Waste Tire Research Articles

Advances and Outlook on Desulfurization and Utilization of Tire Pyrolysis Oil: A Review

Advances and Outlook on Desulfurization and Utilization of Tire Pyrolysis Oil: A Review

Sustainability assessment and impact of different recycled rubber aggregates on the performance of cement mortars

Sustainability assessment and impact of different recycled rubber aggregates on the performance of cement mortars

Sulfur Diffusion Studies Imitating Recycled Ground-Rubber-Containing Compounds

In-rubber properties of vulcanizates deteriorate in the presence of incorporated recycled ground rubber (GR). This behavior is partly explained by a possible diffusion of sulfur from the rubber matrix into the GR. Therefore, the sulfur concentration and, thus, the crosslink density in the matrix are reduced. This phenomenon was further investigated in this research work using two spatially resolved methods that supplement each other: the diffusion of soluble sulfur in GR-containing compounds was locally investigated via Micro X-Ray Fluorescence analysis. Viscoelastic properties were also determined spatially by the Micro Dynamic-Mechanical Indentation method. Combining the results of both methods, local concentrations of sulfur were related to local viscoelastic properties, revealing great differences in crosslink density at the interface between the GR and matrix material. In this way, it is shown that sulfur is capable of diffusing several mm, which locally doubles its concentration with respect to the sulfur content of the compound formulation. This, in turn, negatively impacts the homogeneity of crosslink density in both the matrix and GR, revealing a local increase in the elastic stiffness of 100 %. In addition, it was found that the vulcanization characteristics of the used polymers determine the amount of sulfur diffusion and, thus, the change in viscoelastic properties.

Experimental study on the mechanical evolution for waste tire rubber powder‐modified asphalt and its mixture considering the temperature characteristics in seasonal freezing regions

Experimental study on the mechanical evolution for waste tire rubber powder‐modified asphalt and its mixture considering the temperature characteristics in seasonal freezing regions

Recycled Carbon Black/High-Density Polyethylene Composite from Waste Tires: Manufacturing, Testing, and Aging Characterization

This study addresses the global issue of recycling used vehicle tires, typically burned out or trimmed to be reused in playground floors or road banks. In this study, we explore a novel environmentally responsive approach to decomposing and recovering the carbon black particles contained in tires (25–30 wt.%) by vacuum pyrolysis. Given that carbon black is well known for its UV protection in plastics, the objective of this research is to provide an ecological alternative to commercial carbon black of fossil origin by recycling the carbon black (rCB) from used tires. In our research, we create a composite material using rCB and high-density polyethylene (HDPE). In this article, we present the environmental aging studies carried out on this composite material. The topographic evolution of the samples with aging and the oxidation kinetics of the surface and through the thickness were studied. The Beer–Lambert law is used to relate the oxidative index to the characteristic depth of the samples. The UV photons are observed to penetrate up to 54% less with the addition of 6 wt.% of rCB compared to virgin HDPE. In this work, the addition of rCB as filler for HDPE used for outdoor applications has demonstrated to be an antioxidant for UV protection and a good substitute for commercial carbon black for industrial goods.

Catalytic steam reforming of waste tire pyrolysis volatiles using a tire char catalyst for high yield hydrogen-rich syngas

The production of hydrogen and syngas (H2/CO) from waste tires by pyrolysis catalytic steam reforming was investigated in a two-stage fixed bed reactor. In this study, tire char served as a sacrificial catalyst, facilitating the combination of catalytic steam reforming and char steam gasification reactions. The tire char acted as both a catalyst and a gasification reactant, enhancing the gas product yield. The process parameters investigated were, a reforming temperature range of 700–1000 °C, steam space velocity between 2 and 12 g h−1 g−1char and reaction times of 0.5–2 h. The influence of the parameters on the yield and composition of the product gases and the characteristics of the used catalyst were analyzed in detail. The results indicated that higher temperature and steam space velocity increased H2 and CO yields in the presence of a tire char catalyst. Elemental analysis of the used tire char, surface morphology and pore structure provided insights into the extent of tire char consumption in the reaction. Prolonged reaction time allowed for more thorough reactions between the pyrolysis volatiles and tire char, promoting the production of H2. At a reaction time of 2 h, the H2 yield reached 223 mmol g−1, representing 74 wt% of the maximum hydrogen yield.

Sulfate attack resistance of hybrid fiber reinforced rubber concrete

To increase the strength and applicability of rubber concrete, an eco-friendly concrete called hybrid fiber-reinforced rubber concrete (HFRRC) was produced by utilization of recycled tire rubber particles, basalt fibers, and polyvinyl alcohol fibers. This study investigates the sulfate attack resistance of HFRRC and normal concrete (NC). The mass variation, ultrasonic pulse velocity, compressive strength, failure mode, and microstructure of concrete specimens were investigated. The results showed that the corrosion resistance coefficient of HFRRC was higher than that of NC throughout the age of erosion. Further, HFRRC exhibited better integrity than NC when specimens were subjected to compression test failure. The findings can provide a useful reference for the application of hybrid-fiber reinforced rubber concrete suffered from sulfate attack.

Automated repair of asphalt pavement cracks and potholes utilizing 3D printing and LiDAR scanning

This study introduces a method for automatic repair of asphalt pavement cracks and potholes using 3D printing and LiDAR scanning. A scanning method was developed to accurately detect and represent cracks and potholes in a 3D model. To address the limitations of LiDAR scanning, such as missing data points caused by the irregular shapes of cracks and potholes, the screened Poisson method was applied to reconstruct the missing data points. These models were validated through both theoretical calculations and sand test. In addition, the research focuses on optimizing key 3D printing parameters, such as printing temperature and printing speed, to enhance performance of crack repair throughout semi-circular bending test. Direct tensile strength test was employed to assess the impact of waste materials (e.g., rubber tire powder and waste glass) on the bond strength of filled sample. The results indicated a volume difference of 2–5 % between the scanning method and the sand test method, demonstrating high accuracy in detecting and reconstructing 3D cracks/potholes. Binders modified with 10 % rubber tire powder, or 20 % waste glass exhibited the highest tensile strength of 212 kPa and 207 kPa, respectively. However, using more than 30 % waste materials is not recommended due to a significant reduction in bond strength compared to conventional binders. An optimal 3D printing speed of 180 mm/min and a temperature of 117 °C are recommended for use in 3D printing in laboratory conditions. It was also noted that higher printing speeds decrease indirect tensile strength, highlighting the importance of balanced parameter settings.

Mechanical and Microstructural Properties of Environmentally Friendly Concrete Partially Replacing Aggregates with Recycled Rubber and Recycled PET

Today, waste generation is a worldwide problem, where the major source of waste is generated by worn-out tires and Polyethylene Terephthalate (PET) bottles. Therefore, as a way to provide an ecological disposal and reduce the environmental impact, the feasibility of producing ecological concrete (EC) with recycled rubber (RB) and PET as substitutes for natural aggregates is explored, determining their physical, mechanical and microstructural properties. This experimental study considered the replacement of fine aggregate with RB at 1%, 4%, 7%, 10%, 20% and 30%, and the optimum content of coarse aggregate plus the replacement of coarse aggregate with PET at 1%, 5%, 10% and 15%. The results showed that the optimum percentage of RB was 1%, which, when combined with PET, resulted that the design with 1% RB+ 1% PET was the optimum replacement combination, increasing 10% in bending, 1% in compression and for tension it decreased by 11%, in turn with the XRD test quartz and different aluminosilicates were found, such as portlandite and by SEM-EDS it was possible to visualize polymer flakes embedded in the analyzed fragment. It is concluded that RB and PET can be viable for the production of EC only if low percentages of replacement by natural aggregates are used.

Molecular dynamics study of waste tire pyrolysis: Focus on intermediate product evolution and sulfur migration law

With the rapid development of the automotive industry, the large number of waste tires poses significant environmental and health pressures. Pyrolysis technology offers a way to resourcefully utilize waste tires by converting them into pyrolysis oil, pyrolysis gas, and pyrolysis char, which has promising application prospects. However, there are still considerable challenges in the application of this technology, such as unclear reaction mechanisms and the high sulfur content of the products, which limit its practical implementation. Although some research has elucidated the pyrolysis mechanisms, there remain significant gaps in understanding the evolution paths of key intermediate and final products, as well as the detailed migration and transformation patterns of sulfur. This study uses reactive molecular dynamics simulation to investigate the pyrolysis process of tires. A three-dimensional polymer molecular model was constructed to study the pyrolysis process of waste tires at different temperatures, focusing on the evolution of key products, intermediate products, and sulfur-containing components. The results indicate that CH4 and ·CH3 radicals collide with unsaturated hydrocarbons through carbon-hydrogen transfer reactions and radical chain reactions, leading to polymerization. During the initial stage of pyrolysis, sulfur primarily exists in the form of sulfur-containing hydrocarbons (CHS). As pyrolysis progresses, the quantity of CHS decreases. With increasing pyrolysis temperature, the proportion of sulfur in the S form far exceeds that of CHS. At a pyrolysis temperature of 3000 K, the proportion of S is 64 %, while the proportion of CHS is 23 %.

Prospects of electricity generation through the use of alternative sources such as waste tires processing products

The object of this study is a hybrid energy system that integrates the processes of recycling used tires with the use of alternative energy sources to design a sustainable and environmentally safe power generation system. The problem addressed in this study is to find effective methods for recycling waste tires for electricity generation, as traditional recycling methods are energy-intensive and lead to the loss of valuable resources. Three methods of tire processing have been considered: pyrolysis, thermal degradation, and mechanical grinding. The method of electricity generation using pyrolysis has demonstrated high environmental performance due to a significant reduction in greenhouse gas emissions and a high rate of renewable energy (80 %). According to the results of the study, the use of 5 MW pyrolysis furnaces in combination with 500 kW solar panels provides a reduction in dependence on fossil sources, reducing CO2 emissions to 50.0 kg/year. The method has high capital costs (NPC USD 4.2 million), but the cost of energy production (COE USD 0.18/kWh) makes this method competitive in the long run. Thermal degradation provides a balanced approach in terms of energy efficiency (75 %) and environmental performance. Although its CO2 emissions are higher than in pyrolysis, the method makes it possible to obtain additional products that could be used in other industries, thereby increasing economic efficiency. Mechanical shredding has the lowest average energy costs (USD 0.12/kWh) and the lowest CO2 emissions (30.0 kg/year), making it ideal for cost-conscious businesses. The study confirms the possibility of effective integration of renewable sources with tire recycling methods. The practical use of the research results is possible during the implementation of grant projects for the recycling of used tires, and in the work of relevant government structures for devising a policy for the disposal of used tires

Chemical and Rheological Evaluation of the Ageing Behaviour of High-Content Crumb Rubber Asphalt Binder

High-Content Crumb Rubber Asphalt (HCRA) binder improves road performance and address waste tyre pollution, yet its ageing behaviour is not fully understood. In this study, 70# neat asphalt binder and HCRA with rubber contents of 35% and 50% were selected and aged through the Thin Film Oven Test (TFOT) and Pressure Ageing Vessel (PAV) tests. FTIR (Fourier Transform Infrared Spectroscopy) and DSR (Dynamic Shear Rheometer) were employed to investigate their chemical composition and rheological properties. The FTIR results show that HCRA’s chemical test results are similar to those of 70#, but HCRA is more susceptible to ageing. I(C=C) strength decreases with age. The DSR results show that HCRA outperforms 70# neat asphalt binder in terms of viscoelasticity, high temperature performance and fatigue resistance, and exhibits greater resistance to ageing. The ageing index (AI) was obtained through a calculation using the formula, and overall, 70# neat asphalt binder is more sensitive to ageing behaviour and less resistant to ageing, and HCRA is particularly outstanding for fatigue resistance. A strong correlation is observed between chemical composition and some rheological property indicators. Therefore, we are able to predict the rheological properties using chemical composition indicators. This study provides insight into the ageing behaviour of a neat asphalt binder and an HCRA binder and demonstrates that the HCRA binder outperforms conventional asphalt in several performance areas. It also provides theoretical support for the consumption of waste tyres to prepare high content crumb rubber asphalt.

The Input of Nanoclays to the Synergistic Flammability Reduction in Flexible Foamed Polyurethane/Ground Tire Rubber Composites

Currently, postulated trends and law regulations tend to direct polymer technology toward sustainability and environmentally friendly solutions. These approaches are expressed by keeping materials in a loop aimed at the circular economy and by reducing the environmental burdens related to the production and use of polymers and polymer-based materials. The application of recycled or waste-based materials often deals efficiently with the first issue but at the expense of the final products’ performance, which requires various additives, often synthetic and petroleum-based, with limited sustainability. Therefore, a significant portion of research is often required to address the drawbacks induced by the application of secondary raw materials. Herein, the presented study aimed to investigate the fire performance of polymer composites containing highly flammable matrix polyurethane (PU) foam and filler ground tire rubber (GTR) originating from car tire recycling. Due to the nature of both phases and potential applications in the construction and building or automotive sectors, the flammability of these composites should be reduced. Nevertheless, this issue has hardly been analyzed in literature and dominantly in our previous works. Herein, the presented work provided the next step and investigated the input of nanoclays to the synergistic flammability reduction in flexible, foamed PU/GTR composites. Hybrid compositions of organophosphorus FRs with expandable graphite (EG) in varying proportions and with the addition of surface-modified nanoclays were examined. Changes in the parameters obtained during cone calorimeter tests were determined, discussed, and evaluated with the fire performance index and flame retardancy index, two parameters whose goal is to quantify the overall fire performance of polymer-based materials.

Acoustic Enhancement of Sustainable Concrete Mixture Through Integration of Recycled Tyre Waste

Acoustic Enhancement of Sustainable Concrete Mixture Through Integration of Recycled Tyre Waste

Mechanical and Microstructural Properties of Environmentally Friendly Concrete Partially Replacing Aggregates with Recycled Rubber and Recycled PET

Today, waste generation is a worldwide problem, where the major source of waste is generated by worn-out tires and Polyethylene Terephthalate (PET) bottles. Therefore, as a way to provide an ecological disposal and reduce the environmental impact, the feasibility of producing ecological concrete (EC) with recycled rubber (RB) and PET as substitutes for natural aggregates is explored, determining their physical, mechanical and microstructural properties. This experimental study considered the replacement of fine aggregate with RB at 1%, 4%, 7%, 10%, 20% and 30%, and the optimum content of coarse aggregate plus the replacement of coarse aggregate with PET at 1%, 5%, 10% and 15%. The results showed that the optimum percentage of RB was 1%, which, when combined with PET, resulted that the design with 1% RB+ 1% PET was the optimum replacement combination, increasing 10% in bending, 1% in compression and for tension it decreased by 11%, in turn with the XRD test quartz and different aluminosilicates were found, such as portlandite and by SEM-EDS it was possible to visualize polymer flakes embedded in the analyzed fragment. It is concluded that RB and PET can be viable for the production of EC only if low percentages of replacement by natural aggregates are used.

Rubbercrete as a sustainable solution for recycling waste tires in concrete: An overview

Due to the rapid growth of the automotive industry, the number of waste tires has been rising dramatically each year. This increase is causing a strain on landfills, as the bulky nature of waste tires, with about 75% of their volume being void, quickly depletes available space of landfills. Furthermore, waste tires are non-biodegradable and, due to their concave shape, provide an ideal breeding ground for insects and harmful rodents, posing a public health risk. Given the limited range of products that can be produced from recycled tires, it is crucial to find economically viable solutions to recycle these tires and use them in mass production of useful materials, such as concrete. Concrete has been chosen by researchers as it is the second most consumed material per capita, after water. Researchers have produced crumb rubber from recycled tires and used it to partially replace fine aggregates in concrete, creating a material known as rubbercrete. Compared to conventional concrete, rubbercrete has better thermal and acoustic properties, is lighter in weight, and more ductile. However, it also shows a reduction in mechanical strengths. This paper provides an overview of rubbercrete, highlighting its key challenges, advantages, and properties.

Mechanical and Durability Properties of Rubberized Sulfur Concrete Using Waste Tire Crumb Rubber

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.

Influence of rubber aggregates from the recycled tires on the physico-mechanical and durability properties of compressed earth blocks

To meet sustainable development goals, global policies are strongly oriented toward valorizing alternative resources such as local materials and waste from different sectors of activity. This study aims to evaluate the influence of adding rubber aggregates from used/recycled tires (GPU) on the physico-mechanical and durability properties of compressed earth bricks (CEB). The CEB were made with an earthen matrix containing 8% cement, and 0 to 2% mass of GPU. The CEB were cured under ambient conditions (30±5°C) for 28 days. The results showed a real improvement in physical and mechanical performance and durability indicators of CEB with increasing GPU content. The apparent density changed slightly from 1697 kg/m3 to 1733 kg/m3. Total water absorption decreased from 21% to 19% with a slight decrease in water-accessible porosity from 35.7% to 33.1%. The capillary absorption coefficient at 10 minutes also decreased from 14 g/cm2.min1/2 to 10 g/cm2.min1/2 The increase of 29% was noted on the compressive strength in the dry state ranging from 3.5 to 4.5 MPa and of 60% on the compressive strength in the wet state ranging from 1.1 MPa to 1.7 MPa. This resulted in the improvement of the structural efficiency coefficient by 27% ranging from 2080 to 2651 Pa.m3/kg. Abrasion resistance coefficient increased more than 50% ranging from 10.8 to 16.9 cm2/g. By comparing the results to the normative references, the CEB containing GPU can be classified as CEB usable in load-bearing walls in a dry environment and resistant to abrasion.

Optimizing Synthesis of Anionic Surfactant‐Modified Carbon Black for Enhanced Ammonium Adsorption

The increasing levels of ammonium in wastewater pose serious environmental issues, highlighting the urgent need for effective adsorbents to facilitate its removal. Although conventional biological treatment methods have certain drawbacks, adsorption using carbonaceous materials, such as carbon black produced from waste tires, presents a promising alternative for ammonium removal. However, the use of these materials has not been thoroughly investigated. This study focuses on optimizing the synthesis of carbon black modified with anionic surfactants to improve its capacity for ammonium adsorption. Utilizing Response Surface Methodology (RSM) and a Box‐Behnken design, the optimization process examined key variables, including reaction time, surfactant concentration, carbon black dosage, and surfactant type. Comprehensive characterization of the adsorbent was conducted to analyze its surface properties, functional groups, morphology, and elemental composition. The regression models produced highly accurate results with an R2 value of 0.9437. The optimal synthesis conditions were identified as a 12.30‐hour reaction time, a surfactant concentration of 8 mmol/L of sodium dodecylbenzene sulfonate, and a carbon black dosage of 30 g, achieving an ammonium removal efficiency of 84.80%. This study offers a scalable solution for ammonium removal in wastewater, promising practical applications and future sustainable waste management research.

Experimental study on recycling rubber to increase the impact resistance of cement mortar

The COVID-19 pandemic has led to a surge in medical waste generation, posing hazards to both the environment and global health. The impacts of the COVID-19 pandemic’s medical waste hazard may persist long after the pandemic itself subsides. Improper disposal of medical waste can contaminate environment, posing risks to ecosystems and public health. Discarded medical rubber gloves, for example, can become a source of infection, improper disposal of these gloves can escalate the spread of infectious diseases and increase the risk of transmission of the virus to the general public. This study proposes an innovative and sustainable method to reinforce cement mortar by adding recycled glove rubber as an additive to cement mortar to increase its resistance to impact loads. This study conducted uniaxial compression tests, separating hopkinson pressure bar (SHPB) experiments and SEM observations to evaluate the quasi-static compressive strength and dynamic stress of recycled rubber fiber mortar (RRFM) with varying recycled rubber fiber (RRF) contents (0, 1%, 2%, 3%). Strain curves, dynamic increase factor (DIF), energy absorption rules, failure modes, and microstructure of RRFM mixtures. The experimental results demonstrate that with the addition of RRF, the dynamic stress-strain curve flattens and the peak strain gradually increases. The RRFM sample shows stronger toughness. In comparison to regular cement mortar (NM), RRFM has a higher DIF and specific absorbed energy, a faster increase in dynamic compressive strength, and the ability to absorb more energy per unit volume. Under the same impact load, RRFM has fewer and smaller cracks than NM. Scanning electron microscopy (SEM) testing also observed that RRF formed a strong connection pattern with the cement mortar matrix.