Abstract: An additive for a bituminous binder respectively a bituminous composite material, able to reduce bituminous binder respectively bituminous composite material viscosity when an alternating magnetic field is applied, in particular for healing pavement cracks and in-depth micro-cracks in asphalt, wherein the additive comprises an amount of magnetic iron oxide particles should be improved, in order to reach bituminous composite material respectively a bituminous binder which can be melted in a faster and simplified way, in particular usable for crack healing of asphalt structures on site. This is reached by forming the additive comprising at least a part of magnetic iron oxide nanoparticles with average sizes between 1 nm and 300 nm coated with a fatty acid.