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Waste Management 28 (2008) 2171–2176

Promoting the use of crumb rubber concrete in developing countries

Malek K. Batayneh a,*, Iqbal Marie b, Ibrahim Asi b

a Fulbright Scholar at CFL, North Carolina State University, Campus Box 7533, Raleigh, NC 27695, USAb Civil Engineering Department, Faculty of Engineering, The Hashemite University, Zarka 13115, Jordan

Accepted 23 September 2007Available online 3 December 2007

Abstract

The use of accumulated waste materials in third world countries is still in its early phases. It will take courage for contractors andothers in the construction industry to recycle selected types of waste materials in the concrete mixes. This paper addresses the recyclingof rubber tires accumulated every year in Jordan to be used in concrete mixes. The main objectives of this research were to provide morescientific evidence to support the use of legislation or incentive-based schemes to promote the reuse of accumulated waste tires. Thisresearch focused on using crumb tires as a replacement for a percentage of the local fine aggregates used in the concrete mixes in Jordan.Different concrete specimens were prepared and tested in terms of uniaxial compression and splitting tension. The main variable in themixture was the volumetric percentage of crumb tires used in the mix. The test results showed that even though the compressive strengthis reduced when using the crumb tires, it can meet the strength requirements of light weight concrete. In addition, test results and obser-vations indicated that the addition of crumb rubber to the mix has a limited effect toward reducing the workability of the mixtures. Themechanical test results demonstrated that the tested specimens of the crumb rubber concrete remained relatively intact after failure com-pared to the conventional concrete specimens. It is also concluded that modified concrete would contribute to the disposal of the non-decaying scrap tires, since the amount being accumulated in third world countries is creating a challenge for proper disposal. Thus,obliging authorities to invest in facilitating the use of waste tires in concrete, a fundamental material to the booming construction indus-try in theses countries, serves two purposes.� 2007 Elsevier Ltd. All rights reserved.

1. Introduction

Hazardous waste materials are being generated andaccumulated in vast quantities causing an increasing threatto the environment. Hazardous materials can be classifiedas chemical, toxic or non-decaying material accumulatingwith time. The accumulation of rubber and plastic can beconsidered non-decaying materials that disturb the sur-rounding environment. However, a positive method fordisposing of this non-decaying material, such as reuse inconcrete mixes, would have a beneficial effect. Recyclingtechniques are being developed around the world andmany have proven to be effective in protecting our environ-ment and conserving natural resources (Shayan and Xu,

0956-053X/$ - see front matter � 2007 Elsevier Ltd. All rights reserved.

doi:10.1016/j.wasman.2007.09.035

* Corresponding author. Tel.: +1 919 5131733; fax: +1 919 5131765.E-mail address: malekbat@hotmail.com (M.K. Batayneh).

1999; Rindl, 1998; Pierce and Blackwell, 2003; Segre andJoekes, 2000). Recycling of materials such as, rubber, glass,demolished concrete, metal, and plastic represent a clearmodel for the proper disposal of waste materials for a bet-ter environment (Batayneh and Marie, 2006; Shayan andXu, 2004; Marzouk et al., 2007).

It has been reported that the United States alone hasabout 275 million scrap tires stockpiled across the country,with an annual increase of 290 million tires generated peryear (Papakonstantinou and Tobolski, 2006). Researchand development within the industrial world is continu-ously progressing towards finding new and innovative tech-niques to recycle waste materials. Worldwide, the use ofrecycled materials has been practiced for years in highwayapplication and in rubberized concrete (Chanbane et al.,1999; Siddique and Naik, 2004). The latter has gainedacceptance worldwide in the engineering sector, directing

0

20

40

60

80

100

120

9.5 4.75 2.36 1.18 0.6 0.3 0.15 0.075Sieve size (mm)

Cum

ulat

ive

% p

assi

ng

Rubber

Fine Agg

Fig. 1. Sieve analysis of crumb rubber.

2172 M.K. Batayneh et al. / Waste Management 28 (2008) 2171–2176

many researchers in recent years to focus on performingadditional research on the use of waste rubber in concrete(Hernandez-Olivares et al., 2002; Siddique and Naik, 2004;Lee and Roh, 2006). The consumption of crumb rubber inhighway construction was made compulsory in projectsfunded by governments like the USA and France (Mar-zouk et al., 2007; Li et al., 2004). Savas et al. (1996), Benaz-zouk and Queneudec (2002), and Paine et al. (2002)investigated the effect of adding rubber to concrete mixeson freezing and thawing resistance. They concluded thatthere is potential for using crumb rubber as a freeze–thawresistance agent in concrete and that the concrete withcrumb rubber performed better under freeze–thaw condi-tions than plain concrete. It has been reported by Hernan-dez-Olivares and Barluenga (2004) that the addition ofcrumb tire rubber to structural high strength concrete slabsimproved fire resistance, reducing the spalling damage byfire. Yang et al. (2001) concluded in their research that rub-berized concrete can successfully be used in secondarystructural components such as culverts, crash barriers, side-walks, running tracks, sound absorbers, etc. However,most of the developing third world countries have yet toraise their awareness regarding recycling of waste materialsand have not developed effective legislation with respect tothe local reuse of waste materials.

In Jordan, with a small population of just over 5 million,the number of cars has increased substantially in the lastdecade to reach over 700,000 cars in 2006. This quantityrepresents the number of cars registered officially asreported by the Ministry of Transport in Jordan (2007).This amount of cars has lead to an increase in the rate ofaccumulation of scrap tires throughout the country. How-ever, no current official data on the amount of stockpiledscrap tires in Jordan is available. Encouraging the localauthorities to invest in and support the recycling of wastetires for use within building materials would provide anideal and environmentally friendly disposal method for alarge percentage of the waste tires. Due to rapid populationgrowth in the recent years and influx of the refugees fromneighboring countries, construction is booming and rapidlybecoming the lead investment in the stock market. There-fore, the demand for building materials has risen accord-ingly to meet the high demand of the constructioncompanies. Building on previous research carried out inter-nationally, this study may provide the technical informa-tion necessary to improve local awareness of the reuse ofcrumb rubber as a substitute for natural aggregates in theproduction of concrete. One of the objectives of this paperis to make these data regarding the basic properties ofmodified concrete using crumb rubber in the concretemix available to aid in the development of preliminaryguidelines for the use of crumb rubber in concrete. This willeventually provide information for the effective use ofwaste tires in the concrete industry in Jordan. Further-more, the reuse of the waste tires in construction will con-tribute to providing environmental-friendly solutions forthe tire disposal problem in Jordan.

In this study, a number of laboratory tests have beencarried out on modified concrete specimens using crumbrubber obtained from waste tires. Different percentages ofcrumb rubber are used as a substitute for the natural fineaggregates used in the concrete mix.

2. Research program

2.1. Recycled scrap tires materials

Four types of scrap tire particles have been classifiedby the study carried out by Siddique and Naik (2004),which were graded according to particle size. These typesconsisted of slit tires (the tire is slit into two halves),shredded/chipped tires (the particle size is 300–400 mmlong by 100–230 mm wide), ground rubber (19–0.15 mm), and crumb rubber (4.75–0.075 mm). Thecrumb rubber has been reported to have a nominal sizebetween 4.75 mm (No. 4 sieve) and 0.075 mm (No. 200sieve). The waste tire particles used in this study werecrumb rubber, which was obtained from a local indus-trial unit in Jordan. The scrap tires originated from ascrap yard of tires from different types of vehicles (acombination of cars and trucks) in Jordan. The physicalproperties of the crumb rubber relevant for this study areparticle shape and size. Fig. 1 shows the sieve analysisfor both the crumb rubber particles and the fine aggre-gates (sand) used. The figure indicates that the gradationof the crumb rubber particles and the sand used fallbetween the minimum and maximum limits of the fineaggregates specified ACI gradation limits. The crumbrubber particle size varied from 4.75 to 0.15 mm. Thecrumb rubber was used in the concrete mix to partiallysubstitute for fine aggregates (sand) in various percent-ages of 20%, 40%, 60%, 80%, and 100%.

2.2. Mixed materials

The raw materials used for the preparation of the con-crete mix consist of Type I Ordinary Portland Cement, nat-

M.K. Batayneh et al. / Waste Management 28 (2008) 2171–2176 2173

ural fine aggregate which is specified as natural silica sand,and coarse aggregates taken from crushed limestone, all ofwhich were supplied from natural local resources in Jor-dan. Tap water at room temperature was used in all mixes.For each crumb rubber percentage, three batches of con-crete were prepared. Concrete with no additives was desig-nated as the control mix. Various mix ratios of cement,water, fine, and coarse aggregates were used to achieve aworkable concrete for a typical in situ concrete followingACI 211.1-91 (ACI, 2002).

2.3. Specimen preparation and testing

In order to prepare the recycled crumb rubber concretespecimens, fine aggregates were replaced by waste materialsof crumb rubber in several percentages (20%, 40%, 60%,80%, and 100%) in separate concrete mixes. For each mix,cubes of 100 · 100 · 100 mm, cylinders of 150 mm diameterby 300 mm height, and small beams of 100 · 100 · 400 mmwere prepared. All specimens were fabricated and then curedin water for 28 days in accordance with ASTM/C192M-06Standard practice (ASTM, 2006).

For each concrete mix, slump tests were performed andrecorded at the casting time of the specimens. A UniversalTesting Machine with a maximum load capacity of 300 kN(load accuracy within ±0.5%) was used for testing. Aftercuring, specimens were tested for compressive strength,split tensile strength, and flexural strength in accordancewith ASTM specified procedures. The compression testswere performed according to ASTM C39 Standard TestMethod, and the indirect tensile (split tensile) strength testswere performed as described in ASTM C496 Standard Test

Table 1Mix proportions and fresh rubber concrete properties

Crumb rubbercontent (%)a

Mix proportions (kg/m3 of finished concrete)

Water Cement Coarseaggregates

Fine agg

0 252 446 961 58520 252 446 961 46840 252 446 961 35160 252 446 961 23480 252 446 961 117.2100 252 446 961 0.0

a Percentage replacement by volume.

Table 2Effect of crumb rubber content on various strength results

Crumb rubbercontent (%)

Flexural strength(MPa)

Splitting tensile strength,ft (MPa)

0 3.68 2.82020 2.550 1.84040 2.040 1.47060 1.380 0.94080 0.770 0.533100 0.640 0.220

Method. Flexural strength tests were performed accordingto ASTM C78 Standard Test Method.

3. Results and discussion

3.1. Effect on workability and unit weight

As seen in Table 1, the increase of the crumb rubbercontent in the mix resulted in a decrease in both the slumpand the unit weight of the mixtures. However, despite thedecrease in measured slump, observation during mixingand casting showed that increasing the crumb content inthe mix still produced a workable mix in comparison withthe control mix. Despite the decrease in the unit weight ofthe mix (due to the lower unit weight of the rubber), theunit weight remained within the acceptable range for thetotal aggregate volume when up to 20% crumb rubber con-tent was used. This statement is supported by the study car-ried out by Khatib and Bayomy (1999).

3.2. Effect on strength

The effect of crumb rubber on concrete strength is givenin Table 2, and is demonstrated in Figs. 2 and 3. The rela-tionships between the percentage of crumb rubber contentand the reduction in compressive, tensile and flexuralstrengths are shown in Fig. 2. It can be seen that the useof crumb rubber reduced all types of tested strength. Asexpected, the higher the rubber content in the mix, thehigher the reduction in compressive (fc), tensile (ft) andflexural strengths. Detailed examination of the figureshows that increasing the crumb rubber to a limit of 40%

Nominalw/c ratio

Slump(mm)

Unit weight(kg/m3)regates Rubber

0.0 0.56 75.33 2399.067.51 0.56 60.7 2217.0

135.0 0.56 35.7 2068.3202.5 0.56 17.7 1987.0270.0 0.56 10.3 1830.6337.6 0.56 4.7 1740.6

Compressive strength,fc (MPa)

ft/fc

(exp.)ft = 0.3(fc)

2/3

(MPa)ft/fc

(theo.)

25.330 0.111 2.587 0.10218.960 0.097 2.133 0.11312.270 0.120 1.596 0.1308.070 0.116 1.207 0.1504.470 0.119 0.814 0.1822.500 0.088 0.553 0.221

0

20

40

60

80

100

0 20 40 60 80 100Crumb Rubber Content (%)

Stre

ngth

Red

uctio

n (%

)

FlexuralSplitting tensile (ft)Compression (fc)

Fig. 2. Comparison between strength reduction and rubber content.

Tensile, R2 = 0.9626

Compressive, R2 = 0.9594

0

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60

80

100

120

0 20 40 60 80 100

Crumb Rubber Content (%)

Stre

ngth

Red

uctio

n (%

)

ftfcLinear (ft)Linear (fc)

Fig. 3. Effect of rubber content on the compressive and splitting tensilestrengths.

R2 = 0.9594

R2 = 0.9626

0

20

40

60

80

100

120

0 20 40 60 80 100Crumb Rubber Content (%)

Con

trol

Str

engt

h Pe

rcen

t (%

) Splitting Tensile (ft)

Compression (fc)

Linear (Compression (fc))

Linear (Splitting Tensile (ft))

Fig. 4. Variation of strengths with regards to control strength.

Table 3Practical range of categories of light weight concrete (Neville, 1995)

Categories Densityrange(kg/m3)

Minimum strength (MPa)

Structural lightweightconcrete

1350–1900 17

Moderatestrengthconcrete

1900–800 7–17

Low densityconcrete

300–800 Used for non-structural purposes(insulation panel, pavements, blocks,etc.)

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maintained a linear relationship between the increase ofcrumb rubber and the compressive strength, showing a lossof about 50% of the compressive strength at 40% rubbercontent. The inclination is lesser when rubber content isabove 40%; however, rubber content between 40% and100% continues to reduce the strength to a maximum lossof strength of up to 90%. Therefore, this result limits theuse of the modified concrete when strength is the primerequirement. The relationship between compressive andsplitting tensile strengths is demonstrated in Fig. 3, andthe experimental and theoretical results are presented inTable 2. It can be seen from the figure that there is a linearcorrelation of the two strengths with both strengths show-ing the same linear rate of strength-loss with increasingrubber content. In addition, the ratio of splitting tensileto compressive strength (ft/fc, exp.) based on the experi-mental data is found to be similar to the ratio of the twostrengths computed theoretically (ft/fc, theo.) using the the-oretical equation (ft = 0.3(fc)

2/3), as given in Table 2.Table 3 illustrates the required compressive strength for

the different application categories of the structural lightweight concrete (LWC) as specified by Neville (1995),which has been adopted for building codes in Jordan.Because of the low specific gravity of the rubber, concretewith crumb rubber can be classified as light weight con-crete. This can also be supported by the conclusionsreported by Pierce and Blackwell (2003). The minimumstrength required for structural light weight concrete is17 MPa, as shown in Table 3. This strength can be metwhen 20% crumb rubber is used in the mix, achieving an

average strength of 18.97 MPa. Therefore, the modifiedconcrete containing up to 20% crumb rubber can be usedin light weight structural elements. The second categorygiven in Table 3, requiring compressive strength of 7–17 MPa for moderate concrete, can be also achieved witha 40–60% substitution of rubber for the fine aggregates ofthe mix.

Fig. 4 shows the effect of the different percentages ofrubber content on the retained compressive and splittingtensile strengths when compared to the control. The resultsindicate that the retained compressive strength for differentrubber contents varied from 75% to 10% of the controlspecimen, while the retained tensile strength varied from65% to 8% of the control specimen, as shown in Table 4.It is notable that the rate of strength reduction withincreasing rubber content was nearly the same in compres-sive strength as it is in splitting tension strength. This is evi-dent in the bar chart of Fig. 4, in which a trend-line for thebars has been drawn representing the two strengths of thebar chart. This gives approximately the same trend of incli-nation, unlike other studies that suggest that the rate ofstrength-loss in compression is higher than the rate of split-ting in tension (Papakonstantinou and Tobolski, 2006).Among other factors, concrete strength, particularly incompression, depends mainly on paste quality, aggregatepaste bond, and aggregate hardness and density. Substitut-ing the harder dense natural aggregates with a softer, less

Table 4Percentage retained strengths with relation to the control specimen

Rubber content(%)

Splitting tensile strength(ft) (MPa)

ft retained strength with relationto the control (%)

Compressive strength(fc) (MPa)

fc retained strength with relationto the control (%)

0 2.820 100 25.330 10020 1.840 65.25 18.960 74.8940 1.470 52.13 12.270 48.4460 0.940 33.33 8.070 31.8680 0.533 18.79 4.470 13.70100 0.220 8.16 2.500 9.99

M.K. Batayneh et al. / Waste Management 28 (2008) 2171–2176 2175

dense rubber will act as a stress concentrator, causingmicrocracking of the concrete matrix, leading to a loss instrength (Khatib and Bayomy, 1999; Li et al., 2004).

3.3. Stress–strain relationship

The relationship between stress and strain is shown inFig. 5 for the different rubber contents in the concretemix. Two different behavior patterns are shown for thestress–strain curves. The stress–strain behaviors of thespecimens containing rubber of up to 40% behave in a sim-ilar trend to the control specimen, but having a smallerpeak. From the figure, it can be observed that there is linearincrease of stresses until it reaches its peak before energy isreleased by specimen’s fracture. For this case, the speci-mens behaved like a brittle material of which the totalenergy generated upon fracture is elastic energy. However,nonlinear behavior is seen for the other two specimens con-taining 60% and 80% rubber. Here, once the peak stress isreached, the specimen continues to yield, as represented bythe branch-line. This behavior is similar to the behavior ofthe tough materials having most of its energy generatedupon fracture as plastic energy. Plastic energy is definedas the amount of energy required to produce a specifieddeformation after the elastic range, which increased theability of the material to support loads even after the for-mation of cracks. Therefore, it can be stated that concretewith a higher percentage of crumb rubber possess hightoughness, since the generated energy is mainly plastic.

0

5000

10000

15000

20000

25000

30000

0 0.0005 0.001 0.0015 0.002 0.0025 0.003 0.0035Strain

Stre

ss (

kPa) 0% rubber

20%

40%

60%

80%

Fig. 5. Relationship between stress and strain for different rubbercontents.

4. Conclusions

The test results of this study indicate that there is greatpotential for the utilization of waste tires in concrete mixesin several percentages, including 20%, 40%, 60%, 80%, and100%. Based on these results, the following can beconcluded:

The modified concrete mix using recycled tires per-formed satisfactorily on various tests, with acknowledg-ment to the proportional relationship between its rate ofstrength-loss and the content of the rubber in the mix. Mix-ing, casting and compacting the concrete mix using crumbrubber with local materials can be carried out in a similarfashion to that of the conventional concrete mix.

Although the strength of modified concrete is reducedwith an increase in the rubber content, its lower unit weightmeets the criteria of light weight concrete that fulfill thestrength requirements in Table 3. Although it is not recom-mended to use this modified concrete in structural elementswhere high strength is required, it can be used in manyother construction elements like partition walls, road barri-ers, pavement, sidewalks, etc. which are in high demand inthe construction industry.

With the addition of the crumb rubber, the reduction instrength can not be avoided. However, these data provide apreliminary guideline of the strength-loss of locally pro-duced modified concrete in comparison with the conven-tional concrete of 25 MPa targeted strength.

The amount of scrap tires being accumulated in thirdworld countries has created a big challenge for their disposal,thus obliging the authorities to invest in facilitating the use ofwaste tires in concrete as the use of concrete is fundamentalto the booming construction industry in theses countries.

Acknowledgements

The authors would like to acknowledge the support of theHashemite University of Jordan for funding this researchstudy. The authors would like to thank Engineer HussainEl Diki for his technical assistance in the laboratory.

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