Waste Tire Research Articles

The utilization of pulverized waste tire rubber in a soil–cement composite for sustainable compressed earth brick production

This study examined the suitability of blending waste tires with cement in indigenous soil for producing compressed earth bricks (CEB) to achieve a sustainable environment. CEB was produced with clay soil and a combination of cement at 5 and 10% levels with varying dosages of pulverized waste tire at 0, 2.5, 5, 7.5, and 10% mixture. Classification tests were conducted to determine engineering properties such as the particle size distribution, Atterberg limit, specific gravity, optimum moisture and unit weight of the soil. The physical properties of the pulverized tire were evaluated. Moreover, density, water absorption, and compressive strength were determined for hardened CEB samples produced from mixtures of soil and various proportions of blended cement and pulverized waste tire materials. The classification results showed that the soil was silty clay of low plasticity. The density of the CEB samples was observed to increase slightly with the addition of blended cement-tire residue. Furthermore, a considerable improvement in the compressive strength development of the CEB was observed; however, compared with those of the control, the peak compressive strength of the CEB samples was greater when the soil was stabilized with 7.5% pulverized waste tire material and 10% cement. A decrease in the water absorption capacity of CEB was observed with an increase in the amount of pulverized waste tire and cement in the soil mixture. The response models corroborate the experimental findings indicating that amount of waste tire rubber residue and cement had significant effects on the CEB performance. This study ensure the beneficial recycling of waste tires blended with cement in soil for making medium-strength CEB to achieve sustainable, resilient masonry construction applications.Graphical

Effect of high-density-polyethylene (HDPE) and waste tire rubber (WTR) on laboratory performance of styrene butadiene styrene (SBS) modified asphalt

To reduce the cost of SBS modified asphalt, we incorporated waste high-density polyethylene (HDPE) and waste tire rubber (WTR) as partial substitutes for SBS modifier. The performance parameters for HDPE, WTR, and SBS synergistic modified asphalt were designed using the response surface method. Specifically, modified asphalt groups with excellent conventional properties were identified through penetration, softening point, and ductility tests. The high/low-temperature rheological properties and anti-aging properties of the selected modified asphalt were investigated. The modification mechanism of the composite modified asphalt was studied using fluorescence microscopy (FM). Subsequently, a cost analysis of the modified asphalt was conducted. Based on the aforementioned studies, we recommend a composition of 1.5% SBS, 3% HDPE, and 10% WTR, which demonstrated superior performance compared to 4% SBS modified asphalt. Furthermore, the cost of the modified asphalt was found to be 13.3% lower than that of SBS modified asphalt.

Graphene nanoplatelets on recycled rubber: an experimental study of material properties and mechanical improvements.

This study presents an experimental investigation of the mechanical behaviour of recycled rubber pads coated with graphene nanoplatelets. The investigation is part of an effort to develop a novel rubber-based composite that aims to reroute rubber from end-of-life tyres from illegal landfills and incineration back into the market in the form of a novel composite for vibration isolation. Graphene nanoplatelets were deposited on rubber pads via ultrasonic spray coating. The pads were made of a combination of recycled rubber (from tyres) and virgin rubber. A comprehensive analysis of the structural and chemical properties of the graphene coating, ensuring its integrity on the rubber substrate, was performed by combining surface topography, Raman and Fourier-transform infrared (FTIR) spectroscopy. Stacked coated pads were cured and tested dynamically in compression and shear under cyclic loading. Results showed promising improvements in the mechanical properties, in particular, in compressive stiffness and damping of the coated specimens with respect to their uncoated counterparts, laying the foundation for using graphene-enhanced recycled rubber as a novel composite.This article is part of the theme issue 'Celebrating the 15th anniversary of the Royal Society Newton International Fellowship'.

3D Cementitious composites printing with pretreated recycled crumb rubber: mechanical and acoustic insulation properties

ABSTRACT Cementitious materials incorporating recycled crumb rubber have become a common sustainable resolution in diverse building environments to achieve various functions in terms of lightweight, ductility, as well as energy absorption. This study explored the 3D printed rubberised cementitious composites (3DPRC) in two aspects: examining the effects of crumb rubber pretreatment conditions on compressive properties; conducting experimental and numerical analysis on the acoustic dissipation characteristics of 3DPRC. Fine crumb rubber granules (3-5 mm) replaced 10%, 20%, and 30% of river sand in the composites. Uniaxial compression tests indicated that the compressive strength of 3DPRC decreased with the increase of crumb rubber content and introduced anisotropic behaviour. Impedance tube tests were conducted to evaluate the sound absorption and insulation capabilities of 3DPRC. An optimal Noise Reduction Coefficient (NRC) of 0.35 was achieved with 30% crumb rubber. The sound insulation properties depend strongly on the mass density and porosity of the 3DPRC. Additionally, it is proved that the volume of built-in air gap has positive effects on both sound absorption and insulation properties. The results from Finite Element Method (FEM) numerical simulations correlated well with experimental data, proving the efficiency of the simulation and validating the experimental results.

Molecular dynamics simulation of interfacial interaction mechanisms between ground tire rubber and styrene-butadiene rubber enhanced by nanomaterial incorporation

The recycling of ground tire rubber (GTR) is an effective method for addressing black pollution. In this study, we investigated and compared the effects of acidic oxidation treatments and different nanomaterial contents on the interfacial properties of styrene-butadiene rubber (SBR) and GTR. Molecular models of GTR modified by acidic oxidation and nanomaterials, as well as SBR, were established. The interfacial interaction mechanisms between SBR and GTR were studied through tensile and shear behaviors. The results indicated that the properties of SBR-GTR interface were enhanced through acidic oxidation and nanomaterial modification, with the latter demonstrating superior advantages in augmenting the interfacial strength. Specifically, the addition of a carbon nanotube and graphene increased the interfacial cohesion strength by 55.12 % and 82.93 %, and the interfacial shear strength by 29.87 % and 43.05 %, respectively. Moreover, graphene exhibited superior performance in enhancing interfacial interactions compared to carbon nanotubes and increasing the nanomaterial content did not positively impact the improvement of interfacial properties. The interfacial properties of SBR and GTR were quantitatively analyzed using molecular dynamic (MD) simulations. This study provides a theoretical foundation for enhancing the mechanical properties of recycled rubber by using nanomaterials, thereby guiding the experimental preparation of recycled rubber.

Impact response and compression-after-impact properties of foam-core sandwich composites incorporating scrap tyre rubber particles

Integrating scrap rubber particles as fillers into polymer matrix composites offers a cost effective and environmentally sustainable pathway to manage tyre waste through the creation of value-added products. This research explores the low-velocity impact (LVI) response and compression after impact (CAI) properties of rubberised foam-core glass fibre-reinforced epoxy (GFRE) sandwich composites. Syntactic foam cores integrated with rubber particles were manufactured using vacuum-assisted resin transfer moulding (VARTM). The compression properties of rubberised foam core, vital for resisting impact damage during LVI, were examined. Results show more than 40% reduction in compression strength and modulus of the syntactic foam upon the inclusion of 33 wt.% rubber particles. The LVI response and residual compression properties of rubberised foam-core composites were also evaluated. Rubberised foam cores caused a marginal reduction in the peak impact force and led to approximately 60% reduction in the delamination area. The pre-impact compression strength was unaffected by rubber particles within the core as the GFRE face sheets carried most of the compression load. Post-impact compression strength was slightly higher in rubberised foam-core composites due to reduced delamination. Digital Image Correlation (DIC) analysis tracking of the strain evolution during CAI experiments revealed the stress-raising effect of the impact damaged region. This study showcases sustainable scrap tyre management through the inclusion of rubber particles into foam-core composites without substantially reducing in-plane compression properties before or after low-velocity impact.

Development of sustainable HPC using rubber powder and waste wire: carbon footprint analysis, mechanical and microstructural properties

This research advances the development of eco-friendly high-performance concrete (HPC) by integrating tire rubber powder and waste wire, focusing on both enhanced mechanical properties and reduced environmental impact. Substituting up to 40% of silica sand with rubber powder helps maintain the compressive strength necessary for high-strength concrete applications. The addition of waste wire is designed to improve ductility. A comprehensive evaluation includes mechanical and microstructural analyses, such as compressive, splitting tensile, and flexural strength assessments, in addition to Scanning Electron Microscopy (SEM) and Differential Thermal Analysis (DTA). Environmental implications are assessed by measuring the embodied carbon footprint. Findings indicate that the absence of rubber powder allows for a compressive strength peak of 95 MPa, while 50% rubber content leads to a decrease to 25 MPa, establishing a 40% rubber threshold for optimal strength. Conversely, 3% waste wire reinforcement enhances the strength to 106 MPa. Microstructural investigations reveal that increased rubber content adversely affects compressive strength by weakening the cement matrix, and reducing calcium-silicate-hydrate (C-S-H) formation. Significantly, the study reveals that replacing silica sand with rubber powder, along with waste wire reinforcement, substantially reduces the carbon footprint of the material, contributing to more sustainable construction methodologies.

Rubber concrete reinforced with macro fibers recycled from waste GFRP composites: Mechanical properties and environmental impact analysis

With the rapid growth of the automotive industry, a huge amount of tires have been produced, which inevitably led to the accumulation of scrap tires. A typical disposal routine is using scrap tires as a partial substitute for fine aggregate in concrete, producing so-called rubber concrete. However, the detrimental effects of rubber particles on concrete properties have been identified, which, to some content, hinders their broader application. The discrete fiber addition is shown to be effective in minimizing this detrimental effect, and this paper has therefore attempted to introduce macro fiber produced from waste glass fiber reinforced polymer (GFRP) into the rubber concrete system. Three series of specimens for compression, splitting, and flexural testing were tested. The test variables include concrete type (i.e., normal concrete, rubber concrete, and modified rubber concrete); and macro fiber content (i.e., 0–2 %). In addition, the inverse analysis is performed to transform the flexural test response into the tensile constitutive law of the fiber-reinforced concrete (FRC). The test results revealed macro fibers have little effect on the compressive strength of normal concrete and rubber concrete and a detrimental effect on that of modified rubber concrete. Incorporated fibers notably improve the splitting and flexural performance of normal concrete and rubber concrete. In addition, the cost and environmental impact analysis revealed that the addition of recycling products increases the concrete cost and results in a maximum reduction of carbon emissions by 17.3 % and embodied energy emissions by 80 %.

Pyrolysis of End-Of-Life Tires: Moving from a Pilot Prototype to a Semi-Industrial Plant Using Auger Technology.

This work, carried out within the framework of the BlackCycle project, demonstrates the robustness of an auger reactor for the pyrolysis of end-of-life tires (ELTs) to be considered within the seventh level of technology readiness (TRL-7). For this purpose, the resulting pyrolysis products are compared with those obtained from a pilot scale facility ranging within the fifth technology readiness level (TRL-5). Using the same type of ELTs, tire trucks (TTs), operating conditions used at the TRL-5 plant are attempted to mimic those expected at a semi-industrial plant: tailored temperature profile (450, 550, and 775 °C) and residence time for vapors (30 s) and solids (15 min). The feed mass rate is 4 and 400 kg/h for the pilot and semi-industrial plants, respectively. The yields of tire pyrolysis oil (TPO), tire pyrolysis gas (TPG), and raw recovered carbon black (RRCB) from both plants, as well as their key properties and characteristics, are in good agreement with each other. The TPO produced by both plants contains comparable concentrations of value-added chemicals such as benzene, toluene, xylene, ethylbenzene, and limonene. There is also a very similar pattern between the simulated distillation curves. The TPG obtained from both plants is also very rich in H2 and CH4 and has a lower calorific value of 52-54 MJ/Nm3 (N2 free basis). Although the RRCBs produced by the two plants are more demanding and require more labor, they do have a number of comparable characteristics. All this information demonstrates not only the reliability of the experimental campaigns to scale up the pyrolysis process but also the robustness of the semi-industrial scale plant based on the auger technology to be classified at TRL-7.

Improving shear behavior of rubberized concrete beams through sustainable integration of waste tire steel fibers and treated rubber

This study investigates the innovative and sustainable use of crumb rubber (CR) and waste tire steel fibers (WTSF) in reinforced concrete beams. By addressing the concern of reduced shear capacity in rubberized reinforced concrete (RC) beams, the paper presents a sustainable approach that integrates WTSF and a hybrid treatment of CR involving temperature and fly ash. Six different concrete mixtures were developed, incorporating 15 % and 25 % CR as a replacement for natural fine aggregates, both with and without treatment, along with the addition of WTSF. The experimental program assessed the workability, mechanical properties, including compressive and split-tensile strength, and conducted four-point loaded flexural tests on rubberized RC beams designed to fail in shear, in order to investigate their shear behavior.A numerical study further analyzed this hybrid treatment approach across various parameters, including concrete mixture compositions, types of tensile reinforcement (conventional steel or Glass Fiber Reinforced Polymer, GFRP), transverse reinforcement types (conventional steel or GFRP), longitudinal reinforcement ratios, and the combined effects of treated rubber and WTSF. Key findings include a 10 % higher compressive strength in the 25 % treated rubberized concrete mixture (TRC25) compared to the 15 % untreated rubberized concrete (URC15). Tensile strengths were significantly enhanced, with treated rubberized concrete beams containing WTSF at 15 % and 25 % showing tensile strengths 195 % and 180 % higher than normal concrete (NC), respectively. The inclusion of treated rubber and WTSF significantly improved shear capacities, with both 15 % and 25 % rubber content mixtures demonstrating substantially higher shear capacities than normal concrete. Toughness measurements indicated that treated rubberized concrete beams with WTSF at 15 % and 25 % rubber content showed toughness levels 15 to 18 times higher than NC. Beams reinforced with GFRP showed up to a 31 % higher load capacity and greater deflection before failure compared to those with conventional steel reinforcement. The study highlights a beneficial shift from shear to flexural failure modes due to the combined effects of treated rubberized concrete and WTSF incorporation.

Characterization of wood plastic composites made with recycled waste tire rubber

Abstract Green materials are currently demanded for construction as well as other products since the 26th UN Climate Change Conference of the Parties (COP26) in 2021. Using renewable and sustainable resources to innovate new materials such as composites is encouraged. This study aimed to investigate the physical and mechanical characteristics of wood plastic composites (WPCs) when adding waste tire rubber as filler for 10% or 20% by weight. The results showed that the density of the WPC samples (50 wt% wood − 50 wt% high density polyethylene) increased with the addition of the waste tire rubber (WTR) while the dimensional stability of samples was reduced. The mechanical properties of the WPC samples were determined, including flexural strength, flexural modulus, elongation at break, tensile strength, tensile modulus, and impact strength. The WTR as filler in the WPC tended to decrease the tensile strength and flexural strength whereas it improved the impact strength of materials. The results indicated that the WTR as recycled material in WPC affected the physical and mechanical properties of the WPCs. Although the use of the WTR in the production of the WPC adversely affects the mechanical properties, the use of 10 wt% WTR was acceptable. The results of the study showed that the addition of the WTR to the WPC production process can be useful for its recycling and for reducing the cost of the WPC.

Assessment of performance and emission characteristics of CI engine using tyre pyrolysis oil and biodiesel blends by nano additives: An experimental study

In the current study, the diesel engine performance, emission, and combustion have been investigated using tyre pyrolysis oil (TPO) and biodiesel blended with nano-additives. The effect of the blending ratio on fuel combustion and emission was evaluated. The tyre pyrolysis oil was derived from scrap tyres through the pyrolysis process and biodiesel was synthesized from used cooking oil (UCO) through the transesterification process. Moringa oleifera-derived strontium oxide (SrO) nanoparticles were mixed into the fuel to provide extra oxygen for better combustion. Three blended fuels were formulated as: a) 5 % biodiesel and 95 % TPO containing 50 ppm SrO nanoparticles (B5TPO95SrO50), b) 10 % biodiesel and 90 % TPO containing 100 ppm SrO nanoparticles (B10TPO90SrO100), c) 50 % TPO and 50 % biodiesel without nano-additives (B50TPO50). Among the blended fuels, B10TPO90SrO100 showed the best brake thermal efficiency at 31.4 % and a brake-specific fuel consumption of 0.21 kg/kWh at full load. The B5TPO95SrO50 blended fuel showed reduced emission parameters such as unburned hydrocarbon (HC), carbon monoxide (CO), and oxides of nitrogen (NOx) by 2.05 %, 8.30 %, and 18.00 %, respectively, as compared to the conventional diesel engine at an optimum engine load (27.9 Nm). Hence, waste tyre oil and UCO biodiesel blended with biogenic SrO nano additive can be considered a promising fuel for a sustainable environment.

Effect of low-content crumb rubber modification on the performance of bitumen and asphalt

The performance of flexible pavements is greatly influenced by rutting, fatigue, and durability, leading to premature failures under environmental conditions. The limitations of traditional bitumen in flexible asphalt pavements are due to the significant rise in traffic loads and volumes. The reason for incorporating tire waste into bitumen is its incredible qualities and economical price as a bitumen modifier. The quality of crumb rubber (CR)-modified bitumen mainly depends on the concentration of low-content CR dispersed into the base bitumen. The primary target of this research is to modify the bitumen with low-content CR to improve the thermal properties, rheology, rutting resistance, fatigue resistance, and moisture-damaged performance. The three concentrations, i.e., 5%, 10%, and 15% of CR, were selected based on extensive preliminary trials when dispersed in conventional 60/70 penetration grade bitumen. The consistency and mixture test results concluded that the optimum dosage of CR-10% provides a 20% improvement in thermal performance, a 15% increase in rheological stability, a 25% enhancement in rutting resistance, a 30% boost in fatigue resistance, and a 10% reduction in moisture damage susceptibility. The inclusion of CR makes rubberized asphalt an attractive and effective solution for highway construction, aligning with sustainable construction practices. The findings demonstrate that low-content CR-modified asphalt improved the durability of asphalt mixtures against moisture-induced damage and other benefits, such as reduced cracking and maintenance requirements. The CR technology led to a significant subsidization in the environmental impact of asphalt paving from 5 to 10% compared to standard paving applications.

Production of rubberized concrete utilizing reclaimed asphalt pavement aggregates and recycled tire steel fibers

The integration of waste tire elements into concrete, specifically granular rubber and discrete steel fibers, signifies a substantial advance in the pursuit of sustainable alternatives for rigid concrete pavements. This incorporation not only improves the ductility of rigid concrete pavements, but also augments their energy absorption capabilities. Similarly, replacing natural aggregates in concrete with reclaimed asphalt pavement (RAP) aggregates makes a large contribution to the reduction of negative environmental impacts, while conserving natural resources from depletion. This investigation explores the potential application of recycled rubber particles from waste tires (WTRR) and RAP aggregates as partial substitutes for natural fine aggregates, and evaluates their impact on the performance of rigid concrete pavements. Eight mixes were cast, each with two variables: (i) fine aggregate type (fine rubber (FRu) aggregates, fine asphalt (FAs) aggregates, and combinations of both types of aggregate) replacing 50 % of the natural fine aggregate; and (ii) waste tire recycled steel fibers (WTRSF) content (0 and 40 kg/m3). The axial compressive stress–strain, flexural load–deflection, and direct shear strength behaviors, together with the dry unit weight and volume of permeable voids for all concrete mixes were investigated and compared. The results show that, although the flexural and shear strengths decrease with the inclusion of FRu and/or FAs, the use of WTRSF noticeably mitigates the losses in strength that arise from the use of WTRR and/or RAP aggregates alone. The inclusion of WTRSF enhances the strain capacity of the concrete and allows the development of adequate post-peak energy absorption capacity in flexural and shear loading. Additionally, the dry unit weight of the proposed composites decreased by as much as 8 %, and their volume of permeable voids lies within the limits of high-durability concrete mixes (9–12 %). Hence, the proposed sustainable concrete composites are promising composites for rigid concrete pavement construction.

Review on Assessment and Performance Mechanism Evaluation of Non-Structural Concrete Incorporating Waste Materials

This research seeks to solve the multi-faceted problem of waste disposal by analysing the application of waste plastic and tyre material within non-structural concrete to ensure more sustainability and less environmental degradation. The study focusses on material properties, including specific gravity, water absorption, and bulk density and characteristics of the concrete that is produced by the utilization of the above waste aggregates, including workability, compressive strength, flexural strength, and tensile strength. This paper employs results from published past research from the literature and MATLAB (R2021b) in the analysis of the findings, pointing to the fact that the mechanical properties reduce with the level of waste content yet emphasizing the green aspect of such materials. Thus, a complex and diverse effect is demonstrated by the life cycle assessments (LCA) for global warming, ozone depletion, terrestrial ecotoxicity, and acidification. Furthermore, the utilization of waste materials decreases the compressive, flexural, and tensile strength, but it provides distinct ecological benefits which prove the importance of proper mix proportions for concrete performance. The outcomes of this research will be useful for further investigation in the application of the concept as well as to call for the development of new ideas for the improvement of bonding of wastes to aggregates in concrete.

Use of carbon black as a modifier for petroleum bitumen

The problem of recycling worn-out tires and recycling of solid carbon-containing residue from the pyrolysis of tires is considered. The possibility of processing carbon black from the pyrolysis of tires into a high-quality concentrate, which can serve as a raw material for modifying petroleum bitumen, has been shown. The nature of the interactions occurring between the components of carbon black and the matrix of petroleum road bitumens has been studied. The chemical interaction of carbon black with the bitumen matrix through unsaturated C=C bonds has been proven. The introduction of carbon black as a modifying additive leads to a significant change in the physical, mechanical and rheological properties of the resulting bitumen binder systems. Based on spectrometric studies, an assessment is made of the structural changes occurring in the original and modified bitumen during the production of modified bitumen binders. It has been established that with such modification, diffusion of aromatic hydrocarbons occurs from the bitumen component into the modifier particles. During the modification process, six-membered cyclic aromatic compounds are formed in the bitumen part, the composition of paraffin-naphthenic hydrocarbons changes, and sulfur compounds are formed that “transfer” from the modifier particles to the bitumen. Thus, in this study, the phenomenon of mutual diffusion between bitumen and CBWT modifier was confirmed using IR spectroscopy.

Quantitative determination of olefins in pyrolysis oils from waste plastics and tires using selective adsorption by Ag–SiO2 followed by GC×GC-FID

Determination of olefins in pyrolysis oils from waste plastics and tires is crucial for optimizing the pyrolysis process and especially for the further advanced valorization of these oils in terms of the circular economy. Identifying olefins, even using high-resolution techniques like GC×GC, is challenging without TOF-MS, which allows modification of the ionization step. Currently, the only method for determining olefins in plastic pyrolysis oils is GC-VUV, recently standardized as ASTM D8519. However, TOF-MS and VUV are not affordable instruments for many research teams working on plastics recycling. This paper introduces a simple method for the selective micro-scale adsorption of olefins over AgNO3/SiO2, followed by the GC×GC-FID analysis. Olefins are determined indirectly from the loss of chromatographic area in respective hydrocarbon groups before and after removal. Only 50 μL sample and 15 min of sample separation are needed. Our method was extensively validated and provides a reliable determination of olefin content in a wide range of pyrolysis oils from plastics and tires and their products after mild hydrotreatment. It is affordable to all researchers and industrial companies working on plastics recycling by thermochemical processes as it does not require an MS detector.

Experimental study on bond performance of interface between concrete and UHPFRC incorporating recycled tyre fibers

This paper conducted single-side shear tests on 27 groups specimens with dimensions of 100 mm × 100 mm × 40 mm to investigate the shear bond performance of the interface between concrete and ultra-high performance fiber reinforced concrete (UHPFRC) incorporating recycled tyre fibers, as an eco-friendly and cost-effective material. The effects of concrete strength, interface roughness, interface adhesives, and the substitution rates of recycled tyre fibers in UHPFRC were analyzed by Response Surface Methodology model. The findings revealed the existence of two failure modes, specifically interface failure and concrete failure, and it was observed that the shear load-slip curves exhibited a similar trend across various specimens, characterized by a gradual increase accompanied by an escalating growth rate. The higher concrete strength and interface roughness as well as the lower substitution rates of recycled tyre fibers would enhance the shear bond strength, while interface adhesives had minor effects. Based on the micro-bonding mechanism and experimental data, two theoretical models for shear bond strength and shear load-slip curves were established, demonstrating good agreement between prediction and experimental results. Considering the shear bond strength, the environmental and economic analysis was carried out, and UHPFRC with 25 % substitution rates of recycled tyre fibers exhibited the best benefits.

Novel Design of Eco-Friendly High-Performance Thermoplastic Elastomer Based on Polyurethane and Ground Tire Rubber toward Upcycling of Waste Tires.

Waste rubber tires are an area of global concern in relation to reducing the consumption of petrochemical products and environmental pollution. Herein, eco-friendly high-performance thermoplastic polyurethane (PU) elastomers were successfully in-situ synthesized through the incorporation of ground tire rubber (GTR). The excellent wet-skid resistance of PU/GTR elastomer was achieved by using mixed polycaprolactone polyols with Mn = 1000 g/mol (PCL-1K) and PCL-2K as soft segments. More importantly, an efficient solution to balance the contradiction between dynamic heat build-up and wet-skid resistance in PU/GTR elastomers was that low heat build-up was realized through the limited friction between PU molecular chains, which was achieved with the help of the network structure formed from GTR particles uniformly distributed in the PU matrix. Impressively, the tanδ at 60 °C and the DIN abrasion volume (Δrel) of the optimal PU/GTR elastomer with 59.5% of PCL-1K and 5.0% of GTR were 0.03 and 38.5 mm3, respectively, which are significantly lower than the 0.12 and 158.32 mm3 for pure PU elastomer, indicating that the PU/GTR elastomer possesses extremely low rolling resistance and excellent wear resistance. Meanwhile, the tanδ at 0 °C of the above-mentioned PU/GTR elastomer was 0.92, which is higher than the 0.80 of pure PU elastomer, evidencing the high wet-skid resistance. To some extent, the as-prepared PU/GTR elastomer has effectively solved the "magic triangle" problem in the tire industry. Moreover, this novel research will be expected to make contributions in the upcycling of waste tires.

Eco-economic analysis of utilizing high volumes of recycled plastic and rubber waste for green pavements: A comparative life cycle analysis

The strategic repurposing of substantial volumes of plastic waste and end-of-life tires into asphalt pavement presents a compelling practical solution to the growing waste accumulation problem. Adopting a comparative LCA and LCCA approach, this study focuses on the environmental, functional, and economic performance of hot mixed asphalt (HMA) produced with various compositions to determine the most sustainable solution in the local context. The compositions included unmodified, styrene butadiene styrene (PMB), and the novel recycled composite produced with devulcanized rubber and waste low-density polyethylene (DVR + LDPE composite) HMAs. Research findings indicate that HMA modified with DVR + LDPE composite outcompete the traditional counterparts by significantly reducing GHG emissions by 54.5 % and 14.4 % compared to unmodified and PMB HMAs, respectively. The same can be extended to the cost analysis. The discussion emphasizes the practicality and significance of the novel waste composite and stresses adopting a complete life cycle perspective for asphalt sustainability assessment.