Experimental Investigation on the Behaviour of Recycled Aggregate Concrete

The amount of construction and demolition waste has increased considerably over the last few decades due to growing construction industries. There has been an increasing trend toward the use of sustainable materials and reduce the consumption of non-renewable natural resources. Recycling and reuse of demolition concrete in construction is one potential solution to minimise the natural resources. Recently the main use of recycled concrete aggregate (RCA) is for non-structural applications such as in road sub-bases. However, research studies suggest that the natural aggregates can be partially or fully substituted by RCA if well graded and good quality RCA is guaranteed. The RCA concrete has a lower elastic modulus, compressive and tensile strength, and ductility and greater water absorption than natural aggregate (NA) concrete. Furthermore, the age of the concrete used as RCA has a vital effect on the mechanical properties of the recycled aggregate concrete. However, adding steel fibres (SFs) into RCA mix may improve its mechanical properties. The purpose of this study is to evaluate the percentage of RCA replacement and the age of original concrete on the compressive and tensile strength RCA at 7-, 14- and 28- days. Furthermore, this research will investigate the effect of steel fibre percentage and hook geometry on the compressive and tensile strength of NA to anticipate the effect of steel fibres on the mechanical properties of concrete made from RCA. To achieve that, a number of concrete cubes, cylinders with different percentage of RCA replacements and 3D and 5D hooked end SFs are casted to assess the compressive and tensile strength.