The Role of Clays in the Decay of Ancient Egyptian Limestone Sculptures

Rodríguez-Navarro, Carlos; Hansen, Eric; Sebastián, Eduardo; Ginell, William S.

doi:10.1179/019713697806373172

Cited by 30 publications

(15 citation statements)

References 18 publications

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“…Aqueous solutions can promote deleterious chemical reactions on stony materials such as dissolution due to low or high pH (Winkler 1994;French 1997) and high ionic strength (Turkington and Paradise 2005), sulphate attack (Neville 2004) and alkaliaggregate reactions (Farny and Kerkhoff 2007). Solutions with soluble salts have also been referred to as promoters of the deleterious effects on some rock constituents, namely clay minerals, by favouring (due to hydroscopicity) wetting-drying cycles (Rodriguez-Navarro et al 1997) and by increasing the volumetric expansion of clays (Pye and Mottershead 1995). Some authors also defend that rock strength can be affected by the composition of pore solutions (Feng et al 2001).…”

Section: Solutionsmentioning

confidence: 97%

“…Water per se has been referred to as capable of causing volumetric changes in stone (Rodriguez-Navarro et al 1997), and the presence of water in pores can also affect rock strength (Winkler 1994). Aqueous solutions can promote deleterious chemical reactions on stony materials such as dissolution due to low or high pH (Winkler 1994;French 1997) and high ionic strength (Turkington and Paradise 2005), sulphate attack (Neville 2004) and alkaliaggregate reactions (Farny and Kerkhoff 2007).…”

Section: Solutionsmentioning

confidence: 99%

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Decay effects of pollutants on stony materials in the built environment

Sanjurjo-Sánchez

Alves

2011

Environ Chem Lett

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This review discuss the effects that pollutants have on stony materials applied on the built environment, illustrating different macroscopical products (pathologies) that can affect historical and modern architectural works. The impact of the decay processes is related to the susceptibility of the materials, environmental conditions and the kind of pollutants that degrade building materials. Here are reviewed the main decay processes resulting from the actions of gases, particulate matter and solutions (from wet deposition to capillary rising and including circulating waters such as run-off), showing that besides atmospheric pollution, also pollutants rising from the ground can cause important deterioration on building materials. Following, the use of tracers is considered for the study of pollutant sources and migration, including neoformation minerals (that might also constitute markers of environmental conditions) and chemical tracers, giving special attention to isotopic tracers, namely to proposals regarding the use of some stable and radioactive isotopes for the study of pollutants that have strong potential but have not been tested yet are also presented. At the end of this chapter, some final considerations are made on the problem of durability assessment of materials in the built environment and also on the use of tracers to assess the origin of damaging compounds in the built environment.

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Section: Solutionsmentioning

confidence: 97%

Section: Solutionsmentioning

confidence: 99%

Decay effects of pollutants on stony materials in the built environment

Sanjurjo-Sánchez

Alves

2011

Environ Chem Lett

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“…Examples of susceptible stone include the brownstone widely used in the northeastern United States (Jimenez Gonzalez et al, 2002), the molasse used in the cathedral of Lausanne, Switzerland (Félix, 1994), and sandstones used in some Egyptian sculpture (Charola et al, 1982;Rodriguez-Navarro et al, 1997). Figure 1 shows damage to the molasse in the cathedral in Lausanne.…”

Section: Introductionmentioning

confidence: 97%

Characterization of swelling in clay-bearing stone

Scherer¹,

Gonzalez²

2005

Stone Decay in the Architectural Environment

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Many sedimentary rocks contain clays that cause differential swelling upon exposure to moisture, and the resulting internal stresses are blamed for the deterioration of buildings and monuments. To predict the likelihood of damage from this mechanism, it is necessary to characterize the magnitude of the swelling and the mechanical properties of the stone. Stones that swell also exhibit viscoelastic behavior, probably owing to sliding of the clay layers. In this paper we discuss the characterization of the relaxation and swelling behavior and the estimation of stresses resulting from swelling. A new method for measuring swelling is introduced, in which warping of a plate of stone is produced by wetting one side. This method is faster than the traditional direct measurement of swelling pressure, and it also yields information about the permeability and the infl uence of wetting on the elastic modulus. Sample results are presented for Portland Brownstone.

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“…Another damage mechanism arises with sandstones that have swelling clay inclusions in the binding phase, where stresses on the order of the strength of the stone can arise due to differential wetting and drying. The problem of swelling clays in conservation has been recognized by a number of authors previously (Rodríguez-Navarro et al 1997;Delgado Rodrigues 2001), and continues to generate interest in recent years (Franzini et al 2007;Sébastian et al 2008). It has been demonstrated that the expansion of Portland brownstone results from intracrystalline swelling of mixed-layer chlorite/smectite clays in the cementing phase by incorporation of as many as four layers of water molecules (Wangler and Scherer 2008).…”

Section: Introductionmentioning

confidence: 97%

Flaw propagation and buckling in clay-bearing sandstones

et al. 2010

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Many historically and culturally significant buildings have sandstones that contain swelling clay inclusions in the binding phase. Differential strains that evolve during wetting and drying cycles can generate stresses that are on the order of the strength of the stone, leading to degradation. Most damage observed in the field is surface delamination and buckling of the stone over a flaw, indicating that the damage is occurring during wetting. Classical buckling theory predicts buckling to occur at a particular aspect ratio, or flaw size. The results of this study confirm buckling theory experimentally. Through finite-element simulation and experiment, the study then explores a potential flaw propagation mechanism whereby nonuniform wetting patterns generate stress intensities capable of flaw propagation. As a result, small natural flaws can grow to the critical size necessary for buckling.

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The Role of Clays in the Decay of Ancient Egyptian Limestone Sculptures

Cited by 30 publications

References 18 publications

Decay effects of pollutants on stony materials in the built environment

Decay effects of pollutants on stony materials in the built environment

Characterization of swelling in clay-bearing stone

Flaw propagation and buckling in clay-bearing sandstones

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