An experimental investigation into the salt-weathering susceptibility of building limestones
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ORIGINAL PAPER
An experimental investigation into the salt‑weathering susceptibility of building limestones Simona Scrivano1 · Laura Gaggero1 Received: 20 November 2019 / Accepted: 17 July 2020 © The Author(s) 2020
Abstract Dimension and ornamental stones used for built heritage are frequently affected, under all climates, by intense weathering induced by the transport of saline solutions. Accordingly, researchers addressed the weathering mechanisms induced by salts (primarily Na2SO4), the stresses generated in the host material, and the durability of ornamental and dimension stones. This study investigates the behaviour of four sedimentary lithotypes, differing in texture and structure (Breccia Aurora, Rosso Verona, and fine- and coarse-grained Vicenza Stone) exposed to a selection of saline solutions, aiming at evaluating their susceptibility to weathering and the influence of petrographic features on durability. The chosen N a2SO4, MgSO4, Na2CO3, NaCl, and KNO3 solutions include the anions characterizing the major saline sources affecting built heritage: capillary rise, acid rain, atmospheric particulate deposition, bird or other animal scat, and de-icing salt contamination. The petrophysical properties of unweathered and salt-weathered samples were characterized by relative mass variation estimation, capillary rise, and hygroscopic absorption-based porosimetry. Scanning Electron Microscopy coupled with microprobe allowed studying the morphological changes triggered by weathering and analysing the chemical composition of the efflorescence crust. The whole of data, consistently with literature, allowed inferring pore type and distribution as the main intrinsic parameters controlling salt weathering susceptibility. Moreover, Na2SO4 and Na2CO3 proved to be the most harmful, probably due to their ability to crystallize in different hydration stages at room temperature. The comparative analysis of the induced weathering can help to choose suitable dimension stones for new buildings or restoration replacements. Keywords Salt weathering · Limestones · Pore network · Salt susceptibility · Dimension stones
1 Introduction Within natural materials, dimension stones in monumental structures and artefacts are studied correlating mineralogicpetrographic and petrophysical characteristics to durability. The added cultural value encourage to study these materials to understand weathering phenomena and the response of each material to diverse environmental parameters, to preserve them (Török and Přikryl 2010). Salt crystallization has a significant effect on the weathering of exposed ornamental and building stones (Amoroso and Fassina 1983; Siegesmund and Snethlage 2014). The significance of soluble salts as weathering agents derives * Simona Scrivano [email protected] 1
Department of Earth, Environment and Life Sciences, University of Genoa, C.so Europa 26, 16132 Genoa, Italy
from their ubiquitous occurrence in a wide range of environments (e.g., urban, desert, coastal, and rural; Goudie and Viles 1
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