A bitumen polymer additive comprises a base of tire rubber crumbs in the amount of about 70 to about 90 percent by weight of tire rubber crumbs sized about 14 mesh or smaller. Added to that base is about 0.5 to about 5 percent by weight of a benzothiazole-based devulcanizing agent, about 0.3 to about 3 percent by weight of a C14-C18 heavy metal soap such as a zinc stearate, about 0.1 to about 3 percent by weight of an antiozonant, and about 0.1 to about 20 percent of a plasticizer such as a heavy oil. The additive polymer is used for producing an asphalt of superior quality, including lower initial viscosity and improved wear resistance.