Long-term salt freeze-thaw resistance of polyvinyl alcohol (PVA) modified mortar: The role of molecular structure
Qian Deng, Xuzhe Zhang, Shaohua Li, Qingliang Yu
Abstract
: Polyvinyl alcohol (PVA) has shown potential in developing cost-effective anti-freezing technologies for concrete. However, its effectiveness in reducing scaling and performance stability under combined salt freeze-thaw conditions and the involved mechanism remains unclear. This investigation systematically evaluates the salt freeze-thaw resistance of cementitious systems modified with PVA variants possessing different hydrolysis degrees (DH) and molecular weights (Mw). Experimental results demonstrate that while PVA adsorption on C 3 S/C 3 A surfaces inhibits cement hydration and degrades mechanical properties and pore structure, these effects appear very limited at ≤0.04% low dosages. Fully hydrolyzed PVA with an Mw of 75000 g/mol achieves an 18.8% reduction in mass loss compared to the unmodified group and maintains a stable microstructure after 25 freeze-thaw cycles. The enhancement is primarily attributed to improved ice nucleation inhibition capacity, which positively correlates with increasing DH and Mw. However, cryogenic gelation of PVA compromises its ice inhibition effectiveness, especially PVA with lower DH and Mw showing exacerbated performance degradation due to short-chain aggregation and acetate group steric effects. High-Mw PVA maintains its functionality through 3D network formation that preserves ice-binding sites. These findings provide crucial theoretical foundations for optimizing PVA-modified concrete formulations in cold-region engineering applications.