Service Life Assessment of Harbor Structures - Case studies of chloride ingress into concrete and sheet piling corrosion rates

Sammanfattning: Popular Abstract in English The two most used building materials in harbor structures are undoubtedly steel and concrete. These two materials are often combined in the structures of wharfs and quays where most steel sheet pile walls have cap beams of reinforced concrete. The degradation processes of these structures must be taken into account both when designing new structures and when inspecting existing harbor structures with the purpose of determining their remaining service life. Since the environmental loads on harbor structures differ substantially depending on their location, both globally and locally, the degradation processes also differ. Assessment of these types of structures must therefore combine general knowledge about degradation processes with knowledge about the local conditions. This PhD-project has focused on degradation of steel and concrete structures in harbor environments. The purpose of the work has been to increase the understanding of the degradation processes in order to optimize the design of new structures in marine environment, and to make better predictions of the remaining service life for existing load carrying structures. The results presented in this thesis come from both laboratory studies and from field studies in three Swedish harbors together with a large inventory of earlier performed ultrasonic thickness measurements on sheet pile quays along the Swedish coast. The results from the sampling of concrete specimens for determining the chloride ingress into concrete, is that core sampling and grinding gives less variations in chloride content using large core diameters compared to dry drilling and dust sampling with a small bore. If dust sampling is used in the field as the needed equipment is easy to handle, the dust sampling should be performed as mixed sampling from several bore holes in the same sampling area. From the results it is also clear that chloride contents should be expressed per mass of cement, not per mass of concrete. Regarding to the corrosion rate of steel in a marine environment, the main factor of importance is the temperature. The results from field investigations and field exposures indicate that neither the salinity nor the pH-value of the water has any major influences on the corrosion rate, at least not in the short time perspective.