Appraisal of non-destructive in situ techniques to determine moisture- and salt crystallyzation-induced damage in dolostones
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Date
2022
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Publisher
Journal of building engineering
Abstract
The characterisation of both surface and subsurface pathologies (position, depth, width, …) that
affects the porous materials used in building constructions, once in service, is important to
establish the most suitable intervention strategy. In this sense, the use of non-destructive techniques
allows the analysis of different properties without affecting the material. The present study
shows the accuracy of different non-destructive in situ techniques, such as: electrical conductivity
and capacitance, infrared thermography, ultrasonic pulse velocity, sound absorption, and electrical
resistivity tomography, applied on dolostone ashlar stones outer façade of a sixteenthcentury
belltower, affected by moisture and salt induced decay. The joint analysis of the results
obtained with different techniques substantially improves the interpretation and characterisation
of the detected pathologies, as they complement each other perfectly. Electrical
resistivity tomography, which delivers resistivity cross-sections, yields very good results in
detecting subsurface pathologies, and sound absorption is particularly useful for stone surfaces. In
both cases, the frequency of the electric field and that of the acoustic emission to detect the extent
of damage must be established in advance. The joint study of electrical conductivity and
capacitance determines the degree of moisture/salts, both at the surface and subsurface, in the
materials tested, one of the main causes of scaling and flaking in stony materials. However, the
petrological characteristics of the materials used and the identification of the saline phases present
must be known in advance to make a correct interpretation of the results.