Study On The Rutting Resistance Of Asphalt Mixtures In Middle And Lower Course

With the growing of transportation, increasing of heavy and channel traffics, the asphalt pavement rutting has become a remarkable problem.Anciently the rutting research focused on the mixture of the upper course asphalt, but according to the results of mechanical analysis, the max. Shear pressure is found under 5~10cm of pavement surface (the middle course). The research and investigation on asphalt rutting problem also showed that the most part of deformation in asphalt pavement occurred in the middle course. The middle course plays very important pole on the performance of anti-rutting of the whole pavement, it is necessary to study the performance of mixture of the middle course.Through a set of modified rutting test and Hamburg rutting test on the three type of mixtures used in the middle course and two type of mixtures used in lower course, which individually is AC-20I,modified AC-20I,Sup20,AC-25I,Sup25, not only the effect of the type of grade ,air void percent, bitumen content and properties of bitumen on the rutting resistances of the mixture in air and water bath are studied, but also the shortage of index of anti-rutting applied in China are analyzed. Some suggestions are presented to reduce the rutting of asphalt pavement.As the performance of anti-rutting is concerned, SBS modified bitumen mixture is much more excellent than AH-30 and AH-70 bitumen mixture and the AH-30 mixture is better than AH-70 mixture. If the modifies bitumen is applied, a little more binder content(<0.5%) does not endanger the performance of anti-rutting ,on the contrary, it can improve the rutting resistance in water. Both Sup20 and modified AC-20I mixture show better performance of anti-rutting than AC-20I. It is also showed that properties of bitumen play the most important pole in the rutting resistance in water and too more air void percent will severely weaken the rutting resistance in water. The index of performance of anti-rutting of the mixture has some shortages, it is advised to apply relative deformation and decide the level of requirement of the rutting resistance of the middles course.