Effect of Reclaimed Asphalt Pavement (Proportion and Type) and Binder Grade on Asphalt Mixtures

Reclaimed asphalt pavement (RAP) has been used in the United States for more than 25 years because of the benefits in costs and environmental stewardship. The recent substantial increases in asphalt prices have led asphalt technologists to examine the increase in RAP use. The evaluation of the performance of the asphalt mixture containing RAP is therefore a priority for the asphalt materials community. This paper investigates the effect of RAP percentage and sources on the properties of asphalt mixtures. Ten asphalt mixtures, including two different RAP sources, three RAP content percentages (0%, 20%, 40%), and two different asphalt binders (PG 58-28 and PG 58-34) were investigated in this study. The complex dynamic modulus was performed on all mixtures at different temperatures and frequencies, and semicircular bend (SCB) fracture testing was performed for all mixtures at three low temperatures. Experimental results indicate that asphalt mixtures containing RAP have higher dynamic modulus values than the control mixtures containing no RAP. The stiffer asphalt binder was found to result in higher dynamic modulus values for both the control and the RAP-modified mixtures. Experimental data also show that the RAP source is not a significant factor for the dynamic modulus at low temperatures, although it significantly affects; dynamic modulus values at high temperatures. In addition to test temperature, the RAP percentage was found to significantly affect the SCB fracture resistance or mixtures. However, for the dynamic modulus, values for the softer binder were higher than for the stiffer one at low temperatures. No significant statistical relationship between dynamic modulus and fracture energy was found.