Research progress on two-dimensional carbon nanomaterials modified alkali-activated cementitious materials: A review

Graphene is a two-dimensional nanomaterial made of carbon atoms tightly packed with sp2 hybridized connections, which has excellent electrical and mechanical properties. Even though graphene is hydrophobic and very easy to agglomerate, nowadays it is a hot spot at the forefront of research on alkali-activated cementitious materials, as it can play a role in increasing strength, improving performance, and increasing functionality by exerting the physical effects of gap-filling, nucleation sites, and interlocking effects in alkali-activated cementitious materials doped with graphene. Therefore, the use of graphene and its derivatives, i.e., graphene oxide (GO), partially reduced graphene oxide (rGO), and graphene nanoparticles (GNPs) to modify alkali excitation cementitious materials is the mainstream currently. In this paper, the preparation and dispersion of different graphene derivatives are reviewed in terms of mechanism and other aspects, with emphasis on their different effects on the hydration process and microstructure of alkali-activated cementitious materials, which in turn, modulate the workability, mechanical properties, durability, heavy metal curability and functionality of alkali-activated cementitious materials. In addition, the paper discusses the problems faced by future research in this field, such as the conflicting working, mechanical and electrical conductivity properties, the complexity of the liquid-phase environment and the difficulty of investigating the regulatory mechanism, etc., and looks forward to the future direction of graphene-modified alkali-activated cementitious materials.