Assessing the extent of AAR in Finland

Finland has typically been considered a country with very durable granitic aggregate that is used in a wide range of construction applications. In general, the chemical reaction between Finnish aggregates and their surrounding environment is usually quite low. In this regard, the risk of Alkali Aggregate Reactions (AAR), where the alkalinity of concrete harmfully reacts with certain aggregates to cause expansion and cracking, has been considered negligible in Finland. However, when investigating reinforced concrete infrastructure in Finland for other types of deterioration attack, such as chloride ingress and frost-salt exposure, AAR has been found. AAR deterioration is limited to certain rock types. The geology of Finnish bedrock and soil is well studied and therefore there is a good general view of the composition of aggregates in different parts of Finland. This helps to estimate the potentiality of AAR. AAR has been investigated at VTT - Technical Research Centre of Finland by use of petrographic thin section microscopy. This paper shares the findings of 25 years of review from in-service structures, with respect to ASR findings. In addition, as new alternative hydraulic binders and aggregate sources (including recycled materials) are used in future concrete production, the mechanisms and risks of AAR need to be addressed in Finnish practice. The hope is that by initiating open discussions within Finland and abroad, the potential risk of future AAR deterioration can be evaluated and a process to handle AAR can be created to ensure concrete durability and service life of our structures.