Behaviour of reinforced concrete members incorporating recycled rubber materials

Abstract

This thesis deals with the behaviour of concrete materials and reinforced concrete members incorporating recycled rubber particles, as a partial replacement for mineral aggregates. The research involves several experimental investigations on materials and members, coupled with detailed numerical simulations and parametric assessments. Tests on cylindrical material specimens focus on examining the uniaxial behaviour of rubberised concrete. The experimental investigation, combined with the detailed assessment of data from previous tests, show that the rubber particles influence the mechanical properties as a function of the quantity and type of replaced aggregates. A series of expressions and analytical models defining the mechanical properties of rubberised concrete are proposed. Further tests on confined rubberised concrete cylinders show that external confinement provides significant enhancement to the strength and deformation capacity of the material. The experimental behaviour of rubberised concrete members under shear loading is also investigated in this research. The design of an asymmetric four-point shear test set-up is discussed and a detailed account of test results on eighteen prismatic rubberised concrete members, with or without confinement, is presented. Close observation of specimens exhibiting shear-governed failure shows that rubber particles have a significant influence on the member shear resistance and force transfer mechanisms along the cracked interface. In addition to the material and shear tests, the experimental performance of large-scale beam-column members is examined in the thesis. Tests on fourteen large scale reinforced rubberised concrete members, subjected to lateral cyclic displacements and co-existing axial loading, are reported. The test results enable a direct assessment of key response characteristics of beam-column specimens. It is shown that members with rubber particles can offer a better balance between capacity and ductility compared to conventional reinforced concrete members. In addition, external confinement, such as using fibre reinforced polymer (FRP) sheets, can be adopted to recover the loss of strength and provide highly stable hysteretic response. Numerical simulations of all the test series are performed using nonlinear finite element analysis and validated against the corresponding experimental results. The numerical models are then used to conduct parametric studies in order to examine the effect of key material and geometric factors on the behaviour of rubberised concrete members. Based on the findings from the experimental and numerical investigations, a series of expressions to assess the key performance characteristics of rubberised concrete members are proposed in a form that is suitable for practical design application.