Accelerated impressed current testing is the most common experimental method for assessing the susceptibility to corrosion-induced cracking, the most prominent challenge to the durability of reinforced concrete structures. Although it is well known that accelerated impressed current tests lead to slower propagation of cracks (with respect to corrosion penetration) than in natural conditions, which results in overestimations of the delamination/spalling time, the origins of this phenomenon have puzzled researchers for more than a quarter of a century. In view of recent experimental findings, it is postulated that the phenomenon can be attributed to the variability of rust composition and density, specifically to the variable ratio of the mass fractions of iron oxide and iron hydroxide-oxide, which is affected by the magnitude of the applied corrosion current density. Based on this hypothesis, a corrosion-induced cracking model for virtual impressed-current testing is presented. The simulation results obtained with the proposed model are validated against experimental data, showing good agreement. Importantly, the model can predict corrosion-induced cracking under natural conditions and thus allows for the calculation of a newly proposed crack width slope correction factor, which extrapolates the surface crack width measured during accelerated impressed current tests to corrosion in natural conditions.

翻译：加速外加电流测试是评估腐蚀开裂敏感性的最常用实验方法，腐蚀开裂是钢筋混凝土结构耐久性面临的最主要挑战。尽管众所周知，加速外加电流测试导致的裂纹扩展速度（相对于腐蚀渗透而言）比自然条件下更慢，从而导致对剥落/剥蚀时间的过高估计，但这一现象的根源已困扰研究人员超过四分之一个世纪。根据最近的实验发现，本文推测该现象可归因于锈层成分和密度的可变性，具体而言是氧化铁与氢氧化铁-氧化铁质量分数比值的变化，该比值受外加腐蚀电流密度大小的影响。基于此假设，本文提出了用于虚拟外加电流测试的腐蚀开裂模型。所提模型的仿真结果与实验数据进行了验证，显示出良好的一致性。重要的是，该模型能够预测自然条件下的腐蚀开裂行为，从而可计算新提出的裂纹宽度斜率修正因子，该因子可将加速外加电流测试中测量的表面裂纹宽度外推至自然腐蚀条件下的情况。