Rubberized Concrete Research Articles

Tensile strength prediction of crumb rubber concrete based on mesoscale modelling

ABSTRACT This study presents an experimental study and a mesoscale model for evaluating the tensile performance of crumb rubber concrete (CRC). In the experimental study, indirect tensile strengths of CRC with 6%, 12% 18% rubber contents were tested. Then the tested CRC samples were modelled as a five-phase material containing rubber, coarse aggregate, mortar, aggregate-mortar interface layer, and rubber-mortar interface layer. Numerical results from the mesoscale model agreed well with experimental tests. Parameter analysis was carried out to investigate the content, size, shape of rubber particle, thickness of interface layer on the tensile strength of CRC. Numerical results also indicated that rubber content was the governing influencing factor on the tensile strength reduction. As comparison, the influence from rubber size and rubber shape was relatively low. For a specimen with constant rubber content and size, changes in the distribution of rubber particles resulted in slight changes in the tensile strength of CRC as well. The effect of rubber particles on the tensile properties of concrete was similar to that of pores. Finally, tensile strength prediction formula was developed based on the pores model proposed in this study.

Experimental study on coir fiber based crumb rubber concrete

Experimental study on coir fiber based crumb rubber concrete

Study on static and dynamic mechanical properties and microstructure of silica fume-polypropylene fiber modified rubber concrete

Through tests and micro-observations, the static and dynamic mechanical properties and microstructure of rubber concrete samples modified with varying amounts of silica fume and polypropylene fiber content were explored. The results indicate that incorporation of silica fume and polypropylene fiber can effectively enhance the performance of rubber concrete. Moreover, at 10% and 0.1% of silica fume and polypropylene fiber content respectively, rubber concrete’s compressive strength, splitting tensile strength, flexural strength, and dynamic compressive strength reached maxima. Furthermore, microstructure characteristic analysis indicated that inadequate adhesion between rubber particles and the matrix is responsible for compromised bearing capacity in unmodified rubber concrete. However, with the addition of silica fume and polypropylene fiber, the fiber binds the rubber particles closely with the matrix, while the silica fume fills the gaps between the matrix components. This combination results in rubber concrete with a denser internal structure and enhances its bearing capacity significantly.

Development in the Study of Mechanical Prop-erties and Damage Constitutive Models of Rub-ber-Reclaimed Concrete

Advances in rubber-reinforced concrete technology and its applications in engineering are cru-cial for the thorough recycling and safe disposal of waste tire rubber and construction debris. Rubber-reinforced concrete (RAC) is a concrete material produced by substituting some fine and coarse aggregates with waste rubber particles and recycled aggregates. The incorporation of waste rubber particles endows RAC with distinctive mechanical properties and a distinct damage constitutive model. The mechanical properties of rubber recycled concrete mainly in-clude compressive strength, tensile strength, flexural strength, and elastic modulus. Compared to traditional concrete, RAC exhibits slightly lower compressive and flexural strengths but sig-nificantly enhanced tensile strength. This is due to the changes in mechanical properties caused by the softness and elastic properties of rubber particles. In addition, the addition of rubber particles can also improve the energy absorption capacity and impact resistance of concrete. On the other hand, in order to describe the damage behavior of rubber recycled con-crete, some constitutive models were studied. Common models include linear elastic model, plastic model, and damage model. The linear elastic model is suitable for describing the be-havior of rubber recycled concrete during the elastic stage; The plastic model is suitable for describing its deformation behavior during the plastic stage; The damage model can better describe the fracture and failure behavior of rubber recycled concrete, including shear damage, tensile damage, and compression damage. Tailored to the unique characteristics of RAC, these models consider the stiffness of rubber particles and the deformation characteristics of the binding materials, enabling accurate predictions of the stress-strain behavior of RAC. In conclusion, rubber-reinforced concrete possesses excellent mechanical and durability proper-ties, which can be accurately described and predicted using appropriate constitutive models. These findings are crucial for advancing the application and development of rubber-reinforced concrete.

Bond behavior of deformed rebar in concrete containing recycled brick aggregate and waste rubber

The reuse of aggregates and crumb rubber (CR) in concrete is gaining interest globally for reducing the adverse effects on the environment and maintaining construction sustainability. The bond strength of reinforcing rebars in such concrete is one of the key issues to be addressed before their practical application, particularly in structural elements. Pull-out tests were performed on 80 specimens to assess the bond performance of deformed rebars in rubberized recycled brick aggregate concrete (RRBAC). After investigating the strength properties of RRBAC, pull-out tests were performed on two sizes of cylindrical specimens. RBA%, CR%, rebar diameter (d), embedment length (le), and concrete cover-to-rebar diameter ratio (c/d) were among the test variables in this bond behavior investigation. Bond stress-slip relationships were obtained, examined, and average bond strengths were compared with the available codes. Concrete split failure was observed in 79% of the tested specimens, whereas rebar fracture was not seen in any of the tests. The bond strength was found to be decreased with the inclusion of RBAs and CRs though relative improvement was observed for higher percentage RBAs. Additionally, regression analysis was performed on the experimental data to produce a closed-form equation for forecasting the bond strength for RRBAC. With a strong coefficient of determination (R2 = 0.97) and low values of error terms, the predicted bond strengths were seen to be a good agreement with the test results.

Enhancing of damping capacity in crumb rubber concrete at various damage levels: Effects of fly ash and ground granulated blast furnace slag

Crumb rubber (CR) incorporated as damping units in concrete, partially replacing natural aggregates, enhances the material's damping capacity. However, the filler type and replacement rate will usually influence the crack development of crumb rubber concrete (CRC) elements under repeated loading, which in turn influences their damping capacity at different damage levels. Thus, the damping characteristics of CRC cantilever beams at different damage levels, influenced by filler type and substitution rate, are investigated in the present paper through low-cycle repeated damage and free vibration tests. The results reveal that partial cement replacement with fly ash (FA) significantly enhances the energy dissipation capacity, especially at a 30 % FA replacement rate. Positive effects on the damping ratio are observed only when the ground granulated blast furnace slag (GGBFS) substitution rate is 30 %. For the CRC cantilever beams both with and without filler, the damping ratio shows an increasing and then decreasing trend with increasing displacement angle. The maximum damping ratio is exhibited when the displacement angle is 0.02. With increasing displacement angle, FA and GGBFS doping accelerated the degradation rate of the bending dynamic stiffness and the damage index rose faster. A model is formulated to describe the correlation between the damping ratio and the damage index in CRC cantilever beams both with and without filler. The effect of filler incorporation on the pores and microcracks may be the main reason for the damping ratio increase as observed by micro-morphology.

Enhanced nonlinear models for critical compressive stress-strain characteristics of rubberized concrete: Comprehensive experimental data and robust evaluation methodology

The integration of rubber aggregate (RA) into concrete presents a pivotal avenue for enhancing the material's sustainability and environmental impact. Despite its potential, a crucial gap persists in the field concerning the development of material models that accurately consider the influence of RA particle size on the stress-strain responses of Rubberized Concrete (RuC). To address this gap, this study explores the effects of incorporating RA into concrete on its ascending compressive stress-strain behavior. In this research, we have compiled a comprehensive database encompassing the compressive stress-strain characteristics of 80 distinct concrete mixes incorporating RA from varied sources, sizes, and attributes. The investigation also evaluated the effectiveness of recent models in predicting key parameters, including modulus of elasticity, peak stress, and strain at peak stress. We proposed more robust models to accurately capture essential features. Notably, the findings suggest that higher RA content leads to dispersed cracks and decreased stiffness, resulting in lower peak stress and strain. Moreover, compressive strength exhibits notable variations with RA content, with significant drops observed across both normal and high-strength concrete mixes. The performance evaluation of existing models underscores the superiority of Li et al.'s model for peak stress prediction and Abbara et al.'s model for elasticity modulus prediction. The proposed simplified nonlinear models in this research offer enhancements over existing ones, promising more accurate predictions. These findings have profound implications for the optimization of rubberized concrete mixes and pave the way for future research directions aimed at further refining predictive models and advancing the application of RA in concrete technology.

Experimental and Numerical Evaluation for Hybrid Reinforced T-Beam with Different Ratios of Recycled Rubberized Concrete

The use of hybrid GFRP and steel bars as main reinforcement increases the flexural capacity of T-section concrete beams and reduces ductility. Adding recycled rubber to the concrete mix would further enhance the ductility of the hybrid system. Evaluation of the concrete's flexural capacity and ductility is the main goal of the current investigation using normal concrete (NC) and rubberized recycled concrete (RRC). Eight T-beams have been experimentally investigated in this research, two beams were reinforced with steel bars and GFRP bars with zero percentage of crumb rubber (C.R). The remaining beams were reinforced with different combinations of GFRP and steel bars with rubberized concrete mixes with partial substitution of sand with recycled crumb rubber by (0%, 7.5%, 10%, and 12.5% replacements by volume) particle size 1.0 to 2.0 mm. The ductility index for the tested hybrid rubberized T-beams (HRTB) BRH1, BRH3a, BRH5, BRH2, BRH4, and BRH6, were higher than BH1 and BH2 by 28.2%, 35.47%, 65.38%, 23.76%, 30.04%, and 56.95% indicating that increasing the percentage of C.R. has a direct effect on increasing the ductility index. The ultimate failure load for the tested HRTB BRH1, BRH3a, and BRH5, decreased by 11.68%, 14.29%, and 17.47% compared to the hybrid T-beam BH1. The energy dissipation decreased for HRTB BRH1, BRH3a, BRH5, BRH2, BRH4 and BRH6 by 7.88%, 12.36%, 17.17%, 8.12%, 12.96%, and 18.28 compared to hybrid T-beams BH1 and BH2. This indicates that the existence of the very weak C.R. was not able to dissipate the energy properly within the concrete matrix. Good agreement was found between the numerical model and experimental results in terms of crack pattern, ultimate loads and deflections.

Durability and Recycling of Rubber Concrete

The addition of crumb rubber particles causes a decrease in the compressive strength of concrete. This is particularly observed beyond 3.6% crumb rubber addition with respect to the total weight of the aggregates. The accelerated carbonation also indicates an increase in the CO2 ingress, which is partially due to the low quality of the interface rubber particles-cementitious matrix. On the other hand, the water sealant properties, the chloride penetration resistance and the resistance to freeze and thaw exhibit an increase. This latter feature is mainly due to the implemented ductility of the crumb rubber concrete, which can better adapt to the thermal stress that arises during the freezing action. Furthermore, the addition of recycled crumb rubber up to 25% of the aggregate weight to concrete positively affect the mechanical as well as the durability performance.

Fatigue Damage of Rubber Concrete Backfill at Arch Springing Influence on Surrounding Rock Deformation in Tunnel Engineering

The backfill area of tunnel projects may deform or collapse due to the cyclic disturbance of groundwater and train loads. Hence, the anti-deformation and crack resistance performance of backfill materials under cyclic disturbance is critical to engineering safety. In this paper, concrete was produced by mixing 0.85 mm, 1–3 mm and 3–6 mm rubber particles instead of 10% sand, and tested to discuss the effect of rubber particle size on the deterioration of concrete material properties (compressive characteristics and energy dissipation) after bearing cyclic loading. The stress–strain curve and various parameters obtained through the uniaxial compression test and cyclic load test were used to explore the optimal grain size that can be applied to the tunnel engineering backfill area, and numerical simulation was adopted to calculate the deformation of the surrounding rock and the structural stress of different backfill materials. Research shows that the increase in particle size lessens the compressive strength, deformation resistance and cracking resistance of specimens, but after the cyclic loading test, the concrete material deterioration analysis indicates that rubber concrete has lesser and more stable losses compared to ordinary concrete, so the optimum rubber particle size is 0.85 mm. Numerical calculations show that RC-1 reduces the arch top displacement by 0.4 mm, increases the arch bottom displacement by 0.6 mm and increases the maximum principal stress by 11.5% compared to OC. Therefore, rubber concrete can ensure the strength and stability requirements of tunnel structures, which can provide a reference for similar projects.

Studies on Concrete Replaced with Waste Tyre Rubber as Fine Aggregate

Concrete is one of the most extensively used construction material in the world and the mineral aggregates used to make the concrete are a finite resource, which is fast dwindling. On the other hand, Waste tyre treatment is now a serious global threat. Waste tyre dumping, disposal of these materials or burning these tyres cause serious environmental and health problems. The public, governments and industry are all greatly interested in green environment and engineering approaches towards better sustainable development. At the same time, these studies can help to make the environment clean and minimize waste. An emerging use is the production of concrete, in which rubber tyre particles Partially replace natural coarse aggregates. One of the solutions suggested is the use of tyre rubber aggregates as additive in cement based material. Waste tyres are cut into small pellets of size matching the nominal aggregate size and are used to replace the coarse aggregate used in concrete. For comparative analysis, concrete mix of M20 grade is prepared for various concrete mixes by varying percentage replacement of mineral coarse aggregates by 4, 6, and 8 rubber aggregates and the mechanical properties of rubber concrete are compared with that of conventional concrete. Different combinations of crumb rubber with traditional coarse aggregate were evaluated based on compression strength and flexural strength tests were conducted according to Indian Standard.

Effect of titanium dioxide as nanomaterials on mechanical and durability properties of rubberised concrete by applying RSM modelling and optimizations

The use of rubber aggregates derived from discarded rubber tyres in concrete is a pioneering approach to replacing natural aggregate (NA) and promoting sustainable building practices. Recycled aggregate in concrete serves the dual purpose of alleviating the accumulation of discarded rubber tyres on the planet and providing a more sustainable alternative to decreasing natural aggregate. Due to fact that the crumb rubber (CR) decreases the strength when used in concrete, incorporating titanium dioxide (TiO2) as a nanomaterial to counteract the decrease in strength of crumb rubber concrete is a potential solution. Response Surface Methodology was developed to generate sixteen RUNs which contains different mix design by providing two input parameters like TiO2 at 1%, 1.5%, and 2% by cement weight and CR at 10%, 20%, and 30% as substitutions for volume of sand. These mixtures underwent testing for 28 days to evaluate their mechanical, deformation, and durability properties. Moreover, the compressive strength, tensile strength, flexural strength and elastic modulus were recorded by 51.40 MPa, 4.47 MPa, 5.91 MPa, and 40.15 GPa when 1.5% TiO2 and 10% CR were added in rubberised concrete after 28 days respectively. Furthermore, the incorporation of TiO2 led to reduced drying shrinkage and sorptivity in rubberized concrete, especially with increased TiO2 content. The study highlights that TiO2 inclusion refines pore size and densifies the interface between cement matrix and aggregate in hardened rubberized concrete. This transformative effect results in rubberized concrete demonstrating a commendable compressive strength comparable to normal concrete.

Effect of the Inorganic Modification Mode on the Mechanical Properties of Rubber Recycled Concrete.

The reasonable and effective application of waste tires and discarded concrete in concrete is an important branch of green concrete development. This paper investigates the effects of the inorganic modification mode on the basic mechanical properties of rubber recycled concrete based on indoor tests. Inorganic modification, such as water washing, acid washing, and alkaline washing modification, was mainly used to treat and modify rubber particles. The factors affecting the compressive strength, the splitting tensile strength, the flexural strength, the axial compressive strength, and the modulus of elasticity of modified rubber recycled concrete were analyzed. The study results show that the incorporation of recycled aggregates and rubber reduced the mechanical properties of concrete, with the compressive and splitting tensile strengths showing the greatest reductions of 27.36% and 27.24%, respectively. Three modification methods significantly improved the mechanical properties of rubber recycled concrete. The alkali washing modification method was the most effective, maximally improving the mechanical properties of rubber recycled concrete by 7.53-15.51%. The effects of the three modifications on the mechanical properties of concrete were ranked as follows: alkali washing > acid washing > water washing. This study provides a data basis for the practical application of rubber recycled concrete in engineering and a test basis for the development of green concrete.

Experimental study on GFRP-steel double-skin rubber concrete composite piers under mixed loading

To address the issues related to the insufficient compressive and shear strength of rubberized concrete and to enhance the deformation capacity and longevity of composite piers, a novel approach involving the confinement of rubberized concrete with glass fiber-reinforced polymer (GFRP) tube and steel tube has been proposed. This method aims to create a GFRP-steel double-skin rubberized concrete composite pier. Pseudo-dynamic and quasi-static tests were conducted on the composite pier to assess its seismic response and residual seismic performance. The study investigated the failure mode, hysteretic characteristics, ductility, energy dissipation, stiffness, and self-centering capability of composite piers. Additionally, a correction coefficient for the equivalent plastic hinge length was proposed. The results indicate that the specimen maintains its elastic state when subjected to frequent seismic events. However, when subjected to infrequent seismic events, the glass fiber layer may fracture, leading to the development of white stripes, while the steel tube experiences yielding, transitioning into a plastic state. The shock absorption and toughness of rubberized concrete were effectively utilized when subjected to horizontal low cyclic loading, thereby mitigating the appearance of more pronounced damage in seismic-damaged specimens. The hysteretic curve was complete, demonstrating a significant energy dissipation capacity. This confirmation indicates that the composite pier can be a viable solution for sea-crossing bridges and complex environments.

Examining the effects of nano iron oxide on physical and mechanical characteristics of rubberized concrete

Examining the effects of nano iron oxide on physical and mechanical characteristics of rubberized concrete

Mechanical Performance of Steel-Fiber-Incorporated Rubberized Concrete for Rigid Pavement Applications

Sustainable solutions are required to mitigate waste tire accumulation. Using rubberized concrete (RuC) in rigid pavements is a viable and relatively environmentally friendly strategy for partially replacing fine/coarse aggregates with crumb rubber. However, crumb rubber affects the mechanical properties of concrete. Although RuC is more flexible (ideal for road pavements) than conventional concrete, its strength is lower than that of the standard concrete used in rigid pavements. Consequently, the crumb rubber generated from discarded tires cannot be used sustainably. The primary objective of this study was to characterize RuC mixed with manufactured steel fibers to improve the strength of the mixture. Fine aggregates (sand) were partially substituted with various proportions (10%, 20%, and 40%) of crumb rubber (size:1.70–2.36 mm) while incorporating 0.5% steel fibers (by volume). The compressive strength, splitting tensile strength, and flexural strength of the concrete deteriorated with increasing rubber content, consistent with the previously reported results. However, steel fiber incorporation improved the mechanical behavior of RuC, thus enhancing the compressive strength, splitting tensile strength, and flexural strength of the pavement structure. The developed steel-fiber-incorporated RuC design enhances the usability and economic value of RuC as well as minimizes the adverse environmental impact of concrete pavement technology.

Properties and stress-strain curve of rubberized concrete cast with uncoated or pre-coated rubber with cement/waste materials

Replacement of fine aggregate with crumb rubber (CR) in concrete manufacturing has become necessary to reduce environmental problems resulting from the traditional disposal of waste tires and to produce environment-friendly concrete. The main problem resulting from incorporating CR into the concrete industry remains the reduction in the properties of concrete. Various methods have been employed to treat CR particles to enhance the overall performance of crumb rubber concrete (CRC). Nevertheless, most of the suggested treatment techniques exhibited little efficacy in improving the characteristics of CR particles, and certain chemical treatments pose risks and hazards to the environment. This work presents a novel method for pre-treating CR particles before their use in CRC. The methodology involves the utilization of several processing materials, including cement (C), supplemental cementitious materials (SCM) such as fly ash (FA), and waste materials such as marble powder (MP). Seventeen different mixtures in terms of rubber replacement ratios and rubber processing methods were prepared for the experiment. One mix served as the control without any addition of CR. Four mixtures were generated by substituting varying proportions (5%, 10%, 15%, and 20%) of sand with untreated CR, measured by weight. The remaining twelve mixes contain treated CR with C, FA, and MP. This study investigated the fresh and mechanical properties of CRC, as well as the overall behavior of the stress-strain curve, including yield, peak, ultimate strain, toughness, modulus of elasticity, and strain ductility. The findings indicated that pretreatment of CR with one of the proposed materials enhances the overall behavior of CRC, especially using FA, compared to untreated. The substitution of fine aggregate with 20% CR treated with FA significantly improved the overall properties of CRC. The compressive strength, splitting tensile strength, peak stress, modulus of elasticity, and toughness rose by 22%, 21.30%, 31.19%, 5.30%, and 37%, respectively, compared to using the same proportion of untreated rubber. Therefore, this type of treatment can be relied upon to improve the properties of CRC and give acceptable results.

Effect of mix dosage on rubberized concrete mechanical performance: A multivariable prediction model towards design provisions

The accumulation of end-of-life tires generates significant environmental/economic/social problems worldwide; however, these tires can potentially be used in engineering applications when recycled as crumb rubber (CR). One possibility is to use CR as a replacement for river sand in concrete to reduce the disposal of CR and the use of sand as well as to improve some of concrete’s properties, such as thermal performance and carbon footprint at the expense of some compressive strength reduction. In this study, a novel and simple multivariable model was developed to predict the compressive strength reduction of rubberized concrete (RC) based on a dataset of 287 concrete mixtures from 38 different studies. The approach used in this study quantified the significance of the impact of 10 mix design variables on the evaluation of compressive strength reduction. The final model proposed in this paper considers six explanatory variables (i.e., volume replacement of sand by CR, CR quantity, fine aggregate quantity, coarse aggregate quantity, cement quantity, and water quantity) to predict the compressive strength reduction in which a logarithmic transformation was implemented to achieve a more precise model. The proposed model reached a coefficient of determination of 0.89, significantly better than other existing models with which the proposed model was compared, resulting in a highly accurate and yet easy-to-implement model. Finally, practical design considerations were provided to be used in concrete mix design or the design of minor structural elements.

Multi-scale analysis and structural application of the synergistic enhancement effect of silane coupling agent on the interface between PVA/rubber and cement

This study employs polyvinyl alcohol (PVA) fibers and silane coupling agent (SCA) to augment rubberized concrete mechanical prowess. A multiscale investigation delves into the synergistic enhancement mechanism of SCA on the interfaces of PVA/cement and rubber/cement, considering macroscopic mechanical properties, microscopic structural characteristics, and nanoscale interface interactions. Initially, fundamental mechanical performance tests reveal a notable enhancement in compressive and flexural strength with the inclusion of SCA and PVA fibers in rubberized concrete. Subsequently, observations of corresponding composite concrete slices are conducted using scanning electron microscopy (SEM), X-ray diffraction (XRD), and Fourier-transform infrared spectroscopy (FT-IR). The results manifest gel and polymer filling interface gaps, with SCA fostering a tighter amalgamation of the two interfaces, effectively rectifying interface defects and elucidating its bonding effects at the microscopic interface. Molecular dynamics (MD) modeling and simulation analyses of PVA/C-S-H and rubber/C-S-H, pre- and post-SCA modification, demonstrate that SCA mitigates interface effects, reinforcing hydrogen bonding, van der Waals interactions, Ca-H coordination bonds, and stability. This augmentation enhances interface adhesion energy, fortifying the weak interface bonding between PVA fibers, rubber, and inorganic silicate (C-S-H). Ultimately, portal frame experiments substantiate that incorporating fiber rubberized concrete into structures not only fails to diminish but marginally enhances the load-bearing capacity of the framework. This research furnishes concrete and innovative solutions for sustainable development while providing a valuable reference for the future application of PVA fiber rubberized concrete materials in practical engineering endeavors.

Enhancing the Strength and the Environmental Performance of Concrete with Pre-Treated Crumb Rubber and Micro-Silica

Dumped non-biodegradable tires present a significant environmental threat, with overflowing landfills and associated health risks highlighting the urgency of tire waste disposal. Current disposal methods, such as stacking tires in open spaces, exacerbate the problem. The large-scale recycling of tire rubber waste offers environmental benefits. This study examines the effects of pre-treatment using NaOH and micro-silica as a mineral admixture on the mechanical strength of crumb rubber concrete (CRC) with partial replacement of natural sand. Samples of M20 and M30 grade were prepared with varying levels of crumb rubber (CR) replacement and evaluated at 28 days. CRC prepared with pre-treated NaOH solution and micro-silica showed improved workability and strength compared to conventional concrete and untreated CRC, with the highest strength observed for 5% CR replacement using micro-silica. Predictive models and micro-structural analysis validated these findings. Life Cycle Assessment (LCA) using OpenLCA v2.10 software and the ecoinvent database revealed that incorporating micro-silica into CRC did not significantly increase environmental impacts, compared to conventional concrete across different mixes.