Research On Optimization Of Mixture Ratio Of Ultra-thin Wearing Layer And Construction Technology

The rapid growth of China’s national automobile ownership has been continuously increased the pressure on traffic loads,resulting in a rapid decline in the surface function of different grades of asphalt pavements~[1].At the same time,different degrees of disease have appeared on the pavement,so the preventive maintenance of high-grade highways is imminent.However,traditional road maintenance has shortcomings such as long construction time,high cost and poor quality.The ultra-thin wear layer is a skeleton-embedded asphalt concrete structural layer with a thickness of 1.5cm to 2.5cm.During construction,the emulsified asphalt spraying and hot asphalt mixture paving are carried out at the same time~[2],and the pavement can be formed at one time.The principle is that the hot mixture causes the moisture of the emulsified asphalt to evaporate,prompting its rapid,ademulsificationnd quickly forming a very strong oil film between the old and new structural layers.This surface layer has the advantages of ultra-long durability,anti-skid,reduced noise,reduced water mist,anti-rutting and low cost~[3].Therefore,it is of great practical significance to carry out the engineering application research of ultra-thin wear layer in different regions.This paper takes NovaChip C-graded asphalt mixture as the research object,and conducts research and analysis on raw material selection,mix ratio design,and road performance of the mixture.According to the research results of the characteristics of ultra-thin wear layer grading,the production technology of intermittent asphalt mixing plant and the three high-viscosity modified asphalts with different properties adapted to southern climate conditions,the best quality and the most suitable combination of the actual construction conditions between the target mix ratio and the modified asphalt are selected.The physical engineering proves that all road performance indicators of this combination type meet the requirements.The main research results obtained in the physical engineering experiment are as follows.(1)The mechanical properties of the raw materials(aggregate and asphalt cementing materials)were tested according to the road performance requirements of the ultra-thin wear layer.First,three groups of modified asphalts with different properties were selected for testing.At the same time,in order to fully study the influence of different gradations and different asphalt cementitious material combinations on the mixture,it is proposed that the needle flake shape of the coarse aggregate should not exceed 5%and the maximum particle size of 16mm sieve pass rate must reach 100%.(2)Secondly,based on actual demand,the aggregate amount of 2.36mm-4.75mm was increased,and the 2.36mm screen was determined as the key sieve hole of NovaChip C asphalt mixture.Within the grading range required by the specification,through the study of the relationship between the key sieve pass rate and the void ratio of the asphalt mixture,four sets of target gradations were initially formulated,and the gradation program.of different types of asphalt cementing materials was formulated.Program In addition,through Marshall,leakage and scattering tests,the mechanical performance indexes such as the best bitumen-stone ratio and stability of each group of asphalt mixtures with different grading schemes were determined.After repeated comparison and analysis,the relationship among the key sieve hole change,the void ratio of the mixture and the best oil-stone ratio and the asphalt film was obtained.(3)Third,the high temperature stability,low temperature crack resistance,water stability and anti-skid performance tests of asphalt mixtures with different gradations were carried out.And according to the comparative analysis of the advantages and disadvantages of different gradation asphalt mixtures,the optimal gradation was screened out.(4)Last but not least,the best graded asphalt mixture was applied to the Furong Avenue(Xiangtan Section)rapid pavement reconstruction project,and simultaneous construction technology was used.After the construction was completed,all indicators can meet the technical requirements of the wearing layer.Finally,the cost of control in the actual construction process according to the optimal plan was calculated through the theoretical calculations.