STABILIZATION OF RESIDUE CONTAINING HEAVY METALS BY MEANS OF MATRICES GENERATING CALCIUM TRISULPHOALUMINATE AND SILICATE HYDRATES

Two binding matrices based on blast furnace slag or fly ash/lime mixtures were studied in relation to the stabilization/solidification of a residue from a municipal solid waste incinerator. Their use is of interest because of the formation of calcium trisulphoaluminate and silicate hydrates. Mixtures of the above matrices with up to 80% of the incinerator residue were paste-hydrated and cured for 28 days at 25°C and 100% relative humidity. The effect of added waste on the hydration phenomena was studied by means of differential thermal analysis and X-ray diffraction analysis. The effectiveness of these systems as stabilization/solidification matrices was checked by means of mechanical and leaching tests. Cured samples with up to 20–40% of added waste gave compressive strengths sufficiently high for reuse as building materials. The U.S. Environmental Protection Agency leaching test has shown that disposal in a landfill in which no facilities for collecting and treating percolating waters are provided, is possible with 40–60% of waste content. Finally, the American Nuclear Society dynamic leaching test has shown that the entrapment is mainly dependent on the physical binding potential of the matrices.