Abstract

It is important to study the failure mechanism of concrete by observing the crack expansion and capturing key structures at the mesoscale. This manuscript proposed a method for efficiently identifying aggregate boundary information by X-ray computed tomography technology (CT) and a discrete element modeling method (DEM) for equivalent random polygon aggregates. This method overcomes the shortcomings of the Grain Based Model (GBM) which is impossible to establish a mesoscopic model with a large difference in grain radius. Through the above two methods, the CT slice images were processed in batches, and the numbers of edges, axial length, elongation of the aggregate were identified. The feasibility of the method was verified by the comparison between experimental and simulating results. Three mesoscopic models for different porosities were established. Based on aggregate statistics, this manuscript achieved the meso-model recovery to the maximum extent. The test results show that the crack appeared at the tip of the aggregate firstly, and then the broken boundary was applied in the direction of the applied load and around the pores. Finally, the crack was selectively expanded under the axial force. During the loading process, the minor principal stress was normally distributed. As the porosity and loading time increased, the heterogeneity increased.

Highlights

  • The grain-scale microstructure controlled the micromechanical behavior and governed the complex macroscopic response [1]

  • This paper has aimed to generate a 2D model regarding the probability and statistics method, and to analyze the micro-crack propagation law at the mesoscale. This manuscript proposed a method for efficiently identifying aggregate boundary information in computed tomography technology (CT) images and discrete element modeling method (DEM) method for equivalent random polygon aggregates. This method overcomes the shortcomings of Grain Based Model (GBM) which is impossible to establish a mesoscopic model with a large difference in grain radius

  • This method overcame the shortcomings of the traditional GBM method, which is program

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Summary

Introduction

The grain-scale microstructure controlled the micromechanical behavior and governed the complex macroscopic response [1]. It is well-known that the heterogeneity (mortar, aggregate and the interfacial transition zone) plays a key role in the generation of localized tensile stress, which further results in crack initiation. I.e., between the microscopic scale and the macroscopic scale (10−6 m–10−0 m), the interfacial transition zone (ITZ) between mortar and aggregate is the weak part of concrete, which determines the concrete strength. It is necessary to study the macroscopic failure mechanism and characteristics of strength and deformation of concrete at the mesoscale.

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