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 C₃S/C₃A 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 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.

中文翻译：

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聚乙烯醇 （PVA） 改性砂浆的长期耐盐冻融性：分子结构的作用

聚乙烯醇 （PVA） 在开发具有成本效益的混凝土防冻技术方面已显示出潜力。然而，它在盐冻融联合条件下减少结垢和性能稳定性的有效性以及所涉及的机制仍不清楚。本研究系统地评估了用具有不同水解度 （DH） 和分子量 （Mw） 的 PVA 变体改性的胶凝体系的耐盐冻融性。实验结果表明，虽然 PVA 吸附在 C₃S/C₃A 表面会抑制水泥水化并降低机械性能和孔隙结构，但在 ≤0.04 % 的低剂量下，这些影响似乎非常有限。与未改性组相比，Mw 为 75000 g/mol 的全水解 PVA 的质量损失减少了 18.8 %，并在 25 次冻融循环后保持稳定的微观结构。这种增强主要归因于冰成核抑制能力的提高，这与 DH 和 Mw 呈正相关。然而，PVA 的低温凝胶化损害了其冰抑制效果，尤其是 DH 和 Mw 较低的 PVA 由于短链聚集和乙酸盐基空间效应而表现出性能恶化。高分子量 PVA 通过保留冰结合位点的 3D 网络形成来保持其功能。这些发现为在寒冷地区工程应用中优化 PVA 改性混凝土配方提供了重要的理论基础。