Coupled transport-chemo-mechanical simulation of cement/aggregate samples affected by DEF at the aggregate scale. Effects of pre-cracked interface and comparison with experimental data

Concrete structures are widely used due to their long-term durability and strength; however, they are susceptible to deterioration and fracture once subjected to chemical reactions and/or mechanical stresses.One specific example of this type of degradation is the phenomenon of delayed ettringite formation that can occur under combined environmental conditions and exposure to high temperatures at early age.This often leads to the swelling, micro and macro-cracking and at a later stage the deterioration of massive concrete structures with loss of strength.In this context, the aim of the work is to predict, characterize and monitor the chemical and mechanical behavior of mature concrete affected by DEF pathology at "aggregate scale" using 3D numerical simulations.A composite parallelepiped sample composed of CEM I cement paste bonded to siliceous aggregate have been simulated to perform a qualitative comparison with experimental results (113 cm 3 sample dimensions).The chemo-poromechanical model is based on the coupling between a poromechanical model, in the framework of Frictional Cohesive Zone Model for fracture.The initial chemical parameters and mechanical properties of the cement paste have been estimated from the chemical composition of the cementitious mix that was used in the previous experimental work.The effect of the initial degradation at the interface between cement paste and the aggregate have been studied.Our work shows that the initial cracks affect the ettringite precipitation and hence modify the cracking pathology in the sample.These results show good agreement with the crack propagation and swelling evolution in the sample as compared to experimental data.