Based On Layer Function To Research The Method Of Asphalt Mixture Design

Against to the performance deficiency of resistance to rutting in high temperature and fatigue cracking in norma temperature in large temperature difference areas,this paper combines structure design and materials design to introduce new asphalt mixture design method for their asphalt pavements.First, the paper analyzes the formation mechanism of the rutting under the high temperature in asphalt pavement. Analyzed with the theory of viscoelastic layeres system and finite element analysis software, the shear stress at high temperature in asphalt surface under the wheel loads first increased and then decreased as the surface depth increases,and the peak shear stress arrives at 60mm away from the road surface. Combined with the actual deformation results of the pavement cores, the second layer of asphalt pavement is consided as the main layer to resist rutting.Secondly, the paper analyzed the formation mechanism of fatigue cracking in asphalt pavement. Calculated and analyzed with the theory of viscoelastic layeres system and finite element analysis software,we find that while the contact condition of the asphalt surface with the base is continuous completely,it does not produce tensile stress in asphalt pavement under the wheel load alone,but the maximum tensile stress appears under the asphalt surface 120mm depth under the temperature load and wheel load coupling; while the contact condition is smooth completely, the maximum tensile stress is produced at the bottom of the pavement.Thus, the third layer of asphalt pavement is consided as the leading layer to resist fatigue.Third, through the asphalt mixture design of the main zone to resist high temperature rutting, the paper proposed three gradation design mathods to resist high temperature rutting: Bailey method, SAC method, and Multi-level embeded shear method. The paper proposed a new evaluation index resistance to high temperature rutting-Shear Strength. Also it proposed a new high temperature rutting of asphalt mixture design method:using Shear Strength instead of the Marshall Stability to design the asphalt mixture.This method of the asphalt mixture design have better performance to resist high temperature rutting than the Marshall method. Lastly, through the asphalt mixture design of the main zone to resist fatigue cracking on the asphalt pavement, it proposed a new evaluation index of fatigue cracking-Tensile Strength and the new tensile strength test method-Semi-circular bending test. Also it put forward a new asphalt mixture design method to anti-fatigue cracking:using the Tensile Strength instead of Marshall Stability to desgin the asphalt mixture. This method of the asphalt mixture design have better performance to resist fatigue cracking than the Marshall method.