Abstract This paper discusses the effect of both load-induced cracks and top-casting-induced defects on the corrosion characteristics of the tensile bars in reinforced concrete beams under sustained loading and exposure to a chloride environment. Four reinforced concrete beams exposed to climate accelerated natural corrosion were used in the present work. The cracking maps, chloride profiles and cross-sectional loss of four beams were studied and compared with each other. Experimental results show that the presence of load-induced cracks is not the sole cause of early propagation of corrosion. As a result, top-casting-induced defects are the most significantly impacting factor accelerating the deterioration of reinforced concrete. With top-casting-induced defects, corrosion starts at service cracks and then develops preferentially at the bottom surface of the tensile bar. Without top-casting-induced defects, corrosion starts at service cracks but does not develop along the tensile bar. It is only when the chloride content at the depth of reinforcement reaches a critical value that corrosion develops along the tensile bar – preferentially at the outside surface of the rebar because of its probable higher chloride content.

中文翻译：

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荷载诱导裂纹与顶铸缺陷耦合与否对持续荷载下暴露于氯化物环境的自然腐蚀梁纵向受拉钢筋腐蚀的影响

摘要 本文讨论了在持续加载和暴露于氯化物环境下，荷载引起的裂缝和顶部浇筑引起的缺陷对钢筋混凝土梁中受拉杆腐蚀特性的影响。目前的工作中使用了四根暴露于气候加速自然腐蚀的钢筋混凝土梁。研究并比较了四根梁的开裂图、氯化物分布和横截面损失。实验结果表明，载荷引起的裂纹的存在并不是腐蚀早期传播的唯一原因。因此，顶浇引起的缺陷是加速钢筋混凝土劣化的最显着影响因素。顶铸引起的缺陷，腐蚀开始于使用裂纹，然后优先在拉伸杆的底面发展。如果没有顶部铸造引起的缺陷，腐蚀开始于使用裂纹，但不会沿拉伸杆发展。只有当钢筋深度处的氯化物含量达到临界值时，沿抗拉钢筋才会发生腐蚀 - 优先发生在钢筋的外表面，因为其氯化物含量可能较高。