High performance rubber concrete

Abstract

The fast development of the automotive industry after the Second World War led to the rapid accumulation of waste tyre rubber. Since 1963, finding applications for the use of waste tyres has become the center of attention for many researchers. Using waste tyres in concrete has been proposed by many researchers, but due to its flexibility combined with hydrophobicity, any structural applications of such concrete has been difficult to develop. The mechanical properties of concrete, such as its compressive strength, modulus of rupture and tensile strength, are adversely affected by the addition of rubber, but energy absorption and fire performance properties improve. This justifies studies on improving the bond between rubber and cement paste in rubber concrete to counteract the adverse effects on mechanical properties and this is the objective of the present research. In order to improve the mechanical properties of rubber concrete, this study attempted to treat rubber crumb with chemical solutions. Microstructural characterisation of untreated and treated rubber crumb were performed in order to investigate the effect of treatment on the rubber surface and to study the development of active groups on them. For this, using untreated and different chemically treated rubber in concrete, as a replacement of 3% of fine aggregates, the compressive strength of several mixes were investigated. By taking advantage of microstructural characterisation analysis, the bonding properties of different types of rubber concrete were studied to arrive at the best method of activation (treatment). The best treatment method found was the oxidisation of rubber crumb. This innovative method was developed further to treat the rubber surface in sufficient amounts, allowing its introduction into structural applications for rubber concrete. The method works based on thermal oxidation in the presence of air. A small amount of rubber crumb was oxidated in air at the laboratory of Western Sydney University. Microstructural characterisation of the heat treated rubber took place to ensure the activation of the rubber surface through looking at surface morphology and FTIR reactive spectra. Afterward, more than 40 Kg of rubber was thermally activated in a structural furnace to carry out the mechanical and structural testing of heat treated rubber concrete. In the next step, compressive strength of different percent of rubber concrete from 5% up to 30% of replacement sand with heat treated rubber were investigated to obtain the optimum percent of replacement. This part of the study was completed by taking SEM images, completing the microstructural analysis of heat treated rubber concrete. After arriving at the optimum percentage of replacing sand with heat treated rubber crumb, mechanical properties of the rubber concrete such as compressive strength, modulus of rupture and modulus of elasticity were examined according to Australian standards. In the next step, to improve the mechanical properties of heat treated rubber concrete, a new mix design was introduced and all the mechanical properties of this type of concrete were tested. Fire performance of heat treated rubber concrete and untreated rubber concrete were also compared with control concrete. Following, structural properties of heat treated rubber concrete in a beam-column joint under monotonic and cyclic load were investigated and compared to the control specimens. At the end, numerical modelling of control concrete was performed and checked against the experimental results. The results showed some inconsistency which relates to the properties of rubber and the way cracks propagate in rubber concrete. While deficiencies were analysed and discussed, detailed examination is suggested for future studies.

Date of Award	2019
Original language	English