Abstract
Sulfate resistance of mortars containing limestone powder was investigated in a laboratory in which mortar specimens were continuously immersed in 33,800 ppm of sodium and magnesium sulfate solutions for 1,700 days. Mortars made from interground limestone and limestone powder, replacing cements with different proportions (10%, and 20% limestone by weight of the blended cement), were used to compare with the control Portland Type 5 cement mortar. Expansion and weight loss were measured. Microstructural analyses such as SEM, MIP, TGA and XRD techniques were also performed on the paste samples. It was observed that interground limestone cement specimens had higher expansion than the limestone powder replacing cement specimens due to smaller average pore size and lower total porosity, providing less spaces for depositing products of expansion. Contrary to the expansion, the specimens made from interground limestone cement lost less weight than those made from the limestone powder replacing cement because of lower average pore size and total porosity, making the specimens denser. For mortar containing limestone powder specimens in MS solution, the MS decreased the system' s pH. There occurred higher dissolution of CaCO3 from the limestone powder, which contributed to the formation of gypsum, magnesite and dolomite. This reduced the conversion of C-S-H to M-S-H, which resulted in less weight loss and less severe surface etching than the specimens made from OPC.
