MUNGUNKHULUG JARGALMAA

Study on the Mechanical Behavior of Asphalt Mixture with High Content of Reclaimed Asphalt Pavement

Osamu Takahashi

In recent years, the ratio of reclaimed asphalt pavement (RAP) into asphalt mixture in the asphalt pavement structures has increased to 70% or more, and the number of RAP that is repeatedly reused is increasing. However, previous studies have shown that repeated use of RAP deteriorates the quality of recycled aggregate, so it is expected that the RAP that meets the quality standards will decrease in the future. On the other hand, in order to maintain a high level of recycling in the future, it is also important to increase the RAP mixing ratio.
Therefore, in this study, we investigated the crack resistance of the recycled asphalt mixture using slightly low quality RAP at a high content ratio, and evaluated its effect. Then, as a measure to improve the performance of the regenerated asphalt mixture, the method of adding the regenerative additive was examined. 
As a result of the direct tensile test, the fracture stress did not change significantly with the increasing RAP content, but the strain at the time of fracture decreased significantly when the RAP content was increased. From this result, even if the quality is slightly below the standard, the fracture resistance is considerably reduced when the low quality RAP is mixed with high ratio.
Also, the strain at the time of fracture of the mix tended to decrease as the RAP’s curing time was lengthened. It is considered that the longer the curing time, the faster the deterioration and it leads to the low the fracture resistance. Therefore, it was confirmed that it is more appropriate to shorten the curing time after adding the additive to the RAP.
As in the case of the modified Lottman’s test, the indirect tensile strength decreased due to the increase in the low quality RAP content, but the Tensile Strength Ratio (TSR) was exceeded the standard value of 0.8 in spite of the RAP content. The test results indicate that the recycled mixes exhibited good resistance to moisture damage with high values.