Study On Low Temperature Crack Resistance Of Hot Recycled SBS Modified Asphalt Mixture In Central Plant

Insufficient low temperature crack resistance is an important factor that restricts the utilization rate of recycled old materials,and is also an important problem for asphalt pavement in cold area.Lack of low temperature crack resistance will lead to more fine cracks in the early time of the road.Under the load and temperature circulation,the small cracks will slowly expand to make large lateral cracks on the road,which will reduce the service quality of the road and affect the safety of road.In this paper,the low temperature anti-cracking performance of recycled mixture under different influencing factors was studied by laboratory experiments,aiming at improving the low temperature crack resistance of reclaimed asphalt mixture under high content in central plant.First,the technical indicators of the recycled raw materials were determined by testing and analyzing the pretreated recycled raw materials.Then,based on the Beray method,the mineral gradation of the recycled asphalt mixture was designed,and the composition analysis of the reference material was carried out by the gray correlation analysis method,and the proportion of each material in the reference material was determined.Finally,the effects of regeneration process,reference material and fiber on the low temperature crack resistance of the recycled mixture were studied by low temperature splitting test,trabecular bending test and trabecular creep test.The test results show that the basic indexes of the recycled raw materials meet the requirements;compared with the AC grading,the regeneration grading optimized by the Beray method has good volume index and mechanical index,and better the low temperature performance;The factors that have the greatest influence on the low temperature performance of the mixture by the low temperature splitting test are the recycled asphalt pavement(RAP)content,followed by the mixing temperature and the RAP mixing time.When the RAP content increased from 20%to 40%,the splitting strength decreased by 32.5%,the mixing temperature increased from 160? to 180?C,the splitting strength increased by 37.3%,and the RAP mixing time increased from 120s to 240s.The splitting strength was increased by 11.9%,and the optimum mixing method under different RAP rat was determined by the orthogonal combination method and experiment.According to the trabecular bending test,under the same RAP content,the bending strength and the maximum bending strain have peaks with the RAP-F ratio in the reference material,and the reference material determined by the gray correlation analysis method.The flexural strength and the maximum bending strain of the recycled asphalt mixture determined by the grey correlation analysis method are the bestst.The gray correlation analysis method can effectively analyze the composition design of the reference material and reasonably match the thickness ratio of the reference material.Improve the low temperature performance of recycled asphalt mixture;Appropriate reference material ratio can effectively compensate for the shortcomings of the high RAP content on the low-temperature performance of the recycled mixture.When the RAP content is increased by 10%,the maximum bending strain of the asphalt mixture with the C reference material as the recycled raw material is slightly higher than that of the asphalt mixture with the B1B2 reference material as the recycled raw material.With the increase of RAP content,the low temperature performance of recycled asphalt mixture decreased by the variation of low temperature splitting strength,trabecular bending strength,maximum bending strain and trabecular bending creep rate index.The low temperature performance of the recycled mixture has a certain improvement effect,but as the RAP content increases,the improvement effect is smaller.