Exploring the effect of graphene oxide on freeze–thaw durability of air-entrained mortars

Abstract

Air-entrained agent (AE) has been recognized as the best way for improving the frost resistance of cement materials. However, its foaming ability could reduce compressive strength significantly. To enhance freeze–thaw durability without sacrificing mechanical performance, this study carries out in-door experiments by adding graphene oxide (GO) into air-entrained mortars, based on which the mechanism is explored by microstructural and numerical analyses. The test results show that 0.03 wt% GO (optimal dosage) can improve frost resistance and compressive strength of air-entrained mortars by 18.9% and 41.9%, respectively. According to microscopic tests, both AE and GO can reduce spacing factor, while an opposite trend on porosity is observed when AE and GO are added into mortars. To predict frozen deterioration, a thermal-hydro-mechanical model considering the influence of GO on water transport and nucleation rules during freeze–thaw process is firstly proposed. It implies that both water flow and self-compression illustrate the freeze–thaw damage. Through validating against the experimental data, the proposed model is proved to be reliable on simulating the deterioration of air-entrained mortars upon freezing, especially in case of sheet-like nano additives. Numerical result indicates that frost resistance can be continuously improved with increasing GO content if nano dispersibility is ignored, and thus remarkable enhancement will be achieved with the development of dispersion technology.