INNOVATIVE MORTARS CONTAINING MSWI BOTTOM ASHES FOR QUARRY BACK-FILLING: ENVIRONMENTAL ASSESSMENT OF LONG TERM BEHAVIOUR

摘要

All over the world, a large amount of wastes mainly issued from thermal processes are candidate to being re-used as secondary raw materials in civil engineering materials. In 1998, the European Commission had approved the VALOMAT project (CEE Contract n° BRPR-CT98-0661) aiming at developing new civil engineering materials based on MSWI bottom ash valorisation using hydraulic binders. One of the proposed applications is quarry (or mine) back-filling by a bottom ash-based mortar. Our paper focuses on the environmental assessment, taking into account the properties of the new bottom ash-based materials and the conditions specified by the scenario. In order to assess the emission of the pollutants from the new materials in the scenario conditions, several steps are required and an adapted experimental and modelling approach, based on the ENV 12 920 European standard, is proposed.The main results obtained show that: 1. the experimental "toolbox" consisting of equilibrium tests and dynamic leaching tests is appropriate to provide the necessary information for modelling and long term prediction, 2. based on mineralogical and leaching data, the chemical modelling of the physico-chemical solid/liquid repartition (equilibrium) of the species in batch tests allows the determination of the chemical reactions involved, and then the prediction of the pollutants solubilisation in different chemical contexts, 3. the new materials (source term) present a low environmental impact at a given time scale and in the conditions specified by the application.