Re-use of ashes from the combustion of municipal solid waste and biomass in bituminous mixtures

The paper presents an extended research work on the re-use of bottom and fly ashes of different origins in substitution of fine aggregates in bituminous mixtures. Bottom ash from a north Italian municipal solid waste incinerator (MSWI), and biomass bottom and fly ashes from twelve different power plants were considered. The MSWI ashes were vitrified at 1450°C. Vitrified MSWI ash and biomass ashes were ground and sieved to different dimensions and used as filler or sand in bituminous mixtures. Physical-mechanical tests included in road materials specifications were carried out on aggregates, mastics and on the whole mixtures. In this last case, ashes were used in partial or total substitution of natural aggregates. The test results demonstrate that vitrified MSWI ash and biomass bottom and fly ashes can be effectively re-used as pavement materials in order to avoid their landfill disposal. Moreover, the vitrification process reduces the ashes absorption potential of binder and the biomass ashes can be re-used in their original state if they are first subjected to sieving selection.