How to deal with Structures affected by Delayed Ettringite Formation

The expansive sulphate internal reaction of concrete due to Delayed Ettringite Formation (DEF) can damage concrete structures severely. DEF is defined as the formation of ettringite in a concrete after setting, and without any external sulphate supply, but with water supply. This phenomenon occurs in concretes exposed to frequent humidity or contact to water, and subjected to a relatively high thermal treatment (> 65°C) or having reached high temperatures during casting. This reaction may cause large structural disorders due to unexpected deformations and additional stresses in concrete and reinforcement, and the problem is therefore to know how to deal with such structures affected by DEF. The prediction of future deterioration, the appraisal methodology and the assessment of the efficiency of remedial operations are crucial points for existing affected structures whose serviceability and structural safety may constitute a serious concern.