Experimental Study On The Effect Of Void Fraction On The Skid Resistance And Cooling Performance Of Porous Asphalt Pavement

With the rapid development of the highway construction in China,a fast and convenient traffic network has been formed.At the same time,how to improve road safety performance to reduce traffic accidents has become an important evaluation index of pavement design.The good skid resistance and cooling performance of porous asphalt pavement make it possible to improve the safety performance by adopting this pavement.But the performance of porous asphalt pavement is greatly influenced by the porosity.Therefore,experimental analysis and theoretical research were carried out in the paper,focusing on the influence of porosity on the skid resistance and cooling performance of porous asphalt pavement.The skid resistance performance of the pavement was evaluated by the surface friction coefficient,the texture depth and the critical speed as the water-skiing happened.The mathematical model between the surface friction coefficient and porosity of porous asphalt pavement was estabilished on the test results with pendulum friction meter.And the model between measured texture depth and porosity was obtained by the sand patch test.Besides,the CT images were used to correct the measured texture depth.Based on the correcting method,the relationship between the accurate depth value and the porosity and the relationship between the correction and the porosity were obtained.Moreover,the mathematical model of critical hydroplaning speed and porosity was obtained by the combination of seepage theory derivation and permeability coefficient test.The results indicated that when the porosity changed from 16.36% to 23.05%,the friction coefficient of porous asphalt pavement was 0.056-0.175 higher than AC pavement.And the texture depth was 0.024-0.083 cm deeper than AC pavement.Besides,the critical hydroplaning speed would increase as the porosity got greater.In addition,the convective heat transfer coefficients of the surface of different specimens under the same windy condition were determined by the simulated sunshine test and the virtual test by ANSYS Workbench.And the ABAQUS finite element was used to simulate the change of the temperature field internal the pavement of different forms in 24 hours.The results showed that the cooling performance of porous asphalt pavement would increase with the increase of the void ratio.When the upper layer porosity reached 23.05%,the cooling effect was best.The temperature in the depth of 0cm,4cm and 10 cm in the porous asphalt pavement was 5°C,5.49°C and 3.85°C lower than that in AC pavement.road.And the cooling performance of double-layered porous asphalt pavement was 4.46°C,4.76°C and 5.05°C in the same positions.Based on the study of the skid resistance and cooling performance of porous asphalt pavement,the law of their variation with porosity was obtained,which could provide reference for practical engineering.