Crumb Rubber Research Articles

Workability Investigation on the Fresh Mix of ECC Mortar and Crumb Rubber (CR)-ECC based on Variations of Palm Shell Ash, River Sand, and Cement

Engineered cementitious composite (ECC) is a composite that has better tensile properties and behavior than concrete. ECCs are usually made of cement, water, silica sand, cementitious materials, fibers, and other additives. The term ECC mortar is used because the ECC does not use fiber. The cementitious material in this research uses palm shell ash, with a proportion of 5%, 10%, and 15% of the cement weight. As a replacement for the fiber, crumb rubbers are used, with proportions of 2.5%; 5%; 7.5%; 10% and 12.5% of the cement weight. Workability was measured based on slumpflow tests (with measurements T500 and slumpflow diameter). The objective of this study is to establish the workability of fresh mix of the ECC mortar and CR-ECC with variations in the addition of palm shell ash, cement, sand and crumb rubber. Based on the results of slumpflow tests, the average diameter for fresh ECC mortars ranges between 88 cm to 106.5 cm, and the T500 ranges from 0.28 seconds to 1.39 seconds. As for fresh CR-ECC mix, the mean slumpflow diameter is between 71 cm to 93 cm and the T500 ranging between 0.90 seconds and 1.68 seconds. All of these values meet the slumpflow requirements stipulated by EFNARC. Nevertheless, the workability of the fresh mix ECC mortar is more flowable than the fresh mix CR-ECC. This is because crumb rubbers are water-absorbing.

Influence of graft-activated crumb rubber on the aging performance of modified bitumen: Experimental analysis and molecular dynamics simulation

This paper centers on the assessment of how graft-activated crumb rubber (GR) affects the aging properties of modified bitumen. Three bitumen samples, namely matrix bitumen (MB), crumb rubber modified bitumen (CB) and graft-activated crumb rubber modified bitumen (GB) were aged by rotating thin film oven test (RTFOT) and pressure aging vessel (PAV). The physical and rheological performance of the bitumen were assessed before and after aging, and the aging mechanism was analyzed using Fourier-transform infrared spectroscopy (FTIR) and molecular dynamics (MD) simulation. The results indicated that GR significantly improved bitumen performance in both high and low temperatures after being aged, enhancing its anti-aging properties. This positive effect was attributed to the physical swelling of GR in bitumen and chemical reactions between the amide group in GR and the anhydride group in bitumen. These reactions depleted the polar molecular content in bitumen, reducing its susceptibility to oxidation. A comparison of FTIR results between CB and GB demonstrated the absence of the anhydride group and reduced levels of the carbonyl index (CI) and sulfoxide index (SI) in GB, confirming the occurrence of chemical reactions. MD simulations further revealed that GB exhibited the highest fractional free volume (FFV) after being aged and displayed inferior agglomeration behavior towards light components compared to crumb rubber (CR). In conclusion, the combined experimental and analytical findings collectively affirmed that the primary factor contributing to the enhanced anti-aging properties of GB was the chemical reaction between GR and bitumen.

Enhancing the Storage Stability and Rutting Resistance of Modified Asphalt through Surface Functionalization of Waste Tire Rubber Powder

Waste tire rubber powder-modified asphalt (RMA) has been widely used in road construction, which was traditionally limited by the poor compatibility of RMA, affecting pavement performance. By synthesizing epoxy soybean oil with amide groups (ESO/TETA) and grafting it onto desulfurized rubber powder (DCR) through microwave irradiation, a surface-functionalized rubber powder (MDCR) was produced successfully. The effects of the physical properties, storage stability, thermal stability, and rheological behavior of the modified asphalt were studied. The results show that the MDCR with a polar surface improved the compatibility and adhesive interactions between the modified crumb rubber and the asphalt. The MDCR content could reach 50%, and the phase separation could meet the requirements of 2.2 °C, which has application conditions in engineering for stable storage. Additionally, the inclusion of MDCR in the asphalt formulations significantly mitigated the temperature sensitivity of the modified asphalt. Importantly, when the MDCR constituted from 20% to 50% of the asphalt, there was a noted reduction in the phase angle at temperatures above 70 °C, indicating a significant improvement in the elastic efficiency. The MDCR also led to substantial enhancements in the resistance of the asphalt to high-temperature and high-stress rutting, addressing the crucial limitations in the consumption ability of waste tire rubber powder and improving the overall performance of RMA in pavement applications.

The effect of sand-crumb rubber mixture treatment on the seismic response of a low-rise building located on liquefiable soil

One of the most effective measures to reduce earthquake risks in high-seismic areas is to reduce the input forces caused by earthquakes to the structure. The properties of rubber materials in geotechnical projects are energy absorption, dynamic deformation change as well as damping of latent energy in loads, high shear modulus and damping ratio, easy access and their economic nature. In this research, with finite difference modeling, the effect of using sand- crumb rubber layer on the seismic behavior of the model has been obtained. In the following, by changing the thickness and depth of the sand-crumb rubber layer, the seismic behavior such as floor displacement and internal forces have been investigated. This research numerically models liquefaction (UBCsand with FLAC) and predicts the effects of the sand-crumb rubber layer of different thicknesses (as % weight of the mixture) under the foundation and evaluates the structure's damage and settlement interacting with the soil by validating the numerical model with the laboratory model and calibrating it with different ratios. The results show that liquefaction, pore water pressure excess ratio and soil settlement will be significantly reduced with the presence of sand-crumb rubber layer, and also the base shear has shown an increase, but the structural damage is reduced.Graphical

Mechanical and Environmental Analysis of Granular Subbase with Fine Crumb Rubber

The increasing manufacturing of tires, driven by the automotive sector, has led to various sustainability and waste management issues. Consequently, it is necessary to explore alternatives for the reuse of these wastes. Rubber has demonstrated properties that could make it an attractive material for use as a granular aggregate. The aim of this study is to evaluate the influence of crumb rubber (CR) on the mechanical behavior of a granular subbase (GSB) by replacing fine CR at 10% and 15%. An environmental analysis of the proposal was conducted using the SimaPro tool, and a series of laboratory tests were performed to assess physical and mechanical characteristics. The strength results indicate a decreasing trend as the CR content in the GSB increases. Specifically, in abrasion tests, the natural material showed an average result of 30.86%, while the mixes with 10% and 15% CR exceeded the maximum limit (50%), achieving results of 59.24% and 53.98%, respectively. In terms of the California Bearing Ratio (CBR), only the natural samples compacted at maximum energy exceeded the minimum requirements for low and medium traffic levels (30%). The highest CBR value for samples containing CR was 5%, whereas the natural GSB reached a maximum CBR of 33%. A similar trend is observed in environmental outcomes, with increases of up to 17% in abiotic depletion for the sample with 15% CR. Overall, the environmental analysis suggests that incorporating CR into the GSB could lead to an increase in various environmental impacts.

Durability and Recycling of Rubber Concrete

The addition of crumb rubber particles causes a decrease in the compressive strength of concrete. This is particularly observed beyond 3.6% crumb rubber addition with respect to the total weight of the aggregates. The accelerated carbonation also indicates an increase in the CO2 ingress, which is partially due to the low quality of the interface rubber particles-cementitious matrix. On the other hand, the water sealant properties, the chloride penetration resistance and the resistance to freeze and thaw exhibit an increase. This latter feature is mainly due to the implemented ductility of the crumb rubber concrete, which can better adapt to the thermal stress that arises during the freezing action. Furthermore, the addition of recycled crumb rubber up to 25% of the aggregate weight to concrete positively affect the mechanical as well as the durability performance.

Plasma Processing of Rubber Powder from End-of-Life Tires: Numerical Analysis and Experiment

Tire recycling is becoming an increasingly important problem due to the growing number of end-of-life tires (ELTs). World-wide, ELTs account for more than 80 million tons. ELTs contribute to environmental pollution in the long term. They are flammable, toxic and non-biodegradable. At the same time, ELTs contain rubber, metal and textile cord, which are valuable raw materials. ELTs are buried in landfills, burned, crushed and restored. Most of these methods have a negative impact on the environment. From an environmental point of view, the most preferred ways to recycle tires are retreading and shredding. Rubber powder (RP) or crumb is mainly used for rubber pavers production, waterproofing, curbs, road slabs and various surfaces. An alternative method for RP processing, eliminating the disadvantages of the above approaches, is plasma gasification and pyrolysis. The paper presents a thermodynamic and kinetic analysis and an experiment on plasma processing of RP from worn tires to produce flammable gas. At a mass-average temperature of 1750 K, the yield of synthesis gas from plasma-air gasification of RP was 44.6% (hydrogen—19.1, carbon monoxide—25.5), and 95.6% of carbon was gasified. The experimental and calculated results satisfactorily agreed. It was found that plasma products from RP did not contain harmful impurities, either in calculations or experiments. Plasma gasification allows for recycling ELTs in an environmentally friendly way while also generating flammable gases that are valuable commodities. In this research, plasma technology was demonstrated to be effective for gasifying RP to produce flammable gas.

Studies on Concrete Replaced with Waste Tyre Rubber as Fine Aggregate

Concrete is one of the most extensively used construction material in the world and the mineral aggregates used to make the concrete are a finite resource, which is fast dwindling. On the other hand, Waste tyre treatment is now a serious global threat. Waste tyre dumping, disposal of these materials or burning these tyres cause serious environmental and health problems. The public, governments and industry are all greatly interested in green environment and engineering approaches towards better sustainable development. At the same time, these studies can help to make the environment clean and minimize waste. An emerging use is the production of concrete, in which rubber tyre particles Partially replace natural coarse aggregates. One of the solutions suggested is the use of tyre rubber aggregates as additive in cement based material. Waste tyres are cut into small pellets of size matching the nominal aggregate size and are used to replace the coarse aggregate used in concrete. For comparative analysis, concrete mix of M20 grade is prepared for various concrete mixes by varying percentage replacement of mineral coarse aggregates by 4, 6, and 8 rubber aggregates and the mechanical properties of rubber concrete are compared with that of conventional concrete. Different combinations of crumb rubber with traditional coarse aggregate were evaluated based on compression strength and flexural strength tests were conducted according to Indian Standard.

Effect of titanium dioxide as nanomaterials on mechanical and durability properties of rubberised concrete by applying RSM modelling and optimizations

The use of rubber aggregates derived from discarded rubber tyres in concrete is a pioneering approach to replacing natural aggregate (NA) and promoting sustainable building practices. Recycled aggregate in concrete serves the dual purpose of alleviating the accumulation of discarded rubber tyres on the planet and providing a more sustainable alternative to decreasing natural aggregate. Due to fact that the crumb rubber (CR) decreases the strength when used in concrete, incorporating titanium dioxide (TiO2) as a nanomaterial to counteract the decrease in strength of crumb rubber concrete is a potential solution. Response Surface Methodology was developed to generate sixteen RUNs which contains different mix design by providing two input parameters like TiO2 at 1%, 1.5%, and 2% by cement weight and CR at 10%, 20%, and 30% as substitutions for volume of sand. These mixtures underwent testing for 28 days to evaluate their mechanical, deformation, and durability properties. Moreover, the compressive strength, tensile strength, flexural strength and elastic modulus were recorded by 51.40 MPa, 4.47 MPa, 5.91 MPa, and 40.15 GPa when 1.5% TiO2 and 10% CR were added in rubberised concrete after 28 days respectively. Furthermore, the incorporation of TiO2 led to reduced drying shrinkage and sorptivity in rubberized concrete, especially with increased TiO2 content. The study highlights that TiO2 inclusion refines pore size and densifies the interface between cement matrix and aggregate in hardened rubberized concrete. This transformative effect results in rubberized concrete demonstrating a commendable compressive strength comparable to normal concrete.

Dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) under low-velocity impact: Effect of waste rubber incorporation and low temperatures

This study aims to explore the dynamic response of ultra-high performance engineered cementitious composites (UHP-ECC) incorporating waste crumb rubber (CR) at various temperatures, focusing on its potential to enhance the resilience and sustainability of civil infrastructures against low-velocity impacts. To date, the impact behaviour of UHP-ECC under low temperatures has rarely been explored. Firstly, natural river sand and waste tyre CR was utilized to prepare the UHP-ECC. Then, a series of mechanical tests, including compression test, flexural test and uniaxial tensile test were carried out to investigate the static mechanical properties of rubberised UHP-ECCs. In addition, the effects of different waste CR incorporations (0%, 5%, 10%, and 15%) and various temperatures (25 °C, −5 °C, −30 °C, −50 °C, −100 °C and −196 °C) were comprehensively investigated by low-velocity impact tests with constant impact energy. Lastly, the Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) model was introduced to evaluate the overall performance of UHP-ECC. It was found that the use of river sand and CR significantly enhanced the tensile ductility and impact toughness of UHP-ECC. Impact energy primarily dissipates through damage such as matrix crack initiation, propagation, and fibre pull-out/rupture within the specimen. Adding CR notably decreased stress fluctuations during impact at room temperature, facilitating steady state energy absorption. Moreover, the time to reach peak impact force decreased with decreasing temperature across all UHP-ECC groups. At room temperature during impact process, fibre failure mode is dominated by pull-out failure, while lower temperatures lead to increased fibre rupture at the cracking surface. In low-temperature conditions, the impact response of rubberised UHP-ECC necessitates a comprehensive consideration of the synergistic effects, including material contraction, fibre bridging capacity, rubber phase transition, and water freezing.

Secondary degradation of bio-oil degraded crumb rubber and preparation of stable degraded crumb rubber modified asphalt

Using bio-oil to desulfurize and degrade crumb rubber (CR) significantly enhances the compatibility between CR and asphalt, improving the workability of CR-modified asphalt and providing environmental and economic benefits. However, the secondary degradation of bio-oil degraded crumb rubber (ODR) in asphalt hinders the stability of ODR-modified asphalt. To optimize the mechanical performance of ODR-modified asphalt, the secondary degradation behaviors of ODR were investigated. The degree of CR degradation was determined by solubility testing, while the rheological properties and chemical structures of ODR-modified asphalt were characterized through rotational viscometer, dynamic shear rheometer, bending beam rheometer, and Fourier transform infrared spectrometer. The processes for preparing stable ODR modifier and ODR-modified asphalt were proposed to mitigate the damage caused by bio-oil and degraded CR to the high temperature mechanical properties of asphalt. The results show that at lower processing temperatures for ODR-modified asphalt, the volatilization of light components is predominant, while higher processing temperatures prompt secondary degradation of ODR. By stirring at 280°C for 2 hours to acquire moderately degraded CR, and then concentrating it at 220°C for 2 hours, a stable ODR less susceptible to secondary degradation can be obtained. The workability, temperature sensitivity, and low temperature cracking resistance of stable ODR-modified asphalt improve significantly. The reduction of ester group and increase in aromaticity restore the high temperature deformation resistance of ODR-modified asphalt. Further, the inclusion of composite SBS extends the range of rheological properties in ODR-modified asphalt, bolstering the application potential of ODR in asphalt pavement.

Mitigating microplastic stress on peanuts: The role of biochar-based synthetic community in the preservation of soil physicochemical properties and microbial diversity

Tire-derived rubber crumbs (RC), as a new type of microplastics (MPs), harms both the environment and human health. Excessive use of plastic, the decomposition of which generates microplastic particles, in current agricultural practices poses a significant threat to the sustainability of agricultural ecosystems, worldwide food security and human health. In this study, the application of biochar, a carbon-rich material, to soil was explored, especially in the evaluation of synthetic biochar-based community (SynCom) to alleviate RC-MP-induced stress on plant growth and soil physicochemical properties and soil microbial communities in peanuts. The results revealed that RC-MPs significantly reduced peanut shoot dry weight, root vigor, nodule quantity, plant enzyme activity, soil urease and dehydrogenase activity, as well as soil available potassium, and bacterial abundance. Moreover, the study led to the identification highly effective plant growth-promoting rhizobacteria (PGPR) from the peanut rhizosphere, which were then integrated into a SynCom and immobilized within biochar. Application of biochar-based SynCom in RC-MPs contaminated soil significantly increased peanut biomass, root vigor, nodule number, and antioxidant enzyme activity, alongside enhancing soil enzyme activity and rhizosphere bacterial abundance. Interestingly, under high-dose RC-MPs treatment, the relative abundance of rhizosphere bacteria decreased significantly, but their diversity increased significantly and exhibited distinct clustering phenomenon. In summary, the investigated biochar-based SynCom proved to be a potential soil amendment to mitigate the deleterious effects of RC-MPs on peanuts and preserve soil microbial functionality. This presents a promising solution to the challenges posed by contaminated soil, offering new avenues for remediation.

Analysis on the rheological behavior, microstructure and storage stability between crumb rubber of desulfurization and depolymerization and asphalt

The compatibility of crumb rubber (CR) modified asphalt restricts its application in pavement engineering. In this study, desulfurized (DS) and depolymerized (DP) CR-modified asphalts (CRMA) were prepared, and molecular models were constructed using molecular dynamics (MD). To analyze the effect of desulfurization and depolymerization on CRMA compatibility, rheological properties, storage stability, and morphological characteristics of CRMA, DSCRMA, and DPCRMA were determined and characterized. The interaction mechanism between CR and asphalt was characterized using indicators including binding energy and diffusion coefficient. Dynamic Shear Rheometer (DSR) results showed that desulfurization and depolymerization significantly improved the high-temperature rutting resistance of CR modified asphalt. Storage stability results indicated a softening point difference of 2.1°C for DSCRMA, meeting the standard of less than 2.5°C. Scanning Electron Microscopy (SEM) revealed a decrease in the size of DSCR particles and an increase in roughness and the number of pores. Fluorescence microscopy observed better dispersion of DSCR particles in asphalt, which was consistent with SEM results. MD results indicated an increase in binding energy between DSCR and light components, while diffusion motion was constrained. The interaction capability of DPCR decreased, possibly due to uneven depolymerization accumulation. The study revealed that desulfurization significantly enhances CRMA compatibility, while the degree of CR depolymerization warrants further investigation into its effects on asphalt.

Mechanical Performance of Steel-Fiber-Incorporated Rubberized Concrete for Rigid Pavement Applications

Sustainable solutions are required to mitigate waste tire accumulation. Using rubberized concrete (RuC) in rigid pavements is a viable and relatively environmentally friendly strategy for partially replacing fine/coarse aggregates with crumb rubber. However, crumb rubber affects the mechanical properties of concrete. Although RuC is more flexible (ideal for road pavements) than conventional concrete, its strength is lower than that of the standard concrete used in rigid pavements. Consequently, the crumb rubber generated from discarded tires cannot be used sustainably. The primary objective of this study was to characterize RuC mixed with manufactured steel fibers to improve the strength of the mixture. Fine aggregates (sand) were partially substituted with various proportions (10%, 20%, and 40%) of crumb rubber (size:1.70–2.36 mm) while incorporating 0.5% steel fibers (by volume). The compressive strength, splitting tensile strength, and flexural strength of the concrete deteriorated with increasing rubber content, consistent with the previously reported results. However, steel fiber incorporation improved the mechanical behavior of RuC, thus enhancing the compressive strength, splitting tensile strength, and flexural strength of the pavement structure. The developed steel-fiber-incorporated RuC design enhances the usability and economic value of RuC as well as minimizes the adverse environmental impact of concrete pavement technology.

Pavement Binder Course Optimization

The main objective of this study is to design the asphalt pavement structure for the Alkut-Mayssan highway in Iraq as a case study by using PCASE application to determine the necessary thickness of CR-modified asphaltic layers. Additionally, Marshall tests were used to investigate the effect of the dry process crumb rubber modifier on the thickness of the binder coarse layer based on various variables, such as the crumb rubber modifier with different content (1, 2, 3, 4, 5)% and sizes (0.3mm, 2.36mm , 4.75mm, and mix gradation). The test results show that while pavement thickness reduced as crumb rubber gradation increases, MR values increase. Additionally, as compared to the control mixture, the addition of 1% of CR in various gradations could decrease the thickness of the asphalt binder layer.

Performance study of SBS/CRMA with different composite crumb rubber particle size ratios

Different crumb rubber (CR) particle sizes affect asphalt performance differently. To improve the performance of CR in SBS/CR composite modified asphalt (SBS/CRMA) and to study the enhancement of SBS/CRMA performance with varying ratios of composite CR particle sizes. This study employed three different configurations of SBS/CRMA composite ratios. Several tests and analyses were conducted, Brookfield viscosity measurements, conventional performance tests, storage stability, high- and low-temperature rheology, LAS, Fourier transform infrared spectroscopy (FTIR) and fluorescence microscopy (FM) analysis. The results indicated that, in the composite CR particle size ratio, a finer particle size of CR demonstrated more significant benefits in improving the high- and low-temperature performance of asphalt. However, with aging, the role of a coarse particle size of CR gradually became more prominent. Furthermore, compared to a single CR mesh SBS/CRMA, the 3 S + 5R-6:2:2 composite CR particle size ratio of SBS/CRMA exhibited superior high- and low-temperature deformation and fatigue resistance. Considering the microscopic analysis, it can be observed that the fine particle size of CR exhibited superior compatibility and anti-aging performance compared to the coarse particle size. In the composite CR particle size ratio, adjusting the proportion of coarse and fine CR particle size will improve the performance of SBS/CRMA significantly. Contrary to common belief, it was not necessarily true that a higher ratio of coarse CR particles leads to a better modification effect in SBS/CRMA. On the other hand, the composite CR particle size ratio proved significantly advantageous, thereby providing valuable guidance for enhancing the performance of SBS/CRMA.

An Experimental Study on Self Compacting Concrete with Partial Replacement of Cement by Silica Fume and Crumb Rubber

Abstract: Self-compacting concrete (SCC) is a type of concrete that can flow and consolidate under its own weight without the need for vibration. SCC has many advantages such as improved workability, durability, surface quality, and reduced noise and labour. However, SCC also requires a high amount of cement and fine materials, which increases the cost and environmental impact of concrete production. Therefore, the use of supplementary cementitious materials such as silica fume and crumb rubber is beneficial to reduce the cement content and enhance the properties of SCC. This study aims to explore the effects of mixing silica fume and crumb rubber on the fresh and hardened properties of SCC. This involves the preparation of various concrete mixes with different percentages of cement replaced by silica fume and crumb rubber. Through a series of experiments, we evaluate the fresh and hardened properties of the SCC mixes, fresh properties such as workability, passing ability, and filling ability, while hardened properties including compressive strength, tensile strength, and flexural strength. The result obtained from these tests are compared with conventional concrete of M30 grade od concrete specimens. Hence the use of silica fume and crumb rubber leads to reduction in cement quantity for construction purpose and its use should be promoted for better performance as well as environmental sustainability.

Effect of the reclaiming degree of catalytic pre-desulfurization recycled crumb rubber on the properties of modified asphalt

The application of crumb rubber (CR) as an asphalt modifier in flexible pavements is an effective way to achieve sustainable utilisation. The performance of crumb rubber modified asphalt (CRMA) can be improved by pretreatment of CR to make it desulfurized to a certain extent. This study aims to determine the optimal regeneration degree of CR to obtain CRMA with better performance. Recycled crumb rubber (RCR) was prepared by catalytic regeneration at low temperatures and used to prepare recycled crumb rubber-modified asphalt (RCRMA). Furthermore, the characteristics of RCR with different regeneration degree and the performance of RCRMA were investigated to determine the reasonable range of regeneration degree. The results showed that solubility was a reliable indicator of the degree of regeneration of RCR and that the solubility of RCR was positively correlated with its regeneration degree. The higher the degree of RCR regeneration, the lower the molecular weight, the more uniform the distribution, and the larger the surface structure. The low-temperature performance, fatigue resistance, and construction workability of the RCRMA were better than those of the CRMA. When the solubility of RCR was greater than 30%, the compatibility and storage stability of RCRMA were significantly improved. As the solubility of RCR increases, the high-temperature performance of RCRMA decreases; however, as long as the solubility of RCR does not exceed 60%, the decrease in the high-temperature performance of RCRMA is very small. According to a comprehensive analysis, the solubility of RCR should be maintained at 30–60%.

Experimental Investigations of Bituminous Concrete Using Dissimilar Trash Which Improve the Results

Abstract: Bituminous mixture is an admixture of coarse aggregate, fine aggregate and fill. CRMB is based on a unique technology that permits homogeneity. CRMB is suited for use in heavy load traffic lanes, air fields. In this study, Crumb Rubber Modified Bitumen (CRMB-60) blended with normal asphalt binder VG-30 with various different percentages of crumb rubber in different proportions with constant optimum binder content i.e. 5% which shows improved characteristics when compared with regular bitumen. The cost for Bituminous course for CRMB-60 came out to be Rs 68.23 Lacs per Km which was 20.81% economical than the bituminous work done by normal VG- 30 bitumen. The Marshall Mix design using CRMB 55 with 0.04 % Zycosoil chemical, reflects the significant rise in stability, unit weight and flow values for better compaction and enhancing the workability conditions.

The Effect of Different Proportions of Waste Rubber Substitution on Alkali-Silica Reaction and Mechanical Properties in Mortars

This study investigates the alkali-silica reaction (ASR) and mechanical properties of mortars containing crumb and powder rubber instead of river sand. In this regard, mortars were produced using waste rubber whose ratios in the mixture are 0%, 3%, 6%, 9%, 12%, 15%, 18%, and 21%. ASR expansion, compressive and flexural strength tests were conducted on the samples. ASR measurements were performed on days 3, 7, 14, 21, and 28. Besides, at the end of the ASR experiment, the microstructures of the mortars were examined using scanning electron microscope (SEM) images. Examining the results of this study reveals that the use of waste rubber in rising portions in the mortars led to an increase in the ASR expansions of the mortars. The study shows that the ASR expansions of the mortar samples that have 9% and 15% waste rubber replacement are comparatively higher than the other mortar samples. Furthermore, the results of the SEM analysis verified this finding. The study demonstrates that 3% of waste rubber mortar samples have the highest compressive and flexural strengths. On the other side, the ASR expansion of the mortars with 3% substituted waste rubber was considerably low compared to other mortars containing waste rubber. These findings (ASR, compressive and flexural strength tests results) show that using 3% waste rubber is ideal for producing mortars and supports a sustainable production approach in the sector.