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

Abstract

Active thermography methods enable structural investigations of reinforced concrete elements taking into account many different testing problems. The goal of this review is to provide an overview on the state-of-the-art regarding the use of active infrared thermography (IRT) for detection and characterization of defects in reinforced concrete. The paper will provide the physical background, equipment being used, as well as post-processing methods that are used to analyse sequences of thermograms. This work also presents the fields of applicability of IRT with a focus on the aspects related to reinforced concrete structures, as well as the advantages, limitations and potential sources of errors of IRT employment. Additionally previous non-destructive testing (NDT) studies that employed thermography techniques with natural excitation are briefly presented. A review of the future trends of thermal imaging are also included in this work. It can be concluded that while IRT is a useful tool for the characterisation of defects in the building sector, there is great prospect for the development of more advanced, effective and accurate approaches that will employ a combination of thermography approaches.

Recycled aggregate concrete for nearly zero-energy buildings

“…69 W/m K to 3 . 3 W/m K (Milovanović, 2013). For the concrete density of 1922 kg/m 3 and 2083 kg/m 3 , ACI Committee 122 (2002) gives thermal conductivities of 0 .…”

A New Grating Thermography for Nondestructive Detection of Cracks in Coatings: Fundamental Principle

“…Therefore, these methods require a relatively long time to detect all the cracks in coatings. Currently, the detection of surface cracks in coatings is still a research hot spot in the nondestructive testing field [10][11][12][13][14][15][16].…”

“…Using the detector array of an infrared camera, infrared thermal wave detection is an effective method to detect massive cracks which are parallel to the surface. Thermal waves are formed on the surface by absorption of modulated radiation and propagate towards the inside of the sample [13]. When they meet cracks or defects, the interaction between the thermal wave and the crack generates a new thermal wave signal which will propagate to the surface.…”

“…In this method the detector array can simultaneously detect multiple horizontal cracks. The recently developed lock-in thermography combines infrared thermal wave imaging technology with the digital phase-locked loop signal processing technology [13][14][15][16][17][18]. It determines the defect characteristics by calculating the amplitude and phase diagram of the sample temperature at each point on the surface.…”

Full-Scale Study of Infrared Thermography for Assessing Surface and Subsurface Defects in Pavements and Other Civil Infrastructure

“…In a passive approach on structures such as bridge decks, natural sources of heat which are present in the environment surrounding the target, such as solar radiation and ambient temperature, are used to heat up the surface of the specimen. These sources are the direct cause for the thermal excitation of the domain(Milovanovic and Pecur 2016). In an active approach however, heat generators such as hot air blowers, microwaves, electricity or vibrations are used to employ heat on the surface or the body of the domain(Kashif Ur-Rehman et al 2016).…”