Research On Pavement Surface Properties Based On The Internal Structure Parameters Of Asphalt Mixture

Asphalt mixture is a heterogeneous material that consists of multiple components including coarse aggregate,asphalt mortar and air voids.The distribution of internal phases of asphalt mixture has a certain correlation with the surface properties of pavement,but there are few researches about the correlation between the two.Meanwhile,the homogeneity of asphalt mixture is directly related to the pavement performance,but there is less research on the correlation between the two.Therefore,evaluating the internal structure of asphalt mixture accurately is the premise to analyze the relationship between the internal structure of asphalt mixture and the surface properties of pavement/the road performance.However,the methods of studying the internal structure of asphalt mixture using digital image processing technique vary greatly,and now has not been formed an objective and effective system for evaluating the internal structure of asphalt mixture yet.Considering the shortages of evaluation method for internal structure of asphalt mixture,the dissertation used the scanner to obtain the asphalt mixture section images,and then developed a 2 Dimension Image-based Internal Structure Analysis Method?2D-IISAM?.2D-IISAM first preprocessed the asphalt mixture digital image and used the equivalent ellipse short axis to characterize the aggregate particle size in the image.Meanwhile,the two dimensional percentage of aggregates retained in each sieve size?e.g.D_j=4.75,9.5,13.2,16mm?was calculated.Then the accuracy of image pre-processing was verified by comparing the“two dimensional percentage of aggregates retained in each sieve size”and the“actual percentage of aggregates retained in each sieve size”.Finally,combined with the IPP?Image Pro-plus?,the evaluation indexes which characterized the aggregate arrangement,the air voids distribution,the asphalt mortar distribution and the homogeneity of asphalt mixture were proposed,which can reflect the internal structure of asphalt mixture directly.In order to evaluate the effect of various factors on the internal structure of asphalt mixture and understand the distribution of internal phases?i.e.aggregate,air voids and mortar?systematically,the effects of compaction methods,aggregate geometry?i.e.aggregate shape,angularity and surface texture?,gradation types,asphalt contents on the internal structure parameters of asphalt mixture were studied.The shape,angularity and surface texture of coarse aggregate were evaluated by the Aggregate Geometric Characteristic Evaluation System?AGCES?developed by this dissertation,the fractal dimension D,the percentage passing through 4.75mm and the percentage passing through the key sieve size were used to characterize the gradation type,while the filler binder ratio was used to characterize asphalt content.According to the grey correlation theory,the grey relation entropy analysis method was proposed to estimate the influence degree of design parameters on the internal structure parameters of asphalt mixture.In order to establish the prediction models of pavement surface texture based on the internal structure parameters of asphalt mixture,the dissertation obtained the macro-texture level(i.e.L_TX,0.5-32)and micro-texture level(i.e.L_TX,0.13-0.5)of asphalt pavement using 2D-ITAM firstly.Then,the volume of air voids calculated by image?i.e.VV_c?and the sine of aggregate inclination?i.e.sin?_m?were introduced to characterize the distribution of air voids and coarse aggregates in asphalt mixture,while the area ratio of mortar?i.e._mR^A?and mortar thickness?i.e.T_m?were used to estimate the distribution of mortar in asphalt mixture.Then,the correlations between the VVc,sin?_m,mR^A,Tm and the macro-texture level LTX,0.5-32,the micro-texture level L_TX,0.13-0.5X,0.13-0.5 were analyzed.Finally,the models for predicting the surface texture of pavement based on the internal structure parameters of asphalt mixture were established by the Levenberg-Marquarat and generalized global optimization algorithm.In order to study the effect of the homogeneity on the pavement performance,the homogeneity of different types of asphalt mixture was studied by 2D-IISAM.At the same time,the skid resistance,high-temperature performance,low-temperature crack resistance and water stability of different types of asphalt mixture were performed.In order to describe the skid resistance of pavement under low-speed driving situations accurately,the friction coefficient of asphalt pavement was tested by Walking Friction Tester?WFT?developed by the Highway&Airport Pavement Research Center?HAPRC?.Based on the above discussions,the influence of homogeneity of asphalt mixture on the pavement skid resistance and conventional pavement performance was studied.Finally,the relationship between asphalt mixture homogeneity and pavement performance variability was established.