Shape Characteristics Analysis Of Coarse Aggregate Based On Image Processing Technology And Its Application

Coarse aggregate has its own characteristics such as gradation and particle size distribution,particle shape and shape characteristics,and void ratio,all of which have an important impact on the performance of concrete.The shape characteristics of coarse aggregate affect its bulk density,which furthermore affects the meso and micro performance of concrete.The conventional detection and analysis methods of aggregate cannot fully reflect the shape characteristics of coarse aggregate,and cannot meet the needs of meso and micro level research of concrete materials.The conventional sieving methods cannot obtain the shape characteristics of coarse aggregate,so the traditional aggregate density calculation theories and methods cannot consider the shape characteristics of the aggregate.With the development of image information processing technology,it is possible to obtain all the shape characteristics.The use of image processing technology to obtain the shape characteristics of aggregates not only provides an efficient,convenient and intelligent detection method for aggregate property detection analysis,but also provides data support for the calculation of aggregate bulk density.Furthermore,it is of great significance to improve the performance of concrete.The main content of this paper includes:(1)The general theories and methods of 2D and 3D image processing technology and their application to the analysis of aggregate particle shape are analyzed and summarized.The progress of the calculation theories and methods of particle packing density are summarized and discussed,and the impact of coarse aggregate bulk density on concrete performance is analyzed.The feasibility,the technical route,and the key issues to be solved are determined.(2)The two-dimensional image analysis reconstruction theories and its methods were applied to construct the 2D image acquisition and processing analysis systems.Through the edge information obtained by image analysis,the shape parameters of aggregate are determined and analyzed by using the equivalent ellipse method.Based on the theoretical research,2D image acquisition and processing analysis software was developed.Comparative analysis and research show that the error of the detection and calculation results is small.Compared with the conventional sieving method,the maximum error of the grading is 5.52%.Compared with the gauge method and vernier caliper method,the error of needle and flake particles are 2.54% and 6.88%,respectively.(3)Aiming at the problem caused by the lack of three-dimensional information in twodimensional analysis,the multi-view stereo vision three-dimensional reconstruction theories and its methods were applied to construct the 3D image acquisition and processing analysis systems.The multi-dimensional stereo vision technology is used to extract the threedimensional information of the aggregate from multiple angles,and the three-dimensional shape parameters are obtained and analyzed by using three-dimensional reconstruction method.Comparative analysis and research show that the accuracy is further improved.The maximum error of grading has been reduced from 5.52% to 3.95%,the error of the needle and flake particle content test has been reduced from 2.54% to 1.97%(gauge method),6.88% to 2.93%(vernier caliper method).(4)Based on the two-dimensional and three-dimensional detection analysis and system construction,the four-point perspective transformation theory and the OpenCV image library are used to create a mobile app of image processing for concrete aggregates image processing and quality analysis on Android OS,and construct a mobile intelligent detection and analysis system.Comparative analysis and research show that the accuracy of the detection and calculation results of the app is high.Compared with the conventional sieving method and the 2D and 3D fixed-camera testing method,the test results of the method have high coincidence degree.The test precision can meet the requirements of the practical application.(5)The bulk density of the aggregate affects the performance of concrete mixtures and hardened concrete.Improving the bulk density and reducing the void ratio of aggregate is of great significance for improving the performance of the concrete.The calculation theories and methods of the aggregate bulk density have important guiding significance for the optimization of aggregate gradation and concrete mix proportion design.Using the shape parameters obtained and analyzed by image analysis processing system,a calculation method of bulk density based on the shape characteristics of aggregate was proposed.It makes up for the defects of the existing calculation models of particle packing density,such as FURNAS model,TOUFAR model,and CPM model,etc.,which do not consider the true particle size distribution and shape characteristics of aggregate particles.The two-dimensional packing simulation of aggregate and the results of bulk density calculation by using this method show that the calculation accuracy is high.Compared with the conventional detection method,the maximum error is only 0.96%.