Tire Crumb Research Articles

Synergetic Effects of Waste Engine Oil and Crumb Tyre Rubber on Bitumen Modification

Bitumen is a widely used road infrastructure material exhibiting black color and sticky consistency and is known for its versatile use and thermoplastic nature. In recent years, predicting road life has been arduous due to increasing traffic, global warming, and ever-changing stresses on pavements. Meanwhile, a large amount of waste engine oil (WEO) and vehicle tyres from various automobiles is disposed of into the atmosphere as hazardous waste. Relatedly, heavy metals and the huge capital involved in the sustainable treatment of these materials have been challenging. Therefore, this study aims to analyze modified bitumen using (WEO) in combination with waste crumb tyre rubber (CTR), thus reducing virgin bitumen (VB) use and making bitumen a sustainable material. During the characterization of modified bitumen, the following WEO concentrations were utilized: 3%, 5%, 7%, and 9%, and the following CTR concentrations: 5%, 7%, 9%, 12%, and 15%. The properties of modified and virgin bitumen were compared. It has been found that the blend of 5% CTR and 9% WEO exhibit the highest penetration value and the lowest softening temperature of all the samples examined. As a result, this mixture can be used to reduce the excessive brittleness of bitumen to a greater extent. Moreover, the flash and fire point values have increased after modification, while the ductility and specific gravity values have decreased. In summary, the modified bitumen has shown promising results regarding physical changes in bitumen.

Anti-deformation performance of asphalt modified by carbon black extracted from waste cooking oil pyrolysis waste tires rubber

As a promising renewable resource, waste tire rubber powder has been utilized to enhance asphalt performance but it has compatibility concerns with matrix asphalt. To solve the phase separation between crumb tire rubber (CTR) and asphalt, waste cooking oil (WCO) has been successfully employed as the solvent to desulfurize crumb rubber. However, about 30 % of carbon black is wrapped in crumb rubber, which has a high recycling value. The cross-linking network structure of the crumb rubber can be loosened by waste cooking oil, and the carbon black will gradually peel off. This study desulfurizes crumb rubber with waste cooking oil at 180 ℃, and the carbon black produced by the evolution of rubber structure was separated by Soxhlet extraction. The rubber-cracked carbon black (RCCB) and the industrial carbon black N330 were added to asphalt, and the impact of the two different carbon black on the anti-deformation of asphalt was analyzed by dynamic shear rheometer (DSR). The results indicated that at the same dosage of 5 %, the carbon black separated from rubber will weaken the deformation resistance of asphalt at high temperatures, rather than improving it like N330 produced in the industry.

Evaluation of sorbent amendments used with stormwater management practices to remove contaminants: Impacts of rainfall intensity and antecedent dry periods

For a comprehensive evaluation of the suitability and efficiency of soil amendments in bioretention systems, it is crucial to investigate the capability of amendments for simultaneously serving three important functions under intermittent and variable flow conditions: removing a wide range of contaminants, supporting plant health, and maintaining media infiltration rate. However, most studies have not considered these important factors and conditions simultaneously, which may overestimate or underestimate the bioretention performance. In this study, a long-term vegetated column study was conducted to investigate the ability of various sorbent amendments– coconut coir fiber (CCF), blast furnace slag (BFS), and waste tire crumb rubber (WTCR) –for removal of metals, nutrients, and polycyclic aromatic hydrocarbons (PAHs) from stormwater. The experiments were performed under intermittent flow conditions considering different runoff intensities and antecedent dry periods (ADP). The long-term effect of bioretention usage on plant health and media infiltration rate was also investigated.All amended and unamended columns were able to remove >99 % of influent metals, except Cu, over the 7-month experiment period with different rain intensities and dry periods; modest effluent Cu concentrations occurred with higher rainfall. The performance of different media for removing PAHs such as naphthalene and acenaphthylene varied with the rain intensity. The BFS-amended media had high phosphate removal capacity (>90 %) under tested conditions. In all columns, nitrate removal was notably affected by changes in stormwater intensity and ADP, with high nitrate removal during heavy rainfall. Over the entire experiment, all media had good infiltration rate within the locally acceptable range (1–25 cm/h). The high iron and aluminum contents of BFS adversely affected the plant health in BFS-amended media. Overall, this study identifies the opportunities and challenges associated with the usage of bioretention amendments, and improves awareness among bioretention designers to consider seasonal effect on the performance of bioretention systems.

Ingestion of car tire crumb rubber and uptake of associated chemicals by lumpfish (Cyclopterus lumpus)

Car tire rubber constitutes one of the largest fractions of microplastics emissions to the environment. The two main emission sources are tire wear particles (TWPs) formed through abrasion during driving and runoff of crumb rubber (CR) granulate produced from end-of-life tires that is used as infill on artificial sports fields. Both tire wear particles and crumb rubber contain a complex mixture of metal and organic chemical additives, and exposure to both the particulate forms and their leachates can cause adverse effects in aquatic species. An understanding of the exposure pathways and mechanisms of toxicity are, however, scarce. While the most abundant metals and organic chemicals in car tire rubber have multiple other applications, para-phenylenediamines (PDs) are primarily used as rubber antioxidants and were recently shown to cause negative effects in aquatic organisms. The present study investigated the responses of the marine lumpfish (Cyclopterus lumpus) to crumb rubber exposure in a controlled feeding experiment. Juvenile fish were offered crumb rubber particles with their feed for 1 week, followed by 2 weeks of depuration. Crumb rubber particle ingestion occurred in >75% of exposed individuals, with a maximum of 84 particles observed in one specimen. Gastrointestinal tract retention times varied, with some organisms having no crumb rubber particles and others still containing up to 33 crumb rubber particles at the end of the experiment. Blood samples were analyzed for metals and organic chemicals, with ICP-MS analysis revealing there was no uptake of metals by the exposed fish. Interestingly, high resolution GC-MS analysis indicated that uptake of PDs into lumpfish blood was proportionate to the number of ingested CR particles. Three of the PDs found in blood were the same as those identified in the additive mixture Vulkanox3100. N-(1,3-dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD) was the most concentrated PD in both the crumb rubber and lumpfish blood. The transformation product 6PPD-quinone was detected in the rubber material, but not in the blood. This study demonstrates that PDs are specific and bioavailable chemicals in car tire rubber that have the potential to serve as biomarkers of recent exposure to tire chemicals, where simple blood samples could be used to assess recent tire chemical exposure in vertebrates, including humans.

Assessment of Mechanical Characteristics of Crushed Rock Substituted with Tyre Crumb for the Application of Road Base or Subbase Layers of Road Pavement

Assessment of Mechanical Characteristics of Crushed Rock Substituted with Tyre Crumb for the Application of Road Base or Subbase Layers of Road Pavement

Effects of Tire Crumb Rubber and Steel Fiber on Punching Shear Behavior of Two-way Alkali-activated Concrete Flat Slabs

As a result of the rapid increase in the demand for transportation vehicles recently, the accumulation of waste tires causes environmental problems. One of the methods that can contribute to the reduction of this environmental problem is the recycling of waste tires as a construction material in aggregate form. This research investigated the impacts of waste tire crumb rubber with/out steel fiber (SF) on the two-way punching-shear behavior alkali-activated concrete (AAC) flat slabs and performed center point load tests. In the study, one-type of SF and two kinds of scrap tire waste i.e., crumb rubber (CR) and tire particles, were used on the producing of rubberized AAC slabs obtained by 100% as binder made of ground-granulated blast furnace slag (GGBFS). Also, while both fine crumb rubber (FCR) and coarse crumb rubber (CCR) were used together in the AAC slabs, tire crumb rubber (TCR) was used alone at the same proportion. Additionally, the fine aggregate was substituted with 10% and 15% FCR and CCR, and coarse aggregate was substituted with TCR in the same proportions. Additionally, AAC slabs with recycled tire rubber (RTR) were produced as fibrous and non-fibrous using 1% by volume hook-end SF. In total, nine AAC slabs with sizes of 50 x 50 x 6 cm3 were manufactured for the study. Experimental data showed that the inclusion of RTR only slightly reduced the punching shear strength of AAC slabs and the punching shear strength of the slabs increased when SF was added to the mixtures containing RTR.

Properties of sustainable self-compacted concrete with recycled concrete and waste tire crumb rubber aggregates

The concrete building industry has to adhere to stringent sustainability standards. In previous investigations, the utilization of recycled concrete aggregates (RCA) from construction and demolition waste (CDW) or crumb rubber (CR) from waste tires in producing sustainable self-compacted concrete (SCC) was well studied; however, the combined effect of RCA and CR on the performance of SCC is scarce. Therefore, the main purpose of this study is to evaluate the feasibility of developing SCC mixtures containing both RCA and CR and their influence on the performance of SCC. Three distinct series of SCC mixes were designed so that the water-to-binder ratio and total binder content were kept at 0.32 and 505 kg/m3. In the first series, the effect of RCA content (0%, 50%, and 100%) in place of natural coarse aggregate (NCA) on the performance of SCC mixtures was studied. Moreover, the effect of various CR contents (0%, 10%, 20%, 30%, and 40%) as a sand substitution and 50% RCA was investigated in the second series. In the third series, the influence of CR inclusion and 100% RCA was utilized to promote the sustainability of SCC. The fresh behavior of the mixtures was assessed by measuring followability, viscosity, and segregation resistance. Density, water absorption, and apparent porosity for all mixes were also examined. The mechanical properties were assessed for compressive, splitting tensile, and flexural strengths. The findings show that the inclusion of RCA and CR has an adverse impact on the fresh, physical, and mechanical properties of SCC, excluding segregation resistance. However, it is possible to produce a SCC using 100% RCA and 40% CR with a slump flow diameter of 605 (SF1 class) and a compressive strength of greater than 31 MPa, which is applicable for structural applications. Moreover, the ACI and Euro code CEB-FIP proposed models can predict the mechanical properties of the developed SCC made with recycled materials. This research could contribute to a more sustainable SCC by substituting recycled materials for natural aggregates.

Hybrid viscoelastic damper using natural rubber compound, waste of rubber tire crumb with various compacted sands (iron sand, natural sand, and silica sand) to increase damping property for non-engineered buildings

To reduce lateral deformation due to earthquake shake has been carried out by strengthening techniques. Such techniques require additional structural elements such as bracing or shear wall, if not applying additional new materials on beams or columns such as CFRP. This study focuses on the formation of the hybrid rubber dampers from materials such as natural rubber compound (NRC), waste of rubber tire crumb (WRTC), compacted natural sand, iron sand, and silica sand. The main goal of this research is to investigate the dynamic properties of hybrid materials of compacted various sands encapsuled with the NRC and WRTC compound. Nonetheless, the mechanical properties of rubber, such as tensile strength and modulus of elasticity, were also tested. In this research, the specimens were in the form of a square block of 100 x 100 mm2 base and 25 mm thickness and consisted of two types of specimens for reference i.e., fully natural rubber compound (NRC) and blended NRC with 25% by volume of the WRTC, namely MRTC. Furthermore, other three types of hybrid viscoelastic dampers (HVD) were also provided i.e., 1) compacted natural sand, 2) compacted iron sand, and 3) compacted silica sand, which were all wrapped with WRTC in a proportion of 3:4 by volume. The results show that the addition of the MRTC reduces the tensile strength and elastic modulus in comparison to the NRC but increases the damping properties. Moreover, the elaboration of compacted natural sand, iron sand, and silica sand in the HVD also shows an increase in the damping properties up to 200%.

Assessing children’s potential exposures to harmful metals in tire crumb rubber by accelerated photodegradation weathering

Whether a tire crumb rubber (TCR) playground would expose children to potentially harmful chemicals such as heavy metals is an open question. The released metals available for pickup on the surface of TCR tiles was studied by accelerated 2-year aging of the TCRs in the NIST-SPHERE (National Institute of Standards and Technology Simulated Photodegradation via High Energy Radiant Exposure). The dermal contact was mimicked by a method of composite surface wiping from US Environmental Protection Agency throughout the weathering process. The surface release of ten most concerned harmful metals (Be, Cr, Cu, As, Se, Cd, Sb, Ba, Tl, Pb) was monitored through the course of aging. The cumulative release of Cu, As, Tl, and Sb reached potentially harmful levels at various times within 3 years, although only Cr was found at a harmful level on the surface of the tiles. Taking the cleansing effect of precipitation or periodic cleansing with rain into account, TCR playgrounds may still be safe for use.

Durability assessment of sustainable metakaolin based high strength concrete incorporating crumb tire rubber

Durability assessment of sustainable metakaolin based high strength concrete incorporating crumb tire rubber

Laboratory testing and field application of devulcanized rubber/SBS composite modified asphalt

Styrene-butadiene-styrene copolymer (SBS) and recycled tire rubber are the typical polymers for asphalt modification. The dispersion of crumb tire rubber (CTR) dominates the composite effect of rubberized asphalt. And the multiscale of CTR in mixtures always challenges the design and construction of asphalt mixtures. The multiscale dispersion of CTR can be controlled by pre-devulcanization. In this study, lightly devulcanized rubber (LDR) with various dispersive scales in asphalt from microns to dozens of microns, and deeply devulcanized rubber (DDR) with micro-nano scales were prepared and analyzed, respectively. The devulcanized rubber (DR) was further compounded with SBS to prepare composite modified asphalt. The influences of rubber content on the structure and properties of modified asphalt and mixtures were investigated, and the dispersive structure model of asphalt mixture was also established. Furthermore, a high viscoelastic rubberized asphalt was prepared with 4% SBS and 20% DDR in the field plant and paved in a field project, a new first-grade national highway. The results showed that the devulcanization of CTR can help the dispersion of CTR in asphalt by improving the compatibility among CTR, SBS, and asphalt. And the dispersive scale and the content of DR can affect the binder content, high and low temperature performance of asphalt mixtures. The field project showed that the high viscoelastic rubberized asphalt exhibited similar mix design and construction process but better high and low temperature performance compared to SBS modified asphalt.

INVESTIGATION OF THE MECHANICAL PERFORMANCE OF STONE MASTIC ASPHALT MIXTURES MODIFIED BY RECYCLED WASTE POLYMERS

The usage of polymer-modified asphalt binders has increased as a result of the significant increase in the number of conventional cars operating on Iraqi roads in recent years. This has resulted in increased strains being placed on pavement structures and materials. Global exploration has focused on the development of stabilizing Stone Mastic Asphalt mixtures for improved pavement behavior. Numerous effective efforts were made to stabilize stone mastic asphalt mixes with polymers and fibers. Iraq produces a considerable amount of waste polymer materials each year. Usually, they are sent to landfills for disposal. These wastes are dumped, occupying a sizable portion of landfill space and creating various serious environmental issues. The study focuses on how waste polymer additions, such as recycled plastic bottles, shopping boxes, and tire crumb rubber, affect the mechanical performance and durability of stone mastic asphalt mixtures. The mechanical performance attributes were assessed. It is evident from the findings that the drain-down amounts were within the permissible requirement range. The findings also showed that the indirect tensile strength, Marshall Stability, moisture damage resistance, and resistance for permanent deformation of stone mastic asphalt mixtures have all increased as a result of the use of waste polymer components. The recycled polymer-modified mixes are the combinations that are most resistant to rutting, according to the results of the repeated load axial creep tests. Iraq may have new options to employ the significant volumes of recycled polymers that are becoming accessible as a result of recycling waste polymers.

Comprehensive study on the degradation progress of crumb tire rubber during the preparation of terminal blended rubberized asphalt binder

Terminal blended rubberized asphalt binder (TB) technology, which blends crumb tire rubber (CR) with asphalt under high interaction conditions, offers a promising waste tire recycling solution for pavement construction. By precisely controlling the degradation progress of CR, it is possible to prepare TB with specific property requirements. However, the degradation progress of CR and its impact on TB property during the TB preparation process remain ambiguous. This hinders the potential for efficient preparation of TB with specific property requirements. This study aims to understand the degradation progress of TB by analyzing binders, soluble fractions, and insoluble fractions obtained at various interaction durations. Microscopic analysis characterizes the chemical composition, morphology, and molecular weight distribution of insoluble and soluble fractions, while macroscopic analysis evaluates the solubility, viscosity, compatibility, and mechanical properties of binders. The results reveal that the degradation of CR during the preparation of TB consists of a desulfurization reaction, depolymerization reaction, and release behavior (carbon black and fillers). Depending on the degradation progress of CR, the interaction process can be classified into three stages: initial (desulfurization reaction dominant stage), middle (depolymerization reaction dominant stage), and last (release behavior dominant stage). The desulfurization reaction of CR is almost completed in the initial stage. The depolymerization reactions and release behavior occur throughout the process. The most pronounced depolymerization reactions occur in the initial stage for natural rubber and in the middle stage for synthetic rubber, while the most significant release behavior occurs in the last stage. Accordingly, in the initial stage, TB shows a rapid evolution in macro properties due to the significant development of degradation reactions, specifically, the notable improvement in viscosity, compatibility, and low-temperature properties, as well as the substantial deterioration in high-temperature properties. In the middle stage, the degradation reaction develops further but slower, with TB exhibits a further but slower evolution in macro properties. In the last stage, the degradation reaction is almost completed, and TB shows a gradual stabilization of macro properties. The findings are expected to achieve precise control of CR degradation progression, which offers the possibility of efficient preparation of TB with specific properties, thus advancing the application of CR in pavement engineering.

Use of Biomass and Waste Tires to Facilitate the Use of HDPE in Coking

This work examines the role of various wastes such as pine sawdust, tire crumbs, and hydrochar from pine sawdust in reducing the deleterious impact of high-density polyethylene (HDPE) on coke contraction during coking. Contraction assessed using the Koppers-INCAR test was used as an indirect measurement of coking pressure. The Koppers-INCAR contraction of ternary blends containing coal, HDPE, and one of the other additives was tested together with their devolatilization in a thermobalance. The existence of synergism between the additives was examined to determine whether there were both positive and negative interactions between HDPE and other additives. The temperature corresponding to a 2% conversion increased with the use of additives; this was related to the degree of dangerousness of the blends. In addition, the effect of the additives on coal fluidity and coke quality was tested.

Development and Study of a Carbon–Mineral Catalyst Based on Natural Clay and Tire Crumb for the Oxidative Decomposition of Nonionic Surfactants with Hydrogen Peroxide in Wastewater

Development and Study of a Carbon–Mineral Catalyst Based on Natural Clay and Tire Crumb for the Oxidative Decomposition of Nonionic Surfactants with Hydrogen Peroxide in Wastewater

Excellent low temperature performance for modified asphalt by finely dispersed sidewall tire rubber

Low temperature performance of rubber asphalt in cold regions still has challenges for facing cracking. In this study, the modified asphalt by finely dispersed degraded sidewall tire rubber (STR) was prepared to study its low temperature performance by bending beam rheometer, differential scanning calorimetry, Fraass brittleness temperature and ductility. Results showed that low test temperature and Fraass brittleness temperature of STR-modified asphalt could be down to −24.0 °C, both of which were better than that of current crumb tire rubber modified asphalt. The ductility at temperature of 5 °C was 22.3 cm, which was higher than those of other tire section rubber modified asphalt, such as tread tire rubber modified asphalt (TTRMA, 19.8 cm) and bead tire rubber-modified asphalt (BTRMA, 15.6 cm). This was owing to that STR-modified asphalt had low glass transition temperature (Tg) of −33.1 °C, which was lower than those of TTRMA (−32.9 °C) and BTRMA (−31.2 °C). Modification mechanism proposed that flexible butadiene rubber (Tg of −110.0 °C) in STR strongly promoted the relaxation of rubber molecular segments through molecular orientation and conformation switching when suffering stress concentration. Accordingly, the STR-modified asphalt had excellent low temperature performance, and could be practically used for flexible pavement in cold region.

Development and Investigation of Carbon-Mineral Catalyst Based on Natural Clay and Tire Crush for Oxidative Decomposition of Nonionic Surfactants by Hydrogen Peroxide in Wastewater

Samples of a carbon-mineral catalyst based on natural clay and tire crumb for the reaction of oxidative decomposition of nonionic surfactants by hydrogen peroxide in wastewater have been developed and studied. The iron content in the samples varied in the range of 2.3–3.9 wt %. The effect of sample pyrolysis temperature in the range of 350–800°С on characteristics, the number and type of acid sites on the surface, and the ζ (zeta) potential of colloidal systems based on prepared samples was studied. Using model solutions under static and dynamic conditions, the effect of sample pyrolysis temperature on catalytic properties in the reaction of oxidative decomposition of H2O2 and nonionic surfactant (NS) nonoxynols N-9 by hydrogen peroxide was studied. The best result in the oxidation of nonoxynols N-9 with hydrogen peroxide was obtained in the presence of a carbon-mineral catalyst sample calcined at 650°C.

The effect of pre‐pyrolysis chemical treatment of waste tyre rubber crumbs: comparison between pre‐treated and conventional waste tyre‐derived oil

AbstractBACKGROUNDPyrolysis process is one of the most effective recycling methods due to its ability to recover products like gas, oil and char with oil being the major/important product. The shortcomings of waste tyre‐derived oil from the conventional pyrolysis process are that the oil contains high amounts of sulfur and polycyclic aromatic hydrocarbons (PAHs) and has a pungent smell, which makes it difficult to utilize further. The aim of this study is to investigate the effect of chemical pre‐treated waste tyre rubber crumb‐derived oil versus conventional waste tyre oil. The instrumentation utilized in this study was to solely investigate the shortcomings of waste tyre pyrolysis (high sulfur and PAH content and also high temperature required for waste tyre pyrolysis).RESULTSThe results showed a reduction in amounts of both sulfur and PAHs in treated waste tyre‐derived oil by about 83% and 77% respectively. Also, there was a reduction in initial pyrolysis temperature for the treated waste tyre crumb as compared to untreated waste tyre crumb: a temperature range of 96–115 °C for treated waste tyre crumbs as compared to 300–400 °C for untreated waste tyre crumbs.CONCLUSIONSThe success of this study means the production of quality oil at a low temperature with lower amounts of PAHs and sulfur and less odour, plus the possibilities of it being used as a petroleum fuel or for extraction of important compounds like benzene, toluene, xylene, limonene and C12–C20 acids. © 2023 The Authors. Journal of Chemical Technology and Biotechnology published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry (SCI).

Utilization of high contents of recycled tire crumb rubber in developing a modified-asphalt-rubber binder for road applications

Waste tires are generally mixed with asphalt materials to produce asphalt-rubber (AR) or rubberized asphalt through wet-, dry-, and terminal blending processes. However, the limitations such as long-term storage and stability issues of these special products have led to the need for advancing the AR technology capable of mitigating the production-related problems. Thus, the major objective of this research was to re-engineer AR in the form of a set of eighteen modified-asphalt-rubber (MAR) products comprising high contents of recycled tire crumb rubber (CR) through activation and pulverization. A set of MAR products was synthesized through different blending dosages, sequences, and material combinations. The material characterization techniques (attenuated total reflection-infrared spectroscopy and powder X-ray diffraction) revealed that the type of additives and the proportions of each material pose a significant effect on the physiochemical properties of MAR. It is noteworthy that this study emphasized the best use of CR emanating out of scrap tires in paving applications through incorporation of higher volumes (as large as 62%) in the preparation of MAR when compared to the conventional AR binder that currently includes about 15–20% CR by weight of the base asphalt binder. The fatigue performance of MAR-modified dense graded mix (MAR blended with natural aggregates) was compared to the conventional mix, which revealed that the MAR-modified dense graded product will have higher fatigue life by more than two times, and increased durability than the conventional mix. Practically, the MAR products can be used for instant application in pothole patching, rehabilitation, and new construction through dry-process technology by replacing a reasonable proportion of conventional aggregates in the asphalt mix. It is envisioned that the MAR binders will reduce the overall cost of pavement construction by utilizing the untreated (or unprocessed) CR in larger quantities by actively supporting the recycling mechanism and circular economy.

Experimental Study on Liquefaction Characteristics of Saturated Sands Mixed with Fly Ash and Tire Crumb Rubber

The liquefaction of saturated sandy soils during dynamic loading can inflict excessive damage on the structures, leading to significant human and economic losses. Recycling and reusing industrial waste materials may offer a sustainable and economic solution to this problem. This study investigates the influence of two waste materials, namely, recycled fly ash and tire crumb rubber, on the liquefaction characteristics of sand. For this purpose, loose and medium-dense triaxial specimens were prepared using sand–fly ash mixtures containing 0–40% of fly ash and sand–tire crumb rubber mixtures containing 0–30% of crumb rubber. The liquefaction characteristics of the specimens were examined through a series of stress-controlled, undrained, dynamic triaxial tests. The tests were conducted at 1 Hz loading frequency and under initial effective confining stresses of 50 and 100 kPa. The experimental results showed that, at a similar relative density, the liquefaction resistance of the sand–fly ash specimens decreased as the fly ash content (FA) increased up to about 20%; then, it slightly increased until FA reached 40%. Sand-only specimens showed greater liquefaction resistance than sand–fly ash specimens. The liquefaction resistance of the sand–tire crumb rubber specimens was enhanced by increasing the rubber content (RC) in the mixtures. It was found that the increasing liquefaction resistance of sand with the addition of tire crumb rubber was more noticeable under higher confining stresses.