Cyclic Compression Behavior of Concrete-Filled Hybrid Large Rupture Strain FRP Tube

This paper experimentally investigates the behavior of concrete-filled-fiber-reinforced polymer (FRP) cylinders under cyclic axial compression. The FRP used in this study were either large rupture strain FRP (LRS-FRP) or hybrid LRS-FRP and conventional glass FRP (GFRP). LRS-FRP are manufactured out of polyethylene naphthalate (PEN) and polyethylene terephthalate (PET) obtained from recycled plastics. Hence, they are much cheaper and environment-friendly than conventional GFRP or carbon FRP (CFRP). LRS-FRPs has high tensile rupture strain (usually greater than 5%) compared to 1-2% for GFRP and CFRP. This study presents the results of 4 specimens with different confinement ratios to investigate the behavior of concrete-filled LRS-FRP or hybrid LRS-FRP and GFRP tubes in terms of ductility, ultimate strain, and strength improvement. The results showed that using LRS-FRP significantly improved the ductility of the confined concrete. However, the improvement in strength was limited. The hybrid confinement improves both the ductility and strength

Numerical Investigation on Hollow Pultruded Fibre Reinforced Polymer Tube Columns

As the axial behaviour of hollow pultruded fibre reinforced polymer (PFRP) profiles is governed by the instability conditions due to the local and global buckling, the determination of the safe load carrying capacity of FRP columns is vital. The compressive performance of PFRP tube depends on many factors such as fibre type, fibre content, and orientation of fibre layers, cross-section, thickness and height of the column member. In this study, concentric compressive testing was conducted using PFRP short columns. Based on the fibre orientation and thickness, the samples were divided into two groups of tubes in a square shape and two groups in a circular shape. The height of columns is designed to keep the slenderness ratio (length/lateral dimension) of 5. The axial behaviour of FRP columns was simulated using STRAND7 finite element software package. The laminate method was followed to define the mechanical properties of the FRP material. Failure was investigated by using the Tsai-Wu failure criterion. The experimental results show that the failure mode of the hollow square tube was either local buckling or corner splitting at the mid-height followed by buckling. Although both types of circular tubes failed in a similar way by crushing one end with high noise, followed by separation of the crushed end into strips, the stiffness and the load capacity of PFRP column was higher for the profiles with fibres oriented close to the axial direction. The numerical results are in close agreement with the peak value of the experimental results. This can be extended to study the effects of all factors that influence the axial behaviour of PFRP columns numerically

Prediction of crumb rubber concrete strength

In recent years, a very important environmental issue all over the world is the disposal of waste tyres. Rubber from waste tyres can be used to replace part of the natural aggregates in conventional concrete, resulting in a product called crumb rubber concrete (CRC). CRC can improve ductility, damping ratio, and energy dissipation, which are the most important parameters in concrete structures resisting earthquakes. However, CRC can have lower compressive strength when compared with conventional concrete. This paper presents an empirical model able to predict CRC compressive strength. The proposed model is verified using 148 different CRC mixes and compared to two previous models. The proposed model resulted in CRC strength predictions with only 10.7% mean error. The proposed model reduced the mean error in the predictions by 24.6% compared to the nearest predictions by previous models. This paper can aid structural designers who are considering using CRC as a promising alternative to conventional concrete in seismic zones

Bond behaviour between crumb rubberized concrete and deformed steel bars

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.Rebecca J. Gravina, Tianyu Xie, Rajeev Roychand, Yan Zhuge, Xing Ma, Julie E. Mills, Osama Youss

A comprehensive review on the mechanical properties of waste tire rubber concrete

Recycling of End of Life Tyres (ELT) is one of the major environmental concerns faced by the scientific community and the government organisations worldwide. Every year, an estimated one billion tyres reach their end of life, out of which only about 50% are currently being recycled and the remaining form part of the landfills. Therefore, there is an urgent need to improve the existing and develop new applications of recycled tyre products to address this shortfall in the utilisation rate of the ELT. One application which is actively being researched is the use of waste tyre rubber as a partial replacement of conventional aggregates in concrete applications. Although it shows tremendous potential, it comes with its own challenges such as weak inherent strength of the rubber and poor bond performance with the cement matrix, which hinders its use as an aggregate in large quantities. To overcome this challenge, researchers have looked at various rubber treatment methods that not only improve the bond performance but also significantly improve the mechanical properties of rubber concrete. This review paper considers the effect of rubber particle size, percentage replacement and various treatment methods on different mechanical properties of rubber concrete, studied over the last 30 years. However, to be accepted by the concrete industry, the researchers have to come up with a rubber treatment method that can address the concerns of high flammability and the resultant release of noxious gases from the rubber particles, when exposed to fire

Experimental study on enhancing the main characteristics of crumb rubber concrete

The use of rubber particles as partial fine aggregate replacement to produce crumb rubber concrete (CRC) can have an adverse effect on some of its mechanical properties, such as strength. Researchers have used a range of methods to overcome the material deficiencies, however the results have often been contradictory and highly variable. In this paper, the effects of many different rubber chemical pre-treatments on CRC workability, compressive strength, tensile strength, and flexural strength were measured. The rubber pretreatments utilized chemicals such as Sodium Hydroxide (NaOH), Hydrogen Peroxide (H2O2), Sulfuric acid (H2SO4), Calcium Chloride (CaCl2), Potassium Permanganate (KMnO4), Sodium Bisulfite (NaHsO3), and Silane Coupling Agent. Soaking rubber particles in tap water or running them through water before mixing were also tried as pre-treatment of rubber particles. X-ray photoelectron spectroscopy (XPS) analysis and scanning electron microscope (SEM) imaging of some of the pre-treated rubber particles were carried out. The results showed that mixing rubber with dry cement before adding to the mix increased the compressive strength by up to 3%. Pretreatment using water was more effective than other chemicals in enhancing the CRC workability. Regardless of the treatment material type, the longer the time of the treatment the more cleaning of rubber occurred

Influence of Mixing Procedures, Rubber Treatment, and Fibre Additives on Rubcrete Performance

This research extensively investigates how to enhance the mechanical performance of Rubcrete, aiming to move this type of concrete from the laboratory research level to a more practical use by the concrete industry. The effects of many different mixing procedures, chemical pre-treatments on the rubber particles, and the use of fibre additives, have been investigated for their impact upon Rubcrete workability, compressive strength, tensile strength, and flexural strength. The mixing procedure variables included mixing time and mixing order. The rubber pre-treatments utilized chemicals such as Sodium Hydroxide (NaOH), Hydrogen Peroxide (H2O2), Sulphuric acid (H2SO4), Calcium Chloride (CaCl2), Potassium Permanganate (KMnO4), Sodium Bisulphite (NaHsO3), and Silane Coupling Agent. Soaking rubber particles in tap water, or running them through water before mixing, were also tried as a pre-treatment of rubber particles. In addition, the effects of fibre additives such as steel fibres, polypropylene fibres, and rubber fibres, were assessed. X-ray photoelectron spectroscopy (XPS) analysis was utilised to examine some of the pre-treated rubber particles. The results showed that doubling the net mixing time of all mix constituents together enhanced the Rubcrete slump by an average of 22%, and the compressive strength by up to 8%. Mixing rubber with dry cement before adding to the mix increased the compressive strength by up to 3%. Pre-treatment using water was more effective than other chemicals in enhancing the Rubcrete workability. Regardless of the treatment material type, the longer the time of the treatment, the more cleaning of rubber occurred. Significant Rubcrete flexural strength increase occurred when using 1.5% fibre content of both steel fibre and polypropylene fibre

Novel approach to improve crumb rubber concrete strength using thermal treatment

The concept of using crumb rubber as a partial replacement of natural aggregate in concrete to produce rubberised concrete and reduce environmental impacts has been a subject of research for many years. A plethora of studies have investigated various methods to improve the rubberised concrete strength using different pre-treatment methods for the rubber particles and/or using other additives for general concrete strength enhancement. However, the efficiency and applicability of these methods have been quite inconsistent and in some cases in conflict with each other. This study presents a novel approach to pre-treating crumb rubber particles using thermal treatment at 200 °C before incorporation into concrete. Heating time, rubber size, and rubber content were the variables in this experimental investigation. Scanning electron microscope (SEM) investigation was carried out on both as-received and thermally-treated rubber particles, as well as crumb rubber concrete (CRC) specimens. The results showed promising enhancements in concrete performance compared with the previous work findings. At 20% rubber content using size #40 mesh thermally-treated rubber, the compressive strength recovered by 60.3%