Methodology for Numerical Analysis of a Structure Affected by DEF

Delayed ettringite formation (DEF) is a pathology of concrete that permanently affects many massive civil engineering structures such as bridges, dams or nuclear power plants. Realistic numerical modelling of the behaviour of these structures is necessary to establish their safety and optimise their maintenance. At present, few numerical models are able to faithfully reproduce the structural behaviour of DEF at this scale because of the diversity of phenomena to be considered. Temperature, water saturation and amount of alkali act directly on the chemical balances involved. In addition, the correct evaluation of the pressure generated by DEF, creep and induced cracking is also essential. In this work, a thermo-hydro-chemo-mechanical model is applied to the aging phase of three laboratory beams from the bibliography with different reinforcement rates subjected to controlled young age heating. The methodology used in this paper is composed of two steps to calibrate and validate the calculations. The calibration phase is carried out on a sample, on the deflections of the beams and on the cracking pattern of the unreinforced beam, then, the validation is carried out on the chemical advancement obtained by coring, the other displacements and cracks on all the beams as well as on the stresses in the reinforcements. The model correctly reproduces the experimental measurements carried out on these beams attesting to the correct evaluation of the main phenomena involved. However, sensitivity to water and alkaline leaching is important. Multiphysics calibration is therefore necessary to obtain satisfactory results in terms of displacement, stress and cracking. For a predictive calculation of a structure, a parametric study also seems necessary.