Study On Properties Of Reclaimed Asphalt Mixture Based On Superpave Method

With the improvement of environmental protection awareness,the application of recycling waste asphalt mixture has gradually aroused people’s attention.As a way of high value utilization of recycled material(RAP),the old asphalt mixture recycling technology is being used more and more widely.First of all,relying on a large number of recovery materials after road repair and milling in Jilin Province,the aging degree of old asphalt in RAP material was evaluated,and the grade of old material and the ratio of oil to stone were determined.RAP was extracted,centrifuged and rotary-vaporized to obtain the old asphalt,and its performance was tested,and the old asphalt was confirmed as grade I mild aging.Secondly,according to the Superpave design method of Sup-19 hot reclaimed asphalt mix mix design.The road performance of reclaimed asphalt mixture with different dosage was studied.The results of high temperature rutting test,low temperature trabecular bending test,immersion Marshall test and freeze-thaw splitting test show that the addition of RAP and basalt fiber can improve the ability of asphalt mixture to resist shear failure at high temperature.When RAP content is 0%,10%,20%,30%,respectively,the bending tensile strength of the corresponding asphalt mixture increases by 3.1%～8.6%,3.6%～12.9%,2.5%～12.1%,1.7%～2.8%,respectively.Maximum bending strain were increased by 17.2%～ 25.9%,18.8% ～ 27.9%,10.6% ～ 26.7% and 14.0% ～ 19.0%.The addition of basalt fiber can slightly improve the water stability of asphalt mixture,because the fiber itself has the adsorption and reinforcement effect,when added to the asphalt mixture,the formation of uniform distribution of fiber network,prevent asphalt loss,increase the adhesion between asphalt and mineral,effectively control water infiltration,so when the fiber length does not change with the increase of fiber content,The water stability of asphalt mixture is improved.At the same time,in order to study the mechanical properties of reclaimed asphalt mixture,dynamic modulus tests of 5 test temperatures and 6 load frequencies were carried out on the formed specimens by universal testing machine(DTS).The test results showed that the RAP content of Sup-19 hot reclaimed asphalt mixture was inconsistent with the dynamic modulus change amplitude of reclaimed asphalt mixture with basalt fiber content.Compared with asphalt mixture without old material,the dynamic modulus of reclaimed asphalt mixture mixed with old material is slightly higher,and also increases with the increase of basalt fiber content.Through the test,it is concluded that the change of phase Angle has a certain rule.When the test working temperature is low or even normal temperature,the phase Angle decreases with the increase of load frequency,but when the test ambient temperature increases,the phase Angle is gradually reduced and then tends to a critical point,which is also because the recycled asphalt mixture is a viscoelastic material.Finally,the main curve of dynamic modulus and phase Angle was established based on the test data,so as to compare the influence of different influencing factors on the mechanical properties of reclaimed asphalt mixture,and obtain the optimal dosage of Sup-19 hot reclaimed asphalt mixture.Accordingly,the Witczak model was used to fit the predicted value and the measured value,and it was not difficult to find that the good of fit was 0.98.The prediction of dynamic modulus of reclaimed asphalt mixture is more consistent with Witczak model.