Mechanical characterization of bituminous mixtures with bottom ash from Municipal Solid Waste Incineration (MSWI)

The paper discusses the results of a laboratory study, aimed to evaluate the suitability of bottom ash from Municipal Solid Waste Incineration (MSWI), obtained from different Italian plants, to be recycled in the lithic skeleton of bituminous mixtures, for base layers of road and airport pavements. The research involved a preliminary study of the leaching, physical and geotechnical properties of the bottom ash by itself; it was followed by a mechanical characterization of the bituminous concretes. The Marshall methodology was used to identify the optimum bitumen content; the mixtures were also mechanically checked by means of the indirect tensile strength test and the stiffness modulus test. The results can be considered completely satisfactory, being the Marshall Quotient up to 425 daN/mm, the Indirect Tensile Strength up to 0.95 MPa and the Stiffness Modulus, at 30°C and 124 ms, up to 1,344 MPa. Since the requisites for acceptance in the Italian Specifications and Standards have been satisfied and given the positive mechanical performances, it has been verified that the MSWI bottom ash can be used as substitution of the lithic materials in the road bases, also with relevant contents (up to 43% on the weight of the aggregate).