Einfluss von wasserabführenden Schalungsbahnen auf die Dauerhaftigkeit von Betonbauwerken

摘要

The use of water-repellent formwork liners should improve the impermeability, and therefore the durability, of a concrete structural element. Their effect and also, for economic reasons, the possible number of times that they can be re-used had to be determined for the production of concrete piles for the 36-km-long Hangzhou Bay Bridge in China. Laboratory trials were used to assess the water absorption capacity, concrete surface strength and resistance to chloride penetration of concretes that had been moulded with different formwork liners and, for comparison, with conventional formwork. The results of the investigations are explained in the article. The use of water-repellent formwork liners lowers the water/cement ratio and the porosity of the moulded edge zones and greatly improves the durability of the concrete structure. The use of water-repellent formwork liners for concrete structural elements can therefore be recommended, especially for hydraulic engineering structures, wastewater plants and dockyards as well as in bridge construction. The service life of concrete structures in seawater and of the structural elements in bridges that are exposed to de-icing salt is affected by the penetration of chlorides. The chloride diffusion coefficient can be used to assess the resistance to chloride penetration. During the investigations that were carried out it was found that the penetration resistance can be substantially increased by the use of water-repellent formwork liners. Zemdram~? Classic and Formtex~? were still very effective with respect to chloride penetration resistance even when used 3 or 4 times. The Neptune formwork liner was less effective. In the present case the test results that were obtained led to the decision to use water-repellent formwork liners for concreting the piles of the Hangzou Bay Bridge standing in seawater in the tidal and spray-water areas. The spray water area covers the section of the bridge between + 1.88 m and + 10.21 m above mean sea level. The dense smooth surface of the concrete piles achieved with the Formtex? formwork liner is also expected to provide protection against the adhesion of aquatic animals and plants.%Durch die Verwendung von wasserabführenden Schalungsbahnen soll die Dichtigkeit und damit die Dauerhaftigkeit des Betonbauteils verbessert werden. Für die Herstellung der Betonpfeiler der 36 km langen Hangzhou-Bay-Brücke in China sollten ihre Wirkung und aus wirtschaftlichen Gründen auch die m?gliche Anzahl ihrer Wiederverwendung ermittelt werden. Zu diesem Zweck wurden in Laborversuchen die Wasseraufnahmef?higkeit, die Betonoberfl?chenfestigkeit und der Chlorideindringwiderstand von Betonen festgestellt, die mit unterschiedlichen Schalungsbahnen und im Vergleich hierzu mit einer herk?mmlichen Schalung geschalt waren. Die Untersuchungsergebnisse werden in dem Beitrag erl?utert.