Research On Influence Of Coarse Aggregate Distribution Morphology On Fatigue Performance Of Asphalt Mixture

During the use of the established asphalt pavement,there are some asphalt pavement that are damaged due to temperature and repeated load,that is,fatigue breakage.With the development and improvement of asphalt pavement design and construction,the fatigue performance of pavement is gradually used as the basic standard for evaluating road performance in the industry,so it is more and more important to study the generation mechanism and response methods of fatigue damage.At the same time,coarse aggregate as the main material of asphalt mixture,it is also of great value to study the characteristic properties of coarse aggregate and the fatigue performance of asphalt mixture.At present,there have been many studies on the fatigue properties of asphalt mixtures and the meso-characteristics of coarse aggregates,but there has not been a comprehensive study that combines macroscopic morphology,meso-characteristics and fatigue performance.In view of the above research needs,this paper combines the indirect tensile fatigue test in the laboratory to obtain the fatigue life of asphalt mixture specimens made of coarse aggregates that have been extracted by digital image processing technology and mesoscopic characteristic parameters that have been statistically quantified.Image processing technology and discrete element software reconstructed a virtual two-dimensional specimen with realistic coarse aggregate meso-characteristic parameters,and then conducted indirect tensile fatigue test simulation to analyze the coarse aggregate meso-features in the specimen to asphalt mix Material fatigue performance.The comparison between the macro test and the meso-simulation test reveals the influence of coarse aggregate distribution morphology on the fatigue performance of asphalt mixture,which has great theoretical value and application prospects.In this study,the AC-13 asphalt mixture specimen was used as the follow-up research object.After determining the ratio,the coarse aggregate particles of a certain composition were weighed to perform 0,250,500,750,and 1000 rotations respectively.Abrasion test,and use the MATLAB image processing technology to program the extraction and calculation of the angular parameters.The Marshall specimens were prepared from coarse aggregates after the parameters were extracted for the split experiment.The results showed that the angularity produced by the abrasion test had a relatively obvious change in the split strength of the specimen group,so it laid the foundation for subsequent experiments.In this study,a method for converting a three-dimensional quality gradation into a two-dimensional quantity gradation was designed.According to this method,the coarse aggregates with collected feature information were randomly placed using MATLAB programming methods to generate a two-dimensional cross-section of the specimen.PFC2 D series of interactive methods reconstructed two-dimensional virtual specimens in discrete element software.Afterwards,the reconstructed specimens were subjected to indirect tensile virtual fatigue test.The results show that no matter under the same stress ratio or the same stress,the fatigue life of the test specimen has a peak in the gradient of angularity change.Therefore,when the angularity is low,the coarse aggregate inside the mixture is analyzed.The skeleton structure cannot be formed.When the stress increases to a small limit,the internal stress is basically borne by the asphalt mortar.Therefore,the meso-phenomenon of the phenomenon is that there will be more branch cracks during loading;with the formation of the skeleton,Fatigue performance has improved;but as the angularity continues to increase,the angularity of the coarse aggregate is more abundant.At the corners of the coarse aggregates,there will be more obvious stress concentration,which causes the coarse aggregates to puncture the asphalt film and form cracks,which eventually reduces the fatigue performance again.The analysis results show that the angular parameters of the peak fatigue performance are 110,000 to130,000 between.In the gradient change of the contact pair parameters,the fatigue performance of the specimen has a positive correlation with the meso-contact state.It is analyzed that due to the increase of the contact pair,a more stable skeleton structure is formed inside the asphalt mixture,thereby fatigue Improved performanceThrough the discrete element virtual experiment,the influence of coarse aggregate distribution on the fatigue performance of asphalt mixture was preliminarily revealed,and the correlation between the angular parameter L of coarse aggregate and the contact parameter J and the parameter K in the stress fatigue equation was studied.The optimization of the stress-fatigue equation is achieved.In order to compare with the mesoscopic virtual experiment,the coarse aggregates with mesoscopic parameters extracted were subsequently prepared into Marshall specimens,and the indirect pull-up fatigue test was designed and completed.The fatigue life of the macro experiments is relatively large,but the The fatigue life under the parameter gradient of angular gradient and contact basically satisfies the law of virtual experiment.Therefore,it is considered that the distribution of coarse aggregates has the above rules for the fatigue performance of asphalt mixture.