Composition Design And Function Evaluation For Materials And Structures Of Permeable Asphalt Pavement

At present,majority of highway and square are impermeable pavement structure.Rainfall should be discharged by urban sewerage and drainage system,which will aggravate drainage system's burden.And rainstorms easily bring waterlogging disaster.Besides that,dense pavements make permeated rainfall substantially reduced,groundwater can't obtain supplement,and then ground subsidence is formed.To promote the coordination between pavement and environment as well as sustainable development,to create harmonious living environment,and to improve urban roads' single pavement structure form,this paper researched on permeable asphalt pavement for material fabric and structure function.Permeable asphalt concrete's micro-pore structure directly affected mixture's permeability performance.Described and analyzed PAC's micro-pore characteristics by means of X-ray computed tomography scanning technology,the results revealed the influence law from macroscopic material composition on micro-pore characteristics,and established transformation model among air voids,connected air voids and permeability coefficient,the air voids prediction model was also generated simultaneously.Used pore plugging test to evaluate mixture's anti-clogging performance,and explained the mixture's blocking reason combining with micro-pore characteristics,finally put forward mitigation measures.The paper optimized PAC's material composition design method.During the gradation design,the virtual test results based on discrete element method proposed a new concept about coarse aggregate roughness,then analyzed the relationship between roughness and mixture's performance,afterwards recommended PAC's gradation range.In addition,suggested a new optimum asphalt content determining method,which make 15%scattering loss and 0.3%drain-down loss as control standard.This new method even provided a specific calculation formula for optimum asphalt content.After verification,we found the new method can fix a reasonable asphalt content more simply and objectively.Evaluated PAC's high temperature performance,water stability,low temperature performance,fatigue performance as well as thermal physical characteristics,and compared them with dense-graded asphalt mixture's relevant performances.The test results of Hamburg Wheel Tracking in water showed PAC with reasonable material composition design own excellent water and high temperature stability.Fatigue test results revealed,with the increase of air voids,PAC's fatigue performance weakened,and the fatigue life became more sensitive to stress level's change,but if the asphalt-aggregate ratio is reasonable,3 to 10 days soaking can't significantly decreased PAC's fatigue life.Both of PAC's thermal physical indexes and laboratory simulation test results demonstrated PAC possessed better thermal resistance,who can prevent and delay road's heat transmission from surface to interior in hot season.According to PAC's materials properties and applicable situation,put forward three types permeable asphalt pavements,and designed drainage system for every pavement.On the basis of permeable pavement's structure selection and pavement layers combination state's research,the author chose appropriate pavement structure design specifications,and adopted mixture's compression modulus after soaking or freeze-thaw cycle to do permeable pavement's structure design,finally combining with mechanical analysis,recommended typical structure and reasonable structure layer thickness in different traffic conditions for every type permeable asphalt pavement.Every structure layer thickness of permeable asphalt pavement must be not only satisfy bearing ability,but also fulfill functional requirements as permeable,drainage,water storage and so on.Therefore,the paper studied rainfall's flow process in permeable asphalt pavement,also analyzed rainfall parameters and rainfall process,on this basis,established three types permeable asphalt pavements' permeable models and evaluation systems combining with water adhesive rate,connected air voids and permeability coefficient.