Concrete deterioration mechanisms (A)

The environments in which we place our reinforced concrete structures mean that various deterioration processes affect their in-service durability, loss of functionality, unplanned maintenance/remediation/replacement, and in the worst cases a loss of structural integrity and a resultant safety risk. Cracks in concrete (plastic settlement, plastic shrinkage, early thermal contraction, drying shrinkage) are routes for the ingress of aggressive environmental agents. The penetrability of hardened concrete is also relevant. Degradation of concrete may involve chemical causes including: alkali aggregate reaction (AAR); delayed ettringite formation (DEF); sulphate attack; acid sulphate soils; thaumasite sulphate attack (TSA); acid attack; dissolved CO₂ attack; leaching and efflorescence; and physical salt attack (PSA).