Property degradation of seawater sea sand cementitious mortar with GGBFS and glass fiber subjected to elevated temperatures

Abstract

Abstract Effects of ground granulated blast-furnace slag (GGBFS) and glass fiber on the property degradation of seawater sea sand mortar (FSSM) after elevated temperature exposure were investigated in this study. The physical properties and mechanical strength of FSSM were compared with that of cementitious mortar prepared with demineralized water and river sand (FRRM). The results showed that when the mortars were exposed to normal temperature, the compressive strength of FSSM was higher than that of FRRM. GGBFS increased both the compressive and flexural strengths of FSSM, while glass fiber increased the flexural strength but slightly decreased the compressive strength. The maximum flexural strength of FSSM was achieved with 1 wt.% glass fiber and 30% GGBFS. After exposed to temperatures of 200 °C and 400 °C, the flexural and compressive strength losses of FSSM were lower than that of the corresponding FRRM, while the FSSM with glass fiber exhibited more compressive strength loss but less flexural strength loss compared to the FRRM. Additionally, GGBFS could densify the microstructure of FSSM, and decrease the losses of flexural and compressive strength after exposed to elevated temperatures. The calcium aluminosilicate hydrate (C–A–S–H) gels with higher ratios of Si/Ca and Al/Ca in the FSSM with GGBFS were significantly more stable at the temperature of 700 °C compared to the calcium silicate hydrate (C–S–H) gels with lower ratios of Si/Ca and Al/Ca in the FRRM or FSSM without GGBFS. Therefore, it can be included that the high temperature or fire resistance of FSSM can be improved by glass fibers and GGBFS.