Aging Characteristics of Plant Hot-Mix Recycled Asphalt and Its Induced Aging on New Asphalt

Abstract

In order to explore the aging process and mechanism of new and old asphalt in plant hot-mix recycled asphalt mixture during the mixing and use process, the liquid viscosity test and low-temperature bending creep test are carried out to test the dynamic viscosity, stiffness modulus, creep rate, and low-temperature flexibility of the matrix asphalt, recycled asphalt, and old and new asphalt after rolling thin film oven test (RTFOT) aging and pressurized aging vessel (PAV) aging. The macroscopic performance attenuation law of new and old asphalt during the aging process in thermal regeneration is compared and analyzed. After that, the aging process and mechanism of new and old asphalt are explored by infrared spectroscopy and differential calorimetric analysis scanning. The results show that RTFOT aging and PAV aging make the viscosity of recycled asphalt rise significantly and the low temperature performance decline rapidly. After RTFOT aging and PAV aging of new and old asphalt, the dynamic viscosity and low-temperature performance change range is much higher than that of the matrix asphalt. Some technical indicators are even closer to the recycled asphalt after aging, which proves that its aging speed is faster than that of the matrix asphalt. Meanwhile, the results of infrared spectroscopy and differential scanning calorimetry analysis show that in addition to the independent aging of new asphalt and recycled asphalt, there is also a chemical effect between them–that is, some active groups in recycled asphalt have a more obvious promotion effect on the aging process of new asphalt, here called “induced aging”. This induced aging changes the aging mechanism of the matrix asphalt by changing the aging process of it, which greatly limits the popularization and application of thermal regeneration technology.