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Tire consumption increased exponentially due to the rapid population growth and transportation development. For reusing waste tires in concrete, all available studies turned rubber into particles, replacing concrete cement or natural aggregates. This approach, however, prevents the optimum utilization of rubber properties and decreases the mechanical performance of rubberized concrete in most investigations. This paper presents the results of an experimental research, analyzing a novel approach of reusing waste car tires as a layer (surface and base course) to reduce concrete consumption. Under the short recycling process, the tread area of waste tires was cut and pasted to the concrete surface with tile and concrete adhesives. The sample performance was investigated through impact resistance, abrasion resistance, pull-off strength, and flexural strength tests. A comparison with the reference concrete sample was also performed. The results showed that using rubber as a surface and base course significantly increased the impact resistance of concrete. Samples containing rubber as a surface course had two times more abrasion resistance than plain concrete. Also, using rubber as a base course improved the flexural strength of concrete considerably. However, as a surface course, a marginal increase in the flexural strength of samples was achieved. The pull-off strength of specimens containing rubber as a layer decreased considerably due to the poor bond performance between the rubber and adhesive layer. Some suggestions for future studies are also provided. [ABSTRACT FROM AUTHOR]

Using waste rubber to partially replace fine aggregate to make rubber concrete can not only reduce black pollution to alleviate the dilemma of natural sand resource depletion, but also improve the frost resistance of concrete, which is undoubtedly a win–win solution. Aim to promote the application of rubber concrete seasonal cold regions, it is of great significance to evaluate and predict its frost-resistance. Different from ordinary concrete, the existence of rubber changes the inherent characteristics of concrete to varying degrees, which makes the durability of rubber concrete more complicated and the establishment of prediction models more challenging. In this paper, an artificial neural network (ANN) model was proposed to predict the frost-resistance of rubberized concrete. Using water-cement ratio, cement, sand, sand rate, rubber content and the number of freeze–thaw cycles as input variables and relative dynamic elastic modulus as output variables, a three-layer BP neural network (BPNN) prediction model with a hidden layer was established on the basis of a large number of experimental data of another author. The prediction results show that the proposed BPNN model has a strong ability to predict the frost resistance of rubberized concrete with satisfactory accuracy (R2 = 0.9825, MAPE = 1.5609%), which opens up a new way to improve the prediction accuracy of frost-resistance for rubberized concrete.Article Highlight: A BPNN prediction model was established for frost-resistance of rubberized concrete. Using concrete composition and relative dynamic elastic modulus as input and output variables of BPNN. Comprehensive consideration the empirical formula and the minimum mean square error to determine the number of neurons in hidden layer. [ABSTRACT FROM AUTHOR]

Recently developed multi-scale fiber (i.e., CaCO3 whisker, polyvinyl alcohol (PVA) fiber, and steel fiber) reinforced rubberized concrete exhibits excellent mechanical properties and spalling resistance at high temperatures. Measurement of macro properties such as strength and Young's modulus cannot reveal and characterize damage mechanisms, particularly those relating to the multi-scale fiber strengthening effect. In this study, acoustic emission (AE) technology is applied to investigate the impact of multi-scale fiber on the damage evolution of rubberized concrete exposed to high temperatures, under the uniaxial compression and tension loading processes. The mechanical properties, AE event location, peak frequency, b-value, the ratio of rise time to amplitude (RA), average frequency (AF) values, and AE energy of specimens are investigated. The results show that the number of events observed using AE gradually increases as the loading progresses. The crumb rubber and fibers inhibit the generation and development of the cracks. It is concluded that both the peak frequency and b-value reflect the extension process of cracks. As the cracks develop from the micro scale to the macro scale, the peak frequency tends to be distributed in a lower frequency range, and the b-value decreases gradually. At the peak stress point, the AE energy increases rapidly and the b-value decreases. The specimens without multi-scale fibers exhibit brittle failure, while the specimens with fibers exhibit ductile failure. In addition, adding multi-scale fibers and crumb rubber increases the peak frequency in the medium and high frequency ranges, indicating a positive effect on inhibiting crack development. After being subjected to high temperatures, the maximum and minimum b-values decrease, reflecting an increase in the number of initial cracks due to thermal damage. Meanwhile, the RA and AF values are used to classify tensile and shear cracks. The specimens fracture with more shear cracks under compression, and there are more tensile cracks in specimens with multi-scale fibers under tension. [ABSTRACT FROM AUTHOR]

This paper presents an experimental study on how crumb rubber particles from waste tires and corrugated round steel fibers affect the mechanical behavior of concrete. In addition to the standard plain mix and five combinations of mixes composed of 0.5%, 1.0%, and 1.5% ratios, three steel fiber and crumb rubber mixes, 0.5%, 1.0%, and 2.0% weight of sand, coarse aggregate, cement, and silica fume were evaluated. The percentage of silica fume that replaced the weight of the cement in this study was 8%. The fresh properties of the 12 mixtures in terms of slump and density were studied. After 28 days of curing 36 cubes, 36 cylinders, and 12 prisms, the hardened properties were determined by evaluating the mean compressive, split, and flexural strengths. The results indicate that a synergetic effect is observed for the combination of crumb rubber and corrugated round steel fibers to improve the fresh and hardened properties of concrete. Adding fiber reinforcement to concrete can mitigate the negative impacts of rubber, and vice versa. According to the combination content, increases in compressive strength, tensile strength, and flexural strength of up to 49.04%, 38.60%, and 75.76%, respectively, were achieved compared with the control combination. This validates the applicability of the proposed mathematical prediction formulation to evaluate the compressive strength, split tensile strength, and modulus of rupture of rubberized fibrous concrete in terms of fiber and rubber ratios. Based on these results, a promising solution for tire disposal is to recycle waste rubber for fibrous concrete applications. [ABSTRACT FROM AUTHOR]

The use of concrete-filled steel tube (CFST) piers has attracted widespread attention due to their high load-bearing capacity, excellent ductility, and superior seismic performance. Given their role as bridge substructures responsible for transmitting seismic loads, the ability of CFST piers to dissipate energy under seismic conditions significantly impacts bridge safety. This study investigates rubberized concrete-filled corrugated steel tube (RuCFCST) pier as a solution for addressing issues such as local buckling, bulging, or tearing damage in CFST columns during seismic loading. Four 1:4 scale pier specimens were subjected to pseudostatic tests to determine the effects of the axial compression ratio, filling concrete type, and connection method on the damage development, failure mode, strain distribution, and seismic performance of the pier specimens. In addition, a reliable nonlinear finite element model was established to evaluate sensitive parameters such as the length–diameter ratio, axial compression ratio, diameter-to-thickness ratio, and confinement factor. The influence of each parameter on this type of composite pier was revealed. The results showed that the flexural strength of corrugated steel tubes filled with rubber concrete was 17.4% lower than that of ordinary concrete tubes, but the ductility coefficient was 24.3% higher. When the axial compression ratio is increased from 0.2 to 0.3, the flexural strength of the composite pier increases by 16.8%, while the ductility coefficient decreases by 8%. Additionally, utilizing embedded connections reduces the flexural strength by 16.4%, but it increases the ductility coefficient by 45.9%. Finite element analysis revealed that the confinement factor was the metric with the highest sensitivity in relation to the flexural strength of the pier. This research is a novel and comprehensive exploration of the seismic performance of RuCFCST piers that provides experimental and numerical support for transitioning from conventional CFSTs to this innovative structural solution. [ABSTRACT FROM AUTHOR]

The main aim of this research is to investigate and mathematically express the relationship between the mixture proportions of rubberized concrete and its thermal conductivity performance. For that purpose, a dataset with a wide range of experimental variables was compiled from the studies available in the literature and one of the most important and widely used machine learning methods, called Artificial Neural Networks, was chosen to establish this mathematical expression strongly and consistently. Two important criteria were taken into consideration when compiling the dataset: firstly, the aggregate had to be of natural normal weight and secondly, the rubber aggregate had to be derived from waste tire and not treated. A reliable, functional, and robust empirical model to estimate the thermal conductivity coefficient of the rubberized concrete was generated in the scope of this study based on the input parameters like cement content (c), water-to-cement ratio (w/c), natural aggregate-to-cement ratio (na/c), rubber aggregate-to-cement ratio (ra/c), and rubber type (rt). The estimation capability of the model was validated using a dataset that the model never faced and was evaluated based on some statistical metrics like R2, MAPE, MSE, etc. The R2, MAPE, and MSE values of the trained model were about 0.984, 4.62%, and 0.002, respectively. Both validation and statistical evaluation results revealed that the model can accurately and reliably estimate the thermal conductivity coefficient of the rubberized concrete. Besides, the statistical metrics of the developed model were in the acceptable range for such models. [ABSTRACT FROM AUTHOR]

Recycling scrap tires provides an alternative source of fine aggregates for the production of rubberized concrete and this will lead to significant increase in concrete frost resistance, environmental protection, and conservation of natural sand and gravel resources. In this paper, a total of 25 groups of rubberized concrete were produced by adding scrap tire rubber particles of different sizes, contents, and pretreatment methods to replace the fine aggregate, and their compressive strength during freeze–thaw cycles was studied from both the macro- and meso-perspectives. The results indicated that the decrease in concrete strength and weight was notably restricted by the presence of rubber particles during freeze–thaw cycles. The rubber fine aggregate with smaller particle sizes enhanced the concrete frost resistance more significantly, and the F100 of concrete with rubber particles of 1.0–2.0 mm increased from 76.6 to 86.5% by increasing the rubber content from 0.0 to 5.6%. The effects of rubber fine aggregate on concrete compressive strength during freeze–thaw cycles were quantified. On this basis, a forecast model for rubberized concrete compressive strength in freeze–thaw cycles was proposed, and the effects of the particle size, content, and pretreatment of the rubber particles were considered. The calculated results agreed well with the test results both in this study and the relevant peer studies, indicating that the model can provide a good reference for the design and engineering application of rubberized concrete in frigid environments. [ABSTRACT FROM AUTHOR]

Nowadays, intensive investigations on the potential of rubberized concrete as a structural material are available in the literature due to its promising characteristic in terms of sustainability, ductility, high absorption of energy, and enhanced vibration behavior. These works have initiated the introduction of multiple estimation methods to rapidly evaluate its properties. Over the last few decades, hundreds of researches have been conducted to assess different mathematical approaches for modeling concrete's properties. Among them, multivariable regression analysis is considered one of the simplest multipurpose options. However, its adaptation is sometimes inefficient, and its results are not highly accurate. This study proposes an enhancement to the estimation technique for rubberized concrete's mechanical characteristics by conducting a data reconstruction using kernel principal component analysis and then utilizing multivariable regression to develop the prediction models. The importance of the kernel principal component analysis comes from its capability to transform the input parameters to visualize the dataset's information described by multiple inter-correlated quantitative variables so that it discovers underlying patterns. In general, the research results have shown that the performance of the proposed method can significantly overcome that of the conventional regression techniques with as high as 80% reduction in the root-mean-square error in the case of compressive strength. [ABSTRACT FROM AUTHOR]

With the increasing operation mileage of urban rail transit, to ensure its operation safety, it is necessary to carry out health monitoring on the rail, tunnel, and other structures. How to capture the vibration energy generated by train operation and use it to monitor the power supply of sensors has become a research hotspot in recent years. In this paper, a new type of spherical energy harvester is designed for rubberized concrete tunnel invert-filling. Based on the calculation model of rubberized concrete tunnel invert-filling under train load, the vertical displacement, stress, voltage, and total electric energy are analyzed. The main conclusions are as follows: (1) The spherical energy harvester is embedded in the rubberized concrete tunnel invert-filling in the form of an array, and the optimal position is 5 mm below the sleeper. (2) Ten energy harvesters are set up in the scope of a 6-m-long rubberized concrete tunnel invert-filling. The electric energy of the millijoule level can be generated when an A-type train of 8-vehicle formation passes by. If the departure interval of 5 min/trip is calculated, the total electric energy harvesting in 1 h is 122.4 mJ. (3) Rubberized concrete tunnel invert-filling is more conducive to energy harvesting than ordinary concrete tunnel invert-filling. When the content of rubber is 10%, the total electric energy harvesting by the energy harvester array inside the tunnel invert-filling is 5% higher than that of the ordinary concrete, and the mechanical performance indexes such as stress are within the safe range. The research results of this paper have reference value for further exploration of electric energy harvesting in the running environment of rail transit trains. [ABSTRACT FROM AUTHOR]

During the past two decades, geopolymer concrete has been investigated as a sustainable alternative to Portland cement concrete, which is known to generate a huge amount of CO2 in the environment. This study focuses on the assessment of the fresh and hardened mechanical properties and durability of metakaolin (MK)-based geopolymer rubberized concrete. Crumb rubber was derived from discarded waste tires, another pollution source to the environment, and incorporated in concrete as fine aggregate replacement in ratios from 10 to 50% by volume. The performance of the MK-based geopolymer rubberized concrete is discussed based on its workability, air content, stress–strain behavior (including compressive strength and modulus of elasticity), flexural strength, dry unit weight and rapid chloride penetrability. The results show that the proposed sustainable concrete mixes achieve acceptable fresh and hardened mechanical and durability properties. The compressive strength when crumb rubber replaces fine aggregates in volumetric percentages between 10 and 40% are in the range of 28.7–39.7 MPa. Furthermore, the unit weight and modulus of elasticity of the MK-based geopolymer rubberized concrete mix with 40% rubber replacement are 14.9 GPa and 2134 kg/m3, respectively. This can promote a potentially large market for the MK-based geopolymer rubberized concrete products in applications where the priority is for decreasing self-weight and increasing flexibility rather than strength. [ABSTRACT FROM AUTHOR]

Scholars have studied the impact of rubber particles (RPs) on the performance of the concrete and the research topics have covered all the mechanical properties and durability of normal concrete (NC). Recently, scholars have turned their research interest to the structural properties of concrete. However, there are few experimental studies on the bonding properties of RC to NC. The RPs have both positive and negative impacts on the bond performance. On one hand, RPs can reduce the shrinkage of concrete, resulting in reduced shear stress and tensile stress near the bonding boundary. On the other hand, RPs cause a reduction in the overall strength of concrete, resulting in the poor mechanical performance of the interface transition layer between the two concrete. The test results of this study show that the bonding splitting tensile strength between freshly mixed RC to aged NC first increases and then decreases with the rise of the RPs content in the RC, and the bonding splitting tensile strength reaches the peak when the RPs content is 10%. The bonding splitting tensile strength between the NC and the RC mixed with 3–5 mm RP is higher than that between the NC and the RC mixed with 1–3 mm RPs. When mixed with modified RPs, the bonding splitting tensile strength between the RC and the NC is improved. Applying an interfacial agent (a cement slurry or an epoxy) on the old concrete bonding surface can significantly improve the bonding splitting tensile strength. The results of non-repeated two-way ANOVA show that the content of the RPs and the type of the interfacial agent have significant effects on the bond splitting tensile strength, while the size and modification of the RPs have no significant effects on the bond splitting tensile strength. [ABSTRACT FROM AUTHOR]

Rubberized concrete is highly effective in areas where more flexibility is required. Compared to standard concrete, rubberized concrete has greater flexibility, impact resistance, and lower unit weight. In this study, sulfuric acid is used in the surface treatment process of rubber particles to strengthen the bonding property of rubber particles and cement paste. Six waste tire rubber crumb contents (0, 10, 15, 20, 25, and 30%) and particle sizes of 0.6–2.36 mm were used as partial replacement of fine aggregate in concrete. Microstructural analyses (EDX, TGA, XRD) are conducted on rubber crumbs to examine rubber's compatibility before using it in concrete. The fresh, hardened, microstructural properties (SEM and XRD) and stress vs. strain behavior of rubberized concrete are investigated. From the SEM image, it is analyzed that surface treatment improves the bonding properties of rubber particles and cement paste compared to untreated rubber particles. The mechanical properties of rubberized concrete reduce by increasing the rubber crumb in the mix. Still, the results are not much troubling up to 15% replacement level of rubber crumb, and the rubberized concrete has a highly deformable capacity than standard concrete. [ABSTRACT FROM AUTHOR]

Incorporating crumbed recycled rubber powders as aggregate has great potential for improving the impact resistance of concrete and easing the environmental issue caused by the disposal of waste tires. This study was conducted to evaluate the effect of rubber powders on the properties of ultra-high performance concrete (UHPC). River sand was replaced by the same volume of rubber powders at different ratios of 5, 10, and 15% in UHPC. The flowability, quasi-static mechanical properties, and dynamic compressive properties of UHPC containing crumbed rubber powders were thoroughly investigated. The experimental results showed that rubber powders reduced the flow of UHPC. The poor bonding between rubber powder and cement paste compromised the quasi-static mechanical properties of UHPC. However, with the increasing content of rubber powders, the extent of damage and the brittle behavior of UHPC under impact loading were restrained significantly. Rubber powders enhanced the dynamic compressive properties of UHPC by increasing the tortuosity of cracks and dissipating energy. The dynamic strength quantified by the dynamic increase factor was more sensitive in UHPC with rubber powders than that in control mix. In addition, new linear fitting curves to predict the dynamic increase factor of UHPC with different contents of rubber powders were proposed. [ABSTRACT FROM AUTHOR]

Rubberized concrete is an environmentally friendly building material that mixes rubber particles from old automobile tires into normal concrete in place of fine aggregate. The addition of rubber particles can improve the abrasion resistance of normal concrete observably. It has a good application prospect in hydraulic engineering, especially in the concrete building parts with high abrasion resistance. However, there are few experimental studies on the abrasion resistance of rubberized concrete, and the influence law and mechanism of rubber particles on the abrasion resistance of concrete are not understood. In this paper, the abrasion resistance of rubberized concrete is studied using the underwater-steel-ball method. The results show that rubber particles increase the slump of concrete mixtures. The abrasion resistance of rubberized concrete increases significantly with increasing rubber particle content, whereas the compressive strength decreases linearly. For the same rubber particle size and content, the abrasion resistance of rubberized concrete positively correlates with compressive strength and larger rubber particles significantly improve the abrasion resistance. Rubber particle content is the factor that most strongly affects abrasion resistance of rubberized concrete, followed by the compressive strength. Rubber particle pretreatment methods of NaOH + KH570 can significantly improve the abrasion resistance of rubberized concrete. [ABSTRACT FROM AUTHOR]

Over the last few years, many studies were performed to investigate rubberized concrete's behavior as a sustainable alternative for conventional concrete by replacing natural aggregates with recycling old rubber tires. These studies have shown that the concrete's mechanical and durability properties are significantly reduced, while its ductility and damping ratio improved. Accordingly, using this material in RC structures could be a promising solution for improving their energy dissipation capabilities. Currently, the literature lacks a numerical study that can highlight the effectiveness of using high-strength rubberized concrete for retrofitting RC structures subject to earthquake loadings. Therefore, this research investigates the seismic performance of reinforced concrete buildings strengthened using different high-strength rubberized concrete mixtures under various ground motion excitations. As a part of the study, finite element models of reinforced concrete structure retrofitted with these concrete mixes will be analyzed using nonlinear response history analysis and compared against two different control models composed of a bare structure and a jacketed RC structure using the control concrete mixture. In general, using rubberized concrete jacketing improved the seismic performance of the bare structure significantly. Furthermore, utilizing high-strength rubberized concrete rather than the control one resulted in increasing the damping energy and slightly reducing the base shear forces of the structure. [ABSTRACT FROM AUTHOR]

The use of rubber in concrete has been practiced in the engineering community for several years. However, the poor mechanical properties of rubberized concrete are a serious hurdle. This innovative research provides a closer look at improving the flexural strength of rubberized concrete beams with high rubber content using confinement technique. FRP jackets with different confinement thickness were used to recover the strength loss of rubberized concrete beams. In this paper, 66 rubberized concrete (RuC) beams having 0–50% rubber content were tested under four-point loading. RuC beams suffered up to 167% reduction in flexural strength. However, the FRP jackets were highly effective to improve the flexural strength of RuC beams. The statistical models were developed to predict the flexural strength of FRP confined rubberized concrete beams using response surface methodology (RSM). In this regard, the effect of two principle variables; unconfined strength and number of FRP layers on the flexural strength of FRP confined rubberized concrete beams was investigated. The models were found significant because the predicted and adjusted R2 was less than 0.2 (a limit proposed by Design Expert software). The predicted and experimental results for FRP confined rubberized concrete beams were found in good agreement. The developed statistical models provide insights into the sensitivity of parameters affecting the flexural strength. The proposed models can improve the reliability of the experiments and reduces the design and analysis time. [ABSTRACT FROM AUTHOR]

This paper presents a comparative study on the composite structure of Corrugated Steel Plate (CSP) with normal and rubberized concrete. One CSP-normal-concrete plate and two CSP arch structures composited with different concretes are established. A theoretical section-property deduction is derived, which demonstrated that the flexural rigidity of such composite structure increased notably. Static and dynamic mechanical experiments are also conducted. Experimental results agree with expectations, and the measured results on plate structures verified the effectiveness of the analytical and numerical solutions. Comparing the deflection of two composite arches shows that the rubberized concrete composite arch has smaller flexural and compressive stiffnesses, resulting in larger deflection. The rubberized concrete composite arch has higher steel stress, lower concrete stress and better energy-dissipating capacity compared with the normal concrete composite arch. Therefore, the CSP-rubberized concrete composite structure is more suitable for anti-shock and earthquake-resistant structures. [ABSTRACT FROM AUTHOR]

The main objective of the research presented in this paper is to study the bending behaviour of Concrete Filled Steel Tube (CFST) columns made with Rubberized Concrete (RuC), and to assess the seismic performance of moment-resisting frames with these structural members. The paper describes an experimental campaign where a total of 36 specimens were tested, resorting to a novel testing setup, aimed at reducing both the preparation time and cost of the test specimens. Different geometrical and material parameters were considered, namely cross-section type, cross-section slenderness, aggregate replacement ratio, axial load level and lateral loading type. The members were tested under both monotonic and cyclic lateral loading, with different levels of applied axial loading. The test results show that the bending behaviour of CFST elements is highly dependent on the steel tube properties and that the type of infill does not have a significant influence on the flexural behaviour of the member. It is also found that Eurocode 4 is conservative in predicting the flexural capacity of the tested specimens. Additionally, it was found that the seismic design of composite momentresisting frames with CFST columns, according to Eurocode 8, not only leads to lighter design solutions but also to enhanced seismic performance in comparison to steel frames. [ABSTRACT FROM AUTHOR]

This paper investigates the possibility of using rubber waste from scrap tires as replacement of coarse aggregate in concrete. Performance of concrete mixtures incorporating 5, 10 and 15% of scrap rubber as volume replacement for coarse aggregate was investigated. Compressive strength, flexural strength, stress-strain behavior, workability, air content, water absorption and unit weight were evaluated using standard procedures. Thermal behavior for concrete was examined using hotbox technique. No remarkable changes in concrete properties up to 5% substitution were occurred. Beyond 5% substitution, concrete properties change appreciably. Compressive strength, flexure strength, workability, stiffness and unit weight of rubberized concrete decreased as rubber content increased. While impact resistance, air content and water absorption of rubberized concrete increased with increase in rubber content. Thermal performance of concrete containing rubber aggregate was improved, and promising results were obtained. Thus, rubberized concrete could be useful in slabs to improve energy efficiency of building unit. [ABSTRACT FROM AUTHOR]

To improve the combination of cement matrix and waste tire rubber particles in concrete, the rubber particles were treated with acrylic acid (ACA) and polyethylene glycol (PEG) for grafting hydrophilic groups on their surfaces. The X-Ray photoelectron spectroscopy (XPS) and surface contact angle were used to characterize the hydrophilicity and surface functional group of rubber particles. The effect of rubber particle modification on fresh/hardened properties of rubberized concrete was studied. The experimental results show that the contact angle between rubber particle surface and water decreases when rubber particle is modified. Compared with the unmodified rubberized concrete(RC), the unit weight of modified rubberized concrete(MRC) changes slightly. However, the slump, air-entrainment, compressive strength, flexural strength, and impact performance of MRC are obviously improved. Under good condition of slump, the water-cement ratio of the MRC can be reduced from 0.4 to 0.38. And the compressive strength and flexural strength of the MRC(10% rubber particle content) can be increased by 25.9% and 26.4%, respectively. [ABSTRACT FROM AUTHOR]

In this study, the impact resistance of double-layer concrete panels made of rubberized and steel fiber reinforced concrete subjected to direct fire weapon (11 mm or 0.45 magnum bullet size) is investigated. Concrete panels with dimensions of 400 × 400 × 50 mm are subjected to impact forces from 11 mm-diameter bullets at a distance of 10 m. Three types of concrete panels are tested: single-layer steel fiber reinforced concrete (SFRC), single-layer crumb rubber concrete (CRC), and double-layer CRC/SFRC. For a double-layer CRC/SFRC, the CRC layer of 12.5 mm is added to the front surface by partially replacing part of the SFRC panel. The CRC layer is expected to act as a cushion layer to absorb impact energy from the bullet and to reduce damage to the concrete panel. [ABSTRACT FROM AUTHOR]

The abrasion resistance properties of rubberized concrete were comparatively studied by taking silica fume and crumb tire rubber as the additives. The abrasion tests were conducted in accordance with the Chinese standard test method DL/T 5150 - 2001, two recommended test methods: under water method and ring method, were used. The crumb tire rubbers with the sieve size of 8-mesh and 16-mesh were incorporated into the concrete by replacing same volume of sand and as an additive. The abrasion resistance of concrete was evaluated according to the abrasion resistance strength and the mass loss. Test results show that the addition of silica fume enhanced both compressive strength and abrasion resistance of concrete, and the addition of crumb rubber reduced the compressive strength but increased notably the abrasion resistance of the concrete. Silica fume concrete performed a better abrasion resistance than control concrete, and the rubberized concrete performed a much better abrasion resistance than silica fume concrete. The abrasion resistance of rubberized concrete increased with the increase of rubber content. [ABSTRACT FROM AUTHOR]

In this study, FRP tube encased waste tire rubber modified concrete cylinders were investigated. Four batches of confined and unconfined concrete cylinders with a diameter of 101.6 mm and a height of 304.8 mm were prepared. Each batch contained three confined cylinders and three unconfined cylinders. The total number of effective cylinders prepared was 24. Batches 1-3 were made of rubberized concrete. In Batch 1, 15% by volume of coarse aggregate was replaced by waste tire fibers or stripes; in Batches 2 and 3, 15% by volume of sand and 30% by volume of sand were replaced by crumb rubbers, respectively. Batch 4 was a control batch with conventional plain concrete. Uniaxial compression tests were conducted on all the cylinders per ASTM C39. Strain gages were installed on the encased rubberized concrete cylinders to obtain local strain distributions. The compressive strength and strain at the peak load were compared with the predictions by available design-oriented confinement models. It is found that the FRP tube encased rubberized concrete cylinders have higher confinement effectiveness, ductility, and elastic regions than FRP tube encased conventional concrete cylinders. Waste tire fiber modified concrete performs better than crumb rubber modified concrete with a lower cost. Instead of volume contraction, FRP encased rubberized concrete cylinders experience volumetric expansion. The current design-oriented confinement models cannot consistently predict the compressive strength and strain of the encased cylinders. An 1-D coupon test cannot uniquely determine the hoop tensile strength of the FRP tubes which are subjected to a 2-D stress condition. [ABSTRACT FROM AUTHOR]

Acoustic emission (AE) technique is employed to investigate the damage process of the notched plain concrete and rubberized concrete specimens under 3-point bending load. AE signals in the fracture process of notched specimens are illustrated by analyzing the distribution of amplitude and hit rate of AE signals. AE signals in the rubberized concrete have lower activity and amplitude than in the plain concrete. By AE location analysis, it is found that the high energy events mainly are distributed near the notch tip. According to AE energy, the fracture process zone (FPZ) is determined. By comparing the FPZ of both concretes, it is found that the incorporation of rubber particles in concrete can greatly alleviate the damage process of concrete specimens and the damage zone in the rubberized concrete is much smaller than in the plain concrete. The moment tensor is also used to analyze the type of cracks and it is found that tensile cracks dominate the early period of loading, while shear cracks become dominant with propagation of cracks in late load period. [ABSTRACT FROM AUTHOR]

Using the discarded tire rubber as the concrete aggregate may be a solution to disposal of this waste material. However, presence of the rubber aggregates in the concrete mixture decrease the mechanical properties of such concretes depending mainly on the type and the content of the rubber used. In this paper, neural network (NN) and genetic programming (GEP) based explicit models are proposed for the prediction of mechanical properties of rubberized concretes. Data used in both training and testing of NN and GEP models were obtained from an experimental study containing a total of 70 rubberized concretes. The models were constructed using eight design variables and one response as the inputs and output, respectively. Compressive strength, splitting tensile strength, and static elastic modulus of the concretes were employed as the outputs of the models developed in this study. It is found that both NN and GEP provided high prediction capability with certain accuracy. The proposed formulations also showed perfect agreement with the experimental study, thus leading to beneficial and practical estimation of the mechanical properties of the rubberized concretes. [ABSTRACT FROM AUTHOR]

By ring test and bend test, the improvement of waste tire rubber particles on the crackresistance and flexural behaviors of cement-based materials were investigated. Test results show that the cracking time of the ring specimens can be retarded by the incorporation of rubber particles in the cement paste and mortar. The improvement in the crack-resistance depended on the rubber fraction. When the rubber fraction was 20% in volume, the cracking time was retarded about 15 h for the paste and 24 d for the mortar respectively. Flexural properties were evaluated based on the bend test results for both mortar and concrete containing different amount of rubber particles. Test results show that rubberized mortar and concrete specimens exhibit ductile failure and significant deformation before fracture. The ultimate deformations of both mortar and concrete specimen increase more than 2–4 times than control specimens. [ABSTRACT FROM AUTHOR]

The study presented herein has been carried out in order to investigate the strength development and chloride permeability characteristics of plain and rubberized concretes with and without silica fume. For this purpose, two types of tire rubber, namely crumb rubber and tire chips, were used as fine and coarse aggregate, respectively, in the production of rubberized concrete mixtures which were obtained by partially replacing the aggregate with rubber. Two water-cementitious material (w/cm) ratios (0.60 and 0.40), three moist curing periods (3, 7, and 28 days), four designated rubber contents (0, 5, 15, and 25 by total aggregate volume), two silica fume content (0 and 10% by weight of cement), and five different testing ages (3, 7, 28, 56, and 90 days) were considered as experimental parameters. The results indicated that for a given w/cm ratio and moist curing period, the use of rubber significantly aggravated the chloride ion penetration through concrete but the degree of the rate of the increment of the chloride permeability depended on the amount of the rubber used. When the curing period was extended from 3 to 28 days, the reduction in the magnitude of chloride penetration depth was notably higher for the rubberized concretes, even at a rubber content of as high as 25%. It was also observed that silica fume may be considered as a remedy to enhance the chloride penetration resistance of the rubberized concretes. [ABSTRACT FROM AUTHOR]

In order to raise the efficiency of resource utilization, recycling waste rubber particles into concrete as aggregate has been widely accepted. When the size and content of the rubber particles are appropriate, rubberized concrete can achieve many excellent properties. This study investigated the impact of rubber replacement on dynamic compressive and splitting tensile properties of concrete. The split Hopkinson pressure bar tests of rubberized concrete containing 5%, 10%, 15% and 20% volume replacement for sand were completed. The failure modes, stress curves and dynamic strength values of rubberized concrete under high strain rates were recorded. The results reveal that the dynamic compressive and splitting tensile strength of rubberized concrete decrease with increasing rubber content. Meanwhile, peak strain increases with increasing rubber content. Dynamic increase factors (DIFs) of compressive and splitting tensile strength also were calculated, where rubberized concrete shows a stronger strain rate sensitivity. The analysis of specific energy absorption illustrates that rubberized concrete with 15% rubber replacement has the best impact toughness. In addition, ratios of dynamic compressive-tensile strength of rubberized concrete were calculated, which are between 3.82 and 5.39. [ABSTRACT FROM AUTHOR]