Laminar gypsum crust on lede stone: Microspatial characterization and laboratory acid weathering

TALANTA

卷:162

Article

De Kock, Tim^1,2  Van Stappen, Jeroen¹  Fronteau, Gilles³  Boone, Marijn¹  De Boever, Wesley^1,2  Dagrain, Fabrice⁴  Silversmit, Geert⁵  Vincze, Laszlo⁵  Cnudde, Veerle¹ 

[1] Univ Ghent, Dept Geol, PProGRess UGCT, Krijgslaan 281-S8, B-9000 Ghent, Belgium

[2] Inspect BVBA, Technol Pk 3, B-9052 Ghent, Belgium

[3] Univ Reims, GEGENAA EA3795, 2 Esplanade Roland Garros, F-51100 Reims, France

[4] Univ Mons, Stone Assistance Sprl, Spin Off, Clos des Botteresses 4, B-4317 Viemme, Belgium

[5] Univ Ghent, Dept Analyt Chem, XMI, Krijgslaan 281-S12, B-9000 Ghent, Belgium

关键词: Gypsum crust;    X-ray computed microtomography;    X-ray fluorescence mapping;    Drilling resistance;    Scratch test;   

DOI  :  10.1016/j.talanta.2016.10.025

来源: Elsevier

【 摘 要 】

Gypsum crusts are typical decay forms on limestone in polluted urban environments. Their origin and relation to the stone facies have been thoroughly investigated in the past three decades. Here, we present the combined use of novel techniques for a microspatial structural, chemical and mechanical characterization of a laminar black gypsum crust on a sandy limestone. These techniques include i.a. X-ray computed microtomography, Xray Fluorescence micromapping, permeability mapping and the scratch test. They reveal the typical architecture of a laminar gypsum crust, with an outer opaque layer, a subsurface gypsum crystallization layer and a deeper cracked zone passing irregularly into the sound stone. Gypsum crystallization is mostly restricted to an irregular outer zone with an average thickness of 500 mu m, while cracks are found deeper within the rock. These cracks decrease the rock strength to more than 27.5 mm below the surface. Because of their surface parallel orientation and thickness of >10-100 mu m, they create the potential for surface scaling. This is shown by a laboratory acid test where the crack network extensively developed due to further exposure to an SO2 environment. The use of novel techniques opens potential for the study of different decay forms and can be used for stone diagnosis with regards to conservation studies.

【 授权许可】

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