The internal structure of the Villamayor sandstone as it affects its use as a construction material

Patino, M. T. Martín; Madruga, F.; Saavedra, J.

doi:10.1016/0169-1317(93)90026-w

Cited by 7 publications

(1 citation statement)

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“…Damage produced by cyclic swelling and shrinking of clays commonly found as minor components in ornamental and building stone is a major problem in the conservation of cultural heritage (Dunn and Hudec 1966;Caner and Seeley 1978;McGreevy and Smith 1984;Wendler et al 1991;Martin-Patino et al 1993;Kuhnel et al 1994;Ruiz et al 1995;Brattli and Broch 1995).…”

Section: Introductionmentioning

confidence: 99%

The Role of Sepiolite-Palygorskite in the Decay of Ancient Egyptian Limestone Sculptures

Rodríguez-Navarro

Sebastián

Doehne

et al. 1998

Clays and clay miner.

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Abstract--An ancient Egyptian limestone sculpture was found to be undergoing major structural decay when stored in a museum environment. Mineralogical and petrographic analysis of the limestone showed a high proportion of clay (--10% by weight) that was concentrated along bedding planes. The clay fraction consisted mostly of sepiolite (>90%) and palygorskite (< 10%). Minor quantities (--< 1%) of soluble salts (NaCI and NaNO3) were also found. Wetting/drying with distilled water and relative humidity cycling resulted in the same delamination cracking damage as that observed in the museum environment. Thermomechanical analyses (TMA) confirmed that the damage was due to expansion (>4.5%) parallel to bedding planes when the limestone was immersed in water. The expansion due to swelling of the clays was directly observed at high magnification in an environmental scanning electron microscope (ESEM) when wetting/drying cycles were performed. X-ray diffraction (XRD) analysis showed that crystalline swelling of sepiolite occurred. This was determined by a shift of (110) reflection (from 12.07 to 12.20 A) and a decrease of (060) reflection (4.47 A, to 4.44 and 4.41 .~), when in contact with ethylene glycol (EG) and dimethyl sulfoxide (DMSO), respectively. Swelling also occurred due to hydration of the clay surfaces and to electrostatic forces between clay particles, which, it was assumed, was promoted by the presence of Na counterions in water solution. Possible treatments for the conservation of these artistic objects are proposed and discussed.

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