Abstract
The fracture performance of concrete is size-dependent within a certain size range. A four-phase composite material numerical model of mesofracture considering a mortar matrix, coarse aggregates, an interfacial transition zone (ITZ) at the meso level and the initial defects of concrete was established. The initial defects were assumed to be distributed randomly in the ITZ of concrete. The numerical model of concrete mesofracture was established to simulate the fracture process of wedge splitting (WS) concrete specimens with widths of 200–2000 mm and three-point bending (3-p-b) concrete specimens with heights of 200–800 mm. The fracture process of concrete was simulated, and the peak load (Pmax) of concrete was predicted using the numerical model. Based on the simulating results, the influence of specimen size of WS and 3-p-b tests on the fracture parameters was analyzed. It was demonstrated that when the specimen size was large enough, the fracture toughness (KIC) value obtained by the linear elastic fracture mechanics formula was independent of the specimen size. Meanwhile, the improved boundary effect model (BEM) was employed to study the tensile strength (ft) and fracture toughness of concrete using the mesofracture numerical model. A discrete value of β = 1.0–1.4 was a sufficient approximation to determine the ft and KIC values of concrete.
Highlights
The mechanical behavior and fracture properties of engineering materials are significantly dimensionally dependent
There were no obvious differences between the fracture phenomena of the 3-p-b specimens and wedge splitting (WS) specimens of concrete for the final failure mode
When the load reached 30% of Pmax, the concrete specimen of 3-p-b cracked from the initial notch tip, and when the load reached 17% of Pmax, the concrete
Summary
The mechanical behavior and fracture properties of engineering materials are significantly dimensionally dependent. Griffith [2] discovered the size effects of fracture parameters of engineering materials through experiments and interpreted it as the effects of defects. A large number of results have shown that the strength and fracture parameters of concrete obtained from experiments vary with the size of specimens [3,4,5,6,7]. Exploration of the regularity and mechanism of the size effect phenomenon has never stopped. By comparing a series of experimental results of specimens with various sizes, it is concluded that the size effect phenomenon exists at a certain scale range
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