Effect Of Crumb Rubber Aggregate On Toughness And Impact Energy Of Steel Fiber Concrete

Theoretically, concrete properties such as toughness, ductility, and energy absorption capacity can be improved by adding crumb rubber aggregate from waste tires. Therefore, this intended research work is to support the lack of previous studies by focusing on toughness and impact behavior of concrete containing crumb rubber aggregates with steel fiber. Fine aggregates were partially replaced by crumb rubber at 5%, 10%, 15%, 17.5%, 20%, 22.5%, and 25%. Additionally, 0.5% by volume of hooked end steel fiber was used with an aspect ratio of 80 and 60mm in length. Several specimens including cylinders, beams and slabs were prepared to investigate the toughness and impact behaviour of steel fiber concrete containing crumb rubber. Other properties such as fracture energy, stress intensity, critical strain energy release rate, and J-integral were also investigated. A preliminary impact resistance of beams was obtained using 4.54 kg falling hammer whereas for impact behavior of plain and steel fiber-reinforced rubberized concrete, an instrumented machine of 2.5 kg falling load was used. Simulation was carried out using FEM with LUSAS V14 to predict load deflection behavior of these beams under impact load. A reasonable good agreement was attained between the predicted values and experimental results of impact test. It was noticed that the impact energy of concrete slabs under low-velocity falling iron ball has increased with the increase of crumb rubber in both normal and steel fiber concrete up to 20%. However, a reduction of impact energy was observed when the replacement ratio of fine aggregate by crumb rubber was more than 20%. In conclusion, rubberized concrete containing steel fiber has shown a potential better performance under impact load which could eventually promote healthy environment using recycled waste tires

A Comparative Study on the Flexural Behaviour of Rubberized and Hybrid Rubberized Reinforced Concrete Beams

This paper aims to investigate the flexural behaviour of the rubberized and hybrid rubberized reinforced concrete beams. A total of fourteen beams, 150×200 mm in cross-section with 1000 mm in length, were subject to a laboratory test over an effective span of 900 mm. The sand river aggregate was replaced by 10%, 12.5%, and 15% of crumb rubber (volume).   The hybrid structure contained two double layers: 1) rubberized reinforcement concrete at the top layer of the beam and 2) reinforcement concrete at the bottom layer of the concrete beam. The static responses by the flexural test of all the beams were evaluated in terms of their fresh properties, failure patterns, total energy, flexural strength, stiffness, and ultimate deflection, modulus of rupture, strain capacity, and ductility index. The results showed that there were improvements when the hybrid beams were used in most cases such as failure pattern, ultimate load, stiffness, modulus of rupture, and stress. The rubberized concrete beams showed improvements in the strain capacity as illustrated in strain gauges and stress-strain curves, toughness, ultimate deflection, and ductility index. The findings of the study revealed an improved performance with the use of the hybrid beams. This has resulted in the implementation of innovative civil engineering applications in the engineering sustainable structures

Cumulative Effect of Crumb Rubber and Steel Fiber on the Flexural Toughness of Concrete

Concrete properties, such as toughness and ductility, are enhanced to resist different impacts or blast loads. Rubberized concrete, which could be considered a green material, is produced from recycled waste tires grinded into different crumb rubber particle sizes and mixed with concrete. In this study, the behavior of rubberized steel fiber-reinforced concrete is investigated. Flexural performance of concrete beams (40

Lightweight Rubberized Concrete Slabs for Sustainable Road Pavements Serving Non-Auto Traffic

Non-auto transportation infrastructure, such as bicycle lanes and sidewalks, serves as an efficient means of public mobility. Improving the sustainable design and construction of the concrete slabs that compose such roads promotes environmental and economic benefits, spanning the usage of green sources of materials and reduced maintenance costs. In this study, an investigation into the application of recycled tires, also known as tire-derived aggregate (TDA), combined with rotary-kiln produced expanded clay (EC) as coarse aggregates in concrete, as well as their life-cycle cost assessment, are presented. The mechanical properties of concrete specimens with three different mix designs, i.e.,100% EC (MIX A or control mix), a mixture of 20% EC – 80% TDA (MIX B), and 100% TDA (MIX C) as coarse aggregates, were first derived through experimental tests. Impact-fatigue tests were then conducted on concrete slabs of MIX A, B, and C to evaluate their sustainability under several cycles of bicycle loads. The results showed that the TDA concrete has lower compressive and flexural strength, but it is more ductile than concrete with zero rubber content. Also, the results of impact-fatigue tests combined with a life-cycle cost analysis indicated the long-term benefits of constructing green and durable infrastructure using TDA on future investments in transportation

Flexural fatigue behaviour of recycled tyre polymer fibre reinforced concrete

The utilization of recycled tyre polymer fibre (RTPF) into concrete production is feasible to promote sustainable development and mitigate environmental pollution of global landfilled waste tyres. This paper for the first time presents an experimental study on flexural fatigue behaviour of concrete reinforced with mixed RTPF considering different fibre dosages (i.e., 1.2, 2.4, 4.8 and 9.6 kg/m^{3} ). Results indicate that with the presence of RTPF, the flexural strength of concrete was increased by 3.6-9.6%. The fatigue life of all mixtures followed the two-parameter Weibull distribution and can be accurately predicted using the developed double-logarithm fatigue equations. Concrete reinforced with 4.8 kg/m^{3} of RTPF presented the longest fatigue life under different failure probabilities. RTPF and polypropylene fibre (PPF) reinforced concrete exhibited similar fatigue failure mechanisms. 0.2-0.4% V_{f} of RTPF could substitute around 0.1% V_{f} of PPF in concrete considering overall static, dynamic and fatigue performance

Numerical Study of Concrete

Concrete is one of the most widely used construction material in the word today. The research in concrete follows the environment impact, economy, population and advanced technology. This special issue presents the recent numerical study for research in concrete. The research topic includes the finite element analysis, digital concrete, reinforcement technique without rebars and 3D printing

Properties and Performance of Concrete Materials and Structures

The Special Issue on “Properties and Performance of Concrete Materials and Structures” presents the current and relevant research and advances in the field of concrete composites, as well as covering a broad range of experimental studies in relation to high-performance, fiber-reinforced, self-compacting, and eco-efficient concrete materials and structures. Furthermore, analytical studies and numerical simulations are presented to show developments in the design methods of concrete composites. This Special Issue collects the most recent experimental techniques, analytical and numerical methods in relation to concrete materials and structures

Use Of Crumb Rubber To Improve Thermal Efficiency Of Construction Materials

Motivated by the tremendous trend toward green environment and to reduce the effect of scrap tires on the environment, this research is an attempt to find a practical and environmentally sound solution of the problem of scrap tires. A few literatures are available about the effect of crumb rubber on thermal conductivity (k-value) of mortar. Furthermore, almost there is no studies have considered the effect of crumb rubber on the thermal properties of gypsum materials. For this purpose, an experimental program was established to investigate the amount and size of crumb rubber (rubber obtained from recycling scrap tires) on the thermal properties of mortar and gypsum. Four levels of sand replaced with crumb rubber 10%, 20%, 30%, and 40% and three sizes of crumb rubber (#30, #10_20 and combination of both sizes) considered to make twelve rubberized mortar and eight rubberized gypsum specimens. The specimens tested for thermal conductivity using an apparatus constructed for this purpose. Water absorption and unit weight of rubberized mortar were tested. It was found that the size and the amount of crumb rubber had an effect on thermal properties of the specimens investigated. k-value decreased when amount of rubber increased. Thermal conductivity of rubberized mortar was13 – 28% lower than the ordinary mortar and rubberized gypsum was18 – 38% lower than the ordinary gypsum. The water absorption of mortar mixtures contained up to 20% of crumb rubber inclusion was lower than that of plain mortar. In regard of rubber particle size, courser rubber particles gave higher reduction in k-value if compared to finer size. The materials investigated in this research can be used as coating material to improve thermal insulation property of exterior walls.Two equations to predict k-value of mortar and gypsum consist of crumb rubber were proposed. Finally, finite element approach to convert amount of rubber used in each mixture to a layer of rubber was used to develop equations to estimate the k-value of mortar and gypsum containing crumb rubber

A self healing smart syntactic foam based grid stiffened sandwich structure

Syntactic foams are composite materials synthesized by dispersing microballoons in a polymeric, ceramic or metallic matrix. In the past three decades, syntactic foams have gained immense importance as a lightweight and damage-tolerant material when used in foam-cored sandwich structures. Because of the structural-length scale damages by low velocity impact such as tool drops, runway debris etc., sandwich structures usually have a very low residual structural capacity. Unfortunately, macro-length scale damage, in particular internal damage such as impact damage, is very difficult to repair. Therefore, there is a genuine need to develop impact-tolerant and self-healing syntactic foams which can be used as a core in sandwich structures. In this study, a new shape memory polymer (SMP) based syntactic foam was proposed, fabricated, characterized, and tested using DSC, TEM, SEM, and stress-controlled programming and free shape recovery by association with the foam cored sandwich. A micromechanics based model was employed to clearly visualize the microstructure and to quantify the geometrical and mechanical properties of the smart foam composite in the linear elastic region. An orthogrid stiffened SMP based syntactic foam cored sandwich was then fabricated, programmed, impacted, healed (sealed), and compression tested, for the purposes of sealing impact damage. Two impact energy levels (30J and 53J), two prestrain levels (3% and 20%), and two confinement conditions (2-D confined and 3-D confined) were used in the low velocity impact test, strain-controlled programming and constrained shape recovery, respectively. C-scan and visual observation were also conducted to visualize impact damage and evaluate the degree of sealing achieved. It is found that the shape memory functionality of the SMP based syntactic foam can be utilized for the purpose of sealing impact damage with the developed programming and shape recovery. The developed foam and the hybrid sandwich structure are able to heal (or seal) structural-length scale damage (here impact damage) repeatedly (up to 7 rounds of impact-healing cycles), efficiently (with a healing efficiency over 100%); and almost autonomously (the only human intervention is by heating). This study lays a solid foundation for the next generation of smart self-healing composite structures in engineering applications