Chemical modelling of Delayed Ettringite Formation for assessment of affected concrete structures

Delayed Ettringite Formation (DEF) modelling is addressed in the context of structural analysis. First, a chemical model is specified to simulate the effects of the heating of concrete in terms of reactions involving sulfates, aluminates and alkalis. It can be decomposed into: dissolution of primary sulfoaluminates at high temperature, fixation of aluminates in hydrogarnet or carboaluminates, and formation of delayed ettringite at low temperature. The influences of alkalis, temperature and water saturation on these reactions are taken into account. The main result of this model is the amount of delayed ettringite. The parameters of the proposed chemical model are fitted on a large number of experiments taken from the literature. The chemical model is then coupled with a nonlinear mechanical model based on poro-mechanics modelling. An application of chemo-mechanical coupling shows the features and benefits of such modelling to help practitioners in the management of structures affected by DEF.