Angst Ueli M, Boschmann Carolina, Wagner Matthias, Elsener Bernhard
Institute for Building Materials, ETH Zurich;
Institute for Building Materials, ETH Zurich.
J Vis Exp. 2017 Aug 31(126):56229. doi: 10.3791/56229.
The aging of reinforced concrete infrastructure in developed countries imposes an urgent need for methods to reliably assess the condition of these structures. Corrosion of the embedded reinforcing steel is the most frequent cause for degradation. While it is well known that the ability of a structure to withstand corrosion depends strongly on factors such as the materials used or the age, it is common practice to rely on threshold values stipulated in standards or textbooks. These threshold values for corrosion initiation (Ccrit) are independent of the actual properties of a certain structure, which clearly limits the accuracy of condition assessments and service life predictions. The practice of using tabulated values can be traced to the lack of reliable methods to determine Ccrit on-site and in the laboratory. Here, an experimental protocol to determine Ccrit for individual engineering structures or structural members is presented. A number of reinforced concrete samples are taken from structures and laboratory corrosion testing is performed. The main advantage of this method is that it ensures real conditions concerning parameters that are well known to greatly influence Ccrit, such as the steel-concrete interface, which cannot be representatively mimicked in laboratory-produced samples. At the same time, the accelerated corrosion test in the laboratory permits the reliable determination of Ccrit prior to corrosion initiation on the tested structure; this is a major advantage over all common condition assessment methods that only permit estimating the conditions for corrosion after initiation, i.e., when the structure is already damaged. The protocol yields the statistical distribution of Ccrit for the tested structure. This serves as a basis for probabilistic prediction models for the remaining time to corrosion, which is needed for maintenance planning. This method can potentially be used in material testing of civil infrastructures, similar to established methods used for mechanical testing.
发达国家钢筋混凝土基础设施的老化，迫切需要可靠评估这些结构状况的方法。埋入式钢筋的腐蚀是结构退化最常见的原因。虽然众所周知，结构抵抗腐蚀的能力在很大程度上取决于所用材料或结构使用年限等因素，但目前的普遍做法是依赖标准或教科书中规定的阈值。这些腐蚀起始阈值（Ccrit）与特定结构的实际特性无关，这显然限制了状况评估和使用寿命预测的准确性。使用表格化数值的做法可追溯到缺乏在现场和实验室确定Ccrit的可靠方法。本文介绍了一种确定单个工程结构或结构构件Ccrit的实验方案。从结构中获取多个钢筋混凝土样本，并进行实验室腐蚀测试。该方法的主要优点是，它确保了与那些众所周知会极大影响Ccrit的参数相关的实际条件，比如钢 - 混凝土界面，这在实验室制作的样本中无法得到具有代表性的模拟。同时，实验室中的加速腐蚀试验能够在测试结构发生腐蚀起始之前可靠地确定Ccrit；这相对于所有常见的状况评估方法具有很大优势，那些方法只能估计腐蚀起始后的状况，即结构已经受损时的状况。该方案得出测试结构Ccrit的统计分布。这为剩余腐蚀时间的概率预测模型提供了基础，而这是维护规划所必需的。这种方法有可能用于民用基础设施的材料测试，类似于用于机械测试的既定方法。
