Rapid detection of concrete joint activation using normalized shear wave transmission energy.

A rapid and reliable method to detect the activation of contraction joint cracks is needed to assess the effectiveness of sawcut depth and timing on new concrete pavements and for forensic investigation. A one-sided ultrasonic measurement technique is presented that detects the existence of a contraction joint crack, which is not visible from the concrete slab surface. A multi-sensor ultrasonic array device is used to generate and receive ultrasonic shear waves (S-wave) across the inspected joint. The acquired time-domain signals are used to calculate a newly defined feature, called normalised transmission energy (NTE), across the joint. A laboratory experiment investigated the proposed technique on three 500 × 500 × 150 mm³ concrete specimens with 38 mm notch depth, the first without a propagated crack, the second with a narrow width crack, and the third specimen with a full-depth open crack. The laboratory results demonstrate that the NTE technique can identify the existence or not of a crack beneath the notch. Finally, the NTE technique coupled with a 2D decision boundary equation was field validated on 152 concrete pavement contraction joints with various slab thickness (e.g. 102 to 152 mm) and notch depths (less than 38 mm) from multiple projects in Illinois and Iowa (USA). [ABSTRACT FROM AUTHOR]