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DURABLE STRUCTURES LNEC Lisbon 31 May - 1June 2012

EVALUATION OF THE DURABILITY OF CONCRETE MADE

WITH GRINDED GLASS AGGREGATES

Authors:

Sara de Castro; Jorge de Brito


Table of contents Introduction Objectives State of the art Experimental campaign

Aggregate tests Concrete mixes Fresh concrete tests Curing conditions Hardened concrete tests

Discussion of the results Aggregates Fresh concrete Hardened concrete

Shrinkage Water absorption by immersion Water absorption by capillarity Carbonation Chloride ion penetration

Conclusions

ICDS12 International Conference DURABLE STRUCTURES: from construction to rehabilitation LNEC Lisbon Portugal 31 May - 1 June 2012

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Glass

Glass is globally used as container, bottles, flat glass for window screens, light bulbs, televisions and computer screens

Over the past 10 years and due to new environmental regulation, which sets a tax for every tonne of waste in landfills, there was a greater concern and an effort to produce concrete with aggregates from recycled glass.

Introduction


Objectives

Assess the durability of concrete made using glass recycled aggregates as a replacement of natural aggregates

evaluate the variation of CGAs durability with the replacement ratio of natural aggregates (NA) by glass aggregates (GA) with different sizes;

increase the knowledge on the use of glass aggregates in concrete manufacture.


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Literature review (scientific publications, MSc and PhD theses, conference proceedings, etc.)

experimental campaigns associated with the use of glass aggregates on the durability-related performance of concrete:

Lam et al. Limbachiya Wang and Huang Kou and Poon Shao et al. Ismail and Al-Hashmi

State of the art


Lam et al. (2001) and Limbachiya (2009) observed that the water absorption decreased with the increase of glass aggregates;

Wang and Huang (2010) observed that fine glass used as aggregates created a denser structure and more resistance to chlorides and sulphates penetration. Kou and Poon (2008) also observed an improvement in the resistance to chloride penetration;

Kou and Poon (2008) and Shao et al. (1999) obtained a decreased shrinkage with the increase of incorporation of glass aggregates;

in general, the authors used either metakaolin or fly-ash to mitigate the effect of ASR. Ismail and Al-Hashmi (2008) observed a pozzolanic effect when replacing 20% natural sand by glass sand.

State of the art


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Aggregates tests:

Grading analysis NP EN 933-1 (2000) and NP EN 933-2 (1999) Density and water absorption NP EN 1097-6 (2003) Bulk density NP EN 1097-3 (2003) "Los Angeles abrasion LNEC E-237 (1970) Shape index NP EN 933-4 (2002)

Experimental campaign



Concrete mixes:

RC reference concrete

C05G concrete with replacement ratio of 5% of coarse natural aggregates with coarse glass aggregates



C05F concrete with replacement ratio of 5% of fine natural aggregates with fine glass aggregates



C05FG concrete with replacement ratio of 5% of coarse and fine natural aggregates with coarse and fine glass aggregates




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Fresh concrete tests:

Slump NP EN 12350-2 (2002) Fresh density NP EN 12350-6 (2002)



Curing conditions

Laboratory environment Wet chamber



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Hardened concrete tests:

Drying shrinkage LNEC E-398 (1993) Water absorption by immersion LNEC E-394 (1993) Water absorption by capillarity LNEC E-393 (1993) Carbonation LNEC E-391 (1993) Chloride ion penetration Nordtest NT Build 492 (2004)



Shrinkage 2 specimens Water absorption by immersion 4 specimens Water absorption by capillarity 4 specimens Carbonation 4 specimens Chloride ion penetration 4 specimens

Total duration of this experimental investigation: 18 months


020406080

100120140160180

DryingSkrinkage

Waterabsorption

byimmersion

Waterabsorption

by capillarity

Carbonation Chloride ionpenetration

Total

Specimens 20 40 40 40 40 180

Specimens


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Discussion of the results Aggregates

Aggregate Fine sand Coarse sand Rice grain Gravel 1 Gravel 2 Fine glass Coarse glass

Dry density (kg/m3) 2585 2627 2724 2740 2720 2513 2525

Water absorption (%) 0,1 0,05 0,9 1,3 1,0 0,75 0,39

Bulk density (kg/dm3) 1500 1550 1440 1430 1430 1360 1360

LA abrasion (%) - - 34,2 30,8 31,9 - 38,4

Shape index (%) - - 18,6 17,9 12,0 - 30,5

The GAs density was a little lower than that obtained for the NA;

the GAs performed as well as the NA in terms of water absorption;

GAs showed a worse result of the shape index compared to the natural

aggregates.


Fresh concrete tests Slump

The W/C ratio varied according to the particle size and replacement

ratio, in order to maintain the slump within the limits shown;

the fresh concrete density decreased with increasing amount of glass

aggregates.

Discussion of the results

Fresh density

95

96

97

98

99

100

0% 5% 10% 15% 20%

Fre

sh d

en

sity

in c

om

par

iso

n w

ith

th

e

refe

ren

ce m

ix (

%)

replacement rate

CC

CF

CFC


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Hardened concrete tests Drying shrinkage

The mix of fine and coarse aggregates featured the most favourable performance . This was

due to the combination of fine aggregates and their adhesion to the cement matrix together

with the lower w/c ratios of the coarse mixes;

the mix with better results was the C10FC, which shows the lower shrinkage value at 91 days.


0,80

0,90

1,00

1,10

1,20

1,30

0 5 10 20

Shri

nka

ge a

t 9

1 d

ays

of

test

ing

in

com

par

iso

n w

ith

th

e r

efe

ren

ce m

ix

replacement rate

RC

Coarse

Fines

Fine and coarse


Haredened concrete tests Water absorption by immersion

The behaviour of the glass concrete mixes was very similar to that of the reference concrete. The

variations of the values are between -1.28% and 9% resulting in very close values between all the

mixes;

these results may be due to the low water absorption of the glass aggregates and the micro structural

similarity of the mixes produced.


0,90

0,94

0,98

1,02

1,06

1,10

0 5 10 20

Wat

er

abso

rpti

on

by

imm

ers

ion

in

com

par

iso

n w

ith

th

e r

efe

ren

ce m

ix

replacement rate

RC

Coarse

Fine

Fine and coarse


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Hardened concrete tests Water absorption by capillarity

A better behaviour was found for concrete mixes with both fine and coarse aggregates, for all replacement

rates, and for fine and coarse aggregates up to 10% of substitution;

the mix C20F was characterized by high harshness and w/c ratio which contribute to the increase of air

voids, promoting a porous structure and leading to a mediocre performance of this mix.


0,50

0,60

0,70

0,80

0,90

1,00

1,10

1,20

0 5 10 20

He

igh

t o

f w

ate

r ab

sorb

ed

by

cap

illar

y ac

tio

n in

co

mp

aris

on

wit

h t

he

re

fere

nce

mix

(%

)

replacement rates

RC

Coarse

Fine

Fine and coarse

0,50

0,60

0,70

0,80

0,90

1,00

1,10

1,20

1,30

0 5 10 20

Wat

er

abso

rpti

on

by

cap

illar

y ac

tio

n

in c

om

par

iso

n w

ith

th

e r

efe

ren

ce m

ix

(%)

replacement rate

RC

Coarse

Fine

Fine and coarse


Hardened concrete tests - Carbonation

In general, the carbonation depth is similar or lower than the value of the reference concrete for any age;

A slight relative improvement of the carbonation depth for concrete with advanced ages was found;

the variations between those concrete mixes and the reference mix are so modest that it can be said that

the glass aggregates contributes in the same manner for the concrete matrix as natural aggregates do.


0,65

0,75

0,85

0,95

1,05

1,15

1,25

1,35

1,45

1,55

1,65

7 28 56 91

Car

bo

nat

ion

de

pth

in c

om

par

iso

n w

ith

th

e

refe

ren

ce m

ix (

%)

Age (days)

CF

C05C

C10C

C20C

C05F

C10F

C20F

C05FC

C10FC

C20FC


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Discussion of the results Hardened concrete tests Chloride ion penetration

It is possible to observe that the results remained approximately constant as the replacement

rates increase, so it was concluded that glass aggregates confer chloride penetration

performance in concrete identical to natural aggregates.

0

0,2

0,4

0,6

0,8

1

1,2

1,4

1,6

1,8

0 5 10 20Ch

lori

de

pe

ne

trat

ion

de

pth

in c

om

par

isio

n

wit

h t

he

re

fere

nce

mix

(%

)

replacement rate

RC

Coarse

Fines

Fine and coarse


The workability of glass concrete is highly affected by the particle size; it is necessary

to add water, increasing the w/c ratio from 0.55 to 0.58, for a 20% replacement of fine

aggregates;

a clear loss in density values is observed with the increase of glass content; this

decrease is motivated by the lower density of the glass particles;

in general, a decrease in the 28-day compressive strength values is observed as the

glass content increases;

in the water absorption by capillary action test the mixes that show a better behaviour

are those with both fine and coarse aggregates for all replacement rates and the fine

and coarse mix at 10% of replacement;

Conclusions


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Conclusions the performance of glass concrete in the water absorption by immersion test is very

similar to that of the reference mix; this result is due to the low water absorption of

glass aggregates and the similarity between the microstructure of the executed

mixes;

an improvement in the carbonation depth was found for advanced ages; in general,

the glass concretes between 7 and 28 days of testing show an increase in the

carbonation depth as the glass content increases while, for concrete between 56 and

91 days of testing, the opposite is observed; therefore, there seems to be some

refinement in the cementitious matrix of glass concrete at old ages;

the behaviour of the fine, coarse and both aggregates mixes are very similar to the

behaviour registered by the reference mix in the chloride penetration test;


Conclusions

the shrinkage of the concrete with glass aggregates is very similar to that of the

reference mix; however, the best shrinkage values are obtained in the mix with both

fine and coarse aggregates.

In general, concrete with glass aggregates is feasible in normal practice. It was verified,

for most cases, that glass confers the concrete very similar features to natural

aggregates. In most cases, there is a variance range of 15% from the reference

concrete which, taking into account experimental errors, is a quite acceptable difference.


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