Search Results (120)

Every year, a billion tires are discarded worldwide, with only a small percentage being recycled. This leads to significant environmental hazards, such as fire risks and improper disposal. Silty sand also presents technical challenges due to its poor shear strength, susceptibility to erosion, and low permeability. This study explores the incorporation of crumb rubber derived from waste tires into silty sand to enhance its mechanical properties. Crumb rubber particles of varying sizes (3–6 mm, 5–10 mm, and 10–20 mm) were mixed with silty sand at 0%, 3%, 6%, and 9% percentages, respectively. Triaxial compression tests of unconsolidated and consolidated undrained tests with cell pressures of 100, 300, and 500 kPa were conducted. The deviatoric stress, shear stress, and stiffness modulus were investigated. The results revealed that the addition of crumb rubber significantly increased the deviatoric and shear stresses, especially at particle sizes of 5–10 mm, with contents of 3%, 6%, and 9%. Additionally, the stiffness modulus was notably reduced in the mixture containing 6% crumb rubber tire. These findings suggest that incorporating crumb rubber tires into silty sand not only improves silty sand performance but also offers an environmentally sustainable approach to tire waste recycling, making it a viable strategy for silty sand stabilization in construction and geotechnical engineering performance. Full article

The production of ordinary Portland cement has had a significant environmental impact, leading to increased interest in sustainable alternatives. This comprehensive review thus explores the performance and applications of rubberized alkali-activated concrete (RuAAC), an innovative material combining alkali-activated concrete with crumb rubber (CR) from waste tires as a coarse/fine aggregate replacement. The study examined current research on the components, physical and mechanical properties, and seismic performance of RuAAC structures. Key findings revealed that CR addition enhances dynamic characteristics while reducing compressive strength by up to 63% at 50% CR replacement, though ductility improvements partially offset this reduction. Novel CR pretreatment methods, such as eggshell catalyzation, can enhance seismic resilience potential. While studies on the structural seismic performance of RuAAC are limited, relevant research on rubberized conventional concrete indicated several potential benefits, highlighting a critical gap in the current body of knowledge. Research on the behavior of RuAAC in full-scale structural elements and under seismic loading conditions remains notably lacking. By examining existing research and identifying crucial research gaps, this review provides a foundation for future investigations into the structural behavior and seismic response of RuAAC, potentially paving the way for its practical implementation in earthquake-resistant and sustainable construction. Full article

The article reports on the development of a fundamentally new, effective technology for recycling waste tires using the explosive-circulation technology method, which was implemented in industry at a working factory. The construction of an explosion-circulation reactor, in which tires are destroyed under the influence of an explosion, is described. The main technological stages of the reactor operation include the formation of a tire package with a height of about 2.4 m and a mass of up to 1000 kg; cooling the package by air turbo-cooling machine to a temperature of minus 70–80 °C; placing the package into the reactor; initiating the explosive charge; and removing the tire shedding products with a subsequent granulometric classification of the resulting rubber crumb. The resulting rubber crumb has good wettability, which eliminates the need for an additional technological stage of activating the crumb surface. This made it possible to successfully use the obtained rubber crumb to improve the characteristics of road construction bitumen, the hardness of which at −16 °C decreased from 217 to 161 MPa. Using atomic force microscopy (AFM), gas chromatography, mass spectrometry, GPC, and XPS, it was established that the good wettability of the crumbs is explained by the formation of molecules with polar groups (C-O, C=O, C(O)O, C-S, C-SO_x, Zn-S, O-Si(O)-O) on the crumb surface as a result of the explosion. Full article

This study explores the innovative use of recovered tire-derived aggregates in cement-based mortars to enhance thermal insulation and reduce environmental impact. The research addresses the pressing global challenge of managing end-of-life tires (ELTs), which are non-biodegradable and contribute significantly to waste management issues. By incorporating crumb rubber from recycled tires into mortars, this study investigates the feasibility of creating lightweight, thermally insulating mortars suitable for building repair and rehabilitation. The primary objective is to develop mortars that minimize structural load, decrease energy consumption in buildings, and promote the recycling of ELTs as a valuable resource. The study focuses on evaluating how varying crumb rubber content affects key properties such as workability, thermal conductivity, compressive strength, and fracture energy. Experimental tests were conducted to assess these properties, with the results indicating that mortars with up to 50% crumb rubber content exhibit improved thermal insulation and meet industry standards for non-structural repair applications. The methodology involved creating eight different mortar mixtures with varying proportions of crumb rubber particles (ranging from 0% to 100%). Each mixture was tested for physical and mechanical properties, including density, workability, air content, setting time, thermal conductivity, and strength. The experimental results showed that as the crumb rubber content increased, the thermal conductivity of the mortars decreased, indicating enhanced insulation properties. However, higher crumb rubber content led to reduced mechanical strength, highlighting the need for a balanced approach in material design. Key findings reveal that the air content of early-age mortar paste increases linearly with the crumb rubber replacement ratio, impacting the hardened behavior by concentrating stresses or facilitating the infiltration of damaging elements. The study also establishes relationships between mortar properties and crumb rubber content, contributing to the development of sustainable construction materials. The environmental benefits of recycling ELTs are emphasized, as this practice reduces the reliance on natural sand, a resource that is the second most consumed globally after water. This study underscores the viability of using crumb rubber from recycled tires in mortars for repair and rehabilitation purposes. The developed mortars, particularly those with 25% to 50% crumb rubber content, show promise as non-structural repair products, offering improved thermal insulation and reduced environmental impact. Full article

Railway track performance and durability face growing challenges from higher speeds, heavier axle loads, and changing environmental conditions. Crumb rubber-modified asphalt (CRMA) offers a sustainable solution by repurposing waste tires into a durable material for railway trackbeds, improving both performance and environmental impact. Following PRISMA-ScR guidelines, this scoping review synthesizes an extensive body of global research on the structural, mechanical, and environmental benefits of CRMA in railway trackbeds. A systematic literature search was conducted across major academic databases, covering studies published over several decades. Selection criteria focused on CRMA applications in railway trackbeds, using keywords such as “crumb rubber-modified asphalt”, “railway track vibration”, and “sustainable railway materials.” After rigorous screening and eligibility assessment, the most relevant peer-reviewed studies were included, emphasizing mechanical performance, durability, and environmental impact. Key findings indicate that CRMA effectively reduces ground vibrations, enhances load distribution, and lowers long-term maintenance costs while promoting sustainable waste management through tire recycling. However, challenges such as optimal mix design, potential emissions, and long-term bonding stability require further investigation. Additionally, the review was limited to English-language studies, potentially omitting relevant non-English research, and some reports were inaccessible during retrieval. This review maps critical research gaps, identifies key areas for future optimization, and highlights CRMA’s potential to advance resilient and eco-friendly railway infrastructure. Full article

Rubber materials enter aquatic environments by stormwater runoff via sources such as playground mulch, athletic fields, and roadway surfaces. Tire rubbers are considered plastics as they comprise a substantial portion of synthetic polymers. Rubber particles are complex and variable depending on the type, source, and age of rubber. In this study, zebrafish embryos and daphnids were exposed to nano-scale or micro-scale particles, or leachate from recycled rubber (RR), crumb rubber (CR), and cryo-milled tire tread (CMTT). Zebrafish embryos were evaluated for lethal and sub-lethal effects over a 120 h exposure, while daphnids were tested over a 48 h period. Nano-scale RR, CR, and CMTT particles elicited a hatch delay in zebrafish embryos with similar EC₅₀ values (1.3 × 10⁹–1.4 × 10⁹ particles/mL). Micro-scale particles did not elicit any significant effects in developing zebrafish. Nano-scale particles of all rubber materials significantly increased hatch delay compared to leachate, suggesting an adverse nanoparticle effect unexplained by chemical leaching alone, indicating tire particle-specific effects. Daphnia RR micro- and nanoparticle exposures resulted in mortality, with LC₅₀ values of 9.8 × 10⁵ microparticles/mL and 5.0 × 10⁸ nanoparticles/mL, respectively. Leachate exposures did not elicit significant Daphnia mortality. Sublethal micro- and nano-TP exposures significantly decreased microalgae ingestion by Daphnia after 24 h. The effects of tire-derived exposures observed pose a risk to aquatic organism survival at environmentally relevant concentrations. Full article

Asphalt modified with treated waste tires has good environmental protection and application value. However, the nano-interaction mechanism of crumb rubber (CR) and asphalt (especially its components) is unclear. In this study, molecular models of asphalt, asphalt components, CR, and CR-modified asphalt (CRMA) were constructed by molecular dynamics (MD) simulation. The validity of the model construction and parameter setting was verified by multiple indexes. The influence mechanism of CRMA density, asphalt-CR compatibility, mechanical indexes, and binding energy under the influence of temperature, CR dosage, and other factors was systematically analyzed. Results showed that the optimum temperature for preparing and storing to prevent segregation did not coincide. The solubility parameters (S_P) prediction model of the asphalt’s four components was obtained based on the multiple linear regression method. CR could enhance the mechanical properties of asphalt, but the improvement was limited to small dosages. Increasing the dosage can enhance the mechanical properties of asphalt; the mechanical properties can be significantly improved in medium- and high-temperature conditions. Bulk modulus and shear modulus were recommended for preferential analysis of the mechanical properties of CRMA. It is recommended that the optimal dosage be 20%. Full article

Asphalt modified with treated waste tires has good environmental protection and application value. However, the nano-modification mechanism of crumb rubber (CR) with asphalt is still unclear. This research investigates the mechanism, aging, and interfacial interaction with the aggregate of CR modification asphalt (CRMA). The base asphalt and CRMA (original and aged) and two typical aggregate models were constructed. The accuracy of the model was verified through multiple indicators. The effects of CR and aging on the physical properties (density, compatibility, and diffusion coefficient), mechanical properties, component interaction behavior, and interfacial interactions with aggregates of CRMA were systematically analyzed. The results showed that the CR reduced the diffusion coefficient of asphalt by about 31%. The CR inhibited the movement of the components of asphalt (especially saturate and aromatic), which significantly improved the mechanical properties of asphalt. The compatibility between asphalt and CR significantly deteriorated after aging. The difference in the solubility parameter was about four times that before aging. It is instructive for the regeneration of CRMA. Aging led to a decrease in the shear modulus and Young’s modulus of both base asphalt and CRMA, which verified and quantified the adverse effects of aging on the mechanical properties. Comparing the two aggregates, CaCO₃ had a greater adhesion with asphalt than SiO₂. The difference ranged from 22.5% to 39.9%, which quantified the difference in the adhesion properties of acid base aggregates with asphalt. This study can provide theoretical guidance for the modification and application of CRMA. Full article

Road paving costs have significantly increased in the last decades not only because of the increase in oil price globally, which has in turn increased the prices of bitumen, transportation, coarse aggregate and fine aggregate, but also due to the shortage of these virgin materials. Thus, it is essential to find more sustainable and cost-effective road paving solutions. This research focuses on the combination of recycled asphalt pavement (RAP) and crumb rubber extracted from end-life tires and new asphalt mixtures to assess the enhancement of asphalt performance and cost minimization. The optimal percentage of RAP mixed with new asphalt including crumb rubber with achieves the highest performance, stability, and durability of pavement, while considering the economic and environmental impacts was investigated. Experimental investigations, including a universal testing machine and the Marshall stability test, were implemented to evaluate different mixing percentages of RAP and the new asphalt including crumb rubber at different bitumen contents. Abaqus software was utilized to simulate a model with the new mixture to determine the stress and deformation characteristics under different loading conditions. The findings of the experimental study from testing more than 150 samples of asphalt with different percentages of mixing illustrated that a balanced mix of 50% RAP with 50% new rubberized asphalt with a 5% bitumen content achieved the optimal balance of stability, flow and density characteristics, which will offer a promising solution for more sustainable and cost-effective road-paving solutions. Full article

Globally, 1.5 billion annual tire outputs generate a substantial volume of end-of-life tires (ELTs), creating significant environmental challenges. Despite increased recovery rates, ELT management costs in Europe underscore the need for proactive strategies to mitigate environmental and health risks. This study comprehensively evaluates the environmental impact of disposal methods, including landfilling, incineration, and crumb rubber production, using Life Cycle Assessment (LCA) via the OpenLCA software 2.0.2. While incineration is sometimes identified as a disposal method, unprocessed scrap tires have potential applications in civil engineering that can better align with sustainability goals. Detailed ELT composition analysis reveals significant recycling potential, with car and truck tires containing 10–20% steel fiber content, less than 1–8% textile fibers, and approximately 80% natural and synthetic rubber content. Recycling 1 ton of ELTs saves an estimated 1.4–1.6 tons of CO_2 Eq. compared to incineration. Mechanical recycling and application of recycled crumb rubber in concrete show significant environmental advantages, reducing mass density by approximately 55% and enhancing ductility by up to 40%, according to material testing results. These properties make crumb rubber particularly suitable for acoustic and resilient applications. Additionally, its elasticity and durability offer effective solutions for shoreline reinforcement, mitigating erosion and providing stability during flooding events. When used as a replacement for river sand in cement composites, crumb rubber contributes to a 24.06% reduction in CO₂ emissions, highlighting its potential for environmentally friendly construction. Full article

The global rise in vehicle ownership has led to a significant accumulation of waste tires, with many ending up in landfills or incinerated, resulting in considerable environmental impacts. Several end-of-life solutions have been developed to repurpose these tires, and one promising approach is converting them into crumb rubber for use in road infrastructure. Crumb rubber has been incorporated as a stabilizing agent in asphalt mixtures, Portland cement concrete, base and sub-base granular layers, and subgrades. This application not only mitigates environmental harm but also often enhances the mechanical performance of these materials. Additionally, crumb rubber (CR) serves as a low-carbon material, offering environmental benefits such as reduced carbon footprint. This study provides a comprehensive literature review on the use of crumb rubber in road infrastructure materials, examining aspects such as treatment methods, mix design, mechanical properties, durability, and environmental impacts. It also highlights knowledge gaps and potential research directions to advance the application of crumb rubber in the road infrastructure industry. The findings suggest that, at appropriate dosages (in asphalt mixtures, for example, it is between 15–20% by weight of asphalt binder), crumb rubber can shift from being an environmental burden to a valuable resource across numerous road infrastructure applications. This review aims to guide agencies, designers, engineers, and other stakeholders in informed decision-making. Full article

Researchers are increasingly concerned about the vast amounts of waste rubber tires produced globally, which contribute significantly to environmental pollution. The potential of incorporating waste rubber tires to modify bitumen has garnered considerable interest. This study assesses pavement design temperatures according to SUPERPAVE standards for representative Malaysian regions. The assessment is based on hourly air temperature data and simulates temperature diffusion in typical Malaysian road pavements using the finite difference method (FDM). Tests on neat bitumen (PEN 60/70) and crumb rubber-modified bitumen (CR-TMB) samples evaluated their physical and rheological properties across various temperatures and aging stages. These tests were conducted using the dynamic shear rheometer, rotational viscometer, and bending beam rheometer. The attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) analysis provided insights into the aging processes of both PEN 60/70 and CR-TMB. The findings indicate that adding 15% crumb rubber to produce CR-TMB enhances the physical and rheological properties of bitumen. Additionally, this modification significantly improves aging behavior, highlighting its potential for more resilient and sustainable road construction materials. Therefore, the use of crumb rubber in road construction should be considered to improve pavement durability and strength. Furthermore, utilizing crumb rubber as an alternative material can reduce costs by recycling waste materials. Full article

The use of rubber crumbs provides a viable solution for alleviating the disposal problem of waste tires. In this study, rubberized sulfur concrete (RSC) was researched to investigate the optimal mixture proportion and to improve the mixing process in terms of compressive strength and durability performance. For the mixture of the RSC, sand, rubber particles, and micro-filler were adopted as aggregates and sulfur was used for the binding material. Moreover, two mixing processes were applied: the dry mixing process and the wet mixing process. Based on the test results, the increment of rubber particles in the mixture led to a decrease in the compressive strength for both the dry and wet mixing processes. To minimize the voids between the sand and rubber particles, the micro-filler was used at 5% of the total volume. The amount of sulfur varied slightly depending on the mixing process: 30% sulfur for the dry mixing process and 34% sulfur for the wet mixing process, respectively. Consequently, compared to the dry mixing process, the wet mixing process increased the bonding force between sulfur and rubber powder due to the simultaneous heating and combining. In toughness, the wet mixing process demonstrates a 40% higher energy absorption capability compared to the dry mixing process. For the durability performance of the RSC, the mixture with 20% rubber particles produced using the wet mixing process exhibited better corrosion and freeze–thaw resistance. Full article

Year by year, more and more plastic is used worldwide. A large part of post-consumer waste is still stored in landfills instead of being reused. The solution to this problem may be recycled materials (recyclates) or biodegradable materials. The method of 3D printing, regarded as a clean processing technology, can significantly contribute to addressing global plastic pollution by utilizing post-consumer recycled polymers to create new components and parts. Therefore, this study focuses on the assessment of various properties and characteristics of 3D-printed compositions based on post-consumer polypropylene (PP) and rubber crumbs, recycled from packages foils and car tires, respectively. Moreover, within this study, we compared the mechanical performance of the injection molding material with the one obtained from 3D printing. A characterization was made considering the thermal and mechanical properties as well as the “print quality” through the microscopic and tomographic analysis of subsequent print passes, the number of free spaces, and imperfections in the polymer melt. Samples obtained using the FDM and injection methods exhibited comparable melting temperatures, while the samples obtained by injection molding exhibited slightly better mechanical performance, higher hardness, and impact strength. Full article

This study aimed to investigate the behavior of accelerated carbonation-cured laboratory specimens using the ultrasonic non-destructive testing (UNDT) method and compare the results with the destructive testing (DT) method. The materials used in the study included a blend of lime kiln dust and ground granulated blast furnace slag (LKD-GBFS) wastes, natural fine aggregate (sand), and alternative fine aggregates from waste tires. The chemical analysis of the LKD and GBFS samples highlighted them as suitable alternatives to OPC, hence their utilization in the study. A 60:40 (LKD-GBFS) blending ratio and a 1:2 mix design (one part LKD-GBFS blend and two part sand) was considered. The natural fine aggregate was partially replaced with fine waste tire rubber crumbs (TRCs) in stepped increments of 0, 5, and 10% by the volume of the sand. The samples produced were cured using three curing regimens: humid curing (HC), accelerated carbonation curing (ACC) with no water curing (NWC) afterwards, and water curing after carbonation (WC). From the results, an exponential model was developed, which showed a direct correlation between the UNDT and DT results. The developed model is a useful tool that can predict the CS of carbonated samples when cast samples are unavailable. Lastly, a total CO₂ uptake of 15,912 g (15.9 kg) was recorded, which underscores ACC as a promising curing technique that can be utilized in the construction industry. This technique will bring about savings in terms of the time required to produce masonry units while promoting a change in the basic assumptions of a safer and cleaner environment. Full article