Study On Fatigue Characteristics Of Asphalt Mixture With Interlayer Interface Under Long-term Aging

With the rapid development of our country’s economy and the rapid growth of highway construction scale,the national highway construction has tended to improve,but due to the increasing traffic volume,the traffic load is more heavy,and the influence of environmental factors makes the road prone to functional defects.However,at present,the research on overlay pavement in our country is not perfect,and there is no more accurate scientific guidance to the practical design and construction,so it is necessary to study the pavement overlay deeply.Through the three-point bending test of double-layer asphalt mixture and the oblique shear test,analyzed the damage and fatigue performance of AC-16SMA-13 under different aging methods,different stress ratios,different temperatures and different adhesive oil,conducted multifactor fatigue life fitting,analyzed the influence of different environmental conditions on the pavement and pavement,and the form of fatigue cracking,and the main research conclusions are:(1)The test results of double-layer asphalt mixture: under different bonding conditions,SBS modified asphalt adhesive layer can provide better bending and tensile performance;In different ways of aging,The worse the aging level,The brittle the asphalt mixture,the harder,The worse the fatigue resistance performance;The higher the stress ratio,The worse the fatigue life decreases,Heavy load overload greatly reduces the service life of the road surface;Asphalt mixture acts as a temperature-sensitive material,The improvement of the temperature will significantly reduce the fatigue life of the double layer small beam;Single-factor fatigue equation fitting for the double-layer asphalt mixture small beam by phenomenological method,A good linear relationship,Using SPSS statistical analysis software,A more reliable fatigue estimation equation is obtained.(2)Through the diagonal shear test results of asphalt mixture with interlayer interface,it can be seen that SBS modified asphalt as tack coat oil has better shear strength,followed by matrix asphalt;with the increase of temperature,the shear strength of diagonal shear specimen decreases obviously;with the change of aging mode,the longer the influence of thermal aging,the higher the shear strength;based on the evaluation of shear modulus,it is found that although the strength of oblique shear specimen increases,the fatigue property decreases significantly and it is difficult to resist repeated load;the fatigue performance of double-layer asphalt mixture is greatly reduced by using viscous viscous viscous layer oil;Based on fatigue life,the fatigue life of overlay pavement is estimated by multi-factor equation fitting of oblique shear fatigue with interlayer interface.(3)The digital speckle correlation method was used to synchronously observe the mechanical test of AC-16 + SMA-13 double-layer mixture.Through the analysis of horizontal displacement and horizontal strain field,it was found that in the bending test of double-layer beam,the interlayer as a weak area did not appear interlayer failure before the macroscopic crack appeared.When the crack was carried out from the weak position of the lower layer,the transverse crack would occur at the interlayer position,and then the crack continued to expand from the weak position of the upper asphalt mixture until the crack ran through the failure.Through the shear displacement and shear strain field in the inclined shear test,it is found that the shear displacement difference can obviously reflect the dislocation between the upper and lower layers,which seriously affects the performance of the overlay pavement;At the same time,it is found that the local compression of the mixture near the fixture contact area occurs in the specimen with interlayer viscous oil at the initial stage of loading.After that,the strain is concentrated in the interlayer position,and the interlayer stress increases gradually.The development and convergence of micro cracks evolve into macro cracks.Therefore,it is determined that the slope intersection position of the shear strain of the oblique shear specimen from the rapid rise stage of local compression and the slow development stage of interlayer dislocation is the beginning time of the linear development of interlayer displacement,and then the interlayer dislocation gradually develops until it is completely separated from the failure.To sum up,the temperature,thermal aging degree and traffic load have great influence on the fatigue performance of the pavement.In the process of longitudinal crack,the interlayer dislocation is easy to occur before the crack runs through,and the bonding effect is the key factor affecting the fatigue life.