Waste Tire Research Articles

Economic and Sustainable UHPC at Scale: Material Variability Study and Application to Full Axial Columns

The high cost of robust UHPC of a proprietary nature and expensive constituents hinders mass production and expansion into full structural applications. This study provides experimental research and validation to support new initiatives in scalable, economical UHPC of a semi-proprietary nature that leverages local and sustainable materials and explores the use of raw recycled tire fibers. The study provides comprehensive material trials and mechanical characterization validated through the fabrication and testing of five full-scale axial UHPC columns with varying reinforcement ratios, fiber ratios, and types of fibers. Overall, the result shows that incorporating local and sustainable components into proprietary mixtures does not compromise the mechanical properties of UHPC with compressive strength of more than 150 MPa and modulus of elasticity ranging from 41.8-43.4 GPa. In addition, the axial strength capacity of economical UHPC columns, designed accordingly with ACI, performed better than non-ACI-compliant columns by up to 26.8%.

Water Resistance Analysis of New Lightweight Gypsum-Based Composites Incorporating Municipal Solid Waste

Incorporating waste to produce new environmentally friendly construction products has become one of the great challenges of the industry nowadays. The aim of this research is to analyse the behaviour of novel gypsum composites against water action, incorporating recycled rubber aggregates (up to 8.5% vol.) and dissolved expanded polystyrene (up to 10.0% vol.). To this end, a total of 10 dosages have been proposed with the progressive substitution of natural resources by these secondary raw materials. The results show how it is possible to reduce the total water absorption of the gypsum composites by up to 8.3% compared to traditional gypsum material. In addition, it is also possible to reduce water absorption by capillary by up to 52.7%, resulting in lighter composites with good performance against water action. In all composites analysed, the mechanical strengths exceeded the minimum values of 1 MPa in bending and 2 MPa in compression, making them an optimal solution for the development of lightweight prefabricated products for damp rooms.

Stripping down sustainability assessments for easier comparison of innovative recycling options

In this short communication we propose a screening approach for assessing the sustainability of new recycling options. Before performing a full comparative LCA it is useful to perform a simplified LCA because of the lower data intensity. The impact categories are limited to greenhouse gas emissions and land use. As an example car tire recycling is shown. This screening approach is already useful for decision makers and can be used by stakeholders to compare innovative with the baseline technology.

Pemanfaatan Limbah Ban Bekas untuk Sintesis Nanokomposit MnO2/C dengan Metode Hidrotermal sebagai Material Superkapasitor

Activated carbon from waste tires is used as MnO2 metal oxide doping in making MnO2/C-based nanocomposites into high-density and environmentally friendly supercapacitor electrodes. The MnO2/C nanocomposite synthesis process was carried out using the hydrothermal method by varying the mass of activated carbon by 1.25 g, 2.5 g and 3.75 g to determine the optimum results. Based on the results of research that has been carried out, it shows that MnO2/C can be used as a high density supercapacitor electrode. This is in accordance with the XRD test results which show that the MnO2 nanocomposite with the addition of C was successfully synthesized and has an orthorhombic crystalline phase. The SEM test results show that the material has almost the same morphology, namely many protrusions which make each particle have high roughness. The most optimal results were obtained from the MnO2/C-50 variation because it has the highest C element content, namely 39.93%, so it has the highest capacitance value of 5.791 f/g during the CV test. The GCD test shows that electrodes with a carbon variation of 2.5 g have a much longer and constant charge-discharge measurement time. In the EIS test, this variation shows a resistance value that is not too high and not too small, materials that have good storage capacity or capacity have moderate resistance.

Experimental Investigation and Machine Learning Prediction of Mechanical Properties of Rubberized Concrete for Sustainable Construction

Concrete is widely used in civil engineering applications and the natural aggregates which used in concrete are scarce, but its demand is increasing. The disposal of rubber tyres poses a significant environmental challenge, as their decomposition releases harmful chemicals into the soil and water bodies over many years. Decomposition of tyres should be done in a smart way and hence came the emergence of mixing recycled rubber crumbs into concrete as Rubberised Concrete (RC). This paper provides an in-depth analysis of the mechanical properties of concrete such as Compressive Strength (fck), Tensile Strength (ft), Flexural Strength (fcr) of 7, 14, 28 days in replacement of fine aggregate with fine rubber (FR), and Coarse Aggregate with Coarse Rubber (CR). The results indicate that RC is more suitable for structural applications, including Reinforced Concrete columns, beams, slabs, than conventional concrete. The primary objective of the article is to explore the potential use of recycled rubber crumbs in concrete, referred to as Rubberised Concrete (RC), and to analyze its mechanical properties such as compressive strength, tensile strength, and flexural strength over different curing periods. Additionally, machine learning (ML) based prediction model has been developed for various strength characteristics of concrete mixtures at 28 days. The hyperparameter optimization using Grid Search CV with fivefold cross-validation have been performed to obtain the best hyperparameters. The model’s performance is evaluated using metrics like MAE, MSE, RMSE, and R-squared values. Results reveal varying performances among different ML algorithms for predicting flexural, tensile, and compressive strengths.

Improved demineralization of the carbon black obtained from the pyrolysis of the sidewall and tread of scrap Tires: Extraction of some micro-/macro-nutrient elements of plants

In parallel with the increasing tyre production in the world, the amount of scrap tyres is also increasing. Within the scope of scrap tyre management, studies aimed at preventing the accumulation of tyres that threaten the world in terms of human health and the environment can be briefly defined as 4RL, including recycling, reuse, recovery, regeneration, landfill. Current methods have not yet completely controlled the accumulation of scrap tires. In this study, sidewall and tread parts of scrap tires with different compositions were pyrolyzed separately. Pyrolytic carbon black has been upgraded with an improved acid-base extraction method. Two different carbon blacks of high commercial value were obtained from the tire sidewall and tread. Since the mixture obtained from acidic-basic extraction, consisting of elements such as Zn, K, Na, Ca and S, are micro and macro nutrients of plants, the solution can be used directly in the fertilizer industry. With this study, the commercial value of solid residue, which is a major bottleneck in tire pyrolysis plants, has been increased. The pyrolysis method has been transformed into a more feasible project.

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.