Mechanical properties and microstructure of ultra-high strength concrete with lightweight aggregate
Lingqi Meng, Chunxiao Zhang, Jiuqi Wei, Lei Li, Jingbiao Liu, Shihe Wang, Yahong Ding
Abstract
In recent years, the development of concrete has been toward to the direction of lightweight and high strengthening. This study developed a kind of lightweight ultra-high strength concrete(L-UHSC) through the comprehensive design method, which had an apparent density rang of 1995kg/m3-2114kg/m3 and a compressive strength of 102.4 MPa-114.5 MPa. The specific strength of the designed L-UHSC is more than 50 MPa/(t/m3), which is higher than ordinary structural lightweight aggregate concrete (LAC). Additionally, the roles of high-performance paste, lightweight aggregate (LWA) and steel fiber in L-UHSC were revealed through scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP) and strength test. The findings revealed that SF content, rather than the binder-sand ratio and aggregate ratio, has a greater impact on density and strength, and the aggregate ratio having the least effect. As steel fiber content increases from 0.5% to 2.0%, compressive strength, flexural strength and splitting tensile strength of LAC increase by 44.3%, 120% and 151%, respectively, which is higher than that of ultra-high performance (UHPC). The micromorphology and pore structure research suggested that the high-performance paste plays a keystone role in achieving the ultra-high strength, and LWAs mainly affected strength through improving pore structure. In addition, small size pre-wetted LWA is more conducive to concrete strength. Our preliminary results provide a reference for the research and development of lightweight ultra-high strength cement composites.