Preparation of graphene-coated lithium slag and its effect mechanism on cement-based composites

Abstract

Graphene and its derivatives are widely used nanomaterials within high-performance cementitious composites in the construction industry. However, their tendency to agglomerate presents challenges for uniform dispersion, limiting their effectiveness. This study proposes an in-situ modification strategy to synthesize graphene directly onto a carrier, improving its dispersion and ensuring its reinforcing effects. Nitrate lithium slag (NLS), an industrial solid waste obtained through pressurized nitric acid leaching of spodumene, is a highly active supplementary cementitious material that can serve as carrier for in situ graphene synthesis. In this study, a carbothermal reduction method was used to prepare a graphene-coated NLS composite (G@NLS). The results demonstrated that graphene was successfully grown in situ on the surface of NLS, exhibiting excellent dispersion and strong interfacial bonding. Compared to pure cement paste, the incorporation of G@NLS reduced the fluidity and extended the setting time of cement paste. Compared to pure cement blocks, G@NLS enhanced the compressive and flexural strengths of cement blocks by 27.5 % and 33.1 % after 28 d. The graphene in G@NLS acts as a nucleation site, promoting the secondary hydration of NLS, and also contributes to pore-filling.