Research On Optimization Of Asphalt Pavement Materials With Graded Macadam Base

Asphalt pavement with graded crushed stone base layer often has a long service life and pavement diseases often occur on the upper layer of the pavement.Thus,structural damage is less likely to occur,saving the cost and time of road maintenance and reducing the impact on traffic.This paper discusses the influence of various factors on the mechanical response of graded crushed stone base asphalt pavement,the performance study of surface asphalt mixture,the study of asphalt stabilized gravel layer materials,the study of graded gravel layer materials,and recommendation of material combination under different traffic volumes for the recommended structure of long-life graded gravel base asphalt pavement,in order to provide a meaningful reference for realizing long-life asphalt pavement with graded crushed stone base.Firstly,this paper summarizes the structural forms of flexible base asphalt pavement,and compares and analyzes the mechanical response of typical structures of semi-rigid base asphalt pavement,graded macadam base asphalt pavement and inverted structure asphalt pavement.In order to analyze the influence of various factors on the mechanical response,the changes of typical structure layer bonding state,wheel pressure,axial load,structural layer modulus and structural layer thickness of graded gravel base asphalt pavement were carried out respectively.In addtion,by controlling the tensile strain at the bottom of asphalt layer to 60με and the ultimate compressive strain at the top of subgrade to 200 με,the structural form of long-life asphalt pavement with graded macadam base is recommended.Secondly,this paper researches on surface materials.The influence of asphalt grade,modifier type,gradation(4.75 mm sieve pass rate)and modifier content on anti rutting performance of AC-13 graded asphalt mixture were studied at 60 ℃ and 70 ℃.In addition,by adding anti rutting agent to SBS Ⅰ-D modified asphalt mixture and hard asphalt mixture,the anti rutting performance of composite modified asphalt mixture and hard modified asphalt mixture is compared and analyzed.Then,uniaxial compression dynamic modulus test is carried out for AC-13,AC-20 and AC-25 gradation asphalt mixture,which is convenient for subsequent optimization of surface layer materials.At the same time,the two-stage analysis model of rutting occurrence is used to fit the rutting test data of three grades of asphalt mixture,and the relationship between the rutting depth and the rutting performance evaluation index of asphalt mixture is optimized.Thirdly,this paper researches on material of asphalt stabilized macadam layer.The fatigue life of ATB-25 graded asphalt stabilized macadam under 200,400 and 600 μεwas studied by four point bending fatigue test.The influence of asphalt grade,maximum nominal particle size,oil aggregate ratio and modifier type on fatigue performance of asphalt stabilized macadam was studied,and the fatigue performance of composite modified,hard modified and rubber asphalt stabilized macadam was studied.Then,uniaxial compression dynamic modulus test is carried out for all kinds of asphalt stabilized macadam,which is convenient for the subsequent optimization of asphalt stabilized macadam materials.In addition,the rutting test data of asphalt stabilized macadam are fitted through the two-stage analysis modulus of rutting occurrence,and the relationship between rutting depth and rutting depth is established to verify the optimization of rutting evaluation index in Chapter 3.Fourthly,this paper researches on mechanical properties and deformation characteristics of graded crushed stone layer.Through dynamic triaxial test and California bearing ratio test,the influence of water content,stress state and compactness on dynamic modulus and CBR value of graded crushed stone are studied.At the same time,through the dynamic triaxial test,the influence factors of the permanent deformation of graded macadam are analyzed,which provides the basis for optimizing and studying the structural design of graded macadam base asphalt pavement.Finally,combined with the long-life graded macadam base asphalt pavement structure recommended in Chapter 2 and the test results of dynamic modulus of each structural layer material in this paper,the material of each structural layer of asphalt layer is preliminarily optimized.Then,the asphalt layer permanent deformation of different structural layer material combinations is checked under light,medium,heavy and extra heavy traffic volume,and the layer material combination of long-life graded macadam base asphalt pavement under different traffic volume is optimized.The results are shown at the end of Chapter 2.