Analysis Of The Influence Of Dry-wet Cycle On Mechanical Properties Of Dense Graded Asphalt Concrete At Medium And Low Temperature

Asphalt concrete pavement has many advantages,such as comfortable driving,low noise and so on,so it is more and more widely used.With the wide popularization of road civilization construction,artificial sprinkler,intermittent precipitation and so on,lead to the change of dry and wet state of roadbed.Asphalt pavement has to undergo countless dry and wet cycles during its use,but the influence on the mechanical properties of asphalt concrete after dry and wet cycle,especially the medium and low temperature properties,is not clear.Therefore,it is necessary to discuss the influence of dry and wet cycle on its mechanical properties according to the actual operating conditions.In order to clarify the influence of dry and wet cycle on the mechanical properties of asphalt concrete at medium and low temperature,indirect tensile test,semicircular bending test and digital image speckle technique are used to analyze the effect of dry and wet cycle on the mechanical properties of asphalt concrete at low temperature,and the dynamic stiffness modulus test is used to evaluate the effect of dry and wet cycle on the medium temperature stiffness modulus of asphalt concrete.The main results are as follows:(1)The indirect tensile strength is obtained from the indirect tensile test at low temperature.The failure strain increases at first and then decreases with the increase of dry and wet cycles,and the damage rate of single cycle strength and single cycle failure strain increases exponential with the increase of soaking time.The failure strain calculated by DIC is compared with that calculated by load-displacement,and it is found that the difference between the two data is small and the trend is basically the same.(2)From the low temperature semicircular bending tensile test,it can be seen that the bending tensile strength,bending strain,fracture toughness and fracture energy increase at first and then decrease with the increase of dry and wet cycle times,and the damage rate of each index increases exponential with the increase of soaking time.The trend of bending modulus and dry and wet cycle times is not regular.As a whole,with the increase of dry and wet cycle times,the damage rate of bending tensile modulus in single cycle increases with the increase of single immersion time,and the trend is veryobvious.(3)The dynamic stiffness modulus test shows that the dynamic stiffness modulus increases with the increase of the number of dry and wet cycles,and the loss rate of the single cycle dynamic modulus increases exponentially with the increase of the soaking time.(4)The low temperature mechanical index of asphalt mixture specimen is relatively poor when the number of cycles is one time and the immersion time is 288 h.When the number of dry and wet cycles reaches a certain number,the mechanical index continues to decrease,and when the soaking time reaches a certain degree,the damage rate per unit cycle increases sharply.From these two factors,with the increase of dry and wet cycles and the prolongation of immersion time,the mechanical properties of asphalt concrete at low temperature have a great negative effect on the mechanical properties of asphalt concrete at low temperature.