Influence of moisture on the development of delayed ettringite formation

Delayed ettringite formation (DEF) is strongly affected by moisture. Thus, understanding the effect of this parameter on the related degradations is of prime interest, not only for prevention strategies, but also for re-assessment of affected structures. While alkali–aggregate reactions have been extensively researched, the effect of moisture on DEF still deserves to be studied, especially for exposure conditions representative of field exposure. This paper describes an experimental programme that aims to contribute to this objective. It consists in exposing concrete specimens with different DEF potentials to controlled moisture and water supply conditions, either constant or variable. The test results with these first conditions will help to determine the relationship between moisture and expansion, while test results of variable conditions will be used to benchmark these equations. To ensure exposure conditions are as stable as possible, a specific experimental set-up was developed and is presented in this paper. Moreover, determination of the wetting–drying cycles applied to some specimens is presented and preliminary results are displayed and analysed.