Experimental investigation on mechanical property and microstructure of ultra‐high‐performance concrete with ceramsite sand

Abstract As one of the most innovative cement‐based materials, the properties of ultra‐high‐performance concrete (UHPC) have been widely investigated. This paper experimentally studies the effect of ceramsite sand on the properties and microstructure of UHPC to develop a new UHPC with low apparent density. The effects of the volume ratio of ceramsite sand and steel fiber content on the properties of UHPC were also studied. Various experiments, including apparent density, compressive and flexural strength, and microstructural properties were conducted on UHPC with different mixing parameters. The results showed that the addition of 18% ceramsite sand effectively improved the mechanical strength, specific strength, and pore structure as well as the interfacial transition zone of UHPC. Steel fiber and ceramsite sand worked together to make up for the lack of lightweight porous aggregate so that even when 100% ceramsite sand was used to prepare UHPC, the compressive strength of concrete could still exceed 100 MPa, and had a lower apparent density than normal UHPC.