ASTEC INDUSTRIES, INC. asphalt group 21 Astec’s Double Barrel drum mixer dries the material in the inner drum and mixes asphalt in the outer shell. Part of the real-time quality control system from Astec’s PTI group The Astec RocDoc$^{TM}$ lab provides material analysis. The new TC 2000$^{TM}$ control system operates the plant via PC.