Investigation On Asphalt Mixture Balance Design Of Intermediate Layer Based On Layer Properties

The main tasks and ultimate goals of hot mix asphalt mixture design is to determine the grading and the optimal asphalt content for raw materials.Rut and cracks are the two main diseases on the road.Rut is associated with the ability to resist permanent deformation of asphalt mixture,fracture associated with the crack resistance of the mixture.And the asphalt content directly influences the mixture of these two kinds of ability:a high content of asphalt is beneficial to crack resistance of the mixture;When asphalt content is low,it is advantageous to the mixture deformation resistance ability.So,an HMA(overlay)mixture to perform well it must have a balance of both adequate rut and crack resistance performance.On the other hand,each asphalt layer has its own layer properties,the resistance to deformation characteristics and crack resistance characteristics of each layer are different.For example,for a three-layer asphalt pavement structure,the intermediate layer may has the largest proportion of permanent deformation contribution,while the bottom layer is more critical to the action of reflective crack and anti-fatigue crack.So,an ideal method for determination of optimal asphalt content,can be based on the comprehensive consideration of the deformation and cracking characteristics of different asphalt layers,and make the anti-crack ability and anti-deformation ability of asphalt mixture are relatively balanced.At present,many kinds of HMA designs are raised,such as Marshall methods,Superpave method,Hveem method,LCPC method,TxDOT method and so on.However,these method focused on rutting resistance more and often associated with cracking distresses such as reflective and top-down cracking.The optimal asphalt content obtained by different design can change.In addition,the optimal asphalt content has no relationship with pavement structure.Neither consider the pavement structure layer features,nor consider the thickness problem.This situation results in the poor correlation between the structure design of asphalt pavement and the material design of the mixture,and it is difficult to give full play to the anti-deformation ability and anti-crack ability of various asphalt mixtures.So,it is very important to study the balanced design of asphalt mixtures based on the layer properties.The focus of this paper is to develop an integrated hot-mix asphalt(HMA)mixture design method which can not only balances both rutting and cracking requirements,but also take each asphalt layer properties into consideration.The Hamburg Wheel Tracking Test(HWTT)and Overlay Tester(OT)devices were used to evaluate the rutting and cracking resistance of HMA mixtures,respectively.The upper limit value is optimized in the initial effective area due to the main anti-rutting ability in the intermediate asphalt pavement.Apply the permanent deformation parameters and the deflection at top and bottom of finite intermediate layer in the VESYS rutting prediction model,and calibrate the value of rutting prediction.Using permanent deformation contribution to calculate the intermediate layer rutting permissible value.Comparing rutting forecast and the intermediate layer rutting permissible value,determine the optimum asphalt content of intermediate layer.Intermediate layer as the research object,this paper puts forward the concrete steps of the method,and the feasibility of this method is also verified by using gradation AC-20.The results show that the asphalt mixture balance design method based on the anti-rutting characteristics of the intermediate surface layer is feasible and is a more reasonable design method of asphalt mixture.