Performance level controlled efficiency of graphene nanoplatelets in cementitious composites

Graphene nanoplatelets (nGP) have been widely reported as effective nano-reinforcements for cementitious composites; however, their optimal dosage remains inconsistent across existing studies. This variability is commonly attributed to nanomaterial-related parameters, whereas the influence of the cementitious matrix’s inherent performance is rarely systematically examined. In this study, cementitious matrices with distinct performance levels were designed by varying water-to-binder ratios (0.55, 0.40, and 0.30) and incorporating silica fume. Their interaction with nGP was experimentally investigated, with contents up to 2.4% being used. A total of 25 mix designs were evaluated for fresh-state behavior, mechanical performance, transport properties, and microstructural characteristics. The results indicate that the efficiency and optimal utilization of nGP are strongly governed by the matrix performance level. High-performance matrices (water-to-binder (w/b) = 0.30, 11% silica fume) achieved peak performance at 1.2% nGP, yielding compressive strength of 118.2 MPa and up to 50% reduction in capillary water transport, whereas low-performance matrices (w/b = 0.55) exhibited limited sensitivity to nGP incorporation. Microstructural observations confirmed that matrix densification improved nGP integration and hierarchical pore refinement by enhancing interfacial bonding, thereby restricting capillary water transport. The findings demonstrate that optimal nGP dosage cannot be treated as an intrinsic material parameter and should instead be defined in relation to matrix performance level, enabling performance-based dosage guidelines for nano-engineered composites in high-durability applications.