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This study presents a systematic investigation of the bond behaviour of rubberized concrete. The local and global bond behaviours of rubberized concrete are studied experimentally using concentric pull-out test and beam end test, respectively. The test parameters include concrete strength grade, bar embedded length, bar diameter and rubber content. In addition to the bond tests and the ancillary material property tests, six large-scale reinforced rubberized concrete beams are also tested under flexural bending to evaluate the influence of the alteration of bond behaviour owing to rubber incorporation on the flexural performance of the beams. The higher deformability of rubberized concrete compared to conventional concrete at each strength grade results in altered local and global bond behaviour, where the reduced peak bond stress and an increase in the slip at the peak bond stress are observed. The altered bond in conjunction with the other reduced mechanical properties of rubberized concrete subsequently led to a reduction in the flexural stiffness at the elastic stage and a reduction in ductility at the post-peak stage of a corresponding reinforced concrete beam containing rubber. The results of the mechanics-based and code-based models for predicting the development length for a reinforced bar in rubberized concrete indicated that the code-based model to design the anchorage length in rubberized concrete could be used with confidence Refereed/Peer-reviewed

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.

This study aims to assess the effect of high temperature on the bond strength of Concrete Filled Steel Tubular (CFST) sections incorporating crumb rubber particles as partial replacement of fine aggregates in concrete core. High daily temperatures; as in hot countries; was considered as well. Push out tests were conducted on 72 CFST specimens with five different concrete mixes. Prior to these tests, 210 concrete specimens were tested to obtain the mechanical properties of rubberized concrete under high temperature gradients. Some of the tests; on CFST sections or concrete specimens; were tested at the desired high temperature, and some others were tested after cooling down. The main variables considered were the crumb rubber replacement ratio, shape of CFST section (circular or square) and temperature gradient. The test results indicated that high temperature reduces the bond strength between steel tube and rubberized concrete core with small percentage of rubber replacement. Recovery in bond strength was observed when the specimens were cooled down. Circular sections showed higher bond strength and ductility on its square counterpart.

Over one billion tires are disposed into the environment each year and this has become a major environmental issue in the globe. Recycling of these waste tire rubbers in concrete has gained attention from researchers all around the world. In this study, the impact resistance of rubberized concrete exposed to fire is investigated experimentally in the laboratory. For that purpose, sixty specimens were made with five different mixes replacing their sand content partially with different percentages of tire rubber by weight ratios of 0% control, 6%, 12%, 18% and 24%. The water/cement ratio was kept constant at 0.393 in all the mixes. In each mix, fifteen concrete specimens with the size of (150 x 150 x 73) mm were prepared to expose to fire. Every three specimens were gradually exposed to fire for four various durations of (0, 15, 30, and 45) minutes. Each specimen was then tested in a drop-weight impact machine by dropping 2240-gr and 4500-gr hammers from heights of 280 mm and 450 mm. The average impact energy of three identical specimens required for the occurrence of the final fracture was calculated. The investigational results are compared with results of control samples. It is found that the impact energy considerably increased with an increase of the rubber replacement. It is, also, noted that any increase in the burning period of specimens results in a reduction of the impact energy and more early crushing of the rubberized concrete.

This study aimed to investigate abrasion resistance, flexural toughness and impact resistance of concrete mixes with incorporated particles of crumb rubber (CR) as a partial substituent by volume to concrete natural aggregates. Seven concrete mixes were prepared with water to cement ratio 0.4 and cement content 450 kg/m3 . One mix, with no rubber content, was considered as a reference mix to compare the designated mechanical properties of plain rubberized mixes, while the remaining six mixes contained crumb rubber as a partial replacer at levels of 10%, 20% and 30% by volume of each sand and crushed stone aggregates. Abrasion resistance was evaluated according to British standard BS 1338 and impact resistance was measured according to ACI 544.2R. It has been discovered that increasing CR replacement level led to a significant improvement in abrasion resistance, flexural toughness, and impact resistance (number of blows that cause failure cracking). Abrasion lengths decreased by 3.0 - 20.6%, while flexural toughness and impact resistance increased by 8.2 - 39.4% and 18.7 - 365.4% respectively with increasing crumb rubber replacement level.

This paper analyzes concrete fine aggregate (sand) modification by scrap tire rubber particles-fine crumb rubber (FCR) and coarse crumb rubber (CCR) of fraction 0/1 mm. Such rubberized concrete to get better bonding properties were modified by car-boxylated styrene butadiene rubber (SBR) latex and to gain the strength were modified by glass waste. The following tests—slump test, fresh concrete density, fresh concrete air content, compressive strength, flexural strength, fracture energy, freezing-thawing, porosity parameter, and scanning electron microscope—were conducted for rubberized concretes. From experiments, we can see that fresh concrete properties decreased when crumb rubber content has increased. Mostly it is related to crumb rubber (CR) lower specific gravity nature and higher fineness compared with changed fine aggregate-sand. In this research, we obtained a slight loss of compressive strength when CR was used in concrete However, these rubberized concretes with a small amount of rubber provided sufficient compressive strength results (greater than 50 MPa). Due to the pozzolanic reaction, we see that compressive strength results after 56 days in glass powder modified samples increased by 11–13% than 28 days com-pressive strengths, while at the same period control samples increased its compressive strength about 2.5%. Experiments have shown that the flexural strength of rubberized concrete with small amounts of CR increased by 3.4–15.8% compared to control mix, due the fact that rubber is an elastic material and it will absorb high energy and perform positive bending toughness. The test results indicated that CR can intercept the tensile stress in concrete and make the deformation more plastic. Fracturing of such conglomerate concrete is not brittle, there is no abrupt post-peak load drop and gradually continues after the maximum load is exceeded. Such concrete requires much higher fracture energy. It was obtained that FCR particles (lower than A300) will entrap more micropores content than coarse rubbers because due to their high specific area. Freezing-thawing results have confirmed that Kf values can be conveniently used to predict freeze-thaw resistance and durability of concrete. The test has shown that modification of concrete with 10 kg fine rubber waste will lead to similar mechanical and durability properties of concrete as was obtained in control concrete with 2 kg of prefabricated air bubbles.

Recycling of the waste rubber tire crumbs (WRTCs) for the concretes production generated renewed interest worldwide. The insertion of such waste as a substitute for the natural aggregates in the concretes is an emergent trend for sustainable development towards building materials. Meanwhile, the enhanced resistance of the concrete structures against aggressive environments is important for durability, cost-saving, and sustainability. In this view, this research evaluated the performance of several modified rubberized concretes by exposing them to aggressive environments i.e., acid, and sulphate attacks, elevated temperatures. These concrete (12 batches) were made by replacing the cement and natural aggregate with an appropriate amount of the granulated blast furnace slag (GBFS) and WRTCs, respectively. The proposed mix designs’ performance was evaluated by several measures, including the residual compressive strength (CS), weight loss, ultrasonic pulse velocity (UPV), microstructures, etc. Besides, by using the available experimental test database, an optimized artificial neural network (ANN) combined with the particle swarm optimization (PSO) was developed to estimate the residual CS of modified rubberized concrete after immersion one year in MgSO4 and H2SO4 solutions. The results indicated that modified rubberized concrete prepared by 5 to 20% WRTCs as a substitute to natural aggregate, provided lower CS and weight lose expose to sulphate and acid attacks compared to control specimen prepared by ordinary Portland cement (OPC). Although the CS were slightly declined at the elevated temperature, these proposed mix designs have a high potential for a wide variety of concrete industrial applications, especially in acid and sulphate risk.

This study investigated the potential use of tire derived rubber aggregates, particularly powdered rubber, and recycled steel-wire fibers in concrete subjected to impact loading. The fibers are approximately 0.4 mm in average diameter and 25 mm in length on average. There are two main portions to this study. The first phase of this study involved small-scale batching to investigate the fresh and hardened properties of concrete mixtures with powdered rubber up to 50% replacement of sand volume and recycled steel fibers up to 0.25% by mixture volume. Additional mixtures containing powdered rubber, crumb rubber, and tire chips were evaluated for their mechanical performance. Based on fresh concrete properties, compressive strength, modulus of rigidity, and impact resilience, mixtures were selected for a second investigative phase. In this phase, static and impact testing were performed on two sets of scaled beams. One beam set was produced with concrete containing 40% powdered rubber as a sand replacement and another beam set with a combination mixture incorporating rubber products of varying sizes (10% powdered rubber, 10% crumb rubber, and 10% tire chip) and 0.25% recycled steel fiber. Flexural performance improved initially with the inclusion of powdered rubber but decreased with increasing concentrations. Mixtures including recycled steel fibers at 0.25% outperformed industrial steel fiber mixtures in both flexural strength and impact resistance. For both the static and impact beams with the recycled powdered rubber and steel fibers in the combination demonstrated improved load distribution and load-carrying capacity, acting as a sufficient replacement for industrial steel fiber reinforcement.

This paper presents the results of an experimental study into the behavior of rubberized concrete-filled fiber-reinforced polymer tube (CFFT) columns, where the fiber-reinforced polymer (FRP) confining layer is prestressed by using an expansive agent (EA). The study focuses on utilizing the incompressibility property of rubber in improving the strength properties of crumb rubber concrete (CRC). A total of 27 CFFT columns were tested under axial compression and the effect of rubber content, prestress level, confinement amount and curing condition was studied. Different EAs with cement replacement ratios of 0%, 7.5%, and 15% were used to examine the influence of different levels of hoop prestress on the axial compressive behavior. The influence of amount of confinement was examined with specimens prepared with either one or two layers of CFRP. The influence of the curing condition was also examined by preparing half of the one-layer specimens with steel plates confining the specimens in the axial direction during curing. Finally, both flexible and stiff molds were used to examine the influence of mold stiffness on prestress development during curing. The lateral prestress provided by the expansive agent and FRP confinement was used to mitigate the typical strength reduction associated with CRC. The positive effect of this technique is two-fold. First, the pressure produced by the expansive agent compresses the cement paste and rubber particles together, reducing porosity and increasing interaction and interface friction between the rubber particles and cement paste. Second, rubber is generally considered nearly incompressible, with a Poisson's ratio of approximately 0.5, hence as the rubber is compressed in one direction, it expands significantly in the other directions. Using rubber in unconfined and non-prestressed concrete results in strength reduction; however, the combined effects of FRP-confinement and lateral prestress on CRC can lead to significant increases in the columns' axial stiffness and strength. The stresses and strains developed during curing for the expansive mixes were found to be considerably higher in CRC compared with conventional concrete (CC), indicating that an EA is more effective in developing prestress in rubberized concrete. Moreover, the mold stiffness was found to have a noticeable influence on the compressive strength of concrete. Using stiff molds resulted in unrealistic and unsafe strength evaluation and, hence, should be avoided if expansive concrete is used, or the results should be modified to account for the effect of confinement provided by the stiff molds. It was also observed that the confinement effect in CRC was higher compared with that of CC, which is due to the incompressibility of rubber. Finally, applying confinement plates to the ends of the concrete during curing had insignificant impact on the compressive behavior. Refereed/Peer-reviewed

In this study, four steel-concrete-steel (SCS) sandwich beams were tested experimentally under incrementally increasing cyclic loading. Each beam had a length of 1000 mm, and upper and lower steel plates with 3 mm thickness sandwiched the concrete core which had a cross section of 150 mm × 150 mm. Two of the beams were constructed out of Rubcrete with welded and bolted shear connectors, the other two beams were constructed with welded shear connectors and either conventional concrete or lightweight expanded clay aggregate (LECA) concrete. The performance of the SCS sandwich beams performance including damage pattern, failure mode, and load-displacement response were compared. The results showed that while Rubcrete was able to provide similar concrete cracking behaviour and strength to that of conventional concrete, LECA concrete degraded the strength properties of SCS. Using bolted shear connectors instead of welded ones caused high number of cracks that resulted in a reduced ductility and deflection capacity of the beam before failure.

This research focuses on producing and testing a type of geopolymer concrete as an alternative to the conventional Portland cement concrete. The proposed concrete incorporates lightweight expanded clay aggregate (LECA) and rubber from car tyre waste which results in the production of a new concrete: “geopolymer LECA-Rubcrete”. A total of ten geopolymer concrete mixes were produced using rubber and LECA as partial replacements of fine and coarse aggregates, respectively. Variables such as the ratio of geopolymer binders, LECA pre-treatment, concrete curing method, and mixing procedures were examined. Physical, mechanical, and durability tests were conducted including workability, compressive strength , drying shrinkage , water absorption, surface abrasion, and carbonation . This research aimed to provide the necessary information needed to develop lightweight geopolymer Rubcrete structures to reduce carbon emissions and move a step closer towards a greener future. The results indicated that lightweight geopolymer Rubcrete is a suitable alternative to lightweight conventional concrete with similar or better durability properties. The workability increased by 9% and 20% when using rubber and LECA, respectively; however, the compressive strength decreased by 32% and 67%, respectively. Using 25% slag to 75% fly-ash decreased the workability by 44% and increased the strength by 47%. Specimens cured in the ambient condition showed less strength compared to those cured in water. Heat + water curing showed less strength in all mixes, except in mixes with no lightweight materials and with high fly-ash content, which showed 16–21% strength increase. Of the tested mixes, geopolymer LECA-Rubcrete mix that has high slag content showed comparable or better performance than that showed by Portland cement LECA-Rubcrete mix in all measured characteristics.

Due to the high number of discarded end-of-life tyres around the world every year, the use of rubber waste in concrete has been researched for some years in normal and high strength concrete. Rubcrete is a type of concrete which is similar to conventional concrete, but uses scrap tyre rubber as a partial substitution for mineral aggregates. Lightweight concrete is another type of concrete with the advantage of reducing the self-weight of the structure. Utilizing rubber waste in concrete as a replacement of fine and/or coarse aggregates to produce lightweight concrete is of great interest as it can potentially provide a ductile lightweight concrete. This study investigates the possibility of using rubber waste, lightweight expanded clay aggregate (LECA), or a combination of both, in producing ductile lightweight concrete at the material level as well as the structural level. Fourteen concrete mixes were produced with different rubber content as replacement of fine aggregate volume, and different rubber/LECA content as replacement of coarse aggregate volume. The pre-treatment of the rubber/LECA particles using water, cement/silica fume paste, and cement/silica fume solution was also investigated. Three reinforced concrete beams with 130 mm × 230 mm cross-section and 1000 mm length were made out of selected mixes and tested under cyclic loading. Several rheological and mechanical properties, and structural performance characteristics were measured and compared. The results indicated that the LECA performs better than coarse rubber as a replacement for concrete coarse aggregate. Pre-treatment of fine rubber by soaking in water for 24 h had no significant effect on concrete slump; however, it increased the compressive strength by 15%. Rubcrete had an insignificant effect on the general behaviour of the reinforced concrete beams. Using LECA-Rubcrete decreased the strength and ultimate displacement of the reinforced beam by 22% and 21%, respectively compared with the Rubcrete beam. Refereed/Peer-reviewed

From the twentieth first century to date, the world has seen a rapid production of non-biodegradable materials like rubber with some having less than a decade expiry date such as vehicle tyres. This has generated enormous amount of solid waste which can be best managed by recycling methods; recycling in concrete is one possible means of achieving this goal since it's the single most widely used material in the world. Although concrete compressive strength is reduced by addition of rubber depending on the percentage of rubber added and the average size of rubber used as aggregate. This study investigates Rubberized Bama Gravel concrete (RBGC) when three varied contents of rubber (10%, 20% and 30% by mass) were used to replace the mineral aggregate for both fine and coarse rubber aggregates respectively as compared to the controlled mix. A mix ratio of 1:1½:3 and 1:2:4, and water cement ratio of 0.5 and 0.6 were respectively used during the investigation. Tests carried out on Bama aggregate were specific gravity, aggregate impact and aggregate crushing; and on concrete are workability, density and destructive compressive strength. The study has shown that rubberized concrete is weak in compressive strength. But they have good water resistance with low absorption, low shrinkage and high impact resistance.The reduction in compressive strength of 10% fine rubber aggregate is about 10% which could be used as a structural member, while others (20%, 30% fine rubber aggregate and 10%, 20%, 30% chipped rubber aggregate) cannot be used as structural members as there is a significant decrease in compressive strength of concrete but rather as floors, kerbs, blocks and other non-structural.Read Complete Article at ijSciences: V72018031624 AND DOI: http://dx.doi.org/10.18483/ijSci.1624

The paper presents the results of a research work aimed at assessing the long-term strength and elastic properties of rubberized concrete. The parameters of the research were the rubber replacement of fine aggregates and the age of testing the specimens. Compressive and splitting tensile strength of concrete cylinders were obtained at the age of 5 years, coupled with the static and dynamic modulus of elasticity of all concrete specimens. Additionally, the material damping coefficient was assessed by means of non-destructive tests. The density of the rubberized concrete decreases with the percentage replacement of natural sand by rubber aggregates. A significant drop in the values of density after 5 years was observed for specimens made with rubberized concrete. The static and the dynamic moduli of elasticity decrease with the increase in rubber content. A similar trend is observed for the compressive and tensile splitting strength.

A composite slab reinforced by profiled steel deck is a structural system where the longitudinal shear resistance between the steel deck and the concrete is the critical factor that governs the member capacity of the slabs under shear and/or flexural loads. Partially replacing concrete sand by crumbed rubber particles derived from used tyres to form crumb rubber concrete (CRC) can adversely affect the concrete mechanical characteristics; however, the plastic energy absorption and ductility of CRC have been shown to be improved. This paper presents an experimental study of large-scale composite slabs made of CRC or conventional concrete (CC) at similar compressive strength of 25 MPa that were tested under 4-point bending. Different shear spans and loading schemes were applied and tested in this study. The slabs were all 130 mm thick and had 3400 mm full span (800 mm shear span) for long slabs and 1800 mm full span (400 mm shear span) for short slabs. The overall performances, load carrying capacity, end-slippage, and interaction with steel of the tested CRC slabs were comparable or even better than those of the corresponding CC slabs, which indicated the viable substitution of CRC in composite slabs. Refereed/Peer-reviewed

This study presents the results of an experimental study on the cyclic compressive behavior of rubberized concrete under active confinement. Two different mixes of concretes with rubber replacement ratios of 0%, as a control mix, and 18% were prepared. The effects of the incorporation of rubber and the confining pressure on the cyclic compressive behavior of concrete were examined through tests of unconfined and actively confined concrete cylinders. The active confinement was applied by a Hoek cell at different confining pressures, including 5, 10, 15, 20, and 25 MPa. The results indicate that peak stress of concrete decreases, and the peak axial strain and corresponding lateral strain increase by incoporating rubber. The results also show that, at a given confining pressure, concrete exhibits a higher ductility under cyclic loading than that under monotonic loading.

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.

This study presents experimental results about the effect of incorporating waste rubber aggregates in combination with waste glass powder or silica sand powder obtained from dune natural sand, on the performances of cementitious mixtures. Rubber aggregates (RW) were used to replace crushed sand in concrete mixes with ratios of 10%, 20%, 40% and 60%, while glass powder (GP) and natural sand powder (SP) were used to replace 15% of the cement weight. Nine different forms of concrete with the separate wastes and with the combination of them were designed and prepared. The mixtures were characterized in the fresh and hardened states by means of workability, fresh density, compressive and tensile strengths, propagation of ultrasonic waves and deformability tests. The water/binder ratio and superplasticizer percentage of all mixtures were maintained constant. The results showed that the strength increased with the incorporation of glass powder and rubber aggregates, especially with 10% and 20% RW contents. In addition, the developed rubberized concrete with the incorporation of glass powder presented higher fresh density and deformability, compared to the cementitious rubberized mixtures without GP. Furthermore, the simultaneous incorporation of rubber waste and glass powder enhanced the concretes workability due to the low GP and RW water absorptions., Ministère de l′Enseignement Supérieur et de la Recherche Scientifique, République Algérienne Démocratique et Populaire, Programme National Exceptionnel, Algeria and acknowledge the financial support from the Laboratory of Construction Materials, University of Minho, Portugal, info:eu-repo/semantics/publishedVersion

This paper reports on an experimental study on nine Post-tensioned Segmental Retaining Walls (PSRWs). All the walls were post-tensioned and tested under incrementally increasing cyclic loading. Each test wall was constructed using four T-shaped precast concrete blocks, assembled on top of each other with dry joints. The integrity of the system was maintained using post-tensioning (PT). Different levels of PT forces were applied to investigate the effect of it. Different wall-footing interface materials were used including steel plate, concrete and neoprene pad. Conventional concrete and crumb rubberized concrete was used to investigate the effect of concrete properties on the structural behavior of retaining walls. Three walls with confinement (confined with either Carbon Fiber Reinforced Polymer (CFRP), steel reinforcement or steel face plate) were tested. The force–displacement responses, energy dissipation, post-tensioning stresses, gap rotation, lateral stiffness, and normal strains were observed and compared. The results from this study showed that the level of axial stress ratio, eccentricity of pre-stressing as well as the properties of the wall-footing interface material is critical to provide enough lateral strength and stiffness for engineering design of the PSRW. The wall with steel plate on compression face had the largest ultimate strength. The specimen having largest PT force generated largest initial and secant stiffness. Additional reinforcement of the bottom most segment is also required to avoid sudden failure and increase ductility in T-shaped blocks. Lateral stiffness increases in conventional concrete was much higher than rubberized concrete when PT force was increased. None of concrete confinement methods applied (CFRP confinement, steel reinforcement and steel face plate) affected energy dissipation characteristics of the tested walls. Using neoprene as the interface material for wall-footing significantly increased energy dissipation and concrete wall-footing interface showed more energy dissipation in comparison to steel interface material.Stiffness degradation of all walls had similar rate against wall lateral displacement. This paper concluded that the proposed segmental retaining wall system is potentially a practical alternative to accelerate the construction of retaining walls using precast concrete blocks. Refereed/Peer-reviewed

An experimental study was performed to investigate the possible use of crumb rubber concrete (CRC) for structural columns by evaluating the use of fibre reinforced polymer (FRP) confinement as a means of overcoming the material deficiencies (compressive strength). Five reinforced concrete columns having 240 mm diameter and 1500 mm shear span were tested under axial compression and incrementally increasing reverse cyclic loading. Three columns were constructed out of CRC with 0, 2 and 4 layers of carbon FRP and two were constructed out of conventional concrete with 0 and 2 layers of carbon FRP. The results of this study showed that at the same confinement thickness, the peak strength of the FRP-confined CRC column was slightly higher than that of the FRP-confined conventional concrete column, even though the base concrete compressive strength was less. However, its ultimate drift was slightly lower. Doubling the confinement thickness increased the peak strength and the ultimate drift of the FRP-confined CRC by 11.5% and 53.8%, respectively. By using 2 layers of FRP, the strength confinement effectiveness of the conventional concrete and the CRC were 1.11 and 1.13, respectively, however, the drift confinement effectiveness was 0.98 and 1.07, respectively. This investigation demonstrates that CRC provides an environmentally-friendly alternative to conventional concrete in structural applications. Refereed/Peer-reviewed

Inclusion of rubber into concrete changes its behavior and the established shape of its stress-strain curve. Existing constitutive stress-strain models for concrete are not valid in case of rubberized concrete, and currently available modified models require additional validation on a larger database of experimental results, with a wider set of influential parameters. By executing uniaxial compressive tests on concrete with rubber substituting 10%, 20%, 30%, and 40% of aggregate, it was possible to study and evaluate the influence of rubber content on its mechanical behavior. The stress-strain curve was investigated in its entirety, including compressive strength, elastic modulus, strains at significant levels of stress, and failure patterns. Experimental results indicated that increase of rubber content linearly decreases compressive strength and elastic modulus, but increases ductility. By comparing experimental stress-strain curves with those plotted using available constitutive stress-strain models it was concluded that they are inadequate for rubberized concrete with high rubber content. Based on determined deviations an improvement of an existing model was proposed, which provides better agreement with experimental curves. Obtained research results enabled important insights into correlations between rubber content and changes of the stress-strain curve required when utilizing nonlinear material properties. info:eu-repo/semantics/publishedVersion

Researchers investigated the utilization of crumb rubber aggregate recycled from waste tire in concrete to solve the problem of discarded tire and to produce a green sustainable concrete. However, a reduction in the mechanical properties due to crumb rubber inclusion occurs. Steel fiber rubberized concrete used in this study to provide a balance between the strength loss and sustainable issue. An investigation on the mechanical properties of rubberized concrete combined with hooked – end steel fiber is presented. Rubberized concrete with different replacement ratios of crumb rubber was incorporated in plain and steel fiber concrete mixes via partial replacement of fine aggregate. Four replacement ratios (17.5%, 20%, 22.5%, and 25%) were used to investigate the effect of the partial replacement of fine aggregate by crumb rubber on the mechanical properties of plain and steel fiber concrete. In both mixes, reduction in mechanical properties was observed to be proportionate with the increment of crumb rubber. Finally, a successful combination of steel fiber and crumb rubber was obtained due to improvement of strain capacity under flexural loading.

This paper presents the results of the first experimental study on the axial compressive behavior of the rubberized concrete under active confinement. Four different batches of concretes with rubber replacement ratios of 0%, 6%, 12%, and 18% were prepared. The effects of the rubber replacement ratio and confining pressure on the compressive behavior of concrete were examined through the tests of unconfined and actively confined concrete cylinders. The active confinement was applied by a Hoek cell at different pressures, including 5, 7.5, 10, 15, 20, and 25 MPa. The results indicate that the rubber content significantly affects the compressive behavior of actively confined concrete. An increase in the rubber content results in a decrease in the compressive strength and an increase in the axial and lateral deformability of concrete. It is found that the axial strength and strain of rubberized concrete increase with the confining pressure following a similar trend to that in conventional concrete. On the other hand, the rubber content affects the descending branch trend of the axial stress-strain curves of concrete under active confinement, with more shallow branches seen in concretes with a higher rubber replacement ratio. Refereed/Peer-reviewed

This paper reports on an experimental study carried out to understand the behavior of rubberized concrete at the structural application level and to numerically predict the behavior of rubberized concrete beams and columns. Four reinforced concrete (RC) beam specimens and four RC column specimens, made out of rubberized concrete having 0%, 6% 12% and 18% replacement of sand volume by crumb rubber, were fabricated to examine the effects of rubber content on their structural behavior. The beam specimens were tested under incrementally increasing cyclic loading and their performances including damage pattern, failure mode, force-displacement response and energy dissipation behavior were compared. The column specimens were tested under eccentrically monotonic loading and their behaviors were compared. This experimental study indicates that while by increasing the rubber content from zero to 18%, the material compressive strength reduced by about 31%, the reductions in the ultimate capacities of beam and column members (made out of the same concrete materials) were only about 6% and 12%, respectively. As the rubber content increased the compressive strain capacity increased. This study showed that adding rubber to concrete increased the viscous damping ratio and kinetic energy; however, it had adverse impact on the dissipated hysteretic energy. Refereed/Peer-reviewed

Due to the known loss of compressive strength experienced by crumb rubber concrete (CRC) compared with conventional concrete, there have been few applications explored to date for the structural use of these materials. This paper describes experimental work conducted to explore the possible future use of CRC for structural columns by evaluating the use of fibre reinforced polymer (FRP) confinement as a means of overcoming the material deficiencies (decreased compressive strength). The results indicated that the use of FRP to confine rubberized concrete effectively negates the decrease in strength, and retains the advantages of increased ductility that arise from rubberized concrete. This indicates promising potential for structural column applications, particularly in seismic zones. Refereed/Peer-reviewed

Double-skin tubular columns (DSTCs) have become a competitive candidate for column members due to their important advantages compared with conventional reinforced concrete columns, including their better weight-to-strength ratio and ease of construction. Using Rubcrete in hybrid DSTCs is of great interest due to the potential of this system to overcome the Rubcrete material deficiencies and to add more ductility, toughness, seismic resistance, confinement effectiveness, and environmentally-friendly features to that structural system compared to conventional concrete. In this paper, hybrid DSTCs made out of Rubcrete, sandwiched between a fibre reinforced polymer (FRP) tube and a steel tube, were tested. The examined variables were concrete sand or stone replacement ratio (0% and 20%), FRP wall thickness (1- and 2-layers), steel wall thickness (3.2 mm and 4.5 mm), void ratio (50% and 76%), and void shape (circular or square). The axial and lateral stress&ndash, strain responses were monitored, measured, and compared. According to this investigation, using Rubcrete in hybrid DSTCs can enhance the axial and hoop strain capacities, especially with fine rubber particles. It was also observed that the adverse influence of using rubber on column ultimate capacity was much lower in DSTC specimens, compared with that of unconfined Rubcrete columns. Therefore, using Rubcrete with fine rubber particles is recommended in DSTC structural columns.

Various works have been carried out on both the physical and mechanical properties of rubberized concrete in previous research. But the chemical composition of rubberized concrete has not been fully investigated. The scanning electron microscopy (SEM) and energy-dispersive x-ray spectrum (EDX) analysis were used to determine the element composition and the peak intensity of chemical elements in the waste rubber concrete. The SEM and EDX analysis results showed that, ferrous iron, oxygen, calcium, and silicon were the dominant elements, and these elements reduced as more waste rubber were added to the concrete. Carbon and sulphur elements increased as rubber crumbs were added to the rubberized concrete. The work concluded that the presence of rubber crumb in the concrete samples contributed to both mechanical and chemical changes in the property of rubberized concrete.

Crumb rubber concrete (CRC) has some known shortcomings in mechanical performance compared to conventional concrete, particularly with respect to compressive strength. Many previous researchers have tried to overcome the material deficiencies using different methods; however, the results have often been contradictory and highly variable. In this research, three methods to improve and then assess the mechanical performance of CRC have been examined namely, rubber pre-treatment using sodium hydroxide (NaOH) solution, using silica fume additives, and increasing concrete cement content. The effect of the rubber pre-treatment time (0–2 h), silica fume content (0–15%), and cement content (300–400 kg/m3) on CRC slump, short and long term compressive strength, and tensile strength were measured for fifteen concrete mixes prepared with 0% and 20% rubber content. Six 100 × 200 mm cylinders were prepared from each mix for evaluating the compressive strength at 7 and 28 days. Four additional 100 × 200 mm cylinders were prepared from two mixes for evaluating the compressive strength at 56 and 84 days. In addition, two 150 × 300 mm cylinders for each mix were prepared and tested to determine the indirect tensile strength at 28 days. The results showed that 0.5 h of rubber pre-treatment using NaOH solution, 0% of silica fume replacing cement by weight, and 350 kg/m3 cement content were the best alternatives in this assessment range to enhance the CRC performance. Refereed/Peer-reviewed

Emiroglu, Mehmet/0000-0002-0214-4986 WOS: 000358476400005 In this study, dynamic modulus of elasticity of self-consolidating rubberized concrete is evaluated by using results of ultrasonic pulse velocity and resonance frequency tests. Additionally, correlation between dynamic modulus of elasticity and compressive strength results is compared. For evaluating the dynamic modulus of elasticity of self-consolidating rubberized concrete, prismatic specimens having 100 x 100 x 500 mm dimensions are prepared. Dynamic modulus of elasticity values obtained by non-destructive measurements techniques are well agreed with those given in the literature. Scientific Research Projects Management Council of the Firat University of TurkeyFirat University [1933] The research described in this paper was financially supported by the Scientific Research Projects Management Council of the Firat University of Turkey (Project no. 1933).

Recycling waste tire rubber by incorporating it into concrete has become the preferred solution to dispose of waste tires. In this study, the effect of the volume content of crumb rubber and pretreatment methods on the performances of concrete was evaluated. Firstly, the fine aggregate and mixture were partly replaced by crumb rubber to produce crumb rubber concrete. Secondly, the mechanical and durability properties of crumb rubber concrete with different replacement forms and volume contents had been investigated. Finally, the crumb rubber after pretreatment by six modifiers was introduced into the concrete mixture. Corresponding tests were conducted to verify the effectiveness of pretreatment methods as compared to the concrete containing untreated crumb rubber. It was observed that the mechanical strength of crumb rubber concrete was reduced, while durability was improved with the increasing of crumb rubber content. 20% replacement of fine aggregate and 5% replacement of the total mixture exhibited acceptable properties for practical applications. In addition, the results indicated that the modifiers had a positive impact on the mechanical and durability properties of crumb rubber concrete. It avoided the disadvantage of crumb rubber concrete having lower strength and provides a reference for the production of modified crumb rubber concrete.