Study On Permeability And Microstructure Of Porous Asphalt Mixture

The large-void asphalt mixture is gradually promoted and applied in road engineering with its good surface functional properties.The rain-water safety provided by good water permeability is the main performance of excellent surface functional characteristics.In order to grasp the penetration mechanism of the drainage asphalt mixture,it is necessary to study The effect of void parameters on its permeability.This paper fully considers the various factors affecting the permeability coefficient in the actual pavement conditions.The internal factors include the change of 2.36 mm key mesh passage rate and the incorporation of polyester fiber.The external factors include the surface blockage simulation of the mixture and the change of compaction degree.The infiltration characteristics of each test piece under different factors were tested by self-made test vertical and horizontal permeability coefficient integrated water seepage device,and the internal observation of large void asphalt mixture under different factors was analyzed by CT non-damage scanning technology.The structure is distributed,and then the correlation between the macroscopic and mesoscale parameters and the permeability coefficient is analyzed.Firstly,the variation of the permeability characteristics of large-void asphalt mixture under different factors was studied by using a self-made water seepage instrument.Studies have shown that reducing the amount of fine aggregates will increase the void ratio of the large void asphalt mixture to improve the permeability;the polyester fiber reduces the void ratio and the connected void ratio in the large void asphalt mixture;the plugging essence of the large void asphalt mixture The upper part is caused by the residue of the plug in the void.The plugging agent mainly affects the permeability coefficient of the seepage direction;the change of the degree of compaction has a greater influence on the connected void ratio,and the underpressure will significantly increase the permeability characteristic,and the overpressure will be slightly Reduce its permeability characteristics.Then,CT damage-free scanning technology and digital image processing software were used to analyze the influence of different factors on the internal meso-gap structure of large-void asphalt mixture.The research shows that the coarse-grain asphalt mixture is mixed with the finegrained aggregate.The vertical and horizontal gap gradation of the material is also finely thickened;after the polyester fiber is blended,the void ratio of the test piece is reduced and the vertical and lateral gap gradation curves are tapered;the test piece after the clogging test The vertical and horizontal gap gradation curves will be thicker than the original test piece gap grading curve;under different degrees of compaction,the vertical and lateral scanning of the overcompressed test piece has a finer gradation,and the under-compacted test piece The void gradation is coarser;under different freezing and thawing cycles,the vertical and horizontal scanning shows that the void gradation changes of the specimen after freezing and heat treatment conditions are obvious;the Weibull distribution model is in the void equivalent diameter of the large void asphalt mixture.The distribution distribution has a good fitting effect,and the lognormal distribution model can better simulate the distribution of the void equivalent diameter distribution spectrum.The fractal dimension of the void contour can show the vertical direction and the test piece to a certain extent.The complexity of the voids.Finally,the correlation between the permeability characteristics of macrovoid asphalt mixture and macroscopic and mesoscopic parameters under different factors was studied.Based on the gray correlation analysis and the rough set attribute reduction theory,the parameters in the void equivalent diameter distribution spectrum and the correlation between the fractal dimension of the void contour and the permeability coefficient are analyzed.The results show that the correlation between the macroscopic void parameters and the permeability coefficient is good;the area ratio at the boundary between the coarse and small voids,the area ratio at the smallest particle size and the two-way permeability coefficient are well correlated;The 7mm~8mm)group has the greatest influence on the vertical permeability coefficient,and the(12mm~13mm)group has the least influence on the vertical permeability coefficient;the(2mm~3mm)group has the greatest influence on the horizontal permeability coefficient(11mm~)The 12mm)group has the least influence on the transverse permeability coefficient;based on the rough set theory and the Rosetta software platform,the key groups affecting the vertical permeability coefficient are {A2(1mm~2mm),A4(3mm~4mm),A7(6mm ~7mm)},the key groups affecting the transverse permeability coefficient are {B2(1mm~2mm),B3(2mm~3mm),B9(8mm~9mm)};the transverse void contour fractal dimension of each test piece under different factors The number is larger than the vertical fractal dimension,and the void distribution of the transverse test piece is more complex than the vertical distribution.There is no obvious correlation between the fractal dimension of the void profile and the permeability coefficient.