Effect of notch-to-depth ratio on flexural and fracture behaviors of UHPGC notched beams based on four-point bending test and acoustic emission

Abstract

An ecological ultra-high-performance glass sand concrete (UHPGC) was prepared by partially replacing quartz sand in traditional ultra-high-performance concrete (UHPC) with glass sand recycled from waste glass. The four-point bending tests of UHPGC notched beams with different notch-depth ratios (0.2, 0.3, 0.4, and 0.5) were carried out, while acoustic emission (AE) monitoring was employed at the whole fracture process. Flexural toughness and residual flexural tensile strength were used to evaluate the flexural properties. Meanwhile, fracture energy and fracture toughness were used to evaluate the fracture properties. The results reveal that notch-depth ratio exhibits a significant effect on the flexural and fracture performances of UHPGC notched beams. The residual flexural tensile strength, flexural toughness, fracture energy and fracture toughness decrease with the increase of notch depth. Moreover, AE energy parameters can favorably characterize the differences of energy release in the fracture processes of UHPGC beams with different notch depths, and favorable correlations are observed between cumulative AE energy and fracture energy. Besides, AE wavelet entropy are constructed based on wavelet packet transform (WPT) of AE waveforms, and the evolution model of wavelet entropy is established. By comparing with the evolution process of AE energy information entropy, it is proved that the maximum point of wavelet entropy can be used as the key point to predict the peak load.