Rubber Particle Content Research Articles

Quantitative statistical analysis of the crack propagation and fracture process of self‐compacting rubber concrete based on acoustic emission

In this study, acoustic emission (AE) was used to monitor the whole process of tensile and fracture of the self-compacting rubber concrete (SCRC) under four-point bending. The AE activities of SCRC during the stretching and fracture process were analyzed by statistical methods to correlate the process of crack propagation with changes in mechanical properties. And by comparing the tensile and fracture properties, the change patterns of crack mode, the cumulative events and energy of AE in the bending process of SCRC with different rubber particles content, the influence of the incorporated rubber particles on the propagation of microcracks, and the macroscopic fracture mechanism were analyzed. Studies showed that with the incorporation of rubber particles, the ductility of the concrete before and after cracking was improved. Due to the weak bonding surface between the rubber particles and the matrix, the microcracks began to propagate at low-stress levels and developed steadily throughout the stretching process. As the rubber content increased, more rubber components participated in the tensile and fracture process. Because of the elastic stretching of rubber particles, the tensile deformation capacity and fracture properties of the concrete have been improved. And in the whole process of tensile and fracture, the cracking of the weak cemented surface of the matrix and the pulling of the rubber particles were more likely to cause shear mode cracks.

Experimental study on the erosion resistance of rubberized cement-soil

This study examines the effects of granular rubber on the erosion resistance of Cement Soil (CS). Rubber powder was incorporated into CS where the Cement Content Ratios (CCR) of the samples were 10%, 15%, 20% and 25% at five different Rubber Particles Content Ratios (RCR) of 0%, 5%, 10%, 15% and 20%. The main tests included Erosion test, Permeability test and Crystallization test, and theses test results were used to analyze the influence and mechanism of rubber particles on the erosion resistance of CS. Under the action of NaCl and Na2SO4 solutions, the mass and unconfined compressive strength of rubberized cement soil (RCS) went up first, and then decreased with the increase of RCR. When the CCR is more than 20%, the increase of CCR has no obvious effect on the strength after the erosion process. The compressive strength was stronger with bigger size of the rubber particles. Under the same depth, the chloride ion content of RCS decreased with the increase of RCR. When the RCR is more than 15%, there is no significant effect on the erosion resistance with adding more rubber particles in CS. The reasons for increasing of erosion resistance of RCS can be summed up into three aspects: blocking capillary action, elastomer action and preventing crack propagation action. The effect of elastomer delays the time of cracks developing of CS. From the SEM test, it can be observed that the rubber powder hindered the development of micro-cracks since it offered adequate restraint to prevent the shorter cracks from propagating. All the above results show that rubber powder can effectively improve the erosion resistance of cement soil.

Research on strength distribution of natural pumice concrete based on precast porosity

In this study, the rubber natural pumice concrete was taken as the research object, and the orthogonal test method was employed to design the experiment, the rubber particles were added to the concrete as precast pores to test the actual porosity, compressive strength and splitting tensile strength of the natural pumice concrete under different precast porosities. According to the change rule, the actual porosity, compressive strength and split tensile strength distribution were respectively fitted. The results show that there is a good correlation between the actual porosity of natural pumice concrete and the precast porosity, and then the empirical formula of rubber particle content and concrete strength is established, which provides a certain theoretical reference for the research on the porosity of natural pumice concrete.

Pavement and Noise Reduction Performance of Open‐Graded Asphalt Friction Course Improved by Waste Tire Crumb Rubber

To further reveal the road performance and noise reduction performance of open‐graded friction course (OGFC), the crumb rubber prepared by adding waste tires were considered, and the performance requirements of the material were put forward. To avoid the influence of rubber particle swelling on aggregate, the special gradation and mix proportion of OGFC mixture were designed, and the particle size of 4.75 mm was proposed as the control size. The test results show that the aggregate forms a good embedded structure. The resilient modulus, deformation performance, and fatigue performance of R‐OGFC asphalt mixture with different crumb rubber contents were studied. According to the test results, the rubber particle content under the best road performance and noise reduction effect was proposed. The results show that, after adding a certain amount of crumb rubber, the performance of asphalt mixture has been greatly improved, especially the dynamic stability has been improved by 84%. Although the resilient modulus has decreased by 10%, the creep performance has decreased by 37%, and the fatigue life has decreased by 31% (2% rubber content), the noise reduction can reach 3.6–8.6 dB, and the noise reduction performance is significant. This shows that the best content of rubber particles is between 1.5% and 2%, and the R‐OGFC mixture modified by rubber has a good application prospect.

The influence of equal amplitude high stress repeated loading on the mechanical and deformation characteristics of rubber concrete

The reuse of waste rubber in concrete has become one of the focuses of environmentalists and researchers in recent years. Rubber concrete pavement is often deformed and damaged by the repeated loading of vehicles. In this paper, a series of experiments are carried out on the deformation of rubber concrete (RC) during equal amplitude repeated loading. It is discussed that the effect of rubber particle size (0.85 mm, 1–3 mm and 3–6 mm) and content (0%, 5%, 10%, 15% and 20%) of RC on the uniaxial mechanical properties and the total strain, elastic strain and plastic strain during repeated loading. The results show that with the increase of rubber content and particle size, the compressive strength and elastic modulus of concrete decrease. After 50 times of repeated loading, the decrease of compressive strength of RC is generally higher than that of NC, but The decrease in elastic modulus is lower than that of NC, which shows that the addition of rubber can slow down the loss of elastic modulus, and the decrease of elastic modulus first decreases and then increases with the increase of particle size and content. During repeated loading, the curves of total strain, elastic strain and plastic strain of RC are significantly higher than those of NC, which indicates that RC has larger deformation and elasticity, but the relative strain range is smaller than NC, showing better stability. The mechanical properties of each group of concrete are evaluated by the analysis of efficiency coefficient, the scoring order of each group is RCA-1 > RCA-2 > RCB-2 > RCA-4 > RCA-3 > RCC-2 > NC. The results show that the best content of rubber is 5%, and the best particle size is 0.85 mm.

A New Composite Slab Using Crushed Waste Tires as Fine Aggregate in Self-Compacting Lightweight Aggregate Concrete.

A composite slab comprised of self-compacting rubber lightweight aggregate concrete (SCRLC) and profiled steel sheeting is a new type of structural element with a series of superior properties. This paper presents an experimental research and finite element analysis (FEA) of the flexural behavior of composite slabs consisting of SCRLC to develop a new floor system. Four composite slabs specimens with different shear spans (450 mm and 800 mm) and SCRLC (0% and 30% in rubber particles substitution ratio) are prepared, and the flexural properties including failure modes, deflection at mid-span, profiled steel sheeting, and concrete surface stain at mid-span and end slippage are investigated by four-point bending tests. The experimental results indicate that applying SCRLC30 in composites slabs will improve the anti-cracking ability under the loading of composite slabs compared with composite slabs consisting of self-compacting lightweight aggregate concrete (SCLC). FEM on the flexural properties of SCRLC composites slabs show that the yield load, ultimate load, and deflection corresponding to the yield load and the ultimate load of composite slabs drop as the rubber particles content increases in SCRLC. The variation of SCRLC strength has less impact on the flexural bearing capacity of corresponding composite slabs. Based on the traditional calculated method of the ultimate bending moment of normal concrete (NC) composite slabs, a modified calculated method for the ultimate bending moment of SCRLC composite slabs is proposed.

Influence of Rubber Particle Size on Functional Properties of a Composite Material Based on Scrap Tires and a Polymer Binder

Functional properties of composite material based on mechanically grinded scrap tires with different particle size of fractioned crumb and polyurethane type polymer binder were investigated to estimate influence of rubber particles size and content on composite material properties (Shore C hardness, compressive stress at 10 % deformation, tensile strength, elastic modulus and elongation at break, apparent density). Optimization possibilities of composite material consisting of rubber particles with different sizes or fractions were investigated. The obtained results show that variation of composition of the composite material by changing size of rubber granulate have definite influence on selected properties of the material. Purposeful selection and mutual combination of rubber particles size included in material can ensure desirable and predictable mechanical properties of composite material.

Analysis of the Crack Evolution Process in Crumb Rubber Concrete Based on Acoustic Emission Technology

In this study, the crack evolution process of crumb rubber concrete (CRC) in a four-point bending tensile test was monitored using the acoustic emission (AE) technique. The peak frequency, distribution characteristics of the AE source, and the damage process based on the AE ring count during the crack evolution were analyzed. The test results revealed that the addition of rubber particles decreased the brittleness of cracks and improved the ductility of the concrete during the macro-cracking process. The AE positioning method could effectively monitor the evolution process of micro-cracks inside the concrete. Additionally, based on the statistical results of the AE source events and energy distribution, the position of macroscopic cracks could be predicted, and the random distribution of micro-cracks could be characterized. By introducing the Weibull distribution to describe the random growth process of micro-cracks, the damage inside the concrete could be qualitatively predicted. As the rubber particle content increased, the inherent micro-cracks inside the concrete also increased. The damage inside the concrete was biased toward the crack nucleation stage.

Dynamic behavior of sand-rubber mixtures based on hollow cylinder tests

Different additives can be utilized to improve the mechanical behavior of soils including their dynamic properties. Among these additives, crumb rubber, as a recycled material, can provide economic and environmental advantages in addition to the improved mechanical behavior. In this paper, different aspects of dynamic behavior of sand-rubber mixtures were investigated over a wide range of shear strains implementing dynamic hollow cylinder tests. For this purpose, the effects of various parameters including relative density, rubber content, confining stress, and size of rubber particles were studied in detail. The results demonstrated that dynamic properties of sand-crumb rubber mixtures were mainly influenced by rubber content and confining stress values, while relative density and rubber particle size were less effective in this regard. Moreover, it was found that dynamic behavior of the mixtures was completely strain-dependent such that at strain ranges lower than a threshold value, which depended on the applied confining stress, an increase in rubber content led to higher damping ratios, while at strain levels higher than the threshold value a reverse trend was observed.

Study on Dynamic Characteristics of Rubber‐Red Clay Mixtures

Rubber powder formed from discarded tire rubber is mixed with red clay to form a rubber‐red clay mixture. The dynamic triaxial test was carried out on the mixtures under different conditions. The effects of rubber content, rubber particle size, moisture content of mixed soil, compactness, confining pressure, and vibration frequency on shear strain relation, dynamic shear modulus, and damping ratio of the mixture were investigated. The results show that under the same dynamic strain, the dynamic shear stress‐strain curve of rubber mixed soil decreases with the increase in rubber particle content and moisture content and decrease in rubber particle size. On the other hand, it increases with the increase in compactness, confining pressure, and vibration frequency, and as the dynamic strain increases, the τd‐γd curve becomes more nonlinear. In addition, with the increase in the rubber particle content, the dynamic shear modulus decreased while the damping ratio increased. When the content was 2%, the change was fastest. After continued addition, it gradually became stable, and when the decrease in rubber particle size also shows the same pattern, 2.00 mm rubber‐red clay mixture shows better structure. The water content has great influence on dynamic shear modulus and damping ratio of rubber‐red clay mixtures. With the increase in compactness, confining pressure, and vibration frequency, the interaction between mixed soil particles was enhanced, the dynamic shear modulus increased, and the damping ratio decreased.

Analysis of Rubberized Self‐Compacting Concrete under Uniaxial Tension by 3D Mesoscale Models

Damage and failure of rubberized self‐compacting concrete (RSCC) are studied by mesostructural models. The models include six phases: mortar, aggregates, rubber particles, aggregate‐mortar interfacial transaction zones (A‐M ITZs), rubber‐mortar interfacial transaction zones (R‐M ITZs), and voids. Thin layers between mortars and aggregates and between mortars and rubber particles represent A‐M ITZs and R‐M ITZs, respectively. Aggregates and rubber particles are modeled with linear elastic, while mortars, A‐M ITZs, and R‐M ITZs are with different damage‐plasticity behaviors. The mesoscale models are validated by the comparison of numerical results and experimental results. The effects of essential phase parameters on the composite’s strength are evaluated, and empirical laws for these effects are established by data regression. It is demonstrated that the effect of porosity, size, and content of rubber particles affect strength and toughness, which provides guidance to the design of such composites for practical applications.

Damping dissipation properties of rubberized concrete and its application in anti-collision of bridge piers

Rubberized concrete contains crumb rubber as an additional aggregate, serving as a possible solution to deal with waste tires. To investigate the potential of using rubberized concrete as anti-collision cladding of bridge piers, a set of static and dynamic tests and finite element modelling were carried out. First of all, normal concrete and rubberized concrete with different crumb rubber particle sizes and volume fractions were fabricated and tested to obtain its mechanical properties, including compressive strength, elastic modulus and loss factor. Then these mechanical properties were used in three truck-pier collision models established by LS-DYNA. The difference among the three models is the cladding of the pier. One was a single concrete pier without cladding (SP) and the other two were with normal concrete cladding (NC) and rubberized concrete cladding (RC). It is found that with the increase of rubber particle size and content, the compressive strength and elastic modulus decrease but the loss factor increases. Rubberized concrete cladding is suitable for protecting the bridge pier since its high energy dissipation capacity.

An Experimental Study on Mechanical and Thermal Insulation Properties of Rubberized Concrete Including Its Microstructure

This study aimed to investigate the effects of the size and weight content of waste rubber particles on the relevant performances of rubberized concrete. First, the fine aggregates were partially replaced by rubber particles of different sizes to produce rubberized concrete. Secondly, the mechanical and thermal insulation properties of rubberized concrete were investigated. Finally, microstructural analyses of rubberized concrete including scanning electronic microscope (SEM) and energy distribution spectroscopy (EDS) were examined. Experimental results indicated that uniaxial compressive strength of rubberized concrete was reduced, while the peak strain was gradually increased and thermal insulation properties were improved with the increase of rubber content or decrease of rubber particle size. In addition, rubber particles affected the failure modes, endowing concrete with weak brittleness and strong cracking resistance. Additionally, it was observed that the interfacial adhesion between the matrix rubber and the aggregates was weak under SEM, which seemed to be a key factor that reduced the strength of rubberized concrete.

Experimental investigation on the application of recycled tires polymer fibers as a BTEX removal material

Hydrocarbons from BTEX group are dangerous pollutants that can cause a threat to environment and human health. In many cases, their presence in an ecosystem is the result of accidents and petroleum products spills. For this reason, novel, more efficient sorbents are needed for immobilization of such pollutants. This paper presents an experimental study of recycled tires polymer fibers (RTPF) used as a low-cost sorbent for BTEX compounds in soils treated with cement. RTPF are a type of waste that contains polymer fibers with high content of rubber particles. The high porosity and large specific surface area of rubber result in possibility of use of RTPF as a removal material. Effectiveness of the application of RTPF as a BTEX removal material was evaluated on a basis of concentrations values above the surface of reacting mixture (at 25 ± 3 °C). It was found that RTPF addition increased BTEX immobilization efficacy, compared to the use of Portland cement alone. The maximum percentage reduction in BTEX compounds concentration was 33% for toluene. Lower level of removal was observed for ethylbenzene (21%), and substantially, small efficacy was noted for xylenes (8%) and benzene (7%). Additionally, in order to evaluate mechanical properties of soil–cement composites, analysis of their compressive strength after 28 days of maturation was performed. Tests showed a decrease in the compressive strength of soil–cement monoliths containing RTPF.

Prediction on damage evolution of recycled crumb rubber concrete using quantitative cloud imagine correlation

Abstract To account for the improvement of mechanical properties for recycled crumb rubber concrete (RCRC) under uniaxial compression and flexural toughness test in detail, three groups of RCRC specimen covering contents of rubber aggregate from 10 percent to 30 percent and one group of normal concrete (NC) specimen were prepared. Experimental results present distinguished influence of rubber particle content on uniaxial compressive strength and failure mode. Then, improvement in toughness properties was displayed inherently through change of the index named ratio of flexural strength to compressive one ( R f - c ). Simultaneously, a mesoscopic numerical model on random aggregate of RCRC was built up and validated by comparison of results from damage simulating to in-door testing. Furthermore, the mechanism of ductility enhancement for RCRC is unveiled visually and the prediction on damage evolution is revealed in quantitative way by a novel methodology of quantitative cloud imagine correlation (QCIC) based on 2D analysis. Subsequently, the similar law is established by a 3D Extended QCIC named volumetric damage accumulation method (VDAM). Therefore, it put forward a step further from state-of-the-art research about mechanical properties of RCRC, which may promote the utility of optimal design for this ecological material in civil engineering.

Study on Influence of Waste Tire Rubber Particles on Concrete Crack Resistance at Early Age

Two groups of variables, the amount of rubber particles and the size of rubber particles, were set up to evaluate the early crack resistance of rubber concrete after 24 hours of forming. Combined with the test results, the influence of the amount and particle size of rubber particles on the early crack resistance of concrete is analyzed. The experimental results show that the early crack resistance of concrete increases with the decrease of the size of rubber particles when the content of rubber particles is small, but decreases first and then increases when the content of rubber particles is large. When the size of rubber particles is large, the early crack resistance of concrete increases with the increase of the content of rubber particles, on the contrary, decreases first and then increases.

Compression properties and micro-mechanisms of rubber-sand particle mixtures considering grain breakage

The waste materials of scrap tires are becoming more prevalent in geotechnical engineering. While adding scrap tires particles into sand particles as a filling material can reduce the stockpiles of scrap tires and minimize the environmental pollution. Therefore, investigating the effect of scrap tires-sand particle mixtures on compression properties is in urgent demand. In this study, the effect of the rubber particle content and vertical stress on the actual density, void ratio, coefficient of compressibility, modulus of compression, rebound and grain breakage is investigated systematically by a serious of laboratory tests. The test results reveal that when rubber content RV exceeds 50% (or less than 50%), the three-stage change trend of void ratio is proposed: accelerating reduction, deceleration stage and slow reduction (or accelerating reduction, slow reduction and stable stage). A region where the actual density is lower than the control density is given under different vertical stress and RV. In accordance with the coefficient of compressibility, the rubber-sand mixtures used in this paper is categorized into three groups: (1) Low compressive materials (RV = 0–10%); (2) Medium compressive materials (RV = 20–30%); (3) High compressible materials (RV > 50%). The addition of rubber particles to sand particles generates a significant reduction in modulus of compression, and the modulus of compression at the same rage of vertical stress decays exponentially with increasing RV. In addition, the plastic strain of specimens is greater than the elastic strain, and the gap between elastic strain and plastic strain is increasing with the increase of RV. A good linear relationship is derived between grain breakage Br and RV. Obviously, the particle breakage decreases with the increase of RV at different vertical stress levels. Based on the analysis of SEM, three force transmission ways with different RV are proposed to describe the compression micro-mechanic of rubber-sand particle mixtures.

Durability performance of rubberized mortar and concrete with NaOH-Solution treated rubber particles

This study experimentally investigated the durability of rubberized mortar and concrete samples with NaOH-solution treated rubber particles. The concrete samples without rubber particles were cast as control samples. The rubberized mortar or concrete samples were prepared with 15% as-received rubber and different contents of NaOH treated rubber (15%, 25%, 35% and 50% by volume of fine aggregate). The electrical resistivity, air-void measurement, and absorption tests were first conducted to evaluate the transport properties of rubberized concrete samples. The freeze-thaw durability tests on different concrete samples showed that the added rubber particles improved the freeze-thaw resistance of concrete. The effect was more significant for NaOH treated rubber particles than that of as-received rubber particles. The results of the alkali-silicate reaction (ASR) expansion test suggested that the ASR expansion was decreased in rubberized mortar compared to plain mortar. The 15% NaOH treated rubber replacement was most effective on reducing the ASR expansion among all of the rubberized mortar samples. The drying shrinkage increased with the content of rubber particles in mortar; however, the increased shrinkage in rubberized mortar appeared to be reduced when the additional rubber was treated with NaOH solution. These test results indicated that the rubberized concrete or mortar (with 15% or 25% NaOH-treated rubber replacement) samples have improved durability.

Investigation on the mechanical behavior of polyester-scrap tire composites

An investigation of the mechanical properties of unsaturated polyester composites containing rubber waste particles is presented. The main objective of this work was to formulate and develop polyester-rubber composite as an insulating material with acceptable mechanical performance. To determine the effect of the rubber particles ratio on the compressive and tensile strengths and moduli of a polyester composite 8 different concentrations (i.e., 5%, 10%, 15%, 20%, 25%, 30%, 35% and 40% by volume) were considered. The experimental results revealed that mixing rubber particles with the polyester matrix decreased both the compressive and tensile strengths and moduli of the composite. As the rubber content increases, and due to its low hydrophilicity towards polyester resin, the degree of crosslinking between the rubber particles and polyester is reduced causing a noticeable reduction in the composite strengths. On the other side for all investigated rubber contents, the larger the particle size of rubber, the lower the composites strength and modulus of elasticity. This is due to the difficulty of dispersion of the large particles into the matrix resulting non homogenous distribution of the particles and less interfacial contact with the matrix and in turn degradation in the mechanical behavior. However, smaller rubber particles have more specific surface area that could improve the interfacial contact with the polyester matrix. The SEM micrographs indicated that voids within the composite matrix increased with the content and size of rubber particles. Though adding rubber particles reduces the mechanical properties, the prepared composites demonstrate superior mechanical tensile strengths (22.8–1.25MPa) and compressive strength (79.5–8.42MPa) if compared with the currently used insulating materials and comparable to some construction materials like the stone masonry.

Experimental study on short rubberized concrete-filled steel tubes under cyclic loading

This paper presents an experimental investigation on the cyclic behaviour of short steel tubes filled with rubberized concrete (RuC), a composite material that mixes concrete with rubber particles. A brief literature review on the cyclic behaviour of CFST columns, the mechanical properties of RuC and recent research on RuC-filled steel tubes (RuCFSTs) is presented. Then, the tested specimens are characterized, comprising three cross-section shapes (square, rectangular, circular), three steel grades (S235, S275, S355), three concrete mixes (0%, 5%, 15% of rubber particles content) and two axial load levels (10%, 20% of axial plastic load). After that, the loading protocol, test rig and experimental procedure are described in detail. The experimental results are extensively discussed, focusing on the columns’ cyclic strength, failure modes, hysteretic and envelope curves, as well as on the energy-based ductility factors. Finally, conclusions are drawn regarding all these parameters. The most relevant achievement is that a concrete mix with a low content (5%) of rubber particles leads simultaneously to the lowest decrease (5%) in the cyclic strength and the highest increase (52%) in the ductility of RuCFST columns, thus being the most suitable mix to use in seismic areas, where ductility and energy dissipation requirements are mandatory.