Leveraging Active Thermography for Facade Detection at Jesolo Beach Condominium

Active thermography is a thermographic investigation conducted in a state of thermal transition, generally from cold to hot (in storage) but also vice versa (in release).

By uniformly heating a structure, it is possible to observe the thermal behavior of its constituent materials, which will increase their temperature at varying rates and in different manners, depending on their thermal inertia. This allows for an analysis of the thermal dynamism of the 'façade' to make considerations about what is happening beneath the surface layer. In construction, for example, one observes what occurs beneath the plaster.

Active thermography can effectively highlight the masonry pattern, as well as any defects not yet visible, such as cracks in the masonry and plaster detachment. The air that fills these spaces has a very low thermal inertia; it will heat up much faster and will be visible as a 'hot zone,' its outline will suggest what it is.

Active thermography is not only used in construction but also, for example, on composite materials such as fiberglass hulls, carbon fiber, etc. In this case, it will be possible to detect defects such as delamination, porosity, disbonding, etc.

To accelerate the accumulation process and provide greater contrast to the phenomena under observation, solar radiation is used if possible, or that of infrared heating lamps if working indoors, for example.

In order to take full advantage of the benefits of active thermography, it is always best to have a thermal imaging camera with high thermal sensitivity (NETD) and a high-resolution sensor capable of offering images with a large number of pixels on the defect you want to observe.

Meticulously planning the work is the basis for the success of an active thermography campaign, as in the example below in which Arch. Guido Roche of Architecno srl describes to us a step-by-step inspection performed with a Hikmicro G61 thermal imaging camera.

The investigation

Purpose of the investigation: Detection of facade rebar cover detachments

Localization: Lido di Jesolo

Environmental Conditions: Day in full sunshine with a temperature of about 12°C and RH of 65%

Equipment used: Hikmicro G61 with standard optics

Irradiance: Constant on the fronts under investigation

Method of execution: The survey campaign was carried out in active mode, acquiring the thermal images during irradiation. The thermographic survey started in passive mode before the onset of irradiation on the elevations and then carried out on the same elevations, the survey in active mode by analyzing the thermal transient. The detachments of the rebar covers were detected during the first solar heating phase, taking advantage of the insulating power of the air inside the detached portion. During the heating phase, the portions where the cover-iron is well adhered to the masonry turn out to be cooler because the heat absorbed by the masonry in the heating phase, by conduction, is transferred inside the structure itself. In the case of detachment, on the other hand, with equal heat provided on the surface, the detached areas appear warmer because the heat is stopped on the surface by the insulating power of the air enclosed within the detached portion.

Results obtained: Shown below are some of the thermal images that were generated within the project, where detached portions that in thermal infrared appear to be hotter are highlighted.

The defects found are indicated by the blue arrows on the radiometric images.

Conclusions: The investigation enabled the detection of the detached portions of the concrete covers in a very sharp manner due to the high thermal resolution of the thermal imaging camera used. The surveys were acquired with standard optics. A wide-angle lens was also employed during the survey to enable the thermal anomalies on the investigated elevations to be appreciated with great speed. The high thermal resolution combined with the frequency of acquisition allowed the detection of thermal anomalies even when employing a wide-angle lens.

The Gx1 Series

Active thermography is therefore useful in the search for defects that are not visible in the building field. Indeed, thanks to this inspection technique, it is possible to detect possible anomalies in advance and intervene before they actually turn into damage, not only to the building but also to people. Moreover, early intervention makes it possible to significantly reduce restoration costs by operating in a targeted and localized manner in areas where the thermographic operator has identified possible problems.

Thanks to their high resolution and high thermal sensitivity, HIKMICRO thermal imaging cameras are ideal for this type of activity. In the case study we discussed, the G61 model proved to be a perfect tool for the purposes of the investigation. The 640x480 thermal sensor, combined with a standard lens, sped up facade inspections even at long distances, thanks to a congruous ratio of resolution to field of view. Where it was needed, however, the integration of the additional telephoto lens instrument proved essential to view critical areas in greater detail.