Study On Design And Application Of Coarse-grained Stress Absorbing Structure Layer Mixture

Reflection crack have always been a common problem in semi-rigid base asphalt pavement and old cement concrete pavement surface overlay asphalt layer(commonly known as "White + Black").The results show that the stress absorbing layer of asphalt mixture laid the top of semi-rigid base or between the old cement concrete pavement and overlay asphalt layer can effectively prevent and control the phenomenon of reflection crack,and the sand granular asphalt mixture with 1.0cm~2.5cm thickness is often used as the stress absorbing thin layer.But the design thickness of sand granular stress absorption layer is thin,the anti-rutting ability is poor,and the objective phenomenon of poor smoothness in old cement concrete pavement,which makes the paving thickness of sand granular stress absorbing layer difficult to control,and the uneven thickness makes the stress absorbing layer become a weak part of pavement structure.In this study,a coarse-grained stress absorbing structure layer mixture is proposed,and study on the design method and practical engineering application.In this study,the mix ratio of the coarse-grained stress-absorbing structure layer mixture was designed by thecombination of CAVF method and GTM method;Calculation and analysis of different modulus and different thickness of coarse-grained stress absorbing structural layer mixture were carried out by means of finite element numerical analysis;and built the test pavement section by relying on the high-speed reconstruction and expansion project of Liunan,Guangxi.The mixture as a pavement structure layer with the role of stress absorption,can be used for the old cement pavement overlay asphalt layer of the bottom layer or semi-rigid base asphalt pavement structure below the layer,design thickness 5~11cm,with waterproof anti-cracking,anti-fatigue,prevention and control of reflective cracks and other multiple functions.The main conclusions of the study are as follows:(1)Combining the advantages of CAVF method and GTM method,this paper puts the CAVF method is used to gradation design and the optimum asphalt-aggregate ratio design by using the GTM method,and the coarse-grained stress absorption structure layer mixture designed by this method has excellent road performance.(2)The results of laboratory tests show that this kind of mixture has excellent high temperature stability,water stability,rutting resistance,low temperature crack resistance and fatigue resistance.Its large asphalt content design can improve the transverse tensile deformation ability of the mixture,enhance the stress relaxation,play the role of "stress absorption" and waterproof and anti-cracking,the mixture has the skeleton dense structure,has the good high temperature stability and the vertical resistance to the rut deformation ability,can be used as the pavement structure layer.(3)Using ABAQUS finite element software,a three-dimensional solid model of coarse-grained stress-absorbing structure layer composite pavement structure is established,and the stress of pavement structure under different modulus and different thickness of the coarse-grained stressed structure layer is calculated and analyzed.The results show that the stress absorbing capacity of the mixture of coarse-grained stress-absorbing structure layerwith lower modulus is better,and the coarse-grained stress absorbing structure layer is more effective when the thickness is of the 9cm.(4)The test pavement section of coarse-grained stress absorbing structure layer is paved,and the implementation process of the test road is monitored,and the results show that the paving effect of the test road is perfect.Compared with the asphalt pavement structure of sand granular stress absorbing layer,the coarse-grained stress absorbing structure layer can reduce the construction of one-time paving in practical engineering application,which is helpful to shorten construction period and reduce the overall cost of the project.