Abstract: The invention relates to a modification additive for asphalt masses and to the manner of production of asphalt masses for the creation of mineral-asphalt mixtures having a high shear modulus. The essence of the invention is a modifier, characterized in that it comprises 50 to 97% of cyclopentadiene oligomers, which are dissolved in 2 to 30% by weight of alkenes with 9-11 carbon atoms in a molecule, and 1 to 15% by weight of cyclic and aromatic olefins, wherein the latter are segregation residues of other hydrocarbon fractions. The liquid asphalt mass is added to the above-mentioned modifier in a quantity of 0.1 to 15% by weight at a temperature of no more than 185° C. and kept in a liquid state for at least 15 minutes. The modified asphalt obtained in this way, together with the mineral additive, forms mineral-asphalt mixtures having a high shear modulus.