STABILIZATION OF RESIDUE CONTAINING HEAVY-METALS BY MEANS OF MATRICESGENERATING CALCIUM TRISULPHOALUMINATE AND SILICATE HYDRATES

Two binding matrices based on blast furnace slag or fly ash/lime mixtu res were studied in relation to the stabilization/solidification of a residue from a municipal solid waste incinerator. Their use is of inte rest because of the formation of calcium trisulphoaluminate and silica te hydrates. Mixtures of the above matrices with up to 80% of the inci nerator residue were paste-hydrated and cured for 28 days at 25 degree s C and 100% relative humidity. The effect of added waste on the hydra tion phenomena was studied by means of differential thermal analysis a nd X-ray diffraction analysis. The effectiveness of these systems as s tabilization/solidification matrices was checked by means of mechanica l and leaching tests. Cured samples with up to 20-40% of added waste g ave compressive strengths sufficiently high for reuse as building mate rials. The U.S. Environmental Protection Agency leaching test has show n that disposal in a landfill in which no facilities for collecting an d 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 physica l binding potential of the matrices. (C) 1996 ISWA