Evaluation of Natural Stone Weathering in Heritage Building by Infrared Thermography

Abstract

The application of non-contact diagnostic methodologies is the current challenge in the frame of the cultural heritage, referred to as preservation, monitoring and restoration. Inspired by the potential shown by infrared thermography in rock mechanics’ non-destructive applications, this paper presents the results achieved by its use for the quick survey of different weathering types affecting natural stones at historical buildings. Infrared thermography allowed recognizing and mapping the different surface temperatures arising from the presence of efflorescence, subflorescence, alveolization, black crusts and bioweathering at limestone and basalt stones. Infrared data were sided by photogrammetric three-dimensional models of surveyed spots, which provided quantitative data on the thickness of rock affected by mechanical weathering, and key correspondence between the two techniques is highlighted. Achieved results show that infrared outcomes are related to different aspects primarily involving the stone face morphology and color, as well as the environmental conditions at the surveying time. Provided interpretations were validated by field visual inspections, which confirmed the good potential of infrared thermography as a quick weathering diagnostic tool. This study can be therefore considered a starting reference for knowledge development in this scientific field.

Condition Assessment of Heritage Buildings via Photogrammetry: A Scoping Review from the Perspective of Decision Makers

“…One of the most documented multi-spectral approaches for photogrammetry-based 3D modelling is related to the combined acquisition of VIS and TIR images. This is certainly due to the great maturity of thermography as a non-destructive method for the investigation of construction materials and techniques, surface alterations, energy performances and humidity patterns in heritage buildings [124][125][126][127][128]. Nonetheless, this is consistent with the need to overcome some shortcomings of 2D thermograms, since they do not provide any metric information, they might be affected by environmental factors, especially when not acquired (quite) perpendicular to the surfaces, and, above all, they can guarantee fair resolution only at a very close camera-target distance, thus requiring manual analysis of large datasets and hindering the general wide overview of complex and/or big-sized objects.…”

Thermography Applied to Damage Diagnosis over Monuments and Ancient Constructions

“…It is in those moments when it is easier to observe the eventual presence of non-homogeneous zones that will dissipate heat in a different way. This makes it possible to locate constructive defects in constituent materials [14][15][16][17][18].…”

An Emissivity-based Approach to Assess the Integrity State of Archaeological Discoveries by Thermography

“…If the discovery is in thermal equilibrium, this condition should generate thermal images having uniform colours. However, alveolisation processes, erosions, damages, deposition of iron oxide, defects, fissures, and material irregularities are cause of not uniform emissivity, [14], [15], [16]. Based on this assumption, the authors aim to map the emissivity changes of the discovery due to different conservation or decay states by evaluating pixel by pixel the temperature deviation around the known equilibrium value.…”