Study of the Evaluation Model about Old Asphalt Pavement Service Performance of Freeway

In China, about 70 percent pavement of freeway is asphalt surface, most old pavement has 4 lanes, with the increase of traffic volume, the service performance of pavement can not meet the traffic demand and pavement needs to maintain. Before expanding lanes or maintaining pavement, it needs to evaluate the existing pavement condition. After having analyzed the service performance of old pavement and its evaluation methods, the paper introduces an improved gray correlation degree model to evaluate old pavement performance based on the factors of testing methods, different direction vehicle axle and different pavement sections of highway project. The model considers the fact of pavement repair and puts forward a repair index for the first time. Then the grade of indexes in the model is given according the testing data. At last, this paper demonstrates the applicability and feasibility of the model combined with existing criterions of China and with the application results of several pavement projects for four years which has 4 cm thickness asphalt pavement overlay.