水泥基材料水、气和氯离子非饱和传输性能统一模型研究

The durability of concrete structure is mostly determined by the coupled transport process of various deleterious agents. Moreover, most concrete material under real service is partially saturated. Considering the importance of coupled mass transport and partial saturation, this proposal tries to establish the unified determination method of transport properties for water, gas and chloride ion in unsaturated cement-based material. Treating the unsaturated cement-based material as a porous medium containing liquid and gas in its pore space, the liquid water storage, the dilution effect as well as tortuosity effect of unsaturated cement-based material are firstly quantified from the viewpoint of mass transport properties. Based on the basic knowledge about the mechanisms of water, gas and chloride ion transport in porous medium, unified and consistent models with several parameters of clear physical meaning are theoretically established for various deleterious agents. Several typical experiments with coupled mass transport of liquid, gas and chloride ion are further carried out. The complex mass transport process is numerically modeled by employing the newly established unified models for unsaturated mass transport properties. By comparing the measured mass transport process and corresponding predicted results, the unified models for mass transport properties in unsaturated cement-based material are further verified and validated. All the achievement in this research will provide scientific foundation to quantitatively analyze the detailed transport process of erosive medium in unsaturated concrete materials under different service condition and thus the corresponding durability performance of concrete structure.

混凝土结构的耐久性能往往由侵蚀介质的传输过程决定。考虑到非饱和状态和多相耦合传输的普遍性与重要性，课题致力于研究建立由具有明确物理意义的一致参数表达的水、气及氯离子非饱和传输性能统一模型。将非饱和水泥基材料视作内含气、液两相流体的多孔介质，基于对非饱和多孔介质影响物质传输的稀释效应、曲折度效应及水分存储状态的量化描述，从水、气及氯离子在孔隙内的传输机理出发，从理论上建立包含统一参数的各相物质传输性能模型，并实测典型砂浆材料的各种非饱和传输性能来直接验证。同时，课题通过开展气液耦合、液体与离子耦合、液体气体离子高度耦合的系列经典物质传输试验，利用建立的统一非饱和物质传输性能模型来定量地分析、描述耦合物质传输过程，并将理论分析结果与实测结果进行对比验证。项目研究成果将为定量研究复杂环境边界条件下的侵蚀介质传输过程奠定理论基础，进而为实际混凝土结构的耐久性定量设计、评估及寿命预测等提供科学依据。

混凝土结构的耐久性问题是当前土木工程领域亟需解决的重大课题。混凝土结构的耐久性主要由环境中的水、气和离子向材料内部迁移的速率和过程决定。考虑到非饱和状态和多相耦合传输的普遍性，课题针对水泥基材料内部水、气和氯离子的非饱和传输过程进行研究。..课题通过量化水泥基材料孔结构对侵蚀介质传输的稀释效应和曲折度效应影响，明确饱和传输性能与孔结构的关系，进而考虑饱和度影响建立起各相侵蚀介质非饱和传输性能的统一数学模型。为验证该模型，项目创新应用低场磁共振测试技术来表征典型砂浆在饱水状态下的孔结构和非饱和状态下的水分分布，发现孔径分布曲线及特征孔径在孔隙流体不同（水、异丙醇、真空）时存在数量级差异，发现吸湿过程伴随着水化硅酸钙凝胶层间孔的显著吸水膨胀，发现饱水状态下的孔结构与水分渗透率的关系可以采用经典模型进行准确描述，据此在国际上首次提出水泥基材料具有显著水敏性的概念。受水敏性影响，水泥基材料的毛细吸水速率与初始饱和度呈双线性关系，初始干燥水泥基材料的毛细吸水过程表现出两阶段线性吸水规律且第二阶段毛细吸水速率的物理意义更加明确。近似考虑水敏性后，应用非饱和传输性能统一数学模型，可准确描述水泥基材料长期毛细吸水过程。当吸收含离子的水溶液时，水泥基材料吸湿膨胀的动力学过程会受到离子的影响，离子浓度越高则凝胶膨胀过程发展得更快更强，孔结构细化的速度和程度也越高，可将之视作离子敏感性。..项目建立的非饱和传输性能统一数学模型可用于定量分析评价实际服役混凝土结构的耐久性；建立的低场磁共振测试技术为孔结构的原位、快速、无损测试提供技术支持；国际上首次提出的水敏性概念为混凝土抗裂性和耐久性理论研究与技术开发指明方向；对两阶段毛细吸水速率物理意义的深入挖掘，为水泥基材料耐久性能的快速表征提供理论与方法支撑。..课题研究成果在水泥基材料研究方法学和关键科学问题的解决方面取得重要突破，促进水泥基材料研究方式的转变。