Autogenous shrinkage of alkali-activated slag: A critical review

This paper provides a critical review on autogenous shrinkage of alkali-activated slag (AAS). It is reported that AAS paste, mortar, and concrete generally show larger autogenous shrinkage than Portland cement (PC) counterparts. Self-desiccation is the main driving force of the autogenous shrinkage of hardened AAS, but other mechanisms also play roles, particularly at early age. Existing models developed for PC do not give satisfactory estimations of the autogenous shrinkage of AAS, unless the pronounced viscoelasticity of AAS is considered. The susceptibility of AAS concrete to extensive cracking is not necessarily high due to the effects of stress relaxation, but local creep can exacerbate the development of microcracks. Various strategies have been proposed to mitigate the autogenous shrinkage of AAS, but many exhibit side effects, e.g., strength reduction. Existing testing methods for autogenous shrinkage of PC seem applicable to AAS, but the starting time and test duration need to be reconsidered.