Durability of Concrete According to Performance-Concept – Inspection of Bridges

In current codes the durability of concrete structures is usually guaranteed by describing mix design parameters such as maximum w/c-ratio, minimum cement content and minimum concrete cover. European and German standards (DIN EN 1992, DIN EN 206-1, DIN EN 13670 and DIN 1045 part 2 to 4) specify relevant requirements. However, it has been observed that there seems to be a contradiction between results of life cycle calculations based on fib-Model code and deemed-to-satisfy-rules used for durability in Germany. Hence, a research project was initiated to evaluate the performance of structures with respect to durability. The objective was to assess the condition of a representative group of structures planned and built according to current German standards. The sample was made of five bridges built with various cement types (CEM I, CEM II and CEM III) located in different parts of Germany. The bridges investigated were in use for 11 to 15 years. The aim of the bridge inspections was to come up with information about material performance and execution quality. Material tests were carried out in-situ on the structures and in the laboratory. The in-situ investigations consisted of visual inspection of concrete surfaces, measurement of concrete cover, measurement of electrical resistance and carbonation depth. Laboratory tests on concrete cores taken during the inspections were carried out to investigate concrete performance. The laboratory testing included compressive strength, carbonation depth, chloride content in various depths, chloride migration test and freeze-thaw-tests. This article covers the chlorides at various depths only.