Recommandations for preventing disorders due to delayed ettringite formation: technical guide

The aim of the present recommendations is to limit the risk of disorders occurring due to an internal sulphate reaction. The latter is caused by the delayed formation of ettringite in a cementitious material and occurs in particular because of a significant heating of the concrete intervened several hours or several days after its casting. It causes an expansion of concretew hich in turn generates a cracking of the structures. This reaction can be encountered with two types of concrete: heat-treated concretes and concretes cast in place in so-called critical elements. These recommendations are concerned with civil engineering structures and buildings comprising elements of important size that are in contact with water or subjected to a wet environment. They set the level of prevention to be achieved according to the category of the structure (or to the part of the structure) and to the exposure conditions. For each of the four levels of prevention selected, associated precautions are applied and associated checks are carried out. They also contain provisions relating to the design and dimensioning of structures, the composition and manufacture of concrete, and its pouring. The present recommendations combine a performance approach and specifications of means, and are an update of the previous 2007 recommendations they are replacing, taking into account new knowledge gained since.