An ultrasonic wave-based framework for imaging internal cracks in concrete

Nondestructive detection and sizing of internal cracks initiated in reinforced concrete have been critical problems. Geometric characterization of internal cracks and delaminations contributes to predicting their propagation path and failure pattern followed by structural prognostics. There have been limited studies on quantitative detection and characterization of vertical cracks in concrete using wave-based NDE techniques. This study focuses on solving the problem of imaging deep internal crack planes in the concrete medium by leveraging the ultrasonic shear horizontal (SH) waves from a transducer array. Post-processing the array full matrix capture (FMC) data with both total focusing method (TFM) and plane wave imaging (PWI) reveals their efficiency in mapping planar defects inclined between 0 degrees and 60 degrees. However, their performance on vertical/near-vertical defects is found to be inferior with imaging limited to the tip of the defect planes. Further, half-skip modes of wave dispersion have been adopted in addition to the directly scattered pulses for imaging the vertical and near-vertical cracks. We propose an imaging framework based on the outcomes of our investigation on the best suitable methodology to detect and map planar defects like cracks inclined in the range of 0-90 degrees. Statistical quantification of defect inclinations from the reconstructed images is compared to the ground-truth orientations, and they are found to be 94%-99% accurate. Besides accuracy, the computational efficiency of the proposed techniques makes them desirable and reliable for quick on-site inspections on built infrastructure.

Automated summary

This study focuses on imaging deep internal crack planes in concrete medium using ultrasonic shear horizontal (SH) waves, showing the efficiency of total focusing method (TFM) and plane wave imaging (PWI) in mapping planar defects inclined between 0-60 degrees. The study also proposes an imaging framework based on the investigation outcomes for detecting and mapping planar defects like cracks inclined in the range of 0-90 degrees, with statistical quantification of defect inclinations found to be accurate between 94%-99%.