Durability Study of Silica Fume-mortar exposed to the Combined Sulfate and Chloride-rich Solution

The present article investigates the mechanism behind the sulfate attack of the Ordinary Portland Cement (OPC) and the Silica Fume (SF) based mortar exposed to the combined sulfate and chloride-rich solution. In this study, the control mortar sample was fabricated using OPC. Additionally, the silica fume based mortar composites were fabricated using SF replacing the 5, 10, and 15% of OPC. The 28 days cured control and silica fume based mortar samples were exposed to a sodium sulfate (5%) solution and a mixture of sodium sulfate (5%) and sodium chloride (3.5%) solution for 510 days to examine the deterioration of mortar samples by the sulfate attack. The results reveal that a less extent of deterioration takes place in the silica fume based mortar as compared to that of the OPC mortar exposed to both solutions. The retarded deterioration of silica fume based mortar is primarily governed by the formation of a less extent of expansive ettringite and gypsum due to the consumption of portlandite in producing secondary Calcium Silicate Hydrate (CSH). Based on the analytical analyses, a model has been proposed to explain the overall performances of the silica fume based cement mortar composites exposed to different aggressive environments.