Effects of graphene oxide on microstructure and mechanical properties of graphene oxide-geopolymer composites

This work aims to examine the impact of graphene oxide (GO) and reduced graphene oxide (rGO) on mechanical properties and microstructure of fly ash (FA) based geopolymer. Different schemes were proposed to prepare GO/rGO-geopolymer composites. The chemical composition, microstructure and hydration degree of GO/rGO modified geopolymer were characterized by using FTIR, XRD, DTG, SEM, XPS and BET. The experimental results show that GO/rGO changes the microstructural composition and pore diameter distribution of geopolymer. The increased average electron binding energy of the tetrahedron of [AlSiO4] or [AlSi3O8] leads to the acceleration of geopolymerization process. The decreased average pore volume and porosity confirms that GO/rGO accelerates the dissolution and hydration process of FA microspheres. GO and rGO exhibit different efficiency in promoting the hydration degree of geopolymer, which may be due to different functional groups and dispersion efficiency. Meanwhile, the flexural strength changes with addition of GO/rGO, which increases by 25% for the use of 0.30 wt% GO and 10% for the use of 0.10 wt% rGO. In general, GO and rGO are promising to promote the hydration of FA and increase the mechanical strength of geopolymer. (C) 2020 Elsevier Ltd. All rights reserved.