Effect of using ground waste tire rubber as fine aggregate on the behaviour of concrete mixes

Transcription

1 Indian Journal of Engineering & Materials Sciences Vol. 14, December 2007, pp Effect of using ground waste tire rubber as fine aggregate on the behaviour of concrete mixes M M Balaha, A A M Badawy & M Hashish Engineering Materials Department, Faculty of Engineering, Zagazig University, Egypt Received 14 May 2000; accepted 5 December 2007 The development of environmentally accepted methods of used tire disposal is one of the greatest challenges that waste management experts face today. Using of wastes and by-products as concrete aggregate has attained great potential in the last few years. The aim of this work is to investigate the possibility of the usage of ground waste tire rubber (GWTR) in the civil construction as a partial replacement for fine aggregates and the influence of these wastes on the properties of ordinary concrete. The cement content for concrete mixes is 300, 400, and 500 kg/m 3. The total fine aggregate (TFA) in all mixes is sand, which is partially replaced by GWTR particles. The percentages by volume of GWTR/TFA are 5%, 10%, 15% and 20%. The physical and mechanical properties of rubberized concrete are compared with those of ordinary concrete mixes. Also, three treated materials, polyvinyl acetate, silica fume and sodium hydroxide (PVA, SF and NaOH) are used for treatment the ground waste tire rubber to improve the interface friction between rubber particles and cement matrix. The results show that the mass density (bulk density) of hardened rubberized concrete decreases with increasing rubber content, this is an advantage for that concrete application. Also concrete specimens containing rubber particles are much tougher than those without rubber particles. The damping ratio of the rubberized concrete containing 20% rubber is much higher than those of normal concrete by about 63.2%. Rubberized concrete incorporating treated rubber particles gives better results than concrete incorporating normal rubber. Used tires pose both a serious public health and an environmental threat. Therefore, economically feasible alternatives for scrap tire disposal must be found. Some of the current uses of scrap tires are tirederived fuel, barrier reefs, and crumb rubber as an asphalt additive. However, all of the recycling, re-use and recovery practices combined only consume about 22% of the discarded tires. Thus, a need still exists for the development of additional uses for scrap tires 1-3. Nowadays, waste tire disposal is a significant problem and finding an environment friendly and potentially attractive method is the greatest challenge. The difficulty in the recycling of the waste tire is that the tire rubber is a cross linked polymer that is hard to melt and to process 4,5. The ever-increasing volume of rubber waste in landfills from the disposal of used tires has grown into a serious environmental problem. Because rubber waste does not biodegrade readily, even after long periods of landfill treatment, there is renewed interest in developing alternatives to its disposal 6-8. Waste tire disposal is a worldwide problem and has caused worry for public administrators, researchers and environmentalists. The United States used the tires as asphalt mixtures for highways as an alternative to landfill disposal; however, there were many technical problems and resistance from industry groups. The workability, mechanical properties, and chemical stability of a recycled tire rubber-filled cementitious composite were evaluated 6. As expected, the geometry of the rubber particles influenced the fracture behaviour of mortar containing rubber. The addition of rubber led to a decrease in flexural strength and plastic shrinkage cracking of mortar. The rubber shreds bridged the cracks and provided restraint to crack widening 9,10. Due to its low specific gravity, crumb rubber can be considered a lightweight aggregate. The possibility of making concrete tough has been generally pursued by introduced rubber phases among the traditional components (cement, water and aggregates) and this idea has been largely investigated using, for this purpose, recycled grinded tire rubbers Different kinds of tires have been employed as partial substitute of natural aggregates in concrete: scrap tires obtained by simple grinding without further purifications thus including steel and textile fibers in their composition 11,13, crumb rubber obtained by cryogenic process 11, milled tire rubbers treated with sodium hydroxide solution to achieve a

2 428 INDIAN J. ENG. MATER. SCI., DECEMBER 2007 better adhesion with the cement paste 16, scrap truck tire rubber 14 and tires tread 12. However, regardless the different nature, size and composition of used tire rubbers, a meaningful decrease in concrete compressive strength with the increasing amount of rubber phase in the mixture were always detected. Although, so far obtained rubberized concrete generally shows a tougher behaviour with a gradual failure of the samples than traditional concrete, it generally does not exhibit suitable compressive strength for structural applications. Utilization of waste tires would eliminate castle pollution that is required to prevent degradation of air, land and water in the vicinity of the waste disposal sites. Also burning the remains tires rubber for getting rid of them causes a very big pollution to the environment. Therefore, many studies were directed to avoid the problems due to burn the remains tires rubber and studying the role of utilization the ground waste tires rubber as aggregates in concrete. Many properties of the concrete can be improved being used the tire chips in civil engineering applications such as low material density, high bulk permeability, high thermal insulation, high durability, and high bulk compressibility. Many researches have shown that both compressive strength and unit weight decreases with increasing rubber content The incorporation of fly ash in concreterubber mixtures further reduces unit weight 21. Increasing rubber content also reduces modulus of elasticity and improves ductility 22,23. In many cases, scrap tire chips may also represent the least expensive alternative to other fill materials. In the present investigation ground waste tires rubber was used as a partial replacement for fine aggregates by volume (0%, 5%, 10%, 15% and 20%). The cement content for concrete mixes was 300, 400, and 500 kg/m 3. Also, three treated materials (PVA, S.F. and NaOH) were used for treatment the ground waste tire rubber. Materials and Experimental Program Tire composition and characteristics The average scrap automobile tire weighs approximately 9 kg. Heavy truck and industrial tires can weigh from 16 to 46 kg approximately. Since 1983, all new car and light truck tires are steel-belted radials. 85% of all scrap tires are passenger car or light truck tires, 14% are heavy truck tires and the remaining 1% is specialty tires, ranging from aircraft tires to construction equipment tires 24. A typical tire casing is composed of 83% carbon, 7% hydrogen, 1.2% sulfur and 6% ash. Primary constituents of tires include polymers, carbon black and softeners. The softeners are mostly composed of hydrocarbon oils, which in combination with the polymers give the tire a very high heating value 24. Materials and method All materials used in this study were locally available materials. The cement used was type I ordinary Portland cement 25. The used sand was siliceous sand with 100% passing ASTM sieve No. 4 with a fineness modulus of Dolomite with 20 mm maximum nominal size was used as coarse aggregate. The specific gravity of the coarse aggregate and sand were 2.66 and 2.56, and their absorption percentages were 1.9 and 1% respectively 26. The waste rubber used in this research was the truck tire rubber which mill by different sizes < 4 mm after the exclusion of the part containing steel and textile fibers in their composition. The ground processes were obtained mechanically by using Al- Nasser Company for rubber product. Sieve analysis process was carried out on the GWTR and the result represented by the grading curve is illustrated in Fig.1. The physical properties of the used fine GWTR are given in Table 1. The coarse aggregate were washed carefully and dried before mixing to remove any impurities and organic matters, which may weaken its bond with the cement paste. Mixing water was clean tap water free from impurities and organic matters. Different cement contents of 300, 400 and 500 kg/m 3 were studied. The total fine aggregates in all mixes were sand partially replaced by fine GWTR particles. The percentages by volume of GWTR/TFA% by ratio were 0, 5%, 10%, 15% and 20% as given in Table 2. The experimental program included the investigation of the effect of Fig. 1 Grading curve of ground waste tire rubber

3 BALAHA et al.: RUBBERIZED CONCRETE 429 GWTR/TFA% by ratio on the compressive, tensile strengths, toughness and damping ratios of concrete. Treated materials Generally, the bond between rubber particles and constituent of concrete can enhance by increasing electrostatic interaction and facilitating chemical bonding. In this work, three treated materials were used for treatment the ground waste tire rubber to improve the interface interaction between rubber particles and cement matrix. Several surface treatments include NaOH, SF and PVA were used in this research. The strength and toughness of the concrete are enhanced by surface treatment of the GWTR using sized agents (treated materials). Table 1 Physical properties of ground waste tire rubber Property Measured value Specific gravity 0.9 Unit weight, g/cm³ 0.67 Absorption, % 1.9 Fineness modulus 3.81 Four mixes were performed with total cement content of 400 kg/m 3, as shown in Table 3. The first mix (C400) is the control mix. The second mix (R420N) was prepared using NaOH solution with concentration 10% was used to treat the GWTR. Putting the GWTR into a ceramic container, which contained the solution of NaOH for half an hour, performed the treatment process. After the immersion process, the material was washed until that its ph was 7 before it is mixed with Portland cement. The third mix (R420S) was prepared by using 15% silica fume replacement of Portland cement by weight. The last mixture was prepared by treatment the surface of ground waste tire rubber by PVA for 15 min before it mixed with cement. In all types of mixes, the TFA were sand, which was partially replaced with 20% ground waste tire rubber particles by volume. Experimental procedures A total number of 108 compression and indirect tensile test specimens were cast. Cubes mm were used for casting the concrete compression test specimens. Cylinders 150 mm Table 2 Mix proportion of rubberized concrete Mix code Cement content kg\m³ GWTR/TFA (%) W/C Water content lit/m³ Fine aggregate, kg/m³ Coarse aggregate, kg/m³ Sand Tire-rubber Dolomite C R R R R C R R R R C R R R R Table 3 Layouts of treated and untreated rubber concrete specimens Mix code Cement content kg/m³ Coarse aggregate (dolomite) (%) Fine aggregate Sand GWTR (%) (%) Type of sized No. of specimens agents Cube Cylinder C Control 3 3 R420N (NaOH) R420S Silica Fume 3 3 R420P PVA 3 3

4 430 INDIAN J. ENG. MATER. SCI., DECEMBER 2007 diameter and 300 mm height were used for casting the splitting tensile test specimens. For each concrete mix, three cubes and three cylinders were cast. The GWTR particles is added to the used cement and mixed well with it before mixing the concrete components. Dry materials were mixed first in the dry state for a time to insure the homogeneity of the mixture before adding the mixing water. Mechanical vibrator was used for compaction. Test specimens were removed from moulds in the second day of casting. The compression and tensile test specimens were cured under tap water for 28 days at room ambient temperature. A compression-testing machine of 3000 kn maximum capacity was used for the completion of both the compression and indirect tension test for concrete. Results and Discussion Properties of fresh concrete Physical properties included unit weight and consistency of fresh concretes (control and rubberized concretes) are measured and compared. The unit weight was calculated as summation of the weights of the different mixes constituents per cubic meter. It was noticed that the unit weights of concrete mixes containing rubber decreases with increasing of the percentages of GWTR contents when compared with the control mixes as shown in Fig. 2. The figure shows that a reduction in the unit weights reached 4.2% of normal concrete when rubber aggregate replaced sand. This reduction is attributed to the lower unit weight of rubber compared to sand and a lower volume of sand in the concrete mix compared to the coarse aggregate. It also noticed that the increasing of cement content increases the unit weight of these mixes. Consistency of different mixes was determined using the standard slump test and the results are given in Fig. 3. It was observed that the degree of consistency improved as the GWTR/TFA% by ratio increased. The maximum improvement was recorded at GWTR/TFA% by ratio equal to 15% and 20%. The addition of rubber raises the measured slump of the fresh rubberized concrete in rang of mm and the workability of rubberized concrete was not adversely affected. Figure 4 represents the slump values of the treated rubberized concrete mixes, which showed that the degree of consistency improved for three sized agents. The maximum improvement was recorded for PVA and SF mixes, but NaOH recorded lowest improvement for Fig. 2 Unit weight of different rubberized concrete Fig. 3 Slump values of different rubberized concrete Fig. 4 Effect of treated materials on slump values

5 BALAHA et al.: RUBBERIZED CONCRETE 431 workability. This behaviour can be attributed to that the NaOH permit to form empty places in the rubber particle surface, so it became rough. Properties of hard concrete Effect of cement content The effect of cement content of 300, 400 and 500 kg/m³ on the compressive strength of rubberized concrete at different GWTR/TFA% by ratio was shown in Fig. 5. Generally, this figure demonstrates that the compressive strength of concretes is increased with increasing cement content for all different values of GWTR/TFA% by ratio. It is clear that the increasing values of cement content (500 kg/m³) have pronounced effect on the increasing of compressive strength of rubberized concrete. For example, the increase in the compressive strength of the mix containing 20% of GWTR/TFA was 45% when cement content increased from 300 to 400 kg/m 3 and reached 60.3% when cement content increased from 400 to 500 kg/m 3. The tensile strength as a function of cement contents showed also similar trend for the compressive strength of concretes as shown in Fig. 6. The behaviour of either the compressive strength or the tensile strength with increasing cement content was expected because, as the hydration proceeds, the amount of hydration products increases and their accumulation closes the available pore volumes, which leads to a decrease in the total porosity and increase the compressive and tensile strengths. Also the strength development depends primarily on the formation of calcium silicate hydrate (CSH) as the main hydration products. Therefore, the formations of CSH phases with high values of cement content will increase and the strength accordingly increases 27. Effect of GWTR/TFA percentage The relative compressive strength ratios (σ c /σ co ) of rubberized concrete are shown in Fig. 7 for different cement contents of 300, 400 and 500 kg/m³ and different values of GWTR/TFA% by ratio. The relative compressive strength ratio is the ratio between compressive strength of concrete with partial sand replacement by GWTR by volume percents (rubberized concrete) (σ c ) to that of 100% sand as fine aggregates (σ co ). The results presented in Fig. 7 showed a reduction in compressive strength with increasing rubber content for the concrete mixes. For example, the relative compressive strength ratios (σ c /σ co ) at 300 kg/m³ cement content mixes were decreased about 0.92, 0.865, and 0.72 for Fig. 5 Compressive strength for different cement content Fig. 6 Tensile Strength for Different Cement Content Fig. 7 Relative compressive strength of rubberized concrete

6 432 INDIAN J. ENG. MATER. SCI., DECEMBER 2007 increasing GWTR/TFA% by ratio 5%, 10%, 15% and 20% respectively. This behaviour may be attributed to several reasons including; first, the rubber particles are softer than the surrounding cement paste and the weakness of the rubber material to withstand the load because of its low compressive strength. It also may consider that the spherical shapes of GWTR in the concrete are converted to elliptic shapes under compression, which cause tension cracks in the cement paste. The last reason is a presence lower bond between the rubber particles and the cement paste, this lower bond separates the rubber particles from the cement paste with increasing the load. Also the relative tensile strength ratios (σ t /σ to ) of rubberized concrete are shown in Fig. 8 for different cement contents 300, 400 and 500 kg/m³. This figure showed that the (σ t /σ to ) ratios decreases about 0.945, 0.89, 0.85 and 0.82 for GWTR/TFA% by ratio equal to 5%, 10%, 15% and 20% respectively. These values were recorded at cement content equal to 300 kg/m³. The present results show a reduction in the tensile strength with increasing rubber content of the concrete mixes. On the other hand, the mass density (bulk density) of hardened rubberized concrete decreases with increasing rubber content. This is an advantage for that concrete application where it reduce dead loads and hence reducing the concrete dimensions, however the strength of rubberized concrete decrease. Figure 9 gives the relationship between the ratios of compressive strength to hardened unit weight or (mass density) of rubberized concrete (σ c /γ) and GWTR/TFA% by ratio at different cement mixes. In general, the results show that the ratios of (σ c /γ) for rubberized concrete decreased with increasing rubber percent for all different cement contents. At 300 kg/m³ cement content mixes, the compressive strength to mass density (σ c /γ) were decreased about 6.8%, 11.2%, 20% and 24.2% for the rubber percents equal to 5%, 10%, 15% and 20% respectively. Figure 10 shows the applied load-displacement curve for splitting tensile test of normal concrete specimens, C400, (GWTR/TFA=0%) and rubberized concrete specimens, R420, (GWTR/TFA=20%). The figure shows that the normal concrete specimens failed faster than the rubberized concrete specimens. This implies that the concrete specimens containing rubber particles are much tougher than concrete specimens without rubber particles. The damping Fig. 8 Relative tensile strength of rubberized concrete Fig. 9 σ c /γ Ratios of rubberized concrete Fig. 10 Load displacement of concrete with and without rubber

7 BALAHA et al.: RUBBERIZED CONCRETE 433 capacity of the materials was used to measure the ability of the material to decrease the amplitude of free vibrations on its body. Figure 11 shows the measured vibration signal of the normal concrete specimen. The damping ratios from impulse response (ξ) values were ranged from to 0.035, with an average value of Also Fig. 12 shows that the damping ratios of the rubberized concrete specimen containing 20% ground waste tire rubber were ranged from to with an average value of By the comparison between two figures, it s clearly that the vibration amplitude of rubberized concrete specimen less than vibration amplitude of normal concrete specimen. This means that the damping ratios of the rubberized concrete containing 20% rubber was much higher than those of normal concrete by about 63.2%. Treated rubber In this study the GWTR particles were treated by using three sized agents, (PVA, SF and NaOH) before using it in concrete mixes. Figure 13 illustrates the compressive strength of rubberized concrete incorporating various treated rubber particles. This figure shows that the compressive strengths at 28 days were 444, 438 and 426 kg/cm² for treated rubber particles with PVA, SF and NaOH respectively. This means that the reduction in the compressive strength in case of treated rubber was 14%, 15% and 17% of the normal concrete specimens. On the other hand, in case of untreated rubber (normal rubber), the reduction was 27% at the same percent of rubber (GWTR/TFA=20%). It is obviously clear that rubberized concrete incorporating treated rubber particles give good results than concrete incorporating normal rubber. This behaviour may be explained as follow; PVA coated the rubber particles hence gives a good adhesive between rubber particles surface and cement paste further more its good water resistance. Also this behaviour was observed for silica fume because it's filling effect due to its finer particle size, thus providing a good adhesion between the rubber particles and the cement paste as well as increasing the density of the cement paste, which in turn significantly enhances the compressive strength of the rubberized concrete. The same behaviour of compressive strength was observed in tensile strength. Figure 14 represents the splitting tensile strength of rubberized concrete incorporating various treated rubber particles. This figure showed that the splitting tensile strength at 28 days was 42, 41.2 and 40 kg/cm² Fig. 11 Vibration signal of normal concrete Fig. 12 Vibration signal of rubberized concrete Fig. 13 Effect of treated materials on compressive strength

8 434 INDIAN J. ENG. MATER. SCI., DECEMBER 2007 incorporating normal rubber. The reduction in compressive strength in case of treated rubber was 14%, 15% and 17% of the normal concrete specimens. On the other hand, in case of untreated rubber (normal rubber), the reduction was 27% at the same percent of rubber (GWTR/TFA=20%). (vii) The percentages of increasing in tensile strength of rubberized concrete incorporating treated rubber particles by three sized agent PVA, SF and NaOH, were 12%, 10% and 7% respectively comparison to rubberized concrete specimens made without using any treated rubber. Fig. 14 Effect of treated materials on tensile strength for rubber treated by PVA, SF and NaOH respectively, this means that the reduction of tensile strengths in case of treated rubber was 7%, 8% and 11% of the normal concrete specimens. Figure 14 shows also the percentages of increasing splitting tensile strength for rubberized concrete incorporating treated rubber particles by three sized agent PVA, SF and NaOH, were 12%, 10% and 7% respectively comparison to rubberized concrete specimens made without using any treated rubber. Conclusions Based on the experimental results described in this paper, the following conclusions can be drawn: (i) The compressive and tensile strengths of Rubberized concretes were increased with increasing cement content for all different values of GWTR/TFA% by ratio. (ii) A reduction in the compressive and tensile strengths with increasing rubber content of the concrete mixes was observed. (iii) The mass density (bulk density) of hardened rubberized concrete decreases with increasing rubber content. This is an advantage for that concrete application. (iv) Rubberized concrete recorded higher toughness compared to ordinary concrete. (v) The damping ratio of the rubberized concrete containing 20% rubber was much higher than those of normal concrete by about 63.2%. (vi) Rubberized concrete incorporating treated rubber particles gave better results than concrete References 1 Garrick G M, Analysis and Testing of Waste Tire Fiber Modified Concrete, M. Sc., Mechanical Engineering Dept., Louisiana State University, Cecich V, Gonzales L, Hoisaeter A, Williams J & Reddy K R, Use of Shredded Tyres as a Lightweight Backfill Material for Retaining Structures, Report No. CE-GEE-94-02, University of Illinois at Chicago, Chicago, Illinois, U.S.A, 1994, 3 Humphrey D N, Sandford, T C, Cribbs, M M & Manion W P, Shear Strength and Compressibility of Tire Chips for Use as Retaining Wall Backfill, Transportation Research Record 1422, Washington D.C., (1993), U.S.A. 4 Jang J W, Yoo T, Oh J & Iwasaki I, Jpn-Korea. Resources, Conserv Recycl, 22 (1998) Biel T D & Lee H, Use of Recycled Tire Rubbers in Concrete, Proc ASCE 3 rd Materials Engineering Conf, Infrastructure: New Materials and Methods of Repair, 1994, Lee B I, Burnett L, Miller T, Postage B & Cuneo J, J Mater Sci Lett, 12 (1993) Toutanji H A, Cem Concr Compos, 18 (1996) Raghavan D, J Appl Polym Sci, 77 (2000) Kim J K, Int Polym Process, Munich, 13 (4) (1998) Raghavan D, Huynh H & Ferraris C F, J Mater Sci, 33 (1998) Eldin N N & Senouci A B, J Mater Civ Eng, 5 (4) (1993) Topcu I B, Cem Concr Res, 25 (2) (1995) Khatib Z K & Bayomy F M, J Mater Civ Eng, 11 (3) (1999) Fattuhi N I, Clark L A, Constr Build Mater, 10 (4) (1996) Hernandez-Olivares F, Barluenga G, Bollati M & Witoszek B, Cem Concr Res, 32 (10) (2002) Guneyisi E, Gesoglu M & Ozturan T, Cem Concr Res, 34 (2004) Humphrey D N & Eaton R A, Tire Chips as Subgrade Insulation-Field Trial, Symposium on Recovery and Effective Reuse of Discarded Materials and By-Products for Construction of Highway Facilities, Denver, Colorado, (1993), U.S.A.

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