Experimental Study on Damage Mechanism of Basalt Fiber Reinforced Mortar Based on Acoustic Emission Wavelet Energy Spectrum Analysis

Abstract

To investigate the effect of basalt fiber on the fracturing process and damage mechanism of cement-based materials under axial compression, acoustic emission (AE) signals associated with basalt fiber reinforced mortar (BFRM) with 5 kinds of volume content (0–2.0%) under axial compression were recorded. The statistical analysis of wavelet energy spectrum coefficient and wavelet decomposition coefficient was carried out after threshold de-noising and noise evaluation of original signals by discrete wavelet transform (DWT) based on Mallat algorithm. Results show that the axial compressive strength and the acoustic emission activities decrease with the increase of fiber content. During the fracturing process of basalt fiber reinforced mortar under axial compression, the major energy frequency band concentrates on ca7 (seventh decomposition layers, 0–19.5 kHz), cd5 (fifth decomposition layers, 78–156 kHz) and cd4 (fourth decomposition layers, 156–312.5 kHz) bands corresponding to the wavelet transform. The wavelet energy spectrum coefficient of ca7 and cd4 bands shows distinct phased characteristics, which can be used to identify the damage degree, while the sudden increase in that of cd6 band can serve as a final failure precursor of the specimen. The variation of wavelet energy spectrum coefficient of ca7 and cd4 bands can be used to evaluate the crack resistance of basalt fiber. The maximum wavelet decomposition coefficient and the number of wavelet decomposition coefficient can be used to identify the degree of damage. The statistical analysis of wavelet energy spectrum coefficient and wavelet decomposition coefficient provides an innovative idea for evaluating internal damage of cement-based materials.