Mechanical Properties of Nano-SiO 2 Reinforced Geopolymer Concrete under the Coupling Effect of a Wet-Thermal and Chloride Salt Environment.

In this study, the mechanical behaviors of nano-SiO 2 reinforced geopolymer concrete (NS-GPC) under the coupling effect of a wet-thermal and chloride salt environment were investigated through a series of basic experiments, and a simulation on the coupling effect of a wet-thermal and chloride salt environment and SEM test were also included. During the experiments for the coupling effect of the wet-thermal and chloride salt environment, an environment simulation test chamber was utilized to simulate the wet-thermal and chloride salt environment, in which the parameters of relative humidity, temperature, mass fraction of NaCl solution and action time were set as 100%, 45 °C, 5% and 60 d, respectively. The content of nano-SiO 2 (NS) particles added in geopolymer concrete (GPC) were 0, 0.5%, 1.0%, 1.5% and 2.0%. The result indicated that the mechanical properties of NS reinforced GPC decreased under the coupling effect of the wet-thermal and chloride salt environment compared to the control group in the natural environment. When the NS content was 1.5%, the cube and splitting tensile strength, elastic modulus and impact toughness of GPC under the coupling environment of wet-thermal and chloride salt were decreased by 9.7%, 9.8%, 19.2% and 44.4%, respectively, relative to that of the GPC under the natural environment. The addition of NS improved the mechanical properties of GPC under the coupling effect of the wet-thermal and chloride salt environment. Compared to the control group without NS, the maximum increment in cube compressive strength, splitting tensile strength and elastic modulus of NS-GPC under the coupling effect of the wet-thermal and chloride salt environment due to the incorporation of NS reached 25.8%, 9.6% and 17.2%, respectively. Specifically, 1.5% content of NS increased the impact toughness, impact numbers of initial crack and the ultimate failure of GPC by 122.3%, 109% and 109.5%, respectively.