Investigating the cracking performance of asphalt mixture containing RAP using different cracking indices

Due to environmental benefits and economic issues, the use of reclaimed asphalt pavement (RAP) in asphalt mixtures has become a necessity. However, mixtures containing RAP have poor performance against cracking at different temperatures due to excessive stiffness and aged binder. Therefore, evaluating the cracking performance of RAP is of great importance. In this research, the semicircular bending (SCB) test was used to evaluate fracture characteristics. For this purpose, the indicators of peak load (Pmax), fracture energy until failure (FEUF), fracture energy after failure (FEAF), fracture strain tolerance (FST), and power (P) are used. The SCB test was performed at 25 °C and − 12 °C, and all indicators were calculated at intermediate and low temperatures. Three different percentages of RAP (0%, 50%, and 100%) were used. Also, three different rejuvenators, Waste Engine Oil (WEO), Oleic Acid (OA), and Vacuum Bottom (VB), were used with four different doses. Then recycled high-density polyethylene (r-HDPE) in four different amounts (0%, 3%, 5%, and 7%) was used separately and in combination with rejuvenators to prepare the samples. Also, to expand the application of SCB tests worldwide, and due to the availability and simplicity of the Marshall device, non-standard samples with a diameter of 100 mm made by this device were used. Experimental results showed that the use of a rejuvenator alone, as well as in combination with the recycled polymer, could improve the cracking resistance of asphalt mixtures at medium and low temperatures. Results showed that VB performed best at 25 °C and OA at − 12 °C. An increase of 53% was seen in the FST index for the VB rejuvenator and 62% in the OA rejuvenator. Also, VB (at 25 °C) and OA (at −12 °C) improved crack propagation resistance by 62% and 94%, respectively. To evaluate the results, statistical analyzes were used. The statistical results showed that using the Marshall compaction device to make the samples has a suitable accuracy. In addition, the statistical results showed that the fracture behavior of mixtures containing RAP at a temperature of 25 °C differs from a temperature of − 12 °C