Abstract

Natural stones are influenced by environmental conditions that might affect their performance and durability as building cladding elements. Among these environmental conditions, one that is not well explored is the study of the impact of SO2 deposition on the mechanical properties of ornamental stones. In this paper, the effect of a SO2-rich atmosphere (constant 10 ppm, with cyclic variations of temperature and relative humidity) on the physical-mechanical properties of some stones from Portugal (three granites and two limestones) is evaluated. Comparative studies on unaged and artificially SO2-aged samples were conducted. Samples were characterized by stereomicroscopy, scanning electron microscopy–X-ray energy dispersive spectroscopy (SEM-EDS), weight variation, and evaluation of elastic dynamic modulus through the fundamental resonance method and of flexural strength under concentrated load. Three granites—Amarelo de Vila Real, Cinzento de Alpalhão, and Cinzento de Pedras Salgadas—and two limestones—Moleanos and Semi-Rijo—from Portugal were chosen, as they are commonly used as cladding natural stones on façades. The obtained results showed that SO2 reacted with both silicate and carbonate stones; neoformed calcium sulfates were identified through SEM with different morphologies and in distinct levels. Its formation induced macro- and microstructural and mechanical modifications. Indeed, calcium sulfate crystallization critically affected mechanical performance through a reduction of elastic modulus and flexural strength in different degrees. Based on the flexural strength and dynamic modulus of elasticity variations, it is possible to recognize that only one granite, Cinzento de Alpalhão, presented lower failure risk in a cladding application. Thus, in urban SO2-rich environments, the effect of this pollutant on natural stone performance should be considered in the material selection stage, leading to improved cladding stone behavior and thus increasing stone service life.

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Data Availability Statement

Some or all data, models, or code that support the findings of this study are available from the corresponding author upon reasonable request.

Acknowledgments

L.G. Rosa and P.M. Amaral gratefully acknowledge the support of this research that was partially funded by the Fundação para a Ciência e a Tecnologia (FCT), Portugal, through IDMEC—Instituto de Engenharia Mecânica (Pólo IST), under LAETA project grant UIDB/50022/2020. A. Dionísio gratefully acknowledges the support of the CERENA (strategic project FCT UIDB/04028/2020). V. Pires gratefully acknowledges the support of Fundação para a Ciência e Tecnologia (FCT) under projects UIDB/04449/2020 and UIDP/04449/2020.

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Journal of Materials in Civil Engineering
Volume 34Issue 6June 2022

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Received: Mar 18, 2021
Accepted: Sep 29, 2021
Published online: Mar 17, 2022
Published in print: Jun 1, 2022
Discussion open until: Aug 17, 2022

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Assistant Researcher, HERCULES Laboratory, Institute for Advanced Studies and Research, Univ. of Évora, Largo Marquês de Marialva 8, 7000-809 Évora, Portugal (corresponding author). ORCID: https://orcid.org/0000-0002-1457-1627. Email: [email protected]
Associated Professor, IDMEC, Instituto de Engenharia Mecânica, Instituto Superior Técnico, Univ. of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. ORCID: https://orcid.org/0000-0003-4730-3765. Email: [email protected]
Associated Professor, IDMEC, Instituto de Engenharia Mecânica, Instituto Superior Técnico, Univ. of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. ORCID: https://orcid.org/0000-0002-6135-8263. Email: [email protected]
A. Dionísio [email protected]
Assistant Professor, Centro de Recursos Naturais e Ambiente (CERENA), Dept. of Civil Engineering, Architecture and Georesources, Instituto Superior Técnico, Univ. of Lisbon, Av. Rovisco Pais, 1049-001 Lisboa, Portugal. Email: [email protected]
Assistant Professor, Dept. of Earth Sciences and GEOBIOTEC, FCT NOVA, 2829-516 Caparica, Portugal. ORCID: https://orcid.org/0000-0003-4351-5090. Email: [email protected]

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