Alkali Aggregate Reactions (AAR) in Norway: Thin section analysis and expansion measurements from a dam and a bridge

Abstract

Two concrete structures with AAR have been investigated. The structures are a dam and a bridge, both approximately 30 years old. Both structures have a characteristic crack pattern on the surface of the concrete. Thin section analysis showed clear signs of AAR around aggregate particles consisting of quartzite, sandstone and metha rhyolite. To assess the remaining reaction potential of the concrete, expansion measurements were performed on drilled cores from the structures. The cores were stored in 40 C and 100 % Relative Humidity. The results showed an initial swelling due to increased moisture content but after that no expansion was measured up to 16 months. The implication of these results is that there is no more expansion potential in the concrete and consequently that repairs can be carried out. However, because of little experience with this method in Norway we feel there is a need for investigations with other methods as a supplement to these results.