2 hou rs g r i nd i ng f o r bo th

t he 50% and 10% l a rges t pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s .

D50 D10


6-22

6 .5 EFFECT OF GRI N DING T I ME ON T HE PROPERTIES OF INTER GR OUN D GASIF ICA T ION A S H AND C EME NT


F i gu re 6 .16 shows t he r esu l t s f o r gas i f i ca t i on ash and cemen t

c l i n ke r i n t e rg round i n t he b a l l m i l l f o r d i f f e ren t t ime i n t e r va l s .

See summary o f s t r eng th r esu l t s i n Append i x F . The resu l t s

i nd i ca te t ha t i n t e rg r i nd i ng f o r 2 hou rs ach ieved t he h i ghes t

compress i ve s t r eng th du r i ng t he s t reng th deve lopmen t . Same

as f o r t he i n t e rb l end ing , g r i nd i ng f o r sho r te r t han 1 .5 hou rs

ach ieved s t r eng ths o f app rox ima te l y 10 MPa l ess . The

compress i ve s t r eng th o f t he cemen t on l y m i x whe re s l i gh t l y

h i ghe r t han t he m ixes i n t e rg round f o r l onge r t han 2 hou rs . Th i s

d i f f e rence o f 1 MPa i s omiss i b l e . F rom the resu l t s i t can be

seen t ha t i n t e rg r i nd i ng t ime shou ld no t be sho r t e r t han 1 .5

hou rs .

05

101520253035404550


Days

Com

pres

sive

str

engt

h M

Pa 30 min

1 hour

1.5 hours

2 hours

2.5 hours

4 hours

Cement (2 hrs)

F i gu re 6 .16 Compress i ve S t reng th f o r i n t e rg r i nd i ng gas i f i ca t i on

ash and cemen t f o r d i f f e ren t g r i nd i ng t imes

F rom th e s t r eng th c l ass r equ i r emen ts i n Tab le 6 .7 t he

d i f f e rence i n i n t e rb l end ing and i n t e rg r i nd i ng can be obse rved i n

t e rms o f s t r eng th . G r i nd ing t imes sho r t e r t han 30 m i nu tes f o r

i n t e rg r i nd i ng d i d no t ach ieve s t r eng ths f o r an accep tab le


6-23

s t reng th c l ass . The same s t r eng th c l ass we re ach ieved f o r

g r i nd i ng 1 , 1 . 5 , 2 and 4 hou rs . Fo r i n t e rg r i nd i ng t he 2 .5 hou r

g r i nd i ng ach ieved a l owe r s t r eng th c l ass t han w i t h t he

i n t e rb l end ing a t 32 .5 R . T h i s i s s im i l a r t o t he 1 and 1 .5 hou r

g r i nd i ng t ime s t r eng th c l as s . A cemen t s t r eng th c l ass o f 42 .5 R

was p roduced f o r 2 hou rs g r i nd i ng t ime an d f o r g r i nd i ng 4

hou rs cemen t w i t h a s t r eng th c l ass o f 42 .5 N was ach ieved .

When cons ide ra t i on i s g i ven t o t he cemen t g r i nded fo r 2 hou rs

and no t i n t e rb l ended , i t i s c l ea r t ha t gas i f i ca t i on as h had a

con t r i bu t i on t o t he ea r l y s t r eng th deve lopme n t o f t he mo r ta r

p r i sms .

Tab le 6 .8 a l so i nd i ca tes t he pe rcen tage o f 28 day s t r eng th

ga ined a f t e r 7 days , wh i ch i nd i ca tes t ha t a t l eas t 70% o f t he

s t r eng th i s ac h ieved a f t e r 7 days f o r a l l t he m i xes .

I n t e rg r i nd i ng ach ieved a f as te r r a te o f s t r eng th deve lopmen t

a f t e r 7 days t han t he i n t e rb l end ing m ixes (Tab le 6 .6 ) .

Tab le 6 .8 S t reng th c l asses fo r i n t e rg r i nd i ng m i xes g r i nd i ng t ime

30 min 1

hour 1.5

hours 2

hours2.5

hours 4

hours cement (2hrs)

Strength class

N/A to 32.5 N 32.5R 32.5R 42.5 R 32.5 R 42.5 N 42.5 N

Percentage strength


71% 75% 73% 75% 76% 73% 70%

6 .5 .2 Mor ta r P r ism F lexura l S t reng th

The f l exu ra l s t r eng ths o f i n t e rg r i nd i ng i n F i gu re 6 .17 i nd i ca te

t ha t g r i nd i ng t imes l onge r t han 1 .5 hou rs ach ieved h i ghe r

f l e xu ra l s t r eng ths (Append i x F ) . The d i f f e rence i n f l e xu ra l

s t r eng ths i s l ess than 1 MPa . The g raph i nd i ca tes t ha t a l t hough

t he d i f f e rence i n f l e xu ra l s t r eng t h i s om iss i b l e , g r i nd i ng t imes

l onge r t han 1 .5 hou rs ach ieved g rea te r f l e xu ra l s t r eng ths and

t hus g r i nd i ng f o r l e ss t han 1 .5 hou rs i s no t adv i sab le .


6-24

0123456789

10


Days

Flex

ural

str

engt

h M

Pa 30 min

1 hour1.5 hours

2 hours

2.5 hours4 hours

Cement (2 hrs)

F i gu re 6 .17 F lexu ra l s t r eng ths f o r i n te rg r i nd i ng gas i f i ca t i on ash

and cemen t


ach ieved by t he f l e xu ra l s t r eng th a f t e r 28 days f o r i n t e rg r i nd i ng .

A l l o f t he m i xes had a f l e xu ra l s t r eng th o f a t l eas t 20% o f t he

compress i ve s t r eng th , wh i ch i s h i ghe r t han t he expec ted 10%.

The l owes t pe rcen tage i s ac h ieved by t he cemen t on l y m i x . The

resu l t s i nd i ca te t ha t i n t e rg r i nd i ng gas i f i ca t i on ash and cemen t

ach ieved be t t e r f l exu ra l s t r eng ths t han a cemen t on l y m i x .


i n t e rg r i nd i ng

30 min 1

hour 1.5

hours 2

hours2.5

hours 4

hours cement (2hrs)

Percentage of

compressive strength achieved

26% 24% 22% 20% 22% 20% 18%





6-25




The g raph i nd i ca tes t ha t compress i ve s t r eng th i nc rease w i th

dec reas ing pos i t i on pa rame te r s (X o ) f o r i n t e rg r i nd i ng o f cemen t

c l i n ke r and gas i f i ca t i on ash . Thus f i ne r pa r t i c l e ach ieved

g rea te r s t r eng ths . I t can be seen i n F i gu re 6 .18 t ha t f o r

g r i nd i ng t imes l onge r t han 2 hou rs the pos i t i on pa rame te r (X o )

dec reases s l i gh t l y wh i l e no s i gn i f i can t i n c rease i n compress i ve

s t r eng th i s obse rved .

0

10

20

30

40

50

0 10 20 30 40 50 60


Com

pres

sive

Str

engt

h M

Pa

IG,30 min

IG,1hr

IG, 1.5hrIG, 2hr

IG, 2.5hr

IG, 4hr

F i gu re 6 .18 Re la t i on compress i ve s t r eng ths and Ros in -Rammle r

d i s t r i bu t i on pos i t i on pa rame te r ( X o ) f o r i n t e rg r i nd ing

gas i f i ca t i on ash and cemen t

F i gu re 6 .19 i nd i ca tes t ha t pos i t i on pa rame te r s l a rge r t han

20μm ac h ieved cons ide rab l y l owe r compress i ve s t r eng ths .

The re was a cons ide rab le i nc rease i n compress i ve s t r eng th

f r om 30μm to 20μm. The h i ghes t s t r eng ths we re r eached a t

20μm an d 16μm. The 30 -3µm used by cemen t manu fac tu re r s as

a l im i t on f i neness , e f f ec t i ve l y show tha t a f t e r 1 .5 hou rs t he %

pa r t i c l e a lmos t r ema ined cons tan t (Tab le 6 .3 ) as d i d t he

compress i ve s t r eng th . F rom the g raph i t seems as i f a peak i s

r eached a t 20μm. I t i s t hus conc luded t ha t 20μm, an d t hus 2


6-26

hou rs i s an op t imum when pos i t i on pa rame te r s i s compa red t o

t he compress i ve s t r eng th .

0

10

20

30

40

50

0.97 0.975 0.98 0.985 0.99 0.995 1

Slope (n )

Com

pres

sive

str

engt

h (M

Pa)

IG,30 min

IG,1hrIG, 1.5hr

IG, 2hr

IG, 2.5hrIG, 4hr

F i gu re 6 .19 Re la t i on be tween 28 -day compre ss ion s t reng ths

and Ros in -Ramml e r d i s t r i bu t i on s l ope ( n ) pa rame te r


day compress ion s t r eng th . F rom th i s g raph i t seems t ha t w i t h

i nc reased g r i nd i ng t ime t he s l ope (n ) dec rease and t he

compress i on s t r eng ths i nc rease . The sma l l es t s l ope , a f t e r 4

hou rs g r i nd i ng had t he g rea tes t compress i on s t r eng th . Aga in

t he d i f f e rence i n compress ion s t r eng th be tween t he 2 and 4

hou r g r i nd i ng t ime i s sma l l and op t ima l l y t he 2 hou r g r i nd i ng

t ime i s mos t e f f ec t i ve when s t r eng th , pa r t i c l e s i ze and cos t o f

g r i nd i ng i s cons ide red .






6-27

25

30

35

40

45

50

0 20 40 60 80 100 120


28-D

ay C

ompr

essi

ve S

tren

gth

(MPa

)

IG,30 min

IG,1hr

IG, 1.5hr

IG, 2hr

IG, 2.5hr

IG, 4hr

F i gu re 6 .20 Re la t i on be tween 28 -day compress ion s t reng th and

pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s

D50 D10


compress ion s t r eng th i nc reases . As t he 10% l a rges t pa r t i c l e

s i ze f o r d i f f e ren t g r i nd i ng t imes become sma l l e r compress i ve

s t r eng ths a l so i nc reases . I t i s i n te res t i ng t o no te tha t t he

d i s t r i bu t i on cu r ves conve rge , i nd i ca t i ng t ha t t he pa r t i c l e s i zes

become sma l l e r and more u n i f o rm i n s i ze a t h i ghe r s t r eng ths .

A f t e r 4 h ou rs g r i nd i ng t he ma x imu m compress i ve s t r eng th i s

ob ta i ned . Howeve r t he compress i ve s t r eng th d i f f e rence

be tween 4 hou rs and 2 hou rs i s sma l l and t hus an op t imum

l im i t i s r eached a f t e r 2 ho u rs g r i nd i ng f o r bo th t he 50% and

10% l a rges t pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s .

6 .6 EFFECT OF GYPSUM CONTENT ON THE PROPERTIES OF INTER GR OUN D GASIF ICA T ION A S H AND C EME NT


F igu re 6 .21 shows t he compress i ve r esu l t s f o r d i f f e ren t gypsum

con ten t s . See App end i x G f o r a summary o f t he s t r eng ths . The

h i ghes t compress i ve s t r eng th i s ach ieved by 3% gypsum

con ten t bu t t he d i f f e rence i n compress i ve s t r eng th f o r t he

d i f f e ren t gypsum con ten t s i s no t s i gn i f i can t . A l l o f t he m i xes


6-28

can be c l ass i f i ed as 32 .5R i n s t r eng th c l ass . F rom th e resu l t s

t he re i s no c l ea r i nd i ca t i on t ha t t he re i s an op t imum gypsum

con ten t .

0

5

10

15

20

25

30

35

40

45

2 Days 7 Days 28 Days

Days

Com

pres

sive

Str

engt

h M

Pa

0%

0.50%

1%

1.50%

2%

2.50%

3%

F igu re 6 .21 Compress i ve s t r eng ths fo r gypsum con ten t


The f l exu ra l s t r eng ths (Append i x G ) f o r d i f f e ren t gypsum

con ten t s can be seen i n F i gu re 6 .22 . A l l o f t he m i xe s we re a

b l end o f 35% gas i f i ca t i on ash , i n t e rg r i nded w i t h cemen t . A f t e r

28 days t he h i ghes t compress i ve s t r eng th i s ach ieved by 2%

gypsum c on ten t . The d i f f e rence i n compress i ve s t r eng th f o r t he

d i f f e ren t m i xes i s sma l l . F rom the f l e xu ra l s t r eng th r esu l t s

t he re i s no c l ea r i nd i ca t i on t ha t t he re i s an op t imum gypsum

con ten t .


6-29

012345

6789

10


Days

Flex

ural

Str

engt

h M

Pa 0%

0.50%

1%

1.50%

2%

2.50%3%

F igu re 6 .22 F lexu ra l s t r eng ths f o r gypsum con ten t

6 .6 .3 Hea t o f Hyd ra t io n

F igu re 6 .23 shows t he ra te o f hea t deve lopmen t f o r d i f f e ren t

gypsum pe rcen tages . F rom the g raph i t i s obse rved t ha t t he

f i r s t peak ( i n i t i a l r eac t i on ) i s de layed f o r l ow pe rcen tages o f

gypsum. A l l t he f i r s t peaks f o r t he gypsum pe rcen tages have a

l owe r hea t evo lu t i on t han t he re fe rence 100% cemen t m i x . A

3% rep lacemen t o f gypsum peaks a t t he same t ime as t he 100%

cemen t , howeve r a t a l ower hea t evo lu t i on . Fo r a l l t he cu r ves i t

i s obse rved t ha t t he cu r ves a re smoo th and no shou lde rs i s

obse rved a f t e r t he f i r s t hea t peak wh i ch wou ld i nd i ca te f l a sh o r

f a l se se t . The du ra t i on f o r t es t i ng was 36 hou rs and res t r i c t s

t he comp le te cu r ve o f hyd ra t i on .


6-30

0

0.5

1

1.5

2

2.5

0.02 3 6 8 11 14 17 19 22 25 28 30 33 36

Time (hrs)

dQ/d

t (m

wat

ts/g

.sec

)

1 cem 0% gypsum 1 cem 0.5% gypsum 1 cem 1% gypsum 1 cem 1.5% gypsum1 cem 2% gypsum 1 cem 2.5% gypsum 1 cem 3% gypsum Cement 100%

F igu re 6 .23 Ra te o f hea t deve lopmen t f o r d i f f e ren t gypsum

pe rcen tages

F i gu re 6 .24 rep resen t s t he evo lu t i on o f t he hyd ra t i on hea t o f

mo r ta r s made w i t h t he d i f f e ren t pe r cen t o f gypsum su bs t i t u t i on

r e l a t i ve t o 100% PC mor t a r , w i t h a r e fe rence po in t o f ze ro

be ing ass i gned t o t he hyd ra t i on hea t deve loped by t h e 100%

PC mor ta r . Th i s r ep resen ta t i on o f t he da ta shows c l ea r l y t he

e f f ec t o f d i f f e ren t pe r cen tages o f gypsum on t he hea t

deve lopmen t . Low pe rcen tages o f gypsum dec rease t he hea t

ou tpu t a f t e r t he i nduc t i on pe r i od . The hea t d i f f e rence w i th

r espec t t o t he pu re cemen t pas te i s pos i t i ve f o r t hes e m ixes

a f t e r t he i nduc t i on pe r i od . Fo r h i ghe r gypsum pe rcen tages t he

i n i t i a l hea t ou tpu t i s l e ss t han f o r l ow gypsum pe rcen tages .

A f t e r t he i nduc t i on pe r i od t he hea t d i f f e rence f o r t he h i ghe r

gypsum pe rcen tages as nega t i ve . H ighe r gypsum p e rcen tages

seem to have a cons tan t hea t ou tpu t a f t e r t he i nduc t i on pe r i od .


6-31

-1.8

0

1.80.

02 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32 34 36

Time (hours)

Δ (d

Q/d

t)

1 cem 0% gypsum 1 cem 0.5% gypsum 1 cem 1% gypsum1 cem 1.5% gypsum 1 cem 2% gypsum 1 cem 2.5% gypsum1 cem 3% gypsum

F igu re 6 .24 The d i f f e rence i n t he r a te o f hea t evo lu t i on f o r

d i f f e ren t gypsum p e rcen tages cemen t and pu re PC cemen t

Th i s was f u r t he r con f i rmed by t he p l o t t i ng t he t o ta l hea t

evo l ved w i t h t ime i n F i gu re 6 .25 . The t o ta l hea t evo l ved a t t h e

f i r s t 10 hou rs i nc reased w i t h dec reas ing gypsum con ten t s .

A f t e r 10 hou rs t he pu re cemen t has a cons ide rab le i nc rease i n

hea t whe re l ow gypsum pe rcen tages dec rease the hea t

evo lu t i on . H ighe r gypsum pe rcen tages have a cons tan t hea t

evo lu t i on wh i ch i s l owe r t han t he pu re cemen t . F rom the resu l t s

i t i s c l ea r l y obse rved t ha t gypsum d ec rease the hea t evo lu t i on

o f cemen t pas tes . Th i s i s t r ue f o r t he sma l l es t pe r cen tages o f

gypsum. The re i s no c l ea r i nd i ca t i on t ha t gypsum pe rcen tages

cons ide rab l y enha nce t he hyd ra t i on o f cemen t . I t can be

deduced t ha t a 2 .5% gypsum add i t i on i s a good ave ra ge t o use

i n f u r t he r t es t i ng when hea t o f hyd ra t i on and compress i ve

s t r eng th i s cons ide red .


6-32

0

40

80

120

160

200

240

0 10 20 30 40

Time (hours)

Q (m

Wat

ss/g

)

Cum 0%

Cum 0.5%

Cum 1%

Cum 1.5%

Cum 2%

Cum 2.5%

Cum 3%

Cum cement

F igu re 6 .25 To ta l hea t o f hyd ra t i on o f d i f f e ren t gypsum

pe rcen tage cemen ts a t 25 ºC

6 . 7 EFFECT OF REPL ACE MENT LEVEL ON THE PROPERTIES OF

INTER GR OUN D GASIF ICA T ION A S H AND C EME NT 6 .7 .1 Mor ta r P r ism Co mpress ive S t reng th

F i gu re 6 .26 shows t he r esu l t s f o r gas i f i ca t i on ash and cemen t

c l i n ke r i n t e rg round f o r d i f f e ren t r ep lacemen t l eve l s . See

Append i x H f o r summary o f s t r eng th r esu l t s . The resu l t s

i nd i ca te tha t a r ep lacemen t l eve l o f 10% ach ieved t he h i ghes t

compress i ve s t r eng th . Rep lacemen t l eve l s mo re t han 10% we re

g radua l l y l owe r i n compress i ve s t r eng th . Rep lac i ng 10% o f

cemen t w i t h gas i f i ca t i on ash ach ieved a h i ghe r compress i ve

s t r eng th t han t he m i x w i t h 0% rep lacemen t . T h i s c l ea r l y

i nd i ca tes t ha t gas i f i ca t i on ash rep l acemen t can i nc rease t he

compress i ve s t r eng th o f mo r ta r pas tes . The d i f f e rence i n

compress i ve s t r eng th be tween 35% and 55% i s app rox ima te l y

15MPa , wh i ch i s cons ide rab le . F rom the resu l t s i t can be seen

t ha t a 10% rep lacemen t o f gas i f i ca t i on ash had t he h i ghes t

compress i ve s t r eng th . The 20% and 35% rep lacemen t ha d

l owe r compress i ve s t r eng ths bu t was s t i l l cons ide red as

su f f i c i en t f o r use i n cemen t . A r ep l acemen t o f 55% had l ow


6-33

compress i ve s t r eng ths and i s no t r ecommende d as a

r ep lacemen t f o r cemen t .

010203040506070


Days

Com

pres

sive

Str

engt

h M

Pa0%

10%

20%

35%

55%

F igu re 6 .26 Compress i ve s t r eng th f o r d i f f e ren t r ep lacemen t

l eve l s o f gas i f i ca t i on ash


d i f f e rence i n r ep lacemen t l eve l can be obse rved i n t e rms o f

s t r eng th . Rep lacemen t l eve l s o f 0% to 20% ach ieved t he same

s t r eng th c l ass , 52 .5N . The 35% rep lacemen t ach ieved

s t r eng ths f o r a l owe r s t r eng th c l as s , 42 .5N . The 55% d id no t

ach ieve a compress i ve s t reng th t o be c l ass i f i ed . The resu l t s

i nd i ca te t ha t gas i f i ca t i on ash rep lac emen t has no de t r imen ta l

e f f ec t on t he compress i ve s t r eng th deve lopmen t o f cemen t

pas te . Low rep lacemen t l eve l s ach ieved h i ghe r compress i ve

s t r eng ths t han h i gh rep lacemen t l eve l s .


ga ined a f t e r 7 days , wh i ch i nd i ca tes t ha t a t l eas t 75% o f t he

s t r eng th i s ach ieved a f t e r 7 days f o r m i xes w i t h a r ep lacemen t

l eve l be tween 0% and 35%. The 10% and 20% rep lacemen t

l eve l ach ieved a fas te r r a te o f s t r eng th deve lopmen t a f t e r 7

days t han t he 0% rep lacemen t l eve l . The 55% rep lacemen t

l eve l ach ieved l owe r s t r eng th deve lopmen t t han t he expec ted

70%.


6-34

Tab le 6 .10 S t reng th c l asses f o r d i f f e ren t r ep lacemen t l eve l s o f

gas i f i ca t i on ash

0% 10% 20% 35% 55%

Strength class 52.5 N 52.5 N 52.5 N 42.5 N N/A to 32.5N

Percentage strength


83% 87% 85% 75% 58%


The f l exu ra l s t r eng ths (Append i x H ) o f d i f f e ren t r ep lacemen t

l eve l s o f gas i f i ca t i on ash i n F i gu re 6 .27 i nd i ca te t ha t

r ep lacemen t l eve l s l owe r t han 35% ach ieved h i ghe r f l e xu ra l

s t r eng ths . The d i f f e rence i n f l e xu ra l s t r eng ths i s app rox ima te l y

1 MPa . The g raph i nd i ca tes t ha t a l t hough t he d i f f e rence i n

f l e xu ra l s t r eng th i s sma l l , r ep l acemen t l eve l s l ess t han 35%

ach ieved g rea te r f l e xu ra l s t r eng ths and t hus a 55%

rep lacemen t l eve l i s no t adv i sab le .

0.02.04.06.08.0

10.012.0

Tension 2 Days 7 Days

Days

Flex

ural

Str

engt

h M

Pa

0%

10%20%

35%

55%

F igu re 6 .27 F lexu ra l s t r eng ths f o r d i f f e ren t r ep lacemen t l eve l s

o f gas i f i ca t i on ash


6-35


ach ieved by t he f l e xu ra l s t r eng th a f t e r 28 days f o r i n t e rg r i nd i ng .

A l l o f t he m i xes had a f l e xu ra l s t r eng th o f a t l eas t 20% o f t he

compress i ve s t r eng th , wh i ch i s h i ghe r t han t he expec ted 10%.

The cemen t on l y m i x seen i n Tab le 6 .7 and 6 .9 had a

pe rcen tage o f 18% wh i l e t he 0% rep lacemen t was 17%. The

ra t i o va r i ed w i t h r epea t i ng and f u r t he r t es t i ng shou ld be done

t o es tab l i sh l im i t s on t he s t r eng ths . The l owes t pe rcen tage i s

ach ieved by t he cemen t on l y m i x . The resu l t s i nd i ca te t ha t

i n t e rg r i nd i ng gas i f i ca t i on ash and cemen t ach ieved be t t e r

f l e xu ra l s t r eng ths than a cemen t on l y m i x .


d i f f e ren t r ep l acemen t l eve l s o f gas i f i ca t i on ash

0% 10% 20% 35% 55%

Percentage of compressive

strength achieved

17% 17% 18% 22% 26%







The g raph i nd i ca tes t ha t compress i ve s t r eng th dec rease w i t h

dec reas ing pos i t i on pa rame te r s (X o ) f o r r ep lacemen t l eve l s o f

gas i f i ca t i on ash . I t can be seen i n F i gu re 6 .28 t ha t f o r a 10%

rep lacemen t l eve l o f gas i f i ca t i on as h t he pos i t i on pa rame te r

(X o ) i s sma l l e r t han t he 0% rep lacemen t . Rep lacemen t l eve l s o f

20% and 55% had t he same pos i t i on pa rame te r (Xo ) as t he 10%

rep lacemen t l eve l , bu t w i t h l owe r compress i ve s t r eng ths . The

35% rep lacemen t l eve l had a sma l l e r pos i t i on pa rame te r ( Xo )


6-36

than t he o the r r ep l acemen t l eve l s . The re i s no i nd i ca t i on t ha t

f i ne r pa r t i c l e ach ieved g rea te r s t r eng ths .

010203040506070

0 10 20 30 40


Com

pres

sive

Str

engt

h M

Pa0%

10%

20%

35%

55%


d i s t r i bu t i on pos i t i on pa rame te r (X o ) f o r r ep lacemen t l eve l s o f


F i gu re 6 .28 i nd i ca tes t ha t t he re i s no s i gn i f i can t i nd i ca t i on t ha t

pos i t i on pa rame te r s had an e f f ec t on t he compress i ve s t r eng th

deve lopmen t o f t he mo r ta r m i xes .

010203040506070

0.1 0.3 0.5 0.7 0.9 1.1

Slope n

Com

pres

sive

Str

engt

h M

Pa

0%

10%

20%

35%

55%

F igu re 6 .29 Re la t i on be tween 28 -day compre ss ion s t reng ths

and Ros in -Ramml e r d i s t r i bu t i on s l ope ( n ) pa rame te r


day compress ion s t r eng th . F rom th i s g raph i t seems t ha t t he


6-37

s lope (n ) i s app rox ima te l y 1 f o r a l l t he r ep lac emen t l eve l s o f

gas i f i ca t i on ash bu t 0%. T he compress i ve s t r eng th dec reased

f o r d i f f e ren t r ep lac emen t l eve l wh i l e t he s l ope ( n ) r ema ined t he

same . The re i s no s i gn i f i can t i nd i ca t i on t ha t t he s l ope (n ) had

an e f f ec t on t he compress i ve s t r eng th o f t he mo r ta r m i xes .





010203040506070

0 20 40 60 80 100


Com

pres

sive

Str

engt

h M

Pa

0%

10%

20%

35%

55%

D50 D10

F igu re 6 .30 Re la t i on be tween 28 -day compre ss ion s t reng th and

pa r t i c l e s i ze d i s t r i bu t i on pa rame te r s o f r ep l acemen t l eve l o f



compress ion s t r eng th dec reases . As t he 10% l a rges t pa r t i c l e

s i ze fo r d i f f e ren t r ep lac emen t l eve l s become sma l l e r

compress i ve s t r eng ths a l so dec reases . I t i s howeve r

i n t e res t i ng t o no te t ha t t he re i s no c l ea r i nd i ca t i on t ha t t he

ave rage pa r t i c l e s i ze o r t he 10% l a rges t pa r t i c l e s i ze becomes

sma l l e r f o r d i f f e ren t r ep lacemen t l e ve l s . The ave rage pa r t i c l e

s i ze f o r t he d i f f e ren t r ep lac emen t l eve l s r ange be twe en 15µm

and 20µm, wh i l e t he 10% l a rges t pa r t i c l e s i ze r ange be tween

40µm an d 95µm. F rom the g raph t he re i s no op t imum l im i t f o r


6-38

bo th t he 50% and 10% l a rges t pa r t i c l e s i ze d i s t r i bu t i on

pa rame te rs .

6 .8 COMPA R ISON BE TWEEN MAN UFA CTURE D AND COMMER CIAL CE MENT


The cemen t manu fac tu red i n t he l ab was compa red t o

commerc ia l l y ava i l ab l e CEM I 42 .5R . See Append i x I f o r a

summary o f s t reng ths . The cemen t manu fac tu red i n t he

l abo ra to r y was e i t he r i n t e rb l ended ( i n t e rb l end i n m i xe r ) o r

i n t e rg round ( i n t e rb l end i n ba l l m i l l and g round t oge the r ) f o r 2

hou rs w i th a 2 .5% gypsum con ten t . F i gu re 6 .31 i nd i ca tes t he

compress i ve s t r eng ths f o r i n t e rb l ended and i n t e rg round cemen t

manu fac tu red i n t he l ab and a commerc i a l l y ava i l ab l e CEM I

42 .5R . F rom the g raph i t i s obse rved t ha t i n te rg r i nd i ng cemen t

and gypsum ach ieved compress i ve s t r eng ths h i ghe r t han t he

CEM I 42 .5R , wh i l e i n t e rb l end ing ac h ieved l owe r compress i ve

s t r eng ths t han t he CEM I 42 .5R .

010203040506070


Days

Com

pres

sive

Str

engt

h M

Pa

IB CEM+GYPSUM IG CEM +GYPSUM CEM I 42.5 R

F igu re 6 .31 Compress i ve s t r eng ths f o r manu fac tu red and

commerc i a l l y ava i l ab l e cemen t


d i f f e rence can be obse rved i n t e rms o f s t r eng th . I n te rb l end ing


6-39

can be c l ass i f i ed as 42 .5N wh i l e i n te rg r i nd i ng i s c l ass i f i ed as

52 .5N .


ga ined a f t e r 7 days , wh i ch i nd i ca tes t ha t i n t e rb l end ing and

i n t e rg r i nd i ng ach ieved a t l eas t 80% o f t he s t reng th a f t e r 7 days .

The CEM I 42 .5 R ach ieved on l y 68% o f i t s s t r eng th

deve lopmen t a f t e r 7 days . F rom the resu l t s i t i s c l ea r t ha t t he

i n t e rg round cemen t manu fac tu red i n t he l ab pe r f o rmed be t t e r

t han a commerc i a l l y ava i l ab l e 42 .5R . The i n t e rb l ended cemen t

manu fac tu red cemen t pe r f o rmed l i ke a 42 .5N bu t had a f as te r

s t r eng th deve lopmen t a f t e r 7 days t han t he 42 .5R .

Tab le 6 .12 S t reng th c l asses f o r d i f f e ren t r ep lacemen t l eve l s o f


IB CEM + Gypsum

IG CEM + Gypsum CEM I 42.5R

Strength class 42.5 N 52.5 N 42.5 R

Percentage strength


82% 80% 68%

6 .8 .2 F lexura l Mor ta r P r ism S t re ng ths

F igu re 6 .32 shows t he f l exu ra l s t r eng ths (Append i x I ) f o r

i n t e rb l ended and i n t e rg round cemen t manu fac tu red i n t he l ab

and a commerc ia l l y ava i l ab l e CEM I 42 .5N . F rom the g raph i t i s

obse rved t ha t i n te rg round cemen t ach ieved s im i l a r f l e xu ra l

s t r eng ths t han t he CEM I 42 .5N .


6-40

02468

1012

2 Days 7 Days 28 DaysDays

Flex

ural

Str

engt

h M

Pa

IB CEM+GYPSUM IG CEM +GYPSUM CEM I 42.5 R

F igu re 6 .32 F lexu ra l s t r eng ths f o r manu fac tu red and



ach ieved by t he f l exu ra l s t r eng th a f t e r 28 days . I n t e rb l end ing

ach ieved t he h i ghes t pe r cen tage o f f l e xu ra l s t r eng th compa red

t o compress i ve s t r eng th . The i n t e rg round and CEM I 42 .5R

m ixes ach ieved sma l l e r pe rcen tages bu t a l l t h ree o f t he m i xes

ach ieved a pe rcen tage h i ghe r t han 10% wh i ch i s expec ted . The

resu l t s i nd i ca te t ha t t he bo th t he i n te rb l ended and i n te rg round

cemen t pe r f o rmed s im i l a r t o t he commerc ia l l y ava i l ab l e CEM I

42 .5R .


d i f f e ren t r ep l acemen t l eve l s o f gas i f i ca t i on ash

IB CEM + Gypsum

IG CEM + Gypsum

CEM I 42.5R

Percentage of compressive

strength achieved

20% 16% 19%


6-41

6 .8 .3 Hea t o f Hyd ra t io n

F igu re 6 .33 shows t he ra te o f hea t deve lopmen t f o r t he

manu fac tu red and commerc i a l l y ava i l ab l e cemen t . F rom the

g raph i t i s obse rved t ha t t he cemen t manu fac tu red i n t he l ab

peak a t t he same t ime as t he CEMI 42 .5R bu t a t a l owe r hea t

evo lu t i on . A f t e r t h e f i r s t peak bo th t he m i xes dec rease w i t hou t

any shou lde rs wh i ch i nd i ca te f l a sh o r f a l se se t . The resu l t s

i nd i ca te t ha t t he cemen t manu fac tu red i n t he l ab pe r f o rmed

s im i l a r t o t he commerc i a l l y ava i l ab l e CEM I 42 .5R bu t l owe r

hea t o f hyd ra t i on t empe ra tu res i s obse rved f o r t he cemen t

manu fac tu red i n t he l ab .

0

0.25

0.5

0.75

1

1.25

1.5

1.75

2

0 5 9 14 18 23 27 32 36 41 45 50 54 59 63 68

Time (hours)

dQ/d

t (m

Wat

ts/g

.sec

)

CEM I 42.5

LAB CEM

F igu re 6 .33 Ra te o f hea t deve lopmen t f o r manu fac tu red and


6 . 9 CONCLUSION

• I t i s obse rved t ha t t he gas i f i ca t i on ash , g r i nded sepa ra te

and i n t e rg round had s im i l a r pa r t i c l e s i ze d i s t r i bu t i ons .

The pa r t i c l e s i ze o f gas i f i ca t i on ash g round sepa ra te l y i s

cons ide rab l y f i ne r t han t ha t o f cemen t g round sepa ra te l y

f o r t he same t ime i n t e r va l . Th i s i nd i ca tes t ha t t he cemen t

c l i n ke r i s ha rde r t han t he gas i f i ca t i on ash c l i n ke r .


6-42

• The pos i t i on pa rame te r (X o ) and t he re fo re t he pa r t i c l e

s i ze d i s t r i bu t i on dec rease as t he g r i nd i ng t ime i nc reases

f o r gas i f i ca t i on ash .

• I t seems as i f an op t imum g r i nd i ng t ime can be

es tab l i shed . Fo r bo th t he i n t e rg r i nd i ng and gas i f i ca t i on

ash t h i s op t imum seems t o be i n t he r eg ion o f 2 hou rs .

• The gas i f i ca t i on as h has no un ique s t r uc tu re and cou ld be

desc r i bed as angu la r .

• The XRF , XR D and chem ica l spec i f i ca t i on r esu l t s i nd i ca te

t ha t gas i f i ca t i on ash shou ld be accep tab le t o use as a

cemen t ex tende r i n conc re te .

• The compress i ve s t r eng th , f l e xu ra l s t r eng th , pa r t i c l e s i ze

and Ros in -Rammle r d i s t r i bu t i on pa rame te rs c l ea r l y

i nd i ca te tha t g r i nd i ng t ime shou ld no t be sho r t e r t han 2

hou rs f o r i n t e rb l end ing and i n t e rg r i nd i ng o f gas i f i ca t i on

ash and cemen t .

• I t can be deduced t ha t a 2 .5% gypsum add i t i on i s a good

ave rage t o use i n f u r t he r t es t i ng when hea t o f hyd ra t i on

and compress i ve s t r eng th a re cons ide red .


and Ros in -Ramml e r d i s t r i bu t i on pa rame te r s con f i rm t ha t

r ep l acemen t l eve l s o f gas i f i ca t i on ash shou ld r ange

be tween 10% and 35%.

• The cemen t manu fac tu red i n t he l abo ra to r y pe r f o rmed

s im i l a r i n s t r eng th deve lopmen t t o t he commerc i a l l y

ava i l ab l e CEM I 42 .5R bu t l owe r hea t o f hyd ra t i on

t empe ra tu res a re obse rved f o r t he cemen t manu fac tu red

i n t he l abo ra to r y .


7-1

7. TEST RESULTS AND DISCUSSION ON CONCRETE TESTS

7 .1 INTRODUCTION

I n chap te r 7 , t he r esu l t s o f t he expe r imen ta l t es t s d i scussed i n

chap te r 5 on conc re te a re r ev i ewe d and ana l ysed t o exam ine

t he reac t i v i t y o f a gas i f i ca t i on ash when used i n conc re te .

The rea f t e r t he r esu l t s o f t he conc re te cas t a re i l l u s t r a ted and

d i scussed . The resu l t s i nc l ude s l ump , compress i on s t r eng th ,

t ens i l e s t r eng th , E - va lue , sh r i nkage , c reep , po ros i t y and

oxygen p e rmeab i l i t y t es t r e su l t s . The d i scuss ion o f t he r esu l t s

t akes i n to cons ide ra t i on t ha t t es t s we re conduc ted on a s i ng l e

se t o f samp les . L im i t a t i ons t o t he t es t i ng me thod w i l l be

d i scussed and poss ib l e imp rovemen ts w i l l be r ecomme nded .

7 .2 TESTS C OND UCT ED ON F RESH CONCRET E 7 .2 .1 S lump Tes t

The s l ump t es t r esu l t s ( as i nd i ca ted i n f i gu re 7 .1 ) i l l us t r a t e t ha t

t he conc re te m i x i n t e rb l ended w i t h f l y ash had t he h i ghes t

s l ump and t hus a h i gh workab i l i t y . I t i s expec ted t ha t due t o

t he f i l l e r e f f ec t s cha rac te r i s t i c o f f l y ash i t w i l l e xh ib i t a s l i gh t l y

l owe red pas te wa te r demand . Th i s i nc reases t he cohes i veness

o f t he m i x wh i ch i mp roves i t s wo rkab i l i t y (Ho l c im , 2005 ) . The

m ixes w i t h gas i f i ca t i on ash we re l ess wo rkab le . Resu l t s

i nd i ca te t ha t t he wa te r deman d o f conc re te con ta i n i ng

gas i f i ca t i on ash i s h i ghe r t han t ha t o f t he m i x i n t e rb l ended w i t h

f l y ash . The s l ump t es t r esu l t s i nd i ca te t ha t t he use o f

gas i f i ca t i on ash as cemen t ex tende r w i l l r esu l t s i n a reduc t i on

i n t he wo rkab i l i t y o f conc re te .


7-2

0

40

80

120

160

200

IG IB FA IB GA

Mixes

Slum

p m

m

F igu re 7 .1 S lump t es t f o r conc re te m i xes

7 .3 STRENGTH TEST S 7 .3 .1 Concre te Cube Co mpress ion Tes t Resu l ts

F i gu re 7 .2 shows t he compress i ve s t r eng th o f t he d i f f e ren t

conc re te m i xes . The h i ghes t s t r eng th was ach ieved by t he

i n t e rg r i nded gas i f i ca t i on ash m i x , bu t t he s t r eng th d i f f e rence i s

no t g rea te r t han 5 MPa f o r a l l t he m i xes a f t e r 28 days ( see

Append i x J ) . The l owes t s t r eng ths we re ach ieved by t he

i n t e rb l end ing w i t h f l y ash . These resu l t s c l ea r l y i nd i ca te t ha t

t he use o f gas i f i ca t i on ash as cemen t ex tende r does no t have a

nega t i ve impac t on t he s t r eng th deve lopmen t o f conc re te .

A f t e r 7 days t he gas i f i ca t i on ash i n te rg r i nded ach ieves a h i gh

compress i ve s t r eng th . Th i s va l ue cou ld s t a t i s t i ca l l y be

cons ide red as an ou t l i e r bu t no t r ends can be conc luded f r om

the resu l t s as on l y one se t o f samp les we re tes ted . Th i s va l ue

v i s i b l y i nd i ca tes tha t mo re t es t i ng shou ld be done so t ha t

s t a t i s t i ca l conc lus i ons cou ld be d rawn abou t t he behav iou r o f

compress i ve s t r eng th o f gas i f i ca t i on .

The compress i ve s t r eng th t es t i s howeve r no t a good i nd i ca to r

o f conc re te du rab i l i t y as no d i r ec t r e l a t i onsh ip ex i s t s be tween


7-3

the two cha rac te r i s t i c s . The qua l i t y o f conc re te , i n t e rms o f

du rab i l i t y , shou ld t he re fo re no t be de duced f r om the

compress i ve s t r eng th , as i s o f t en the case i n t he cons t ruc t i on

i ndus t r y .

05

101520253035

24 hour 7 days 28 days

Time

Com

pres

sive

str

engt

h M

Pa

IG

IB FA

IB GA

F igu re 7 .2 Conc re te cubes compress ion s t r eng th r esu l t s

7 .3 .2 Tens i l e S t reng th Resu l ts

Theo re t i ca l l y t he tens i l e s t reng th i s expec ted t o be 10% o f t he

compress i ve s t r eng th . Resu l t s i n Tab le 7 .1 , shows t ha t t he

t ens i l e s t r eng th o f t he m i xe s was a l l app rox i ma te l y 3 MPa . A l l

o f t he m i xes had a f l e xu ra l s t r eng th t o compress i ve s t r eng th

compa r i son o f 10% to 12%. H ighe r t han 10% fo r t he

i n t e rb l end ing m i xes was due t o a l owe r compress i ve s t r eng th

t han t he i n t e rg r i nd i ng m ix . The f l exu ra l s t r eng th r esu l t s o f

gas i f i ca t i on ash , i n t e rg r i nded o r i n t e rb l ended was marg ina l l y

h i ghe r t han t he m i x i n t e rb l ended w i t h f l y ash . The t ens i l e

r esu l t s a re howeve r w i t h i n 0 .3 MPa o f each o the r and t he re fo re

t he d i f f e rence i s no t cons ide rab le . I n t e rb l end ing w i t h

gas i f i ca t i on ash has a s l i gh t l y h i ghe r t ens i l e s t r eng th t han t he

f l y ash .


7-4

Tab le 7 .1 Tab le compa r i ng t ens i l e and compress i ve s t reng ths

Mixes Tensile strength MPa

Compression Strength MPa Comparison %

IG 3.3 31.5 10%

IB FA 3.02 26.7 11%

IB GA 3.35 28.0 12%

F rom F igu re 7 .3 , i t can be seen t ha t i n t e rb l end ing and

i n t e rg r i nd i ng w i t h gas i f i ca t i on ash ach ieved t he h i ghes t t ens i l e

s t r eng ths . These resu l t s i nd i ca te tha t t he use o f gas i f i ca t i on

ash as cemen t ex tende r does no t r esu l t s i n a r educ t i on i n t he

t ens i l e s t r eng th o f conc re te .

0

1

2

3

4

Mixes

Tens

ile s

tren

gth

MPa

IG

IB FA

IB GA

F igu re 7 .3 Tens i l e s t r eng th r esu l t s f o r conc re te m i xes

7 .4 DEFORMATION A ND V OLU ME C HA NGE OF CON CRE TE 7 .4 .1 E -va lue tes t resu l ts

The e l as t i c modu lus r ep res en t s t he ma te r i a l s t i f f ness o f t he

conc re te t o an imposed s t r ess . F i gu re 7 .4 shows t he ave rage o f

two resu l t s f o r each m ix . The resu l t s f o r t he E -va lue show tha t

i n t e rg r i nd i ng w i t h gas i f i ca t i on ash ach ieved t he h i ghes t


7-5

modu lus o f e l as t i c i t y . I n t e rb l end ing w i t h gas i f i ca t i on ash

ach ieved t he l owes t modu lus o f e l as t i c i t y .

0

10

20

30

40

50

Mixes

Mod

ulus

of E

last

icity

GPa

IGIB FA

IB GA

F igu re 7 .4 E -va lue t es t r esu l t s f o r conc re te m i xes

Gas i f i ca t i on ash i n t e rg r i nded ach ieved a h i ghe r mo du lus o f

e l as t i c i t y t han t h e i n t e rb l end ing m ixes ( see t ab le 7 .2 ) . Th i s

cou ld be due t o t he be t t e r i n t e r f ace o f t he pa r t i c l es a l r eady

m ix i ng when g r i nded t oge the r and due t o t he h i ghe r

compress i ve s t r eng th o f i n t e rg r i nd i ng . The re i s a cons tan t

d i f f e rence o f 2 GPa be tween each o f t he cy l i nde rs f o r a l l t h ree

m i xes . No t r ends can be conc luded f r om the resu l t s as on l y one

se t o f samp les we re t es ted . The h i gh s t i f f ness o f i n t e rg r i nd i ng

gas i f i ca t i on ash i nd i ca tes tha t mo re t es t i ng shou ld be done so

t ha t s t a t i s t i ca l conc lus i ons cou ld be d rawn abou t t he s t i f f ness

o f conc re te when gas i f i ca t i on ash i s i n t e rg r i nded w i t h cemen t .

These resu l t s i nd i ca te t ha t t he use o f gas i f i ca t i on ash as

cemen t ex tende r does no t have a de t r imen ta l e f f ec t on t he

s t i f f ness o f conc re te .


7-6

Tab le 7 .2 E -va lu e resu l t s o f t he d i f f e ren t cy l i nde rs f o r t he

d i f f e ren t m i xes

Mix E-value Cylinder 1

E-value Cylinder 2

IG 38.8 GPa 40.3 GPa

IB FA 37.8 GPa 35.9 GPa

IB GA 35.4 GPa 33 GPa

7 .4 .2 Shr inkage and Creep Tes t

Sh r i nkage i s caused by d r y i ng t he re fo re f ac to r s t ha t con t r i bu te

t o t he d r y i ng o f conc re te such as r e l a t i ve hum id i t y , s i ze and

shape o f t he conc re te member as we l l as t he conc re te m i x

p ropo r t i ons and ma te r i a l s w i l l i n f l uence sh r i nkage .

Tab le 7 .3 i nd i ca tes t he sh r i nkage , c reep and spec i f i c c reep f o r

each o f t he m i xe s a f t e r 309 days . F rom the resu l t s i t i s

obse rved t ha t i n te rg r i nd i ng and i n t e rb l end ing o f gas i f i ca t i on

ash ach ieved h i ghe r sh r i nkage , c reep and spec i f i c c reep

resu l t s t han t he i n t e rb l ended f l y ash m ix . Thes e d i f f e rences a re

on l y ma rg ina l .

Tab le 7 .3 Sh r i nkage , C reep and Spec i f i c C reep Resu l t s f o r t he

d i f f e ren t m i xes

MIX Shrinkage (microstrain)

Creep (microstrain)

Specific Creep (microstrain/Mpa)

IG GA 413.4 830.7 201.1 IB FA 326.8 643.7 169.8

IB GA 378.0 783.5 184.6

P rev i ous s tud ies conduc ted by Badenho rs t ( 2003 ) showed t ha t

f o r a 70 /30 FA b l ended cemen t i t i s expec ted t ha t f o r d i f f e ren t

agg rega te t he sh r i nkage d i f f e r s . A do lom i t e sand and g ran i t e

s t one was used i n t he m i x des ign o f t he conc re te f o r a l l t h ree


7-7

m ixes . G ran i t e has an expec ted sh r i nkage o f 500 m ic ros t r a i n

wh i l e do lom i t e has an expec ted sh r i nkage o f 300 m ic ros t r a i n .

The resu l t s o f t he t h ree m ixes f a l l i n t h i s r ange and t hus t he

d i f f e rence i n sh r i nkage fo r t he m i xes i s no t cons ide rab le .

F i gu res 7 .5 , 7 . 6 and 7 .7 i nd i ca te t he sh r i nkage and c reep f o r

each o f t he t h ree m ixes . The resu l t s f o r sh r i nkage i nd i ca te t he

gas i f i ca t i on ash d i d no t sh r i nk s i gn i f i can t l y mo re t han f l y ash .

IG GA73 kN Load; 55% to 60% RH; 25oC

0100200300400500600700800900

1000

0 50 100 150 200 250 300 350

Time (days)

Def

orm

atio

n (m

icro

stra

in)

CreepCreepShrinkage

F igu re 7 .5 Sh r i nkage and c reep resu l t s f o r i n t e rg round

gas i f i ca t i on ash m ix


7-8

IB FA67 kN Load; 55% to 60% RH; 25oC

0100200300400500600700800900

1000

0 50 100 150 200 250 300 350

Time (days)

Def

orm

atio

n (m

icro

stra

in)

Creep

Creep

Shrinkage

F igu re 7 .6 Sh r i nkage and c reep resu l t s f o r i n te rb l ended f l y ash

m ix

IB GA 75 kN Load; 55% to 60% RH; 25oC

0100200300400500600700800900

1000

0 50 100 150 200 250 300 350

Time (days)

Def

orm

atio

n (m

icro

stra

in) Creep

Creep

Shrinkage

F i gu re 7 .7 Sh r i nkage and c reep resu l t s f o r i n t e rb l ended

gas i f i ca t i on ash m ix

C reep o f conc re te i s l oad i nduced , and i s i n f l uenced by f ac to r s

assoc ia ted w i t h t he app l i ca t i on o f l oad and the ab i l i t y o f t he

conc re te t o w i t hs tand t he l oad . The po ten t i a l o f t he conc re te t o

c reep i s de te rm ined by m i x ma te r i a l s and p ropo r t i ons o f t he

conc re te .


7-9

Tab le 7 .3 i nd i ca te t ha t i n t e rg round and i n t e rb l ended

gas i f i ca t i on ash m ixes had h i ghe r c reep va lues t han t he

i n t e rb l ended f l y ash m ix . T he d i f f e rence i n t he c reep va lues a re

howeve r no t cons ide rab le ( see f i gu re 7 .5 , 7 . 6 and 7 .7 ) . The

resu l t s f o r c reep i nd i ca te t he gas i f i ca t i on ash d i d no t c reep

s i gn i f i can t l y mo re t han f l y ash .

F i gu re 7 .8 i nd i ca te t he spec i f i c c reep (See Append i x K ) f o r t he

t h ree m ixes . I t i s obse rved t ha t ove r t ime t h e spec i f i c c reep f o r

t he t h ree m ixes i s app rox i ma te l y t h e same . The spec i f i c c reep

resu l t s i nd i ca te tha t gas i f i ca t i on as h has a spec i f i c c reep

s im i l a r t o f l y ash .

55% to 60% RH; 25oC

0

50

100

150

200

250

300

0 50 100 150 200 250 300 350

Time (days)

Spec

ific

Cre

ep

(mic

rost

rain

/ M

Pa)

IG GA

IB FAIB GA

F igu re 7 .8 Spec i f i c c reep resu l t s f o r t he t h ree d i f f e ren t m i xes

7 .5 DURABIL ITY TEST S 7 .5 .1 Poros i ty Tes t Resu l ts

I t can be obse rved f r om F i gu re 7 .7 t ha t f o r i n t e rb l end ing t he

po ros i t y o f t he gas i f i ca t i on ash was l owe r t han f l y ash . Th i s i s

due t o a f i ne r pa r t i c l e s i ze o f t he gas i f i ca t i on ash t han t he f l y

ash , wh i ch r esu l t s i n a mo re even d i s t r i bu t i on o f so l i d pa r t i c l es

i n t he conc re te .


7-10

The conc re te m i x i n t e rb l ended w i t h f l y ash has t he h i ghes t

po ros i t y , wh i ch shows tha t t he cemen t pa r t i c l es d i d no t

d i spe rse un i f o rm l y t h rough the wa te r r esu l t i ng i n

agg lomera t i ons and l eav i ng l a rge spaces wh i ch do no t con ta i n

cemen t . These spaces f o rm cap i l l a r y po re s and en t ra i n a i r .

The resu l t o f t h i s i s a l owe r s t r eng th o f t he conc re te . The

i n t e rg r i nd i ng w i t h f l y ash had a f i ne r pa r t i c l e s i ze and resu l t s i n

a l owe r po ros i t y . I n t e rb l end ing w i t h gas i f i ca t i on as h had a

s l i gh t l y h i ghe r po ros i t y t han t he i n t e rg r i nd i ng w i t h gas i f i ca t i on

ash ; t h i s cou ld be due t o be t t e r i n t e r l ock i ng o f pa r t i c l es

g r i nded toge the r . See Append i x L f o r Po ros i t y summary .

The d i f f e rence i n po ros i t y be tween a l l t h ree m ixes i s be tween

15% and 16%. Po ros i t y va l ues (B r i t i sh Conc re te Soc ie t y , 2000 )

f o r a h i gh l y po rous conc re te i s g rea te r t han 15%. A l t h ree o f

t he m ixe s f a l l i n to t h i s ca tego ry and t hus t he d i f f e rence i n

r esu l t s i s om iss i b l e . The resu l t s i nd i ca te t ha t t he use o f

gas i f i ca t i on ash as cemen t ex tende r does no t r esu l t s i n an

i nc rease i n po ros i t y . I t i s t he re fo re an t i c i pa ted t ha t t he

conc re te con ta i n ing gas i f i c a t i on ash w i l l be no l ess du rab le

t han conc re te cu r ren t l y man u fac tu red .

0%

6%

12%

18%

Mixes

Poro

sity

% IG

IB FAIB GA


7-11

F igu re 7 .7 Po ros i t y r esu l t s o f conc re te m i xes

7 .5 .2 Ox ygen Permeab i l i t y Tes t Resu l ts

The resu l t s o f t he pe rmeab i l i t y t es t (as i nd i ca ted i n f i gu re 7 .8 )

show tha t t he t ype o f ash used d i d no t a f f ec t t he pe rmeab i l i t y

o f m i xes . The m ix i n t e rb l ended w i t h f l y ash ac h ieved the l owes t

pe rmeab i l i t y . H igh pe rmeab i l i t y i s due t o a poo r qua l i t y o f

cemen t pas te -agg rega te i n te r f ace . F l y ash has t he e f f ec t o f

r educ ing t he pe rmeab i l i t y , wh i ch i s obse rved f r om the resu l t s .

I n t e rg r i nd i ng had t he h i ghes t pe rmeab i l i t y and wou ld abso rb

t he mos t wa te r . See Append i x M f o r Pe rmeab i l i t y ca l cu l a t i ons .

0

2E-21

4E-21

6E-21

8E-21

1E-20

1.2E-20

Mixes

Perm

eabi

lity

(m/s

)

IG

IB FA

IB GA

F igu re 7 .8 Oxygen pe rmeab i l i t y t es t resu l t s f o r conc re te m i xes

Pe rmeab i l i t y va l ues (B r i t i sh Conc re te Soc ie t y , 2000 ) f o r a good

qua l i t y conc re te w i t h a l ow pe rmea b i l i t y i s sma l l e r t han 2 x 10 -

1 8 and a l l o f t he resu l t s f a l l i n t o t h i s ca tego ry . OP I va l ues as

seen i n F i gu re 7 .9 i nd i ca te an exce l l en t c l ass o f du rab i l i t y f o r

conc re te w i t h a g rea te r t han 10 OP I (A lexande r , 1999 ) . These

resu l t s i nd i ca te tha t t he use o f gas i f i ca t i on ash i n conc re te

ach ieves a l ow pe rmeab i l i t y and a du rab le conc re te can be

expec ted .


7-12

0

6

12

18

24

Mixes

Oxy

gen

perm

eabi

lity

inde

xIG

IB FA

IB GA

F igu re 7 .9 Oxygen pe rmeab i l i t y i ndex resu l t s f o r t he conc re te

m ixes .

7 . 6 CONCLUSION

• The use o f gas i f i ca t i on as h as a cemen t ex tende r i n

conc re te wou ld have eco log i ca l and econom ica l bene f i t s

i n t he cemen t i ndus t r y .

• The s l ump t es t r esu l t s i nd i ca te t ha t t he use o f

gas i f i ca t i on ash as cemen t ex tende r w i l l r esu l t s i n a

r educ t i on i n t he wo rkab i l i t y o f conc re te .

• The use o f gas i f i ca t i on ash as cemen t ex tend e r does no t

have a n ega t i ve impac t on t he s t r eng th deve lopmen t o f

conc re te . The re was no reduc t i on i n t he t ens i l e s t r eng th

o f conc re te .


have a de t r imen ta l e f f ec t on t he s t i f f ness o f conc re te .

• The resu l t s f o r sh r i nkage i nd i ca te t he gas i f i ca t i on ash d i d

no t sh r i nk s i gn i f i can t l y mo re t han f l y ash . C reep resu l t s

i nd i ca te tha t gas i f i ca t i on ash d i d no t c reep s i gn i f i can t l y

mo re t han f l y ash . The spec i f i c c reep resu l t s i nd i ca te tha t

gas i f i ca t i on ash has a spec i f i c c reep s im i l a r t o f l y ash .


7-13

• The resu l t s i nd i ca te t ha t t he use o f gas i f i ca t i on ash as

cemen t ex tende r does no t r esu l t s i n an i nc rease i n

po ros i t y . I t i s t he re fo re an t i c i pa ted t ha t t he conc re te

con ta i n i ng gas i f i ca t i on ash w i l l be no l ess du rab le t han

conc re te cu r ren t l y manu fac tu red .

• The use o f gas i f i ca t i on ash i n conc re te ach ieves a l ow

pe rmeab i l i t y and a du rab le conc re te can be expec ted .


8-1

8. CONCLUSIONS AND RECOMMENDATIONS 8 .1 CONCLUSIONS

The a im o f t he r esea rch i s f u l f i l l ed and exp la i ned by g i v i ng

cons ide ra t i on t o each o f t he f o l l ow ing conc lus i ons .

I nves t i ga t i ng t he phys i ca l , chemica l and m ine ra l og i ca l

compos i t i on o f a gas i f i ca t i on ash samp le had t he fo l l ow ing

resu l t s :

• The gas i f i ca t i on as h has no un ique s t r uc tu re and cou ld be

desc r i bed as angu la r .

• The chem ica l and m i ne ra l og i ca l compos i t i on o f

gas i f i ca t i on ash i nd i ca tes t ha t t he ash have s im i l a r

e l emen ts t han f l y ash and i s w i t h i n t he a l l owab le r ange

f o r use as a cemen t ex tende r i n cemen t and conc re te .

• The phys i ca l p rope r t i es o f gas i f i ca t i on ash i nd i ca ted tha t

t he gas i f i ca t i on ash , g round sepa ra te and i n t e rg round

w i t h cemen t i n t he ba l l m i l l had s im i l a r pa r t i c l e s i ze

d i s t r i bu t i ons . The re i s a cons ide rab le d i f f e rence i n

pa r t i c l e s i ze be tween t he gas i f i ca t i on ash and cemen t

g round sepa ra te l y f o r t h e same t ime i n te r va l . Th i s

i nd i ca tes t ha t t he cemen t c l i n ke r i s ha rde r t han t he

gas i f i ca t i on ash c l i n ke r .

• The pos i t i on pa rame te r (X o ) and t he re fo re t he pa r t i c l e

s i ze d i s t r i bu t i on dec rease as t he g r i nd i ng t ime i nc reases

f o r gas i f i ca t i on ash .

I nves t i ga t i ng t he phys i ca l p rope r t i es o f cemen t manu fac tu r i ng

w i t h spec i f i c r e f e rence t o g r i nd i ng t ime , t he op t im i sa t i on o f

gypsum, spec i f i c su r f ace a rea and pa r t i c l e s i ze d i s t r i bu t i on had

t he f o l l ow ing resu l t s :


8-2

• I t seems as i f an op t imum g r i nd i ng t ime can be

es tab l i shed . Fo r bo th t he i n t e rg r i nd i ng and gas i f i ca t i on

ash t h i s op t imum seems t o be i n t he r eg ion o f 2 hou rs .


and Ros in -Rammle r d i s t r i bu t i on pa rame te r s c l ea r l y

i nd i ca te than g r i nd i ng t ime shou ld no t be sho r t e r t han 2

hou rs f o r i n t e rb l end ing and i n t e rg r i nd i ng o f gas i f i ca t i on

ash and cemen t .

• I t can be deduced t ha t a 2 .5% gypsum add i t i on i s a good

ave rage t o use i n f u r t he r t es t i ng when hea t o f hyd ra t i on

and compress i ve s t r eng th i s cons ide red .

The e f f ec t o f r ep l acemen t l eve l on t he p rope r t i es o f

i n t e rb l ended and i n t e rg round gas i f i ca t i on ash and cemen t

shows t ha t :


and Ros in -Ramml e r d i s t r i bu t i on pa rame te rs con f i rm tha t

r ep l acemen t l eve l s o f gas i f i ca t i on ash shou ld r ange

be tween 10% and 35%.

• The cemen t manu fac tu red i n t he l ab pe r f o rmed s im i l a r i n

s t r eng th deve lopmen t t o t he comme rc i a l l y ava i l ab l e CEM

I 42 .5R bu t l owe r hea t o f hyd ra t i on t empe ra tu res i s

obse rved f o r t he cemen t ma nu fac tu red i n t he l ab .

• I n t e rg r i nd i ng o f gas i f i ca t i on ash and cemen t i n t he ba l l

m i l l i s i n my op in i on be t t e r t han i n t e rb l end ing gas i f i ca t i on

ash and cemen t i n t he m i xe r .

The e f f ec t o f i n t e rb l ended and i n t e rg round gas i f i ca t i on ash and

cemen t on t he sho r t and l ong t e rm p rope r t i es o f conc re te had

t he f o l l ow ing resu l t s :


conc re te wou ld have eco log i ca l and econom ica l bene f i t s

i n t he cemen t i ndus t r y .


8-3

• The s l ump t es t r esu l t s i nd i ca te t ha t t he use o f

gas i f i ca t i on ash as cemen t ex tende r w i l l r esu l t s i n a

r educ t i on i n t he wo rkab i l i t y o f conc re te .


have a n ega t i ve impac t on t he s t r eng th deve lopmen t o f

conc re te . The re was no reduc t i on i n t he t ens i l e s t r eng th

o f conc re te .


have a de t r imen ta l e f f ec t on t he s t i f f ness o f conc re te .

• The resu l t s f o r sh r i nkage i nd i ca te t he gas i f i ca t i on ash d i d

no t sh r i nk s i gn i f i can t l y mo re t han f l y ash . C reep resu l t s

i nd i ca te tha t gas i f i ca t i on ash d i d no t c reep s i gn i f i can t l y

mo re t han f l y ash . The spec i f i c c reep resu l t s i nd i ca te tha t

gas i f i ca t i on ash has a spec i f i c c reep s im i l a r t o f l y ash .

The e f f ec t o f t he gas i f i ca t i on ash on t he du rab i l i t y o f conc re te

showed :


r esu l t s i n an i n c rease i n po ros i t y . I t i s t he re fo re

an t i c i pa ted t ha t t he conc re te con ta i n i ng gas i f i ca t i on ash

w i l l be no l ess du rab le t han conc re te cu r ren t l y

manu fac tu red .

• The use o f gas i f i ca t i on ash i n conc re te ach ieves a l ow

pe rmeab i l i t y and a du rab le conc re te can be expec ted .

• Gas i f i ca t i on ash can be used as a cemen t ex tended i n

conc re te .

8 .2 REC OMMENDATI O NS

• The env i r onmen ta l impac t o f dec reas ing CO 2 i n t he

manu fac tu r i ng o f cemen t can bene f i t f r om us ing

gas i f i ca t i on ash as a cemen t ex tende r .


8-4


conc re te i s h i gh l y r ecommended due t o cha rac te r i s t i c s

l i ke i nc reased s t r eng th deve lo pmen t and reduced

pe rmeab i l i t y .

• The e f f ec t o f va r i ab i l i t y i n chemica l p rope r t i es o f

gas i f i ca t i on ash shou ld be fu r t he r i nves t i ga ted .

• The e f f ec t o f adm ix tu res on gas i f i ca t i on ash cou ld

i n f l uence t he wa te r demand o f conc re te and cause

conc re te t o be expens i ve .

• Long t e rm t es t i ng shou ld be done on gas i f i ca t i on ash t o

de te rm ine t he e f f ec t on conc re te du rab i l i t y .

• Tes t i ng shou ld be repea ted on gas i f i ca t i on ash t o

de te rm ine a t r end f o r t he behav io r o f gas i f i ca t i on ash

when used as a cemen t ex t ende r i n conc re te .

• The g r i nd i ng t imes and resu l t s a re no t necessa r i l y t he

on l y answe r s i nce t he l abo ra to r y equ ipmen t has a

i n f l uence on t h i s .


9-1

9. REFERENCES

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Conc re te . AC I Jou rna l , Feb rua ry 1995 ,

Add i s , B . J . and Owens , G . 2001 . Fu l t on ’ s Conc re te

Techno logy . E igh t Ed i t i on . Ceme n t and Conc re te

I ns t i t u t e . M id rand , Sou th A f r i ca .

A l exande r , M .G Mackechn ie , J .R and Ba l l im , Y . Gu id e

t o t he use o f du rab i l i t y i ndexes f o r ach iev i ng du rab i l i t y

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Un i ve rs i t y o f W i twa te r s rand . Resea rch Monog ra ph

No .2 . Cape Town . 1999 .

Amer i can Coa l Ash Assoc ia t i on . 1997 . Coa l combus t i on

P roduc t -P roduc t i on and Use . A lexand r i a . V i r g i n i a .

ASTM C 469 -02 . S tanda rd t es t me thod f o r s t a t i c

modu lus o f e l as t i c i t y and po i sson ’ s r a t i o o f conc re te i n

compress i on . Wes t Conshohocken . Amer i can Soc ie t y

f o r Tes t i ng and Ma te r i a l s . 2002 .

ASTM C 512 -02 . S tanda rd t es t me thod f o r C reep o f

Conc re te i n Comp ress ion . Amer i can Soc ie t y f o r Tes t i ng

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ASTM C 1861 -97 . S tanda rd Gu ide f o r Use o f Coa l

Combus t i on By -P roduc t s i n S t ruc tu ra l F i l l s . Amer i can

Soc ie t y f o r Tes t i ng Ma te r i a l s . Wes t Conshohocken .

Pennsy l van ia . 2002 .

Babcock and W i l cox . 1978 . S team. I t s Gene ra t i on and

Use . New Yo rk , NY .


9-2

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d r y i ng sh r i nkage , t es t me th ods , f ac to r s i n f l uenc ing and

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W i twa te r s rand . Ju l y 2003 . (MSc P ro j ec t Repo r t ) .

Ba l l im , Y . 1999 . Loca l i s i ng i n t e rna t i ona l conc re te

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conc re te t echno logy f o r deve lop ing coun t r i es . New

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I nnova t i ons i n Po r t l and Cemen t Manu fac tu r i ng .

Po r t l and Cemen t Assoc ia t i on . I l l i no i s .

Bouzoubaâ , N . Zhang , M .H . B i l odeau , A . and Ma lho t ra ,

V .M . 19 97 . The e f f ec t o f g r i nd i ng on t he phys i ca l

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B r i t i sh Conc re te Soc ie t y . 2000 . B r i t i sh Conc re te

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B rown , J .H . 1982 . The s t r eng th and wo rkab i l i t y o f

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I n t e rna t i ona l Sympos ium on t he Use o f PFA i n

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Bye , G . C . Po r t l and cemen t . 1999 . Compos i t i on ,

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9-3

Ca re t t e , G .G and Ma lho t ra , V .M . 1986 . Cha rac te r i za t i on

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CENMET Repo r t 86 -6E . O t t awa . ON.

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d r y i ng sh r i nkage and su lpha te r es i s t ance o f b l ended

cemen t mo r ta r . Cemen t and Conc re te Resea rch .

Vo lume 34 . pp 1087 – 1092 .

Dav i s , R .E Ca r l son , R .W Ke l l y , J .W and Dav i s , H .E .

1937 . P rope r t i es o f cemen ts and conc re tes con ta i n i ng

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Vo lume 33 , pp 577 -612 .

D iamond , S . and Lopez -F lo res , F . 1981 . On t he

d i s t r i bu t i on be tween phys i ca l and chem ica l

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ashes . P roceed ings , Symp os ium on E f f ec t s o f F l y Ash

I nco rpo ra ted i n Cemen t a nd Conc re te . Ed i t ed by S .

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E rdogdu , K . Tokyay M . and Tü rke r , P . 1999 .Compar i son

o f i n t e rg r i nd i ng and sepa ra te g r i nd i ng f o r t he

p roduc t i on o f na tu ra l pozzo lan and GBFS- i nc o rpo ra ted

b l ended cemen ts . Cemen t and conc re te r esea rch ,

Vo lume 29 , pp 743 -746 .

Esca lan te -Ga rc i a , and Sha rp , J .H . 2004 . The chem ica l

compos i t i on and m ic ros t r uc tu re o f hyd ra t i on p roduc t s i n

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9-4

F r i g i one , G . 1983 . Gypsum i n Ce men t . I n : Ghosh SN

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pa r t i c l e s i ze d i s t r i bu t i on and compress i ve s t r eng th i n

P ro t l and Cemen t . Cemen t and Conc re te Resea rch .

Vo lume 6 . pp 113 -128 .

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Vo lume 87 . pp 351 -357 .

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A f r i can f l y ashes on t he eng inee r i ng p rope r t i es o f

conc re te . PhD thes i s . Johannesbu rg . Un i ve r i s t y o f t h e

W i twa te r s rand .

Hec t , N .L . and Du va l l , D .S . 1975 . Cha rac te r i sa t i on and

U t i l i za t i on o f Mun i c i pa l and U t i l i t y S l udges and Ashes :

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Ho l c im . 2005 . Ma te r i a l s Handbook . Ho l c im Sou th

A f r i ca .

I l l s t on , J .M . and Domone , P .L . J . 2001 . Cons t ruc t i on

Ma te r i a l s . The i r na tu re and behav iou r . Th i rd Ed i t i on .

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Josh i , R .C . 1982 . E f f ec t o f coa rse f rac t i on (+ #325 ) o f

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I n t e rna t i ona l Symp os ium on F l y Ash U t i l i za t i on . Reno ,

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9-5

K rüge r , J .E . 1999 . Gu ide 2 : O r i g i n , H i s t o r y and

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Ash Cemen ts . Gu ides on the use o f Sou th A f r i can f l y

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Assoc ia t i on , Sou th A f r i ca .

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I n t e rna t i ona l . Vo lume 4 , Nu mber 7 . pp 81 -92 .

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sys tem o n t he f l u i d i t y o f cemen t pas tes . Cemen t and

conc re te r esea rch , Vo lume 33 , pp 763 -768 .

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hyd ra t i on and p ro pe r t i es o f Po r t l and cemen t pas tes .

PCA Bu l l e t i n . Number 12 .

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o f pa r t i c l e s i ze d i s t r i bu t i on on t he s t r eng th o f Po r t l and

cemen t . Zemen t -Ka l k -G ips . Vo lume 26 . pp 349 -355 .

Massazza , F . 1998 . Chem ica l ana l ys i s o f Po r t l and

cemen ts . Chap te r 4 : Lea ’ s Chem is t r y o f Cemen t an d

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9-6

Me tha , P .K . 1989 . Pozzo lan i c and cemen t i t i ous by -

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CANMET/ ACI I n t e rna t i ona l Con fe rence on the use o f

F l y Ash , S i l i ca Fume , S lag and O the r M i ne ra l By -

P roduc t s i n Conc re te , T rondhe im , No rway . J une 18 -23 .

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f l y ash con ten t on wa te r demand , t ime o f se t and

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Jou rna l . Vo lume 87 . pp 619 -626 .

Nev i l l e , A .M . 19 95 . P rope r t i es o f Conc re te . Fou r t h

Ed i t i on . Longman Group L td . London .

Newman , J . 2003 . Advanced conc re te techno logy .

E l sev i e r L td .

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d i s t r i bu t i on o f g round g ranu la ted b l as t f u rnac e s l ag on

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Un i ve r s i t y o f Leeds .

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Conc re te : The Jou rna l o f t he Conc re te Soc ie t y . Vo lume

13 . pp 21 -26 .

Pandey , S .P . 1 983 . The Pa r t i c l e S i ze D i s t r i bu t i on

Ana l ys i s : Sc i ence and App l i ca t i ons i n Ceme n t

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Pe rgamo n P ress .New Yo rk . pp 735 -775 .


9-7

Ros in , P . and Ra mmle r , E . 1933 . The l aws gove rn i n g

t he f i neness o f powde red coa l . Jou rna l o f t he I ns t i t u te

o f Fue l . Vo lume 7 . pp 29 -33 .

Sandbe rg , P . 2005 . The us e o f I so the rma l ca l o r ime t r y

t o op t im i se cemen t su l pha te Pa r t 1 – Ceme n t w i t hou t

adm ix tu res . I n t e rna l Documen t . G race Cons t ruc t i on

P roduc t s .

SANS 14 91 /SABS 1491 :1989 . Po r t l and cemen t ex tende rs ,

Pa r t 1 : G round g ranu la ted b l as t f u rnace s l ag , Pa r t 2 : S i l i ca

f ume , Pa r t 3 : F l y ash . Sou th A f r i can Bu reau o f S tanda rds .

P re to r i a .

SANS 50 196 -1 /SABS 196 -1 :1994 . Me thods o f t es t i ng

cemen t , Pa r t 1 : De te rm ina t i on o f s t r eng th . Sou th

A f r i can Bu reau o f S tanda rds . P re to r i a .


cemen t , Pa r t 1 : Su lphu r t r i o x i de con ten t and l oss on

i gn i t i on . Sou th A f r i can Bu reau o f S tanda rds . P re to r i a .


cemen t , Pa r t 1 : Soundness . Sou th A f r i can Bu reau o f

S tanda rds . P re to r i a .

SANS 5 0197 -1 /SABS 197 -1 :2000 . Cemen t Pa r t 1 :

Compos i t i on , spec i f i ca t i on and con fo rm i t y c r i t e r i a f o r

common cemen ts . Sou th A f r i can Bu reau o f S tanda rds .

P re to r i a .

SANS 5 862 /SABS SM 8 62 :1994 . Conc re te t es t s –

Cons i s t ence o f f r esh l y m i xed conc re te , Pa r t 1 : S l ump

t es t s , Pa r t 2 : F l ow t es t , Pa r t 3 : Vebe t es t , Pa r t 4 :

Compac t i ng f ac to r and compac t i on i ndex . So u th A f r i can

Bu reau o f S tanda rds . P re to r i a .


9-8

SANS 58 63 /SABS Me thod 863 -1994 . Conc re te t es t s –

Compres s i ve s t reng th o f ha rdened conc re te . 1 s t

Rev i s i on . Sou th A f r i can Bu reau o f S tanda rds . P re to r i a .

SANS 61 51 /SABS Me thod 863 -1994 . F reewa te r con ten t

o f Po r t l and cemen t ex tende rs . 1 s t Rev i s i on . Sou th


SANS 61 56 /SABS Me thod 863 -1994 . Wa te r r equ i r emen t

o f Po r t l and cemen t ex tende rs . 1 s t Rev i s i on . Sou th


SANS 6 157 /SABS Me tho d 863 -1994 . F i neness o f

cemen t and Po r t l and ceme n t ex ten de rs . 1 s t Rev i s i on .

Sou th A f r i can Bu reau o f S tanda rds . P re to r i a .

SANS 62 53 /SABS Me thod 863 -1994 . Conc re te t es t s –

Compres s i ve s t reng th o f ha rdened conc re te . 1 s t

Rev i s i on . Sou th A f r i can Bu reau o f S tanda rds . P re to r i a .

Schwar t z , K .P . 2 003 . The ou t l ook f o r CCPs . E lec t r i c

Pe rspec t i ves . Ju l y /Augus t 2003 .

S te f f an , P . and Dean , G . 19 91 . FGD Gypsum

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Managemen t Con fe rence . p . 1 .

Tang , F .J . and Ga r tne r , E .M . 1988 . I n f l uences o f

Su lpha te Sou rce on Po r t l and Cemen t Hyd ra t i on .

Advances i n Cemen t Resea rch . Vo lume 1 . Number 2 .

Ap r i l 1988 .

Tay lo r , H .F .W. 1982 . Cemen t Chem is t r y , 2 n d ed .

Te l f o rd . Rep r i n t ed 1982 .


9-9

Uch i kawa , H . 1986 . E f f ec t o f b l end ing componen ts on

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I n t e rna t i ona l Cong ress on t he Chem is t r y o f Cemen t s .

R io de Jane i r o , B raz i l . Sep t , 22 -27 . Spec ia l s Repo r t

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Sou rces us i ng SASOL Lu r g i F i xed Bed D r y Bo t t o m

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con fe rence . Mon tebe l l o , Canada . SP-79 . pp 307 -319 .



APPENDIX A

CUMULATIVE PARTICLE SIZE DISTRIBUTION OF GASIF ICATION

ASH, CEMENT AND GASIF ICATION ASH AND CEMENT

INTERGROUND AND INTERBLENDED


A-1

Cumulative Particle size distribution of Gasification ash

0

20

40

60

80

100

120

0.01 0.1 1 10 100 1000

Particle size (µm)

Cum

ulat

ive

part

icle

siz

e di

strib

utio

n % GA,30min

GA,1hr

GA,1.5hr

GA,2hrGA,2.5hr

GA,4hr

Cumulative Particle size distribution of Cement

0102030405060708090

100

0.01 0.1 1 10 100 1000

Particle size (µm)

Cum

ulat

ive

Part

icle

siz

e di

strib

utio

n %

CEM,30min

CEM,1hr

CEM,1.5hrCEM,2hr

CEM,2.5hr

CEM,4hr


A-2

Cumulative particle size distribution of gasification ash and cement interground

0102030405060708090

100

0.1 1 10 100 1000

Particle size (μm)

Cum

ulat

ive

part

icle

siz

e di

strib

utio

n %

IG, 30min

IG,1hr

IG,1.5hr

IG,2hr

IG,2.5hr

IG,4hr

Cumulative particle size distribution of gasification ash and cement interblended

0102030405060708090

100

0.1 1 10 100 1000

Particle size (μm)

Cum

ulat

ive

part

icle

siz

e di

strib

utio

n % IB 30 min

IB 1hrIB 1.5 hr

IB 2 hrIB 2.5hr

IB 4 hr


APPENDIX B

CUMULATIVE % OVERSIZE PARTICLE SIZE

DISTRIBUTIONS FOR GASIF ICATION ASH, CEMENT AND

GASIF ICATION ASH AND CEMENT INTERGROUND AND

INTERBLENDED


B-1

Cumulative % oversize particle size distribution

y = 0.9429e-0.0122x

R2 = 0.9991

0%

20%

40%

60%

80%

100%

0 50 100 150 200 250

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,30min

Expon. (GA,30min)


y = 0.9329e-0.0284x

R2 = 0.9989

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100 120

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,1hr

Expon. (GA,1hr)


B-2


y = 0.9331e-0.0382x

R2 = 0.9986

0%

20%

40%

60%

80%

100%

0 20 40 60 80

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,1.5hr

Expon. (GA,1.5hr)


y = 0.9452e-0.0507x

R2 = 0.9978

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,2hr

Expon. (GA,2hr)


B-3


y = 0.9254e-0.0554x

R2 = 0.9981

0%

20%

40%

60%

80%

100%

0 10 20 30 40 50 60

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

GA,2.5hrExpon. (GA,2.5hr)


y = 0.8942e-0.0781x

R2 = 0.9952

0%

20%

40%

60%

80%

100%

0 10 20 30 40

Particle size (μm)

Cum

ulat

ive

% o

vers

ize



B-4


y = 0.9675e-0.024x

R2 = 0.9936

0%

20%

40%

60%

80%

100%

0 50 100 150

Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,30min

Expon. (CEM,30min)


y = 0.7121e-0.0144x

R2 = 0.8842

0%

20%

40%

60%

80%

100%

0 50 100 150 200 250 300

Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,1hrExpon. (CEM,1hr)


B-5


y = 0.9411e-0.0249x

R2 = 0.9858

0%

20%

40%

60%

80%

100%

0 50 100 150Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,1.5hr

Expon. (CEM,1.5hr)


y = 0.8794e-0.0237x

R2 = 0.9681

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,2hr

Expon. (CEM,2hr)


B-6


y = 0.9077e-0.0247x

R2 = 0.9791

0%

20%

40%

60%

80%

100%

0 50 100 150

Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,2.5hr

Expon. (CEM,2.5hr)


y = 0.8179e-0.0179x

R2 = 0.9454

0%

20%

40%

60%

80%

100%

0 50 100 150 200 250

Particle size (µm)

Cum

ulat

ive

% o

vers

ize

CEM,4hr

Expon. (CEM,4hr)


B-7


y = 0.955e-0.0198x

R2 = 0.9996

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IG, 30min

Expon. (IG, 30min)


y = 0.975e-0.0354x

R2 = 0.9997

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Particle size (μm)

Cum

alat

ive

% o

vers

ize

IG,1hr

Expon. (IG,1hr)


B-8


y = 0.9929e-0.0514x

R2 = 0.998

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Particle size (μm)

Cum

alat

ive

% o

vers

ize

IG,1.5hrExpon. (IG,1.5hr)


y = 0.9835e-0.05x

R2 = 0.9983

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Particle size (μm)

Cum

alat

ive

% o

vers

ize

IG,2hr

Expon. (IG,2hr)


B-9


y = 0.9693e-0.0532x

R2 = 0.9986

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Particle size (μm)

Cum

alat

ive

% o

vers

ize

IG,2.5hr

Expon. (IG,2.5hr)


y = 0.9822e-0.0608x

R2 = 0.9963

0%

20%

40%

60%

80%

100%

0 20 40 60 80 100

Particle size (μm)

Cum

alat

ive

% o

vers

ize

IG,4hr

Expon. (IG,4hr)


B-10


y = 0.9031e-0.0165x

R2 = 0.9874

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 30 min

Expon. (IB 30 min)


y = 0.8898e-0.023x

R2 = 0.9792

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 1hr

Expon. (IB 1hr)


B-11


y = 0.9607e-0.03x

R2 = 0.9973

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 1.5 hrExpon. (IB 1.5 hr)


y = 0.945e-0.0334x

R2 = 0.9946

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 2 hr

Expon. (IB 2 hr)


B-12


y = 0.9142e-0.0321x

R2 = 0.9897

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 2.5hr

Expon. (IB 2.5hr)


y = 0.8079e-0.0256x

R2 = 0.9545

0%

20%

40%

60%

80%

100%

0 50 100 150 200

Particle size (μm)

Cum

ulat

ive

% o

vers

ize

IB 4 hr

Expon. (IB 4 hr)


APPENDIX C

ROSIN-RAMMLER DISTRIBUTION GRAPHS


C-1

Rosin-Rammler distribution graph

y = 0.9653x - 4.1996R2 = 1

0

0.5

1

1.5

0 2 4 6

ln (Particle size(µm))

ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,30min

Linear (GA,30min)


y = 0.958x - 3.347R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,1hr

Linear (GA,1hr)


C-2


y = 0.9589x - 3.0666R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,1.5hr

Linear (GA,1.5hr)


y = 0.9665x - 2.8296R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5ln (Particle size(µm))

ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,2hr

Linear (GA,2hr)


C-3


y = 0.9543x - 2.6897R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,2.5hrLinear (GA,2.5hr)


y = 0.934x - 2.2793R2 = 0.9999

0

0.5

1

1.5

0 1 2 3 4


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

GA,4hr

Linear (GA,4hr)


C-4


y = 0.9816x - 3.6309R2 = 1

0

0.5

1

1.5

0 2 4 6 8


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,30min

Linear (CEM,30min)


y = 0.816x - 3.1629R2 = 0.9984

0

0.5

1

1.5

0 1 2 3 4 5 6


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,1hr

Linear (CEM,1hr)


C-5


y = 0.9662x - 3.5129R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5 6


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,1.5hrLinear (CEM,1.5hr)


y = 0.9307x - 3.3684R2 = 0.9999

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,2hr

Linear (CEM,2hr)


C-6


y = 0.9469x - 3.4172R2 = 0.9999

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,2.5hr

Linear (CEM,2.5hr)


y = 0.8908x - 3.4053R2 = 0.9996

0

0.5

1

1.5

0 1 2 3 4 5 6


ln ln

(1/C

umul

ativ

e %

ov

ersi

ze)

CEM,4hrLinear (CEM,4hr)


C-7


y = 0.9743x - 3.7795R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG, 30min

Linear (IG, 30min)


y = 0.9848x - 3.2664R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG,1hr

Linear (IG,1hr)


C-8


y = 0.9959x - 2.9494R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG,1.5hr

Linear (IG,1.5hr)


y = 0.9902x - 2.951R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG,2hr

Linear (IG,2hr)


C-9


y = 0.9813x - 2.8498R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG,2.5hr

Linear (IG,2.5hr)


y = 0.9896x - 2.7544R2 = 1

0

0.5

1

1.5

0 1 2 3 4 5


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IG,4hr

Linear (IG,4hr)


C-10

Rosin-Rammler Distribution graph

y = 0.9424x - 3.7753R2 = 0.9999

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 30 min

Linear (IB 30 min)


y = 0.9348x - 3.4207R2 = 0.9999

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 1hrLinear (IB 1hr)


C-11


y = 0.9777x - 3.3921R2 = 1

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 1.5 hr

Linear (IB 1.5 hr)


y = 0.9686x - 3.2527R2 = 1

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 2 hrLinear (IB 2 hr)


C-12


y = 0.9499x - 2.0479R2 = 0.9999

0

0.5

1

1.5

0 2 4


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 2.5hr

Linear (IB 2.5hr)


y = 0.8839x - 3.0507R2 = 0.9995

0

0.5

1

1.5

0 2 4 6


ln ln

(1/C

umul

ativ

e pa

rtic

le

size

dis

trib

utio

n)

IB 4 hr

Linear (IB 4 hr)


APPENDIX D

BLAINE SURFACE AREA CALCULATIONS


D-1

Cement 7.83gr RD = 3.2 Sample time (sec) cm2/g m2/g

30 min 125.1 3147 3151 hour 138.9 3316 3321.5 hours 175.3 3726 3732 hours 217.1 4146 4152.5 hours 228.5 4254 4254 hours 227.6 4245 425 Gasification ash 6.65gr RD =2.715

Sample time (sec) cm2/g m2/g 30 min 68 2320 2321 hour 173.8 3710 3711.5 hours 253.8 4483 4482 hours 355 5302 5302.5 hours 437.7 5887 5894 hours 668.5 7275 728 Intergrinding 7.28gr RD = 2.976

Sample time (sec) cm2/g m2/g 30 min 131.4 3226 3231 hour 186.2 3840 3841.5 hours 255.4 4497 4502 hours 333 5135 5132.5 hours 348 5249 5254 hours 558.1 6648 665


APPENDIX E

MORTAR PRIS MS STREN G TH SU MMAR Y FOR THE E FFECT OF GRINDING T IME ON THE PROPERTIES OF INTERBL ENDE D

GASIF I C AT ION A SH AN D CEMENT


E-1

Summary Table

Interblending Gasification ash and Cement

Compression (MPa)

30 min

1 hour

1.5 hours 2 hours 2.5

hours 4

hours Cement (2 hrs)

2 days 10.1 11.9 11.2 20.1 18.4 17.6 17.6

7 days 19.5 24.1 23.5 34.3 29.7 31.3 31.5

28 days 30.8 32.1 33.1 45.1 45.4 43 44.9

Tension (MPa) 30 min

1 hour

1.5 hours 2 hours 2.5

hours 4

hours Cement

(2 hours)

2 days 3 3.5 3.3 4.9 4.5 4.8 3.8

7 days 5.2 5.8 5.5 7.3 6.7 7.4 7.3

28 days 7.3 7.7 8.2 8.9 8.8 8.9 8.2


APPENDIX F

MORTAR PRIS MS STREN G TH SU MMAR Y FOR THE E FFECT OF GRIN DIN G T IME ON TH E PROPERTIES OF INTERGROUND



F-1

Summary Table

Intergrinding Gasification Ash and Cement

Compression (MPa)

30 min 1 hour 1.5

hours 2

hours 2.5

hours 4 hours Cement (2 hours)

2 days 11.8 13.3 17 21.5 19.5 19.2 17.6

7 days 19.4 24.6 29.3 32.4 31.6 31.7 31.5

28 days 27.3 32.9 40.1 43.2 41.6 43.6 44.9

Tension (MPa) 30 min 1 hour 1.5

hours 2

hours 2.5

hours 4 hours Cement (2 hours)

2 days 3 3.4 4.2 4.8 4.5 5.1 3.8

7 days 4.6 6 6.5 7.3 6.7 7.2 7.3

28 days 7 8 8.8 8.6 9 8.8 8.2


APPENDIX G

MORTAR PRIS MS STREN G TH SU MMAR Y FOR THE EFFECT OF GYPSUM CONT ENT ON THE PROPE RTIES OF INTERGROUND



G-1

Summary Table

Gypsum Content

Compression (MPa) 0% 0.50% 1% 1.50% 2% 2.50% 3%

2 days 10.7 11.1 11.7 11.6 12 12.1 15.2

7 days 25.1 24.5 24.9 25.7 27.6 25.7 28.6

28 days 33.7 36.1 36.9 32.9 36.2 37.1 38.9

Tension (MPa) 0% 0.50% 1% 1.50% 2% 2.50% 3%

2 days 3.2 3.3 3.2 3.4 3.3 3.3 4.5

7 days 6 6 5.5 6.2 5.9 5.7 6.2

28 days 7.0 7.8 7.7 7.5 8.0 7.7 7.6


APPENDIX H

MORTAR PRIS MS STREN G TH SU MA RY FOR THE EFF ECT OF REPLACEME NT L EVEL ON THE PROPE RTIE S OF

INTER GR OUN D GASIF ICA T ION A S H AND C EME NT


H-1

Summary Table

Replacement Level

Compression (MPa) 0% 10% 20% 35% 55%

2 Days 32.1 34.4 26.1 18.3 6.5

7 Days 47.0 50.3 45.4 32.6 16.9

28 Days 56.9 57.9 53.2 43.3 28.9

Tension (MPa) 0% 10% 20% 35% 55%

2 Days 6.8 7.2 4.7 4.3 1.5

7 Days 8.8 9.2 9.1 7.2 4.4

28 Days 9.7 9.8 9.6 9.5 7.5


APPENDIX I

MORTAR PRIS MS STREN G TH SU MMAR Y FOR THE C OMPARI SON BETWEE N MA NUF ACTU RE D AND C OMME RC IAL CE MENT


I-1

Summary Table

Compression (MPa) IB CEM+GYPSUM IG CEM +GYPSUM CEM I 42.5 R

2 Days 18.8 29.8 22.3

7 Days 34.5 49.4 36.2

28 Days 42.0 61.5 53.0

Tension (MPa) IB CEM+GYPSUM IG CEM +GYPSUM CEM I 42.5

2 Days 4.2 5.9 5.0

7 Days 6.4 8.3 7.8

28 Days 8.3 10.0 9.9


APPENDIX J

CUBE ST REN GTH SUMMA R Y


J-1

Cube St rength Summary Table

Summary 24 hour 7 days 28 days

IG (MPa) 6.33 22.64 31.5

IB FA (MPa) 6.31 15.93 26.7

IB GA (MPa) 7.59 19.29 28.0


APPENDIX K

SPECIF I C CRE EP SUMMARY


K-1

Speci f ic Creep Summary Table

T ime (days) IG GA (microst ra in )

IB FA (microst ra in )

IB GA (microst ra in )

0 0 .00 0 .00 0 .00

1 10 .48 4 .15 11 .13

2 14 .30 20 .25 21 .80

3 24 .30 29 .59 30 .61

7 38 .12 44 .65 42 .67

8 43 .84 51 .92 48 .70

10 49 .08 57 .63 53 .80

13 58 .61 68 .02 64 .47

15 67 .19 77 .88 72 .82

17 71 .48 83 .59 75 .60

41 97 .69 97 .09 89 .98

48 116 .27 113 .70 115 .49

53 120 .08 120 .97 116 .42

64 129 .61 124 .09 119 .20

120 148 .20 137 .07 136 .83

127 155 .82 142 .78 141 .00

132 159 .16 145 .89 143 .78

146 163 .92 153 .68 150 .28

167 171 .07 160 .95 158 .16

269 188 .23 175 .49 173 .00

309 201 .09 169 .78 184 .60


APPENDIX L

POROSIT Y SUMMARY


L-1

Summary Table

M ix Poros i ty

IG 15 .1%

IB FA 15 .9%

IB GA 15 .4%


APPENDIX M

PERMEABIL ITY CALCUL ATIONS


M-1

Summary Table

M ix IG IB FA IB GA Pressure bar 2 2 2 2 2 2 2 2 2

Diamete r (m) 0 .06935 0 .0694 0 .06935 0 .0693 0 .0694 0 .06935 0 .0694 0 .0694

5 0 .0693

5

Area (m 2 ) 0 .003777312

0 .00378276

0 .0037773

0 .003771867

0 .003783

0 .003777

0 .00378276

0 .003788

0 .003777

T ime average ( s ) 4 .85 10 .93 8 .29 12 .83 10 .81 11 .15 11 .53 8 .29 9 .79

Read ing ( m 3 /s ) 1 .88262E-05

8 .3735E-06 1 .1E -05 7 .10137E-

06 8 .42E-

06 7 .78E-

06 7 .85095E

-06 1 .08E-

05 9 .38E-

06 Th ickness o f

d isc (m) 0 .02 0 .02 0 .02 0 .02 0 .02 0 .02 0 .02 0 .02 0 .02

e 2 .02E-16 2 .02E-16 2 .02E-16 2 .02E-16 2 .02E-

16 2 .02E-

16 2 .02E-16 2 .02E-16

2 .02E-16

Permeab i l i t y (m /s ) 1 .621E-20 7 .213E-

21 9 .461E-

21 6 .125E-21 7 .21E-21

6 .37E-21

6 .688E-21

9 .07E-21

8 .14E-21

Permeab i l t y average (m /s ) 1 .096E-20 6 .569E-21 7 . 967E-21

OPI 19 .96 20 .18 20 .098


Documents

THE USE OF GASIFICATION ASH IN CEMENT AND CONCRETE