钢筋非均匀锈蚀引发的混凝土保护层开裂细观数值研究

Meso-scale numerical investigation on the crack process of concrete cover induced by rebar non-uniform corrosion

混凝土保护层锈裂严重影响钢筋混凝土结构的耐久性。为了研究混凝土保护层的锈裂行为,考虑到混凝土细观结构的非均质性以及钢筋锈蚀的非均匀性,将完好混凝土视为由骨料、砂浆和界面过渡区组成的三相复合材料,建立了细观随机骨料模型。在模型中,钢筋的非均匀锈蚀行为以施加非均匀径向位移的方式模拟,骨料的力学行为假定为弹性,砂浆和界面过渡区的力学特性采用塑性损伤模型来描述。在此基础上进行了中部钢筋非均匀锈蚀引发的混凝土保护层开裂行为的细观数值模拟;分析结果与已有文献中的试验结果吻合良好。另外,对比了均质模型和非均质模型中钢筋均匀锈蚀和非均匀锈蚀导致的保护层开裂模式;并探讨分析了保护层厚度和钢筋直径对保护层开裂模式、钢筋锈胀压力及保护层开裂时钢筋锈蚀率的影响。

Concrete cover cracking induced by corrosion of steel reinforcement is a major influencing factor for durability and serviceability of reinforced concrete structures. In order to investigate the cracking process of concrete cover induced by rebar corrosion, the heterogeneity of concrete meso-structure and non- uniformity of rebar corrosion are accounted for. The undamaged concrete is assumed to be a three-phase composite material composed of aggregate, mortar matrix and the interfacial transition zone （ITZ）. And a concrete random aggregate structure is established for the study on the mechanical behavior of the non- uniform radial corrosion expansion. In the present simulations, non uniform radial displacement is adopted to simulate the non-uniform corrosion of the rebar; the plasticity damaged model is used to describe the mechanical behavior of the mortar matrix and the ITZ, and the aggregate is assumed to be elastic. Thecracking of concrete cover due to the non-uniform corrosion of the middle located rebar is numerically simulated. The comparison of the analysis and the test result on failure pattern of cover concrete shows fairly good agreement. And then the failure patterns under uniform corrosion and non-uniform corrosion obtained from the macro-scale homogeneous model and the meso scale heterogeneous model are compared. Furthermore, the influences of concrete cover thickness and rebar diameter on the failure pattern of concrete cover, the expansive pressure and the corrosion rate of the rebar when cover concrete cracks are investigated.