Fracture Resistance of RAP Containing Recycled Polyethylene and Different Rejuvenators at Low and Medium Temperatures Using a Nonstandard SCB Test

Reclaimed asphalt pavement (RAP) contains significant amounts of valuable materials, which in new construction in the pavement industry contributes to sustainable development and promoting a circular economy. However, the use of RAP presents challenges. The most critical RAP challenge is cracking at low and medium temperatures. Therefore, it is necessary to use a robust and available tool to evaluate the performance of RAP cracking. The semicircular bending (SCB) test is considered an appropriate and helpful option to describe the cracking behavior of asphalt mixtures. The available standards for the test mentioned above are compiled based on samples with a diameter of 150 mm. However, the equipment to construct 150 mm cylindrical samples cannot be accessed in different parts of the world. Thus, the Marshall compactor was utilized to build SCB samples and examine RAP cracking resistance. Three different percentages of RAP, 0%, 50%, and 100%, were applied to make the samples. In addition, three different rejuvenates, waste engine oil, oleic acid (OA), and vacuum bottom (VB), were used. Each of the rejuvenators was added to the samples in four different percentages. Then recycled high-density polyethylene was first used individually, then combined with rejuvenators, and used at four different rates, 0%, 3%, 5%, and 7%. In the next step, the SCB test was performed at two temperatures, $-12°\mathrm{C}$ and 25°C. Next, fracture characteristics at low and medium temperatures were calculated using indices such as fracture toughness, fracture energy (Gf), crack resistance index (CRI), balanced crack index (BCI), and toughness index (TI). Then the results were compared with previous studies based on standard samples. Results indicate that VB at 25°C and OA at $-12°\mathrm{C}$ perform best. The BCI was observed to have increased by 41% at 25°C for the sample containing VB, while the CRI showed a significant increase of 62% at $-12°\mathrm{C}$ for the sample containing OA. Furthermore, the simultaneous use of OA and polymer had the most significant effect on resistance to crack. So, the crack resistance index improved by more than 54% at $-12°\mathrm{C}$ temperature. Finally, statistical analyses were performed, such as coefficient of variation, analysis of variance, correlation, and Tukey. Based on the results, utilizing the Marshall compactor to perform the SCB test exhibited reasonable accuracy.