▎ 摘　　要

This paper presents a new method of improving mechanical and physical properties of a composite cementitious material, by a one-step combined modification using graphene and polyvinyl alcohol (PVA) to overcome limitations of other modification methods by polymer and nanomaterials. The complementary and combined effect of graphene and PVA can solve key problems such as high cost, low production of graphene and poor dispersion of graphene in the cementitious matrix. The proposed method of graphene/PVA aqueous dispersions by shear exfoliation has high stability and can directly replace water in cement casting. The exfoliation and dispersion mechanisms of graphene by PVA aqueous solution are revealed by molecular dynamics simulation. Compared to plain cement, the graphene/PVA modified cementitious material has up to 71.1% higher compressive strength, 106.5% higher flexural strength and 75.8% increase in thermal conductivity, whilst PVA-modified cement has only 0.8% increase in compressive strength and 36.2% increment in flexural strength. (c) 2020 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http:// creativecommons.org/licenses/by/4.0/).