Ceramic processing of municipal sewage sludge (MSS) and steelworks slags (SS)

Municipal sewage sludge from municipal wastewater treatment plants were thermally transformed into powders which were blended with two types of steelworks slags in different proportions. Mixtures of powders, performed by attrition milling, were pressed into specimens which were submitted to thermodilatometric tests in order to evaluate their shrinkage and then their softening temperatures on heating up to 1100 \ub0C. Samples were then sintered in air using a muffle furnace and characterized by density, strength, hardness, fracture toughness measurements, X-Ray diffraction and SEM investigations. The mechanical properties of the sintered specimens are satisfactory and this may be due to the formation of small grains that, in some cases, are embedded into a vitreous matrix. Samples obtained by the various blends were aged in an acidic (HCl) water solution to evaluate the elution of the components and it was observed that, through the sintering procedure, it is possible to limit the release of many of the most hazardous metals contained in the starting powders