Assessing Alkali-Carbonate Reaction-Induced Damage in Critical Concrete Infrastructure: The First ACR-Affected Field Structure Reported in Brazil

Alkali-carbonate reaction (ACR) is an internal swelling reaction (ISR) rarely identified in the field. While ACR has been extensively studied in laboratory using known reactive aggregates, such as the one from Kingston, Ontario, the scarcity of field cases limits the understanding of ACR's behavior in critical infrastructure. This paper details a comprehensive condition assessment of concrete structural members affected by ACR bearing no secondary products. Affected sleepers with ten years in service in northern Brazil were multi-level assessed (i.e., microscopically and mechanically) and the chemical composition of the aggregate particles and the cement paste were determined by XRF and XRD. The results uncovered that aggregate chemical composition felt within the potentially expansive thresholds specified by CSA A23.1-14/A23.2-14 for ACR and calcite and brucite are present in the system. The multi-level assessment outcomes further reinforce the hypothesis of ACR with a low damage level. In conclusion, this group of sleepers is likely affected by ACR much less aggressively than previously observed in concrete members incorporating Kingston aggregate.