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Experimental and modelling studies on high strength concrete containing waste tire rubber
Sustainable Cities and Society 19 (2015) 68–73
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Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Experimental and modelling studies on high strength concrete containing waste tire rubber Blessen Skariah Thomas ∗ , Ramesh Chandra Gupta, Vinu John Panicker Department of Civil Engineering, MNIT Jaipur, India
a r t i c l e
i n f o
Article history: Received 16 June 2015 Received in revised form 14 July 2015 Accepted 15 July 2015 Available online 20 July 2015 Keywords: Crumb rubber Sulphate attack Corrosion Abaqus
a b s t r a c t Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. A series of laboratory investigations were undertaken to evaluate the performance of concrete mixtures incorporating discarded tire rubber as aggregate. Numerous projects have been conducted to on the replacement of aggregates by crumb rubber, but scarce data are found in literature on high strength rubberized concrete. In this study, crumb rubber was partially substituted for fine aggregates from 0% to 20% in multiples of 2.5%. 6% silica fumes were added by weight of cement. The properties of concrete like compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed and the results were analyzed. The results showed that there was gradual decrease in the compressive strength of the specimens when compared to the control mix. Water absorption of sulphate attacked specimens showed a trend similar to that of the control mix. Macrocell corrosion and half cell potential measurements showed that there was no presence of corrosion. The analytical results from Abaqus followed the pattern of the results obtained from laboratory experiments. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Solid waste disposal is a worldwide problem. Recycling of these non-biodegradable waste materials is very difficult and a great challenge to the environmental engineers. Fly ash, marble sludge waste, incineration ash, rice husk-bark ash, bagasse ash, bottom ash, plastic waste, stone wastes, ceramic waste, copper slag, agricultural wastes, copper tailings, carbon steel slag, coal waste, mine waste, construction and demolition waste, ceramic waste, foundry slag, limestone waste, wood ash, furnace slag, welding slag, phosphogypsum slag, ISF slag, wollastonite, waste tire rubber, etc., are some of the some of the examples of municipal and industrial waste materials that pollute the environment. Mohammed, Anwar Hossain, Ting Eng Swee, Wong, and Abdullahi (2012), Nayef, Al-Rukaibi, and Bufarsan (2010), Onuaguluchi and Panesar (2014), Oikonomou and Mavridou (2009), Pelisser, Barcelos, Santos, Peterson, and Bernardin (2012), Al-Tayeb, Abu Bakar, Ismail, and Md Akil (2013), Azevedo, Pacheco-Torgal, Jesus, Aguiar, and Camoes
∗ Corresponding author. E-mail addresses: [email protected] (B.S. Thomas), [email protected] (R.C. Gupta), vinu [email protected] (V. John Panicker). http://dx.doi.org/10.1016/j.scs.2015.07.013 2210-6707/© 2015 Elsevier Ltd. All rights reserved.
(2012), Cuong Ho, Turatsinze, Hameed, and Chinh Vu (2012), Benazzouk et al. (2007), Garrick (2001), Guneyisi, Ozturan, and Geso˘glu (2007), Yilmaz and Degirmenci (2009). Proper waste management initiatives can stimulate innovation in recycling and reuse, limit land filling, reduce losses of resources and create incentives for behavioural change. It was estimated that in EU, about five tonnes of waste per person per year is generated on average, and little more than a third of that is effectively recycled. The European Zero Waste Programme aims to eliminate maximum waste materials by recycling and reuse, that will allow for a overall savings potential of D 630 billion per year for European industry and the creation of 580,000 new jobs until 2030 (SWD 2014-206). Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. (Pacheco-Torgal, Ding, & Jalali, 2012; Pelisser, Zavarise, Longo, & Bernardin, 2011; Richardson, Coventry, & Ward, 2012; Thomas, Damare, & Gupta, 2013). It is estimated that every year almost 1000 million tires end their service life and more than 50% are discarded without any treatment. By the year 2030, the number would reach to 1200 million tires yearly. (Including the stockpiled tires, there would be 5000 million tires to be discarded on a regular basis.) If the Indian
B.S. Thomas et al. / Sustainable Cities and Society 19 (2015) 68–73
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Table 1 Mixture proportions of fresh concrete. Cement (kg/m3 )
Water (kg/m3 )
Silica fumes (kg/m3 )
Coarse aggregate 10 mm (kg/m3 )
Coarse aggregate 20 mm (kg/m3 )
Fine aggregates (kg/m3 )
Admixture (%)
450.0
140.0
27.0
355.0
848.0
666.0
2
scenario is considered, it is estimated that the total number of discarded tires would be 112 million per year (after retreading twice). Rahman, Usman, and Al-Ghalib (2012), Thomas, Chandra Gupta, Kalla, and Csetenyi (2014), Thomas and Gupta Chandra (2015), Thomas, Chandra Gupta, Mehra, and Kumar (2015). Albano, Camacho, Reyes, Feliu, and Hernandez (2005) studied on the properties of concrete in which waste tire rubber (crumb rubber with size 0.29 mm and 0.59 mm) was substituted for 5% and 10% of fine aggregates by weight. Untreated and treated scrap rubber was used. The purpose of treatment with a solution of sodium hydroxide and a coupling agent silane was to increase the interfacial adhesion between the concrete and rubber. It was noticed that the particle size, density, compressive and splitting tensile strength of concrete decreased. The treatment with sodium hydroxide and silane does not produce any significant improvement in the mechanical properties of concrete. As the percentage of substitution increased, the ultrasonic pulse velocity decreased. Guneyisi, Geso˘glu, and Ozturan (2004) studied on the properties of rubberized concrete containing silica fumes. Crumb rubber and tire chips were used to replace fine and coarse aggregates respectively from 2.5% to 50% by volume. Silica fumes were used to replace cement from 5% to 20% and water–cement ratios of 0.6 and 0.4 was adopted. It was observed that the rubberized concrete with and without silica fumes were workable to a certain degree. The use of silica fumes in rubberized concrete helped to minimize the rate of strength loss. The concrete with compressive strength of 40 MPa was produced with rubber content 15% and water–cement ratio 0.4. Geso˘glu and Guneyisi (2007) investigated on the strength development and chloride penetration of rubberized concretes and pointed out that the unit weight of rubberized concrete decreased with increasing percentage of rubber added. There was reduction in unit weight up to 18%. The strength development patterns for plain and rubberized concrete between 3 and 7 days were relatively high, slower rate between 7 and 28 days, and relatively slower rate between 28 and 90 days. The compressive strength reduced systematically as the percentage of rubber was increased irrespective of the water–cement ratio and curing period. There was a systematic increase in the depth of chloride penetration for increase in the rubber content, with and without silica fumes. Xue and Shinozuka (2013) have studied on the dynamic and static performance of rubberized concrete. They have used the rubber crumb (maximum size 6 mm) for coarse aggregate replacement in 5–20% by volume of aggregates. A part of cement was replaced with silica fumes. It was observed that the addition of rubber crumb to concrete increased the damping ratio to 62% more than the control mix. Also the seismic force on the rubberized concrete was lesser by 27% than the control mix. Addition of silica fumes to rubberized concrete had helped to increase the strength by improving the bonding between the rubber crumb and the cement paste. In this study, concrete was designed with water–cement ratio of 0.3. Crumb rubber (waste tire rubber mechanically grinded into rubber crumbs) was partially substituted for fine aggregates from 0% to 20% in multiples of 2.5%. 6% silica fumes were added by weight of cement. The properties of concrete-like compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked
specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed. 2. Material properties and preparation of test specimens The properties of the raw materials and the methods of preparation of the specimens for testing are described below. 2.1. Raw materials Ordinary Portland Cement of grade 43, conforming to IS: 81121989 was used (specific gravity 3.15, normal consistency 34%, initial setting time 99 min, final setting time 176 min). Natural river sand confirming to zone II as per IS: 383-1970; void content 34% as per ASTM C 29, 2009 (specific gravity 2.63, free surface moisture 1%, fineness modulus 2.83). Coarse aggregates, 10 mm size was used 40% (fineness modulus – 5.573) and 20 mm size was used 60% (fineness modulus – 7.312) crushed stone were used as coarse aggregates with an average specific gravity – 2.63. Tire rubber was grinded into three sizes (powder form of 30 mesh, 0.8–2 mm, 2–4 mm). The specific gravity of rubber powder was 1.05 and that of the other two sizes were 1.13. The three sizes of crumb rubber were mixed in definite percentages (2–4 mm size in 25%, 0.8–2 mm size in 35% and rubber powder in 40%) to bring it to zone II. 2.2. Preparation of test specimens To investigate the suitability of discarded tire rubber as a substitute for fine aggregates in concrete, concrete was designed (As per IS: 10262-2010) with water–cement ratio of 0.3. The ratio of cement, fine aggregates and coarse aggregates are 1:1.48:2.67 by weight (1 part of cement, 1.48 parts of fine aggregates and 2.67 parts of coarse aggregates). 6% silica fumes were added by weight of cement. Crumb rubber was replaced for natural fine aggregates from 0% to 20% in multiple of 2.5%. The mixture proportion is given in Table 1. Super plasticizer was used as the admixture to arrive at the desired workability (above 0.91). In these mixes 9 cubes of size 100 mm were casted for sulphate attack test, concrete specimens of size 250 mm × 200 mm × 120 mm for corrosion test. The mixtures were prepared and casted at indoor temperature of 25–30 ◦ C. Compacting factor tests were done on fresh concrete to determine its workability. Moulds were covered with plastic sheets, soon after casting and de-moulded after 24 h. Curing was done for 28–90 days in water tank, with controlled temperature of 25–27 ◦ C. All the tests were performed as per the relevant ASTM and IS codes as given in the references. (ASTM C 267-97, IS, 1199-1959, IS 4562000, IS: 1237-1980, IS: 516-1959, IS: 2386-1963, IS 6441-1972, IS 6441-1989, etc.) 3. Laboratory testing programme Sulphate attack test was performed according to ASTM C 101289. The test specimens (100 mm concrete cubes) after 28 days of water curing, was taken oven dried weight and then subjected to continuous soaking for 3 months in 3% MgSO4 solution. Three types of tests were done on the sulphate attacked specimens. The specimens were periodically withdrawn at every 28, 56 and 91 days
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from the soaking tank and taken weight. The percentage reduction in weight with respect to the control specimens (the weight before immersing in MgSO4 solution) was calculated. The compressive strength of sulphate attacked specimens was determined after 91 days of immersion in MgSO4 solution. It was compared with the results of 28 days compressive strength of the non-sulphate attacked specimens. The water absorption test was done (as per ASTM C 642-2006) to study the changes in porosity of concrete due to sulphate attack. The concrete cubes were tested for water absorption after 91 days of immersion in MgSO4 solution. The cubes were oven dried at 60 ◦ C for 3 days and then kept at room temperature for 24 h and the weight noted. Then it was immersed in water for 48 h and the final weight noted. The values were compared with the water absorption values of the non-sulphate attacked specimens. Concrete specimens of size 250 mm × 200 mm × 120 mm were prepared as per ASTM G 109-2005 to measure the corrosion. On the reservoir at the top of the specimen, a solution of 3% sodium chloride (by weight) was poured. Then the specimens were subjected to alternate wetting and drying cycles (2 weeks wetting with sodium chloride solution, followed by 2 weeks drying). Two test procedures, half-cell potential and macro-cell method were used to measure (monitor) the corrosion activities of embedded steel bars in concrete. In the macro-cell readings, the potential difference between anode and cathode across a standard resister of 100 was measured. In the case of half-cell potential measurement, the potential difference between Copper–Copper Sulphate Electrode (CSE) and the top steel bar was measured. The potential measurements were taken with a high impedance voltmeter for both the wetting and drying cycles. Damaged plasticity model was used in the modelling of concrete. The analytical study is used to compare the values obtained in the experimental procedure and to study the trend of compressive and flexural tensile strength. The stress–strain values defining the tension and compression of the concrete and the density of the individual concrete specimens were used as the input values, due to the fact that there are no pre-defined values for rubberized concrete (concrete + rubber) in Abacus.
Fig. 1. Variation in weight of sulphate attacked specimen.
Fig. 2. Reduction in compressive strength of sulphate attacked specimen.
4. Analysis of results and discussion The results obtained for the compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus were analyzed as below.
in the compressive strength of the rubberized concrete specimens when compared to the control mix. The decrease in compressive strength for the mix with 0% crumb rubber was 1.97%. The compressive strength value of the mix with 10% crumb rubber was 3.43% and that of the mix with 20% crumb rubber was 5.01%.
4.1. Sulphate attack test 4.1.1. Variation in weight of sulphate attacked specimen Fig. 1 shows the variation in weight of sulphate attacked specimens with respect to the percentage of crumb rubber. It was noticed that for all the specimens, there was gradual increase in the weight of the specimens from 28 to 56 days and from 56 to 91 days. At the end of 91 days, there was an increase in the weight of the control mix specimen by 0.5%. Gradual increase in the weight was observed as the amount of crumb rubber was increased. The increase in weight of the mix with 10% crumb rubber was 0.54% and that of the mix with 20% crumb rubber was 0.65%. We could find that more amount of water was absorbed by the concrete in which there was more amount of crumb rubber. 4.1.2. Variation in compressive strength of sulphate attacked specimen Fig. 2 shows the variation in compressive strength of sulphate attacked specimen. It was observed that there was gradual decrease
Fig. 3. Water absorption (%) of sulphate attacked specimen.
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4.1.3. Water absorption of sulphate attacked specimen Fig. 3 shows the results for the water absorption test of sulphate attacked specimen. It was observed that the percentage of water absorption had shown a decreasing trend from the mix with 0% crumb rubber to the mix with 7.5% crumb rubber. The water absorption of the mix with 0% and 10% crumb rubber was 0.74%. Similar to the values obtained in the water absorption test of the control specimen, an increase in the amount of water absorption was noticed from the mix with 10% crumb rubber to the mix with 20% crumb rubber. The water absorption of the mix with 10% crumb rubber was 0.74% and that of the mix with 20% crumb rubber was 0.98%. We can observe that the water absorption reduces up to 7.5% of crumb rubber. This is due to the fact that the rubber particles are impervious and does not absorb water. As the percentage of crumb rubber increased, the water absorption decreased. However beyond 7.5% the water absorption increased and it may be due to the lack of internal packing of the concrete.
4.2. Test for corrosion of steel reinforcements 4.2.1. Macrocell corrosion The graph showing the results for the macrocell corrosion is reported in Fig. 4. As per ASTM G 109-99a, a minimum of 10 A is required to ensure the presence of sufficient corrosion. If the macrocell current is positive, it indicates active corrosion in progress and vice versa. It was noticed in all the series that all the macrocell readings were negative up to 91 days. It is noticed that the readings are gradually increasing from the initial day to 91 day. There is a trend for the results to move from negative to positive. The initial reading of the control mix was −1.57 A and that of the mix with 20% crumb rubber was 1.69 A. The macrocell reading of the control mix at 91 days was −1.04 A and that of the mix with 20% crumb rubber was −1.09 A. Since all the readings obtained were less than 10 A, we could conclude that there is no presence of sufficient corrosion in the specimens.
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Fig. 4. Macrocell current of concrete specimens.
4.2.2. Half-cell potentials The results of the variations in half-cell potentials with respect to the percentage of crumb rubber are reported in Fig. 5. It was observed that the readings of all the mixes were decreasing from the initial day to the final day (91 days). The initial reading of control mix was −1.11 mV and the final reading was −1.38 mV. When the mix with 20% crumb rubber is considered, the initial reading was −1.05 mV and the final reading was −1.29 mV. As per ASTM C 876, if potentials over an area are more positive than −0.20 V CSE, there is a greater than 90% probability that no reinforcing steel corrosion is occurring in that area at the time of measurement. If it is in between −0.20 and −0.35 V CSE corrosion activities in that area uncertain and if it is more negative than −0.35 V CSE there is greater than 90% probability that reinforcing steel corrosion is occurring in that area. In our case, all the potential readings were more positive than 0.20 V. So we can assume that no reinforcement corrosion was taking place in any of the specimens at the time of measurement.
Fig. 5. Half-cell potentials of concrete specimens.
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Fig. 6. Analytical results for compressive strength of concrete (0%, 10% and 20% crumb rubber).
Fig. 7. Analytical results for flexural tensile strength of concrete (0%, 10% and 20% crumb rubber).
Fig. 8. Comparison of compressive strength of experimental and analytical results. Fig. 9. Comparison of flexural tensile strength of experimental and analytical results.
4.3. Analytical results from Abaqus 4.4. Comparison of experimental and modelling results The results obtained from the analytical studies for the mixes with 0%, 10% and 20% crumb rubber are reported in Figs. 6 and 7. When we observe the analytical results of the compressive strength, brittle failure could be seen in the mixes with crumb rubber and it was not found in the case of control mix. But when we check the practical test results, the control specimens exhibited brittle failure while the rubberized concrete did not show brittle failure under compression loading. The analytical result of the compressive strength of concrete with 20% crumb rubber is similar to the result obtained in the laboratory. All the other analytical results were lower than the values obtained in the experimental analysis.
The graphs showing the comparison of experimental and analytical results of compressive strength and flexural strength are shown in Figs. 8 and 9. The comparison was done with the compressive and flexural strength obtained at 28 days of curing. When we compare the results of compressive strength and flexural tensile strength obtained from the laboratory experimental work and the analytical results in Abacus, it was observed that the analytical results follow the pattern of the results obtained from laboratory experiments. Most of the analytical results were not exactly same as the experimental results, but it has shown values slightly lower than
B.S. Thomas et al. / Sustainable Cities and Society 19 (2015) 68–73
that of the experimental values. The difference can be due to the minor errors in modelling. 5. Conclusions To investigate the suitability of discarded tire rubber as a substitute for fine aggregates in concrete, concrete was designed (As per IS: 10262-2010) with water–cement ratio 0.3. The ratio of cement, fine aggregates and coarse aggregates are 1:1.48:2.67 by weight (1 part of cement, 1.48 parts of fine aggregates and 2.67 parts of coarse aggregates). 6% silica fumes were added by weight of cement. Crumb rubber was replaced for natural fine aggregates from 0% to 20% in multiple of 2.5%. The properties of concretelike compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed. The following conclusions may be drawn from this study. (1) From the variation in weight measurement of sulphate attacked specimens, it was noticed that for all the specimens, there was gradual increase in the weight of the specimens from 28 to 56 days and from 56 to 91 days. From the compressive strength measurement of sulphate attacked specimens, there was gradual decrease in the compressive strength of the specimens when compared to the control mix. Water absorption of sulphate attacked specimens showed a trend similar to that of the control mix. (2) From the macrocell corrosion test, since all the readings obtained were less than 10 A, we could conclude that there is no presence of sufficient corrosion in the specimens. From half cell potential measurements, all the potential readings were more positive than 0.20 V. So we can assume that no reinforcement corrosion was taking place in any of the specimens at the time of measurement. (3) When we compare the results of compressive strength and flexural tensile strength obtained from the laboratory experimental work and the analytical results in Abacus, it was observed that the analytical results follow the pattern of the results obtained from laboratory experiments. Most of the analytical results were not exactly same as the experimental results, but it has shown values slightly lower than that of the experimental values. References Albano, C., Camacho, N., Reyes, J., Feliu, J. L., & Hernandez, M. (2005). Influence of scrap rubber addition to Portland I concrete composites: Destructive and non-destructive testing. Composite Structures, 71, 439–446. Al-Tayeb, M. M., Abu Bakar, B. H., Ismail, H., & Md Akil, H. (2013). Effect of partial replacement of sand by recycled fine crumb rubber on the performance of hybrid rubberized- normal concrete under impact load: experiment and simulation. Journal of Cleaner Production, 59, 284–289. ASTM C 1012-89. Standard test method for length change of hydraulic-cement mortars exposed to a sulfate solution. West Conshohocken, PA, United States. ASTM C 267-97. Standard test methods for chemical resistance of mortars, grouts and monolithic surfacings and polymer concretes. West Conshohocken, PA, United States. (Source: http://www.scribd.com/doc/230862438/C267) ASTM C 642-06. Standard Test method for Density, Absorption, and Voids in Hardened Concrete. West Conshohocken, PA, United States. ASTM C 876-09. Standard test method for corrosion potentials of uncoated reinforcing steel in concrete. West Conshohocken, PA, United States. ASTM G 109-99a. Standard test method for determining the effects of chemical admixtures on the corrosion of embedded steel reinforcement in concrete exposed to chloride environments. West Conshohocken, PA, United States. Azevedo, F., Pacheco-Torgal, F., Jesus, C., Aguiar, J. B., & Camoes, A. (2012). Properties and durability of HPC with tire rubber wastes. Construction and Building Materials, 34, 186–191.
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Contents lists available at ScienceDirect
Sustainable Cities and Society journal homepage: www.elsevier.com/locate/scs
Experimental and modelling studies on high strength concrete containing waste tire rubber Blessen Skariah Thomas ∗ , Ramesh Chandra Gupta, Vinu John Panicker Department of Civil Engineering, MNIT Jaipur, India
a r t i c l e
i n f o
Article history: Received 16 June 2015 Received in revised form 14 July 2015 Accepted 15 July 2015 Available online 20 July 2015 Keywords: Crumb rubber Sulphate attack Corrosion Abaqus
a b s t r a c t Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. A series of laboratory investigations were undertaken to evaluate the performance of concrete mixtures incorporating discarded tire rubber as aggregate. Numerous projects have been conducted to on the replacement of aggregates by crumb rubber, but scarce data are found in literature on high strength rubberized concrete. In this study, crumb rubber was partially substituted for fine aggregates from 0% to 20% in multiples of 2.5%. 6% silica fumes were added by weight of cement. The properties of concrete like compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed and the results were analyzed. The results showed that there was gradual decrease in the compressive strength of the specimens when compared to the control mix. Water absorption of sulphate attacked specimens showed a trend similar to that of the control mix. Macrocell corrosion and half cell potential measurements showed that there was no presence of corrosion. The analytical results from Abaqus followed the pattern of the results obtained from laboratory experiments. © 2015 Elsevier Ltd. All rights reserved.
1. Introduction Solid waste disposal is a worldwide problem. Recycling of these non-biodegradable waste materials is very difficult and a great challenge to the environmental engineers. Fly ash, marble sludge waste, incineration ash, rice husk-bark ash, bagasse ash, bottom ash, plastic waste, stone wastes, ceramic waste, copper slag, agricultural wastes, copper tailings, carbon steel slag, coal waste, mine waste, construction and demolition waste, ceramic waste, foundry slag, limestone waste, wood ash, furnace slag, welding slag, phosphogypsum slag, ISF slag, wollastonite, waste tire rubber, etc., are some of the some of the examples of municipal and industrial waste materials that pollute the environment. Mohammed, Anwar Hossain, Ting Eng Swee, Wong, and Abdullahi (2012), Nayef, Al-Rukaibi, and Bufarsan (2010), Onuaguluchi and Panesar (2014), Oikonomou and Mavridou (2009), Pelisser, Barcelos, Santos, Peterson, and Bernardin (2012), Al-Tayeb, Abu Bakar, Ismail, and Md Akil (2013), Azevedo, Pacheco-Torgal, Jesus, Aguiar, and Camoes
∗ Corresponding author. E-mail addresses: [email protected] (B.S. Thomas), [email protected] (R.C. Gupta), vinu [email protected] (V. John Panicker). http://dx.doi.org/10.1016/j.scs.2015.07.013 2210-6707/© 2015 Elsevier Ltd. All rights reserved.
(2012), Cuong Ho, Turatsinze, Hameed, and Chinh Vu (2012), Benazzouk et al. (2007), Garrick (2001), Guneyisi, Ozturan, and Geso˘glu (2007), Yilmaz and Degirmenci (2009). Proper waste management initiatives can stimulate innovation in recycling and reuse, limit land filling, reduce losses of resources and create incentives for behavioural change. It was estimated that in EU, about five tonnes of waste per person per year is generated on average, and little more than a third of that is effectively recycled. The European Zero Waste Programme aims to eliminate maximum waste materials by recycling and reuse, that will allow for a overall savings potential of D 630 billion per year for European industry and the creation of 580,000 new jobs until 2030 (SWD 2014-206). Disposal of waste tire rubber has become a major environmental issue in all parts of the world. Every year millions of tires are discarded, thrown away or buried all over the world, representing a very serious threat to the ecology. (Pacheco-Torgal, Ding, & Jalali, 2012; Pelisser, Zavarise, Longo, & Bernardin, 2011; Richardson, Coventry, & Ward, 2012; Thomas, Damare, & Gupta, 2013). It is estimated that every year almost 1000 million tires end their service life and more than 50% are discarded without any treatment. By the year 2030, the number would reach to 1200 million tires yearly. (Including the stockpiled tires, there would be 5000 million tires to be discarded on a regular basis.) If the Indian
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Table 1 Mixture proportions of fresh concrete. Cement (kg/m3 )
Water (kg/m3 )
Silica fumes (kg/m3 )
Coarse aggregate 10 mm (kg/m3 )
Coarse aggregate 20 mm (kg/m3 )
Fine aggregates (kg/m3 )
Admixture (%)
450.0
140.0
27.0
355.0
848.0
666.0
2
scenario is considered, it is estimated that the total number of discarded tires would be 112 million per year (after retreading twice). Rahman, Usman, and Al-Ghalib (2012), Thomas, Chandra Gupta, Kalla, and Csetenyi (2014), Thomas and Gupta Chandra (2015), Thomas, Chandra Gupta, Mehra, and Kumar (2015). Albano, Camacho, Reyes, Feliu, and Hernandez (2005) studied on the properties of concrete in which waste tire rubber (crumb rubber with size 0.29 mm and 0.59 mm) was substituted for 5% and 10% of fine aggregates by weight. Untreated and treated scrap rubber was used. The purpose of treatment with a solution of sodium hydroxide and a coupling agent silane was to increase the interfacial adhesion between the concrete and rubber. It was noticed that the particle size, density, compressive and splitting tensile strength of concrete decreased. The treatment with sodium hydroxide and silane does not produce any significant improvement in the mechanical properties of concrete. As the percentage of substitution increased, the ultrasonic pulse velocity decreased. Guneyisi, Geso˘glu, and Ozturan (2004) studied on the properties of rubberized concrete containing silica fumes. Crumb rubber and tire chips were used to replace fine and coarse aggregates respectively from 2.5% to 50% by volume. Silica fumes were used to replace cement from 5% to 20% and water–cement ratios of 0.6 and 0.4 was adopted. It was observed that the rubberized concrete with and without silica fumes were workable to a certain degree. The use of silica fumes in rubberized concrete helped to minimize the rate of strength loss. The concrete with compressive strength of 40 MPa was produced with rubber content 15% and water–cement ratio 0.4. Geso˘glu and Guneyisi (2007) investigated on the strength development and chloride penetration of rubberized concretes and pointed out that the unit weight of rubberized concrete decreased with increasing percentage of rubber added. There was reduction in unit weight up to 18%. The strength development patterns for plain and rubberized concrete between 3 and 7 days were relatively high, slower rate between 7 and 28 days, and relatively slower rate between 28 and 90 days. The compressive strength reduced systematically as the percentage of rubber was increased irrespective of the water–cement ratio and curing period. There was a systematic increase in the depth of chloride penetration for increase in the rubber content, with and without silica fumes. Xue and Shinozuka (2013) have studied on the dynamic and static performance of rubberized concrete. They have used the rubber crumb (maximum size 6 mm) for coarse aggregate replacement in 5–20% by volume of aggregates. A part of cement was replaced with silica fumes. It was observed that the addition of rubber crumb to concrete increased the damping ratio to 62% more than the control mix. Also the seismic force on the rubberized concrete was lesser by 27% than the control mix. Addition of silica fumes to rubberized concrete had helped to increase the strength by improving the bonding between the rubber crumb and the cement paste. In this study, concrete was designed with water–cement ratio of 0.3. Crumb rubber (waste tire rubber mechanically grinded into rubber crumbs) was partially substituted for fine aggregates from 0% to 20% in multiples of 2.5%. 6% silica fumes were added by weight of cement. The properties of concrete-like compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked
specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed. 2. Material properties and preparation of test specimens The properties of the raw materials and the methods of preparation of the specimens for testing are described below. 2.1. Raw materials Ordinary Portland Cement of grade 43, conforming to IS: 81121989 was used (specific gravity 3.15, normal consistency 34%, initial setting time 99 min, final setting time 176 min). Natural river sand confirming to zone II as per IS: 383-1970; void content 34% as per ASTM C 29, 2009 (specific gravity 2.63, free surface moisture 1%, fineness modulus 2.83). Coarse aggregates, 10 mm size was used 40% (fineness modulus – 5.573) and 20 mm size was used 60% (fineness modulus – 7.312) crushed stone were used as coarse aggregates with an average specific gravity – 2.63. Tire rubber was grinded into three sizes (powder form of 30 mesh, 0.8–2 mm, 2–4 mm). The specific gravity of rubber powder was 1.05 and that of the other two sizes were 1.13. The three sizes of crumb rubber were mixed in definite percentages (2–4 mm size in 25%, 0.8–2 mm size in 35% and rubber powder in 40%) to bring it to zone II. 2.2. Preparation of test specimens To investigate the suitability of discarded tire rubber as a substitute for fine aggregates in concrete, concrete was designed (As per IS: 10262-2010) with water–cement ratio of 0.3. The ratio of cement, fine aggregates and coarse aggregates are 1:1.48:2.67 by weight (1 part of cement, 1.48 parts of fine aggregates and 2.67 parts of coarse aggregates). 6% silica fumes were added by weight of cement. Crumb rubber was replaced for natural fine aggregates from 0% to 20% in multiple of 2.5%. The mixture proportion is given in Table 1. Super plasticizer was used as the admixture to arrive at the desired workability (above 0.91). In these mixes 9 cubes of size 100 mm were casted for sulphate attack test, concrete specimens of size 250 mm × 200 mm × 120 mm for corrosion test. The mixtures were prepared and casted at indoor temperature of 25–30 ◦ C. Compacting factor tests were done on fresh concrete to determine its workability. Moulds were covered with plastic sheets, soon after casting and de-moulded after 24 h. Curing was done for 28–90 days in water tank, with controlled temperature of 25–27 ◦ C. All the tests were performed as per the relevant ASTM and IS codes as given in the references. (ASTM C 267-97, IS, 1199-1959, IS 4562000, IS: 1237-1980, IS: 516-1959, IS: 2386-1963, IS 6441-1972, IS 6441-1989, etc.) 3. Laboratory testing programme Sulphate attack test was performed according to ASTM C 101289. The test specimens (100 mm concrete cubes) after 28 days of water curing, was taken oven dried weight and then subjected to continuous soaking for 3 months in 3% MgSO4 solution. Three types of tests were done on the sulphate attacked specimens. The specimens were periodically withdrawn at every 28, 56 and 91 days
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from the soaking tank and taken weight. The percentage reduction in weight with respect to the control specimens (the weight before immersing in MgSO4 solution) was calculated. The compressive strength of sulphate attacked specimens was determined after 91 days of immersion in MgSO4 solution. It was compared with the results of 28 days compressive strength of the non-sulphate attacked specimens. The water absorption test was done (as per ASTM C 642-2006) to study the changes in porosity of concrete due to sulphate attack. The concrete cubes were tested for water absorption after 91 days of immersion in MgSO4 solution. The cubes were oven dried at 60 ◦ C for 3 days and then kept at room temperature for 24 h and the weight noted. Then it was immersed in water for 48 h and the final weight noted. The values were compared with the water absorption values of the non-sulphate attacked specimens. Concrete specimens of size 250 mm × 200 mm × 120 mm were prepared as per ASTM G 109-2005 to measure the corrosion. On the reservoir at the top of the specimen, a solution of 3% sodium chloride (by weight) was poured. Then the specimens were subjected to alternate wetting and drying cycles (2 weeks wetting with sodium chloride solution, followed by 2 weeks drying). Two test procedures, half-cell potential and macro-cell method were used to measure (monitor) the corrosion activities of embedded steel bars in concrete. In the macro-cell readings, the potential difference between anode and cathode across a standard resister of 100 was measured. In the case of half-cell potential measurement, the potential difference between Copper–Copper Sulphate Electrode (CSE) and the top steel bar was measured. The potential measurements were taken with a high impedance voltmeter for both the wetting and drying cycles. Damaged plasticity model was used in the modelling of concrete. The analytical study is used to compare the values obtained in the experimental procedure and to study the trend of compressive and flexural tensile strength. The stress–strain values defining the tension and compression of the concrete and the density of the individual concrete specimens were used as the input values, due to the fact that there are no pre-defined values for rubberized concrete (concrete + rubber) in Abacus.
Fig. 1. Variation in weight of sulphate attacked specimen.
Fig. 2. Reduction in compressive strength of sulphate attacked specimen.
4. Analysis of results and discussion The results obtained for the compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus were analyzed as below.
in the compressive strength of the rubberized concrete specimens when compared to the control mix. The decrease in compressive strength for the mix with 0% crumb rubber was 1.97%. The compressive strength value of the mix with 10% crumb rubber was 3.43% and that of the mix with 20% crumb rubber was 5.01%.
4.1. Sulphate attack test 4.1.1. Variation in weight of sulphate attacked specimen Fig. 1 shows the variation in weight of sulphate attacked specimens with respect to the percentage of crumb rubber. It was noticed that for all the specimens, there was gradual increase in the weight of the specimens from 28 to 56 days and from 56 to 91 days. At the end of 91 days, there was an increase in the weight of the control mix specimen by 0.5%. Gradual increase in the weight was observed as the amount of crumb rubber was increased. The increase in weight of the mix with 10% crumb rubber was 0.54% and that of the mix with 20% crumb rubber was 0.65%. We could find that more amount of water was absorbed by the concrete in which there was more amount of crumb rubber. 4.1.2. Variation in compressive strength of sulphate attacked specimen Fig. 2 shows the variation in compressive strength of sulphate attacked specimen. It was observed that there was gradual decrease
Fig. 3. Water absorption (%) of sulphate attacked specimen.
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4.1.3. Water absorption of sulphate attacked specimen Fig. 3 shows the results for the water absorption test of sulphate attacked specimen. It was observed that the percentage of water absorption had shown a decreasing trend from the mix with 0% crumb rubber to the mix with 7.5% crumb rubber. The water absorption of the mix with 0% and 10% crumb rubber was 0.74%. Similar to the values obtained in the water absorption test of the control specimen, an increase in the amount of water absorption was noticed from the mix with 10% crumb rubber to the mix with 20% crumb rubber. The water absorption of the mix with 10% crumb rubber was 0.74% and that of the mix with 20% crumb rubber was 0.98%. We can observe that the water absorption reduces up to 7.5% of crumb rubber. This is due to the fact that the rubber particles are impervious and does not absorb water. As the percentage of crumb rubber increased, the water absorption decreased. However beyond 7.5% the water absorption increased and it may be due to the lack of internal packing of the concrete.
4.2. Test for corrosion of steel reinforcements 4.2.1. Macrocell corrosion The graph showing the results for the macrocell corrosion is reported in Fig. 4. As per ASTM G 109-99a, a minimum of 10 A is required to ensure the presence of sufficient corrosion. If the macrocell current is positive, it indicates active corrosion in progress and vice versa. It was noticed in all the series that all the macrocell readings were negative up to 91 days. It is noticed that the readings are gradually increasing from the initial day to 91 day. There is a trend for the results to move from negative to positive. The initial reading of the control mix was −1.57 A and that of the mix with 20% crumb rubber was 1.69 A. The macrocell reading of the control mix at 91 days was −1.04 A and that of the mix with 20% crumb rubber was −1.09 A. Since all the readings obtained were less than 10 A, we could conclude that there is no presence of sufficient corrosion in the specimens.
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Fig. 4. Macrocell current of concrete specimens.
4.2.2. Half-cell potentials The results of the variations in half-cell potentials with respect to the percentage of crumb rubber are reported in Fig. 5. It was observed that the readings of all the mixes were decreasing from the initial day to the final day (91 days). The initial reading of control mix was −1.11 mV and the final reading was −1.38 mV. When the mix with 20% crumb rubber is considered, the initial reading was −1.05 mV and the final reading was −1.29 mV. As per ASTM C 876, if potentials over an area are more positive than −0.20 V CSE, there is a greater than 90% probability that no reinforcing steel corrosion is occurring in that area at the time of measurement. If it is in between −0.20 and −0.35 V CSE corrosion activities in that area uncertain and if it is more negative than −0.35 V CSE there is greater than 90% probability that reinforcing steel corrosion is occurring in that area. In our case, all the potential readings were more positive than 0.20 V. So we can assume that no reinforcement corrosion was taking place in any of the specimens at the time of measurement.
Fig. 5. Half-cell potentials of concrete specimens.
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Fig. 6. Analytical results for compressive strength of concrete (0%, 10% and 20% crumb rubber).
Fig. 7. Analytical results for flexural tensile strength of concrete (0%, 10% and 20% crumb rubber).
Fig. 8. Comparison of compressive strength of experimental and analytical results. Fig. 9. Comparison of flexural tensile strength of experimental and analytical results.
4.3. Analytical results from Abaqus 4.4. Comparison of experimental and modelling results The results obtained from the analytical studies for the mixes with 0%, 10% and 20% crumb rubber are reported in Figs. 6 and 7. When we observe the analytical results of the compressive strength, brittle failure could be seen in the mixes with crumb rubber and it was not found in the case of control mix. But when we check the practical test results, the control specimens exhibited brittle failure while the rubberized concrete did not show brittle failure under compression loading. The analytical result of the compressive strength of concrete with 20% crumb rubber is similar to the result obtained in the laboratory. All the other analytical results were lower than the values obtained in the experimental analysis.
The graphs showing the comparison of experimental and analytical results of compressive strength and flexural strength are shown in Figs. 8 and 9. The comparison was done with the compressive and flexural strength obtained at 28 days of curing. When we compare the results of compressive strength and flexural tensile strength obtained from the laboratory experimental work and the analytical results in Abacus, it was observed that the analytical results follow the pattern of the results obtained from laboratory experiments. Most of the analytical results were not exactly same as the experimental results, but it has shown values slightly lower than
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that of the experimental values. The difference can be due to the minor errors in modelling. 5. Conclusions To investigate the suitability of discarded tire rubber as a substitute for fine aggregates in concrete, concrete was designed (As per IS: 10262-2010) with water–cement ratio 0.3. The ratio of cement, fine aggregates and coarse aggregates are 1:1.48:2.67 by weight (1 part of cement, 1.48 parts of fine aggregates and 2.67 parts of coarse aggregates). 6% silica fumes were added by weight of cement. Crumb rubber was replaced for natural fine aggregates from 0% to 20% in multiple of 2.5%. The properties of concretelike compressive strength of sulphate attacked specimen, water absorption of sulphate attacked specimen, variation in weight of sulphate attacked specimen, macro cell current measurement, half cell potentials and modelling in Abacus was performed. The following conclusions may be drawn from this study. (1) From the variation in weight measurement of sulphate attacked specimens, it was noticed that for all the specimens, there was gradual increase in the weight of the specimens from 28 to 56 days and from 56 to 91 days. From the compressive strength measurement of sulphate attacked specimens, there was gradual decrease in the compressive strength of the specimens when compared to the control mix. Water absorption of sulphate attacked specimens showed a trend similar to that of the control mix. (2) From the macrocell corrosion test, since all the readings obtained were less than 10 A, we could conclude that there is no presence of sufficient corrosion in the specimens. From half cell potential measurements, all the potential readings were more positive than 0.20 V. So we can assume that no reinforcement corrosion was taking place in any of the specimens at the time of measurement. (3) When we compare the results of compressive strength and flexural tensile strength obtained from the laboratory experimental work and the analytical results in Abacus, it was observed that the analytical results follow the pattern of the results obtained from laboratory experiments. Most of the analytical results were not exactly same as the experimental results, but it has shown values slightly lower than that of the experimental values. References Albano, C., Camacho, N., Reyes, J., Feliu, J. L., & Hernandez, M. (2005). Influence of scrap rubber addition to Portland I concrete composites: Destructive and non-destructive testing. Composite Structures, 71, 439–446. Al-Tayeb, M. M., Abu Bakar, B. H., Ismail, H., & Md Akil, H. (2013). Effect of partial replacement of sand by recycled fine crumb rubber on the performance of hybrid rubberized- normal concrete under impact load: experiment and simulation. Journal of Cleaner Production, 59, 284–289. ASTM C 1012-89. Standard test method for length change of hydraulic-cement mortars exposed to a sulfate solution. West Conshohocken, PA, United States. ASTM C 267-97. Standard test methods for chemical resistance of mortars, grouts and monolithic surfacings and polymer concretes. West Conshohocken, PA, United States. (Source: http://www.scribd.com/doc/230862438/C267) ASTM C 642-06. Standard Test method for Density, Absorption, and Voids in Hardened Concrete. West Conshohocken, PA, United States. ASTM C 876-09. Standard test method for corrosion potentials of uncoated reinforcing steel in concrete. West Conshohocken, PA, United States. ASTM G 109-99a. Standard test method for determining the effects of chemical admixtures on the corrosion of embedded steel reinforcement in concrete exposed to chloride environments. West Conshohocken, PA, United States. Azevedo, F., Pacheco-Torgal, F., Jesus, C., Aguiar, J. B., & Camoes, A. (2012). Properties and durability of HPC with tire rubber wastes. Construction and Building Materials, 34, 186–191.
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