Drying shrinkage of expansive cements

Drying shrinkage behaviour of expansive cement pastes were studied and compared with those of portland cements. Results indicate that the shrinkage behaviour of these two cements is significantly different from each other. Generally, expansive cements shrink more than portland cements, and especially more so if they have not been adequately cured, i.e. curing period of at least 7 days is necessary to ensure good performance against shrinkage. Internal damage caused by large amounts of expansion leads to a large magnitude of shrinkage. In that event curing does not seem to have any beneficial impact on shrinkage performance. Steel reinforcement also seems to decrease shrinkage magnitude, but it has no effect on the shrinkage characteristic. Much of the research on expansive cements has so far been focused on the expansion behaviour rather than on the shrinkage behaviour. More research on shrinkage is needed to improve its field performance.