Study On High Strength Graded Macadam Base Of Asphalt Pavement

Semi-rigid base has been widely used in the base of high grade highway in our country because of its high strength,good stability,high bearing capacity and good anti fatigue performance,However,semi rigid base asphalt pavement in the normal operation of the process is prone to reflective cracks and water damage and other diseases,affecting the service life of the road surface.Between asphalt layer and semi-rigid base paving a graded crushed stone base with a fine-quality,dense and a certain thickness thickness,can effectively alleviate the cracks and water damage of semi-rigid asphalt pavement reflection phenomenon,but the strength and stability of Graded Macadam Base is poor,in the traffic loads is easy to produce permanent deformation.In order to effectively improve the performance of the graded crushed stone,this paper will conduct a comprehensive study on the graded crushed ishihara material,mixing ratio,molding methods,adding polypropylene fiber,construction technology and other aspects.Introducing the basic properties and influencing factors of graded crushed stone materials,optimizing the graded broken ishihara material technical requirements and grading range,according to the raw materials test results of screening test and vibration compaction test,determine the gravel gradation curve,optimum water content and maximum dry density,and based on the gradation,the best water content and the maximum dry density of the graded crushed stone were determined by heavy tamping,and with CBR,lateral compressive tests to verify its performance,test result show that the graded aggregate by vibrating compaction has good performance.Compared to the heavy compaction,vibration compaction of gravel CBR value increased by about 45%;to no lateral compressive strength,the graded crushed stone specimens with heavy compaction can not be demoulding and the no lateral compressive strength of the graded crushed stone specimens with vibration compaction can reach 1.02MPaThrough the indoor static analysis of three axis different molding methods on the shear strength of Graded Macadam stress-strain curve and mechanical technical index compression test comparison,results show that the shear strength of the crushed stone can be improved effectively by using the vibration compaction,in which the cohesion C of the vibrating compaction specimen increases by 64%.On the basis of the vibrating compaction,the polypropylene fiber were added into grading macadam mixture,to improve the comprehensive performance,and through splitting test to determine the optimum content of fiber in fiber graded is 1‰,through CBR,without lateral compression,three axis test performance were studied and results showed that after adding fiber,the CBR value of graded crushed stone was increased by about 23%,the compressive strength was increased by 13%,and the cohesion was increased by up to 36%.In order to further study the road performance of high strength graded base,4 kinds of asphalt pavement structure were selected for accelerated loading test.At high temperature(50 degrees Celsius)condition,comparative analysis of four kinds of anti rutting performance of asphalt pavement,under normal conditions,comparative analysis of the pavement rutting resistance,bearing capacity and dynamic response of four kinds of pavement structure,test results show that the high strength asphalt pavement graded gravel pavement bearing capacity and anti rutting performance are good.Using BISAR3.0 software to analyze the influence of the asphalt pavement design parameters of each structural layer of pavement structure stress,provide a reasonable theoretical basis for the design of pavement structure of asphalt pavement of high strength graded macadam base,and provides a related design reference values.Based on the high strength graded Macadam Base test road of Zhangjiakou Er Qin expressway,the construction method of high strength graded Macadam Base is studied in order to ensure strength and stability of the base.In the course of the study,put forward clear requirements process of mixing,transportation,paving and rolling of mixture,to control the construction quality,put forward the corresponding quality control indicators and requirements,using the dynamic stirring mixer instead of the traditional stirring mixer,which can effectively improve the mixing uniformity of the mixture.