Air-coupled ultrasonic diffuse-wave techniques to evaluate distributed cracking damage in concrete

Eunjong Ahn; Myoungsu Shin; John S Popovics

doi:10.1016/j.ultras.2022.106800

Air-coupled ultrasonic diffuse-wave techniques to evaluate distributed cracking damage in concrete

Ultrasonics. 2022 Sep:125:106800. doi: 10.1016/j.ultras.2022.106800. Epub 2022 Jun 30.

Authors

Eunjong Ahn¹, Myoungsu Shin², John S Popovics³

Affiliations

¹ Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801, USA; Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea.
² Department of Urban and Environmental Engineering, Ulsan National Institute of Science and Technology (UNIST), Ulsan 44919, Republic of Korea. Electronic address: msshin@unist.ac.kr.
³ Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign (UIUC), Urbana, IL 61801, USA.

PMID: 35785632
DOI: 10.1016/j.ultras.2022.106800

Abstract

In this study, we investigated the suitability of applying air-coupled ultrasonic diffuse-wave techniques to concrete structures for the evaluation of arbitrarily distributed micro-cracking damage. Air-coupled test results were compared with those obtained using a conventional full-contact measurement system. Three different micro-cracking damage levels were simulated by embedding varying amounts of low-stiffness polypropylene fibers in concrete samples. Two principal diffuse-wave parameters, diffusivity and dissipation, were determined using air-coupled and full-contact test configurations. Wave frequencies of 300-600 kHz were employed, which set up significant ultrasonic scattering owing to the heterogeneous characteristics of concrete components (e.g., aggregates, micro-cracks expressed by fibers, and pores). In addition, the sensitivities of diffusivity and dissipation to the number of measurement locations were examined. The results demonstrated that the air-coupled method can provide an equivalent reliability to the full-contact method, allowing a much faster and flexible data collection. The spatial averaging of 20 arbitrarily selected data (measured at different locations) yielded sufficiently accurate diffuse-wave parameters, showing less than a 5 % difference from the average of 32 spatially different data.

Keywords: Air-coupled ultrasound; Diffuse wave; Diffusivity; Dissipation; Distributed cracking damage; Non-destructive evaluation.