An environmental Risk Assessment of Concrete Based on the Reuse of Ashes from MSWI Incineration

Aiming to solve the environmental problems related with old-quarries and to develop new materials for underground constructions, the European Commission has approved, in 1998, the Valomat project, which was supported through the Brite-Euram III program. The main aim of this project was the development of new materials for quarry back-filling and underground constructions based on the re-use of MSWI bottom ashes from different European incineration plants. Six samples of bottom ashes were collected in six different incineration plants located in Belgium, France, Germany and Italy. These samples were submitted to the leaching process defined in the European standard EN 12457-2. The leachates were characterized for 21 inorganic chemical parameters, including heavy metals, and four ecotoxicological parameters (bioluminescence inhibition of the bacterium Vibrio fischeri, growth inhibition of the alga Pseudokirchneriella subcapitata, mobility inhibition of the crustacean Daphnia magna and germination inhibition of the vegetable Lactuca sativa). The ecotoxic assessment was based in the French proposal of a Criterion and Methods for Waste Ecotoxicity assessment (CEMWE). This methodology was developed with the goal to regulate the classification of residues with ecotoxic properties (residues under the code H14 of the European Council Directive 91/689/EEC). Based on the chemical and ecotoxicological results, the samples of bottom ashes were ranked in an ascending order of ecotoxicity. This ranking was crossed with their physical and mechanical properties and the most appropriate bottom ashes were selected for the development of new materials.The samples of bottom ashes selected were submitted to a physico-chemical process of stabilization and they were used to produce 14 new materials for quarry back-filling and underground constructions. These new formulations were also submitted to the same ecotoxic assessment as for bottom ashes. The chemical and ecotoxicological parameters referred above were used to characterize the leachates produced. The results obtained allowed to classify the new materials in function of their ecotoxicological level and to select the materials presenting the lowest ecotoxic risk to the environment.