The application of gray-scale level-set method in segmentation of concrete deck delamination using infrared images

Abstract

Conventional nondestructive delamination detection of concrete pavements through thermography is often based on temperature contrasts between delaminated and sound areas. Non-uniform backgrounds caused by the environmental conditions are often challenging for contrast-based methods to robustly differentiate the delaminated areas from the sound areas. Instead of focusing on the temperature contrast, this study proposes a temperature gradient-based level set method (LSM) to detect boundaries for delamination segmentations. A modified edge indicator function is developed to represent the normalized temperature gradient of a thermal image. The experimental study was conducted to evaluate its applicability and stability for boundary detection in terms of different burial depths and observation time windows. Then the LSM generated edges LSM were used for delamination segmentations. The results demonstrated significant improvements compared to the well-accepted k-mean method in terms of accuracy and stability of the detections. A field implementation of this method using an in-service bridge generated satisfactory outcomes when compared to the ground truth data. Major limitations and future works are also discussed in terms of parameter selections.