Weathering effects in an urban environment: a case study of tuffeau, a French porous limestone
K. Beck, M. Al-Mukhtar, 2010. "Weathering effects in an urban environment: a case study of tuffeau, a French porous limestone", Limestone in the Built Environment: Present-Day Challenges for the Preservation of the Past, B. J. Smith, M. Gomez-Heras, H. A. Viles, J. Cassar
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A case study is carried out on a highly porous limestone called tuffeau located in an urban environment. Weathering effects are characterized by several complementary techniques: mechanical resistance (compressive test), imbibition (capillarity test), mercury intrusion porosimetry, chemical analysis [inductively coupled plasma-optical emission spectrometer (ICP-OES)], scanning electron microscope (SEM) image analysis and X-ray diffraction (XRD). The results show the different composition of the deteriorated zone of the stone and mainly the presence of high gypsum content in the black crust surface. The analysis also shows that the natural penetration of water into this stone under environmental conditions (atmospheric precipitation, relative humidity and temperature) is limited to 20 mm. Moreover, the presence of gypsum is only detected in this limited zone, which demonstrates the depth of alteration in this stone. Finally, this study clearly highlights the important role of water movements in the deterioration of stone.
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Limestone is a highly successful and widely used building material, found in many important historic buildings and new monuments around the world. Whilst its success reflects its durability under a wide range of environmental conditions, there are still important questions surrounding the selection, use and conservation of building limestones. In order to make best use of new limestone today, and to conserve old limestone most effectively, we need to bring modern research methods to bear on understanding the characteristics of different limestones, what mortars to use, and how key limestones have responded to polluted atmospheres. This volume brings together recent inter-disciplinary research on these issues, illustrating the diversity of innovative techniques that are now being applied to furthering our understanding of building limestones.