Interfacial enhancement of low-carbon cement-epoxy composite grouts using surface-modified nanosilica: A multiscale experimental and molecular simulation study

As demand for high-performance, low-carbon engineering materials increases, this study incorporating surface-modified nanosilica (SMNS) into a waterborne epoxy–calcium sulfoaluminate (CSA) cement grouting materials (WECG). The SMNS was synthesized via KH-560 silane grafting possesses dual-reactive functionality: its inorganic silanol groups chemically bond with CSA hydration products, while the organic epoxy groups crosslink with the polymer network. This dual chemical reactivity enables SMNS to act as a nanoscale interfacial bridge, significantly enhancing compatibility between the inorganic and organic phases resulting in improvements of mechanical properties. Through a multiscale approach combining experiments and molecular dynamics simulations, the study reveals that the Ca–O ionic coordination and chemical anchoring introduced by SMNS substantially improve interfacial bonding strength and ductility. However, agglomeration at higher SMNS concentrations detrimentally affects performance, underscoring the importance of dosage control. This work presents a scalable strategy for designing durable grouting materials with minimal nanomaterial input, contributing to extended service life and reduced environmental impact in sustainable construction. • Study on the mechanical properties and workability of SMNS modified cement-epoxy grout. • The interface enhancement mechanism of SMNS and composite grout was analyzed. • The matrix compactness is enhanced by SMNS through nucleation, micro-filling, and interfacial bridging effects. • Strong Ca–O ionic bonds at the interface were revealed by molecular dynamics, leading to a 31% increase in tensile strength.