Study on mechanical properties and microscopic mechanism of PVA fiber reinforced ultra-high performance concrete cured under different curing temperatures

In engineering, the effects of curing temperature on mechanical properties and fiber-matrix interface of UHPC are rarely considered. In this study, the effects of different curing temperatures on mechanical properties and microstructure of PVA fiber reinforced UHPC were studied. The results show that the compressive strength of UHPC with 2% PVA fiber cured at 90 ℃ for 3 d is the highest, reaching 148.0 MPa. The flexural and tensile strengths of UHPC with 2% PVA fiber are the highest after curing at 70 ℃ for 3 d and then standard curing until 28 d, reaching 20.1 MPa and 9.9 MPa, respectively. The adhesion and roughness of the fiber surface in UHPC cured at 70°C and 90°C are more than those at other curing temperatures, and the bonding between fiber and matrix is also closer, while there are more microcracks at 90°C and the matrix compactness is lower than that at 70°C. The UHPC with 2% PVA fiber and curing at 70°C for 3 d and then standard curing until 28 d has the lowest porosity.