Degradation of cement materials: study of diffusion processes in real cracks

The aim of the present work is to study the concrete chemical degradation by diffusion phenomena. Accelerated degradation of ammonium nitrate is represented by finite-elements methods (FEM). This method made it possible (a) to simulate the diffusion and chemical degradation of cracked concrete, incorporating into the mesh a real geometry crack and (b) to study the influence of the crack geometric parameters (unit segments length, deviation angle, opening, etc.) on the diffusion and chemical degradation. The influence of the crack mesh on the simulation results is computed using FEM. In spite of this, and particularly when coupled phenomena are concerned, the various transfer proprieties present in the structure of the material, as diffusion, are badly represented by this kind of approach. It is demonstrated that only the resolution of the conservation equation of calcium in solution may be sufficient accurately to determine the degradation profiles of cementitious materials, and the theoretical results correspond with experiments.