Utilization of industrial wastes on the durability improvement of cementitious materials: A comparative study between FA and GGBFS

To satisfy the needs of both an increase of infrastructure construction and a reduction of CO2 emissions from cement manufacturing, industrial wastes like fly ash (FA) and ground granulated blast furnace slag (GGBFS) have been as substitutes for cement in cementitious infrastructure. This paper partially replaced cement in cementitious material by FA and GGBFS to improve its durability in the chloride and sulfate environments, and the influences of FA and GGBFS on its microstructures like C-S-H gel and binding behaviors of chlorides and sulfates were comparatively analyzed. Results show that, FA can cause an increase of the mean chain length and a reduction of the Ca/Si molar ratio of C-S-H gel, correspondingly changing its microstructure and reducing physical adsorption of cementitious material, but GGBFS has basically no influence on its C-S-H structure and physical adsorption. The hydration of FA can result in higher protonation and aggregation of C-S-H gel than that of GGBFS, and it has a stronger influence on the C-S-H structure than GGBFS, causing a reduction of the adsorption sites on the C-S-H surface. FA can reduce physical adsorption of chlorides and sulfates, but it is more beneficial for improving sulfate binding, while GGBFS is more favorable for improving chloride binding of cementitious materials. In addition, the physical adsorption capacity of cement pastes is associated with not only the structure of C-S-H gel but also its content in cementitious materials serviced in chloride and sulfate environments. This study supplies some insights on the effective incorporation of industrial wastes to improve the durability performance of cementitious materials.