Effect of blending PVAF and BF on mechanical properties and microstructures of UHPC under high temperature curing

In this study, the effects of blending polyvinyl alcohol fiber (PVAF) and basalt fiber (BF) on the mechanical properties and microstructure of UHPC cured under high temperature were investigated. The results show that when the mixing ratio of PVAF and BF is fixed at 2 %, the compressive strength of UHPC decreases as the content of BF increases. A lower BF content significantly enhances the flexural strength of UHPC. When the BF content is 0.5 % and the PVAF content is 1.5 %, the flexural strength of UHPC reaches the maximum. Meanwhile, when the PVAF content is 0.5 % and the BF content is 1.5 %, the tensile strength of UHPC under high temperature curing reaches the maximum value of 10.2 MPa. Compared with the UHPC without fiber addition, it increases by 75.9 %, and is superior to the tensile strength of UHPC with only PVAF addition and UHPC with only BF addition. The interweaving of PVAF and BF can form a denser reinforcing network and jointly bear tensile stress, further enhancing the tensile strength of UHPC. The nucleation effect of PVAF can accelerate the cement hydration to generate more C-S-H, and the cement hydration around BF is promoted to a certain extent due to high temperature.