Delaminations in concrete bridge decks are a major cause of bridge maintenance problems. Sonic inspection techniques are currently being used for condition surveys to identify those bridge decks on which expenditures of funds are both necessary and cost effective. While the current sonic methods are reliable, they are too slow for the survey application. A need exists for a rapid, non-destructive method for assessing the general condition of the bridge decks without closing the deck to traffic. The inspection techniques considered for use were infrared thermography, electro-magnetic sounding, nuclear radiation and acoustic techniques. Electromagnetic sounding, by using pulsed radar, has the best potential for use in the development of a rapid survey system.

" TRB's second Strategic Highway Research Program (SHRP 2) Report S2-R06A-RR-1: Nondestructive Testing to Identify Concrete Bridge Deck Deterioration identifies nondestructive testing technologies for detecting and characterizing common forms of deterioration in concrete bridge decks.The report also documents the validation of promising technologies, and grades and ranks the technologies based on results of the validations.The main product of this project will be an electronic repository for practitioners, known as the NDToolbox, which will provide information regarding recommended technologies for the detection of a particular deterioration. " -- publisher's description.

Delamination detection in concrete bridge decks is a critical process to the maintenance and upkeep of concrete bridges. Excessive delamination can lead to spalling, damages to properties or human life, and possible failure in extreme cases. Therefore, intense work has been directed toward developing accurate and efficient detection methods. The methods adopted were mainly within the non-destructive evaluation realm of detection to avoid damages to the structure and the financial losses associated. The methods range from traditional techniques such as hammer-sounding, and chain dragging to more effective methods such as impact echo, groundpenetrating radar, ultrasonic test, and infrared thermography. This research focused on the application of infrared thermography as a non-destructive evaluation method through the utilization of an unmanned aerial vehicle-mounted consumer-grade thermal camera. The purpose main purpose was to investigate the accuracy of detection using a consumer-grade thermal camera vs. research-grade thermal camera. Another goal was to provide an efficient and cost-effective data collection method for concrete bridge delamination detection that does not require traffic obstruction such as other NDE methods, and provides more accurate results compared currently deployed methods such as hammer-sounding. Concrete delamination detection using (UAV)-mounted infrared cameras has proved effective in recent research. However, most successful implementations used expensive research-grade infrared cameras. Despite research-grade thermal camera having high resolution and providing accurate results, they are heavy, expensive, need onboard computers, customized drones, and require-proprietary software to operate. This makes the process challenging to implement in state Department of Transportations (DOTs) due to the lack of specialty professionals. Many state DOTs started deploying lightweight consumer-grade infrared cameras UAVs for delamination detection. However, few studies have quantitatively evaluated the accuracy of the lower-resolution uncooled consumer-grade infrared camera for delamination detection. To fill this gap, this study intends to investigate if a consumer-grade infrared camera can maintain an acceptable level of delamination detection, allowing for infrared thermography to be a more accessible and affordable detection method. The advantage of utilizing a consumer-grade camera is that they are less expensive, and lighter thus allowing them to be carried by smaller drones. This study explores the application of infrared thermography (IRT) and a consumer-grade thermal camera mounted on an unmanned aerial vehicle (UAV) for delamination detection while employing the level-set method for image analysis. Data was collected for a slab with mimicked delamination and two in-service bridge decks. For the case of the slab, maximum detectability of 70 - 72% was achieved. A transient numerical simulation was also conducted to provide a supplemental and noise-free dataset to explore detectability accuracy peaks throughout the day. The results of the in-service bridge decks indicated that the consumer-grade infrared camera provided adequate detection of the locations of suspected delamination. Results of both the slab and in-service bridge decks were comparable to those of a research-grade infrared camera.

An objective view of the relative advantages and limitations of the nondestructive testing and evaluation methods that are currently used in the inspection of bridge decks is presented and discussed. The three main nondestructive testing technologies that were evaluated are impact-echo, ground penetrating radar, and infrared thermography. Nondestructive testing and evaluation procedures, including methodology and equipment to evaluate concrete bridge decks with asphalt overlays, are also presented and discussed. Current results indicate that a combination of ground penetrating radar and infrared thermography would provide the best methodology for evaluating the structural integrity, e.g., delaminations, of concrete bridge decks with overlays. Furthermore, current results also indicate that the impact-echo method shows promising future development towards the nondestructive evaluation of bridge superstructures.