Zemedkun Bereket SAMUEL

Fundamental Study on Performance of Recycled HMA Mixtures with Various RAP Contents

Osamu TAKAHASH

 Reclaimed asphalt pavement (RAP) is a form of re-utilizing materials from existing pavements after reaching usable service life. Developed countries benefited by using RAP. Recently or in the future, developing countries should also adopt the reclaiming technology to reduce the environmental burdens and scarcity of resources.
 The present study aimed to assess a 5% interval of RAP content on mixtures properties. The study was undertaken on 0% (control), 20%, 25%, and 30% RAP containing mixtures. From the Marshall design parameters, all mixtures complied with the standard, except the 30% RAP containing mixture which showed a slight decrease of the void in mineral aggregate (VMA). Laboratory mixture performance tests evaluated rutting resistance, moisture damage and cracking resistance of recycled HMA. The result of Dynamic Stability (DS), which indicates potential rutting damage of HMA mixtures, showed that rutting resistance of mixtures improved as RAP content increased in the mixes. The indirect tensile strength test revealed that the moisture susceptibility of the control mix and the 20% RAP mixtures showed a similar tendency. Whereas, the 25% RAP mixture had better resistance to moisture damage compared to other mixtures. The outputs from the three-point bending test (3PBBT) for cracking properties showed that the control mix was ductile compared to other mixes. On the other side, stress value at failure for the 25% RAP containing mixture was higher than the other mixtures.
 The investigation concluded that a 5% RAP content difference affects rutting resistance and moisture damage of recycled HMA mixtures. It was observed that even when the Marshall design parameters of the recycled HMA mixtures showed the same tendency, the performance of mixtures had significant variation. Therefore, it is highly recommended to scrutinize the RAP content variation on mix design procedures in order to ensure a sufficient resistance to different pavement distress mechanisms.