Design And Performance Evaluation Of Anti Freezing Permeable Asphalt Pavement

There is a lot of rainfall and humidity in Southwest China.Under the condition of heavy rainfall in summer,asphalt pavement is easy to accumulate a lot of water,and it is easy to appear freezing in the cold climate in winter.Permeable asphalt pavement has good water permeability and drainage functions,anti freezing asphalt pavement has the ability to reduce freezing point and delay pavement icing,but the single function permeable pavement or anti freezing pavement can not meet the actual needs.Therefore,in this paper,the design and performance evaluation of anti freezing permeable asphalt pavement are carried out based on the climate characteristics and traffic conditions in Guizhou,the research is carried out from the following aspects: the demand of pavement permeability and anti freezing,the combination design of permeable pavement structure,the composition design and permeability of permeable asphalt mixture,the composition design and performance influencing factors of anti freezing permeable asphalt mixture,and the long-term anti freezing performance of anti freezing permeable asphalt pavement.The main conclusions are as follows.(1)Based on the multi-year climate database,this paper investigates the climate characteristics and the demand of pavement water permeability and anti freezing ice in Guizhou Province,establishes a logistic model for pavement freezing prediction,and analyzes the significance of meteorological factors of road freezing,which is as follows: daily temperature >relative humidity > average wind speed > sunshine hours.(2)Taking the average rainfall intensity within 30 minutes of the peak rainfall intensity as the index,this paper analyzes the rain pattern characteristics of Northwest Guizhou,Southwest Guizhou,Central Guizhou and East Guizhou,and puts forward the requirements of pavement permeability function(the thickness of permeable layer is greater than or equal to 100 mm)for representative projects,and then determines the pavement structure with good permeability function and road performance combined with rainfall characteristics and traffic load conditions Combination scheme: PAC13+PAC20+AC25C.(3)Three kinds of high viscosity modifiers and two grades were selected to prepare macroporous permeable asphalt mixture.The connectivity porosity and permeability coefficient of permeable asphalt mixture were tested by using the self-developed permeability coefficient test device.The water permeability difference between single permeable and double permeable asphalt pavement was compared and analyzed.The results show that the water permeability basically remains unchanged with increasing the thickness of permeable layer,but can be improved Increasing the thickness of the reservoir is more suitable for the climatic conditions and rainfall characteristics in Guizhou.(4)The physical and chemical properties of powdery and granular anti freezing agents are compared and analyzed.The composition design of anti freezing permeable asphalt mixture is carried out with permeable asphalt mixture as the matrix.The optimal dosage of powdery anti freezing agent is determined to replace 80% mineral powder,and the optimal dosage of granular anti freezing agent is 5% when it is directly added to asphalt mixture;This paper analyzes the influence of different types of anti freezing agent precipitation on the pavement performance of permeable asphalt mixture,and the results show that the granular anti freezing technology is more suitable for the climate and rainfall characteristics of Guizhou area.The anti freezing performance of pavement is evaluated by silver nitrate titration method,interlayer adhesion test method and ice melting test,and the results show that the granular anti freezing permeable asphalt pavement has good performance.(5)Using the self-developed anti-ice-permeable asphalt mixture scouring device,the conductivity of the aqueous solution after the precipitation of the anti-coagulant is used as an indicator to compare and analyze PAC13+anti-coagulation AC20,anti-coagulation PAC13+AC20,PAC13+anti-coagulation PAC20,Anti-coagulation PAC13+PAC20 and other four combination schemes have long-term anti-coagulation performance,The results show that:with the increase of the number of scouring and rolling cycles,the precipitation amount of anticoagulant increases gradually.When the anti freezing agent is added into the upper asphalt mixture,the scouring effect is more intense.When the anti freezing agent is added into the lower asphalt mixture,the anti freezing agent is not easy to be released,which affects the anti freezing function.After comprehensive consideration,the pavement structure is finally determined as PAC13+anti-coagulation PAC20.In conclusion,the anti freezing permeable asphalt pavement proposed in this paper has dual functions of drainage in rainy season and anti freezing in winter,and has good durability.The research results have important reference value for the construction and safe operation of asphalt pavement in Southwest China.