The Performance Improvement of Hot Mix Asphalt and Enhanced Applicability to Pavement Structure Thickness Design Using DAMA (Drain Asphalt Modified Additive) Jung-hoon, Jin* * University of Incheon ITS. R.C. Researcher 4. Conclusion This research employed five kinds of HMA (dense graded 19mm, drain graded 13mm, drain graded 19mm, superpave graded 19mm, SMA graded 19mm) to produce optimal asphalt mixtures according to the Marshall mixture design. Then, an asphalt mixing additive, DAMA, was added into each mixture, and the additive effect on the mixture was evaluated for Marshall stability, compaction strength, indirect tensile strength, wheel tracking, and resilient modulus. The research result is now summarized as follows. 1.The asphalt mixtures of Marshall mixing method showed slight differences in stability and flow; however, all mixtures satisfied experimental prescribed conditions (dense graded 19mm, superpave graded 19mm, SMA graded 19mm Marshall Stability at or over 500kg, drain graded 13mm, drain graded 19mm, Marshall Stability at or over 350kg, flow 20¢¦40). Furthermore, the stability increased with increasing amount of DAMA added. 2. The flow value increased with increased amount of DAMA added indicating the effectiveness of DAMA additive on brittle failure during winter freezing season. 3. The compaction strength was the highest at 49.228kg/§² with 1% DAMA added for dense graded 19mm asphalt mixture, and then for superpave graded 19mm, drain graded 19mm, drain graded 13mm, and SMA graded 19mm in decreasing order. Even though the same asphalt binder was used, the compaction strength was higher with increased DAMA additive. 4. With the same amount of DAMA added, the indirect tensile strength showed significant differences according to each HMA types. When DAMA was added, the indirect tensile strength increased accordingly. 5. A comparison study using Wheel tracking test showed that dynamic stability increased in proportion to the amount of DAMA added for each HMA types. And for drain graded 19 & 13mm, the 1% DAMA added greatly increased dynamic stability in excess of Japanese standard (3000 per minute). 6. With 1% DAMA added, the layer coefficient derived from resilient modulus was as follows for each HMA types; dense graded 19mm - 0.172, drain graded 13mm - 0.160, dense graded 19mm - 0.172, superpave graded 19mm - 0.189, and SMA graded 19mm - 0.157. These values are greater or the same as 0.157, which is the value applied to domestic dense graded HMA surface layer by the Ministry of Construction and Transportation. 7. From the above, the laboratory test resulted in significant findings. Hence, these results show a promising reference data for the design of pavement thickness.