Promoting the use of crumb rubber concrete in developing countries

Transcription

1 Available online at Waste Management 28 (8) 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, USA b Civil Engineering Department, Faculty of Engineering, The Hashemite University, Zarka 13115, Jordan Accepted 23 September 7 Available online 3 December 7 Abstract The use of accumulated waste materials in third world countries is still in its early phases. It will take courage for contractors and others in the construction industry to recycle selected types of waste materials in the concrete mixes. This paper addresses the recycling of rubber tires accumulated every year in Jordan to be used in concrete mixes. The main objectives of this research were to provide more scientific evidence to support the use of legislation or incentive-based schemes to promote the reuse of accumulated waste tires. This research 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 the mixture was the volumetric percentage of crumb tires used in the mix. The test results showed that even though the compressive strength is reduced when using the crumb tires, it can meet the strength requirements of light weight concrete. In addition, test results and observations indicated that the addition of crumb rubber to the mix has a limited effect toward reducing the workability of the mixtures. The mechanical test results demonstrated that the tested specimens of the crumb rubber concrete remained relatively intact after failure compared to the conventional concrete specimens. It is also concluded that modified concrete would contribute to the disposal of the nondecaying 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 industry in theses countries, serves two purposes. Ó 7 Elsevier Ltd. All rights reserved. 1. Introduction Hazardous waste materials are being generated and accumulated in vast quantities causing an increasing threat to the environment. Hazardous materials can be classified as chemical, toxic or non-decaying material accumulating with time. The accumulation of rubber and plastic can be considered non-decaying materials that disturb the surrounding environment. However, a positive method for disposing of this non-decaying material, such as reuse in concrete mixes, would have a beneficial effect. Recycling techniques are being developed around the world and many have proven to be effective in protecting our environment and conserving natural resources (Shayan and Xu, * Corresponding author. Tel.: ; fax: address: malekbat@hotmail.com (M.K. Batayneh). 1999; Rindl, 1998; Pierce and Blackwell, 3; Segre and Joekes, ). Recycling of materials such as, rubber, glass, demolished concrete, metal, and plastic represent a clear model for the proper disposal of waste materials for a better environment (Batayneh and Marie, 6; Shayan and Xu, 4; Marzouk et al., 7). It has been reported that the United States alone has about 275 million scrap tires stockpiled across the country, with an annual increase of 29 million tires generated per year (Papakonstantinou and Tobolski, 6). Research and development within the industrial world is continuously progressing towards finding new and innovative techniques to recycle waste materials. Worldwide, the use of recycled materials has been practiced for years in highway application and in rubberized concrete (Chanbane et al., 1999; Siddique and Naik, 4). The latter has gained acceptance worldwide in the engineering sector, directing X/$ - see front matter Ó 7 Elsevier Ltd. All rights reserved. doi:1.116/j.wasman

2 2172 M.K. Batayneh et al. / Waste Management 28 (8) many researchers in recent years to focus on performing additional research on the use of waste rubber in concrete (Hernandez-Olivares et al., 2; Siddique and Naik, 4; Lee and Roh, 6). The consumption of crumb rubber in highway construction was made compulsory in projects funded by governments like the USA and France (Marzouk et al., 7; Li et al., 4). Savas et al. (1996), Benazzouk and Queneudec (2), and Paine et al. (2) investigated the effect of adding rubber to concrete mixes on freezing and thawing resistance. They concluded that there is potential for using crumb rubber as a freeze thaw resistance agent in concrete and that the concrete with crumb rubber performed better under freeze thaw conditions than plain concrete. It has been reported by Hernandez-Olivares and Barluenga (4) that the addition of crumb tire rubber to structural high strength concrete slabs improved fire resistance, reducing the spalling damage by fire. Yang et al. (1) concluded in their research that rubberized concrete can successfully be used in secondary structural components such as culverts, crash barriers, sidewalks, running tracks, sound absorbers, etc. However, most of the developing third world countries have yet to raise their awareness regarding recycling of waste materials and have not developed effective legislation with respect to the 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 last decade to reach over 7, cars in 6. This quantity represents the number of cars registered officially as reported by the Ministry of Transport in Jordan (7). This amount of cars has lead to an increase in the rate of accumulation of scrap tires throughout the country. However, no current official data on the amount of stockpiled scrap tires in Jordan is available. Encouraging the local authorities to invest in and support the recycling of waste tires for use within building materials would provide an ideal and environmentally friendly disposal method for a large percentage of the waste tires. Due to rapid population growth in the recent years and influx of the refugees from neighboring countries, construction is booming and rapidly becoming the lead investment in the stock market. Therefore, the demand for building materials has risen accordingly to meet the high demand of the construction companies. Building on previous research carried out internationally, this study may provide the technical information necessary to improve local awareness of the reuse of crumb rubber as a substitute for natural aggregates in the production of concrete. One of the objectives of this paper is to make these data regarding the basic properties of modified concrete using crumb rubber in the concrete mix available to aid in the development of preliminary guidelines for the use of crumb rubber in concrete. This will eventually provide information for the effective use of waste tires in the concrete industry in Jordan. Furthermore, the reuse of the waste tires in construction will contribute to providing environmental-friendly solutions for the tire disposal problem in Jordan. In this study, a number of laboratory tests have been carried out on modified concrete specimens using crumb rubber obtained from waste tires. Different percentages of crumb rubber are used as a substitute for the natural fine aggregates used in the concrete mix. 2. Research program 2.1. Recycled scrap tires materials Four types of scrap tire particles have been classified by the study carried out by Siddique and Naik (4), which were graded according to particle size. These types consisted of slit tires (the tire is slit into two halves), shredded/chipped tires (the particle size is 3 mm long by 23 mm wide), ground rubber (19.15 mm), and crumb rubber ( mm). The crumb rubber has been reported to have a nominal size between 4.75 mm (No. 4 sieve) and.75 mm (No. sieve). The waste tire particles used in this study were crumb rubber, which was obtained from a local industrial unit in Jordan. The scrap tires originated from a scrap yard of tires from different types of vehicles (a combination of cars and trucks) in Jordan. The physical properties of the crumb rubber relevant for this study are particle shape and size. Fig. 1 shows the sieve analysis for both the crumb rubber particles and the fine aggregates (sand) used. The figure indicates that the gradation of the crumb rubber particles and the sand used fall between the minimum and maximum limits of the fine aggregates specified ACI gradation limits. The crumb rubber particle size varied from 4.75 to.15 mm. The crumb rubber was used in the concrete mix to partially substitute for fine aggregates (sand) in various percentages of %, %, %, %, and % Mixed materials The raw materials used for the preparation of the concrete mix consist of Type I Ordinary Portland Cement, nat- Cumulative % passing 1 Rubber Fine Agg Sieve size (mm) Fig. 1. Sieve analysis of crumb rubber.

3 M.K. Batayneh et al. / Waste Management 28 (8) ural fine aggregate which is specified as natural silica sand, and coarse aggregates taken from crushed limestone, all of which were supplied from natural local resources in Jordan. Tap water at room temperature was used in all mixes. For each crumb rubber percentage, three batches of concrete were prepared. Concrete with no additives was designated as the control mix. Various mix ratios of cement, water, fine, and coarse aggregates were used to achieve a workable concrete for a typical in situ concrete following ACI (ACI, 2) Specimen preparation and testing In order to prepare the recycled crumb rubber concrete specimens, fine aggregates were replaced by waste materials of crumb rubber in several percentages (%, %, %, %, and %) in separate concrete mixes. For each mix, cubes of mm, cylinders of 15 mm diameter by 3 mm height, and small beams of mm were prepared. All specimens were fabricated and then cured in water for 28 days in accordance with ASTM/C192M-6 Standard practice (ASTM, 6). For each concrete mix, slump tests were performed and recorded at the casting time of the specimens. A Universal Testing Machine with a maximum load capacity of 3 kn (load accuracy within ±.5%) was used for testing. After curing, specimens were tested for compressive strength, split tensile strength, and flexural strength in accordance with ASTM specified procedures. The compression tests were performed according to ASTM C39 Standard Test Method, and the indirect tensile (split tensile) strength tests were performed as described in ASTM C496 Standard Test Method. Flexural strength tests were performed according to 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 rubber content in the mix resulted in a decrease in both the slump and the unit weight of the mixtures. However, despite the decrease in measured slump, observation during mixing and casting showed that increasing the crumb content in the mix still produced a workable mix in comparison with the control mix. Despite the decrease in the unit weight of the mix (due to the lower unit weight of the rubber), the unit weight remained within the acceptable range for the total aggregate volume when up to % crumb rubber content was used. This statement is supported by the study carried out by Khatib and Bayomy (1999) Effect on strength The effect of crumb rubber on concrete strength is given in Table 2, and is demonstrated in Figs. 2 and 3. The relationships between the percentage of crumb rubber content and the reduction in compressive, tensile and flexural strengths are shown in Fig. 2. It can be seen that the use of crumb rubber reduced all types of tested strength. As expected, the higher the rubber content in the mix, the higher the reduction in compressive (f c ), tensile (f t )and flexural strengths. Detailed examination of the figure shows that increasing the crumb rubber to a limit of % concrete) Nominal Table 1 Mix proportions and fresh rubber concrete properties Crumb rubber Mix proportions (kg/m 3 of finished content (%) a Water Cement Coarse Fine aggregates Rubber w/c ratio aggregates Slump (mm) Unit weight (kg/m 3 ) a Percentage replacement by volume. Table 2 Effect of crumb rubber content on various strength results Crumb rubber content (%) Flexural strength (MPa) Splitting tensile strength, f t (MPa) Compressive strength, f c (MPa) f t /f c (exp.) f t =.3(f c ) 2/3 (MPa) f t /f c (theo.)

4 2174 M.K. Batayneh et al. / Waste Management 28 (8) Strength Reduction (%) Strength Reduction (%) Flexural Splitting tensile (ft) Compression (fc) Crumb Rubber Content (%) Fig. 2. Comparison between strength reduction and rubber content. 1 ft fc Linear (ft) Linear (fc) Compressive, R 2 =.9594 Tensile, R 2 =.9626 Crumb Rubber Content (%) Fig. 3. Effect of rubber content on the compressive and splitting tensile strengths. maintained a linear relationship between the increase of crumb rubber and the compressive strength, showing a loss of about 5% of the compressive strength at % rubber content. The inclination is lesser when rubber content is above %; however, rubber content between % and % continues to reduce the strength to a maximum loss of strength of up to 9%. Therefore, this result limits the use of the modified concrete when strength is the prime requirement. The relationship between compressive and splitting tensile strengths is demonstrated in Fig. 3, and the experimental and theoretical results are presented in Table 2. It can be seen from the figure that there is a linear correlation of the two strengths with both strengths showing the same linear rate of strength-loss with increasing rubber content. In addition, the ratio of splitting tensile to compressive strength (f t /f c, exp.) based on the experimental data is found to be similar to the ratio of the two strengths computed theoretically (f t /f c, theo.) using the theoretical equation (f t =.3(f c ) 2/3 ), as given in Table 2. Table 3 illustrates the required compressive strength for the different application categories of the structural light weight 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, concrete with crumb rubber can be classified as light weight concrete. This can also be supported by the conclusions reported by Pierce and Blackwell (3). The minimum strength required for structural light weight concrete is 17 MPa, as shown in Table 3. This strength can be met when % crumb rubber is used in the mix, achieving an Table 3 Practical range of categories of light weight concrete (Neville, 1995) Categories Density range (kg/m 3 ) Minimum strength (MPa) Structural light weight concrete Moderate strength concrete Low density concrete average strength of MPa. Therefore, the modified concrete containing up to % crumb rubber can be used in light weight structural elements. The second category given in Table 3, requiring compressive strength of 7 17 MPa for moderate concrete, can be also achieved with a % substitution of rubber for the fine aggregates of the mix. Fig. 4 shows the effect of the different percentages of rubber content on the retained compressive and splitting tensile strengths when compared to the control. The results indicate that the retained compressive strength for different rubber contents varied from 75% to 1% of the control specimen, while the retained tensile strength varied from 65% to 8% of the control specimen, as shown in Table 4. It is notable that the rate of strength reduction with increasing rubber content was nearly the same in compressive strength as it is in splitting tension strength. This is evident in the bar chart of Fig. 4, in which a trend-line for the bars has been drawn representing the two strengths of the bar chart. This gives approximately the same trend of inclination, unlike other studies that suggest that the rate of strength-loss in compression is higher than the rate of splitting in tension (Papakonstantinou and Tobolski, 6). Among other factors, concrete strength, particularly in compression, depends mainly on paste quality, aggregate paste bond, and aggregate hardness and density. Substituting the harder dense natural aggregates with a softer, less Control Strength Percent (%) Used for non-structural purposes (insulation panel, pavements, blocks, etc.) R2 =.9594 Splitting Tensile (ft) Compression (fc) Linear (Compression (fc)) Linear (Splitting Tensile (ft)) R2 =.9626 Crumb Rubber Content (%) Fig. 4. Variation of strengths with regards to control strength.

5 M.K. Batayneh et al. / Waste Management 28 (8) Table 4 Percentage retained strengths with relation to the control specimen Rubber content (%) Splitting tensile strength (f t ) (MPa) f t retained strength with relation to the control (%) Compressive strength (f c ) (MPa) f c retained strength with relation to the control (%) dense rubber will act as a stress concentrator, causing microcracking of the concrete matrix, leading to a loss in strength (Khatib and Bayomy, 1999; Li et al., 4) Stress strain relationship The relationship between stress and strain is shown in Fig. 5 for the different rubber contents in the concrete mix. Two different behavior patterns are shown for the stress strain curves. The stress strain behaviors of the specimens containing rubber of up to % behave in a similar trend to the control specimen, but having a smaller peak. From the figure, it can be observed that there is linear increase of stresses until it reaches its peak before energy is released by specimen s fracture. For this case, the specimens behaved like a brittle material of which the total energy generated upon fracture is elastic energy. However, nonlinear behavior is seen for the other two specimens containing % and % rubber. Here, once the peak stress is reached, the specimen continues to yield, as represented by the branch-line. This behavior is similar to the behavior of the tough materials having most of its energy generated upon fracture as plastic energy. Plastic energy is defined as the amount of energy required to produce a specified deformation after the elastic range, which increased the ability of the material to support loads even after the formation of cracks. Therefore, it can be stated that concrete with a higher percentage of crumb rubber possess high toughness, since the generated energy is mainly plastic. Stress ( kpa) % rubber Strain Fig. 5. Relationship between stress and strain for different rubber contents. % % % % 4. Conclusions The test results of this study indicate that there is great potential for the utilization of waste tires in concrete mixes in several percentages, including %, %, %, %, and %. Based on these results, the following can be concluded: The modified concrete mix using recycled tires performed satisfactorily on various tests, with acknowledgment to the proportional relationship between its rate of strength-loss and the content of the rubber in the mix. Mixing, casting and compacting the concrete mix using crumb rubber with local materials can be carried out in a similar fashion to that of the conventional concrete mix. Although the strength of modified concrete is reduced with an increase in the rubber content, its lower unit weight meets the criteria of light weight concrete that fulfill the strength requirements in Table 3. Although it is not recommended to use this modified concrete in structural elements where high strength is required, it can be used in many other construction elements like partition walls, road barriers, pavement, sidewalks, etc. which are in high demand in the construction industry. With the addition of the crumb rubber, the reduction in strength can not be avoided. However, these data provide a preliminary guideline of the strength-loss of locally produced modified concrete in comparison with the conventional concrete of 25 MPa targeted strength. The amount of scrap tires being accumulated in third world countries has created a big challenge for their disposal, thus obliging the authorities to invest in facilitating the use of waste tires in concrete as the use of concrete is fundamental to the booming construction industry in theses countries. Acknowledgements The authors would like to acknowledge the support of the Hashemite University of Jordan for funding this research study. The authors would like to thank Engineer Hussain El Diki for his technical assistance in the laboratory. References American Concrete Institute (ACI), 2. Standard practice for selecting proportions for normal, heavy weight and mass concrete, reproved 2, MI, USA.

6 2176 M.K. Batayneh et al. / Waste Management 28 (8) American Society for Testing and Materials (ASTM), 6. ASTM C192/ 192M-6 Standard practice for making and curing concrete test specimens in the laboratory, vol. 4.2, West Conshohocken, PA, USA. Batayneh, M., Marie, I., Asi, I., 6. Use of selected waste materials in concrete mixes. Waste Management Journal 27 (12), Benazzouk, A., Queneudec, M., 2. Durability of cement rubber composites under freeze thaw cycles. In: Dhir, R.K. et al. (Eds.), Proceedings of the International Conference on Sustainable Concrete Construction. University of Dundee, Scotland, UK, pp Chanbane, B., Sholar, G.A., Musselman, J.A., Page, G.C., Ten-year performance evaluation of asphalt-rubber surface mixes. Transportation Research Record No. 1681, Transportation Research, Washington, DC, pp Hernandez-Olivares, F., Barluenga, G., 4. Fire performance of recycled rubber-filled high-strength concrete. Elsevier Cent and Concrete Research 34 (1), Hernandez-Olivares, F., Barluenga, G., Bollati, M., Witozek, B., 2. Static and dynamic behaviour of recycled tyre rubber-filled concrete. Cement Concrete Research 32, Khatib, Z.R., Bayomy, F.M., Rubberized portland cement concrete. ASCE Journal of Materials in Civil Engineering 11 (3), Lee, H.J., Roh, H.S., 6. The use of recycled tire chips to minimize dynamic earth pressure during compaction of backfill. Construction Building Materials Journal. doi:1.116/j.conbuildmat Li, G., Stubblefield, M.A., Garrick, G., Eggers, J., Abadie, C., Huang, B., 4. Development of waste tire modified concrete. Cement Concrete Research 34, Marzouk, O.Y., Dheilly, R.M., Queneudec, M., 7. Valorization of post-consumer waste plastic in cementitious concrete composites. Waste Management 27, Ministry of Transport, 7. Public Transportation Authority Report, Amman, Jordan. Neville, A.M., Properties of Concrete. Addison Wesley Longman limited, England. Paine, K.A., Dhir, R.K., Moroney, R., Kopasakis, K., 2. Use of crumb rubber to achieve freeze thaw resisting concrete. In: Dhir, R.K. et al. (Eds.), Proceedings of the International Conference on Concrete for Extreme Conditions. University of Dundee, Scotland, UK, pp Papakonstantinou, C.G., Tobolski, M.J., 6. Use of waste tire steel beads in Portland cement concrete. Cement Concrete Research 36, Pierce, C.E., Blackwell, M.C., 3. Potential of scrap tire rubber as lightweight aggregate in flowable fill. Waste Management 23, Rindl, J., Recycling Manager, report by Recycling Manager, Dane County, Department of Public Works, Madison, USA. Savas, B.Z., Ahmad, S., Fedroff, D., Freeze thaw durability of concrete with ground waste tire rubber. Transportation Research Record No. 1574, Transportation Research Board, Washington, DC, pp. 88. Segre, N., Joekes, I.,. Use of tire rubber particles as addition to cement paste. Cement Concrete Research 3, Shayan, A, Xu, A., Utilization of glass as a pozzolonic material in concrete ARRB TR Internal Report RC Shayan, A., Xu, A., 4. Value-added utilization of waste glass in concrete. Cement Concrete Research 34 (1), Siddique, R., Naik, T.R., 4. Properties of concrete containing scraptire rubber an overview. Waste Management 24, Yang, S., Kjartanson, B., Lohnes, R., 1. Structural performance of scrap tire culverts. Canadian Journal of Civil Engineering 28 (2),