Sammendrag
Abstract Most concrete structures in Norway were built before 1980. Norwegian regulations to prevent damage due to alkali aggregate reactions (AAR) were, however, not introduced until the early 1990’ties. During the recent years AAR have been documented on an increasing number of concrete structures, and AAR is now regarded as one of the main deterioration mechanisms in Norway. Only a few Norwegian concrete structures suffering from AAR have so far been repaired. As a basis for planning and executing repair works, detailed condition surveys are required. As part of such surveys relevant laboratory analyses have to be executed, both in order to diagnose the cause of damage, e.g. AAR, and to evaluate the extent of damage over the structure.This paper presents the experiences from an extensive laboratory programme as basis for calculating the remaining load capacity of a huge Norwegian concrete dam installation with AAR. Focus is set on the results from the large number of plane and thin section analyses performed within this project. The results show a large variation in the extent of internal cracking, also in samples collected from the same structure parts. These experiences demonstrate the importance of collecting a large number of samples in order to get representative results.