| During the use of asphalt pavement,the road performance of asphalt mixture gradually deteriorates due to the effect of environment and load,eventually a series of pavement diseases appear,which shortens the service life of the asphalt pavement.Especially in the seasonal freezing regions in northwest our country,the freeze-thaw cycle phenomenon alternates frequentl y and the action period is long,it significantly increases the probability of cracks and other diseases in the early stage of the asphalt pavement.It will directly affect the traffic capacity of the road and increase the maintenance cost of the road at the same time.Therefore,study the law of the changes in low-temperature performance and mechanical properties of asphalt mixtures under the action of freeze-thaw cycles and clarify the development process of freeze-thaw damage.It is expected to guide the design and construction of asphalt pavement structure in seasonal freezing regions.The main contents of this article are as follows:1.The basic technical indicators of the experimental raw materials were determined.Through the Marshall design method,six kinds of asphalt mixtures were designed for the mix ratio,and the mineral gradation and the optimal asphalt content were determined.And verified its high temperature stability,low temperature performance,water stability and water permeability to ensure that it meets the requirements of the specification.2.First,conduct freeze-thaw cycle tests on six asphalt mixtures to test the void ratio of the asphalt mixture after the freeze-thaw cycle.It is concluded that the void ratios of the six asphalt mixtures gradually increase with the increase in the number of freeze-thaw cycles.Then,the low-temperature performance of the asphalt mixture and the degradation law with the number of freeze-thaw cycles were evaluated through the bending beam test and the indirect tensile test.The results show that the low temperature performance of the three asphalt mixtures is: rubber modified asphalt mixture>SBS modified asphalt mixture>base asphalt mixture.the AC-13 type is better than the AC-16 type.The low temperature performance of the six asphalt mixtures gradually decreases with the increase of the number of freezing and thawing,and the decreasing rate gradually decreases.Finally,the evaluation index and influencing factors of the asphalt mixture’s low temperature performance were analyzed,and it is concluded that the type of asphalt has the most significant impact on the low-temperature performance of the asphalt mixture,followed by the number of freeze-thaw cycles,and the aggregate particle size is the smallest.There is a linear relationship between the indirect tensile te st and the bending beam test evaluation index,which has a good correlation.It is more convenient to use indirect tensile test to evaluate the low temperature performance of asphalt mixture.3.A constitutive model of the uniaxial compression test conside ring the freeze-thaw damage of the asphalt mixture was established,and verified its results through uniaxial compression test.The results show that the constitutive model can better express the stress-strain relationship of continuous dense-graded asphalt mixture.There is an "S" type increasing relationship between the total damage variable and the strain.4.The creep process of asphalt mixture was analyzed through uniaxial compression creep test,and it is found that the creep process of asphalt mixtur e is divided into three stages: migration period,stable period and failure period.With the aid of the basic model of viscoelastic mechanics,the viscoelastic characteristics of asphalt mixture are characterized and analyzed.It is found that the creep constitutive model of coupled damage can characterize the complete creep three-stage deformation process of asphalt mixture.The uniaxial compression creep test was performed on the asphalt mixture after freezing and thawing.And it is found that the creep deformation of the asphalt mixture gradually increased with the increase of the number of freezing and thawing,and the viscoelastic parameters decrease. |
