An algorithm for the use of MSWI bottom ash as a building material in road pavement structural layers

•0/2 fraction of MSWI bottom ash improves the soil.•MSWI bottom ash mixtures (with crushed gravel and without) have high permeability.•MSWI bottom ash mixtures can be used for unbound base and sub-base layers.•0/2 fraction of MSWI bottom ash improves asphalt mixture performance. Municipal solid waste incinerator (MSWI) bottom ash (constituting approximately 80–90%) and fly ash are by-products of the incineration of solid waste. In general, MSWI residues are primarily discarded into landfills. To address the continuous growth of landfills and to implement zero waste and circular economy policies, researchers are focusing on more efficient ways of using MSWI bottom ash. To that end, the best practices show that MSWI bottom ash is suitable for civil engineering applications, especially roads. Therefore, the subject of this research was the performance of subgrade and different unbound and bound pavement structural layers containing bottom ash. An algorithm was also introduced to facilitate the use of MSWI bottom ash as a building material. Soil and mineral aggregate mixtures with different percentages (0–100%) of bottom ash were designed and analysed, and more than 10 testing subjects containing a high amount of MSWI bottom ash were tested in the laboratory. The research revealed the suitability of the 0/2 fraction of bottom ash to improve soil and to enhance the performance of asphalt concrete mixture AC 16 PD in which the 0/4 fraction of sand is replaced with the 0/2 fraction of bottom ash. Furthermore, the suitability of mixtures composed of mineral aggregates and MSWI bottom ash or only of MSWI bottom ash (100%) to construct sub-base and base courses was confirmed.