Abstract:Processing waste concrete into recycled sand, and using recycled sand to produce ultra high performance concrete(UHPC), different mechanical properties of UHPC were investigated by the standard test method by replacing natural river sand with recycled sand in different substitution rates. For the different mechanical properties of UHPC, the optimal substitution rate of recycled sand was in the range of 40%60%. The UHPC displayed high mechanical performance when the substitution rate of recycled sand was 60%. The compressive strength, flexural strength, splitting tensile strength, and elastic modulus of UHPC were 17026MPa, 1945MPa, 1217MPa, and 5065 GPa, respectively, which suggested that the compressive strength, flexural strength, splitting tensile strength, and elastic modulus of UHPC with recycled sand was 188%, 1288%, 827%, and 565%, higher than control group of UHPC. With the increase of substitution rate of recycled sand, the content of capillary pores in UHPC increased firstly and then decreased, which suggested that pore structure of UHPC with recycled sand was improved to some extent due to the addition of the recycled sand.