持荷下非饱和损伤混凝土材料的气体渗透性研究

In real services concrete materials are always under the combination of mechanical load and environmental actions, and micro-cracks unavoidably exist. The gas permeability of unsaturated damaged concrete under load is of significant importance for durability design, quantitative estimation and prediction of service life for concrete structure. In this proposal experimental simulation will be employed to understand the evolvement of cumulated damage under long-term load action, and the relationship between cumulated damage and gas permeability after long-term loading action will be analyzed. Then the influence of carried loading condition on current damage state is focused, and the relationship between loading level and corresponding gas permeability under load will be analyzed. Based on the experimental study on the storage of water and transport permeation process of gas phase in unsaturated damaged concrete materials, the relation between saturation degree and gas permeability will be founded. After that, the mathematical model of gas permeability of unsaturated damaged concrete materials under loading action will be established by summarizing respective study on the influence of cumulated damage, current damage state under load and saturation degree. This research proposal revolves around the alteration of pore and micro-crack structures of concrete materials, and employs fractal theory, effective medium theory and percolation theory to theoretically analyze the relationship between microstructure characteristics and gas permeability. All the research fruit will provide scientific foundation to quantitatively analyze detailed transport process of erosive media in concrete materials under different real service condition and thus the corresponding durability of concrete structure.

混凝土材料总是在一定荷载、环境因素作用下服役，研究持荷下非饱和损伤混凝土材料的气体渗透性对混凝土结构耐久性设计、定量评估与寿命预测具有重要意义。课题通过试验模拟混凝土材料在长期荷载作用下累积损伤的发展来研究累积损伤演化的规律，并分析累积损伤与卸载状态下气体渗透性的关系；研究混凝土材料持荷条件与当前损伤状态的关系，分析持荷条件对气体渗透性的影响；研究水分在损伤混凝土材料孔隙、微裂纹内的平衡存储及其渗透传输过程，建立气体渗透性与饱和度的关系；综合分析累积损伤、当前损伤状态及饱和度对气体渗透性的影响，最终建立持荷下非饱和损伤混凝土材料气体渗透率的数学模型。课题研究紧紧围绕混凝土材料的孔隙、裂纹微结构展开，基于分形理论、有效介质理论及逾渗理论以从理论上研究孔隙、裂纹微结构与气体渗透性的关系，为定量分析实际混凝土材料的耐久性提供科学依据，并为研究不同服役环境下侵蚀介质的具体传输过程打下基础。

混凝土材料总是在一定荷载、环境因素作用下服役，研究持荷下非饱和损伤混凝土材料的气体渗透性对混凝土结构耐久性设计、定量评估与寿命预测具有重要意义。课题通过试验模拟混凝土材料在长期荷载作用下累积损伤的发展来研究累积损伤演化的规律，并分析累积损伤与卸载状态下气体渗透性的关系；研究混凝土材料持荷条件与当前损伤状态的关系，分析持荷条件对气体渗透性的影响。基于非饱和渗透理论，通过分析表面毛细吸水过程中的水分传输过程，项目建立了表面毛细吸水率与水分扩散率之间的理论关系模型；通过研究水分在损伤混凝土材料孔隙、微裂纹内的平衡存储，项目提出一个适用于水泥基材料的全新水分特征曲线模型，基于该模型可以进一步建立水分扩散率与水分渗透率之间的理论关系，结合水分渗透率与气体渗透率之间的关系，进而可建立相对气体渗透率的理论模型。试验研究表明，理论研究提出的描述表面毛细吸水率、水分扩散率、水分渗透率和相对气体渗透率的统一模型对水泥基材料具有良好的适用性。课题紧紧围绕混凝土材料的孔隙、裂纹微结构展开理论与试验研究，主要基于非饱和流动理论来从理论上研究孔隙、裂纹微结构与水分、气体渗透率的关系，为定量研究实际服役混凝土材料的耐久性提供科学依据，并为研究不同服役环境下侵蚀介质的具体传输过程打下基础。