Contribution to the technological characterization of two widely used Portuguese dimension stones: the ‘Semi-rijo’ and ‘Moca Creme’ stones
Carlos Figueiredo, Rita Folha, António Maurício, Carlos Alves, Luís Aires-Barros, 2010. "Contribution to the technological characterization of two widely used Portuguese dimension stones: the ‘Semi-rijo’ and ‘Moca Creme’ stones", Natural Stone Resources for Historical Monuments, R Přikryl, Á Török
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Stone weathering and durability are two major concerns widely recognized within construction, cultural heritage and monument stone decay assessment and conservation works. This paper aims to complement the technological data on the two commercial varieties of Portuguese dimension stones (‘Semi-rijo’ and ‘Moca Creme’), widely used in pavement and cladding inside and outside buildings. New data on the pore structures (fluid transport–related properties) and the durability (salt crystallization tests) of these limestones are presented. The pore structure was studied by a combined application of optical microscopy, scanning electron microscopy and mercury injection porosimetry. Fluid migration physical tests (open and free porosity, capillary imbibition and Hirschwald coefficient) were also performed, according to Portuguese and French standards. The resistance to salt crystallization was determined using the Portuguese standard NP EN 12370. An integrated analysis of all data has allowed a comparison of the results of the durability tests with characteristics of the pore network and properties related to fluid transport as well as petrographical features of the stones. The open porosity and freely-interconnected pores accessible to water after 48 hours (N48) seem to be the main features controlling their durability.
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Natural stone is considered to be a versatile, durable and aesthetically pleasing building material. From the beginning of civilization, important structures and monuments have been built from, or based on, natural stone. Until the end of the nineteenth century, the use of local stone resources was mostly in balance with the local environment. Strict environmental legislation has resulted in the closing of many long-standing quarries in industrialized countries, which has led to a shortage of traditional stone varieties. This has caused problems for restoration practice. Cheap, imported stone from less industrialized countries has become more widely available in recent years.
Some of the issues related to built stone conservation and restoration covered by this volume are: the establishment of inventories of possible replacement stones; understanding the decay mechanism and use of preventive conservation methods for slowing down decay processes; evaluation of the properties of natural stone; and assessing the risks of using replacement stones of different qualities.