Abstract: The invention relates to the preparation of a bituminous binder on the basis of bitumen and polyolefin. This binder is prepared in a hot mixing and homogenizing process, the homogenizing being continued until the viscosity of the binder in the course of this homogenizing being distinctly or significantly reduced. The invention also relates to the preparation of a road construction material using this binder, the inorganic additive material being heated before mixing with the binder to a temperature below the decomposition temperature of the binder.