Effect of using mineral admixtures and ceramic wastes as coarse aggregates on properties of ultrahigh-performance concrete

Recent advancements in recycling have transformed nonrenewable resources into partially renewable resources. In line with these advancements, the application of wastes, including ceramics, as substitute aggregate materials for construction has elicited considerable research interest. Ceramic waste aggregates can be used to address complex problems, such as the shortage of materials in construction sites, and reduce environmental wastes. This study aims to investigate the effectiveness of replacing silica fume (SF) and metakaolin (MK) with cement to improve ultrahigh-performance concrete (UHPC) prepared using ceramic wastes as coarse aggregates. Eleven UHPC mixes with 10%, 20% and 30% proportions of either SF or MK were designed. The fresh, physical, mechanical and microstructure properties of these mixes were evaluated, and test results showed that replacing cement with either SF or MK can improve the mechanical and physical properties of UHPC. The use of this waste as construction material will yield substantial technical, economic and environmental benefits, particularly from the perspective of sustainable development. The results showed that replacing SF or MK is effective in improving the strength of UHPC, particularly when the SiO2/CaO ratio was increased to 2.98. The 28-day compressive strength of UHPC with SF increased from 133.1 MPa to 146.6 MPa due to the improved microstructure and denser matrix.