Effect of graphene oxide on microstructure and micromechanical property of ultra-high performance concrete

Abstract

This paper aims to investigate the effects of graphene oxide (GO) on the microstructure and micromechanical properties of ultra-high performance concrete (UHPC) matrix and interfacial transition zone (ITZ) around the embedded steel fiber, and to reveal the working mechanism of GO, so as to fully understand the mesoscopic and macroscopic mechanical behaviors of GO reinforced UHPC. Mercury intrusion porosimetry (MIP) and backscattered electron microscopy (BSEM) were used to systematically study the microstructure evolution, and nanoindentation test was used to quantitatively characterize the microscale fracture toughness of UHPC matrix and ITZ. The results showed that GO induced more calcium-silicate-hydrate generation, which significantly reduced the porosity of the ITZ between steel fiber and matrix from 7.5-13.4% to 5.3%–10.5%, and promoted the homogenization of the microstructure. Due to the decrease of porosity and the bridge effect of GO nanosheets, the microscale fracture toughness in ITZ increases by 24.9% from 0.994 MPa m1/2 to 1.241 MPa m1/2 at the critical dosage of 0.04% GO, which is conducive to the improvement of the interface bonding between steel fibers and matrix, and thus increasing the macroscopic flexural strength of straight steel fiber UHPC and hooked-end fiber UHPC by 14.7% and 13.9% respectively.