Research on the toughening mechanism of modified nano-silica and silane molecular cages in the multi-scale microfracture of cement-epoxy composite

Abstract The inherent brittle fracture characteristics of cement limit the application of cement-based materials in fields such as building repair, thin-layer coating, and the preparation of deformable components. The blending of polymers alleviates this characteristic to a certain extent, but the flexibility and toughness still need to be further improved. We prepared a multi-scale toughener (MST) by applying a hydrothermal method to improve the dispersion performance of the nano-silica (NS) aqueous while constructing the multi-component silane molecular cages (SMC) by using 3-glycidyloxypropyl trimethoxysilane (GPTMS). The mechanical properties and micromorphology of the waterborne epoxy-cement repair material (WECM) with MST were characterized. The zeta potential analysis, laser particle size analysis (LPSA), gas chromatography-mass spectrometry (GCMS), gel permeation chromatography (GPC) and molecular dynamics simulation were used to characterize and explain the basic questions that persist in the theory of particle dispersibility and hydrolysis-condensation effects within the MST system. The results show that the hydrothermal treatment is more efficient than mechanical dispersion in dispersing performance while surging the GPTMS’ reaction rate by ~1000 times as well as the transformation from monomers to the caged multimers. The ductility of MST modified WECM radically increased by 300%–400%. The microscopic morphology reveals that the MST effectively induced multi-slit cracking (cracks of ~5 μm in length and ~1 μm in width, the aspect ratio of 6: 1 ~ 4: 1) effects with a noticeable rugged morphology observed. The obtained results include parameters to improve the mechanical properties of composites with MST and this simple and effective organic-inorganic nano toughener has a good application prospect in the field of polymer modified cement-based materials.