Waste Tire Rubber Research Articles

Eco-friendly 3D printed concrete with fine aggregate replacements: Fabrication, characterization and machine learning prediction

During the last decade, 3D printing technology has experienced significant development, especially for concrete printing in construction. However, eco-friendly 3D printed concrete with fine aggregate replacements has not yet been sufficiently studied. Herein, twenty-five (25) mix categories are designed for use in 3D printed concrete. The mix materials include fine aggregates, silica fume (SF), ground waste rubber tire (Ru), and glass fiber (GF) composites. The mechanical characterization (i.e., stress-strain relations) are investigated, and the mechanical performance (i.e., compressive and flexural strengths) are reported. Numerical simulations are carried out to validate the experimental results, and satisfactory agreements are obtained. Machine learning prediction model is developed using the experimental and numerical results to predict the compressive and flexural strengths of the aggregate-mixed 3D printed concrete. An inverse relationship was observed between the rubber content and compressive strength of 3D printed concrete (RuC) printing imperfections is highly correlated with high rubber content. Similarly, increasing fiber volume in fiber concrete (FC) resulted in a decreased compressive strength due to reduced interlayer bond. Notably, hybridized concrete (HC) exhibited comparable strengths to fiber concretes at 1% fiber content, but a significant strength increase was observed at 5%, 10%, and 15% rubber contents with 2.5% fiber volume. Better stress-strain response (i.e., higher strength) is observed with larger SF content. It is evident that the addition of SF, GF, and Ru to concrete, improves cost efficiency and the stress-strain behavior of 3D printed concrete. The reported eco-friendly 3D printed concrete has a relatively low peak strength compared to normal concrete but shows traces of fatigue resistance. The eco-friendly 3D printed concrete provides the alternative for normal concrete for in-situ construction applications.

The Era of Exploitation of Waste Rubber Tires to Valuable Products

Producing modern types of new and renewable energy locally represents an inevitable necessity, through planning energy policies based on diversifying renewable and non-traditional sources by exploiting local resources, which contributes to securing the increasing energy requirements for daily and industrial needs and reducing dependence on traditional sources of energy resulting from oil and gas derivatives. Optimal exploitation of resources, including plastic waste, which is an important source to produce energy and liquid or solid fuels.

Mechanical, thermal, and morphological properties of poly(lactic acid) (PLA)/ recycled tyre rubber waste compatibilised with chain extender

The accumulation of waste tires in our society is a pressing issue due to their short lifespan and increasing demand. This research delves into effective methods for recycling waste tires, with a particular focus on utilizing biopolymers. Polylactic acid (PLA), a completely biodegradable polymer, has gained popularity for its biocompatibility, biodegradability, mechanical strength, and ease of processing. To overcome its toughness and thermal stability limitations, PLA has been blended with commercial polymers, such as rubber. Furthermore, the incorporation of recycled tire waste into PLA has demonstrated the potential to enhance its durability and strength. Joncryl® ADR is used as a chain extender and reactive compatibilizer to enhance the chemical interactions in the binary blend. The samples were prepared using a twin-screw extruder with the temperature between 150 and 190 ºC and 60 rpm of screw speed. These blends are then analyzed using a range of characterization techniques, including Fourier transform infrared (FTIR) spectroscopy, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), tensile testing, and notched Izod impact testing. The blends were then characterized by chemical changes, thermal transitions, and thermal degradation. it was found that the 90/10/0.6 (PLA/RW/ADR) nanocomposite exhibited maximum thermal degradation.

The Use of Waste Tyre Rubber Recycled Products in Lightweight Timber Frame Systems as Acoustic Insulation: A Comparative Analysis of Acoustic Performance

The current European standards demand more energy-efficient, comfortable, and sustainable buildings and encourage the incorporation of recycled materials in building construction. Timber buildings are successfully competing with traditional building materials in addressing these challenges; however, one of the weaknesses of timber systems is their limited sound insulation capacity. One material that can fit into the sustainability aims of timber construction and improve its acoustic performance is recycled ground tyre rubber (GTR), which, on top of this, is a serious environmental problem. This paper presents research on the use of GTR materials combined with timber systems in order to improve their acoustic performance. Three different types of GTR products (granulate, rolls, and sheets) of different thicknesses and densities are selected and are combined with different sound-absorbing materials (mineral wool, cellulose, and wood fibre) inside a lightweight timber sandwich system. In this study, the first qualitative approach, the acoustic performance of the different resulting systems is compared based on the sound pressure level difference measured in a custom-made reduced-size transmission chamber. Secondly, the sound reduction index of four selected specimens is measured in an accredited sound transmission laboratory. The results show that, for all the lightweight timber systems included in this research, introducing a GTR layer improves the acoustic performance of the system.

Studies on the Thermochemical Conversion of Waste Tyre Rubber—A Review

Waste from scrap tyres, due to its high volume (17 million Mg per year) and durability resulting from the physical and chemical properties, requires innovative approaches for efficient and environmentally friendly management. In many countries, the landfilling of waste tyres is banned (e.g., EU, USA, UK); however, waste tyres can be a source of valuable materials such as carbon black, pyrolysis oil, hydrogen-rich syngas, tyre char, as well as energy. The purpose of this article is to provide a synthesis of the state of knowledge regarding the thermal conversion of waste tyres by pyrolysis and gasification, taking into account the use of different measurement techniques and reactor types. These technologies are forward-looking and have a high degree of flexibility in terms of product sourcing, depending on the process conditions. The properties of waste from used tyres were analysed, i.e., the composition of the content of individual components and the main chemical substances. The results encompassed ultimate and proximate analyses of rubber from tyres, as well as the physical and chemical parameters of the tyre char obtained through pyrolysis. This article compiles available literature data regarding the impact of process and raw material parameters, such as temperature and time conditions, pressure, particle size, and catalyst addition on the pyrolysis and gasification processes. It also explores the influence of these factors on the yield and properties of the products, including pyrolysis oil, gas, synthesis gas, and tyre char.

Load–Displacement Behaviour and a Parametric Study of Hybrid Rubberised Concrete Double-Skin Tubular Columns

Rubberised concrete has emerged as a material of interest to the research community with the mission of creating sustainable structural members and decreasing the burden of waste tyre rubber. The potential benefits of replacing natural aggregates with rubber particles to obtain greater energy absorption and ductility are proven in the literature. To negate the reduction in capacity due to the addition of rubber particles, single- and double-skin confinements were proposed and successfully tested by researchers. Hybrid rubberised double-skin tubular columns (RuDSTCs) were recently trialled and tested by the authors. Each of these hybrid RuDSTCs had a filament-wound carbon fibre-reinforced polymer (CFRP) outer tube and an inner steel tube with rubberised concrete as the sandwich material between the two tubes. To explore the axial behaviour of such a column, this paper develops a finite element modelling strategy and carries out a comprehensive parametric study of the hybrid RuDSTC with 0%, 15%, and 30% combined aggregates replaced with rubber particles. This methodology is validated by experimental results, and a good agreement is found. Hybrid RuDSTC models are developed in four groups with different material and geometric parameters, in addition to those corresponding to the experimentally tested column, to explore the effects of the thickness ratio, hollow ratio, steel tube yield strength, and CFRP tube diameter with a special focus on the transition of the characteristic bilinear stress–strain curve of the hybrid RuDSTCs. The results show the smooth transition of the stress–strain curve with increasing rubber content after the yielding of steel, which indicates better ductility of the rubberised columns. The novel hybrid RuDSTCs can provide a promising sustainable solution with greater capacity compared with their unconfined counterparts. Better strain and enhanced ductility of the hybrid RuDSTCs compared with non-rubberized hybrid DSTCs enable their use in seismic-prone regions and mining infrastructure.

Crumb Rubber in Alkaline Activated Clay Roof Tiles at Low Temperature

The continuous increase in vehicle uptake escalates the number of rubber tyre waste to avoid landfilling and stockpiling. The present research focused on the sustainable use of crumb rubber in clay roof tiles. Tile samples were fabricated by heating the compacted mixtures at 50°C for 72 h, followed by increasing the temperature to 200°C for 24 h. Clay, crumb rubber, NaOH, and Na2SiO3 with a 10% alkaline activator were adopted. The weight of the crumb rubber was 0.5%, 1%, 1.5%, 2%, and 2.5%. X-ray diffraction (XRD) and scanning electron microscopy (SEM) analyses to study the phases and microstructures of the samples. The present study found that the optimum crumb rubber concentration was 0.5%, and 1% satisfied the standard requirement for the roof tiles.

Recycling waste tire rubber through an innovative water-medium ionizing radiation treatment: Enhancing compatibility and mechanical performance

In this research, we solved the compatibility problems of rubber mixtures containing waste ground tire rubber (GTR) with an innovative and environmentally friendly, water-based ionizing radiation treatment, meaning that the GTR is under water. Our hypothesis was that the strong oxidizing agents that appear during the radiolysis of water can activate the surface of the GTR, resulting in reactive functional groups containing oxygen, which can help establish a better interaction between the matrix and the GTR. We treated the GTR using different absorbed doses and examined the changes in the GTR using Soxhlet-extraction and cross-link density measurements. The surface of GTR was characterized by Fourier-transform infrared spectroscopy. Then we prepared GTR-containing natural rubber-based mixtures in an internal mixer, using two different mixing techniques. The mixtures were vulcanized in a hydraulic press, and the mechanical and morphological properties were investigated. As a result of the radiation treatment, cross-link density decreased slightly, while sol content did not change significantly. The FTIR spectra indicated that oxygen-containing groups appeared on the surface of the treated GTR. In the case of one-step vulcanizates, tensile strength increased by 11% and tear strength by 40%, while elongation at break remained high. For the two-step mixtures, tensile strength improved by 25%, tear strength by 35%, while elongation at break was over 400%. An irradiation dose of 20 kGy produced the best result, which is sustainable in mass production.

Effect of combined waste oils on the chemical, thermal, microscopic, and rheological properties of devulcanized waste tire rubber

This research investigates the influence of combined waste oils process variables, including the mass ratio of waste engine–cooking oil (WECO), medium reaction temperature for a constant reaction time, and waste tire rubber (WTR) mesh size, on the chemical properties, rheological properties, and thermal behavior of combined waste oil devulcanized WTR. The samples' chemical elements and bonding energy changes were characterized and their sol friction, thermal behavior, morphology, and rheological properties were analyzed. Different proportions of mixed WECO can devulcanize WTR under medium temperature. WECO with increased reaction temperature and waste engine oil improves WTR's devulcanization (mesh size: 80). The waste oil content significantly increased the WTR morphology quality and reduced its surface roughness. The de-crosslinked structure produced compound structural changeover. Thus, the rheological effects were significant. For devulcanized waste rubber engine–cooking oil, G* decreased gradually and δ° increased progressively, and its anti-fatigue performance increased as the fatigue factors decreased G* sin δ°.

Anti-deformation performance of asphalt modified by carbon black extracted from waste cooking oil pyrolysis waste tires rubber

As a promising renewable resource, waste tire rubber powder has been utilized to enhance asphalt performance but it has compatibility concerns with matrix asphalt. To solve the phase separation between crumb tire rubber (CTR) and asphalt, waste cooking oil (WCO) has been successfully employed as the solvent to desulfurize crumb rubber. However, about 30 % of carbon black is wrapped in crumb rubber, which has a high recycling value. The cross-linking network structure of the crumb rubber can be loosened by waste cooking oil, and the carbon black will gradually peel off. This study desulfurizes crumb rubber with waste cooking oil at 180 ℃, and the carbon black produced by the evolution of rubber structure was separated by Soxhlet extraction. The rubber-cracked carbon black (RCCB) and the industrial carbon black N330 were added to asphalt, and the impact of the two different carbon black on the anti-deformation of asphalt was analyzed by dynamic shear rheometer (DSR). The results indicated that at the same dosage of 5 %, the carbon black separated from rubber will weaken the deformation resistance of asphalt at high temperatures, rather than improving it like N330 produced in the industry.

Physical Chemistry Supports Circular Economy: Toward a Viable Use of Products from the Pyrolysis of a Refuse-Derived Fuel and Granulated Scrap Tire Rubber as Bitumen Additives

The production and maintenance of road pavements consume resources and produce wastes that are disposed of in landfills. To make more sustainable this activity, we have envisioned a method based on a circular use of residues (oil and char) from municipal solid waste pyrolysis as useful additives for producing improved asphalts and for recycling old asphalts to generate new ones, reducing at the same time the consumption of resources for the production of new road pavements and the disposal of wastes to landfills. This work aims to show the feasibility of the integration of two processes (thermal treatment of municipal solid waste on one side, and that of road pavement production on the other side) where the products deriving from waste pyrolysis become added-value materials to improve the quality of road pavements. In this contribution, we presented the effect of pyrolysis product addition on asphalt binder (bitumen) preparation and aging. Solid and liquid products, deriving from the pyrolysis of two kinds of wastes (refused derived fuel (RDF) and granulated rubber tyre waste), have been used for the preparation of asphalt binder samples. Rheological tests have been performed to determine the mechanical properties of neat asphalt binder (bitumen) and those enriched with pyrolysis derived products. Measurements to evaluate possible anti-aging effects have been also performed. The collected results indicate that char addition strengthens the overall bitumen intermolecular structure while bio-oil addition exerts a rejuvenating activity.

Leaching potential of metals and PAHs of asphalt rubber paving materials

Asphalt rubber (AR), a waste-based paving binder prepared with waste tyre rubber and asphalt binder, may contain hazardous components that pose environmental risks when applied to the road surface. This study aims to quantify this concern by characterizing the leaching process of AR using a multi-scale experimental method. The effects of various experimental variables on the leaching process were determined, and the leaching of metals and polycyclic aromatic hydrocarbons (PAHs) were characterized at three scales, i.e., binder, mortar, and mixture. The results suggested that AR presents no significant leaching concerns under most conditions, but the leaching of metals from AR might pose risks to the aquatic environments in the areas with acid rain. Furthermore, the leachability of metals increases with service time due to the aging of asphalt binder. The findings of this study can contribute to a better understanding of the environmental performance of AR and help conduct AR construction and maintenance in a more sustainable manner.

Recent advances on waste tires: bibliometric analysis, processes, and waste management approaches.

End of life tires (ELTs) are a pressing environmental concern due to their non-biodegradable nature and potential release of toxic chemicals, as confirmed by human health exposure studies. The expanding transport sector, driven by the automotive industry, has led to inadequate attention to safe tire disposal. This review extracted papers using keywords such as "waste tire rubber," "waste tire pollution," and "waste tire applications" from 2012 to 2023. Recycling publications have surged by 80% in the past decade, with China and the USA leading the research. Pyrolysis and devulcanization methods have emerged as key circular economy (CE) advancements, producing fuel and reusable rubber. Globally, 1.5 billion waste tires accumulate yearly, projected to increase by 70% in the next 30years if unaddressed. Around 26 million tonnes of used tires are generated annually worldwide, while civil engineering and backfilling use 17 million tonnes of recycled rubber particles. These tires are complex polymer composites, primarily composed of natural and synthetic rubber. The amorphous nature of rubber results in a 50% loss of mechanical properties when exposed to chemicals and microbes, shortening its lifespan. This paper explores the applicability of waste tire rubber and polymer fabrication to offer eco-friendly and cost-effective solutions for proper disposal, mitigating environmental accumulation.

Evaluation of self-compacting rubberized concrete properties: Experimental and machine learning approach

Diverse negative impacts of waste tire disposal have created a menace to a cleaner environment worldwide. Global awareness on the use of unconventional materials in concrete necessitated the use of solid waste in concrete. Towards sustainable construction and building materials, in this study, powdered waste rubber tires (PWRT) were incorporated into self-compacting concrete as a partial substitute for fine aggregate. The suitability of the self-compacting rubberized concrete (SCRC) was assessed by conducting workability tests (slump flow, T50, and L-box), mechanical tests (compressive, splitting tensile, and flexural strength tests), microstructural analysis, and durability tests. The results showed that an increasing percentage of PWRT had an adverse effect on the workability and flowability of SCRC. Mechanical strength at 3, 7, 21, 28, 56, and 90 days exhibited a reduction with an increasing PWRT content. Furthermore, the microstructural analysis showed weaker adhesion at the interfacial transition zone in the SCRC. A correlation matrix with empirical relationships was also developed. The effect of acid attack on SCRC was measured by immersion in HCL and Na2SO4, and a poor resistance was noticed. Machine learning regression algorithms were employed to predict the SCRC mechanical properties, including linear, ridge, lasso, decision tree, random forest, extreme gradient boosting, and support vector. In addition, evaluation metrics with statistical checks were also used to assess the model's performance. Ridge regression appeared best suited for predicting the compressive strength, while random forest regression best estimates the tensile and flexural strength.

Physicochemical investigation and thermogravimetric analysis of bamboo and poplar wood residues and tire rubber waste: Kinetic and thermodynamic analyses

This work conducted a physicochemical investigation of bamboo and poplar wood residues and tire rubber waste and their potential for conversion by pyrolysis from kinetic and thermodynamic aspects. The activation energies were obtained by means of a modified Friedman isoconversional method, with varying values of 133.0–248.4 kJ mol−1, 162.7–235.2 kJ mol−1, and 111.5–275.2 kJ mol−1 for the pyrolysis of bamboo and poplar wood residues and tire rubber waste, respectively. A combination of the kinetic compensation effect and a general empirical reaction model was used for the simultaneous determination of the frequency factors and empirical reaction models. The frequency factors of the pyrolysis of bamboo and poplar wood residues and tire rubber waste ranged from 1.5 × 109 to 4.7 × 1018 s−1, 1.2 × 1012 to 2.3 × 1018 s−1 and 1.3 × 107 to 3.4 × 1020 s−1, respectively. The effective thermodynamic parameters for the pyrolysis of bamboo and poplar wood residues and tire rubber waste were calculated, which indicated that these samples exhibited significant potential as raw materials for pyrolysis conversion.

Identification of patterns of strength formation of concrete using cement Portland Pozzolan (PPC) and waste tire powder in the condition of seawater curing

According to the national standard body in Indonesia, the compressive strength of 20 MPa concrete is medium quality concrete. Medium-strength concrete is usually used for floors, light construction, houses, warehouse factories, and sidewalks. The use of medium-strength concrete is very broad, it is necessary to continuously conduct research to produce new innovations. Previous research on the utilization of waste rubber tires has been carried out. Research on the development of concrete with the use of waste tire rubber powder is very interesting to do considering the waste of used tires that continues to increase along with the increase in the number of motorized vehicles in Indonesia. Portland Cement (OPC) and Portland Pozzolan Cement (PPC) are the two types that will be used in this research to see its effect on concrete with waste rubber powder. These two cements also have different corrosion resistance. And seawater is one of the triggers of high concrete corrosion. Research on the development of concrete with the use of waste tire rubber powder is very interesting to do considering the waste of used tires that continues to increase along with the increase in the number of motorized vehicles in Indonesia. Portland Cement (OPC) and Portland Pozzolan Cement (PPC) are the two types that will be used in this research to see its effect on concrete with waste rubber powder. These two cements also have different corrosion resistance. And seawater is one of the triggers of high concrete corrosion. This study aims to analyze how the compressive strength of PPC concrete compares with OPC and the addition of used tire powder under seawater treatment conditions. Six concrete variants were made and then tested for compressive strength. The compressive strength values of variants 1 to 6 were obtained as 20.78 MPa, 18.26 MPa, 19.56 MPa, 16.58 MPa, 13.03 MPa. The results show that tile powder is not effective in increasing construction strength, but the use of PPC cement is more effective than the use of OPC in improving construction, especially for cement use in buildings close to sea water

Penetration resistance and damage characteristics of cementitious mortar with partially replaced waste tire rubber as a filler against high-speed impact loading

Concrete, as the sole construction material, demonstrates an inadequate performance against high-speed impact loading. Resistance to such loading can be increased by adding rubber from the waste tire industry. In this study, the performances of cementitious mortar with the addition of waste tire rubber (WTR) powder were investigated against the strike of a high-speed projectile. By setting the target flow above 110 % and air content within a range of 5–7%, mortar with 30 % WTR was selected for high-speed impact test. Selected mortar specimens demonstrated significantly high resistance to damage and penetration against a high-speed projectile at impact speeds of 300 m/s and 420 m/s. Further, an experimental study revealed the contrasting behaviour of mortar specimens with WTR powder from that of conventional specimens, where typical compression occurred due to triaxial stress at the tunnel circumference formed by the intrusion of the projectile. Recommendation is made for composite mortar containing a less-stiff material such as rubber for new variables to be defined in the existing formulae, to quantify penetration in high-speed loading; given that the penetration resistance of specimens with 30 % WTR was larger than that of the control specimen, even with its lower compression strength.

A comprehensive review of the application of waste tire rubber in concrete/mortar as fine aggregate replacement

A comprehensive review of the application of waste tire rubber in concrete/mortar as fine aggregate replacement

Performance of rubberized reinforced concrete columns at ambient and high temperatures

The proliferation of discarded rubber tires is rapidly increasing at a concerning pace. Driven by the significant movement towards promoting environmental sustainability and mitigating the adverse environmental impact associated with non-biodegradable waste rubber tires, the objective of this study is to identify a viable and ecologically responsible resolution to the issue of discarded tires. This study experimentally focuses on the structural response and load-carrying capacity of reinforced concrete (RC) short columns containing crumb rubber as a partial replacement for fine aggregate after being exposed to temperatures of 27 °C, 300 °C, and 500 °C. Four concrete mixes were produced in which the natural fine aggregate (NFA) was partially replaced by CR with ratios of 0%, 5%, 10%, and 20% in volume. Twelve columns (three columns from each mix) were cast and tested under concentric loading. The experimental results showed that the workability and compressive strength of the concrete mixes decreased with increasing the CR replacement ratio. The residual failure load of columns decreased with increasing CR quantities and heating temperatures. The CR quantity had a more considerable impact on the decline of the column capacity than the heating temperatures. Analytical equations from international standards ACI 318–14, CSA A23.3, and previously existing equations were applied to study the validity of these equations in predicting the failure load of heated rubberized RC columns. Finally, a proposed equation for predicting the failure load of the columns is developed. The predicted failure loads obtained from the proposed equation were compared to the experimental results. The predictions from the proposed equation were in good agreement with the experimental data. Different statistical tests were done to compare the predictions from the proposed equation and previously existing equations for predicting the failure load of heated rubberized RC columns.

Mechanical behaviour of composite materials including waste rubber chips: experimental and numerical investigations

ABSTRACT Converting scrap tires to a useful form is becoming an acceptable technique for a broad range of applications. This study focuses on the mechanical characterisation of composites containing a high amount of waste tire rubber which are reinforced with different content of aluminium powder. Therefore, a set of experimental test is performed to highlight the effect of metallic fillers reinforcement on the mechanical response of elaborated composites under static and quasi-static tests. Results of this study reveal the high improvement of material properties for the elastomeric matrix reinforced with metallic fillers. In fact, the ultimate strength of composite material has increased to 1.8 MPa for a high reinforcement content. In the second part, a modified visco-hyperelastic model is developed on the basis of experimental results which demonstrate the prominence of the strain-rate-dependent behaviour consideration. Coupled with the Prony’s series approximation, the Mooney Rivlin model is actually applied to refine the strain energy potential in order to examine the mechanical behaviour of the composite material under different loadings conditions. Finally, the good concurrence between the numerical and experimental results highlights the impressive efficacy of the proposed model in accurately predicting the mechanical characteristics of the materials under investigation.