The intensive construction of all categories of roads and the very demanding maintenance of the pavement structures of existing roads due to ever- increasing traffic loads confronts us with a lack of resources and also an increase in cost for the constituent materials of asphalt mixtures. On the other hand, there is another problem: large amounts of waste material in the form of bio-ash, which is obtained by burning waste wood biomass in the production of thermal energy and/or electricity. In order to solve the environmental problem of bio-ash disposal, research was conducted on the use of waste bio-ash as a constituent material in asphalt pavements. As part of this study, the effect of asphalt concrete mix, with bio-ash as a filler, on the release of harmful substances into the environment was investigated. The possibility of using wood bio- ash (BA) as a filler in asphalt mixtures was then determined through physical and mechanical property tests. The properties of the asphalt sample’s sensitivity to the action of water (indirect tensile strength ratio—ITSR) and resistance to rutting were tested for asphalt concrete type AC 11 surf with 50% bio-ash in the filler. It was established that asphalt concrete does not release harmful substances into the environment and that the 50% share of bio-ash in the filler results in asphalt that has good resistance to water sensitivity and even greater resistance to rutting.