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| Titel |
Identification and cause of decay of building materials used in the architectural heritage of Bizerte city (Tunisia) |
| VerfasserIn |
Karima Zoghlami, Paula Lopez-Arce, Antonia Navarro, Ainara Zornoza-Indart, David Gómez |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250138596
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| Publikation (Nr.) |
 EGU/EGU2017-1659.pdf |
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| Zusammenfassung |
| Monuments and historical buildings of Bizerte show a disturbing state of degradation. In order to propose a
compatible materials for the restauration works such as stone of substitution and restauration mortars, a geological
context was analysed with the objectif to localize historical quarries accompanied by a sedimentological study
to identify the exploited geological formations. Petrophysical and chemical caracterisation of both stone and
mortars have been carried out. With the aim to determine the origin of the erosion and the degree of stone decay,
a combination of micro-destructive and non-destructive techniques have been used on-site and in-lab. Moisture
measurements, ultrasonic velocity propagation and water absorption by Karsten pipe test together with polarized
light and fluorescence optical microscopy, mercury intrusion porosimetry and ion chromatography analyses were
carried out to perform petrophysical characterization of stone samples and determination of soluble salts. For the
characterization of mortars, granulometric study was performed to determine the nature of components and their
grain size distribution. Thin sections of mortar samples were examined for the petrographical and mineralogical
characterization. X-ray diffraction (XRD) analysis of finely pulverized samples was performed in order to identify
the mineral crystalline phases of the mortars. Thermal analyses [thermogravimetry (TG)] were performed in order
to determine the nature of the binder and its properties. Porosity was determined following UNE-EN 1936 (2007)
standart test.
Geological and petrographical study showed that historical buildings are essentially built with high porous
bioclastic calcarenite partially cemented by calcite which is Würm in age and outcrops all along the northern
coast of Bizerte where several historical quarries were identified. Occasionally, two other types of lithologies
were used as building stones and they correspond to two varieties of oligocene sandstones (brown quartz-arenite
cemented by iron oxide and ochre-green colored sandstone cemented by calcite) and an eocene white limestone
corresponding to a fine-grained globigerine wackstone according to Dunham classification.
Results of the petrophysical study show that small variations in the petrographic characteristics of the building
geomaterials, such as type and degree of cementation, porous network configuration and presence or absence of
soluble salts leads to differential stone weathering.
Results of study’s mortars show that original and restoration mortars have similar mineralogical composition
but different grain size distribution and proportion of binder/agregats. They differ equally by the nature of raw
materials as demonstrated by the thermal analyses. The study show that little variation of these parameters can
affect the durability and the performance of mortars and can accelerate the degradation process of the building
stones, especially the oligocene and eocene lithotypes. |
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