In the past few years more damage in Finnish structures possibly associated with AAR has been noted. Therefore two summary articles were written to provide background about the AAR phenomena for the Finnish concrete industry and international colleagues [see publications].
1st Study - An Initial Survey on the Occurrence of Alkali Aggregate Reaction in Finland.
An initial project work was financed by The Finnish Transport Agency (Liikenevirasto) in 2011. The results of this work culminated in a VTT Technical Report and an AAR Seminar, organized and held at VTT on the 24th January 2012.
The objectives of the study were to clarify phenomenologically AAR and identify the locations and extent of occurrence in Finland. In addition the needs to proactively address AAR in Finland were identified, and the approach other Nordic countries have adopted for AAR was analysed.
As a result, the 2011 Finland survey documented a total of 56 cases of obvious AAR damage in Finnish concrete structures that have been investigated over the past 15 years. An obvious AAR case meant that gel could be detected in the cracks and/or aggregates. The survey further shows that AAR in Finland is not restricted to a specific location, but in general is widespread. In addition, many different types of structures where identified with AAR and different types of rock were identified as being the cause of AAR damage.
The results of this study clearly showed that AAR exists in Finland and identify the need for this topic to be addressed seriously. The report in both Finnish and English can be downloaded from Publications.
2nd Study – Further Research on Alkali Aggregate Reaction in Finland.
As a result of the 1st study it is necesary that the Finnish Industry accurately addresses AAR in ageing building and infrastructure stock on one hand, and on the other how to mitigate occurance of AAR in new structures by correctly understanding the reactive potential of concrete mix designs. Therefore, in 2012 VTT and several interested parties are discussing the needs for future research on this topic. These are presented below.
Objectives: The following tasks cover the most imperative needs:
• Task 1 – Petrography thin-section comparative study using existing cases, microscopy round-robin test – how to identify/classify AAR;
• Task 2 – Geological mapping of Finnish reactive aggregates originating from both the bedrock and surface deposits;
• Task 3 – Measure AAR levels – Laboratory experiments to define the potential for AAR occurrence, for instance using mortar bar & concrete prism tests following established international test method guidelines;
• Task 4 – Investigate structural sampling – field study of affected concrete structures – detecting damage with depth;
• Task 5 – Developing Finnish guidelines on how to assess AAR in existing structures and avoid AAR in new concrete structures.
• Prepare guidelines for petrography thin-section analysis to identify AAR, includin preparation of Finnish petrographic atlas of reactive aggregates;
• Quantify reactive potential of Finnish aggregates combined with Finnish cements and effect of mitigating actions (additions, air entrainment, etc.);
• Prepare Finnish guidelines on how to assess AAR in existing structures and avoid AAR in new concrete structures.