Waste Tire Research Articles

Study on the Performance of Modified Qingchuan Rock/Rubber Asphalt

This paper developed a new environmentally friendly composite modified asphalt material and studied the composite modification of Qingchuan rock asphalt (QRA) and waste tire rubber powder (RP) was studied in this paper. QRA/RP composite modified asphalt was prepared by adding these two materials as modifiers into matrix asphalt and compared with matrix asphalt and QRA modified asphalt. The basic properties of asphalt before and after aging were evaluated by the rotating thin film oven test. The high-temperature performance and permanent deformation resistance at different temperatures and frequencies were analyzed by the dynamic shear rheological test. The bending creep stiffness test was used to evaluate the low-temperature performance. In addition, the microstructure and modification mechanism of composite-modified asphalt were analyzed by scanning electron microscopy and infrared spectroscopy. The results show that QRA-modified asphalt is superior to matrix asphalt in terms of mass loss, viscosity ratio, and residual penetration, while QRA/RP composite-modified asphalt is further improved on this basis, QRA/RP composite modified asphalt can effectively improve the high and low temperature performance of asphalt.. Although the addition of RP is mainly based on physical modification, it also causes weak chemical reactions and enhances the adhesion of asphalt. The interaction between Qingchuan Rock asphalt and rubber powder significantly improves the overall stability of asphalt structure.

Pengaruh Waktu Iradiasi Ultrasonik dengan Aktivasi Kalium Hidroksida terhadap Sifat Fisis Karbon Aktif dari Serbuk Karet End Life Tire

Processing End Life Tire (ELT) rubber powder into activated carbon is an alternative for handling tire waste. One way to improve physical properties such as proximate characteristics, surface area and pore diameter of activated carbon is through chemical activation assisted by ultrasonic irradiation. This research aims to determine the effect of ultrasonic irradiation time with potassium hydroxide (KOH) activation on the quality of ELT rubber activated carbon. Activated carbon was synthesized and activated using 30% KOH at various ultrasonic irradiation times, namely 0 minutes, 15 minutes, 30 minutes, 45 minutes and 60 minutes. Based on the characterization results, activated carbon with an ultrasonic irradiation time of 30 minutes is the active carbon that has the most superior properties. The proximate characteristics of activated carbon meet the active carbon quality requirements of SNI 06–3730–1995 and have the highest surface area, namely 401.11 m2/g and pore diameter of 2.1652 nm, which is included in the mesoporous structure category so that it has the potential to be applied as an adsorbent for heavy metals from contaminated fluid.

An Innovative Approach for Oxidative Desulfurization Advancement through High Shear Mixing: An Optimization Study on the Application of Benzothiophene.

Alternative fuels are being explored to mitigate the effects of petroleum-based fuels. Pyrolysis oil from waste tires is a promising alternative fuel; however, it contains very high concentrations of benzothiophene (BT) which are beyond the allowable sulfur limits of Taiwan and the Philippines. Mixing-assisted oxidative desulfurization (MAOD) is a method that removes sulfur from fuel oils by utilizing high-shear mixing and oxidants. In this paper, the oxidation of BT in a model fuel was studied to determine optimal process conditions. Crude Fe(VI) prepared from sludge was used as the oxidant. Using the Box-Behnken design under response surface methodology, the significance of the following independent variables was studied: mixing speed (4400-10 800 rpm), phase transfer agent (PTA) amount (100 to 300 mg), Fe(VI) concentration (400-6000 ppm), and mixing temperature (40 to 60 °C). The results from a comprehensive statistical analysis showed the increase of sulfur conversion with high levels of Fe(VI) concentrations and PTA amounts together with low levels of agitation speeds and temperatures. The BT to BT sulfone conversions from experimental runs ranged from 17% to 64%. The optimum sulfur conversion of 88% for the BT model fuel was reached at the maximum levels of Fe(VI) concentration and mixing speed, along with the minimum levels of PTA concentration and temperature. The optimal MAOD variables were applied to a high-sulfur pyrolysis oil sample, which resulted in a sulfur reduction of 55%. The produced fuel oil meets the sulfur requirements of Taiwan and the Philippines for industrial heating oils. Therefore, the findings of the study support the effectiveness of sludge-derived Fe(VI) in the MAOD of BT in the model fuel and pyrolysis oil under mild process conditions.

Construction of Electrically Heated Pavement Using Recycled Waste Rubber Tires

Construction of Electrically Heated Pavement Using Recycled Waste Rubber Tires

The Influence of Devulcanization and Revulcanization on Sulfur Cross-Link Type/Rank: Recycling of Ground Tire Rubber.

Devulcanized rubber could be a valuable material feedstock to help in the manufacture of sustainable rubber products. However, the differences in the chemistry and structure of devulcanized rubber have limited industrial uptake. This work demonstrates how devulcanization affects the concentration and ratios of mono-, di-, and polysulfidic cross-links. These residual cross-links make devulcanized rubber chemically dissimilar from virgin rubber, affecting (re)vulcanization. The hypothesis that the sulfur rank of revulcanized material can be modified by the sulfur/accelerator ratio was evaluated by two different cure packages. Despite substantial differences in the accelerator/sulfur ratio, both recycled rubber compounds favored the formation of polysulfidic cross-links.

Mechanical properties investigation on recycled rubber desert sand concrete

The mechanical properties of recycled rubber desert sand concrete were studied to determine the effect of the replacement rate of recycled rubber and desert sand. The replacement rates of recycled rubber aggregates were set to 0 %, 5 %, 10 %, and 15 %, respectively, and for dessert sand aggregates were set to 0 %, 10 %, 20 %, and 30 %, respectively, during concrete preparation. The concrete's compressive, tensile, and freeze-thaw mechanical properties were tested at each replacement rate. The experimental results show that when the replacement rate of desert sand increases from 0 % to 30 %, the replacement rate of recycled rubber is 15 %, and the splitting tensile strength of concrete shows a pattern of first increasing and then decreasing. When the replacement rate for desert sand is 30 %, the replacement rate for recycled rubber rises from 0 % to 15 %, and the splitting tensile strength shows a pattern of first decreasing. With replacement rates of 10 percent for recycled rubber aggregate and 20 percent for desert sand aggregate, the damage to the concrete from external forces is relatively ideal. The compressive strength values are the highest, and the split tensile strength is the best, demonstrating good compressive and tensile strength. The results of CO2 emission analysis show that as the amount of recycled rubber increases, the CO2 emissions per unit volume of concrete also increase. The interface of the micro-optical structure in the concrete is straightforward, the pores are few, and it exhibits good mechanical properties. The concrete undergoes freeze-thaw cycles with relatively stable changes in compressive strength and split tensile strength, demonstrating a solid freeze-thaw resistive mechanical property.

Investigating the Viability of Rubber Crumbs from Waste Tyres as Partial Replacement for Coarse Aggregates in Concrete

The number of waste tyres is on the increase, because of the growing use of transport vehicles. Almost one trillion waste tyres are generated in the world annually. Established methods of disposal, recycling and re-use of waste tyres have failed to keep pace with generation, proven to be ineffective, cost-intensive and in some cases environmentally unsustainable. This study aims to investigate the effects of utilizing crumbs from discarded rubber as a partial replacement for coarse aggregates in concrete. Rubber crumbs of 10 – 20mm nominal size were produced manually from waste tyres. The rubber crumbs were used to replace 10%, 20% and 30% of coarse aggregates in design concrete of 20N/mm2 target compressive strength. The effects of this material on the slump, water absorption and compressive strength of concrete were examined. The inclusion of rubber crumbs resulted in a decline in the slump of concrete up to 10% relative to the control specimen. Water absorption increased marginally at 10% replacement compared to the control specimen and recorded a maximum value of 0.77% with 30% replacement after 28 days of curing. The compressive strength of the concrete was negatively affected by the rubber crumbs. The maximum value of 13.9N/mm2 was attained at 10% replacement after 28 days of curing. Rubberized concrete with 10% replacement of coarse aggregates can be used for non-structural concrete members such as roof slabs, non–load–bearing partition walls, and roadside barriers. Chemical treatment of rubber crumbs to improve surface adhesion properties should be encouraged.

Shear behavior of RC beams with openings under impact loads: unveiling the effects of HSC and RECC

Incorporating transverse openings in reinforced concrete (RC) beams reduces their load-bearing capacity and stiffness, making them prone to premature failure. This highlights the need for a more nuanced understanding of their behavior to ensure structural integrity, particularly under impact loads. This research delves into a relatively unexplored area, investigating the impact performance of RC beams containing openings through numerical analysis. By comparing different concrete types, the study seeks to identify optimal materials for such applications. The concrete damage plasticity model, accounting for strain rate effects, will be employed to simulate the material behavior of normal-strength concrete (NSC), high-strength concrete (HSC), and a novel eco-friendly alternative: rubberized engineered cementitious composite (RECC). RECC incorporates recycled tire rubber as a partial substitute for traditional concrete aggregates, offering a sustainable solution while mitigating environmental hazards associated with waste tire incineration. The finite element models are validated with experimental results, accurately predicting ultimate capacities, failure modes, and post-cracking response in RC beams (with/without openings) under static/impact loads. A comprehensive parametric analysis investigates the effects of concrete strength, impact energy, impactor mass, drop height, and opening location, providing valuable insights into how these factors influence the impact behavior under drop-weight testing. The results reveal that openings in RC beams under impact loads significantly reduce strength and stiffness, with detrimental effects observed for dual shear-zone openings. Surprisingly, a small mid-span opening can enhance impact response. HSC beams exhibit lower initial displacements but higher residual values, while RECC improves overall behavior in beams with openings, reducing maximum displacement and promoting energy dissipation for improved post-impact recovery.

Recycling of EPDM rubber via thermomechanical devulcanization: Batch and continuous operations

Thermomechanical devulcanization is a possible solution for the circular economy of EPDM rubber, as it removes covalent crosslinks from vulcanizates, resulting in a material similar to uncured rubber mixes. In this paper, sulfur-cured EPDM rubber was treated with thermomechanical stimuli: a) processing on a two-roll mill and in an internal mixer, and b) twin-screw extrusion. Horikx's analysis indicated a 75 % decrease in crosslink density with little polymer chain degradation. The resulting devulcanizates and non-devulcanized rubber crumb were added to the original rubber mix, yielding samples with 0, 25, 50, 75 and 100 wt% recycled rubber contents. Revulcanizates with up to 50 wt% devulcanizate content retained the tensile strength of the original rubber with a slight increase in modulus. Ultimately, batch devulcanization had the most promising results, and extrusion devulcanization was also more beneficial than using non-devulcanized rubber crumb. Crosslink density and morphological tests also support these findings.

Enhanced synergies for product distributions and interactions during co-pyrolysis between corn stover and tyres

Co-pyrolysis has been studied for its potential to recycle energy from biomass and waste tyres, as well as enhance the quality of the bio-oil. In this paper, the TG-FTIR-GC/MS technique and a fast-infrared heated reactor were used to investigate the co-pyrolysis behaviors and mechanism of waste tyres (WT) and corn stover (CS). Based on the TG-FTIR-GC/MS analysis, co-pyrolysis synergy promoted the production of methane and aromatics while inhibiting the formation of CO2. Co-pyrolysis products distribution shows that the best synergy occurred at a ratio of 30 % WT with the highest oil yield deviation of 19.67 % and the lowest water yield deviation of −13.30 %. Response surface method (RSM) was utilized to optimize the oil production and the highest oil yield of 30.25 wt% was acquired at a heating rate of 25 °C/s and a ratio of 40 % WT. According to the oil analysis, the light fraction of oil (gasoline and diesel) was more than 50 % in all conditions and there was a large number of aromatics (more than 30 %) presented in oil. The char characteristics indicated that several metals combined with -S radicals during co-pyrolysis which formed much metal sulfide and sulfate in chars.

Effect of Ni/tire rubber carbon as catalyst in the hydrodeoxygenation of used vegetable oil: biofuel evaluation in the reduction of atmospheric emissions

Abstract The sustainable valorization of discarded resources remains a challenge, and their requirements are crucial for long-term development. In this sense, we characterize biofuels of the diesel range obtained with used vegetable oils subjected to hydrodeoxygenation with Ni supported on tire rubber carbon obtained by the pyrolysis of waste tires. Under optimal reaction conditions, the vegetable oil conversion was 81.2 % with a selectivity of 82.3 % to C10–C18 alkanes, which is supported by the results of the catalyst characterization. A vertical direct injection engine was used to compare the behavior of the renewable biofuel and petroleum diesel blends. In comparison to petroleum diesel, the blends with renewable biofuel showed minimal power loss. In addition, the use of blends containing biofuels allowed a reduction of 25 % of CO and HC, as well as a decrease of 48 % is smoke compared to petroleum diesel, due to the fact that renewable biofuels improved evaporation after injection, reduced the density, and did not contain aromatic components.

Direct Recycling of Rubber: Effect of Staged Mixing on Bulk and Surface Properties of Thermoplastic Macro-Composites

The novel concept was used to upcycle GTR via cleavage of a cross-linked network with subsequent conversion into macro-composite. The pre-blend, which comprised loose 74 wt% GTR, was compacted with the matrix fusing under ram pressure. The final master step ensured the better bulk properties (interfacial adhesion, removal of macro-voids, viscosity) and the regular surface of the D2 blend, comprised of 20 phr SEBS. The extent of fragmentation could not be directly appraised, where traditional testing had failed to identify them. The regular surface quality and reduced viscosity of blend D2 evidence the decrease in size particles, accompanied by improving bulk properties (interfacial adhesion, removal of macro voids). The interactions were quantified using an analysis of peel strength; elastic recovery, tear, and tensile strength. Direct reprocessing via two-staged mixing governed the conversion of GTR to thermoplastic macro-composite., excluding the reclaim step.

Improving flexural response of rubberized RC beams with multi-dimensional sustainable approaches

This research presents a sustainable solution to waste tire disposal and raw material depletion by incorporating recycled rubber into concrete mixtures. To mitigate the reduction in mechanical properties, a novel slag pretreatment of rubber particles with controlled temperature is proposed. The study also investigates the effects of pouring concrete in layers with rubberized concrete (RuC) in tension side and normal concrete in compression side, as well as evaluating the use of GFRP compared to conventional steel, thereby introducing multiple innovative dimensions to enhance structural performance. The experimental study included a total of 27 specimens, consisting of normal concrete, untreated rubberized concrete, and treated rubberized concrete mixtures with 15 % rubber content. The study investigated both compression and tension mechanical properties of the concrete mixtures and assessed the flexural response of reinforced concrete (RC) beams. Parameters explored included rubber treatment, utilization of steel and GFRP as tensile reinforcement, and layered concrete pouring. Subsequently, a numerical study was conducted to address the impact of reinforcement ratio and layer depth on the behavior of slag-treated rubberized RC beams. The findings reveal a significant recovery of concrete compressive strength by 23 %, along with a 28 % enhancement in toughness and a 17 % increase in splitting tensile strength attributed to the application of slag treatment to rubberized concrete. The effect of rubber treatment was more pronounced in GFRP RC beams, as they showed similar load capacity as normal concrete. Furthermore, utilizing layered concrete beams with a 67 % depth of slag-treated RuC showed a comparable load capacity to normal RC beams, demonstrating only a 1 % reduction for steel-reinforced beams and a 2.4 % improvement for GFRP-reinforced beams. Notably, the numerical model emphasized this outcome and suggested that increasing the layer depth to 72 % of slag-treated depth displayed better performance.

Optimizing alkali-activated clay with rubber waste for sustainable earthen bricks: A comprehensive study

This study explores the potential of optimizing alkali-activated clay with rubber waste to create sustainable earthen bricks. The research addresses the environmental challenges associated with traditional cement-based construction materials by incorporating locally sourced calcined clay and recycled rubber tire waste. The experimental program involves testing different proportions of sand with calcined clay, varying sodium hydroxide (NaOH) concentrations, and integrating rubber content. The aim is to develop a material that balances environmental sustainability with improved mechanical and durability properties. The mechanical and microstructural properties of the resulting materials were evaluated through compressive and flexural strength tests, wetting and drying cycles, and advanced analysis techniques such as X-ray diffraction (XRD) and scanning electron microscopy (SEM). The results indicate that while the inclusion of rubber enhances certain properties such as reducing the unit weight and Structural Integrity During Wet-Dry Cycles, it adversely affects compressive and flexural strengths. This study highlights the importance of optimizing the balance between durability and mechanical strength to develop effective and sustainable construction materials.

Microplastic-Related Leachate from Recycled Rubber Tiles: The Role of TiO2 Protective Coating

The extensive global use of rubber results in significant microplastic pollution from the release of tire wear particles and microplastic leachate, impacting the environment, human health, and ecosystems. Waste tires are normally recycled and used for the production of new products, such as rubber tiles. The presented study aims to show the possibility of further decrease in the negative environmental impact of materials based on recycled rubber. This paper presents the modification of rubber tiles with a titanium dioxide (TiO2) coating, focusing on surface integrity, rubber particle wear release, and the consequent environmental impact of leachate release. Both reference and modified rubber tiles were subjected to artificial accelerated aging in a solar simulator for 4, 6, and 8 weeks, followed by an abrasion test. The carbonyl index was calculated from FTIR characterization after each time frame to indicate the degradation of organic compounds and chemical changes caused by UV exposure. A 24 h leaching test with a liquid-to-sample ratio of 1:20 was performed on both rubber tile samples prior to and after 8 weeks of aging along with the aged wear particles for the purpose of the non-target screening of released organic leachate by LC/MS QTOF. The results of carbonyl indices showed that the TiO2 coating contributes to the stabilization of polymer degradation and, to a certain extent, reduces the leaching of organic compounds, such as phthalates. However, the increased wear and release of rubber particles and the subsequent degradation of organic leachates require further in-depth research.

Challenges of a Circular Economy: The Example of Raw Recycled Tyre Steel Fibres Added to Concrete.

This research was conducted to analyse the possibility of using raw, untreated recycled tyre fibres as an effective concrete reinforcement according to circular economy principles. The aim of the article was also to develop a method for dispensing tire fibres on a real scale. Additional treatment and homogenisation of recycled steel fibres entail higher energy consumption, emissions of greenhouse gases, and increased costs. However, obtaining durable and safe concrete effectively reinforced with steel fibres is critical. Finding a balance between environmental friendliness and product durability is a circular economic challenge. Reference concrete with commercial steel fibres (15 kg/m3) and two concretes containing various quantities of non-treated, raw tyre recycled fibres (25 kg/m3 and 45 kg/m3) were industrially produced. Tests were carried out on the properties of the concrete mixture and hardened concrete, such as compressive strength, flexural strength, splitting strength, modulus of elasticity, residual flexural tensile strength, and fibre distribution in concrete. Tests revealed that increasing the amount of raw tyre fibres disturbs the structure and causes air entrainment and the formation of fibre clusters. Smaller quantities of raw tyre fibres turn out an effective concrete reinforcement. The use of non-treated tyre fibres as concrete reinforcement is possible but requires more stringent control of the concrete parameters. Implementation tests on an industrial scale are a novelty in this study, presenting an analysis of the possible dispensing of tyre fibres in a ready-mixed concrete production plant and testing the characteristics of manufactured concrete.

Influence of Tire Reclaimed Rubber (TRR) Loadings on Cure Characteristics and Mechanical Properties of Natural Rubber/Styrene Butadiene Rubber (NR/SBR) Blends

This investigation delves into the potential utilization of Tire Reclaimed Rubber (TRR) as a filler within Natural Rubber/Styrene Butadiene Rubber (NR/SBR) blends. TRR is obtained from discarded rubber tires and stands as a pertinent resource that necessitates its effective utilization in the production of eco-friendly, value-added rubber-based products. This is due to the rising of rubber waste tires which causes environmental concerns and all sorts of pollution. The TRR filled NR/SBR blends were fabricated using two-roll mills. The loadings of TRR were varied ranging from 20 phr to 100 phr. The aim of this study is to investigate the influence of TRR loading on the curecharacteristics and mechanical properties of blends in terms of tensile strength, rebound resilience, hardness, and density. It is found that the MH and Δ torque exhibited a decreasing trend which would indicate a reduction in crosslink density due to high loading of TRR. Meanwhile, the ts2 and tc95 increased with the increase of TRR loading. Furthermore, the tensile strength, hardness, density, and rebound resilience of blends experience a steady reduction with the incorporation of TRR. The decrement of those properties might be due to the low molecular weight of TRR. Regarding the collective findings, TRR emerges as a potentially viable candidate for waste rubber repurposing, serving as a non-reinforcing filler with optimal utility achieved at a 30 phr loading level.

Shear strength characteristics of mixing slag-stone ballast reinforcement with tire geo-scrap using large-scale direct shear tests

AbstractUtilizing the ballast layer with more durable and stable characteristics can help avoid significant expenses due to decreased maintenance efforts. Strengthening the ballast layer with different types of reinforcements or substituting the stone aggregates with the appropriate granular materials could potentially help to achieve this goal by reducing the ballast deterioration. One of the exquisite and most effective solutions to eliminate these challenges is to use waste materials such as steel slag aggregates and useless tires. Utilizing these waste materials in the ballasted railway track will contribute to sustainable development, an eco-friendly system, and green infrastructure. So in a state-of-the-art insightful, the ballast aggregates, including a mixture of steel slag and stone aggregates, are reinforced with a novel kind of geo-grid made of waste tire strips known as geo-scraps. This laboratory research tried to explain the shear strength behavior of the introduced mixing slag-stone ballast reinforced with tire geo-scrap. To achieve this goal, a series of large-scale direct shear tests were performed on the ballast which is reinforced by tire geo-scrap and included various combinations of slag and stone aggregates. The concluded results indicate that the optimal mixing ratio is attained by a combination of 75% slag and 25% stone aggregates which is reinforced by tire geo-scrap at a placing level of 120 mm. In this case, the shear strength‌, internal friction angle, vertical displacement, and dilatancy angle of stone–slag ballast reinforced with geo-scraps exhibited average changes of + 28%, + 9%, − 28%, and − 15%, respectively.

Mechanical and physical properties of flexible polyurethane foam filled with waste tire material recycles

Mechanical and physical properties of flexible polyurethane foam filled with waste tire material recycles

Enhancing the interfacial properties of recycled rubber aggregate mortars through surface modifications with graphene oxide coating

This study explores the potential application of waste rubber (WR) as sustainable recycled rubber aggregates (RRA) in the construction sector. A layer of graphene oxide (GO) was coated on RRA through multiple surface modification techniques, aiming to enhance the interfacial properties in RRA mortars. The C-S-H phases were first tailored through chemical synthesis to better understand the nucleation and growth of hydration products with the presence of GO. Subsequently, a 180 ± 10 nm-thick GO coating was attached to the RRA surface through surface treatment with sodium hydroxide solution, silane coupling agent, and GO suspension. In addition, the mechanical strength, damping performance, water absorption, chloride resistance, and microstructural properties of cement mortars prepared with RRA were further assessed. It was found that the GO coating significantly improves the bonding between RRA and the cementitious matrix due to its hydrophilicity and nucleation effects, which locally facilitate the cement hydration at interfaces. The cement mortars produced with surface-modified RRA exhibit promising high-damping characteristics, accompanied by improved durability and mechanical performance over those prepared with untreated RRA.