Fundamental studies on the mechanisms of repair principle W-Cl and to ensure durability

保证钢筋混凝土结构的耐久性是一项技术要求很高的任务。保持房地产投资组合的流动性和安全性对社会具有重要意义。含氯环境对钢筋混凝土的影响起着重要的作用，因为这些损害的修复会造成相当大的经济损失。由于氯化物进入钢筋混凝土，钢筋会失去其钝性，导致点蚀。钢筋截面的显著损失会导致其承载能力和可用性的损害。含氯化物的混凝土通常必须去除，然后在传统的修复方法中重新塑造。如果能正确地应用W-Cl修复概念，那么与传统修复方法相比，氯化物污染结构的修复将更具成本效益。W-Cl修复原理包括在混凝土表面（例如停车场甲板或地下停车场的底板）涂上一层涂层，这可以防止氯离子和水的进一步渗透，但它允许结构的干燥。通过混凝土的干燥，腐蚀过程明显减速，因此进一步的破坏可以转移到非临界区域，甚至可以完全停止。目前还没有研究低风险实际应用的边界条件，即腐蚀活性可以在临界速率下降低。为了保证在实践中的安全应用，必须进行基础研究。其中一点是根据环境湿度和氯化物含量测定混凝土的吸附等温线。进一步的要点是关于混凝土在表面保护涂层下的干燥行为的测试，以及在部分水饱和的混凝土中氯离子的相应重新分布。此外，腐蚀速率必须根据混凝土的含水率来确定，以便确定腐蚀速率的非临界含水率，而腐蚀速率取决于氯化物含量。本研究项目的挑战在于必须将已知和稳定浓度的氯化物插入混凝土中，并且难以正确掌握部分饱和混凝土中的氯化物重排。这些研究伴随着钢筋在含氯化物部分水饱和混凝土中的腐蚀活性的电化学测定。得到的结果被用作输入参数，用于随后的基于W-Cl原理的与实践相关的维护和修理工作的随时间变化的腐蚀活性的数值模拟。

It is a technically demanding task to ensure the durability of reinforced concrete structures. It is of high significance for the society to maintain the mobility and to secure the real estate portfolio. Effects of chloride-containing environments on reinforced concrete play an important role because the repair of these damages causes a considerable economic damage. Due to chloride ingress into reinforced concrete the reinforcement bars can lose their passivity leading to a pitting corrosion. Significant loss of cross section of the rebar can lead to impairment of the load bearing capacity and usability.Chloride-containing concrete usually has to be removed and subsequently re-profiled in conventional repair methods. The repair of chloride-contaminated structures would be much more cost-efficient compared to conventional repair methods if the repair concept W-Cl could be applied unerringly. The repair principle W-Cl contains the application of a coating on concrete surfaces (e. g. a parking deck or a base slab of an underground parking), which prevents the further penetration of chloride and water, but it permits the drying of the structure contrariwise. By the drying of the concrete the corrosion processes are significantly decelerated, so that the further damage can be shifted to an uncritical area or can even completely stopped.The boundary conditions for a low-risk practice application, where the corrosion activity can be reduced under a critical rate, are not studied yet. To ensure the safe application in practice, basic research must be carried out. One point is the determination of the sorption isotherms of the concrete depending on the ambient humidity and the chloride content. Further points are tests about the drying behavior of the concrete taking place under surface protection coatings and the corresponding redistribution of chloride in partially water-saturated concrete. Furthermore corrosion rates have to be determined depending on the moisture content of concrete in order to define an uncritical moisture content for the corrosion rate which depends on the chloride content.The challenge of this research project consists in the necessity to insert chlorides in known and steady concentration into the concrete and the difficulty to be able to grasp correctly the chloride rearrangement in part-saturated concretes. These studies are accompanied by electrochemical determination of the corrosion activity of reinforcing steel in chloride-containing partially water-saturated concrete. The obtained results are used as input parameters for the subsequent numerical simulation of the time dependent corrosion activity for practice-related maintenance and repair work on the principle of W-Cl.