Determination of Fracture Properties of Concrete Using Size and Boundary Effect Models

Abstract

Tensile strength and fracture toughness are two essential material parameters for the study of concrete fracture. The experimental procedures to measure these two fracture parameters might be complicated due to their dependence on the specimen size or test method. Alternatively, based on the fracture test results only, size and boundary effect models can determine both parameters simultaneously. In this study, different versions of boundary effect models developed by Hu et al. were summarized, and a modified Hu-Guan’s boundary effect model with a more appropriate equivalent crack length definition is proposed. The proposed model can correctly combine the contributions of material strength and linear elastic fracture mechanics on the failure of concrete material with any maximum aggregate size. Another size and boundary model developed based on the local energy concept is also introduced, and its capability to predict the fracture parameters from the fracture test results of wedge-splitting and compact tension specimens is first validated. In addition, the classical Bažant’s Type 2 size effect law is transformed to its boundary effect shape with the same equivalent crack length as Koval-Gao’s size and boundary effect model. This improvement could extend the applicability of the model to infer the material parameters from the test results of different types of specimens, including the geometrically similar specimens with constant crack-length-to-height ratios and specimens with different initial crack-length-to-height ratios. The test results of different types of specimens are adopted to verify the applicability of different size and boundary effect models for the determination of fracture toughness and tensile strength of concrete material. The quality of the extrapolated fracture parameters of the different models are compared and discussed in detail, and the corresponding recommendations for predicting the fracture parameters for dam concrete are proposed.

Fatigue Deformation and Energy Change of Single-Joint Sandstone After Freeze-Thaw Cycles and Cyclic Loadings

“…Until now, few experimental studies have comprehensively investigated the F-T damage and loading-unloading fatigue fracture of fractured rocks. However, some previous studies on the fatigue fracture of concrete and rock under the combined action of environmental factors and periodic loadings provide some valuable information (Sun et al, 1999;Jang et al, 2014;Lei et al, 2018;Gao et al, 2019;Tan et al, 2019;Zhao Y. et al, 2019). Therefore, this work used single-joint quasi-sandstone samples with joint angles of 45 • and 90 • , and the fatigue damage of fractured sandstone was studied experimentally under F-T cycles and periodic loadings.…”

Special Issue on Fatigue and Fracture of Non-Metallic Materials and Structures

“…Different approaches have been used, including experimental investigations, theoretical models, and numerical simulations. Papers [1][2][3][4][5] are related to concrete material, from papers [6][7][8][9][10][11][12] to rocks. Other contributions investigate the fracture behavior of functionally graded materials [13], glass [14], laminate composites [15], refractories [16], and soft matter [17].…”

Investigation of granite fracture under three-point bending using the meso-modeling approach considering the random distribution of poly-crystals

“…Although much work so far has focused on the failure process of rock, and many fracture models are proposed to describe this process (Gao et al 2019;Li et al 2016), a unified method is still needed to simulate the mechanical behavior and deformation characteristics of rock under different loads. A modeling method based on random distribution has been well applied in studying concrete meso-structure (Fang et al 2017;Zhang et al 2012).…”