Study on the mechanism of polyvinyl alcohol (PVA) polymerization degree on the rheological regulation of cement-based materials: A multi-scale simulation analysis based on adsorption

As a common concrete thickener, Polyvinyl alcohol (PVA) affects cement paste rheology depending on its degree of polymerization (DP). This study examines the influence of PVA DP on rheology using TOC, zeta potential tests, and molecular dynamics. We investigate the mechanism linking DP to thickening performance at microscopic and molecular levels. Results indicate that DP controls PVA adsorption and film formation on cement surfaces, altering the electric double-layer thickness and Zeta potential. This promotes flocculation and enhances interfacial adhesion. Additionally, PVA displays distinct thickening effects under varying hydration times and shear rates. DP regulates the competition between lubrication and steric hindrance, resulting in superior thickening for higher-DP PVA. Molecular dynamics confirm that PVA binds to C-S-H via Ca-O linkages, with free ends forming hydrogen bonds with interlayer water to dissipate shear energy. Higher DP leads to more stable bonding, increasing peak shear stress by 125%. This work provides comprehensive insights into improving rheological properties by adjusting DP through extensive microscopic analysis.