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工作。这对于保持社会流动性，保障房地产投资组合的安全具有重要意义。含氯环境对钢筋混凝土的影响起着重要的作用，因为修复这些损伤会造成相当大的经济损失。由于氯离子进入钢筋混凝土，钢筋可能失去其被动性，导致点蚀。钢筋横截面的显著损失会导致承载能力和使用性能的下降。在传统的修复方法中，含氯混凝土通常必须移除并重新压型。如果能够正确地应用W-Cl修复概念，则与传统修复方法相比，修复受氯污染的结构将更具成本效益。维修原则W-CL包含在混凝土表面(例如停车场甲板或地下停车场底板)上应用涂层，以防止氯化物和水的进一步渗透，但它允许相反的结构干燥。通过混凝土的干燥，腐蚀过程显著减速，因此进一步的损伤可以转移到非临界区，甚至可以完全停止。目前还没有研究用于低风险实践应用的边界条件，在这种应用中，腐蚀活性可以在临界速度下降低。为保证其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确定混凝土的吸附等温线。进一步的重点是关于混凝土在表面保护涂层下的干燥行为以及相应的氯在部分水饱和混凝土中的重新分布的测试。此外，为了确定取决于氯离子含量的腐蚀速率的非临界含水率，必须根据混凝土的含水率来确定腐蚀率。本研究项目的挑战在于必须在混凝土中加入已知且稳定的氯化物，并且难以正确地掌握部分饱和混凝土中的氯离子重排。在这些研究的同时，还对含氯离子的部分水饱和混凝土中钢筋的腐蚀活性进行了电化学测定。所得结果作为输入参数，用于后续基于W-CL原理的实际维护和维修工作中随时间变化的腐蚀活动的数值模拟。

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.