Final Report on the Phase 1 of the Assessment of Structures Subjected to Concrete Pathologies (ASCET): Appendices 3 and 4

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Taking into account life extension of nuclear power plants (NPPs) there is a need to investigate degradation mechanisms of existing structures defining their aging management program. The Alkali Aggregate Reaction (AAR) is observed in some concrete structures in Eastern Canada due to the presence of siliceous minerals in the aggregate used from the St. Lawrence River. At this time, there is neither regulatory requirement nor industrial standard which addresses the impact of this reaction on nuclear structures. The chemistry of the reaction is relatively well understood; however, the potential mechanical consequences of the chemical reaction, in terms of ultimate resistance of structural elements and overall structural behaviour as a function of time, are not well known. There is a need to establish the relation between the chemistry of AAR, with its evolution in time, and structural mechanic.

The Canadian Nuclear Safety Commission put in place a holistic approach with three interconnected axis of research: material, structural and numerical simulation aspect.

The present report is based on a SMIRT23 paper by Orbovic et al. (2015). With respect to the material aspect (Guatam et al., 2015), the goal is to perform testing program that determines the transient chemistry and mechanical properties of concrete samples subjected to accelerated environmental conditions for confined and unconfined specimens.