Further evidence relating to the ‘new hypothesis of sulphate expansion’

A recently proposed mechanism of sulphate expansion of cements has been subjected to further tests. According to the proposed mechanism, an addition of CaCO₃ to Portland cement should result in a better performance in sulphate solution. To test this, a single batch of Portland cement was used neat and in two 9:1 ‘cement’ mixtures madefrom cement and CaCO₃ and cement and quartz respectively. A series of 1:4 ‘cement’ :sand mortar prisms was made with the neat cement and with each of the two ‘cement’ mixtures. After water curing, these prisms were exposed to sulphate solutions, and their expansion was measured. The results showed that the mixture of CaCO₃ and Portland cement performed better than both the neat Portland cement and the mixture of quartz and Portland cement, thereby corroborating the proposed mechanism of sulphate expansion. The significance of these results for other properties of Portland cement is also discussed.