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Air-coupled ultrasonic diffuse-wave techniques to evaluate distributed cracking damage in concrete.
Eunjong Ahn1, Myoungsu Shin2, John S Popovics3
1Department 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.
Air-coupled ultrasonic diffuse-wave techniques effectively evaluate micro-cracking in concrete. This non-contact method offers reliable, faster data collection compared to traditional systems for structural health monitoring.
Area of Science:
- Materials Science
- Civil Engineering
- Non-Destructive Testing
Background:
- Concrete structures are susceptible to micro-cracking, impacting structural integrity.
- Accurate damage assessment is crucial for effective structural health monitoring and maintenance.
- Conventional ultrasonic methods often require direct contact, limiting flexibility and speed.
Purpose of the Study:
- To assess the viability of air-coupled ultrasonic diffuse-wave techniques for detecting micro-cracking in concrete.
- To compare the performance of air-coupled methods against traditional full-contact ultrasonic systems.
- To investigate the influence of measurement location number on diffuse-wave parameter accuracy.
Main Methods:
- Simulated micro-cracking in concrete samples using varying amounts of polypropylene fibers.
- Employed air-coupled and full-contact ultrasonic diffuse-wave testing configurations.
- Analyzed diffusivity and dissipation parameters at 300-600 kHz wave frequencies.
- Examined parameter sensitivity to the number of measurement locations.
Main Results:
- Air-coupled ultrasonic diffuse-wave techniques demonstrated comparable reliability to full-contact methods.
- The non-contact approach significantly enhanced data collection speed and flexibility.
- Spatial averaging of 20 data points provided diffuse-wave parameters with less than 5% difference from 32 data points.
Conclusions:
- Air-coupled ultrasonic diffuse-wave testing is a suitable and efficient technique for evaluating micro-cracking in concrete structures.
- This method offers a promising alternative for non-destructive evaluation and structural health monitoring.
- Minimal data points are needed for accurate parameter determination, enhancing practical application.

