Comparative Mechanisms of Graphene Nanoplatelets and Graphene Oxide in Regulating Pore Structure and Drying Shrinkage of Cement Mortar

Abstract

This study comparatively investigates the reinforcement mechanisms of graphene nanoplatelets (GNPs) and graphene oxide (GO) in cement mortar at dosages of 0–0.1%, focusing on mechanical properties, drying shrinkage, fluidity, water absorption, and microstructural evolution characterized by SEM, XRD, and MIP. Both nanomaterials reduce fluidity, with GO exhibiting a less pronounced effect. The mechanical properties display unimodal dosage-dependent trends, with optimal flexural strength at 0.05% and optimal compressive strength at 0.03%; the corresponding 28 d enhancements reach 16.9% and 20.8% for GO, compared with 8.2% and 8.5% for GNP. Water absorption and drying shrinkage attain minima at 0.03% and 0.05%, respectively. GO consistently outperforms GNP, which is attributed to its superior pore refinement, reducing total porosity by 15.0% and large pores (>100 nm) by 51.3%, owing to its functional groups that promote dispersion and hydration nucleation. These results establish GO as a more effective nano-reinforcement for pore-structure engineering in cementitious composites.