SOLUBILITY MODEL FOR THE PORE SOLUTION OF LEACHED CONCRETE CONTAINING SOLIDIFIED WASTE

The long term behaviour of leached blocks of solidified wastes must be modeled from the results of laboratory experiments in order to predict the conditions of a long and safe storage. The solidification with Portland cement of two wastes has been studied: air pollution control residues from municipal solid waste incineration (named REFIOM) and slag from lead secondary smelting (named SCORIE). Both wastes are essentially composed of mineral salts and contain a high level of heavy metals such as Pb. Long term laboratory leaching experiments (more than 1 year duration) allowed us to observe the release of the soluble species. The leaching experiments were performed by contacting the blocks with pure water. A very good fit of the experimental results with the simulated data has been obtained by using a 3 dimension diffusional model for the very soluble ions (Na). In contrast to this situation, the release of heavy metals (Pb) is controlled by the chemical interactions within the solid matrix and by the changes in the pore water composition. The simple diffusion model must be improved in order to include these phenomena.