Tire Rubber Research Articles

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.

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.

Sustainable thermoplastic elastomers based on thermoplastic polyurethane and ground tire rubber

AbstractIn this research, blends are prepared of thermoplastic polyurethane (TPU), ground tire rubber (GTR) and its devulcanized version (dGTR). The primary objective is to produce thermoplastic elastomers wherein TPU is partially substituted by GTR or dGTR obtained from used tires, thereby forming a blend with a favorable cost/value ratio and a smaller environmental footprint. Throughout the experiment, the rubber content of the blends is varied between 0 and 50 wt% and the effect on mechanical properties is investigated. The blends are compounded with a twin‐screw extruder, after which sheet samples are produced by injection molding. With a view to a possible future industrial application, it is important that both the compounding and the injection molding of the specimens are easy to perform, even with a 50 wt% filler content. Increasing the amount of rubber phase reduce the tensile strength and elongation at break of the blends. Unfortunately, devulcanization did not significantly improve the properties of the blends. Overall, even at a (d)GTR content of 50 wt%, an elongation at break of 300% is achieved, which allows the use of the blends as thermoplastic elastomers. In addition, dynamic tests show that the rubber phase increases the damping capacity of the samples.

Nontarget analysis and characterization of p-phenylenediamine-quinones and -phenols in tire rubbers by LC-HRMS and chemical species-specific algorithm

BackgroundN,N′-disubstituted p-phenylenediamine-quinones (PPDQs) are oxidization derivatives of p-phenylenediamines (PPDs) and have raised extensive concerns recently, due to their toxicities and prevalence in the environment, particularly in water environment. PPDQs are derived from tire rubbers, in which other PPD oxidization products besides reported PPDQs may also exist, e.g., unknown PPDQs and PPD-phenols (PPDPs). ResultsThis study implemented nontarget analysis and profiling for PPDQ/Ps in aged tire rubbers using liquid chromatography-high-resolution mass spectrometry and a species-specific algorithm. The algorithm took into account the ionization behaviors of PPDQ/Ps in both positive and negative electrospray ionization, and their specific carbon isotopologue distributions. A total of 47 formulas of PPDQ/Ps were found and elucidated with tentative or accurate structures, including 25 PPDQs, 18 PPDPs and 4 PPD-hydroxy-quinones (PPDHQs). The semiquantified total concentrations of PPDQ/Ps were 14.08–30.62 μg/g, and the concentrations followed the order as: PPDPs (6.48–17.39) > PPDQs (5.86–12.14) > PPDHQs (0.16–1.35 μg/g). SignificanceThe high concentrations and potential toxicities indicate that these PPDQ/Ps could seriously threaten the eco-environment, as they may finally enter the environment, accordingly requiring further investigation. The analysis strategy and data-processing algorithm can be extended to nontarget analysis for other zwitterionic pollutants, and the analysis results provide new understandings on the environmental occurrence of PPDQ/Ps from source and overall perspectives.

Reconstruction after inappropriate lower limb open degloving injury management resulting in the necrotic wound: a case report

Background: Trauma with shear mechanisms, which are typically the result of after trauma regarding traffic incidents, is the primary cause of degloving injuries. The condition is typified by the avulsion of skin and subcutaneous tissue, resulting in a deficiency in coverage and, in extreme situations, the loss of the limb involved. Case Presentation: A 58-year-old male was struck by a car and sustained a direct blow to his right lower leg from a rubber tire. The patient was hospitalized and did primary wound closure. A week later, the patient sought a second opinion in a different hospital due to necrotic tissue formation in his lower limb due to previous primary closure disregarding tissue vitality through split-thickness skin excision (STSE). Conclusion: This case reported management of necrotic tissue and reconstruction defect closure by skin graft through surgical cleaning and debridement. After establishing a viable grafting bed, split-thickness skin grafts were applied as covering.

Mind your tyres: The ecotoxicological impact of urban sediments on an aquatic organism

The presence of tyre and road wear particles (TRWP) in the environment is an underestimated threat due to their potential impact on ecosystems and human health. However, their mode of action and potential impacts on aquatic ecosystems remain largely unknown. In the present study, we adopted a sediment exposure scenario to investigate the influence of sediment coming from an urban runoff sedimentation basin on the life cycle of Chironomus riparius. Targeted broad-spectrum chemical analysis helped to characterise the urban sediments and confirmed the significant contribution of contaminants from traffic (e.g. tyre wear contribution, Polycyclic Aromatic Hydrocarbons [PAHs], metals, tyre rubber additives). First-stage chironomid larvae were subjected to increasing concentrations of urban whole sediment. The results showed that exposure to this urban sediment influenced all measured endpoints. In vivo quantification of ROS showed that larvae exposed to the lowest concentration of contaminated sediment exhibited increased fluorescence. The contaminated sediment conditions increased mortality by almost 30 %, but this effect was surprisingly not concentration-dependent. Fertility decreased significantly and concentration-dependently. The results of the Mean Emergence Time (EmT50) and larval size showed an optimality curve. Furthermore, as a consequence of the effects on fitness, the Population Growth Rate (PGR) exhibited a significant decrease, which was concentration-dependent. Therefore, after a single generation, PGR calculation can be adopted as a sensitive tool to monitor pollution caused by complex matrices, i.e. composed of several contaminants. Our research highlights the importance of effective management of road runoff and underlines the need for further investigation to better understand the toxicity of TRWPs.

Development of a sustainable polymer composite: enhancing properties of waste plastic with ground tire rubber reinforcement

The growing interest in utilizing waste for composite development has prompted investigations across social, economic, and environmental domains. This study focuses on utilizing recyclable waste plastic materials and micro-sized ground tire rubber (GTR) of varying sizes (600 μm, 300 μm, and 150 μm) to create a polymer matrix composite (PMC). Employing a thermal blending technique, the manufacturing process adjusts the composition ratios of polymer and GTR from 90:10 to 50:50. Subsequently, Energy Dispersive Spectroscopy (EDS) is utilized to analyze the PMC composition, while Fourier-transform infrared spectroscopy confirms functional group and chemical structure. The study demonstrates significant improvements in various properties upon adding GTR to High-Density Polyethylene (HDPE) and Low-Density Polyethylene (LDPE) composite materials. For HDPE-GTR composites, the melting temperature (Tm) ranged from 120.29 °C to 138.53 °C, crystallization temperature (Tc) from 102.84 °C to 127.14 °C, and enthalpy of melting (ΔHm) from 70.96 to 139.67 J g−1. Crystallinity (Xc) varied from 48.43% to 52.96%. In LDPE-GTR composites, Tm ranged from 106.08 °C to 129.57 °C, Tc from 90.27 °C to 112.20 °C, ΔHm from 75.59 to 142.53 J g−1, and Xc from 51.59% to 54.05%. Moreover, mechanical properties such as tensile strength, flexural modulus, and impact strength exhibited enhancements with GTR addition to the polymer matrix. These findings underscore the potential of sustainable waste utilization, advancing environmentally friendly and resource-efficient composite materials.

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.

Quantitative analysis of multicomponent mixtures of rubber and additives based on terahertz time-domain spectroscopy and Krawtchouk moments

This paper presents a quantitative analytical method based on terahertz time-domain spectroscopy and chemometrics, which was used to detect the content of diphenyl-p-phenylenediamine in a five-component mixture comprising tire rubber and additives. We separately extracted the features of the spectra by using principal component analysis and Krawtchouk moments, and then used partial least squares regression and support vector regression to develop quantitative analysis models. The experimental results show that support vector regression outperforms partial least squares regression in the quantitative analysis of multicomponent mixtures, and the Krawtchouk moments method effectively enhances the prediction accuracy of the model. The Krawtchouk moment combined with support vector regression model shows excellent predictive ability. The correlation coefficient and root mean square error of Krawtchouk moment combined with support vector regression model for the calibration set were 0.9749 and 1.7256%, respectively, and for the prediction set were 0.9669 and 1.9777%, respectively. The results demonstrate that terahertz time-domain spectroscopy combined with Krawtchouk moments and support vector regression is an effective method for determining the antioxidant content in rubber and additive compounds.

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.

Pemanfaatan Penambahan Limbah Inner-Tube Rubber dan Penggunaan Abu Cangkang Kemiri Sebagai Substitusi Filler pada Campuran AC-WC

Various problems that occur in asphalt damage in Indonesia have triggered new innovations to deal with existing problems, one of which is by improving the quality of asphalt by adding substances (additives) or substitutions to the aggregate composition. This study aims to determine the utilization of inner tube rubber waste and the use of candlenut shell ash as a substitute filler in the AC-WC mixture. This study is an experimental study. The manufacture of test objects using an AC-WC mixture with a total of 18 test objects was then tested using the Marshall method. The results of this study indicate that the use of inner-tube rubber waste and candlenut shell ash greatly affects the Marshall parameter value. With an Optimum Asphalt Content of 6%, the best variation content was obtained at 3% of inner tire rubber additives and 25% substitution of candlenut shell ash as filler with a density value of 2.341 gr/cm3, VMA 15.50%, VIM 4.36%, VFA 71.87%, stability 1730.79 kg, flow 3.36 mm and MQ 565.01 kg/mm ​​which meets the 2018 Bina Marga Specifications Revision 2.

Mechanical strength of rubberized concrete: Effects of rubber particle size, content, and waste fibre reinforcement

Concrete production, ubiquitous in global construction, exerts significant environmental strain, notably through cement manufacturing's carbon footprint and natural sand depletion. As a response, researchers are exploring eco-friendly alternatives, including Waste Tyre Rubber (WTR) aggregates which replace natural sand in concrete. This study investigates the impact of WTR particle sizes (ranging from 0.2 to 4 mm) and volumetric replacements (0–54 %) on Rubberised Concrete Mortar (RuCM) and Rubberised Concrete (RuC) mechanical properties. Additionally, Waste Tyre Steel Fibre (WTSF) reinforcement effects (volume dosage between 0 % and 3 %) are examined and compared with Commercial Steel Fibre (CSF). The study optimizes RuCM and RuC mixes via particle packing theory, incorporating Ground Granulated Blast Furnace Slag (GGBS) and Fly Ash (FA) as cement replacements. Mechanical tests reveal the compressive and flexural strength reduces with an increasing WTR dosage, attributed to the inherent softness of WTR and the weak interfacial bonding between WTR particles and surrounding matrix. Utilizing an optimized RuC mixture with a 10 % WTR replacement yields substantial mechanical improvements, showcasing a remarkable 195 % surge in compressive strength and a noteworthy 61 % elevation in flexural strength over conventional concrete (CC). However, when compared to the control mix devoid of rubber replacement, there is a modest reduction of 16 % in compressive strength and 4 % in flexural strength. Moreover, the incorporation of WTSF reinforcement proves beneficial in mitigating compressive strength losses post rubber particle inclusion and brings about a substantial increase in flexural strength with 3 % volumetric additions. Quantitative analysis reveals the reinforcement effect from WTSF is comparable to the effect of CSF reinforcement. These findings underscore the intricacies and potential opportunities in harnessing WTR and WTSF for the development of resilient and sustainable concrete formulations.

Distinct Species-Specific and Toxigenic Metabolic Profiles for 6PPD and 6PPD Quinone by P450 Enzymes: Insights from In Vitro and In Silico Studies.

The tire rubber antioxidant N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (6PPD) and its quinone product (6PPDQ) are prevalent emerging contaminants, yet their biotransformation profiles remain poorly understood, hampering the assessment of environmental and health risks. This study investigated the phase-I metabolism of 6PPD and 6PPDQ across aquatic and mammalian species through in vitro liver microsome (LM) incubations and in silico simulations. A total of 40 metabolites from seven pathways were identified using the highly sensitive nano-electrospray ionization mass spectrometry. Notably, 6PPDQ was consistently detected as a 6PPD metabolite with an approximate 2% yield, highlighting biotransformation as a neglected indirect exposure pathway for 6PPDQ in organisms. 6PPDQ was calculated to form through a facile two-step phenyl hydroxylation of 6PPD, catalyzed by cytochrome P450 enzymes. Distinct species-specific metabolic kinetics were observed, with fish LM demonstrating retarded biotransformation rates for 6PPD and 6PPDQ compared to mammalian LM, suggesting the vulnerability of aquatic vertebrates to these contaminants. Intriguingly, two novel coupled metabolites were identified for 6PPD, which were predicted to exhibit elevated toxicity compared to 6PPDQ and result from C-N oxidative coupling by P450s. These unveiled metabolic profiles offer valuable insights for the risk assessment of 6PPD and 6PPDQ, which may inform future studies and regulatory actions.

Building Chemical Interface Layers in Functionalized Graphene Oxide/Rubber Composites to Achieve Enhanced Mechanical Properties and Thermal Control Capability of Tires.

With the rapid development of the transport industry, there is a higher demand for environmental friendliness, durability, and stability of tires. Rubber composites with excellent mechanical properties, abrasion resistance, and low heat generation are very important for the preparation of green tires. In this study, the all-aqueous phase process was initially employed to prepare 2-Amino-5-mercapto-1,3,4-thiadiazole (AZT) functionalized graphene oxide (AGO). Subsequently, modified graphene oxide/silica/natural rubber (AGO/SiO2/NR) composites were obtained through latex blending and hot press vulcanization processes. This method was environmentally friendly and exhibited high modification efficiency. Benefiting from the good dispersion of AGO in the latex and the cross-linking reaction between AGO and NR, AGO/SiO2/NR composites with good dispersion and enhanced interfacial interaction were finally obtained. AGO/SiO2/NR composites showed significantly improved overall performance. Compared to GO/SiO2/NR composites, the tensile strength (28.1 MPa) and tear strength (75.3 N/mm) of the AGO/SiO2/NR composites were significantly increased, while the heat build-up value (10.4 °C) and DIN abrasion volume (74.9 mm3) were significantly reduced. In addition, the steady-state temperature field distribution inside the tire was visualized by ANSYS finite element simulation. The maximum temperature of the prepared AGO/SiO2/NR was reduced by 18.2% compared to that of the GO/SiO2/NR tires. This strategy is expected to provide a new approach for the development of low energy consumption, environmentally friendly, and long-life rubber for tires.

The mechanism on liquefaction of waste tire by ethanolysis

Thermo-chemical treatment methods are pivotal for effectively managing waste tire rubber (WTR) while promoting energy efficiency and emission reduction. This study investigates the liquefaction of WTR within a thermal ethanol environment, exploring temperature ranges (200–300 °C) and residence times (0–80 min) to discern the role of ethanol in tire degradation. Additionally, the study includes liquefaction experiments with cyclohexane as a solvent to contrast the effect of ethanol, and comparison between ethanol and water to elucidate solvent impact. Results indicate that at 300 °C for 40 min, oil yields peak at 53.05 % for a WTR/ethanol mass ratio of 1:8 and at 51.64 % for a ratio of 1:6, notably surpassing hydrolysis outcomes. By contracting with the results from the liquefaction with cyclohexane as solvent, the involvement of ethanol can facilitate liquid phase products, primarily alkenes and oxygen-containing compounds, attributed to aromatization inhibition. Heavy oils and heteroatomic compounds are characterized through Fourier-transform ion cyclotron resonance mass spectrometry (FT-ICR MS), detecting hydrocarbons and heteroatom compounds like NxOy, Ox, Sx, NxOySz, NxSy, and Nx. Notably, sulfur, a significant pollutant, predominantly manifests as sulfide in chars. These findings offer valuable insights into advancing waste tire recycling technologies.

Tracing the odor source of crumb rubber modified asphalt emissions and evaluating the deodorization effect of attapulgite

Crumb rubber modified asphalt (CRMA) is widely used in road construction due to its excellent performance. However, it generates significant odorous gases during paving. To analyze the odor contribution, both untreated crumb rubber and desulfurized rubber were involved in this study to prepare CRMA and desulfurized rubber modified asphalt (DRMA). Attapulgite was selected as an emission reduction agent to reduce the odorous emissions released from CRMA and DRMA. An indoor fume collection system and gas chromatography-mass spectrometry (GC-MS) analysis were used to trace the odor source and quantify the odorous emissions. A comprehensive olfactory thresholds database for CRMA emissions was further established to evaluate the odor level of various rubberized asphalt binders by using three-point comparative odor bag method, along with known olfactory thresholds of certain compounds reported in the literature. Dynamic shear rheometer (DSR), multiple stress creep recovery (MSCR), bending beam rheometer (BBR) and Brookfield viscosity tests were used to analyze the effect of attapulgite on rheological properties of CRMA and DRMA. Results indicated that odor emission rate of CRMA containing 1 %, 3 %, and 5 % attapulgite was decreased by 42.62 %, 63.29 %, and 71.06 %, respectively. Benzothiazole, derived from tire rubber vulcanization accelerator, can be reduced by 60.25 % with 1 % attapulgite, demonstrating excellent performance in terms of reducing target odor emissions. Although DRMA has a lower emission rate than that of conventional CRMA, the addition of 1 % attapulgite can further reduce the odor emission rate of DRMA by 37.92 %. The addition of attapulgite has less impact on the overall performance of CRMA and DRMA. Besides, it was found that attapulgite can reduce the viscosity of rubberized asphalt binders, which is beneficial for rubberized asphalt mixture paving and compaction. Considering odor reduction, performance, and economic factors, the optimal attapulgite content was determined to be 5 % for CRMA and 1 % for DRMA. This approach successfully reduces odorous emissions while maintaining the desirable properties of CRMA, making it a viable solution for environmentally friendly road construction.

Recyclability and self-healing capability in reinforced ionic elastomers

This study presents a comparative analysis of different sustainable alternatives for producing reinforced ionic elastomers that are not just mechanically robust but also excellent in recyclability and self-healing, marking a significant advancement in sustainable materials science. Ionically crosslinked carboxylated nitrile rubber (XNBR) was combined with conventional (carbon black and silica) and sustainable (cellulose and ground tire rubber) fillers. The sustainable fillers not only enhanced the mechanical performance (reinforcing character) but also maintained high healing efficiencies (>80 %). Notably, the incorporation of just 10 phr of waste-based ground tire rubber (GTR) produced by water jet grinding (WJ-GTR) resulted in a material capable of complete repair and recycling (100 % efficiency) after temperature-driven protocols, with mechanical properties and a reinforcement index comparable to those of conventional fillers such as silica. This achievement represents a major breakthrough in the field of sustainable composites, as it offers a unique blend of robust mechanical properties and environmental sustainability.

Impact of virgin and recycled polymer fibers on the rheological properties of cemented paste backfill

The addition of polymer fibers to cemented paste backfill (CPB) has shown promise in enhancing mechanical properties, although it also introduces changes in rheological characteristics. This study aimed to investigate the influence of different types of polymer fibers, namely virgin commercial polypropylene fiber (CPPF), recycled tire polymer fiber (RTPF), and recycled tire rubber fiber (RF), on the rheological properties of CPB mixtures through an experimental program, and provide design references for CPB pipeline transport. The results revealed consistent reductions in bulk density upon the incorporation of polymer fibers into CPB, alongside varying impacts on slump. Specifically, the addition of CPPF had a mild effect, while RTPF caused a continuous decrease in slump, and RF exhibited minimal influence up to a 4% concentration, with substantial effects thereafter. Moreover, the inclusion of fibers led to increases in apparent viscosity parameters, with RTPF inducing the most significant changes, followed by varying responses from CPPF and RF. When using RTPF for CPB reinforcement, emphasis should be placed on enhancing technical indicators related to viscosity such as energy consumption and pipeline wear during pipeline transport. Furthermore, adjustments were necessary to account for flow curve instability resulting from interactions between fibers and the paddle, with the data aligning well with the Bingham model. The addition of fibers, particularly CPPF and RF, primarily influenced plastic viscosity rather than yield stress, underscoring the limitations of slump tests in assessing rheology.

Synergistic effects of steel fiber and rubberized aggregates on concrete properties

The drive for more sustainable and environmentally friendly construction practices has resulted in revolutionary concrete production methods. One way is to include scrap rubber tires (contributing significantly to environmental pollution) into concrete mixtures to increase deformability. This study investigates the impact of surface-treated waste tire rubber (which partially replaces natural coarse aggregates with 5%, 10%, and 15% by weight) and industrial steel fiber (as reinforcement by including 0.5, 1, and 1.5% volume fractions) in concrete. Twelve concrete mixtures were prepared as test specimens. The replacement percentage was then determined using the compressive strength test results for additional surface treatment with three different alkaline solution (NaOH) concentrations (5%, 10%, and 15%) for 72 h. Thus, the hardened concrete properties were analyzed using compressive strength, flexural strength, and toughness; whereas the fresh qualities of equivalent concrete mixtures were evaluated using concrete slump. The findings revealed that, while partial replacement had a negative impact on the mechanical properties of the concrete, it was possible to produce rubberized concrete with better mechanical properties than conventional concrete when the partial replacement was less than 5%, treated with 10% alkaline solution, and reinforced with 1.5% steel fibers. The study’s findings illustrate the potential of these combinations for use in concrete pavement and slab applications.

Mechanical and microstructural characterization of sustainable concrete containing recycled concrete and waste rubber tire fiber

The production of cement, which is the key ingredient of concrete, leads to environmental pollution by releasing massive amounts of CO2 and using significant natural resources. Therefore, shifting towards sustainable and greener materials is essential for mitigating these challenges. In this study, recycled concrete powder (RCP) was used as a cement replacement (0%, 5.0%, 10%, and 15%), solving the waste dumps issue and promoting sustainability. Furthermore, the concrete is also reinforced with steel fibers which were obtained from waste rubber tires to improve concrete tensile strength. The concrete properties were evaluated through slump cone test, compressive strength, failure patterns, tensile strength, scanning electronic microscopy, and FTIR analysis. The results indicate that the concrete strength properties improved with the substitution of RCP. The compressive and tensile strength of the optimum mix (10% RCP and 2.0% addition of steel fibers) are 15.8% and 23% more than those of reference concrete. However, the concrete flow is adversely impacted due to RCP angular particle shapes. Failure patterns indicate that RCP and steel fibers improved concrete ductility. SEM and FTIR analysis indicate microstructural improvement with RCP and steel fibers. Finally, the analysis concluded that the developed concrete showed better performance, solved waste dumps issues, and promoted sustainability.