Elastic and Electronic Properties of Alkali Charge-Balanced Calcium Aluminosilicate Hydrate Nanocomposites: A First-Principles Study

High Resolution Image Download MS PowerPoint Slide Graphene–based nanomaterials are regarded as outstanding candidates for enhancing cementitious nanocomposites owing to their superior elastic properties. Using a density functional theory (DFT) simulation approach, this study provides an in–depth analysis of the electronic and elastic behavior of alkali–activated Al–substituted tobermorite 14Å structures, adopted here as representative crystalline analogues based on the experimental structural models proposed in previous studies, forming [C–(Na–)A–S–H] and [C–(K–)A–S–H] gels reinforced with hydroxyl– and epoxy–functionalized reduced graphene oxide (rGO) lattices. The simulations reveal that interfacial bonding and elastic properties are strongly governed by the type of rGO functionalization. Hydroxyl–functionalized rGO nanosheets enhance proton mobility and stabilize the alkali C–A–S–H phase through the formation of strong covalent bonds with AlO 4 tetrahedra, whereas epoxy–functionalized rGO structures mainly rely on weaker hydrogen–bond interactions. In addition, Na–based nanocomposites showed greater enhancements in elastic properties and stronger ionic interactions compared to their K–based counterparts, highlighting the influence of alkali type on structural performance. Thus, the C–Na–A–S–H phase achieves improvements of ∼69% (dry) and 23% (hydrated) in Young’s modulus, and 96% and 26% in bulk modulus. In comparison, the C–K–A–S–H phase shows increases in Young’s modulus of ∼74% and 15%, and in bulk modulus of 85% and 13%, respectively, emphasizing the strong reinforcing effects of rGO functionalization. In summary, both hydroxyl– and epoxy–functionalized rGO act as effective reinforcing agents, significantly improving the structural integrity and mechanical performance of alkali–activated slag (AAS)–derived gels relative to conventional C–S–H–based nanocomposites.