考虑微结构关键参数的荷载损伤钢筋混凝土腐蚀行为与锈裂机理研究

Corrosion of reinforcement is the main cause of premature structural failure of reinforced concrete (RC) structures, and the pore structure of reinforced concrete affects the corrosion behavior during its entire service life. The methodology that will be implemented in the present project is based on the microstructural parameters of reinforced concrete, with combination of microstructural engineering and metal corrosion electrochemistry. Theoretical analysis, numerical simulation, and experimental study will be used in the research. First of all, the influence of loading effect on key microstructural parameters of concrete and the interfacial transition zone (ITZ) between concrete and reinforcing bar will be deeply investigated. In addition, the mechanisms of concrete damage on mass transport behaviors in the micro environment surrounding the rebar will be studied. Afterwards, the chloride, water and oxygen coupled transport model will be established by taking account of loading and environment coupling effects. It can be used to predict the non-uniform time-to-corrosion initiation in steel reinforced concrete, and reveal the mechanism of corrosion rate as a function of various environmental conditions. Secondly, the mechanism of accelerated corrosion of reinforcing bar, as well as the relationship between accelerated corrosion and natural corrosion, will be studied. Finally, the non-uniform corrosion-induced cracking model for the concrete cover, based on the time-dependent interactive action among corrosion rate, expansive force, and strain field of concrete, will be established. The research results will provide theoretical basis and data support for the prediction of time-to-corrosion initiation, rust cracking time and the deterioration of the structure service performance, and improve the applicability and generality of the service life prediction model.

钢筋腐蚀是引起混凝土结构锈裂失效的主要原因，而钢筋混凝土的多孔结构特征对腐蚀行为的影响贯穿整个结构服役寿命周期。本项目以钢筋混凝土微结构特征参数为基础，融合微结构工程学和金属腐蚀电化学等交叉学科，采用理论分析、数值模拟和试验研究相结合的方法，深入研究荷载作用对混凝土和钢筋-混凝土界面过渡区微结构关键参数的影响规律，阐明混凝土损伤对钢筋周围微环境侵蚀介质传输的影响机理，建立多场耦合作用下混凝土中氯盐-水分-氧气耦合传输模型，预测多场耦合作用下钢筋自然不均匀锈蚀开始时间，明确自然锈蚀条件下钢筋锈蚀速率的影响机制；探明钢筋加速不均匀锈蚀机理，建立钢筋加速锈蚀与自然锈蚀的相似关系；揭示锈蚀率-锈胀力-混凝土应变场交互作用时变规律，建立钢筋不均匀锈蚀下的混凝土锈裂预测模型。为荷载损伤钢筋混凝土结构的钢筋起锈和锈裂时间预测、结构性能劣化研究提供理论基础和数据支持，提高混凝土结构寿命预测方法的通用性。

钢筋腐蚀是引起混凝土结构锈裂失效的主要原因，而钢筋混凝土的多孔结构特征对腐蚀行为的影响贯穿整个结构服役寿命周期。本项目开发了一套硬化后水泥基材料非接触式电阻率测定仪，为水泥基材料连通孔隙测定提出了创新性的解决方案。研究了水泥基材料中氧气、氯盐等介质传输规律，阐明了荷载损伤影响侵蚀介质在混凝土中传输的机理，提出了水泥基材料氯离子扩散系数非接触式测定方法。通过创新设计试验方法，借用“并联”模型，采用理论和试验研究了界面过渡区的氯盐和氧气传输规律，建立相应了相应的理论模型，为钢筋锈蚀预测提供支撑；从混凝土工程实际出发，全面考虑钢筋锈蚀诱发机理和实际环境条件，以荷载和氧气扩散系数为基本参数，以水泥基材料孔隙率作为基本参数之间的桥梁，建立了持续荷载作用下高温高湿环境中钢筋锈蚀速率的时变模型。对施加不同荷载的混凝土梁进行自然环境下的加速锈蚀，阐明了持续荷载作用下混凝土中钢筋锈蚀速率的规律，量化分析了钢筋横截面纵向分布的不均匀性；基于电化学理论，开发了模拟钢筋自然非均匀锈蚀的加速试验方法，进一步建立了钢筋通电加速锈蚀锈层发展模型，探明了钢筋典型通电锈蚀方法的锈层分布规律、锈蚀效率以及影响因素，得出了钢筋非均匀通电加速锈蚀方法的推荐参数；分析了钢筋加速腐蚀与自然腐蚀的相似关系；基于以上介质传输和钢筋非均匀锈蚀技术，系统研究了钢筋非均匀锈蚀条件下针对不同钢筋布置的混凝土锈裂模式，建立了钢筋的起锈和混凝土的锈裂预测模型。相关研究成果可为荷载损伤钢筋混凝土结构的钢筋起锈和混凝土锈裂时间预测、结构性能劣化研究提供理论基础和数据支持。