Analysis On Formation Mechanism And Prevention & Control Factors Of Rutting Disease Of Asphalt Pavement

In the continuous development of asphalt pavement engineering application,the rutting problem will occur when the high temperature stability of pavement performance is insufficient.As one of the main diseases of asphalt pavement,rutting problem has always been the key point for researchers to study.At high temperature,the state of asphalt mortar changes from viscoelasticity to viscoplasticity,which results in the decrease of shear resistance of asphalt mixture.Then,asphalt mortar flows to the edge of wheel trace and the rutting occurs.In this paper,the mechanism of asphalt mixture rutting at high temperature is studied,and the prevention and control factors are put forward in order to provide some suggestions for reducing rutting in practical engineering.Firstly,the traditional classification of asphalt rutting is analyzed,and the total deformation of asphalt mixture rutting is decomposed from the structural point of view.From the structural point of view,the total rutting deformation of asphalt mixture can be divided into three parts: the first part is viscoplastic deformation,which is mainly caused by the deformation of asphalt mortar;the second part is compaction deformation,which is mainly caused by the secondary compaction deformation after the opening to traffic;the third part is the slip deformation of large aggregates.This part is mainly caused by the slippage of asphalt mixture under high temperature and the instability of the original stressed structure of aggregates.Secondly,the existing rutting test instruments,methods and indicators are analyzed.In view of the shortcomings of the existing test,a new indoor scale rutting simulation test instrument developed independently is proposed.The instrument includes temperature control system,mixture forming system,dynamic load system,measurement system,environmental simulation system,etc.The instrument can realize the forming of mix and rutting test to mrasure the rutting depth of asphalt pavement under the interaction of various natural and load environments.Compared with the old rutting tests,the experimental results show that when the same rutting deformation is produced,the new rutting instrument needs much more loading times than the traditional rutting instrument,and its rutting deformation growth rate is always lower than the traditional rutting instrument,which is more in line with the actual results of road rutting.It is a new multi-functional asphalt pavement rutting instrument.Then,the three components of rutting amount of asphalt pavement are calculated,measured and simulated: viscoelastic-plastic theory is used to calculate the viscoelastic-plastic deformation of asphalt mortar,new rutting instrument is used to measure the compaction deformation,and discrete element PFC2 D software is used to establish rutting model to simulate the slip deformation of large aggregates,which proves that the decomposition of rutting deformation of asphalt pavement from the of structural point of view is appropriate.It is found that the slip deformation of larger aggregate particles is the main cause of rutting on asphalt pavement,accounting for 85.21% of the total rutting deformation.The aggregates of 13.2-9.5 mm and 9.5-4.75 mm have the greatest contribution to rutting.The secondary compaction deformation is the secondary cause of rutting,accounting for 13.6% of the total rutting deformation,while the viscoplastic deformation of asphalt mortar accounts for only 1.19% of the total rutting which can be neglected in estimating the rutting deformation of asphalt pavement.Finally,the rutting prevention factors of asphalt pavement are analyzed,and the gradation of asphalt mixture is tested by Bayley design method based on the previous research.The simulation test results show that the high temperature shear resistance of asphalt mixture increases first and then decreases with the change of the amount of aggregate used in a certain grade of asphalt mixture.AC-16 asphalt mixture has the best CA ratio of 0.6-0.7,which can reduce the total rutting deformation by 3%-12%.When the CA value is more close to 0.7,the high temperature performance of asphalt mixture will be more prominent.For the rutting resistance of asphalt pavement,in addition to good gradation,the characteristics of raw materials such as asphalt,aggregates,mineral powder,rutting resistance agent,rigorous and standardized construction process are also particularly important.