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Título
Effect of Artificial Freeze/Thaw and Thermal Shock Ageing, Combined or Not with Salt Crystallisation on the Colour of Zamora Building Stones (Spain)
Autor(es)
Palabras clave
Piedras (edificaciones)
Conglomerados
silicified conglomerates
artificial ageing test
building stones
Clasificación UNESCO
3310.04 Ingeniería de Mantenimiento
6203.05 Estética de las Bellas Artes
Fecha de publicación
2022
Editor
MDPI
Citación
García-Talegón, J.; Iñigo, A.C.; Sepúlveda, R.; Azofra, E. Effect of Artificial Freeze/Thaw and Thermal Shock Ageing, Combined or Not with Salt Crystallisation on the Colour of Zamora Building Stones (Spain). ChemEngineering 2022, 6, 61. https://doi.org/10.3390/chemengineering6040061
Resumen
[En] After subjecting Zamora building stones to accelerated ageing tests, colour changes were
studied, namely: (a) freezing/thawing and thermal shock (gelifraction and thermoclasty), and (b) combination
of freezing/thawing plus thermal shock and salt crystallisation (sulphates or phosphates)
(gelifraction, thermoclasty and haloclasty). Zamora building stones are silicified conglomerates
(silcretes) from the Cretaceous that show marked colour changes due to the remobilisation of iron
oxyhydroxides. In this work, four varieties were: white stone; ochreous stone; white and red stone;
and purple stone Their micromorphological characterization (skeleton, weathering plasma and
porosity/cutan) is formed of grains and fragments of quartz and quartzite as well as by accesory
minerals muscovite and feldspar (more or less altered), and some opaque. Quartz, feldspar and
illite/mica were part of the skeleton; kaolinite, iron oxyhydroxides, and CT opal were part of the
weathering plasma or cutans; their porosity were 11.7–8.7%. Their chromatic data have been statistically
analysed (MANOVA-Biplot). They showed higher variations in DE*, DL*, Da* and Db*on
combined freezing/thawing plus thermal shock and sulphates crystallisation leading to rapid alteration
of the building stones. Chromatic differences between the other two artificial ageing tests
were less evident and were not detected in all samples. The global effect of ageing on the Zamora
building stones darkened them and reduced their yellowing. The ochreous stone suffered the least
variation and the purple stone the most. This study of the colour by statistical analyse may be of
interest for the evaluation and monitoring of stone decay, which is an inexpensive, simple, easy and
non-destructive technique.
URI
DOI
10.3390/chemengineering6040061
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