Structural ordering, mechanical performance and reinforcement mechanism of polyvinyl alcohol-regulated calcium silicate hydrate

Calcium silicate hydrate (C-S-H) determines the mechanical properties of cementitious materials. Disordered microstructure and random pores of C-S-H significantly limit its performance. Herein, C-S-H/polyvinyl alcohol (PVA) composites were fabricated to regulate the assembly of C-S-H nanosheets into nacre-inspired lamellar architectures. This strategy produces an ordered structure accompanied by enhanced silicate polymerization and substantial pore refinement, as demonstrated by comprehensive microstructural characterizations. Interfacial analyses suggested that PVA participated in the connection of adjacent C-S-H through Ca O coordination and hydrogen bonding. Nanomechanical measurements revealed the significantly enhanced elastic modulus of C-S-H, reaching 50.55 GPa, approximately 5.9 times that of CSH-ref. Molecular dynamics simulations indicated that the ordered structure with different C-S-H/PVA thickness ratios improved mechanical properties by promoting polymer-chain stretching, C-S-H pull-out, stress redistribution and energy absorption. These findings provide a multiscale foundation for linking PVA-mediated regulation and directional-induced lamellar assembly with mechanical behavior, offering guidance for the design of high-performance cementitious materials.