The Angularity Characteristic And Description Method Of Aggregates

The weight of aggregate in the asphalt mixture accounts for about 90% of the total weight of the asphalt mixture,which determines the road performance of most of the asphalt mixture.The angular characteristics of the aggregate have the most significant impact on the physical properties of the mixture.Asphalt mixture has a direct impact on many other properties.But so far there is no unified standard in the academic community to characterize the angular characteristics of aggregates.The current mainstream angular measurement methods in the academic community are cumbersome and scientifically debatable.In order to design a higher quality asphalt mixture,a uniform and scientific characterization method of aggregate characteristics must be invented first,and then the eligible aggregates should be added to the asphalt mixture to be mixed in order to improve its road performance.With various indicators,it is important to study the characteristics of aggregate angularity.In order to express the angular characteristics of aggregates succinctly and efficiently,this paper mainly analyzes and calculates the index values of the two-dimensional digital images based on the study of the angular characteristics of aggregates in asphalt mixtures domestically and worldwidely.Using matlab as the main software to analysis the images which have been processed and the values of angular characters.Furthermore,a new value called angularity degree which is used to describe the level of angularity of the aggregates.The main research is carried on by selecting the coarse aggregate in the mixture and lay it on a plane with pure white background,and use a camera to take a top view of the plane under the natural sun light.Analyzing the images which are screened via matlab,conversion and data analysis and calculate the longest inner diameter,the area and perimeter of aggregate image and its minimum circumcircle,and also the centerline short axis.Finally can get these angular index values,such as the ratio of the centerline short axis to the longest inner diameter,area ratio,circularity and angularity degree.The Marshall test about single-gauge aggregates was conducted to find that the relative density of aggregate Marshall specimens from the same stockyard increased with the increase of the angularity degree.And shows a nonlinear function with theshort center axis to the longest inner diameter.However,it is not an obvious relation with the area ratio and the circularity.