Atomistic insights into the superior interfacial mechanics of basalt fiber–reinforced cementitious nanocomposite

The interfacial performance of fiber-reinforced cementitious composites is a key determinant of their mechanical properties, yet the interfacial interaction mechanisms between fibers and calcium-silicate-hydrate (C-S-H) matrix still require in-depth investigation at the atomic scale. In this atomistic simulation study, it is demonstrated that basalt fiber (BF) significantly outperforms glass fiber (GF) in enhancing the interfacial mechanical properties of fiber/C-S-H nanocomposite system. The novelties of this study are (i) identifying Fe- and Mg-driven interfacial bonding mechanisms as the origin of BF's superior reinforcement ability and (ii) quantitatively demonstrating BF's mechanical advantages over GF under both tension and shear. Compared to GF, BF forms an enriched and densely packed interfacial transition zone (ITZ) containing unique Fe and Mg in addition to Si, Al, and Ca, which facilitates a broader and stronger bonding network with C-S-H matrix. As a result, the interfacial binding energy of BF/C-S-H system is 22% higher than that of GF/C-S-H. Under uniaxial tension, BF/C-S-H exhibits superior mechanical performance compared to GF/C-S-H, including 16% improvement in tensile strength, 82% increase in failure displacement, and 64% enhancement in fracture toughness. Besides, the higher stress transfer efficiency across the BF/C-S-H interface results in fracture occurring near the interface, whereas fracture in GF/C-S-H occurs within the C-S-H phase. Despite the slightly lower shear strength, the fracture toughness and failure displacement of BF/C-S-H are 26% and 38% greater than those of GF/C-S-H under simple shear. The enhanced shear-induced atomic mobility due to the inclusion of Fe and Mg in BF facilitates the atomic rearrangement, which leads to greater energy dissipation during the shear deformation of BF/C-S-H, thereby effectively delaying the shear fracture. These findings provide atomic-scale insights into the superior mechanical reinforcement capability of BF and offer valuable guidance for designing mechanically robust fiber-reinforced cementitious composites. © 2025 The American Ceramic Society.