Hydrophobierung des Betons - Ökologische und ökonomische Aspekte / Water Repellent Treatment of Concrete - ecological and economical aspects

The use ofdeicing salts on roads may lead to chloride ion induced corrosion. This deterioration mechanism has become one of the most frequent reasons for repair measures within the planned service-life of concrete structures. One way of reducing the risk of chloride ion induced corrosion is the prevention of the penetration of dissolved chloride into the concrete. By water repellent surface treatment the water and chlorid penetration rate can be substantially slowed down. As the water repellent treatment has a limited service-life and its performance and durability depend on many parameters, no standard performance criteria for the water repellent treatment could be defined yet. This study compares the economical and ecological impact of a water repellent treatment with the impact of repair measures. Results are meant to be used to define standard performance criteria. These criteria must take into consideration not only the performance with respect to the reduction of chloride penetration rate, but also garantee the required durability.The expected life-time of an untreated reinforced concrete element can be estimated by modelling the mechanism of chloride ion induced corrosion. Based on this value the frequency of repair measures within a planned service-life of 100 years can be determined. Comparing the ecological and economical impact of a water repellent treatment with the corresponding impact of repair measures allows us to the formulate performance criteria concerning the durability and the minimum required service-life of a water repellent treatment. The water repellent treatment has to prevent repair measures within the planned service-life of a structural concrete element. Technical criteria concerning the performance of a water repellent treatment within the minimum required service-life can be formulated.