Study On Low Temperature Performance Of Recycled Asphalt Pavement In Seasonal Frozen Zone

Reclaimed Asphalt Pavement(RAP)technology is an effective measure to achieve energy saving and emission reduction in the highway transportation industry.It is of great significance to improve the quality and efficiency of transportation development,reduce resource waste and reduce project cost.However,the low temperature performance of recycled asphalt pavement is the main factor that restricts the amount of old materials.In addition,the use of recycled asphalt pavement will be affected by complex climatic factors and driving loads,which will adversely affect its road performance and service life,especially in the freeze-thaw cycle of the seasonal frozen zone.The impact is even more pronounced.In this paper,only the low-temperature performance evaluation index of the recycled asphalt pavement under the freeze-thaw cycle condition and the optimal blending ratio of the old material are studied in depth.In order to study the effect of freeze-thaw cycle on the low-temperature performance of recycled asphalt pavement,this study selected AC-16 and AC-20 two grades of recycled asphalt pavement to comprehensively evaluate the low temperature performance changes from static and dynamic aspects law.The static test method uses low temperature splitting test,uniaxial compression test and trabecular bending test to determine the splitting strength,splitting strain,splitting strain energy,compressive strength,compressive strain,compressive strain energy,bending strength and bending.The strain test index was used to study the effect of freeze-thaw on the low temperature performance of recycled asphalt mixture.The test results show that the low temperature performance of the recycled asphalt mixture gradually decreases with the increase of the number of freeze-thaw cycles,and the more the old material is added,the greater the influence of the frozen material on the recycled material.And the test indexes such as splitting strain,splitting strain energy,compressive strain,compressive strain energy and bending strain have good regularity,and both decrease with the increase of freezing and thawing times.Therefore,it is proposed to evaluate the low temperature performance by splitting strain,splitting strain energy,compressive strain,compressive strain energy and bendingstrain index.Through the qualitative analysis of the splitting and compression test index curve,it is suggested that the old material content should not exceed20%,and the bending strain curve is quantitatively analyzed,and the best old material content of the graded AC-16 recycled material is 19.8%.The optimum amount of old material for grading AC-20 regrind was 16.4%.This will ensure full use of the old materials and ensure the durability of the road.The dynamic test evaluation method refers to the indirect tensile rebound modulus test method in the American AASHTO.The results show that the indirect tensile rebound modulus of recycled materials shows an increasing trend with the increase of freeze-thaw cycles.At low temperature,the asphalt mixture exhibits elastic characteristics,and the larger the dynamic rebound modulus,the smaller the deformation amount under the same load,and the lower the low temperature performance.By measuring the indirect tensile rebound modulus of the recycled material after the freeze-thaw cycle,it provides reference value for the design parameters of the recycled asphalt pavement structure in the seasonal frozen zone.