With the decrease of natural aggregates,in order to meet engineering needs,aggregates have gradually become the main source of sand and gravel resources.However,there are still some problems in the current research on machine-made aggregates:on the one hand,the current aggregate evaluation standard method is too single,and the quality inspection of machine-made aggregates is relatively loose,resulting in poor grain shape and substandard production of machine-made aggregate;On the other hand,as one of the most important physical characteristics of aggregate,the influence of aggregate morphology on the mechanical properties of concrete cannot be ignored.Most of the existing studies are only qualitative analysis.Therefore,a systematic study of aggregate morphology can effectively solve the above-mentioned problems.In this paper,based on digital image processing technology(DIP technology),three aggregate profile parameters and three angularity parameters are selected to quantitatively characterize the morphological characteristics of the aggregate;then the aggregate morphology recognition and feature parameter acquisition are written in Python language The program performed statistical analysis and experimental verification of these quantitative parameters;finally,a concrete simulation model was established at the meso-scale,and the influence of aggregates on the meso-mechanical properties of concrete was analyzed.This article has the following conclusions:(1)The DIP technology can be used to quickly identify the morphological characteristics of coarse aggregates.Parameters such as elongation,sphericity,roundness and angularity can be used to quantitatively characterize the morphological characteristics of coarse aggregates;the compiled aggregate morphology recognition The program can not only obtain the characteristic parameters of the coarse aggregate,but also obtain the gradation curve of the measured aggregate.(2)From the statistical results of the characteristic parameters of the coarse aggregate,it is found that the angle and sphericity of the aggregate are in accordance with the normal distribution,and the other parameters are in the partial normal distribution;the particle size will affect the distribution of the elongation and flat elongation of the aggregate.But it has little effect on other characteristic parameters.(3)The correlation test of the profile parameters,the angularity parameters and the loose accumulation void ratio found that the pairwise combination of the convexity and the profile parameters can describe the angularity and profile characteristics of the aggregates without affecting each other;the characteristic parameters of the aggregates are different from each other.The loose bulk porosity of coarse aggregates has a certain correlation,but the correlation between convexity and porosity is the highest R~2=0.9243.Convexity can be used to evaluate the loose bulk porosity of coarse aggregates.(4)Based on the Monte Carlo random number method,a random aggregate model in a two-dimensional state was established.The meso-level simulation of the model found that the peak stress of the concrete specimen will increase with the increase of the aggregate size,and the mortar and interface The smaller the elastic modulus of the transition zone unit,the easier it is for the specimen to crack;the spatial position and shape of the aggregate will not have a significant impact on the macroscopic mechanical properties of the specimen,but it will cause the change of the internal crack formation and location of the specimen. |