Mitigation of autogenous shrinkage in alkali activated slag mortars by internal curing

Alkali activated slag shows considerable promise as an environmentally friendly alternative to binders produced from ordinary portland cement. The shrinkage behavior of alkali activated slags, however, is not well understood, and is a hurdle to widespread adoption. The use of pre-wetted lightweight aggregate-based internal curing to mitigate shrinkage in slags activated by Na2CO3 solution or waterglass/NaOH solution has been investigated. Chemical shrinkage measurements were used to determine the amount of additional curing water needed by the mixtures, and autogenous and total shrinkage measurements used to determine the effects of internal curing on the overall shrinkage of the systems. Internal curing can completely mitigate autogenous shrinkage; however, in the systems examined here, drying shrinkage was the dominant shrinkage factor. In such a case, the benefits of internal curing are most clearly observed during the first 7 days.