Role of graphene oxide as a powerful nano-catalyst in sodium hydroxide-activated slag and its impact on interfacial transition zone

The use of nanocarbon materials to enhance the toughness of fragile cementitious materials has attracted increasing attention for investigation. This study examines the effects of incorporating graphene oxide (GO) into NaOH-activated slag (AAS) pastes and mortars, focusing on workability, phase composition, mechanical properties, and the local mechanical properties of the interfacial transition zone (ITZ) between sand and paste. The experimental results indicate that the addition of GO decreases the flowability of NaOH-AAS pastes, with noticeable aggregation at concentrations above 0.03 wt%. Furthermore, GO enhances the hydration degree of ground granulated blast furnace slag (GGBS), leading to an increased amount of C-A-S-H gel without introducing new phases. In terms of macro performance, incorporating 0.03 wt% GO significantly improves the compressive and flexural strengths of NaOH-AAS mortars by 10.6 % and 17.9 %, respectively. Additionally, the presence of GO reduces the ITZ thickness from 30 to 15 micrometres in NaOH-AAS mortars, which likely contributes to the enhanced mechanical performance.