Effect of untreated coal waste as fine and coarse aggregates replacement on the properties of steel and polypropylene fibres reinforced concrete

Abstract

This study aims to find a useful solution to reduce the negative influences of untreated coal waste (UCW) on the ecosystem of the region. UCW could however be identified as a practical solution in producing concrete aggregates. A total of 69 concrete mix designs with different contents of untreated coal waste as aggregates are prepared and slump, compressive and splitting tensile strength, flexural resistance, dry unit weight, the elastic modulus, water absorption and the electric resistivity of concrete are measured. In order to measure the influence of UCW as a partial replacement of natural coarse aggregates (NCA) and natural fine aggregates (NFA) on the properties of concrete, mixtures are cast in two groups. In the first group, NCA are substituted with untreated coal coarse aggregates (UCCA) at seven replacement contents: 0%, 5%, 10%, 15%, 20%, 25% and 30% (in term of mass). In the second group, NFA are replaced by untreated coal coarse aggregates (UCFA) at seven mass replacement values: 0%, 5%, 10%, 15%, 20%, 25% and 30%. Also, steel fibres (SF) and polypropylene fibres (PPF) are added to concrete mixtures at three contents: 0%, 1% and 2% (in term of volume) to reduce the negative influence of high replacement contents of UCFA and UCCA on both fresh and hardened characteristics of concrete. The results revealed that fibres considerably improve the compressive, tensile and flexural strength of concrete, and 10% of NCA or NFA could be substituted by UCCA and UCFA when 2% fibres (SF or PPF) are used with no reduction in the mechanical performance of concrete.