Impact Factors of Recycled Asphalt Mixtures Based on Indoor Environment Simulation

In order to solve the problem of the influence of environmental factors on the aging of uncompacted recycled asphalt mixture (RAP), the loose RAP was taken as the research object in this paper. The aging test of newly prepared AC-13 mixture was carried out under specific environmental conditions by controlling the temperature, humidity, aging time and oxygen concentration by using a special indoor aging simulation device. The results show that the aging of loose RAP mixture increase with the increase of test temperature, while decreases with the increase of air humidity and the decrease of oxygen concentration. The growth rate and final value of asphalt aging were different at various test temperatures, indicating that the chemical reactions in the aging process vary with the temperature. In the test of pure nitrogen, the asphalt did not have any aging effect, indicating that the aging of asphalt is only affected by the oxidation effect. The ball & ring softening point test results were more sensitive to temperature changes while the results of the dynamic complex shear modulus of dynamic shear rheometer (DSR) had a certain hysteresis effect on evaluating the aging of asphalt. The low temperature performance of asphalt mixture after aging was decayed. The long-term aging effect was the main contribution to this deterioration. The findings can provide guidance and reference for indoor preparation of RAP mixture and the evaluation of aging performance of uncompacted asphalt mixture in engineering.