Physio-chemical, mechanical and fracture analysis of ultra-high-performance cementitious composite

The aim of this research was to develop cost-effective and environmentally friendly ultra-high-performance concrete (UHPC) using fly ash (FA) and quartz powder (QP) as sustainable cement replacements. The performance of the various constituents was examined and their influence on fresh and hardened properties was investigated in order to determine the optimum trial mix design. A cube compressive strength of 144 MPa was achieved with 20% FA and 10% QP and other ingredients without any special heat treatment. Advanced characterisation studies, such as the heat of hydration and X-ray diffraction analysis, were performed to gain understanding of the performance of FA-blended UHPC. Various fracture properties (fracture toughness, fracture energy, brittleness etc.) were investigated considering geometrically similar notched beam specimens for UHPC mixes with steel fibre contents of 1.5% and 2.5%. The optimum UHPC mix achieved good scores in terms of the strength index and the embodied carbon dioxide emissions index, indicating that the concrete is eco-friendly and sustainable.