海洋复合离子腐蚀作用下混凝土的劣化机制及损伤本构模型研究

In the harsh and complex ocean, marine concrete structures are subjected to the coupling corrosion of compound aggressive ions and are in complicated spatial stress state. The study on the deterioration mechanism of concrete subjected to multiple ocean ions and the spatial damage constitutive model of corroded concrete are prerequisite for the durability assessment of concrete structures in the ocean. In the present project, the corrosion experimental study on concrete is performed under combined action of sulfate ion, magnesium ion and chloride ion with the same ion concentration ratio as that in the actual seawater. The ion concentration distribution in concrete, micro-structure, corrosion product and physical parameters are analyzed to investigate the diffusion characteristic of compound ions, deterioration mechanisms of the marine concrete and the effect of ion concentration and chloride ion on the corrosion process. Further, with respect to the corroded concrete with different damage degrees, the tri-axial mechanical and permeability tests are conducted to understand the deterioration mechanism of mechanical properties and permeability. Based on the ion diffusion, chemical reaction and damage mechanical theories, a chemical damage evolution function considering the coupling corrosion of compound sulfate ion, magnesium ion and chloride ion is proposed, and further an elastoplastic mechanical-chemical damage constitutive model is proposed for the corroded marine concrete. The present investigation may provide some scientific references for the life prediction and safety evaluation of corroded concrete structures in the harbor, coastal and offshore engineering, which is both scientific significance and engineering applied importance.

海洋环境复杂、严酷，海工混凝土结构经受多重腐蚀性离子的耦合作用，并处于复杂的空间应力状态，研究混凝土在海洋复合离子腐蚀作用下的劣化机理以及受腐蚀混凝土的空间损伤本构模型，是海工混凝土结构耐久性评估的必要前提。本项目拟参照海水离子浓度的比例，开展硫酸根离子、镁离子和氯离子耦合作用下混凝土的腐蚀试验，通过混凝土内部离子浓度分布、微观结构、腐蚀产物和物理参数分析，研究复合离子的扩散特性和海工混凝土的劣化机制，以及离子浓度和氯离子对腐蚀进程的影响；进行不同腐蚀程度混凝土的三轴加载力学试验和渗透试验，研究受腐蚀混凝土力学性能和抗渗性能的退化特征；基于离子扩散、化学反应和损伤力学理论，建立复合硫酸根离子、镁离子和氯离子耦合作用的化学损伤演化函数，提出受腐蚀海工混凝土的弹塑性力学-化学损伤本构模型。研究成果为港口海岸及近海工程混凝土结构的寿命预测和安全评估提供科学依据，具有重要的科学意义和工程应用价值。

在多重腐蚀性离子和复杂的空间应力状态共同作用下，海工混凝土结构极易出现损伤，因此需要研究混凝土在海洋复合离子腐蚀作用下的劣化机理以及受腐蚀混凝土的空间损伤本构模型。本项目开展了硫酸根离子、镁离子和氯离子耦合作用下混凝土的腐蚀试验。通过膨胀率、质量、表观形貌等物理参数的变化规律，结合微观结构SEM分析，探究了海洋复合离子对混凝土的耦合腐蚀机理。通过测量混凝土内部各离子的浓度分布，分析了海洋复合离子在混凝土中的扩散机理。通过进行不同腐蚀程度混凝土的三轴力学试验和渗透试验，研究了海洋复合离子对混凝土力学和渗透特性的影响。基于离子扩散、化学反应和损伤力学理论，建立了考虑硫酸根离子、镁离子和氯离子耦合作用的化学损伤演化函数，提出了受海水腐蚀混凝土的弹塑性力学-化学损伤本构模型。研究成果可以为港口海岸及近海工程混凝土结构的寿命预测和安全评估提供科学依据，具有重要的科学意义和工程应用价值。