Performance deterioration of Portland cement matrix due to magnesium sulfate attack

This paper presents a detailed experimental study on the magnesium sulfate attack of cement matrix, and the deterioration mechanism. Experiments were performed on paste and mortar specimens made with ordinary Portland cement conforming to ASTM C 150 Type I. The water-cement ratios were varied from 0.35 to 0.55. In order to identify the reactants by magnesium sulfate at tack. instrumentals analysis such as XRD and SEM were introduced in the present study. Test results showed that the formation of gypum and thaumasite is the main causes of the damage of the cement matrix, but not the formation of ettringite. More importantly, it was found from the laboratory study that the water-cement ratio may play a key role to determine the degree of deterioration of the cement matrix during magnesium sulfate attack. This was confirmed by the results of visual observation, expansion and compressive strength loss of mortar specimens.