▎ 摘　　要

This paper aims to study the effect of the size of pristine graphene (PRG) particles on the compressive and tensile strengths of cement-based mortars and to gain better understandings of the mechanism behind the enhancement of these properties. PRG industrially manufactured by the electrochemical process with a variety of particle sizes including 5 mu m, 43 mu m, 56 mu m, and 73 mu m was used at the optimal dosage of 0.07% by weight of cement binder. The results indicate that mechanical strengths of cement mortars at 7 and 28 days considerably depend on the size of PRG. The mixes with size 56 mu m and 73 mu m show significant influence on both compressive and tensile strengths of cement mortars, which increase approximately 34.3% and 30.1% at 28-day compressive strengths, and 26.9% and 38.6% at 28-day tensile strengths, respectively. On the other hand, the mix with size 43 mu m of PRG addition exhibits a significant increase only in tensile strength, and there are no significant effects on either compressive strengths or tensile strengths of the mix containing 5 mu m particles. The observed enhancement in the mechanical properties of cement mortars by large PRG sizes is attributed to the improvement of cement hydration level, the reduction of cement particles' distance in cement gels because of the effect of van der Waals forces between PRG sheets, and the mechanical adhesion forces between PRG sheets and cement gels. The results from this study indicate that PRG is not only a promising additive in practical application for building materials to improve the current drawbacks of cement composites, but also a feasible option to support the reduction of cement mass used in cement composites, which could reduce the CO2 footprint and amount of CO2 emission into the atmosphere. Crown Copyright (C) 2020 Published by Elsevier Ltd. All rights reserved.