Research on the evaluation of the effectiveness of aged asphalt in RAP based on grey relational degree analysis

By testing the macro basic properties and micro chemical structures of the recycled asphalt and the base asphalt with different aging degrees, the performance parameters of the base asphalt when it is close to the full aging state, and the changes of the oxygen containing functional groups of the asphalt during the actual road use and indoor simulation are determined. On the premise of assuming that the aging degree of the new base asphalt is zero, combined with the gray correlation analysis among the indicators, the effectiveness of recycled asphalt is evaluated. The results show that with the aging of asphalt, its viscosity and three basic properties are obviously deteriorated, and the characteristic functional group index also shows a growth trend of first urgent then slow. However, when the aging time of PAV exceeds 80h, the changes of corresponding indicators are very small. Therefore, in this paper, the state of the matrix asphalt after 100 hours of PAV aging is approximately regarded as a fully aged state. Compared with sulfoxide index, the change trend of carbonyl index is more closely related to the change of macro performance. The grey correlation analysis method based on the carbonyl index can quickly approximate the effective rate of recycled asphalt, and provide a reference for the composition design of the subsequent recycled mixture.