Performance Improvement Study Of Permeable Asphalt Pavement Used On Urban Road

The permeable asphalt pavement structure has been widely used because of its excellent performance on the functions of drainage,antiskid and noise reduction.Because of the widespread use of impermeable dense-graded pavement,urban road has caused the urban heat island effect and rain Island effect seriously,and the ecological environment of the city has been seriously destroyed.In the construction of Sponge city,the paving of permeable asphalt pavement has gradually become a trend.However,there are some diseases such as the loss of function,the loose of mixture,the scour of water on the asphalt pavement of urban paving.This paper aims to improve the performance of urban road permeable asphalt pavement,in this paper,the influence of the pass rate and coarse aggregate properties of the key sieve holes on the road performance of pervious asphalt pavement is studied by the method of indoor mechanical property test,and through the indoor test results,the key sieve hole pass rate is constructed by the analytic hierarchy process.The weight of aggregate spherical factor on the road performance of permeable asphalt pavement mixture is weighted,which provides guidance for the design of pavement performance improvement of urban road permeable asphalt road.Firstly,based on the characteristics and main diseases of the permeable asphalt pavement of urban road,the current design method of mix ratio was analyzed;laboratory test scheme and gradation scheme for controlling single variable were designed;the properties of aggregates used in laboratory tests was determined and 70# matrix asphalt adding TPS high viscosity modifier was used as asphalt binder;by scattering tests it was determined that the minimum scattering loss of TPS high viscosity modifier reached when its content was 13%;then through leakage test and scattering tests to determine the optimal asphalt content and modify the thickness of asphalt film in the empirical formula.Secondly,in order to study the influence of each pass rate of the key sieve holes in the gradation on the road performance of the mixture,on the premise of controlling a single variable to change the passage rate of the key sieve hole of 9.5mm,4.75 mm,2.36 mm and 1.18 mm,for 9 groups of graduation mixtures to conduct uniaxial penetration test,immersion Marshall test and freeze-thaw splitting test.The test results showed that the median gradation had higher shear strength;each pass rate of sieve hole was a good linear correlation with the residual stability;2.36 mm sieve hole pass rate had the greatest influence on residual stability and residual splitting strength but its influence trend was opposite;2.36 mm sieve hole pass rate had the biggest influence on the void ratio of the mixed material and the particle size of 4.75 mm ~ 9.5mm was the key grain size aggregate forming the skeleton void.Thirdly,the influence of aggregate morphology on the road performance of the mixture was explored.The X-ray CT scanning technique was used to analyze the morphology of the two aggregates that the difference of fractal dimension of the two aggregates was small,but the spherical degree was obviously different.Results of laboratory test on road performance of two kinds of aggregated mixture specimens with the same gradation showed that porosity ratio,shear strength,residual stability and residual splitting strength of the mixture increased greatly with the increase of aggregate sphericity,but with the increase of porosity,the Marshall stability and splitting strength decreased slightly with the increase of aggregate sphericity.Finally,take the design guidance of improvement of road performance of permeable asphalt pavement as the object,with laboratory test results to comprehensively analyze the influence of gradation variation and aggregate morphology on the mixture performance,with analytic hierarchy process as an analytical tool,after the establishment of the analytic hierarchy process model,according to the results of laboratory test to determine the weight matrix of the scheme layer to the criterion layer.Based on the analysis of the typical disease of the permeable asphalt pavement of the urban road,the judgment matrix of the criterion layer to the target layer was established.The influence weight of key sieve pass rate and coarse aggregate globality on road performance of permeable asphalt pavement was obtained by systematic calculation and its weight was: pass rate of 2.36 mm sieve hole > globality of coarse aggregate > pass rate of 4.75 mm sieve hole > pass rate of 1.18 mm sieve hole > 9.5mm sieve hole pass rate.