Investigation On Seepage Behavior In Asphalt Mixture Based On Micro-scale Air Void Morphology Genic Library

The investigation of pore water transition and distribution in asphalt mixture is the key to understand the moisture damage behavior in pavements.The ambient water percolated into the asphalt mixture mainly based on micro-scale air voids.The macroscale water seepage characteristics in asphalt mixture has been widely studied.However,these studies ignored the water heterogeneity distribution and irregular transportation in air void complex structures and failed to describe the micro-scale seepage behavior in asphalt mixture.And this shortage resulted the difficulty for proposing solution of moisture damage in asphalt pavements.Hence,the evaluation of micro-scale air void characteristics and investigation of seepage behavior in micro-scale air void is very important to understand the mass transfer characteristics in asphalt mixture.It contributed to the study of moisture damage mechanism under water percolation.This study based on X-ray computed tomography(CT)technique and digital image processing method,discussed the pores morphology characteristics in asphalt mixture.The typical structural units in air void structures were defined and distinguished.The air void morphology genic library was constructed based on statistical method.In addition,the impact of air void morphology genic characteristics on micro-scale seepage behavior in asphalt mixture was studied.The main contents and results are as below.Firstly,based on the 3D air void model extracted from asphalt mixture and digital image analysis method,the air void morphology characteristics evaluation method was proposed.This method was optimized by accuracy analysis under varied slice pictures spacing and pixel size.Under the optimized calculation condition,the impact of compaction method and asphalt mixture type on air void micro-scale volume and morphology character was investigated.Secondly,based on the rule of material gene expression,the air void morphology trait under varied volume was analyzed.Based on the typical difference among air void morphology traits,the air void typical structure units were defined.The distribution of air void morphology indexes under varied typical structure units was analyzed and the rule of typical structure units distinguishing was proposed.The air void morphology genic characteristics was investigated under varied compaction conditions and asphalt mixture types.At last,the genic library of air void morphology was constructed based on statistical method.Next,the air void geometry model with morphology genic characteristics was designed.With this geometry model,utilized finite element method(FAM),the seepage simulation model was constructed under a saturated constant pressure seepage condition.This model was verified based on computational fluid dynamics method(CFDM)and the calculation results of a simplified air void model.At last,the impact of air void surface appearance on seepage behavior near air void wall was analyzed.And then the micro-scale seepage characteristics in air void typical structure units with varied morphology genic traits was investigated.In addition,the real air void geometry model was constructed and the typical structure units were distinguished.Based on this model,the seepage behavior under typical structure units random combination was studied.And the micro-scale seepage behavior in asphalt mixture air void was described.This result of this study contributes the moisture damage mechanism study and mass transfer behavior study in asphalt mixtures.