The mechanical property and microstructure of ultra-high performance lightweight concrete

Abstract:

Ultra-high performance lightweight concrete (UHPLC) is a new type of cement-based structural material with a density of less than 1 950 kg/m³ and is composed of high-strength cement paste,cenospheres, and fibers.This study investigated the effects of different curing systems and curing ages on the mechanical properties of UHPLC, which includes compressive strength, tensile performance, and flexural performance.Besides, the microscopic morphology of the cenospheres was also observed by scanning electron microscopy (SEM).Results show that, the compressive strength, tensile strength and bending peak strength increased obviously as the curing age increased, and UHPLC exhibited strain-hardening behavior.It indicates that curing age has a significant effect on the strength of UHPLC matrix and the interfacial bond strength between fiber and UHPLC matrix.High-temperature steam curing for 3 days, which can make the compressive strength and bending properties of the UHPLC matrix to the level of standard of curing for 28 days,can promote early strength development and shorten the curing age. However, it contributed less to the bond strength, which is still mainly affected by age.The actual density of UHPLC was 1 815.2 kg/m³ and its cubic compressive strength reached 103.1 MPa. During direct tensile test, its ultimate tensile strength and ultimate tensile strain was 7.60 MPa and 0.431% respectively, and it exhibited strain-hardening behavior. Moreover, its bending strength reached 22.43 MPa, meeting the strength demand of RPC160.The required lightweight and high-strength cement based structural materials has been achieved.