Study On The Evaluation Method Of Coarse Aggregate Angularity And Its Influence On The Road Performance Of Asphalt Mixture

With the rapid development of highway construction in China and the continuous improvement of people's requirements for environmental protection,the large demand for stone materials and the increasingly shortage of stone resources have become one of the main contradictions in the development of highway transportation in China.Therefore,studying the aggregate properties and its influence on the road performance of asphalt mixture is of great significance for improving the utilization efficiency of stone materials,saving and protecting limited stone resources,and improving the design methods of asphalt mixtures.This study will be 4.75~16mm of coarse aggregate in the Losangeles abrasion tester respectively wear 0,400,800,1200 revolutions,forming four kinds of coarse aggregate angularity.Using the digital image processing technology and the convex hull algorithm in computational geometry,the evaluation index CHA of coarse aggrgate angularity is proposed.At the same time,using the American aggregate image measurement system(AIMS?),the rationality of the convex hull method to evaluate the coarse aggregate angularity is verified,and the influence of particle size and wear revolutions on the coarse aggregate angularity is analyzed.It is found that the increase of the wear revolution will result in a decline in the coarse aggregate angularity,and in the 4.75~16mm aggregate,the 13.2~16mm coarse aggregate angularity is the most abundant.Through a large number of laboratory tests,the effects of coarse aggregate angularity on the Marshall index,high temperature stability,low temperature performance,water stability and skid resistance of asphalt mixture are analyzed.The analysis results show that the increase of the coarse aggregate angularity will result in the increase of the VV,VMA,MS,the dynamic stability,the uniaxial penetration strength,the flexural strain,the splitting strength,the surface structure depth and the friction coefficient,and the decrease of the bulk density,the VFA,the FL,the bending strength,the residual stability,the freeze-thaw splitting ratio.With the increase of coarse aggregate angularity,the high temperature resistance to rutting,low temperature crack resistance and skid resistance of asphalt mixture increased,and the ability to resist water damage gradually weakened.