University of Nigeria Research Publications

OKIKA, Philip Chukwuemeka

Aut

hor

PG/MENGR /82/1563

Title

Natural Fibre – Reinforced Cement Composites

Facu

lty

Engineering

Dep

artm

ent

Civil Engineering

Dat

e

May, 1987

Sign

atur

e

NATURAL FZw-%REINE'ORaD

CEMENT CGNr'CSTThL

PHILIP C-IUKWEMEKA KANAYO O K I K k

( PG/M, ENGX, O2/1563

Submitted to t h e De?astmcnt of Civil Engineering

I n Partial Ftdfilinent of t he Requirement f o r

the A w a r d of the Degree of

%st= of Engineering

of the

University of Nigeria, Nsukka

D E D I C A T I O N

TO

I* WIFE C X I N k E

A C K N O h ? L E P G E M E M T - ---- -------

The author is indebted t o Prof , R, P?, Madu, for

h i s valuable advice, c lose supervision and general

guidance,

fq~preciat ion i s expressed t o Mr, S, A, Dogbe of

the Department of Materials Technology, Federal Polytechnic

Idah, Benue State ; M r , 3, Ue Asogwa of the Concrete

Testing Labora tary ) Civi l Engineering Department,

University of Nigeria, Nsukka and t h e Turners Asbestos

Company, Emene - Enuq f o r t h e i r immense contribution

towards the accomplishment of the project ,

Okika, P. C,K,

This project has h e n ap2roved by the

Department of Civil Engineering,

Universi ty of Nigeria, Nsukka,

Prof. 12, M, lkdu Supervisor Head of Dept,

External E2mninex

QWPTEH 1: General b a

l a 1 Abstract f3 ,+

1.2 Notations and def in i t ions

10201 Notations o n

1.2.2 Definitions e O

CHAPTER 2: Li terature Review

2-1 Introduction a O

2.2 Factors a f fec t ing properties of natural f i b r e - reinforced cement composites . , o

2.3 Nechanical Properties of natural fibre-reinforcsd cement composites based on Iaboratory expert-tal work 0 0

2.3.1 Tensile s t rength a 0 0

2.3.2 Flexural s t rength o a

2.3.3 Coqressive s t rength rn C )

2.3,4 Fracture toughness O a

2.3.5 Impact s t rength O I

2e3.6 Other properties of natural f i b r e reinforced cement composites

2.4 Natural fibre-reinforced cement products . rn

2 *4.1 Coconut fibre-reinforced corrugated sheets and slabs e D

2.4.2 Si sa l fibre reinforced corrugatdd s labs .

2-5 Other observations on tests and result 44

v i

m R 3: Fj bre $repaz?ation and tests o~

3.1 F i l re extx'aceion nrdl tests m e

3.2 Stjvcture and physical properkies of some natural f ibres .

3.2.1 Ph: *sf cal appearance

3,2.2 M&:ro-strc~cture 0 . CHAPTER 4: C x n p o s i t e a

4.1 Pr2paraUon of composite epocimns

Ma terials

Mi xes

q p e - of Spscfnens

PI ocedure for f abric~tlon

TG s tlng

Y e s t results and discussions

E qerimental results m d 0: ~servations

S xength properties

Ddormational properties

C Lseussion of results

5.2.1 E E f e c t s of fibre characteris tic8 ~ n d mtrix qualities .

5.2.2 C,ther influencing factors . CXAPTER 6: S u n a a r y and Comrlusicm

w a r s affecting properties d ndkural fibtsdeinforced concrete

EFfects of incorporation of rsoconut fibre on properties of concrete

U l t i m a t e strength, nloduli of elas t ic i ty and poissoncs ratio of sugarcane bagasse f i b ~ e i n f o r c e d cement composites

Effects of length and concentration of jute fib^? on strength parameters

Propertie:: of cellulose (Pfnw Radiata) cement composites

Properties of f l a x fibre reinforced cement morrtars

Flexural s t rength data of fibre concrete

Mulus of rupture of sisal f ibre reinforced concrete

Mechanical. properties of cellulose-cerme~t

kmuLts of: impact strdgth tebts on p ~ h f n cone:rete, jute, bamboo and coir f5bre concrete

Snpact strengths of various natural f ibre reirforced concretes

1Eherml ccnductivity of coir f i b r e wrmgated slabs

Sound absorpUon coeEficient (values are in % absorbed) for coir f ibre building materials

Typical thermal conductivitfa of building materials

Comparison of physlcal properties of wLr fibre reinforced roofing sheets and asbest3s roofing sheets

16. b a d bearing capacity i n Kgf(~) at the limit of prouortionali ty for s i sa l fbre corwgated s'leets

17 Loadbearing capacity at the limit of proportiona1:tty in kgf per metre width of sheeC, kgf/m (N/m) for sisal fibre corrugated sheets

18 Tensile test results for coconut 5ibres

19 Tensile test results for plantain fibres

20 Tensile test results for rafia fibxes

21 Properties of natural f ibre cement mortars

Figures

E f f e t t of fiEre content on tensile strength 8

Effect of fibre length on tensile strength 9

variakiwr of t a i l e d d bend dt tengthr with majr fraction of cellulose fibr&s 11

Young s Variakion of . 4 modulus in bending and in tension w l t h mads f r a t t i o n 14

Effect of flax f ibre content on flexural stre?gth a t various test conditions 15

Effects of refining flax fibres on nmodulus of rupture

Effects of fibre content on flexural strength at various fceeness values 18

Effect of f i b r e content on flexural strength following various preconditioning treatments 19

Relationship lzetweah casting pressure and modulus of rupture for coconut fibre reinf n r r d c m m ~ n t na.rte 20

ix Page

Relaticnship between ncdulus of rupture of composites and volume f r ac t i cn f o r coconut fibres

Stress-strain behaviour f o r un- reinforced and chopped sisal. fibre reinforced concrete 2 3

Stress-strain khaviour f o r concrete reinforced w i t h continuous sisal fibres 2 3

Effect 3n the stress-strain behaviour for Continuous sisal fibre concrete whrn th: matrix quality is changed 24

Effect on the stress-strain behavbur f o r continuous sisal fibre concrete f o r changinq volume f rac t ion of fibres 25

Compressive strength re la t ion with age 27

Compressive strength f a t i o for varying f i b r e content 2 8

Effect of freeness on fractwe toughness a t various values of fibre content 30

Effect of fibre content on f rac ture Dcwghness following various pre-con- d i t ioning treatment 31

Effect of f lax fibre concentration on fracture toughness a t various test conditicns 32

Coripmis on of modulus of rupture with volume f ' raction fo r corrugated coir fibre slab 37

Comparison of modulus of rupture with fibre length at 3% volume fraction 3 7

Production a t the vi l lage level ,of Sisal fibre reinforced products when chopped fibres are used 42

Production i n small scale industries of fibre reinforced products uslng fibre nets

Production of sisal flbre concrete sheets In mechanize1 industries

Coconut fibr.3 glued t o timber plates f o r tensile test

Mean stress-strain curve f o r coconut fibre

k a n stress-strain m e f o r plantain f i k e

%!an stress-strain curve f o r rafia f i b r e

Micro-photograph's of fibre cross-sections in natural dry state

Tensile t e s t set- for fibre-mortar briquette

Flexural t e s t set~up for f ibre-mortar prism

Compressibn test Set-up f o r fibre- mortar cube

Effect of doir Eibm on the tensile strength of mortar

E f f e c t of plantain fibre on the tensile strength of mortar

Effect of rafia fibre on the tmile strength of nortar

Effect of c o i r fibre on the flexural s t rength of n~artar

Wfect of plantain f i b r e on the flexural strength of mortar

Effect of raf'ia f ibre on the f lexural strength of mortar

Page

4 3

4 3

4 7

49

52

55

57-58

61

62

62

66

67

68

71

7 2

73

xl

Effect of flbre content on eube e m pressive strength of mortar

Effect of fibre content en cube - pressive strength of mortar

Effect of f ibre content on cube compressive strength of mortar

Failure pa t t e rn of tensile specimaas

Failure pattern of flexural specimens

Fkilwe pattiern of compression specimens

Strese-strain behavlour of fibre m m r

References

OIAPTER 1: _II-

G E N E R A L ----

1.1 ABSTi-WCT:

Chopped natural f i b re s from coconut husk, plantain

stern and r a f i a palm leaves were examined, testej and

incorporated i n cement mortar, The resu l t ing cgmposites

were then studied t o ascer ta in the effects of f i b r e

presence on the m o r t a r properties. The relevant properties

of these natural f i b re s and t h e bchaviour of t h z i r cement

mortar composites are presented i n this paper.

In this study, some mechanical properties: t ens i l e ,

f l exura l and comp:essive strengths of mortars reinforced

with these fibres were obtaind and compared with those

of equivalent pla:.n mortar with a view to devehping

natural f i b r e r e i n f o r e d ternent mortar building products

comparable t o asbestos cement products.

The experiments show t h a t workable homogenms mixes

are obtainable wLng w e l l proportioned mixes. Ihe findings

also confirm t h a t the f i b r e mass f rac t ion affects the

mechanical proper'lies of composites. I n tensiorl, f l exure

and compression, w e n though f iber& composites d i d not

give higher o r conclusively higher strengths t h m p la in

mortar, t h e i r deformational properties improved and

reasonable strengzhs w e r e obtainable through careful choice

of f i b r e length and content.

1.2 NOTATION3 ii,ND DEFINITIONS - li2-1 Notations .-

Et =

=

Em =

Ef =

f - - +cu =

f p =

fmin =

ft =

fb =

fC =

P - - L - -

Young's modulus i n tension

Young 1 s modulus i n hencli:~g

Void f r x matrix modulus

Fibre mxlulus

St ress

Cube compressive strength

F i r s t crack stress

Stress rotairled after first cracking

U l t i m a t s tensile strength

W u l u s of rupture

Maxtmum post-crack stress

M%imum applied load ( in N)

Diskano-. between axes of t h e support r o l l e r s

( i n nun)

Width OF beam at the l i n e of fracture (mm)

Depth o f beam at the line of f rac tu re ( i n m)

Fibre l m g t h

Fibre mass f r ac t i on

Composite void fraction

Fibre vdume feaction

Raduis of fibre (for non-cylinderkal f ibres

fi'3re cross section area - % :fibre primeter -1

RH

OD

WET

CSF

Densi t y of .fiSre

Density of carilpasite

Ideal der~s i ty OF zonposi ta

Averase f ibrc-matrlx interfacia 1 ho-4 s tren j.th

Fracture toughness oE composite

Mass of saturated composite i n air

Dry mass of composite

Mass of saturated composite under water

Largest grain s i z e

Defini t ions - --- Controlled atmosphere of 50 + 5% relative - humidity and tamprof 22 + ~ O C for 5 days, - Oven heating at 100 - 1 0 5 ~ ~ for 24 h r s - then

cooling i n a des iccator*

Sodking in water for 48 hrs w i t h excess water

remove3 with cloth prior to tes t ing.

Canadi m S t a n d d Freeness

_Lens* pf flbm- h m ) Aspect r a t i o = 2 x radius of fibre (mm)

C W F E R 2 -- ---------- - -----me---

LI ?ZRATURE L V I C t J --- ---------- ---- --- - -- ---------- - 2.1 INTRODUCTIOI --,

Cement pastt , r r ~ r t a r and concrete a r c capable of high

s-rength i n cornpi-ession, weak i n tension, have low s t r a i n

a t failure and are 5enerally very b r i t t l e , Fibres a r e

required i n thest- cment composites t o ovaxorne some of

these shortcornincs, Already, several types of filxes

have been u s 4 ir> t 5 production of many cementitious

bui lding product:, Ihese include asbestos-cement, ferro-

cement, s teel - f i t r, :oncrete, glass-fibre concrete and

polypropylene E i k r ? concrete (19). The most widely used,

asbestos-cement, ?mxgh of sa t i s fac tory i l exuaa l s t rength

still has low i m p c: strength. b r eove r , the asbestos

f i b r e is a b i g h e ~ l th hazard and t h e pr ice i s hich. The

decline i n world c-,momy too is now compelling developing

countries: particl: w l y the t rop ica l ones, t o inves t iga te

all possible ways c f u t i l i z i n g some of t h e n - t u r d fibres

which most of then h m e i n abundance and which are r e l a t i v e l y

cheaper than asbestof .

Some o f t h e s e na tu ra l f i b r e s under i n v e s t i g a t i o n

f o r over a decade n3w, inc lude those fram sisal (16, 17,

331, coconut husk ( 3 , 7, 8, 12, 13, 15, 31, 34) j u t e

(3, 27, 311, bamboo (9, 311, sugarcane bagasse (?4),

aktlara ( l o ) , f l a x (321, wood (351, c e l l u l o s e (231,

p lan ta in and musambs ( 18, 201,

This growing i n t e r e s t i n na tu ra l f ibre-reinforced

cement composites i s aimed a t f ind ing n full or p a r t i a l

substitute f o r asbestos. The r e s u l t s o f researcb work

done s o f a r show improved bending and t e n s i l e s t r eng ths ,

post-cracking res i s t ance , high energy absorbing

c h a r a c t e r i s t i c s and f a t i g u e s t r eng th (7, 8, 12, 13, 14, 16,

27). bwever , t h e ~ b v i o u s problems associa ted with

t h e use of n a t u r a l f i b r e s such a s g rea t s k i l l remirement

i n f i b r e procurement, d i f f i c u l t y i n mixing and placing

of composites, unpraven d u r a b i l i t y of f i b r e s i n concrete,

etc a r e y e t t o be o-~ercome.

From the work of researchers on natural f ib re -

reinforced cement composites, a lot of f a c t o r s are now

known t o a f f e c t t h e proper t ies of such composites.

Table 1 gives a l is t of some of t h e s e f ac to r s .

However, t he mechanical properties are depenclent

principally on t h e following parameters: cas.t-3ng pressure,

fibre volume fract ion anb aspect ratio, water/cement

r a t i o , properties of t h e fibre and quality OF the cement

paste or mortar (13, 34).

Tab1 e I . Factom- affectina n r o ~ ~ r k i es of natural f i hre

reinforced concrete (26).

Factors Cons ti tuents

Fibre type

Fibre geometry

Fibre form

Fibre surface

Fbtrix properties

Mix design

Mixing method

Placing method

Casting method

Curing method

c ~ o n u t , s i s a l , sugarcane bagasse, wood, bamboo, jute, akwar?., elephant grass, waber-reef., plantain, msamba, cel lulose, etc.

length, diameter, cross-section, rings and hooked ends, etc:,

mono-filament, strands, crimped, single- knotted, etc.

smoothness, coatings, etc.

cement type, aggregate t y ~ e and grading, addi t ive types, etc,

water content, workability aids, &foaming agents, fibre content ,etc,

type of mixes, sequence of adding consti tuents, method of adding f i b re s , duration and speed of mixing etc.

conventional vibration, vacuum dewatering a a sprayed-up concrete rnemker, extrusion, guniting, etc.

conventional, special method, etc.

I n t h i s review, the uark has been divi.ded i n t o two

broad categories: 1,) thost$ findings based on purely

laboratory experinental work on specimens of f jbre - reinforced cement paste, mortar and concrete arid 2.)

those based on t e s t s on fibre - reinforced cerncnt

products s imilar t o those of asbestos cement c u r r e n t l y h use'

2,,3 MECHANICAL PROPEXTIES OF NfiTUXAL F I B R E - HEINFOl3CED CEMENT COP'IPOSITES PASED ON LABOlaITOlIY EXPERIMENTAL WORK

2.3.1 Tensile Strenqth

2.3.1.1 Coconut f i b r e ~ornpos_it-e-s_

The r e su l t s of d i r e c t t ens f l e tests by Da.s Gupta

et a 1 (13) on specimens of coconut fibre-reinfmxed

cement paste show t h a t tensile s t rength is increased by

the incorporation of fibres with the t ens i l e s:rength

increasing with increase i n fi!xe volume fraction up t o

a maximum a t about 4% (Vf for 3Gmm f i b r e len jths and

then decreashy f o r fur ther volume f rac t ion increase as

shown i n Figure 1 (13)-

6 7 8

f16Rf I'OL UME FRACTION, / p c r u n t )

--

strength based on Das Qupta, Figure 1 E f f e c t of f i b r e content on tensile

Paranrasivam and Lee (131,

With fibre volune f rac t ion fixed a t i ts optihm of 474,

t e n s i l e strength of the composite was seen to increase

w i t h increasing fibre length up to a maximum lt about

to 38mm and decrees& for any further fibre lerlgth

X

This i s i l lustrated i n FFgurc 2 (13)

%

I NBPE LENGTH, mm i

I i Agure 2. E f f e c t of fibre length on tensile ' s trength (13)

Consequently, Das Oupta e t a1 (13) concluded tha t

coconut f ibres , when Incorporated i n cement psste, a t

their optimum vcdume fract ion and length, improved the

t e n s i l e strength of composites by 50% They a l so defined

t h e optimum fibre content as 4% volume f r a c t i m f r o m

strength point of view.

Sla t e (8) also investigated the effects of coconut

f i b r e refnforcenient on t h e t e n s i l e strength of cement

mortar using varying fibre mass fract ions f o r strong

(1:2.75) and weak (I:.?) mortar. It was found t h a t

t ens f l e strength of coconut f i b r e - re inforce? mortar

as measured by br iquet te test was increased i n the

range of 5% t o 2'3% while using 25mm long fibres.

@ - - rn-Ll- m t n \

10.

Table 2 EFFECTS OF' INC~R'L;%A:ITPN OF C K O W T FIEZES

CN PROPERTIES CrF 0TCNCRETE ( 8 )

Each value is the average of four t e s t s , except that

E, PL, and toughness are for one test (only one reasured

s tra in) -

' S t r e s s from Mc/I, and strain is ave, of top and bottom.

"Area under stress-strain curve as for E,

No strain values beyond 85% max, load.

Andonian et a:L (23) showed that the ultimate tens i le

strength and corresponding Young's modulus of cellulose

fibre - reinforced cement - silica composites hcreased

gradually with fibre mass fraction up to about 0.06 and

Table 3 U l t i m a t e Strengths, Koduli of Elas tic3 ty and

Poissonls Ratfo of Sugarcane Bagasse Fibre

Reinforced Cement Composites based on Kacines and

Pama (145

Fibre U l t i m a t e strength Pbdulus of Po isson ' s r a t i o volume e l a s t i c i t y fract ion (%I ~ / r n ~ ~ / m m ~ x 1 0 ~

Direct tension t e s t

-- - - - - - .- -

1 3.87 32-40 0.202

2 2*95 0e54 0 235

a 2043 6,40 0.240 -I____

Compression test - -- 1 21003 13e06 0 c. 246

2 12.26 9 e 9 9 0,260

3 6e26 6,78 0,201

2,3,1,4 Ju te filxe-reinforced cement paste

Mansur and Azlz (27) found tha t tens i le strength of

fibre-reinforced cement paste could be increased by good

choice of both f ib re length and f i b r e volume f raz t ion

w i t h optimum values at 2 5 m and 3% respectively. This

is i l lu s t r a t ed i n S'able 4 1271,

Table 4 Effects of length and concentration of jute

fibre on strength parameters based on Mansur

and Aziz (27)

Fibre Fibre Comp-- 41ncr-. length volume resive ease in

fr ac- stren- tensile t ion gth

s tren- gth

tm) (Perc- m/m2) (iJerc- ent 1 ent 1

"ncro: *Incre Young's modulus ase i n ase i n (xlo3 ~/mrn2 f lenural flexural

strength toughn- ess

(Percent) (~e rcen t ) Comp- Tensile ress- ive

- - - - . - -. -. . - - -

+Relative to plain cement paste

2.3.2 Flexural S-trenqth

M x t of the literature under review considered the

flexural strength of fibre-reinforced cement composites

( 8 , 13? l 6 ? 17, 23, 31, 32, 35).

2.3,2.1 Cellulosi~: fib=+-reinforced cement co~os i t e s

The flexural strengths measured by Andonian e t a1

(23) fo r centre-poht loading on an Instron machine using

150 x 20 x 8mm test specimens ofgPinus Radiatal

14 s

cellulose flbre reinforced cernznt - silica mortar were

seen to increase gradually stith fibre maes fraction up

to the same mass fraction limit of 6% as for tensile

strength* Byond this 69: limit, measured values of

flexural strength remained nearly constant (Figuke 31,

Also, measured values of Young's modulus in flexure

remained approximately equal up to fibre mass fraction

< showing a slight decrease for furthcr m f

increase to 10%. See Fig. 4 (231,

0 2 L 6 8 10 12 30 ---

Eb- PREDICTED *- . .. --2-. -0 I 1

2 0 - - 8WNO i5 P

10 P 9 :!.. :: . - . .

0 2 L 6 8 Y3 12 MASS FRACTION OF FBRES. mf (%I

Figure .I$ Variation of Young's modulus in bending and in tension wit.4 mass fraction of fibres. Bars indicate the standard deviation.

Upperbound: E,=30 GPa, E,=3 7 GPa; lowerbound: E,=30 GPa, Em=23 GPa.

Coutts (32) in his own work, used various mass

f ract ions of beaten flax fibres i n cast ing specimens

(125 x 40m x varing thickness) of cement - silica (1:1) mortar cured under two pro-test conditions ar.d tested,

Flexural strength was found to be optimized at. fibra

loading of 8 - ( m f ) with values i n excess of 20

Mpa obtainable as shown i n Figure 5 (32).

Fig. 5 Effect of f l ax fibre content on flexural

strength a t various test conditions 132).

Table 6 P r o p e r t i e s of flax f ibre reinforced CE -- h d u l u s of r u p t u r e ( P h ) Fractrtrc tmuqhness

Fibre Freeness p e r c e n t . ~ q e CSP - by inass BH 513. 2 17.421.8

17,

h e strength V a l u e s SQ obtetLncd are comparable t o those

f r o m similar tests on :Pinus Radiate1 fibres-ccnrpare

Tables 5 and 6 (35, 3 2 i , Howver, unlike the case of

'Pinus Radiata' fibre-reinforced ceinent-silica mortar,

the degree of beating appeared not to affect t h e nmdulus

of rupture of the composite for 2 10% loading of flax

fibres used, This is illustr~ted in Fig, 6 C32).

Fig, 6. Effects of refining flax fibres on modulus of rupture (32).

In another work, mutts (35) s t d i e d the effect of

refining (beating) fibres from *Pinus Radiatal ?craft

wood pulp, the degree of beating being measwed by a

Canadian s tandard Freeness Tester ( CSF 1. Flexur 31 tests

carried out on 125 x 40 x 5-8mm specimens of the fibre-

of refining (bsating) stuciicd, opti~nurn condition

occurrd a t f iSR freeness value of about 553m1 CSF

and the sample had about 10% fibre nd as show in

Figure 7 (35). The work also showed tha t fle:mral

strength values e r e further f nfluenced by t h e type

pre-test kretitment of the specimens, See

(35).

also Mg.

I

FL~.-~ Effect of f i b K cbnteiitt onnf lexural s treng th

at various freeness values (3510

I _ - F~twe content l% by truss)

Fig, 8 Effect of ffbre content on flexural strength

following various preconditioning treatments

(35)

2-3-2.2 -nut fibre-reinforced cement composites

In flexural tests with coconut: fibre-reinforced

mortar, slate ((3) determined modulus of rupture, secant

modulus of elasti.city at 45% maximum load and propor-

tional l i m i t using SO x SO x 20Om beams cast f r o m 1:4

mortar of varying fibre contente The mcdu1.u~ of rdptme

results did not show any clear effect of the presence of

fibres as seen from Table 2.

Das Gupta et a1 (131 unlike Slate ( 8 ) arrived a t

d e f i n i t e conclusions on the effect of coconut f ibre

loading on t h e modul.us of rupture of the composite. By

means of flexural tests an specimens prepared under

optirmun casting pressure pre-determined from rn earlier

experiment (Fig . 9) and incorporating optimun fibre

20,

lengths, they established that modulus of rup tu re of

the composite increased with increasing volurre fraction

2 reaching a maxirmun of a b u t 5-4 ~ / m n and decr:easing

FIBER LENGTH 38 mm (1.5 in) I' 1 ' 1 2

VOLUME FRACTION 3 %

I) '$

pressure and

modulus of rupture for coconut fibre

rehforced cement: paste, (13).

They concluded that by using coconut fibres at

optfmum content: and length, flexural strength of the

composite can be improved by 75%.

FIBER LENGTH 38 mm (1.5 in)

I CASTING PRESSUAE 3.1 ~ / m m

(450 ps i )

1 I I 1

' 1 2 3 L . 5 6 n

VOLUME FRACTlON ('I.; - - - ig, lo-- T?d.ationSKp &tween modulus of -Epture of

composites and volume fraction for coconut

fibres (13).

Ramaswamy et a1 (31) tensile spl i t t ing strength

and modulus of rupture tests on coconut fibre-r.xinforced

concrete using 10C x 100 x 600mm prisms with op",mum

sand content gave lower 284ay strength values than

those of plain concrete specimens, Generally, the

flexural to compressive strength ratio was improved for

various test ages as shown i n Table 7 (31).

- .

Table 7 Flexural strength data of fibre conQ.&e (31)

Ratio of modulw of rupture to cube compressive strength a t

Type of concrete 3 days 1week 4 weeks 1 2 weeks U

1 Plain coneetb (no fibre) Om14 0.19 O O X ) 0.22

2 Concrete with i$ jute fibre 0017 0.24 0.26 0,28

3 Concrete wlth 1% coir fibres 0017 0-22 0.22 0.26

4 Concrete with i% bamboo fibres 0014 0.20 0021 0,23

Cubes 100 mm, modulus of rupture 100 x 100 x 600 m prisms.

2.3.2.3 Si-sal fibre-refnforced cement composit~

Swift and Smith (16) studied the effect of sisal fibre

reinforcement on hbth cement mortar and concrete. Generally,

the results showed improvements in flexural strengt'ns. A

sumnary of these results is shown in Table 8 (16).

Table 8 Modulus of rupture of s isal fibre reinforced concrete based on Swift and S m i t h (16)

Mix praportion Water Fibre Fibre Curing Specimen Modulus ( cement ; sand ; cerr ent length volume period size of coarse aggre- ratio f rac- rupture

gate) tion hd (%I (days) (4 d m 2

Persson and Skarendahl (17) also investigated sisal

fibre-reinforced cement mortar first, usltng choppcd

fibres (15-50 mm) and later with continuous f i k r e s (up to

'J1F00 mm). They found that continuous fibres produced a

more pronounced increase in flexural strength. Typical

strers-strain curves for the tvo cases are shown in Rgs sod 12 (17). -- -

- Linit'of proportionality for unreinforced concrete

Limit o f proportionalily for s ~ s a l fibre concrete

Sisal fibre concrete

Unteinforced concrete

1 I

a -

with continuous sisal fibres based on Ekrsson and

With continuous fibres of fixed volume f rac t ion , the

stress-strain behavfarr for changing qualify of matrix

was established (Fig, 13) and with increasing volume

f r a c t i o n but constant matrix qualtty the cormsponding

stress-strain pat te rn was established too (Fig. 14). --

I Increasing n;atr.ix cjirality

Figure 13. Effect on t h e s t ress -s t ra in behaviour -for continuous s i sa l f i b r e concrete when t h e mat~ix quality is changed, based on Persson and Skarendahl ( 17)

/ -- I increasirtg voltlme-I fractiori of fibres

Figure 14. Effect on the s t ress -s t ra in behaviour fo r continuous s i s a l f ibre concrete f o r changing volume f rac t ion of f i b r e s (17).

2,3,2,4 Ju t e fibre-reinforced cement composites

Flexural tests on j u t e fibre-reinforced cement

composites carr ied out by Mansur and Aziz (27) show

c l ea r ly t h a t t he f lexura l s t rength of the composite

increases with f i b r e volume f rac t ion up t o a maximum a t

an optfmum value of about 3% ( V f ) f o r fixed f i b r e

lengths and s imilar ly with f i b r e length a t an optimum

value of about 2 5 m f o r f ixed f i b r e volume fraction.

These are well i l l u s t r a t e d i n Table 4,

On the other hand, l'\amaswamy et a1 (31) carr ied

out similar t e s t s with ju te f i b r e reinforced cement

composites with inconclusive r e su l t s except for imyrov$-

f l exu ra l t o compressive s t rength r a t i o shown i n Table 7,

2,3,3 Compressive Str-eat

While S l a t e ( 8 ) observed t h a t compressive s t rength

of cement mortar was not much affected by the presence of

coconut f i b re s i n the composites (Table 21, Das Oupta et a1

(13) concluded a f t e r t h e i r tests on coconut f i b r e - refnfbrced cement paste t h a t the ultimate compressive

s t rength of t h e reinforced composite was l e s s than t h a t

of t h e p l a in cement paste, They inferred t h a t a s t he

f i b r e volume f r ac t ion increased, t he compressive s t rength

decreased up t o a maximum reduction of about 10% a t 6%

volume fract ion,

Ramaswamy et a 1 (31) carr ied out compressive

s t rength t e s t s on 1% volume f rac t ion of co i r , j u t e and

bamboo fibre-reinforced concrete, Their r e su l t s showed

t h a t only c o i r f i b r e s performed as w e l l a s p la in

concrete whi le bamboo and jute fibre concretes showed

lower compressive strengths than equivalent pla in

concrete. See Figure 15 ( 31 1,

(Cont~nuously curca In w a t e r ) M ~ X 1:3.58 : 2.87

W/C 0.65

Figure 15. Compressive s (31)

However, it was observed cnaL me ~ J L ~ I I I U I I r l u ~ e

volume fractions for compressive strength are 0,5%

for j u t e and bamboo fibres and 1% for coir filres

as shown in Figure 16 (31).

[a ) JUTE 7 ( c ) BAMBOO

F i g u r e 16. Compressive s t r e rq th ratio for wrying fibre content (33.1

2.3.4 Fracture Touqhnes:

2.3.4,l Cellulosic fibre-reinfaxed cement composites

Fracture toughness t e s t s by Amlonian et a1 (23) was

w i t h notched beams (150 x 20 x 8mm) of cellulose fibre

reinforced mortar with crack depth to spedmcn width

ra t io of 0.50 subjected to three ~ o i n t bendir a,

Specific work of f rac ture ( R ) was d e t d n e d from Guxey's

irreversible work area methd (21. A summary of the

experimental results i s shown on Table 9 (23).

Table 9 Mechanfcal propertics of cellulose-cement ( ! 3 )

Specific

Mass fraction Modulus (GPa)

of Cellulose

Strength ( M 'a) work 05 fracture R

01 standard deviation, sample s i z e = 6

+*I standard deviation, sample s h e = 15

+I standard deviation, sample size = 5

Compared to values for asbestos-cement a t equivalent fibre

mass fractions (22), R is a h u t 5% - 100% less, For example,

2 for mf = 1W, R + 1.6 .t OO6KJ/m for asbestos cement md L

2 0.97 + 0.17KJ/m for cellulose cement composite, -

Cautts (35) also tested refined wood fibre-reinf3rced

mortar specimens (125 x 40 x 54mm), fracture energy ~ e i n g

calculated from the area under the load - deflection m e

and fracture toughness from fracture enerw cross section area of s >ecimen

It was found t h a t fngcmzzal, fox constant mf of fi >re,

toughness tended to decrease as the fihre was furtler

beaten and that there was a rapid improvem?nt i n

toughness as the fibre content was increased as sh >wn

in Figures 17 and 18 (3511

Figure 17. Effect of freeness an fracture toughnes s a t various values of fibre content (35:

- F ~ b e cnnren! (3'. bvmassl ----- I

igure 18. Effect of fibre content on fracture toughness following varioua pre- conditioning treatments (35)

Sn another investiga43on, Coutts (32) studiec t h e

effect of refined flax fibre incorporation in mor'ar on

the fracture toughness of the composite, A f t e r tt s t s

on 125 x 40mm strips of varying thickness it w s jowd

that fracture toughness increased as the fibre cot tent

increased, further toughness increase being obser?ed

frm w e t samples as can be seen in Figure 19 (32).

I

I L E * - I 3 I ? FIBRE 1 OH7Lhi 1 % t ly a o r r l l~ Figure 19. Effect of f-%b?Pco=emonir

fracture toughness at various test conditions based on Coutts (32)

In general, these R values were approximately half the

corresponding values for the 'Pinus Radiatal coqosite.

2.3-4.2 Sisal fibr_e-lc_elnforced cement comositcs_

Persaon and Skarendahl (17) carried out frar tui-e

toughness t e s t s on sisal fibre-reinforced mortars and

concluded that toughness is higher fo r s i sa l f ibre

concrete than for plain concrete. However, the i i report

d id not include any experimental results to back up

the above conclusionm

2.3.4-3 Coconut and Jute Fibre-reinforced cemer $ ~p_mpos ites

The effect of coconut fibre on the fracture

toughness of the composite was investigated by S l a t e (8).

By measuring modulus of bughness f r o m the area w d e t

the stress-strain curve at 05% of msximurn load, if was

observed that moduLus of toughness of the reinforced

composite increased 95% and 60% for 0.00% and O . l t % fibres

respectively. See Table 2,

Rmswamy et a1 (311 reported that fracture

toughness was distincbly higher for jute, coir am

bamboo fibre-reinforced mortars. This is a purel!

qualitative observation as there were no experimertal

results to substantiate it, However, the work of Mansur

and Aziz (27) mnfirms this observation for jute fibre-

reinforced copsites only (Tabic 4).

2.3.5 *act Strenqth

Within the literature i n review, only th?:ce apers

considered t h e effect of f i b r e incorporation orl tle

impact strength of fibre - reidorced cement compcsites ( 3 , 27, 31).

Rarnamamy et al (31) compared the impact encrgy at

first crack of plain concreka specimens to those c f

jute, bamboo and coir fibre - reinforced concretes.

They observed that the values of impact energy me~sured

by the drop ball method far the three types of fl bres

were about 10 * 20% higher than those for unreinfcrced

specimens as seen in Table 10 (311,

Table 10, Results of impact s t rength tests on plz i n concrete, jute, bamboo and c o i r fibr concrete 12 1 !

Average impact energy N o c (kg c m ) a t f irst crack blows ror rauure on v i rg in specimens --

Type of concrete slabs beams slabs beams

Plain 0% fibres 240 5 5 2 3 Jhte 1% fibres 290 68 5 5 Bamboo 1% fibres 275 61 3 3 C o i r 1% fibres 290 60 4 4 Coir % X fibres 2 70 61 4 3

Note: Slab specimens 300 x 300 x 25 rnm were simp11 supported at all four edges and beam.

Specimens 330 x 100 x 25 m were simply supported only a t tvm opposite shor t edges.

&ah value imlicated in t h e Cable represents t he mean of s i x specimens.

Weight of drop ball: Skg for slabs and 1 kg :'or beams,

Height of a l l 480 - 580 m

This improvement i n impact resistance of nab ral

fibre-reinforced concrete was also observed by Si:*askar

and Kumar ( 3) as a result of inpact tests on coco~ iut

and jute fibre-reinforced concrete the results of which

are shown in Table 11 (31,

Table 11. I'mpact sk-sngths of r a ~ i o u s n a t u r ~ l fi:m reinforced concretes based 0.1 Siraskar and Kumar ( 3 )

-.. - -- Impact strength, N c m / m 2 .--. - ---

Concrete type Curing periods, d ~ y s -. -

lo Plain concrete 135 20 3 608 2. 3% coconut fibre reinforced 473 1,148 ! ,093 3, 3"/,ute fibre reinforced 270 473 !,025

Considerable irnprovenent i n impact strength as

observed by Phnsur and Aziz (27) from resu l t s of :ests

w i t h j u t e fibre-.reinforced ceinent paste with f i b r ?s a t

optimum length and volume fraction, The maximum

increase was i n the region of 400% of the value f x

plain concrete.

2.3.6 Other Pro~ert ies of Natural .- Fi-b~q-Reinforc Cement Composites

Density of fibre-reinforced composites were

found to decrease with increase In f ibre mass fra:tion

while water absorption increased w i t h increase i n mass

fraction (35) remaining d e p e d e n t on density of

composite ( 32).

Cment content and sand gradation were t he

control l ing fac tors for watertightness (17).

Abrasion resis tar1~3, k k ~ m a l rtnd acouetie p~ . p-:L c: I =.c:

of f ibre-rei.nEorced cement composites were good,

par t icu lar ly with sisal, jute and sugarcane bagas:@

fibres (14, 16, 271,

Creep &is seen to be somewhat higher while

shrinkage was substantially lower than fo r plain

concrete (31),

2e4,1 Coconut Fibre-Keinfarced Cbrruqated --.I-u- Sheets - and Slabs -

The investigations made by Parumasivam et E L

(34) was aimed a t f inding a simple simple and

systematic method of casting corrugated coconut fibre-

reinforced slabs su14able for use i n l o w cost horsing

f o r developing countries. Tests were carr ied out on

corrugated slabs made from cement-sand (1: 0,s) mc lrtar

retnforced with coconut fibres of varying volume

f rac t ion and aspect ratio, The test r e su l t s sholr that

2 a f lexura l strength of up t o 22N/m i s obtalnab .e

using optimum values of V f = 3% and fibre length =

25 rnm, See Figs . 20 and 21 (34).

- 25 rnm --- 38 mrn

Vo lume f r a c t i o n ( "I.) igo 20 Comparison oi rncx2ulm or rupcure u r n

volume fraction for corrugated coir fibre Slab (34)

fibre length at 3% volume fraction ( 3 1.1

The above f lermral strength value Is higher 'tha I the

dnimum bending strength of 15.7 PN/m2 iqx?cifi d

for asbestos - cement corrugated sheets ( 5 1.

sound absorption coefficients of 3 - 8% for low

frequency and i:hermal conductivity of 0.64 W/$K

(Tables 1 2 and 13) which compare w i t h those for

asbestos cement boards (Table 14).

Table 12. Thermal conductivity of coir f i b r e ccrrugated slabs (34)

Specimen Thermal - conductivi' y

Volume ~ i b r e length Thickness (W/mOK) fract ion (mm) (mm)

Table 13, Sound absorption coefficient (values are in % absorbed) for coir fibre corrug ited slabs based on Paramasivam, Nathan ald Das Gupta (34)

S o u . absorption coefficie nt (961 for

Frequency

121 250 500 0 200C 4000 Specimen - Volume Thickness f r ace

Table 14. Typical thermal conductivities of building materials (34)

-- -- Thermal

mterials ~~X'ql~tiiiit I W/m0K ) -* --- +- I..._ -I.- ..-YI-

AeSes tos cernvlt imarrs O o E 5 Asbestos insuJ-ating boards 0,10&.0,13 5 Fibreboard ( ceiiiei te 0,C 5 Plaster board 0,1; 3 Hard bard C,2C 1 T i l e s , clay G,8C 6 Wood C n l L 4

Singh (15), on h i s part, compared the rhysical

properties of coconut fibre-reinforced corn gated

roofing sheets and asbestos roofing sheets. The

comparison is sho-rn in Table 15 ( I S ) *

Table 15. Comparison of physical propertie: of coir f ibre reinforced roofing sht :ets and aebestos roofing sheets base l on Singh (15

Coc0l Characteristics and reil Properties roof:

Pitch of corrugation, mm 146 146 ~ e p t h of corrugation, m 40 48 Length of sheets, m 1.5-2.0 1.5-3.0 Width -of sheets, m 1 .O 1.05

Weight, kg/m 2

Breaking load of 60 an, ~ / m Breaking load

12 eS-12mO 1 ) a 5 for a span

50 I

at a span of 100 an, ~ / m 19 i0 Thermal conductivity, k, cal/cm/m2 0.09 0, !4 Water permeability through finished surface i n 24 hours almost nil - Acid resistance as p l.Se : 59lLl970, N/m ?? 9.30 x toms3 9 ,26x1f3

2,4,2 Sisal Fibre-Reinforced Corruqated Slabs

In Uselotte Johanssm's (33) work on sisal Xbre-

reinforced corrugated sAeets, a draft standard f lr

t e s t methods for corrugated sheets of natural f i x e o tries was presented, Sheets ?f varying

concrete sultab!eyor develop~cement /sand - rat LO:-

A) 1:2, B) 1:3, C) 1:4, Dl 1:7 and a f ibre

volume fraction were produced and la ter tested i l

A) and B) passed the strength tests with large nwgins

uhlle those of mixes C) and D) were near the

~ l s o all the sheets passed the watertightness t e s t ,

Table 16. Laadbearing capadty i n kgf(~) at thc l i m i t of proportionality for s isal f ibre corrugated sheets based on Liselotte Johansson (33)

I

Group A B C D 205(2010) 215(2108) 140 (1373) 11 Q(1569 210 (ZOSS) 270 (2647) 115 ( ' - 290(2843) 200(1961) 165('

Mean value 232(2275) 228(2235) 140 ( '

Table 17. Loadbearing c a m Q at the l imit of proportionality in kgf per me=@ width of sheet, k&m ( N / d for s i s 11 fibre! corrugated sheets &is& on Mlelot te Johansson (33)

G ~ U P A n c D

Wan 288(2824) 280( 2745 1 171 (1i ;76) 196(1922)

For sisal fibre-reinforced products. Persson and

Skanderahl (17) considered design criteria such as

loads, stresses, choice of safety factor: , crack wi*,

watertightness, impact resistance, fibre resistance

and so on. They considered also, the actual

prdductfon process f o r sisal-fibre c o n a t e sheets on

the basis of

(I) Material flow using

a) Chopped fibres

Mixing-Casting-Wing Storing water

b) Continuous fibres

sisal -"-\ \ sand Mixing-Ca~ting-Arrir 3-Storing

water --&" (If) Level of Production

a) Production at the village level - Figure 22 (17)

b) Production by small-scale industry - Fig, 23 (17)

C ) Production i n mechanized i n d u s t r i e s - Fig. 24 (17)

CEMENT

SAND

. . . . . . .. .. .

WATER

@ SISAL F I B R E S

ifler rags1 STORING

Fig, 22, Production a t the vil lage level when chapped f ibres are used (17

I CEMENT

i SISAL F I B R E NETS

MIXING CAST IN G

1 CO~JTINUOUS FEEDING i /'

. I , K

o: laminate I

A

CON? INbOUS MOULD- --- - . . .-

. . -

2.5 OTHER OBSERVATIONS ON TESTS AND RES JLTS 3-.

In the literature under review, the m !thocis of

f ibre extraction and treatment are m a t i s !actory.

There is need t o establish economical and lare & ; f i a t

f ibre preparation processes.

The Absence of either international s :andads or

local standanis for the testing of f ibre r!inforced

cement composites has led t o a p r o l i f e r a t i m of casting

and testing parameters such as specimen 6i :el age of

t e s t , casting and curing conditions, type )f cement

(ordinary portland or rapid

aggregate - to name just a

used briquette tests for d i r e c z censue r e iung co

ASTM t es t method, C 190-72 - Tensile Strmgth of

Hydraulic Cement Mortars (4) while Andonia 1 et a1 (23)

used rectangular strips 150 x 20 x 8m t e b d i n an

Inskon machine apparently to no w i s u n g ttandards on

f i b r e concrete.

Flexural tests m e dn different beam sizes a d

loading arrangements and these t w o factors are known to

affect modulus of rupture values (25 1. In fact, ofly

Andonian et a1 (23 1, Cbutt~ ( 32) and Cout ;S (35

maintained some consistency in flexural st-ngth and

fracture toughness tests.

Even in the papers on fibre reirWwccrJ cement

prducts , only one stdndard (El) for fibrc reinforced

concrete sheets was mentioned. Other star3ards used

relate to corrugated sheets of asbestos cfnent (1, 5 , 11,

28, 29). Zn fact, most of the t e s t s =re cone to asbestos

cement t e s t procedures. Much progress w i l l be made in

the quality control of f ibre reinforced crrnent products

if t h e draft standard proposed by Uselott e Johansson

(33) is adopted.

Presently, It is d i f f i c u l t to correlcte tho

results of the same tests by the various investigators.

None of the researchers tried t o invrstigate the

possibility of finding general optimum vzlues of volume

fraction and fib= length for strerigth fox each type

of vegetable fibre,

Finally, only two works (13, 23) t r i ~ 9 an analytical

verification of their results. The rest vzre silent on

that aspect.

FIBRE PREPARATION AND TESTS

3.1 FIBRE EXTRACTION AND TESTS

coconut husk. First, the husks were s p l i 5 open and

after the in ter ior nut had been removed, :hey (husks)

were broken into three or more pieces . E I& husk piece

wan IR+PY snf+~nnrl hv b a t i n n and than *n,lcd in w a f ~ r

the natural c

to rid t h e m c

The fibres were swjeccea ro cesrs KO aecxnune cne

tensile strength and specific gfavity.

Fibres for the tensile t e s t had both ends glued

to timber plates as shown in Figure 25.