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

Wednesday, April 3, 2019 - 17:30

A rapid and reliable method to detect the activation of contraction joint cracks is needed in order to assess the effectiveness of sawcut depth and timing on new concrete pavements and for forensic investigation when premature slab cracking occurs. A one-sided non-destructive 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 normalized transmission energy (NTE) across the joint, defined here as the ratio of energy of diffracted and reflected S-wave received behind the joint with respect to the energy of direct, diffracted, and reflected S-wave received in front of the joint. A laboratory experiment was carried out to investigate the proposed technique on three 500×500×150 mm3 notched concrete specimens, 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 from multiple projects with similar slab thickness and notch depths in Illinois and Iowa (USA). The final report is online at https://apps.ict.illinois.edu/projects/getfile.asp?id=8787