Effect of replacement of silica fume by wollastonite microfibers on ultrahigh performance concrete

Abstract

Ultrahigh performance concrete (UHPC) is a new type of cement-based composite building material with the characteristics of high strength, high toughness, and high durability. However, the presence of silica fume (SF) will greatly increase the cost of UHPC. Wollastonite microfiber (WF), a microfibrous inorganic mineral powder, has been shown to be effective in improving the mechanical properties of cementitious materials and reducing the cost of UHPC. In this study, a series of UHPC-WF were synthesized via replacing a part of SF with WF. The excellent smooth properties of the WF surface played a lubricating role in the UHPC-WF slurry, resulting in the fluidity of 287.5 mm for UHPC-WF. Furthermore, the synergistic effect of WF and steel fiber played a significant role in UHPC-WF. The flexural strength of UHPC-WF in 3 days and 28 days was 16.4 MPa and 21.6 MPa, respectively, and the compressive strength in 3 days and 28 days was 119.4 MPa and 155.3 MPa, respectively. Meanwhile, the shrinkage strain of UHPC-WF was only 0.13 mm/m in 90 days. This work provides consideration for the innovation of UHPC technology in the future and the research of replacement SF to mineral admixtures in UHPC.