Chloride penetration resistance of concrete is one of the key parameters for the durability design of reinforced concrete structures located in chloride-bearing environments. In all the current available durability models, service life is evaluated considering concrete in uncracked conditions, which is rarely found in practice. This work investigates chloride penetration resistance of concrete in uncracked and micro-cracked configurations, evaluated in terms of chloride migration coefficient through non-steady state migration test (Rapid Chloride Migration test). Prismatic specimens were manufactured considering six different concrete types and two different times of curing. In micro-cracked configuration, cracks were obtained with a specifically developed loading procedure. Micro-cracks were characterized at the end of the exposure test, in terms of crack width at the exposed surface and crack depth. Results showed that cracks were 5–70 μm wide and up to 40 mm deep, always causing an increase in chloride penetration, that should be evaluated considering both crack width and crack depth, with respect to sound conditions. The effects on the chloride penetration seemed to be more pronounced on the more impervious concretes.

中文翻译：

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荷载致微裂纹对不同类型混凝土抗氯离子渗透性能的影响

混凝土的抗氯化物渗透性是位于含氯化物环境中钢筋混凝土结构耐久性设计的关键参数之一。在当前所有可用的耐久性模型中，评估使用寿命时都考虑了未开裂条件下的混凝土，这在实践中很少见。这项工作研究了混凝土在未开裂和微开裂配置中的氯离子渗透阻力，通过非稳态迁移测试（快速氯离子迁移测试）评估了氯离子迁移系数。考虑到六种不同的混凝土类型和两种不同的固化时间，制造了棱柱形试样。在微裂纹配置中，裂纹是通过专门开发的加载程序获得的。在暴露测试结束时表征微裂纹，在暴露表面的裂纹宽度和裂纹深度方面。结果表明，裂纹宽度为 5-70 微米，深度可达 40 毫米，总是会导致氯化物渗透率的增加，应考虑裂纹宽度和裂纹深度，就健全条件进行评估。对氯化物渗透的影响似乎在更不透水的混凝土上更为明显。