Experimental study on loading rate and notch-to-depth ratio effects on flexural performance of self-compacting concrete with acoustic emission and digital image correlation technologies

Abstract

As no extra vibration is needed in the casting procedure of self-compacting concrete for its excellent workability under its own dead weight, the material can be applied to construction projects where vibrations are hard to perform. To better utilize self-compacting concrete in practical engineering, it is essential to conduct an in-depth study on its fracture performance. In this study, three-point bending tests on notched self-compacting concrete beams were performed considering different loading rates and notch-to-depth ratios as variables. Acoustic emission technique and digital image correlation method were utilized to collect acoustic emission signals generated in the loading procedure and monitor crack propagation in the fracture process zone, respectively. Results show that the b-value from acoustic emission analysis can be divided into three stages and the variation range increases as the notch-to-depth ratio increases. Based on clustering analysis, three cluster groups can be obtained, and it is found that the ratio of the first cluster group decreases while that of the third cluster group increases when notch-to-depth ratio increases. With the aid of digital image correlation technique, effective crack length and horizontal crack opening displacement can be recorded and it is observed that crack tip opening displacement decreases as the notch-to-depth ratio increases.

Fracture Energy Measurement in Different Concrete Grades

“…On the contrary, for Hillerborg's model Gf value increased as the concrete strength increased across all notch depths. The Gf decreases as the notch depth increases, a similar observation was revealed [11]. Table 2 presents the comparative analysis of the fracture energy results.…”

Investigation on Acoustic Emission Kaiser Effect and Frequency Spectrum Characteristics of Rock Joints Subjected to Multilevel Cyclic Shear Loads

“…(4) By performing the fast Fourier transform (FFT) on the AE waveform signals, we can obtain the frequency domain information of the waveform signals. Chen et al [36] Joint shear test Skarn 5~35 kHz (less than 5%) 35~122 kHz (more than 90%) 122~170 kHz (less than 5%) Low-amplitude and high-frequency signal (low stress) High-amplitude and low-frequency signal (high stress)…”

“…At present, the research on acoustic emission waveform and frequency spectrum characteristics of rock mainly focuses on compression aspect [27][28][29][30][31][32], and the frequency spectrum analysis had also been carried out on the direct tensile test [33], the Brazilian tensile test [34], and threepoint bending test [35,36]. However, there are few reports on the Kaiser effect and spectrum analysis of rock joint shear test.…”