Laboratory characterization and pilot site tests of residual sludge from dimension stones for civil and environmental applications

Residual sludge from dimension-stone working plants, both from gangue saws with abrasive shot and frame saws, is classified as waste and presents a number of problems for the stone industry. These problems include a fine size distribution, heavy metals and total petroleum hydrocarbon (TPH) content, all of which impede recovery and reuse. Residual sludge, management of which is administered in accordance with the Italian Legislative Decree 152/06, can be used in waste form for environmental restoration or for cement plants. However, it is also possible that sludge applications could go beyond these limited uses with incorporation of systematic treatment for the production of secondary raw materials (SRM), for example, filler, or for ‘new products’, for example, artificial loam. Such new products or SRM have to be certified not only on the basis of their technical and physical characteristics but also by means of appropriate chemical analyses to guarantee that the products are not contaminated. This paper outlines the results from laboratory and in situ characterization of residual sludge. In particular, three potential applications of sludge either by itself or mixed with other materials were evaluated: landfill waterproofing material, filler material for civil works and artificial soil for land rehabilitation.