Utilizing Infrared technologies as a non-destructive evaluation for maintenance of concrete structures

Review of Active IR Thermography for Detection and Characterization of Defects in Reinforced Concrete

“…Thus, it is also necessary to establish optimal specifications for an IR camera before any inspection works take place. It was found in the research [28] that thermal sensitivity and pixel resolution do not affect IR inspection so much compared to detector type or spectral range of the cameras.…”

“…Some researchers recommend daytime measurements (4 to 9 h after sunrise) for solar loading part [12] while it was mentioned in SHRP2 report [27] that thermal image of fabricated deck recorded 40 min after sunrise yielded much clearer image than that recorded about noontime. Hiasa et al [28] conducted an experimental study to determine the most thriving time window to collect useful data from an object by using an IR camera. Hiasa et al [28] state that if the difference between damaged and sound part is the only concern, then daytime would be an ideal time window for IR thermography.…”

“…Hiasa et al [28] conducted an experimental study to determine the most thriving time window to collect useful data from an object by using an IR camera. Hiasa et al [28] state that if the difference between damaged and sound part is the only concern, then daytime would be an ideal time window for IR thermography. If IRT is used for deck inspection during daytime, there is a possibility to miss some of delaminated parts of the deck, and there will be a lot of noise in the thermal images, which makes it difficult to detect anomalies in the subsurface.…”

“…This is because temperature differences during nighttime are very stable, even though the differentials are very small, below 0.5˝C but without troublesome noise. In addition to ambient temperature conditions, Hiasa et al [28] indicated that camera specifications such as thermal sensitivity, resolution, and detector type might also affect the accuracy. Thus, it is also necessary to establish optimal specifications for an IR camera before any inspection works take place.…”

“…For optimum results it was recommended that IRT inspections should be conducted when little or no wind and cloud cover are present, defects up to a depth of 20 mm could be detected even with the presence of wind and cloud cover. Contrary to [28], Scott et al [1] recommend that inspections should be conducted after maximum solar loading has been reached in order to accommodate for thermal lag through the concrete and allow for large thermal contrasts to develop. This investigation also showed that steel reinforcement had little influence on the thermal contrast, created by internal defects, on the surface of a concrete element [1].…”