This study contributes to the development of a methodology for assessing concretes manufactured from waste materials. The methodology is based on the study of mortars containing an experimental waste: Municipal Solid Waste Incineration fly ash (MSWI fly ash) [1, 2].
The microstructure of concretes containing waste materials is likely to change considerably as the material ages due to the effects of carbonation, leaching, etc. These changes can affect the kinetics of penetration of aggressive agents inside the material and the kinetics of release of chemicals into the environment. The study of the microstructural evolution of concrete containing waste is therefore very important in order to predict its long-term behavior.
To study the long-term evolution of the microstructure of concretes containing waste during the leaching process, the CEMHYD3D hydration model developed at the National Institute of Standards and Technology (NIST) by Bentz and Garboczi [3] has been applied to cement pastes containing MSWI fly ash. The experimental study carried out to determine the input data needed for model execution has been presented in the first part of this article [4]. In this second part, assumptions of the model and the results obtained are presented.
The experimental study [4] has sufficiently characterized the MSWI fly ash so that it can be incorporated into the hydration model. The hydration of cement pastes in the presence of MSWI fly ash has then been simulated. The influence of MSWI fly ash on the quantity of hydrates formed and on the capillary porosity and its connectivity has in particular been studied. The evolution of the diffusion coefficient of pure cement pastes and cement pastes containing MSWI fly ash during leaching has been simulated. Finally, a macroscopic leaching model has been developed to assess the effects of the changes in transport properties of cement pastes containing fly ash on the kinetics of the release of chemicals into the environment.