Investigation into the ductile and damping behaviour of concrete incorporating waste tyre rubber
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Sustainable development has grown to be a major concern to the construction industry with the main effort and attention in recent times devoted to developing innovative solutions to preserve the environment and natural resources. One suggested approach in aiding the conservation of natural resources is to recycle waste material for innovative use in construction applications. This thesis reports on the fundamental findings of an investigation into an elastomeric modified concrete (EMC), in particular its ductile and damping performance. This first- of-its-kind-in-Australia EMC incorporates Styrene Butadiene Rubber (SBR) waste tyre granules as a partial replacement of fine and coarse aggregates. Another significant feature of this project is that until now 100% Portland cement plain concrete has been utilised to evaluate the mechanical performance of EMC reported in literature, however, in this study the use of a supplementary cementitious material, that of fly ash (FA), is suggested as a partial replacement of Portland cement to create a more environmentally friendly construction material. Moreover, in order to examine the improvement of adhesion properties between the SBR granules and the cementing matrix, a styrene butadiene (SB) copolymer emulsion has been introduced to the couple of mixes. In the first experimental work stage two sets of EMC were prepared; one with small SBR granules (1 to 4 millimetres) in proportions of 5%, 10% and 15% of the total weight of aggregates; the other with larger SBR granules (12 to 15 millimetres) in proportions of 2%, 4%, 6% and 10% of the total weight of aggregates. In order to evaluate the damping and ductility properties of concrete, several tests were conducted following Australian Standards (AS) and American Society for Testing and Materials (ASTM), including compressive strength, static chord modulus of elasticity, modulus of rupture and dynamic modulus of elasticity. Compared to the control concrete, EMCs demonstrated lower density (mass per unit volume) and higher air content with increasing additions of SBR granules to EMCs. Furthermore, the compressive strength was found to decrease with increasing additions of SBR granules to EMCs. In contrast, static chord modulus of elasticity (MOE) and modulus of rupture (MOR) of EMCs were found to increase compared to the control concrete. Unlike the control concrete, EMCs did not exhibit a brittle-like failure. In the second experimental work stage, five reinforced beams (two for four point bending and three for three point bending tests) were made based on Australian standards. There were two sets of tests conducted on beams: destructive and non-destructive. Four point bending and three point bending tests were used to investigate the static properties of beams. To evaluate dynamic properties, hammer test was carried out prior to initiation of loading and also after failure of beam in four point bending test. The stiffness and maximum load of the beams decreased with the addition of SBR granules, however, the damping ratio of the beams increased. The project also included simulation and modelling of static tests using analysis by computer programs. This study encompassed a large experimental component and through specific testing, the best performing materials is selected to achieve the highest damping-to-ductility ratio.
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