Study on the mechanism of polymer-whisker synergistic regulation of cement pore structure and toughness

Polymer modification improves cement toughness but can increase porosity through air entrainment. This study develops a synergistic system using vinyl acetate-ethylene copolymer (VAE) redispersible latex powder and calcium carbonate whiskers (WC). Mechanical testing, X-ray diffraction (XRD), scanning electron microscopy (SEM), mercury intrusion porosimetry (MIP), isothermal calorimetry, and molecular dynamics simulations were conducted. With 5 wt.% VAE and 3 wt.% WC, the flexural-to-compressive strength ratio increased by 439.44% compared with plain cement, while compressive strength decreased by 27.96%. VAE formed a flexible film that enhanced crack bridging and energy dissipation but inhibited hydration. WC acted as a micron-scale filler and heterogeneous nucleation site, refined pores, and promoted C-S-H growth. Molecular dynamics showed stable coordination between VAE carbonyl oxygen and Ca sites on C-S-H, restricting interfacial water migration. The results clarify the organic–inorganic synergistic modification mechanism for low-carbon cementitious materials.