Influence of some admixtures in mitigating the effects of sodium and magnesium sulphate attack in cement mortars

In this paper, results from the efforts to improve the sulphate resistance of cement mortars by incorporating chemical and mineral admixtures are described. The experiments reported in this paper include physico-mechanical tests, thermal analysis by DSC, and backscatter SEM. The first section of the paper compares the performance of the air-entrained and pozzolanic mortars to the PC mortar. The second part of this paper deals with the effects of sodium citrate on the properties of the PC mortar subjected to sulphate attack. Entrained air voids resulted in reduction of the expansive stress and corresponding deterioration. Silica fume at 10% replacement was effective in reducing the extent of attack even in magnesium sulphate solution, but the performance with metakaolin replacement was not favourable. The use of sodium citrate reduced the extent of damage in the attack, which was attributed to the effect of retardation caused by sodium citrate.