Acoustic Emission Waves Propagation in Rubberized Concrete under Special Monitoring Conditions

This study investigates the change in the acoustic emission (AE) parameters emitted in rubberized concrete under abrasion action at a sub-freezing temperature (-20 degrees C). Seven concrete mixtures were developed with two coarse-to-fine aggregate ratios (C/F) (2.0 and 0.7), various crumb rubber (CR) content (0%, 10%, 20%, and 30%), and different rubber particle sizes [4.5 mm CR and 0.4 mm powder rubber (PR)]. Rotating cutter tests were conducted on three 100 mm cubic samples from each mixture at -20 degrees C and 25 degrees C while monitored via an AE system. AE parameters such as amplitude, number of hits, and signal strength were collected and underwent two parameter-based analyses: b-value and intensity analysis approaches, resulting in three additional parameters: b-value, severity (Sr), and the historic index [H(t)]. Results showed that testing concrete samples under abrasion at cold temperature,-20 degrees C, resulted in a decrease in the emitted number of hits, cumulative signal strength (CSS), Sr, H(t), and an increase in b-values compared to testing at 25 degrees C. Furthermore, incorporating rubber particles was found to decrease the AE signals' amplitudes significantly at 25 degrees C and slightly at -20 degrees C, which manifested the higher wave attenuation occurrence at ambient temperature compared to cold temperature. AE analysis also showed a decrease in the abrasion resistance for mixtures with higher C/F, higher CR content, and larger rubber particle size. These decreases were more noticeable at 25 degrees C compared to -20 degrees C. Finally, the study developed two damage classification charts to estimate the ranges of abrasion mass loss percentage and wear depth in terms of the intensity analysis parameters: Sr and H(t).