towards better understanding of concrete containing recycled concrete aggregate

Hindawi Publishing CorporationAdvances in Materials Science and EngineeringVolume 2013 Article ID 636034 8 pageshttpdxdoiorg1011552013636034

Research ArticleTowards Better Understanding of Concrete Containing RecycledConcrete Aggregate

Hisham Qasrawi and Iqbal Marie

Civil Engineering Faculty of Engineering The Hashemite University Zarqa 13115 Jordan

Correspondence should be addressed to Hisham Qasrawi hisham qasrawiyahoocom

Received 20 May 2013 Revised 27 August 2013 Accepted 27 August 2013

Academic Editor Amit Bandyopadhyay

Copyright copy 2013 H Qasrawi and I Marie This is an open access article distributed under the Creative Commons AttributionLicense which permits unrestricted use distribution and reproduction in any medium provided the original work is properlycited

The effect of using recycled concrete aggregates (RCA) on the basic properties of normal concrete is studied First recycled aggregateproperties have been determined and compared to those of normal aggregates Except for absorption there was not a significantdifference between the two Later recycled aggregates were introduced in concrete mixes In these mixes natural coarse aggregatewas partly or totally replaced by recycled aggregates Results show that the use of recycled aggregates has an adverse effect on theworkability and air content of fresh concrete Depending on the watercement ratio and on the percent of the normal aggregatereplaced by RCA the concrete strength is reduced by 5 to 25 while the tensile strength is reduced by 4 to 14 All results arecompared with previous research As new in this research the paper introduces a simple formula for the prediction of the modulusof elasticity of RCA concrete Furthermore the paper shows the variation of the air content of RAC

1 Introduction

The average world production of concrete in our rapiddeveloping industrialized world is about 6 billion tons peryear [1] which has an adverse impact on the environmentSince earth is the source of the aggregates (either naturalor crushed) then obtaining these amounts would have anadverse effect on the environment Furthermore demolishingconcrete structures and dumping the concrete rubbles wouldaggravate the problem Therefore recycling constructionmaterial plays an important role to preserve the naturalresources and helps to promote sustainable developmentin the protection of natural resources thus reduces thedisposal of demolition waste from old concrete [2] Hencerecycling concrete wastes becomes important in getting ridof the demolished concrete which accumulates with timeFor example the amounts of demolished buildings in Europeamount to around 180 million tons per year [3]

Old concrete and masonry that have ldquoreached the endof the roadrdquo can be recycled and used not only as aggregatefor new concrete but also for a number of other applicationsin construction [4] For example since 1982 the ASTMdefinition of coarse aggregate has included crushed hydraulic

cement concrete and the definition of manufactured sandincludes crushed concrete fines [4] Similarly the US ArmyCorps of Engineers and the Federal Highway Administrationencourage the use of recycled concrete as aggregate in theirspecifications and guides [5] Several references [3ndash12] havepresented literature survey and research results in the fieldof the use of recycled aggregate concrete and masonry andtheir effect on maintaining the environment Based on thesereferences the advantages of using recycled aggregate inconcrete can be summarized as follows

11 Environmental Considerations SBM [12] provided briefenvironmental considerations regarding the use of concretequoted in their own words ldquoIn this time of increasing atten-tion to the environmental impact of construction and sus-tainable development Portland cement concrete has much tooffer (1) it is resource efficient-minimizing depletion of ournatural resources (2) it is inert making it an ideal mediumin which to recycle waste or industrial byproducts (3) it isenergy efficient it is superior to wood and steel (4) it isdurable continuing to gain strength with time and finally(5) it is recyclable fresh concrete is used on an as-needed

2 Advances in Materials Science and Engineering

basis (whatever is left over can be reused or reclaimed asaggregate) and old hardened concrete can be recycled andused as aggregate in new concrete or as fill and pavementbase materialrdquo Parekh and Modhera [13] considered the useof RCA in concrete as an appropriate and ldquogreenrdquo solution tothe anticipated increased world-wide construction activity

12 Economic Factors SBM [12] considered that recyclingconcrete is an attractive option for governmental agenciesand contractors alike because most municipalities imposetight environmental controls over opening of new aggregatesources or new dumping areas By time the increase of thecost of starting new quarries is increased and will be fartheraway Hence the cost and transport distances of conventionalaggregates could continue to increase as sources becomescarcer Since landfill space is limited and can be far awayespecially in urban areas the disposal of demolished rubblesbecomes costly and dumping fees will most likely rise asconstruction debris increases and the number of accessiblelandfills decreases Such situation was faced in Hong Kongand recycling aggregate was an attractive solution [14]

13 Solving the Problem of Lack of Materials According toKawakami and Tokshige [15] utilization of concrete that usesrecycled aggregates as a construction material is expected tocontribute to solving the issue of lack of raw materials andthus would allow the construction of infrastructures usinga circulatory system for resources Such situation was facedin Hong Kong and recycling aggregate was an attractivesolution [14]

14 Other Uses While unprocessed RCA is useful to beapplied as many types of general bulk fill bank protectionsubbasement road construction and embankments pro-cessed RCA can be applied to new concrete including leanand structural grade concrete soil-cement pavement basesand bituminous concrete [9] Moreover it has been used toproduce high strength concrete [10]

The use of RCA for the production of concrete involvesbreaking demolished concrete into materials with specifiedsize and quality These materials can then be combined toproduce aggregate of a predetermined grading and hencecan be used in concrete Moreover the steel reinforcementcan be recycled and then can be used as structural concretereinforcement reducing the effect on natural resources

In this research the authors investigate the use of RCAin normal concrete mixes and study the possible effects onsome of the concrete properties Also the research will tryto arrive at some unique relationships that can be used inthe prediction of the properties of RCA concrete Hence triesto help in providing specifications that can be applied toRCA and RCA concrete The research is a continuation of apreviously conducted research on the use of RCA in concrete[16]

2 Common Specifications

Because of the widespread use of RCA in concrete severalagencies have adapted special standards and specificationscovering the use of these materials in concrete In 1994RILEM [17] issued the ldquoSpecifications for concrete withRecycled aggregatesrdquo In these specifications the RCA isclassified into three main categories (a) type I aggregateswhich originate primarily from masonry rubble (b) type IIaggregates which originate primarily from concrete rubbleand (c) type III aggregates which consist of a blend ofrecycled aggregates and natural aggregatesThe specificationsprovided the required properties of these types and theprovision for their use

In 2002 the Works Bureau of Hong Kong [14] issueda special standard WBCT 22002 on the use of RCAin concrete According to this specification (a) for lowergrade applications (a target design strength below 20MPa)concrete with 100 recycled coarse aggregate is allowed (b)recycled fines are not allowed to be used in concrete and(c) for higher grade applications (up to C35 concrete) it isallowed to use a maximum of 20 replacement of virgincoarse aggregates by recycled aggregates and the concretecan be used for general concrete applications except in waterretaining structures

Japan issued three standards for recycled aggregate forconcrete JIS A 5021 JIS A 5022 and JIS A 5023 for classesH M and L respectively [18] These classes can be used asfollows (a) class H in which no limitations are put on thetype and segment for concrete and structures with a nominalstrength of 45MPa or less (b) class M for concrete used formembers that are not subjected to frost action such as pilesunderground beam and concrete filled in steel tubes and (c)class L which can be used for backfill blinding and levelingconcretes

In addition to specification and standards some well-known committees and organizations such as ECCO [4]FHA [5] CCA [7] ACI 555R [8] PCA and [9] OSSGA [19]published previous experience and guidelines for the use ofRCA in concrete

3 Materials

The cement used in all mixes is ordinary Portland cementconforming to ASTM C 150-92 Type I specifications Naturalcoarse aggregate is crushed limestone from local sourcesGradation of the normal aggregates was obtained usingASTM C136 Natural coarse aggregate used in the mixes wasobtained by combining various aggregates of different single-sized aggregates in order to arrive at a grading acceptedby ASTM and BS standards The procedure described byMontgomery and Sturgiss [20] has been followed in thepreparation of RCA as follows first RCA was obtained bycrushing the previously tested samples in the laboratoryinto manageable lumps and then crushing these lumps ina Los Angeles abrasion machine These particles were thenwashed dried and sieved using the standard sieves for courseaggregates Any material passing sieve 5mm (ASTM 4) wasdiscarded Later the sieved particles were combined in order

Advances in Materials Science and Engineering 3

Table 1 Physical properties of aggregates

Property Coarseaggregate

Fineaggregate RCA

Specific gravity (SSD) 257(s = 0041)

259(s = 0037)

228(s = 0057)

Water absorption 167(s = 0052)

19(s = 0071)

58(s = 0121)

Rodded bulk density 1502 kgm3

(s = 112) mdash 1310 kgm3

(s = 143)LA abrasion () 25 mdash 31s standard deviation

to obtain a gradation similar to that of the natural aggregatesBy this the possible effect of the change of gradation on theproperties of concrete is minimized The graduation of bothnatural and RCA aggregates is within ASTM C33 and BS882 for grading requirements for coarse aggregate of nominalmaximum size 20mm (ASTM 15rdquo) to 5mm (ASTM number4) Natural sand known locally as desert sand is used in allmixes The fineness modulus of sand is 176 The sand is notwithin the ASTM C 33ndash92 standard limits but it is withinthe limits of BS 882 1992 standards and is classified as ldquoMrdquo(medium sand) Although this sand is relatively fine it hasgood properties and is commonly used in concrete mixes

The specific gravity and absorption of the aggregates weremeasured using ASTM C 127 and ASTM C 128 In each caserepresentative samples were taken and tested according tothe corresponding ASTM standard For natural aggregatethe average of three values was calculated Because of thehigher variability in RCA results the average of six values(taken fromdifferent crushed lots) was calculatedThe resultsare presented in Table 1 The hardness of the aggregates wasobtained using ASTMC 131The Los Angeles abrasion valuesof both aggregates are shown in the table The compacteddensity (dry-rodded unit weight) of the aggregates wasobtained using ASTM C 29

From Table 1 RCA aggregate has lower specific gravityand higher absorption The reduction in the density andspecific gravity and the increase in absorption are attributedto the attachment of cement paste in the recycled aggregate[3] Since the absorption is highly increased Tsujino etal [21] showed that using an oil-type surface improvingagent reduced water absorption of low- and middle-qualityrecycled aggregate resulting in an enhanced concrete perfor-mance

The RCA aggregate conformed to RILEM 1994 Type IIJIS A 5021 (Type M) and WBCT 22002 Type 2

4 Experimental Program

In order to study the effect of the use of RCA in concreteseveral concrete mixes have been prepared and tested in thelaboratory The following steps summarize the program thathas been followed

(1) Conventional concrete mixes of watercement ratioof 045 055 and 065 were designed and tested inthe laboratory All mixes were prepared and adjusted

Table 2 Mix proportions

Replacement ratio(by volume of CA)

CementKgm3

WaterKgm3

CoarseaggregateKgm3

FineaggregateKgm3

RCAKgm3

119908119888 = 065

0 303 197 985 775 025 303 197 740 775 21850 303 197 495 775 43675 303 197 245 775 654100 303 197 0 775 873

119908119888 = 055

0 358 197 985 740 025 358 197 740 740 21850 358 197 495 740 43675 358 197 245 740 654100 358 197 0 740 873

119908119888 = 045

0 438 197 985 675 025 438 197 740 675 21850 438 197 495 675 43675 438 197 245 675 654100 438 197 0 675 873

to obtain concrete of medium workability (slump 8to 12 cm) Guidance of the ACI 2111 was introducedin the preliminary design of these mixes Then themixture proportions were practically adjusted in thelaboratory

In order to keep the free water cement and sandcontents constant in all mixes a percent of the volumeof coarse aggregate was replaced by a predeterminedpercentage of RCA By this the assumption of theabsolute unit volumedescribed inACI 2111 will not beaffected The percentage of the coarse aggregate thatwas replaced by RCA was 25 50 75 and 100by volume Table 2 summarizes the mix proportions

(2) All mixes were tested for workability using the slumptest described in ASTM C 143

(3) The air content was measured in all mixes using thepressure method described in ASTM C 231

(4) Several cubes of 100mm (asymp4 inch) side length wereprepared and cured in the laboratory in a water bathunder a temperature of 20∘plusmn 2∘C (75∘plusmn 3∘F) andthen tested at the age of 28 days for compressivestrength The average of three values was recorded asthe strength of concrete

(5) Several standard prisms of 100 times 100 times 500mm (asymp4 times 4 times 20 inch) were prepared and cured in thelaboratory in a water bath under a temperature of20∘plusmn 2∘ (75∘plusmn 3∘F) and then tested at the age of 28days for flexural tensile strengthThe average of threevalueswas recorded as the tensile strength of concrete


(6) Concrete containing RCA mixes were prepared byreplacing a predetermined amount of the coarseaggregate by RCA while keeping all other variablesconstant The ratio of RCA used was 25 50 75 and100 percent by volume of coarse aggregate

(7) Concrete containing RCA cubes and prisms wereprepared and tested as in steps 4ndash6

5 Experimental Results

The measured properties of fresh concrete are shown inFigures 1 and 2 Figure 1 shows the relationship between thepercentage of the coarse aggregate replaced by RCA and thepercentage of the original slump for allmixesTheworkabilityof concrete reduces by the increase in the RCA content Thereduction is more significant in the lower wc ratios Figure 2shows the results of the air content for the various types ofmixes Generally the air content increased when RCA wasintroduced It has been observed that up to 25 replacementthe increase in air content is marginal and close to theexpected value of ACI 2111 for maximum size of aggregateof 20mm (1 inch) For the higher percentage replacementsthe air content was 15 to 2 times the expected value

Themeasured properties of hardened concrete are shownin Figures 3 4 and 5 Figure 3 shows the percentage reductionin the 28-day compressive strength when normal aggregate isreplaced by RCA The use of the RCA resulted in reductionof the compressive strength This reduction increases bythe increase in the percentage of RCA in the mix Similarresults are shown by Limbachiya et al [3] Figure 4 showsthe percentage reduction in the 28-day tensile strength whennormal aggregate is replaced by recycled aggregate The useof the RCA resulted in reduction of the tensile strength Thisreduction increases by the increase in the amount of RCAreplacing normal aggregate Also higher strength concretessuffered more strength reduction However the percentreduction in tensile strength was less than the reductionin compressive strength For example the use of 100replacement reduced the compressive strength of the mixesby 25 for wc ratio 045 while in the case of tensile strengththis value is 14 Figure 5 shows the relationship between theRCA percent replacement and the ratio of the modulus ofelasticity of RCA to that of the natural aggregate concrete It isclear from the results that themodulus of elasticity is reducedwhen recycled aggregates are incorporated

6 Discussion of Results

61 Workability The reduction in workability can beattributed to the increase in water demand which is difficultto predict [11 22 23] Similar to the results in Figure 1 Chenet al [24] found that the slump of recycled concrete is lowerthan that of normal concrete and that the tendency becomesmore significant at low watercement ratios Furthermorethey observed that the workability of recycled concrete canbe improved if the recycled aggregate is washed Yong andTeo [2] solved the problem of reduction in workability bysoaking aggregates in water and then using the aggregate in

0 1000

1

2

3

0 20 40 60 80 1000

20

40

60

80

100

Replacement ratio ()

Ratio

of s

lum

p to

orig

inal

val

ueSt

anda

rd d

evia

tion

wc ratio = 045

wc ratio = 055

wc ratio = 065

Figure 1 Relationship between the percentage of the coarse aggre-gate replaced by RCA and the percentage of the original slump

saturated surface dry condition Contrary to previous resultsLimbachiya et al [3] observed only a slight reduction inslump value with increasing RCA content in the mix but thisremained essentially within the accepted specified tolerancesof plusmn25mm (1 inch)

62 Air Content The increase in air content was attributed tothe degree of cleanliness of RCA According to Montgomeryand Strugiss [20] increasing the level of cleanliness of RCAin terms of the amount of mortar adhering to aggregateparticles has been found to reduce the air content andalso to improve the workability mass per unit volume andcompressive strength of concrete

As well known the increase in air content would lowerthe strength of concrete therefore the increase in air contentmight contribute partly to the loss in strength especially formixes containing more than 25 replacement

63 Strength of Concrete Thecompressive strength reductioncan be attributedmainly to the replacement of normal aggre-gate by a lower quality aggregate However according to Lim-bachiya et al and Corps of Engineers [25] approximately nochange in strength is expected for replacement values below30 From Figure 3 it can be also concluded that higherstrength concretes sufferedmore reduction in strength Chenet al [24] found that at lower watercement ratios thecompressive strength of recycled concrete is much lower thanthat of normal concrete but at higher watercement ratiosthe compressive strength of recycled concrete is similar tothat of normal concrete According to Park [11] this problem


0 1000

02

04

0 20 40 60 80 100Aggregate replacement ratio ()

Air

cont

ent (

)

0

05

1

15

2

25

3

35

4

45

Average values

Stan

dard

dev

iatio

n

wc = 045

wc = 055wc = 065

ACI 2111 expected value fornormal concrete mixes

Figure 2 Relationship between the percentage of the coarseaggregate replaced by RCA and air content in fresh concrete

0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

Ratio

of c

ompr

essiv

e stre

ngth

to

orig

inal

val

ue

wc ratio = 045

wc ratio = 055

wc ratio = 065

Figure 3 Relationship between the percentage of the coarse aggre-gate replaced by RCA and the reduction in the 28-day compressivestrength

0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

wc ratio = 045

wc ratio = 055

wc ratio = 065Ra

tio o

f ten

sile s

treng

th to

orig

inal

val

ue

Figure 4 Relationship between the percentage of the coarseaggregate replaced by RCA and the reduction in the 28-day tensilestrength

0 20 40 60 80 100Replacement ratio ()

60

70

80

90

100

Ratio

of m

odul

us o

f ela

stici

ty to

orig

inal

val

ue

95 confidence intervalwc ratio = 045

wc ratio = 055

wc ratio = 065

Best fit line (R2= 099)

Figure 5 Relationship between the percentage of the coarseaggregate replaced by RCA and the ratio of the modulus of elasticityto zero-replacement


can be compensated for by adding extra cement Unlike otherresults at a replacement ratio of 25 Tia et al [26] observedan increase in the 28-day compressive strength of the recycledaggregate concrete (5 to 11) when compared to the controlmix

The loss in tensile strength has been observed by severalresearchers [11 16 24 27] Unlike compressive strength thisproblem cannot be easily compensated for by adding extracement [11] On the contrary Corps of Engineers [25] statedthat no reduction in both compressive and tensile strengthsis expected when recycled aggregate is used especially if theratio of the replacement is below 30 Also Yong and Teo [2]reported that flexural tensile strength and the splitting tensilestrength of both RCA and normal concrete are approximatelyequal

Further analysis has been made in order to obtain thetensilecompressive ratioThe ratio of the tensilecompressivestrength for all replacement ratios is shown in Figure 6 It isclear that the tensilestrength ratio increases by the increasein replacement ratio Since high percentages are accompaniedby lower strength then the use of RCA can be advantageousif higher tensilecompressive ratio is required

64 Modulus of Elasticity The reduction in the modulus ofelasticity is attributed to the reduction in themodulus of elas-ticity of the recycled aggregate [28ndash30] In a comprehensivestudy on the use of recycled aggregate in concrete Schoppe[28] found that 9 of the references he used in his studyobserved that themodulus of elasticity of concretemade withrecycled aggregate is between 55 and 100 compared tothat of normal concrete Schoppe also observed a reductionbetween 0 and 20

Although most authors reported that the reduction inmodulus of elasticity increases by the increase in the replace-ment ratio Chen et al [24] observed a constant reductionin the modulus of elasticity (approximately about 25)irrespective of the replacement ratio Moreover Rahal [31]reported only a marginal 3 reduction in the modulus ofelasticity for concretes of strength between 25 and 30MPa

From Figure 5 it is observed that a linear relationshipexists between the replacement ratio and the reduction in themodulus of elasticity irrespective of the watercement ratioThis finding is consistent with Chen et al [24] that changingthe watercement ratio does not have a significant effect onthe modulus of elasticity values

Figure 7 was plotted in order to evaluate the possibility ofapplying international formulas for the relationship betweencompressive strength and modulus of elasticity For compar-ison the simplified ACI equation [119864 = 47radic1198911015840

119888

] GPa andthe BS 8110 equation [119864 = 91 3radic119865

119888119906] GPa are also plotted (in

the ACI equation the cylinder strength has been assumed tobe 080 times the cube strength) From the figure it is clearthat neither the ACI 318 nor the BS 8110 equations can beapplied for the prediction of themodulus of elasticity It is alsonoted that all the modulus of elasticity values of the concretecontaining recycled aggregate fall below the BS 8110 This isnot observed in the ACI 318 equation Considering the BS8110 equation as an upper bound and using Figure 7 a simple


Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065

Figure 6 Relationship between the percentage of the coarseaggregate replaced by RCA and tensilecompressive strength at 28days

mathematical model to predict the modulus of elasticity inthe form of

119864 = 119865 (1 minus 119862119877) (1)

can be used to predict the modulus of elasticity (E) R isthe replacement ratio ( of the volume of coarse aggregate)F is a function of concrete strength (F

119888119906) which represents

an upper bound for the values (ie E at R = 0) and C is aconstant

In the study a simple equation to predict the modulus ofelasticity based on BS equation and (1) can be formulated

119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)

where E is the modulus of elasticity in GPa F119888119906

is the cubestrength in MPa and R is the recycled aggregate to normalaggregate ratio

In order to test the applicability of (1) the measuredmodulus of elasticity is plotted against the percent errorin prediction when using (1) as shown in Figure 8 Fromthe figure it is observed that the error in prediction rangesbetween minus10 and +20 The error can be considered low(approximately within plusmn10) for the lower wc ratios (055and 045) Also it is observed that the lower the replacementratio the lower the error is The 95 confidence interval isalso shown in the plot The average error for all data points isabout +6 Therefore in this specific case a better estimatecan be obtained by multiplying the predicted value by 094


16 20 24 28 32 36 40 44Compressive strength (MPa)

Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065

Figure 7 Relationship between the 28-day compressive strengthand the modulus of elasticity

7 Conclusions

Based on the study presented in this paper it can be concludedthat the use of RCA as coarse aggregate is possible in normalconcrete mixes It is useful in reducing the environmentalproblems created by dumping these materials and also helpstomaintain sustainability of the environment by reducing thenew quarries needed for new concrete

The use of RCA as coarse aggregate in concrete mixeshas adversely affected the properties of fresh concrete Theworkability of concrete is severely reduced However as itis well known the use of plasticizers and superplasticizerswill be beneficial in enhancing the workability Regardingair content in fresh concrete the use of RCA has an adverseeffect on the air content in concrete especially for replacementratios exceeding 25 On the other hand approximately noeffect is observed at replacements up to 25 Above thisvalue it has been observed that the air content is increasedby a constant value approximately 2 for replacementsexceeding 50

The use of RCA as coarse aggregate in concrete mixeshas adversely affected the properties of hardened concreteA decrease in compressive and tensile strengths has beenobserved This decrease depends on the replacement ratioand the grade of concrete For the same replacement ratio thepercentage reduction in compressive strength is more thanthat in tensile strength when RCA is incorporated Howeversuch problem can be easily coped for by reducing wc ratiowhich will result in increase in strength and hence can copefor such problem

16 20 24 28 32 36Measured modulus of elasticity

0

10

20

30

40

Fit linesAverage of all points95 confidence interval around the average

Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065

Figure 8 Relationship between the measured modulus of elasticityand percentage error in prediction using (2)

The modulus of elasticity of concrete has been reducedwhen RCA is incorporated irrespective of the wc ratio orthe RCA replacement ratio All values are below the BS 8110equation Also both ACI 318 and BS 8110 equations for theprediction of the modulus of elasticity of concrete do notapply for concrete containing RCA Therefore an equationfor predicting the modulus of elasticity of RCA concrete hasbeen obtained It is important to emphasize that this equationis applicable only for the conditions of this studyHence thereis a need to find an adequate model to describe the modulusof elasticity for RCA concrete mixes before generalizing anyformula A model similar to the one in (1) is suggested

At the end it is important to note that because ofthe widespread use of RCA it is important to providespecifications and standards that control the use of RCA inconcrete Each country can arrive at its own specificationand standards The Japanese and RILEM specifications canbe bases for such issue

8 Further Research

It is important to conduct further research concerning theuse of RCA before applications Properties such as shrinkagedurability and fire endurance need to be extensively andcarefully studied

References

[1] S Marinkovic and I Ignjatovic ldquoRecycled aggregate concretefor structural usemdashan overview of technologies properties and


applicationsrdquo in Proceedings of the ACES Workshop InnovativeMaterials and Techniques in Concrete Construction Corfu Octo-ber 2010

[2] P C Yong and D C L Teo ldquoUtilization of recycled aggregateas coarse aggregate in concreterdquo UNIMAS E-Journal of CivilEngineering vol 1 no 1 pp 1ndash6 2009

[3] M Limbachiya A Koulouris J Roberts and A Fried ldquoPer-formance of recycled aggregate concreterdquo in Proceedings ofthe RILEM International Symposium on Environment-ConsciousMaterials and Systems for Sustainable Development pp 127ndash1362004

[4] ECCO Recycling Concrete and Masonry Information BulletinEV 22 Environmental Council of Concrete OrganizationsSkokie Ill USA 1999

[5] FHA Recycling Portland Cement Concrete DP 47-85 FederalHighway Administration Washington DC USA 1985

[6] K Anderson W Uhlmeyer and M Russell ldquoUse of recycledconcrete aggregate in PCCPrdquo Literature Search WA-RD 7261State Department of Transportation Washington DC USA2009

[7] CCA Australia Use of Recycled Aggregates in ConstructionCement Concrete amp Aggregates New South Wales Australia2008

[8] A C I Committee ldquoRemoval and reuse of hardened concreterdquoTech Rep ACI 555R-01 AmericanConcrete Institute Farming-ton Hills Mich USA

[9] PCA ldquoConcrete technologymdashconcrete design and produc-tionmdashmaterials recycled aggregatesrdquo 2008 httpwwwce-mentorgtechcct aggregates recycledasp

[10] Nelson and N G O Shing Chai High-Strength Structural Con-crete with Recycled Aggregates [PhD dissertation] University ofSouthern Queensland 2004

[11] S G Park ldquoRecycled concrete construction rubble as aggregatefor new concreterdquo Study Report 86 BRANZ 1999

[12] S BM Crusher andGMill ldquoRecycling concrete andmasonryrdquo2010 httpwwwminingequipmentsnetknowledge169html

[13] D N Parekh and C D Dr Modhera ldquoAssessment I recycledaggregate concreterdquo Journal of Engineering Research and Studiesvol 2 no 1 pp 1ndash9 2011

[14] W Fong J Yeung and C Poon ldquoHong Kong experience ofusing recycled aggregates from construction and demolitionmaterials in ready mix concreterdquo in Proceedings of the Inter-national Workshop on Sustainable Development and ConcreteTechnology pp 267ndash275 Beijing China 2004

[15] M Kawakami and Tokushige ldquoEnvironmentally consciousconcreterdquo in Proceedings of the Cement Based Materials amp CivilInfrastructure International Workshop (CBM-CI rsquo07) pp 155ndash163 Karachi Pakistan 2007

[16] H Qasrawi I Marie and H Tantawi ldquoThe use of concreterubbles as course aggregate in concreterdquo inProceedings of the 5thInternational Jordanian Civil Engineering Conference pp 281ndash287 Jordan Engineers Association Amman Jordan January2012

[17] RILEM ldquoSpecifications for concrete with Recycled AggregatesrdquoMaterials and Structures vol 27 pp 557ndash559 1994

[18] T Noguchi ldquoToward sustainable resource recycling in concretesocietyrdquo in Proceedings of the 2nd International Conference onSustainable Construction Materials and Technologies pp 321ndash334 Alcona Italy June 2010

[19] OSSGA The ABCs of Recycled Aggregate Ontario Stone Sandand Gravel Association 2010

[20] D G Montgomery and D Sturgiss ldquoProperties of concreteincorporating recycled concrete aggregatesrdquo in Proceedings ofthe National Symposium on the Use of Recycled Materials inEngineering Construction pp 153ndash156 Sydney Australia 1996

[21] MTsujino TNoguchiMTamuraMKanemats IMaruyamaand H Nagai ldquoStudy on the application of low-quality recycledcoarse aggregate to concrete structure by surface modificationtreatmentrdquo in Proceedings of the 2nd Asian Concrete FederationConference pp CMT36ndashCMT45 Bali Indonesia November2006

[22] A D Buck ldquoRecycled aggregate as a source of aggregaterdquo ACIJournal vol 74 no 5 pp 212ndash219 1977

[23] T C Hansen and H Narud ldquoStrength of recycled concretemade from crushed concrete coarse aggregaterdquo Concrete Inter-national vol 5 no 1 pp 79ndash83 1983

[24] H-J Chen T Yen andK-H Chen ldquoTheuse of building rubblesin concrete and mortarrdquo Journal of the Chinese Institute ofEngineers vol 26 no 2 pp 227ndash236 2003

[25] US Army Corps of Engineers ldquoReuse of concrete materialsfrom building demolitionrdquo Tech Rep 200 2004

[26] M Tia N Hossiney and P Bekoe ldquoModulus of elasticitycreep and shrinkage of concretemdashPhase IIImdashpart 2rdquo Tech RepDepartment of Civil and Coastal Engineering University ofFlorida Gainesville Fla USA

[27] R Kumutha and K Vijai ldquoStrength of concrete incorporatingaggregates recycled fromdemolitionwasterdquo Journal of Engineer-ing and Applied Sciences vol 5 no 5 pp 64ndash71 2010

[28] B Schoppe Shrinkage amp Modulus of Elasticity in Concretewith Recycled Aggregates [MS thesis] Faculty of CaliforniaPolytechnic State University 2011

[29] J Xiao J Li and C Zhang ldquoMechanical properties of recycledaggregate concrete under uniaxial loadingrdquo Cement and Con-crete Research vol 35 no 6 pp 1187ndash1194 2005

[30] M C Rao S K Bhattacharyya and S V Barai ldquoInfluenceof field recycled coarse aggregate on properties of concreterdquoMaterials and Structures vol 44 no 1 pp 205ndash220 2011

[31] K Rahal ldquoMechanical properties of concrete with recycledcoarse aggregaterdquo Building and Environment vol 42 no 1 pp407ndash415 2007

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Biomaterials


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TextilesHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Journal of

NanotechnologyHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Journal of

CrystallographyJournal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014


CoatingsJournal of

Advances in

Materials Science and EngineeringHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Smart Materials Research



MetallurgyJournal of


BioMed Research International

MaterialsJournal of


Nano

materials


Journal ofNanomaterials


basis (whatever is left over can be reused or reclaimed asaggregate) and old hardened concrete can be recycled andused as aggregate in new concrete or as fill and pavementbase materialrdquo Parekh and Modhera [13] considered the useof RCA in concrete as an appropriate and ldquogreenrdquo solution tothe anticipated increased world-wide construction activity

12 Economic Factors SBM [12] considered that recyclingconcrete is an attractive option for governmental agenciesand contractors alike because most municipalities imposetight environmental controls over opening of new aggregatesources or new dumping areas By time the increase of thecost of starting new quarries is increased and will be fartheraway Hence the cost and transport distances of conventionalaggregates could continue to increase as sources becomescarcer Since landfill space is limited and can be far awayespecially in urban areas the disposal of demolished rubblesbecomes costly and dumping fees will most likely rise asconstruction debris increases and the number of accessiblelandfills decreases Such situation was faced in Hong Kongand recycling aggregate was an attractive solution [14]

13 Solving the Problem of Lack of Materials According toKawakami and Tokshige [15] utilization of concrete that usesrecycled aggregates as a construction material is expected tocontribute to solving the issue of lack of raw materials andthus would allow the construction of infrastructures usinga circulatory system for resources Such situation was facedin Hong Kong and recycling aggregate was an attractivesolution [14]

14 Other Uses While unprocessed RCA is useful to beapplied as many types of general bulk fill bank protectionsubbasement road construction and embankments pro-cessed RCA can be applied to new concrete including leanand structural grade concrete soil-cement pavement basesand bituminous concrete [9] Moreover it has been used toproduce high strength concrete [10]

The use of RCA for the production of concrete involvesbreaking demolished concrete into materials with specifiedsize and quality These materials can then be combined toproduce aggregate of a predetermined grading and hencecan be used in concrete Moreover the steel reinforcementcan be recycled and then can be used as structural concretereinforcement reducing the effect on natural resources

In this research the authors investigate the use of RCAin normal concrete mixes and study the possible effects onsome of the concrete properties Also the research will tryto arrive at some unique relationships that can be used inthe prediction of the properties of RCA concrete Hence triesto help in providing specifications that can be applied toRCA and RCA concrete The research is a continuation of apreviously conducted research on the use of RCA in concrete[16]

2 Common Specifications

Because of the widespread use of RCA in concrete severalagencies have adapted special standards and specificationscovering the use of these materials in concrete In 1994RILEM [17] issued the ldquoSpecifications for concrete withRecycled aggregatesrdquo In these specifications the RCA isclassified into three main categories (a) type I aggregateswhich originate primarily from masonry rubble (b) type IIaggregates which originate primarily from concrete rubbleand (c) type III aggregates which consist of a blend ofrecycled aggregates and natural aggregatesThe specificationsprovided the required properties of these types and theprovision for their use

In 2002 the Works Bureau of Hong Kong [14] issueda special standard WBCT 22002 on the use of RCAin concrete According to this specification (a) for lowergrade applications (a target design strength below 20MPa)concrete with 100 recycled coarse aggregate is allowed (b)recycled fines are not allowed to be used in concrete and(c) for higher grade applications (up to C35 concrete) it isallowed to use a maximum of 20 replacement of virgincoarse aggregates by recycled aggregates and the concretecan be used for general concrete applications except in waterretaining structures

Japan issued three standards for recycled aggregate forconcrete JIS A 5021 JIS A 5022 and JIS A 5023 for classesH M and L respectively [18] These classes can be used asfollows (a) class H in which no limitations are put on thetype and segment for concrete and structures with a nominalstrength of 45MPa or less (b) class M for concrete used formembers that are not subjected to frost action such as pilesunderground beam and concrete filled in steel tubes and (c)class L which can be used for backfill blinding and levelingconcretes

In addition to specification and standards some well-known committees and organizations such as ECCO [4]FHA [5] CCA [7] ACI 555R [8] PCA and [9] OSSGA [19]published previous experience and guidelines for the use ofRCA in concrete

3 Materials

The cement used in all mixes is ordinary Portland cementconforming to ASTM C 150-92 Type I specifications Naturalcoarse aggregate is crushed limestone from local sourcesGradation of the normal aggregates was obtained usingASTM C136 Natural coarse aggregate used in the mixes wasobtained by combining various aggregates of different single-sized aggregates in order to arrive at a grading acceptedby ASTM and BS standards The procedure described byMontgomery and Sturgiss [20] has been followed in thepreparation of RCA as follows first RCA was obtained bycrushing the previously tested samples in the laboratoryinto manageable lumps and then crushing these lumps ina Los Angeles abrasion machine These particles were thenwashed dried and sieved using the standard sieves for courseaggregates Any material passing sieve 5mm (ASTM 4) wasdiscarded Later the sieved particles were combined in order




Fineaggregate RCA


259(s = 0037)

228(s = 0057)


19(s = 0071)

58(s = 0121)


(s = 112) mdash 1310 kgm3











CementKgm3

WaterKgm3

CoarseaggregateKgm3

FineaggregateKgm3

RCAKgm3

119908119888 = 065

0 303 197 985 775 025 303 197 740 775 21850 303 197 495 775 43675 303 197 245 775 654100 303 197 0 775 873

119908119888 = 055

0 358 197 985 740 025 358 197 740 740 21850 358 197 495 740 43675 358 197 245 740 654100 358 197 0 740 873

119908119888 = 045

0 438 197 985 675 025 438 197 740 675 21850 438 197 495 675 43675 438 197 245 675 654100 438 197 0 675 873















0 1000

1

2

3

0 20 40 60 80 1000

20

40

60

80

100


Ratio

of s

lum

p to

orig

inal

val

ueSt

anda

rd d

evia

tion

wc ratio = 045

wc ratio = 055

wc ratio = 065







0 1000

02

04


Air

cont

ent (

)

0

05

1

15

2

25

3

35

4

45

Average values

Stan

dard

dev

iatio

n

wc = 045

wc = 055wc = 065



0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

Ratio

of c

ompr

essiv

e stre

ngth

to

orig

inal

val

ue

wc ratio = 045

wc ratio = 055

wc ratio = 065


0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

wc ratio = 045

wc ratio = 055

wc ratio = 065Ra

tio o

f ten

sile s

treng

th to

orig

inal

val

ue



60

70

80

90

100

Ratio

of m

odul

us o

f ela

stici

ty to

orig

inal

val

ue


wc ratio = 055

wc ratio = 065











119888





Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065



119864 = 119865 (1 minus 119862119877) (1)





119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)






Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials






Fineaggregate RCA


259(s = 0037)

228(s = 0057)


19(s = 0071)

58(s = 0121)


(s = 112) mdash 1310 kgm3











CementKgm3

WaterKgm3

CoarseaggregateKgm3

FineaggregateKgm3

RCAKgm3

119908119888 = 065

0 303 197 985 775 025 303 197 740 775 21850 303 197 495 775 43675 303 197 245 775 654100 303 197 0 775 873

119908119888 = 055

0 358 197 985 740 025 358 197 740 740 21850 358 197 495 740 43675 358 197 245 740 654100 358 197 0 740 873

119908119888 = 045

0 438 197 985 675 025 438 197 740 675 21850 438 197 495 675 43675 438 197 245 675 654100 438 197 0 675 873















0 1000

1

2

3

0 20 40 60 80 1000

20

40

60

80

100


Ratio

of s

lum

p to

orig

inal

val

ueSt

anda

rd d

evia

tion

wc ratio = 045

wc ratio = 055

wc ratio = 065







0 1000

02

04


Air

cont

ent (

)

0

05

1

15

2

25

3

35

4

45

Average values

Stan

dard

dev

iatio

n

wc = 045

wc = 055wc = 065



0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

Ratio

of c

ompr

essiv

e stre

ngth

to

orig

inal

val

ue

wc ratio = 045

wc ratio = 055

wc ratio = 065


0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

wc ratio = 045

wc ratio = 055

wc ratio = 065Ra

tio o

f ten

sile s

treng

th to

orig

inal

val

ue



60

70

80

90

100

Ratio

of m

odul

us o

f ela

stici

ty to

orig

inal

val

ue


wc ratio = 055

wc ratio = 065











119888





Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065



119864 = 119865 (1 minus 119862119877) (1)





119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)






Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











0 1000

1

2

3

0 20 40 60 80 1000

20

40

60

80

100


Ratio

of s

lum

p to

orig

inal

val

ueSt

anda

rd d

evia

tion

wc ratio = 045

wc ratio = 055

wc ratio = 065







0 1000

02

04


Air

cont

ent (

)

0

05

1

15

2

25

3

35

4

45

Average values

Stan

dard

dev

iatio

n

wc = 045

wc = 055wc = 065



0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

Ratio

of c

ompr

essiv

e stre

ngth

to

orig

inal

val

ue

wc ratio = 045

wc ratio = 055

wc ratio = 065


0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

wc ratio = 045

wc ratio = 055

wc ratio = 065Ra

tio o

f ten

sile s

treng

th to

orig

inal

val

ue



60

70

80

90

100

Ratio

of m

odul

us o

f ela

stici

ty to

orig

inal

val

ue


wc ratio = 055

wc ratio = 065











119888





Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065



119864 = 119865 (1 minus 119862119877) (1)





119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)






Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0 1000

02

04


Air

cont

ent (

)

0

05

1

15

2

25

3

35

4

45

Average values

Stan

dard

dev

iatio

n

wc = 045

wc = 055wc = 065



0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

Ratio

of c

ompr

essiv

e stre

ngth

to

orig

inal

val

ue

wc ratio = 045

wc ratio = 055

wc ratio = 065


0 1000

1

2

3

0 20 40 60 80 10075

80

85

90

95

100


Stan

dard

dev

iatio

n

wc ratio = 045

wc ratio = 055

wc ratio = 065Ra

tio o

f ten

sile s

treng

th to

orig

inal

val

ue



60

70

80

90

100

Ratio

of m

odul

us o

f ela

stici

ty to

orig

inal

val

ue


wc ratio = 055

wc ratio = 065











119888





Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065



119864 = 119865 (1 minus 119862119877) (1)





119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)






Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials











119888





Ratio

of t

ensil

e stre

ngth

to co

mpr

essiv

e stre

ngth

12

14

16

18

20

wc ratio = 045

wc ratio = 055

wc ratio = 065



119864 = 119865 (1 minus 119862119877) (1)





119864 = 91 3radic119865119888119906(1 minus 0353119877) (2)






Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





Mod

ulus

of e

lasti

city

(MPa

)

10

20

30

40

ACI 318BS 8110

wc ratio = 045

wc ratio = 055

wc ratio = 065


7 Conclusions





0

10

20

30

40


Erro

r in

pred

ictio

n (

)

minus10

minus20

wc = 045

wc = 055

wc = 065




8 Further Research


References









































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










































CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



towards better understanding of concrete containing recycled concrete aggregate

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