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

• Applicants: Professor Dr.-Ing. Wolfgang Breit; Professor Dr. Christoph Dauberschmidt
• Subject Area: Construction Material Sciences, Chemistry, Building Physics ; Structural Engineering, Building Informatics and Construction Operation
• Term: from 2014 to 2019
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 264141860

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.

• DFG Programme: Research Grants
• International Connection: Brazil
• Partner Organisation: Fundação de Amparo à Pesquisa do Estado de Minas Gerais