Waste Tire Research Articles

Shear behavior of pre-damaged RC beams strengthened with UHPFRC-CFRP grid layer

Ultra-high performance fiber reinforced concrete (UHPFRC), incorporating recycled tyre fibers, and carbon fiber-reinforced polymer (CFRP) grid were utilized to strengthen the pre-damaged reinforced concrete beams caused by coupling action of sustained loads and marine environment. The failure modes, characteristic loads, deflection features, and strain behavior of the strengthened beams with various types of UHPFRC, thicknesses of UHPFRC layers, CFRP grid ratios, and CFRP grid layout angles were investigated. The results indicated that they exhibited the typical shear failure, and their characteristic loads increased by 102 %–205 % compared to the undamaged beam. By increasing the thickness of the UHPFRC layer and the CFRP grid ratio, and adopting 45° CFRP layout angle, the cracking stiffness, energy absorption capacity, and shear force sharing ability would be further improved, while adopting the UHPFRC incorporating recycled tyre fibers would decrease the ductility. Moreover, analytical models were developed to calculate the ultimate loads, manifesting reasonable accuracy.

Enhancing the pull-out behavior of ribbed steel bars in CNT-modified UHPFRC using recycled steel fibers from waste tires: a multiscale finite element study

In the current investigation, the effect of recycled steel fibers recovered from waste tires on the pull-out response of ribbed steel bars from carbon nanotube (CNT)-modified ultrahigh performance fiber reinforced concrete (UHPFRC) was considered using the multiscale finite element method (MSFEM). The MSFEM is based on three phases to simulate CNT-modified UHPC, recycled steel fibers (RSFs), and ribbed steel bars. For the first time, a bar ribbed has been simulated to make more realistic assumptions, and RSFs have been distributed in the form of curved cylinders of different lengths and with a random distribution within a concrete matrix. The interaction of the steel bar and the RSFs with the concrete is applied by the cohesive zone model (CZM). After confirming the simulation outcomes with the experimental results, the steel bar pull-out response is investigated using load-slip curves. The impact of the CNT content, RSFs and their aspect ratio on the bond strength of steel bars and CNT-modified UHPFRC was assessed. The results show that using RSFs with a lower aspect ratio (steel microfibers) significantly improves the pull-out characteristics of steel bars from concrete. Accordingly, the proposed MSFEM is considered for simulating the effects of different parameters on the pull-out response of ribbed steel bars from concrete without causing complex, time-consuming, or costly experiments. The results indicated that waste fiber or RSF can be used as a toughening component in CNT-modified ultrahigh-performance concrete and as a replacement for industrial steel fibers.

Co-pyrolysis development of waste tire-sludge adsorbent by mixed of waste tires and oily sludge

To facilitate resource utilization of waste tires (WT) and oily sludge (OS), waste tire-sludge adsorbent (WTSA) was developed using co-pyrolysis technology, and its effectiveness in adsorbing crude oil was investigated. The study revealed that the optimal preparation conditions for WTSA included a 1.5:1 mass ratio of WT to OS, a co-pyrolysis temperature of 600 ℃, a co-pyrolysis holding time of 2 hours, and a co-pyrolysis heating rate of 15 ℃/min. The surface of WTSA exhibited numerous pores and cracks with varying shapes and sizes. The dominant pore structures were found to be mesopores and macropores. The carbon content of WTSA was measured to be 89.95%. Moreover, the BET specific surface area, pore volume, and average pore size were determined to be 686.81 m2/g, 0.74 cm3/g, and 5.91 nm, respectively. In the crude oil adsorption test, WTSA demonstrated a comparable adsorption capacity to activated carbon (AC), but with a more attractive initial adsorption rate. Furthermore, thermal regeneration treatment was found to significantly enhance the lipophilic properties of WTSA, leading to an increase in its initial adsorption rate. The adsorption capacity of regenerated WTSA was also found to be relatively stable, making it an ideal solution for emergency crude oil spill cleanups. Compared to AC, WTSA can be recycled and reused multiple times, making it a more sustainable and cost-effective option.

An overview of patents of noise reduction in buildings

Noise is an unwanted sound in urban areas. Natural and or recycled acoustic absorbing or insulation materials are invented to reduce air and or impact sounds in buildings. Yet, they are not widely and commercially available. This review presented an overview of relevant studies on natural materials particularly on cotton and rubber using Scopus search engine and of the patents registered and granted using Espacenet and Google Patents search engines on noise reduction in buildings from the years 1996 to 2023. The 18% and 68% (out of 32 articles) relevant articles, respectively, were written on cotton and rubber and other recycled natural material e.g., consumed teabags, rubber crumb, indicating a clear vision for experimentation and modeling of natural materials e.g., to investigate their sound absorption coefficients at lower frequencies (below 250 Hz) for (recycled) cotton sound absorbing materials and for producing ultralight density with high sound absorption materials (0.56) using recycled rubber material. There were found 31 patents registered and granted, in total. Natural materials, namely, cotton, rubber, glass wool and rock wool were applied in 29% of patents registered and granted from 1996 to 2022. Yet, 93% of patents registered and granted lacked data on sound absorption index of materials they invented. LDA models estimated 29% of Espacenet and Google Patents patents registered and granted having an increased trend of patent innovations for example, in method, structure and building materials in the last decade.

Multi-response optimization of thermally efficient RC-based geopolymer binder using response surface methodology approach

This research addresses the persistent challenge of strength degradation in geopolymer-based materials incorporating rubber crumb (RC). An optimization model was developed, focusing on critical variables such as RC grade (particle size), percentage incorporation, and the molarity of NaOH, using slags as alumina-silicate precursors. Response surface methodology (RSM) was employed for experimental design and statistical modelling to predict the strengths and thermal conductivity of the resulting geopolymer. The study meticulously analyzed the influence of each parameter on the performance of RC-based geopolymers to understand their practical implications. The models generated were highly significant, demonstrating high practicability and minimal errors. The optimization revealed that a geopolymer with the highest strength (41.91 MPa) and lowest thermal conductivity (0.504 W/mK) can be achieved using a molarity of 10, grade 20 RC, and 18.5% RC content. This study highlights the potential of optimizing RC-based geopolymer mixes to enhance material performance, promoting the sustainable use of waste tires and advancing the development of high-performance construction materials.

Enhancing adhesive interlayer performance with waste tire rubber and amorphous poly alpha olefin compound modified asphalt

Insufficient bonding performance in interlayers is a key factor in the deterioration of bridge deck pavements. This study evaluates the bonding and durability of Waste Tire Rubber (WTR)/Amorphous Poly Alpha Olefin (APAO) modified asphalt compared to the commonly used Styrene-Butadiene-Styrene (SBS) modified asphalt. We conducted shear and pull tests to analyze how different bonding processes and the texture depth of the concrete surface affect bonding performance. The research also assessed the durability of the adhesive layer under conditions such as temperature fluctuations, water immersion, and aging. Results show that the choice of bonding method significantly impacts adhesive performance, with the coating bond method being superior to the crushed stone bond method. A concrete surface texture depth of 0.88 mm was identified as optimal for improving adhesive performance. Moreover, the WTR/APAO adhesive interlayer provided better adhesive and durability performance than the SBS adhesive interlayer under conditions of temperature fluctuations and water immersion. Based on these findings, the study recommends using the coating bond process and 15%WTR + 4%APAO modified asphalt for the adhesive interlayer.

Nature-based bank protection measures improve benthic macroinvertebrates in a stream draining an agriculturally dominated watershed

Increased bank erosion is one of the most significant threats to agricultural stream ecosystems. However, it is challenging to ascertain whether bank restoration measures positively affect in-stream habitats and aquatic communities. This study evaluated three nature-based bank protection measures' short-term (2-year) effects on aquatic physical habitat quality and benthic macroinvertebrate communities in a headwater stream in agricultural areas. The results demonstrate that nature-based bank protection measures can significantly improve the quality of aquatic physical habitat in streams. The TPRW (timber piles + riprap + willow cuttings) and WTRW (waste tires + riprap + willow cuttings) measures exhibited the most pronounced improvement in the quality of aquatic physical habitat in streams. The diversity of benthic macroinvertebrates was the highest in the TPRW reach, and the seasons significantly affected the density of benthic macroinvertebrates. The Shannon-Wiener diversity index and Margalef's richness index were the most consistent with the changing trend of physical habitat quality and are effective indicators of the ecological effects of stream restoration measures in our study area. In this study area, TPRW is the preferred measure for streambank restoration of agricultural streams, and WTRW is the alternative measure. However, the ecological effects of WTRW need to be monitored over a more extended period to identify whether there is potential ecotoxicity in the process of weathering and decomposition.

Sustainability-driven application of waste steel and tyre rubber fibres as reinforcement in concrete: An optimization study using response surface methodology

Innovative use of waste materials has proven to be effective for improving concrete’s technical properties while eliminating the threat of environmental pollution. There is paucity of research regarding the combined use of Waste Steel Fibres (WSFs) and Waste Tire Rubber Fibres (WTRFs) in concrete. Thus, this study aimed to investigate the influence of WSFs and WTRFs as reinforcement in concrete and determine their optimal fractions for enhancing the concrete strength properties using Response Surface Methodology (RSM). WSFs of 0.3-1.5% with a 0.6% increment and WTRFs of 0.3-1.5% with a 0.6% increment by concrete volume as reinforcement in concrete with water-to-cement ratio (W/C) of 0.25–0.65 with 0.2 increment were designed using the Box-Behnken Design of RSM. A total of fourteen (14) concrete mixes with a design strength of 25 N/mm2 were prepared. The fresh and hardened properties (slump, density, water absorption, 7- and 28-day compressive and split tensile strengths) of concrete were determined using standard procedures. The RSM was used to evaluate the interaction between the concrete variables and identify their optimum combination which gave the peak values of responses. Furthermore, the characteristics and sustainability of the concrete under optimum variables were compared with that of the conventional concrete. The outcomes revealed that the inclusion of WSFs and WTRFs yielded concretes with maximum slump, density, water absorption and 28-day compressive and split tensile strengths of 25 mm, 2633 kg/m3, 5%, 41 N/mm2 and 4.54 N/mm2, respectively. The optimization technique showed the optimal variables combination which yielded the peak response values of WSFs (1.40%), WTRFs (0.66%) and W/C (0.54). The nominal variance with the absolute percent error of less than (9%) between the actual experimental verified results and predicted results for all the responses validates the predictability of the model. The split tensile strength and compressive strength increased by 28.33% and 48.85%, respectively at the optimum setpoint of variable with respect to the reference concrete. In addition, the WSFs and WTRFs-reinforced concrete exhibited lower embodied CO2 emission but the embodied energy and cost are slightly higher relative to conventional concrete. Nevertheless, the embodied energy of the concrete was significantly lesser than that of concrete that used individual fibers for reinforcement. Thus, the enhancement of concrete strength properties with the prospect for sustainable fibre-reinforced concrete production through the use of waste steel and tyre rubber fibres is feasible.

Constitutive modeling and extended performance evaluation of concrete reinforced with non-hybrid waste tire steel fibers

This paper investigates the extended performance and constitutive modeling of waste tire steel fiber reinforced concrete (WFRC), making notable contributions to civil engineering materials. The study assesses constitutive modeling, reinforcement indices, and the long-term performance of concrete reinforced with varying percentages of waste tire steel fiber (WSF) ranging from 0.30 % to 1.75 %. A modified analytical model for predicting compressive stress-strain curves of WFRC is introduced and compared with previous analytical models for fiber-reinforced concrete. Additionally, a novel waste tire steel fiber reinforcing index, based on WSF properties, is proposed. Empirical relationships between strength properties and reinforcement indices are established. Experimental strength properties at the standard age, as well as water absorption, carbonation depth, and split-tensile strength of specimens aged beyond the standard age at 600 days and fiber-matrix interaction obtained by SEM analysis, are reported. Prediction models are proposed for estimating the mechanical properties of WFRC at the standard age, with results compared against existing codes. The proposed modified analytical model for the uniaxial compressive stress-strain curve demonstrates better coherence with experimental curves than existing models. Furthermore, empirical equations developed in terms of the waste tire steel fiber reinforcing index demonstrate satisfactory alignment between predicted and experimental strength properties. Significant improvements are observed in specimens aged 600 days, indicating the promising role of WSF in enhancing the long-term performance and serviceability of structures. Further studies are recommended to explore the performance of WFRC in aggressive environmental conditions.

Investigation on recycling and reprocessing ability of self-healing natural rubber based on ionic crosslink network

Abstract Natural rubber (NR) is a complex material that is often discarded due to its three-dimensional structure. Recycling of rubber is difficult due to its complex structure, and only 1.7 million tonnes of waste, such as tyres and gloves, are considered recyclable. This study aims to develop self-healing rubber, which allows a product to recover without affecting structural reliability. Commercial NR was ionically crosslinked with zinc thiolate, forming an ionic crosslink network between rubber chains and zinc thiolate ions. The ionic crosslinks allow the rearrangement of rubber molecular chains under external heat, providing self-healing capabilities. The highest ionic crosslink density was found in NR with 35 phr zinc thiolate. The self-healing NR can recover 90 % of its initial properties at room temperature for 10 min and can be reprocessed and recycled three times without compromising its properties. It also shows excellent weldability, making it a promising material for repairing existing rubber products in heavy engineering applications.

Innovative research on waste tire recycling for sustainable biofuel production: Assessment of its usability on multi-cylinder diesel engine employing constant injection of oxyhydrogen and biogas through a premixing device

This study investigates the production of waste tire pyrolyzed oil on a laboratory scale and its potential use as a fuel along with biogas and hydrogen in a variable-speed transportation engine. The pyrolyzed oil, obtained from waste tire pieces through a lab-scale plant, undergoes distillation and is blended with diesel fuel in a 20% ratio. This blended fuel is supplied to a multi-cylinder variable-speed transportation engine, either alongside biogas or HHO separately or both combined, at fixed flow rates with air passage through a premixing device (venturi). This study aimed to assess engine combustion characteristics such as in-cylinder pressure and heat release rate; performance parameters, including brake thermal efficiency (BTE) and brake-specific fuel consumption (BSFC), as well as emissions of hydrocarbons (HC), carbon monoxide (CO), and nitrogen oxides (NOx). The results indicate that using pyrolyzed oil in unmodified diesel engines reduces combustion characteristics and performancewhile increasing HC and NOx emissions and decreasing CO emissions. In addition, supplying biogas and the fuel mixture further deteriorates combustion and performance, while increases HC and CO emissions, and reduces NOx emissions. The focus of the present research is to evaluate the impact of adding green hydrogen (HHO) gas to a pyrolyzed oil fuel mixture and a biogas-led fuel mixture in a compression ignition (CI) engine. The results indicate that the addition of hydrogen enhances combustion characteristics, engine performance and reduces emissions, except for NOx. Specifically, there is an increase in cylinder peak pressure and HRR by around 6–10% range, improvement in BTE by 16–20% and BSFC by 5–7%, along with a decrease in HC and CO emissions by 13–16% and 11–13%, respectively. However, there is an increase in NOx emissions of 6–9%. In essence, the addition of green hydrogen enhances engine performance and reduces emissions in waste tire-derived pyrolyzed oil and biogas blends, indicating a viable path for sustainable transportation fuel.

Optimization of product distribution during co-pyrolysis of furfural residues and waste tyres via response surface method and infrared heating

Co-pyrolysis technique has proved to be an available way to recycle the energy of biomass waste and improve bio-oil quality. In this work, the co-pyrolysis behaviors and product distribution of waste tyres (WT) and furfural residues (FR) were studied by TG-FTIR/GC–MS and infrared heating fixed reactor. TG-FTIR/GC–MS results show that a large amount of CH4 and aromatics were produced at the co-pyrolysis temperature of 410°C. The response surface methodology (RSM) was utilized to optimize the yields of co-pyrolysis products, including oil, aromatic hydrocarbon (AH) in oil, and CH4 in gas. It was found that the highest oil production of 39.24 wt% was obtained at 550 °C and 10 °C/s, with the highest AH content of 35.02 % and the highest CH4 yield of 17.65 wt% at 700 °C and 40 °C/s. Co-pyrolysis oil and char characteristics were analyzed by SIMDIS, GC–MS, XPS, and the ultimate analysis. It was found that there was a high D-limonene content in oil (up to 25.79 %). With increasing co-pyrolysis temperature, AH content gradually increased and that of acid in oil declined. As the temperature elevated from 400 to 700 °C at 10 °C/s, the content of AH rose from 6.48 to 31.56 % and that of acid decreased from 19.74 to 11.73 %. In addition, the transformation of organic sulfur into metal sulfides was facilitated by raising the temperature.

The Effectiveness of Waste Tire Pyrolysis Oils (WTPOs) as Rejuvenating Agents for Asphalt Materials

The Effectiveness of Waste Tire Pyrolysis Oils (WTPOs) as Rejuvenating Agents for Asphalt Materials

Catalytic Activity of Incorporated Palladium Nanoparticles on Recycled Carbon Black from Scrap Tires.

A stable support substrate for catalytically active metal nanoparticles (NPs) plays an important role in various chemical transformation reactions. This study describes the effective integration of catalytically active palladium nanoparticles (PdNPs) into recycled carbon black (rCB) obtained from scrap tires. The loading efficiency and dispersion degree of PdNPs prepared via a deposition-precipitation method are thoroughly compared to those prepared with conventional Vulcan CB. As the rCB powder exhibits relatively larger surface areas and wider pore size distributions, slightly polydisperse and more PdNPs are integrated across rCB than those on CB. These composite materials are subsequently tested as catalysts in the Suzuki coupling and styrene hydrogenation reactions. For the Suzuki reaction using phenylboronic acid and bromobenzene, the PdNPs on rCB exhibit slightly higher reactivity than those on CB (TOF of ∼9/h vs ∼8/h), presumably due to the structural features of the integrated PdNPs and the relatively hydrophobic characteristics of the rCB substrate. For the hydrogenation reaction, both composite materials easily result in over 99% yield under ambient conditions with similar activation energies of ∼32 kcal/mol. These composite materials are also recyclable in both reactions without a detectable loss of the PdNP catalyst and its activity. Understanding the physicochemical properties of rCB and demonstrating their potential use as a catalyst support substrate evidently suggest the possibility of replacing conventional CB, which also provides an idea of upcycling waste tires in the development of practical and green reaction systems.

Characterization of light components in rubber-oil mixtures reclaimed asphalt and their effect on the self-healing performance of asphalt

The aging process of asphalt pavement results in the loss of light components (saturates and aromatics) in asphalt, necessitating the use of regenerators for restoration. The study examined the variation pattern of light components in reclaimed asphalt and their effect on the self-healing performance of asphalt after regeneration. Two types of aged asphalt were analyzed using low-temperature co-pyrolysis products of waste tire crumb rubber (WTCR) and waste cooking oil (WCO). The reclaimed asphalt was fractionated into light components using the SARA (saturates, aromatics, resins, and asphaltenes) method. The regenerator containing the highest concentration of light components was identified through the Soxhlet extraction test. The compound compositions and functional groups of the light components in reclaimed asphalt were characterized using gas chromatography-mass spectrometry (GC-MS) and Fourier transform infrared spectroscopy (FTIR). Moreover, the self-healing performance of the reclaimed asphalt was evaluated using a dynamic shear rheometer (DSR). The results indicate that the 260-1-WROM regenerator produced an optimal content of light components under pyrolysis conditions at 260 °C for 1 h. Incorporating the 260-1-WROM regenerator in RTFO resulted in an increase in hopanoids, oxygenates, heterocyclics, and aromas. Similarly, the PAV regeneration process exhibited elevated levels of paraffins, hopanoids, oxygenates, alkanes, heterocyclics, and aromatic compounds. However, the presence of 260-1-WROM failed to increase the contents of steroids. Both types of reclaimed asphalts exhibited superior self-healing capabilities compared to 70#A, RTFO, and PAV. This suggests that 260-1-WROM effectively restored the light components in the aged asphalt, thereby optimizing the flowability of the reclaimed asphalt and enhancing its self-healing properties. Given the above findings, the recommended dosage for 260-1-WROM is 8 % for RTFO and 10 % for PAV.

Effect of the sharp profile geometry ong the cutting forces of tire recycling tools

Objective: Study the impact of blade profile geometry on cutting forces during tire recycling, focusing on how variations in the shape and design of tools affect the efficiency and quality of the cut, as well as the tools' lifespan. Methodology: Through the construction and testing of three blade geometries, based on a prior numerical study and made from DF2 and 1.2363 steel, experiments were conducted on a Universal Testing Machine with samples of used tire rubber. Results: It was demonstrated that the hollow profile blade significantly reduces energy consumption and improves cutting performance compared to the 30° straight V profile blade, for both rubber-only samples and those with reinforcing textile fibers. Additionally, the study presented the evaluation of shear stresses using a 90° blade, indicating an average shear stress value of 8.67 MPa. Conclusion: This finding suggests that the appropriate selection of blade geometry can significantly contribute to the efficiency of the tire recycling process, offering important economic and environmental implications.

Sustainable Engineered Designs and Manufacturing of Waste Derived Graphenes Reinforced Polypropylene Composite for Automotive Interior Parts.

The automotive sector is actively pursuing a lightweighting strategy as a means to urgently decrease greenhouse gas emissions, which are a significant driver of climate change. The development of lightweight composite structures has been identified as crucial for enhancing part performance while mitigating negative environmental impacts and adopting energy-efficient manufacturing methods. This comprehensive study aimed to decrease the main reinforcement content of talc in commercial compounds while integrating graphene derived from waste polypropylene (PP) grown on talc and graphene nanoplatelet obtained from waste tires by upcycling processes into the PP compound. The entire value chain of interior automotive part production, from compound development and scaling up with a high-shear mixer, to injection molding of the part and performance tests, was investigated with a focus on sustainability considerations. The successful integration of 4 wt % micron talc, together with 1 wt % graphene nanoparticles and 1 wt % hybrid additive into the blended HomoPP/CopoPP matrix resulted in a 10% weight reduction compared to the conventional part. Moreover, significant improvements in flexural and tensile strength were observed, with enhancements of 52 and 38%, respectively. The uniform dispersion of additives and improved interfacial adhesion between the PP matrix and additives facilitated efficient stress transfer, contributing to enhanced mechanical properties. Furthermore, a systematic life cycle assessment study demonstrated the positive impact of waste PP incorporation on CO2 reduction, achieving a remarkable 95% reduction compared to virgin PP. The developed compound also demonstrated favorable processability and flow properties, supporting its potential for mass production. Overall, this study presents a sustainable and effective approach for lightweight automotive interior part production using a synergistically designed PP compound meeting the requirements of the automotive industry.

Fine-grained concrete properties in depending on carbon black additive introducing methods

The object of research is fine-grained concrete with carbon black additive obtained from the recycling of rubber tires. This study aims to determine a method for introducing carbon black into fine-grained concrete that achieves the best strength characteristics. The first method involves the preliminary preparation of a suspension by mixing a superplasticizer, carbon black, and part of the water. The second is the granulation of carbon black together with a superplasticizer in the ratio water: superplasticizer = 9: 1, followed by its introduction into the dry mixture and the addition of water at the last stage of mixing the raw material mixture. The addition of carbon black in powder form to the concrete mixture resulted in a decrease in strength from 35.1 MPa (without carbon black) to 34.9–25.6 MPa (with 4–12% carbon black). The effectiveness of the method of introducing granular carbon black was established, with an increase in strength by 40% in relation to the mixture obtained by the first method. The best strength of 50 MPa was demonstrated by the mix with 4% granular carbon black, which was 6% higher than that of the reference mix. Granulation of carbon black makes it possible to reduce its hydrophobicity and solve the problem of uniform distribution of carbon particles during homogenization of the raw material mixture in the presence of water.

Effective waste management through Co-pyrolysis of EFB and tire waste: Mechanistic and synergism analysis

Driven by the need for solutions to address the global issue of waste accumulation from human activities and industries, this study investigates the thermal behaviors of empty fruit bunch (EFB), tyre waste (TW), and their blends during co-pyrolysis, exploring a potential method to convert waste into useable products. The kinetics mechanism and thermodynamics properties of EFB and TW co-pyrolysis were analysed through thermogravimetric analysis (TGA). The rate of mass loss for the blend of EFB:TW at a 1:3 mass ratio shows an increase of around 20% due to synergism. However, the blend's average activation energy is higher (298.64 kJ/mol) when compared with single feedstock pyrolysis (EFB = 257.29 kJ/mol and TW = 252.92 kJ/mol). The combination of EFB:TW at a 3:1 ratio does not result in synergistic effects on mass loss. However, a lower activation energy is reported, indicating the decomposition process can be initiated at a lower energy requirement. The reaction model that best describes the pyrolysis of EFB, TW and their blends can be categorised into the diffusion and power model categories. An equal mixture of EFB and TW was the preferred combination for co-management because of the synergistic effect, which significantly impacts the co-pyrolysis process. The mass loss rate experiences an inhibitive effect at an earlier stage (320 °C), followed by a promotional impact at the later stage (380 °C). The activation energy needed for a balanced mixture is the least compared to all tested feedstocks, even lower than the pyrolysis of a single feedstock. The study revealed the potential for increasing decomposition rates using lower energy input through the co-pyrolysis of both feedstocks. These findings evidenced that co-pyrolysis is a promising waste management and valorisation pathway to deal with overwhelming waste accumulation. Future works can be conducted at a larger scale to affirm the feasibility of EFB and TW co-management.

THE MECHANICAL PROPERTIES OF CRUMB RUBBER STEEL FIBER CONCRETE (CRSFC)

Waste materials can be used in concrete as part of replacement material. Currently, 4 billion tires are abandoned in landfills, with 1 billion generated annually and 1.2 billion dumped without treatment by 2030. The number of waste tires is continually increasing, because of the growing use of transport vehicles. Therefore, effectively reusing waste tires as crumb rubber in the mix of concrete can save energy and protect the environment, while the use of steel fiber in the concrete will help enhance its properties. The aim this research to producing the steel fiber crumb rubber concrete (CRSFC) and to balance the issues of strength loss and sustainability. Crumb rubber is used as sand replacement in the mix concrete in the following proportions: 0%, 5%, 10%, 15%, and 20%, while steel fiber is added in the following proportions: 0.5% by volume. Slump, compressive strength, dry density, water absorption, ultrasonic pulse velocity, and rebound hammer tests are performed on the concrete after curing. As the percentage of CRSFC increased, the slump value and dry density decreased while the water absorption increased. Steel fiber helps increase compressive strength by 33 % over normal concrete. The optimum percentage of crumb rubber in CRSFC as a sand replacement is approximately 5% to 10% by volume. In summary, incorporating crumb rubber and steel fibers into concrete can result in a more eco-friendly and resilient construction material.