Non-destructive diagnosis by colorimetry of building stone subjected to high temperatures

Abstract

When a building is exposed to fire, the building materials are subjected to high temperatures which cause changes in their structural and aesthetic properties. As the replacement of degraded stones is expensive, a diagnosis of degradation by using non-destructive tests could help to select the appropriate restoration method. The objective of this study is to propose an in situ methodology to assess the state of degradation of stone after exposure to fire by providing a relationship between the state of damage of the stone and its colorimetric properties. Laboratory tests were performed on tuffeau limestone, heated at different temperatures, from 100 to 900°C. Colorimetric measurements were compared to another non-destructive test, ultrasonic P-wave velocity measurements, which are widely used for damage diagnosis of concrete structures.Lorsqu'un monument en pierre est soumis à un incendie, les matériaux de construction subissent de fortes montées en température provoquant une modification de leurs propriétés structurelles mais aussi esthétiques. Le remplacement des pierres altérées a un coût et l'établissement d'un diagnostic de l'état d'altération basé sur un contrôle non-destructif du monument permet de prioriser les remplacements. L'objectif de cette étude est donc de réaliser un diagnostic in situ et non-destructif de l'état d'altération de la pierre après un incendie, en reliant son état d'altération à sa couleur, par le biais de mesures colorimétriques. Dans cette étude, les tests ont été réalisés en laboratoire sur du tuffeau chauffé à différentes températures (de 100 à 900°C). Des mesures de colorimétrie ont été réalisées, comparées ensuite à une autre technique de contrôle non-destructif comme les mesures de vitesse de propagation du son qui est largement utilisé pour le diagnostic d'altération pour les constructions en béton.

Crowdsourcing as an Analytical Method: Metrology of Smartphone Measurements in Heritage Science

“…Colorimetric analysis of surfaces has been frequently used to evaluate changes in compositions and molecular structures of interest to conservation, and the extensive literature on colour change has been the basis of standards for the storage and display of works of art . For example, the yellowing of paper is associated with the oxidation of cellulose; photo‐oxidation results also in the yellowing of many polymers by formation of conjugated unsaturated carbonyl groups; the pigment known as red lead (triplumbic tetraoxide) fades to white through carbonation and sulfation processes; and in limestone, glauconite content can be related to a green hue …”

Evolution of surface properties of ornamental granitoids exposed to high temperatures

“…The first studies of the effect of high temperatures on building stone focused on the variation of bulk mechanical properties in crystalline stones and colour changes due to iron oxidation in sedimentary stones [3,8,9]. From this initial focus on macroscopic variations, research in the last years drifted to assessing mineralogical and textural changes and their effect in building stones [10][11][12][13][14][15][16][17][18][19][20][21][22][23]. Most of these studies focused on the effects of temperature increase, without taking into account ashes and fumes, and therefore were carried out in furnaces on relatively large samples [e.g.…”

“…Most of these studies focused on the effects of temperature increase, without taking into account ashes and fumes, and therefore were carried out in furnaces on relatively large samples [e.g. [8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Commonly, samples were heated with different rates, kept at constant temperatures during a certain time interval and then cooled down freely.…”

“…Sandstone strength increases when heating is moderate, but it is reduced substantially when temperature increase is more intense. The overall degree of decay will depend on the amount and composition of matrix and cement and the subsequent changes in mineralogy, colour and cracking [10,12,14,15,21,23]. Granitoids show different degree of fracturation depending of the temperature [28], showing generally variations in roughness [19,20,26].…”

Crowdsourcing as an Analytical Method: Metrology of Smartphone Measurements in Heritage Science

“…[12] For example,t he yellowing of paper is associated with the oxidation of cellulose; [13] photo-oxidation results also in the yellowing of many polymers by formation of conjugated unsaturated carbonyl groups; [14] the pigment known as red lead (triplumbic tetraoxide) fades to white through carbonation and sulfation processes; [15] and in limestone,glauconite content can be related to ag reen hue. [16] This work assesses the precision, accuracy,and intra-and inter-observer repeatability of measurements contributed by visitors using smartphones.N aturally,e ach of the chemical processes mentioned above and their measurement context have their own requirements in terms of accuracy,b ut to provide ag eneral criterium of quality,w ec onsidered that as uccessful analytical technique should be able to capture ad ifference in colour (or area) before it is perceived by the human eye.T he human eye can detect colour differences smaller than DE = 1under some conditions, [17] but in practice, this threshold is usually higher. This is expressed by the concept of the just noticeable difference (JND), which has been stablished to vary between DE = 1a nd 3i nd ifferent contexts.…”