Pore structure and durability of Portuguese limestones: a case study
C. Figueiredo, R. Folha, A. Maurício, C. Alves, L. Aires-Barros, 2010. "Pore structure and durability of Portuguese limestones: a case study", 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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Exposed stone surfaces containing complex systems of pores, fractures and grain boundaries provide the surfaces where chemical, physical and biological deterioration processes take place. The pore space represents the preferred area for physical, chemical and biological weathering processes. It plays a significant role in the behaviour of porous materials. A full understanding of pore-channel network morphology, size and connectivity is important in stone decay assessment and conservation works. A contribution to the understanding of the role played by the pore system in controlling fluid-related properties and resistance to salt crystallization of limestones is presented. Optical microscopy, scanning electron microscopy (SEM) and mercury injection porosimetry (MIP) were used to characterize the pore structure of two Portuguese dimension stones (‘Semi-rijo’ and ‘Moca-Creme’) widely used for pavements and the cladding of buildings. Fluid migration physical tests (open and free porosity, capillary imbibition, and Hirschwald coefficient) were also performed, according to European (EN 1925:1999; EN 1936:1999) and French (N FB 10-504:1973) Standards. The resistance to salt crystallization was determined using European Standard EN 12370:1999. An integrated analysis facilitated comparison between durability results with stone pore network characteristics, fluid transport properties and petrographical features, suggesting the influence of available porosity and bedding.
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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.