Evaluation of degree of blending and its effect to performance of recycled hot-mix asphalt under different preheating conditions

This research comprehensively explored the function of preheating temperature and quantified the contribution of degree of blending (DoB) to performance of recycled HMAs. Five groups were designed, including no blending group, full blending group, and three experimental groups at preheating temperatures of 60 ºC, 110 ºC, and 160 ºC. It can be found that the preheating temperature played a positive impact on DoB and performance of recycled HMAs. As the preheating temperature increased by 50 ºC, about 0.13%~0.2% RAP binder can be additionally activated, and TSR, shear strength, and fracture energy of recycled HMAs can improve by around 6%~8%, 0.07 MPa~0.15 MPa, and 304.2 J•m2~335.4 J•m2, respectively. Moreover, the results showed that the performance of recycled mixes designed at preheating temperature of 60 ºC closed to that of no blending group, while the mixes designed at preheating temperature of 160 ºC can reach to that of full blending group.