Shrinkage mitigation strategies in alkali-activated slag

In this work, three shrinkage mitigation strategies (i.e. high-temperature curing, sulfate-enrichment, and calcium-enrichment) were evaluated and their effectiveness in mitigating shrinkage of alkali-activated slag (AAS) was studied. The results show that the cause of high-magnitude shrinkage in AAS is attributed to the high visco-elastic/visco-plastic compliance of calcium-alumina-silicate-hydrate (C-A-S-H) in AAS. High-temperature curing can considerably reduce the shrinkage of AAS, likely through strengthening and stabilizing C-A-S-H by improving the coalescence or bonding between adjacent C-A-S-H nanoparticles. However, mitigating shrinkage through early-age expansive reactions is less effective, since the dominant component of drying shrinkage in AAS is due to the long-term visco-elastic/visco-plastic deformation of C-A-S-H.