Fracture behavior of multi-scale nano-SiO2 and polyvinyl alcohol fiber reinforced cementitious composites under the complex environments

This paper aims to investigate the fracture properties and microscopic mechanisms of multi-scale nano-SiO2 (NS) and polyvinyl alcohol (PVA) fiber-reinforced cementitious composites (MNFRCC) in complex environments. The complex environment was the coupling effect of wet-thermal and chloride salt environments (CEWTSE) simu-lated by an environmental simulation test chamber. And the parameters of temperature, relative humidity (RH), mass fraction of NaCl solution, and action time were determined as 50 degrees C, 100 %, 5 %, and 30 d, respectively. The Double-K Fracture model (DKFM), boundary effect fracture model (BEM), and work fracture method (WFM) were used to reveal that PVA fiber and NS improved the fracture properties of MNFRCC under the CEWTSE. And when the contents of PVA fiber and NS were 1.2 % and 0.5 %, respectively, the fracture parameters were significantly improved. Based on the comparative analysis of DKFM and BEM, the reasonable fracture parameters could be obtained by linking them through the crack propagation length. Moreover, the fictitious crack growth lengths and characteristic cracks increased with the increase of PVA fiber contents. On the microscopic level, PVA fiber and NS improved pores, microcracks and interfacial transition zone in the MNFRCC.