A comparative study on shrinkage characteristics of graphene oxide (GO) and graphene nanoplatelets (GNPs) modified alkali-activated slag cement composites

Use of graphene oxide (GO) and graphene nanoplatelets (GNPs) has shown some promising potential to boost the performance of Portland cement (PC). Their influence and working mechanisms in other binding systems, e.g. alkali-activated slag (AAS), are still unclear, although some encouraging results have been reported. This study aims at characterising and quantifying roles of GO and GNPs on shrinkage of AAS mortars. A comprehensive experimental programme was carried out to assess the drying shrinkage and autogenous shrinkage of GO/GNPs-added AAS cements along with hydration process and microstructural changes in order to explain the reasons. The results indicate that the shrinkage of AAS is further increased by GO/GNPs due to refined microstructure and higher degree of hydration of GGBS. That is, the main drawback of AAS, high shrinkage, cannot be mitigated by using these two nano materials. Against these backgrounds, it is early to recommend to directly use GO or GNPs in AAS mixes.