Characterization of ash from biomass combustion for its use as filler in asphalt mixtures

Fly and bottom ashes are the main by-products derived from the combustion of solid biomass. Since the production of energy from this source is increasing, processing and disposal of its ash has become an environmental and economic issue. This research investigates the potential use of ash from biomass as filler in asphalt mixtures. Morphological, physical and chemical characteristics of twenty-seven different ashes and two traditional fillers were evaluated according to European standard EN 13043. Leaching tests were also performed in order to quantify possible release of pollutants. Experimental results show a wide range of values of almost all the investigated properties and low correlation with biomass type. As most of the ashes do not respect acceptance limits for grading and release of pollutants, it can be concluded that processing the raw material before its reuse is necessary. However, the low content of organic matter and harmful fines and the high stiffening power of the ashes suggest that ash from biomass combustion may be considered for the replacement of filler in asphalt mixtures.