Characterisation and technical feasibility of using biomass bottom ash for civil infrastructures

•Thirty samples of BBA from wood and olive trees were analysed.•Low density, high absorption and high organic matter content were observed.•Technical feasibility was proved according to the Spanish specification for roads.•BBA were classified as subsidiary material feasible as construction material.•The use of the ashes as a filler material in road embankments was proved. Biomass is a renewable energy source that is increasingly being used worldwide. However, because of recent increases in production, waste products from biomass combustion are becoming a relevant environmental and economic problem. In the present research, the technical feasibility of bottom ash from various Andalusian power plants is analysed to evaluate their potential use in civil engineering infrastructures. The physical, chemical and mechanical characteristics of this by-product is evaluated, and these parameters are compared to the technical specifications for roads imposed by Spanish regulation. It was determined that biomass bottom ash possesses acceptable properties to be used as a filler material in the core of road embankments over 5m in height without additional precautionary measures, such as the construction of road shoulders.