PURPOSES: Using recycled asphalt materials (called Reclaimed Asphalt Pavement: RAP) from existing asphalt pavement layers in newly constructed asphalt pavement is an essential option not only for lowering the construction budget but also for mitigating environmental pollution for society. For this reason, many pavement agencies in South Korea, the USA, and Canada have observed the effect of RAP on conventional asphalt pavement to evaluate and set proper material specifications and addable amounts. In this paper, effect of recyclable material on low-temperature performance of asphalt materials was investigated with two different mechanical tests. Among the recyclable material sources, RAP and Taconite Aggregate (TA), which is mainly produced in northern Minnesota (USA), were considered.
METHODS : To evaluate the low-temperature mechanical performance of a RAP mixture, two different experimental tests (In-Direct Tensile (IDT) low temperature creep test and Semi-Circular Bending (SCB) test) were considered. The mechanical parameters creep-stiffness, relaxation modulus, fracture energy, and fracture toughness were computed then compared.
RESULTS: More brittle characteristics were observed with RAP-added asphalt mixtures compared to the conventional asphalt mixtures, as expected. However, the differences of computed mechanical performances were not significantly distinct for RAP mixtures compared to conventional mixtures when the RAP proportion was around 20%, and with the addition of TA up to 20%.
CONCLUSIONS : It can be concluded that up to 20% of RAP addition (along with TA up to 20%) in a virgin asphalt mixture does not provide significant performance reduction. This addable proportion can be viewed as a successful minimum level when considering the addition of RAP to hot-mix asphalt (HMA). Moreover, applying TA with RAP could offer a successful alternative for asphalt recycling and the materials industry.

ABSTRACT
 1. INTRODUCTION
 2. MATERIALS AND TESTING
  2.1. Asphalt Material Preparation
  2.2. Experimental Work Part 1: In-Direct Tensile(IDT) Test
  2.3. Experimental Work Part 2: Semi Circular Bending(SCB) Test
 3. DATA ANALYSIS
  3.1. Comparison of Creep Stiffness and RelaxationModulus: Comparison 1
  3.2. Comparison of Fracture Energy and FractureToughness: Comparison 2
 4. SUMMARY AND CONCLUSION
 REFERENCES

• Ki Hoon Moon(Korea Expressway Corporation Pavement Research Division) | 문기훈 Corresponding Author
• Augusto Cannone Falchetto(Technische Universita¨t Braunschweig)
• Mun Jin Cho(Do-Kyeong Construction Corporation R&D Center) | 조문진
• Oh Sun Kwon(Korea Expressway Corporation Pavement Research Division) | 권오선