锈蚀钢筋混凝土保护层锈胀开裂时间的预测模型

Modeling of time to corrosion-induced cover cracking in reinforced concrete structures

由钢筋锈蚀引起的混凝土保护层锈胀开裂是混凝土结构耐久性极限状态的重要标志,是决定结构使用寿命的重要因素。以钢筋均匀锈蚀为前提,考虑锈蚀产物的变形特性以及锈胀裂缝开展过程中锈蚀产物进入裂缝的实际情况,借助弹性力学和Faraday腐蚀定律,建立混凝土保护层锈胀开裂时刻的钢筋锈蚀率以及锈胀开裂时间计算公式。针对影响混凝土保护层锈胀开裂时间各主要因素的分析表明,增大钢筋的混凝土保护层厚度、减小钢筋直径、提高混凝土强度以及控制锈蚀产物的体积膨胀率都有利于混凝土结构耐久性的提高。与已有试验结果的对比分析可知,对于加速锈蚀和长期锈蚀情况,计算公式的预测结果均较为理想,可用于由钢筋均匀锈蚀引起的混凝土保护层锈胀开裂时间的预测分析。

Concrete cover cracking induced by reinforcement corrosion is an important indication of durability limit state for reinforced concrete （RC） structures, and can be used to determine the structural service life. Based on the assumption of uniform corrosion of reinforcement, two models for predicting the time from corrosion initiation to cover cracking and its corresponding corrosion ratio of reinforcement were established according to the mechanics of elasticity and Faraday＇ s Law. In the present models, the deformation property of corrosion products and the extent of corrosion products＇ingress into expansive cracks were all taken into account. The main factors affecting the time to corrosioninduced cracking were analyzed. It is found that the increase of cover thickness, decrease of rebar diameter, improvement of concrete strength and reducing volume expansion of corrosion products are in favor of improving the durability of RC structure. The comparison of prediction results with experimental values obtained from accelerated and long-term tests shows that the proposed model is in good agreement with test results and can be applied in practical design.