Experimental and Predictive Study of the Flexural Behavior of Self-Compacting Rubberized Steel-Reinforced Concrete

This study experimentally investigates the mechanical performance and durability of Polyvinyl Alcohol (PVA) fiber-reinforced rubber concrete and the rubberized self-compacting concrete. The waste rubber particles were introduced as a partial replacement of fine aggregate in the plain concrete. In addition, the waste tire rubbers were pre-treated with alkali surface treatment method to enhance the performance. The PVA fibers were added to the concrete mixes to enhance the post-failure resistance and thus fracture energy. Rubberized fiber concrete samples were prepared with different fine aggregate replacement ratios and the optimum fiber content. At the same time, the rubber particles had been used to partially replace the fine aggregate in normal self-compacting concrete (SCC). The rubberized self-compacting concrete (RSCC) had also been prepared with different rubber contents. The effects of NaOH treatment method had been evaluated in the self-compacting concrete. For these samples, the mechanical performance including compressive strength, indirect tensile strength, and flexural behavior was measured to compare with control samples. The transport property was also detected by electrical resistivity test. The durability performance such as alkali-silica reaction (ASR) expansion and drying shrinkage were evaluated and compared with control samples. The test results of the PVA-fiber reinforced rubber concrete showed that it could achieve a high fracture energy and maintain xvi a high mechanical performance after addition of recycled rubber and PVA-fiber, furthermore, the modified specimens showed a better performance in durability than control samples. At the same time, the results from rubberized self-compacting concrete (RSCC) also indicated that after using of NaOH surface treated rubbers can successfully achieve high-strength requirement and improve durability performance. Overall, the polyvinyl alcohol (PVA) fiber could be considered to improve the mechanical performance and durability in normal rubberized concrete. In addition, the NaOH surface treatment method for rubber particles could improve the performance of rubberized self-compacting concrete (RSCC), thus achieve a high-strength and good durability with the recycled tire aggregate.

3D mesoscale modeling and fracture property study of rubberized self-compacting concrete based on uniaxial tension test

With the accelerated accumulation of scrap tires, the landfill becomes unacceptable due to limited space and its environmental pollution. The rubberized concrete materials containing scrap tire rubber particles as partial replacement of aggregates have been considered as one applicable method to recycle waste tire. However, the mechanical and durability properties of concrete materials can be significantly affected by adding rubbers without optimized designs. The main objective of this research is to develop the optimized designs for fiber-reinforced rubberized normal concrete and rubberized self-consolidating concrete through experimental evaluation of fresh performance, mechanical property, and durability resistance. For fiber-reinforced rubberized normal concrete, steel fibers and plastic fibers were added along with recycled rubber aggregates. The results showed steel fibers could improve compressive strength, splitting tensile strength, and flexural strength of rubberized normal concrete. In the case of plastic fibers, reduced compressive and flexural strength were found by comparing with that of control specimens. However, the fracture energy and post-crack extension were significantly improved by comparing that of control specimens in fiber-reinforced rubberized normal concrete samples regardless of fiber types, especially the fracture energy was increased about 10 to 50 times. The steel fiber-reinforced self-compacting rubber concrete (SRSCC) was also designed by introducing steel fiber and recycled rubber aggregates into self-compacting concrete (SCC). The experimental results showed the SRSCC can meet most requirements of fresh performance (flowability, filling ability, and passing ability) in terms of field applications. Regarding hardened properties, the compressive strength was reduced with the added rubber aggregate and steel fiber. However, SRSCC samples with 10% rubbers showed higher splitting tensile strength than that of plain SCC samples. The Load-crack mouth opening displacement (Load-CMOD) curves showed the increased flexural strength and total fracture energy of SRSCC samples with added steel fiber by comparing that with plain SCC. The critical fracture parameters, including initial fracture energy (Gf) and stress intensity factor (KІc) were increased with added rubber aggregate and steel fiber. With these properties, the bilinear strain-softening model (aggregate interlock effect) and trilinear strain-softening model (aggregate interlock and fiber-bridging effects) were calibrated. The strain-softening curves were utilized in the ATENA finite element model (FEM) to predict the flexural-fracture behaviors of corresponding specimens, and the simulation showed reasonable agreement with experiments. Also, the SRSCC specimens showed excellent freeze-thaw resistance after 600 F-T cycles. In the future, the success of applying fiber-reinforced rubber concrete materials could be an environmental-friendly utilization for recycling solid tire

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.

Recycling rubber and/or steel fiber components of waste tires in construction applications is a venue for maximizing the recycling rate of these items. Additionally, it supports the move towards producing sustainable construction materials and conserving natural resources. Previous research explored the viability of employing recycled waste rubber particles as an alternative for natural aggregate. Despite the adverse effect of rubber on the mechanical properties of concrete (e.g., lower compressive strength), it produces several advantages, including excellent dynamic and ductility properties, which can be utilized in structural members critical to dynamic loads, e.g., blasts, earthquakes, and impacts. In an effort to expand the adoption of waste rubber in concrete beams and to eliminate key concerns associated with the degradation of their flexural behavior, the functionally graded (FG) beams concept was utilized. The present investigation comprised the testing of five beams using a four-point bending configuration. Plain concrete, rubberized concrete (RuC), and steel-fiber reinforced rubberized concrete (SFRRuC) beams were cast along with FG beams arranged in two layers. The top layer of the FG beams comprised plain concrete, while the bottom layer consisted of RuC or SFRRuC. Experimental findings indicated that the flexural behavior of the FG beam with layers of SFRRuC and plain concrete exceeded the flexural strength, displacement ductility ratio, and toughness performances of the plain concrete beam by 9.9%, 12.9%, and 24.4%, respectively. The moment-curvature relationship was also predicted for the tested beam and showed an excellent match with the experimentally measured relationship.

Reinforced concrete (RC) beams with vertical openings are becoming more frequent in new construction to transport numerous services, particularly in structures with restricted height and size. A significant lack of studies was observed to investigate the influence of a vertical opening in the shear zone on the RC beams' behavior and performance. This research investigated experimentally the performance of RC beams with vertical openings at the shear zone, whether these beams were cast with self-compacting concrete (SCC) or rubberized concrete (RUC). In addition, the purpose of this work is to compare the influence of steel fiber (SF) on the performance of vertically perforated SCC beams with its influence on the performance of vertically perforated RUC beams. The impact of the number of vertical openings and the SF ratio used in beam specimens on the beam behavior, including compressive and tensile strengths, crack patterns and modes of failure, maximum deflection, stiffness, loading capacity, and ductility, was evaluated in the current paper. The experimental findings demonstrated that the existence of vertical openings at the shear zone of SCC and RUC beams resulted in a decrease in stiffness with ratios ranging from 10.43 to 66.98%, maximum loading capacity with ratios ranging from 10.66 to 37.73%, and ductility index with ratios ranging from 2.14 to 21.53% compared to the solid beams. It also has a tangible impact on raising the maximum mid-span deflection at the ultimate load, ranging from 2.03 to 81.64%. Moreover, when the number of vertical openings increased, the cracks increased at the shear span in which the openings were located. In general, adding SF to the SCC mixture showed a more significant effect on enhancing the tensile and compressive strengths, stiffness, and ultimate load compared to that in the case of the RUC. For example, the stiffness and ultimate load of the solid SCC beam with a SF ratio of 1% increased by 164.58% and 70.19%, respectively, compared to the solid SCC beam without SF, while those of the solid RUC beam with the same ratio of SF increased by 69.91% and 61.85%, respectively.

The effect and optimization of using self-compacting rubberized concrete was investigated by using Taguchi method. Design of experiment was performed via orthogonal array to accommodate four factors with four levels. These factors were the percentage of fine rubber, coarse rubber, fly ash and viscocrete in the concrete mix. The signal-to-noise (S/N) ratio and the analysis of variance (ANOVA) were employed to study the performance characteristics of self-compacting rubberized concrete (SCRC). Rubberized concrete can be improved using the concrete proportioned as self-compacting concrete. The results indicate that there was a reduction in the strength with increasing rubber content but there was an increase in impact resistance. However, the replacement of 10% of coarse aggregate with coarse rubber gave more strength than that of zero rubber mix by 124% at 90 days. Replacement of 20% of both fine and coarse aggregates with fine and coarse rubber respectively, increased impact resistance by 453% compared to the corresponding SCRC control mix.

Improving shear behavior of rubberized concrete beams through sustainable integration of waste tire steel fibers and treated rubber

This work investigates the mechanical properties of conventional concrete (CC) and self compacting concrete (SCC) using fine rubber and silpozz were accompanied by a comparative study between conventional rubberized concrete (CRC) and self compacting rubberized concrete (SCRC). Fine rubber (FR) from scrap tires has replaced the fine aggregate (FA) and Silpozz has been used as a replacement of cement at the proportions of 5, 10 and 15%. Silpozz as a partial replacement of cement in addition of superplasticiser (SP) increases the strength of concrete. Fresh concrete properties such as slump test, compaction factor test for CRC, whereas for SCRC slump flow, T500, V-funnel, L-box, U-box, J-ring tests were conducted along with the hardened properties tests like compressive, split tensile and flexural strength test at 7, 28 and 90 days of curing. The durability and microstructural behavior for both CRC and SCRC were investigated. FR used in the present study is 4.75 mm passing with fineness modulus 4.74.M30 grade concrete is used with a mix proportion of 1:1.44:2.91 and w/c ratio as 0.43. The results indicate that as FR quantity increases, workability of both CRC and SCRC decreases. The results also show that the replacement of natural fine aggregate (NFA) with FR particles decreases the compressive strength with the increase of flexural strength observed upto 5% replacement of FR. Also replacement of cement with silpozz resulted enhancement of strength in SCRC.

The present study is carried out an experimental investigation on both fresh and hardened properties of conventional and self compacting concrete (SCC) containing waste tyre rubber. A comparison study between conventional rubberised concrete (CRC) and self compacting rubberised concrete (SCRC) is carried out. In both CRC and SCRC, the replacement of rubber varies from 0 to 20 % with coarse aggregate. The rubber chips of size 5 and 10 mm are used. The total volume of rubber chips are replaced in coarse aggregate i.e. 40 % from 5 mm size and 60 % from 10 mm size. The mix design of conventional concrete was targeted for M30 grade of concrete. The mix proportion of the concrete was 1:1.03:2.37 with water cement ratio of 0.375. CERA HYPERPLAST XR-W40 high end super plasticisers are used for the production of SCRC. The test results indicate that there was a reduction in the strength of CRC as compared with the SCRC. However, in both CRC and SCRC the replacement of 5 % rubber chips with coarse aggregate gives more strength than other replacement.

Recycled rubber particles can be produced by using waste tires. Adding recycled rubber particles to concrete can form rubber concrete (RC). RC can not only reduce the amount of natural sand and reduce the cost of concrete but also improve the static compressive toughness of concrete. Adding steel fiber into RC can improve the strength of concrete. In order to study the compressive toughness of steel fiber rubber concrete (SFRC), rubber particles washed with NaOH are added to steel fiber reinforced concrete. This can enhance the bonding performance between the recycled rubber particles and concrete. The volume ratio of recycled rubber is 5, 10, and 15%. Prismatic and cubic test blocks were prepared and their compressive tests were carried out. The results show that the stress interaction between the rubber particles and steel fiber in concrete significantly improves the compressive strength, elastic modulus, and stress–strain relationship of concrete. The compressive toughness and ductility of concrete are improved. When the content of rubber particles is 15–20%, the compressive toughness of SFRC is improved most obviously. Through experiments, the toughness index and specific toughness of rubber steel fiber reinforced concrete are calculated, which explores a new way and method for studying the compressive toughness of similar recycled material concrete.

The shear strength of concrete beams manufactured from a mix including fine pieces of waste tire rubber (rubberised concrete) have been studied in several experimental programmes, with results showing a reduction in shear strength when using rubberised concrete instead of conventional concrete. In much of the recent research in this area. The main goal of the current investigation was thus to determine the extent of such reduction and to find ways to compensate for this reduction by the addition of steel fibre. A total of eight rubberised concrete beams of (140 mm width, 240 mm height, and 1240 mm length) were tested experimentally with replacement ratios by volume fraction of coarse and fine aggregate volume with fine tire waste of 0%, 25%, and 50% investigated. Additions of, 0%, 0.5% and 1.5% steel fibre content were also made to the rubberised concretes, in an attempt to test improvements in the resulting shear strength. A four-points load testing configuration was used for testing the specimens. The compressive strength of the rubberised concrete, volume fraction of steel fibres, longitudinal reinforcement ratio, replacement ratio of conventional aggregate by fine waste rubber, and shear span to depth ratio were the variables considered in this investigation, with the load-deformation behaviour and ultimate load investigated through experimental work. The test results showed that an increase in replacement ratio from 25% to 50% reduced the shear strength by 3.4%, while adding 0.5% steel fibre to the rubberised concrete increased the shear strength by 7.4% as compared with that of conventional strength concrete specimens without steel fibre. Overall, the shear modes of failure in rubberised concrete were similar to those of conventional concrete.

Effect of rubber surface treatment on damping performance of rubber-mortar ITZ in rubberized concrete

Compressive behavior of rubberized concrete under high strain rates

One of the world's largest tire graveyards is located in the Al-Salmi area of Kuwait, where over 42 million discarded waste rubber tires have been accumulated over a time period of 17 years. This study aims to develop sustainable, cost-effective building materials for the construction industry, utilizing waste rubber as a partial substitute for fine and coarse aggregates in concrete mixtures. Three types of untreated rubber particles were used: powder rubber (P) with a diameter between 0.4 and 0.6 mm, crumb rubber (CR) with a diameter between 0.6 and 2 mm, and 2.6 and 3.5 mm respectively, and rubber chips (CH) with a diameter ranging between 2 and 18 mm. Fine aggregates were replaced by P and CR, while coarse aggregates were replaced by CH, at a substitution rate of 10 and 20% by volume. The impact of rubber particles on workability was assessed on fresh rubberized concrete, while the compressive strength was evaluated at 7, 14, and 28 days. Microstructural analysis using Scanning Electron Microscopy (SEM) was also conducted to collate the macroscopic behavior with internal structural changes. The results showed that increasing the rubber content and particle size led to reductions in workability and compressive strength. Large rubber particles, particularly chips, caused gaps and microcracks in the matrix, exhibiting poor adhesion at the Interfacial Transition Zone (ITZ). These findings demonstrate the potential of rubberized concrete as an eco-friendly alternative, with optimization needed for practical applications.