The Susceptibility to Salt Fog Degradation of Stone Cladding Materials: A Laboratory Case Study on Two Limestones from Portugal

Abstract

The evaluation of stone cladding material suitability can be a challenge due to the way that stone physical and mechanical properties, and characteristics such as mineralogy, might influence stone performance as a cladding element in a ventilated facade application. Salts can affect natural stone performance, and one of the experimental methods available to study and predict it is through accelerated aging tests such as salt fog chamber cycles. Aging test results should include the analysis of critical stone physical–mechanical properties to fully understand decay effects. The aim of this study was to reduce the lack of knowledge regarding the implications of salt fog on certain fundamental characteristics of stone cladding requirements, such as elastic properties and flexural strength, because these are particularly important properties for ventilated facade systems. A systematic methodology based on artificial salt fog cycles in a climatic chamber, microscopic analysis, weight measurement, flexural strength, and dynamic elastic modulus was performed on two limestones from Portugal: Moleanos (MO) and Semi-Rijo (SR). This study aims to contribute to improved selection stone methods linked to more sustainable stone facades, and the experimental methodology can be further applied to other stone types, particularly the ones most selected for stone cladding applications near coastal areas. In this work, results of salt fog decay cycles are presented and discussed considering their direct contribution for a better stone-cladding dimensioning process.

Effect of Salt Mist Ageing on the Physical and Mechanical Properties of Two Ignimbrites from the Canary Islands (Spain)

“…The variation in flexural strength after salt spray ageing was similar to that found in other studies, where the flexural strength usually decreases by around 10% to 30% [29,30]. The increase in flexural strength that occurred in LT ignimbrite was an unusual behaviour, but it also occurred in these studies, and although the variation was close to 9%, it cannot be concluded that it is a significant increase due to the scatter of the results.…”

“…Based on the consulted literature, limestone is one of the most studied building stones in terms of deterioration caused by salt mist. Pires et al [28,29] studied two limestones from Portugal and concluded that after exposure to 45 cycles of salt spray, the samples suffered a loss of mass (between 4.0 and 9.0%) as well as a reduction in modulus of elasticity (between 20 and 30%) and in flexural strength (close to 30%). The behaviour of a group of six limestones, also from Portugal, was studied Carvalho et al [30,31].…”

An assessment of the durability of untreated and water repellent-treated cultural heritage stone (Döğer tuff-Turkey) by salt mist and salt crystallization tests

“…For instance, Fort et al (2014) reported no change in the porosity of Colmenar limestone after 120 salt mist cycles. Similarly, Pires et al (2014) observed an increase in the average pore diameter from 0.14 μm to 0.17 μm after 45 salt mist cycles in biomicrite limestone. These findings provide insights into the response of porosity and pore size distribution in tuff stone materials subjected to salt mist conditions.…”

Hydrophobic Coatings’ Efficiency and Limestones’ Resistance to Salt Crystallisation

“…The application of hydrophobic treatments is a preventive maintenance practice to face the damaging effects of salt and ensure the longevity of construction materials. These coatings serve the following two important purposes, especially when stones are installed as cladding: first, to prevent the intrusion of aqueous solutions and their associated damage [11]; second, to safeguard metal fixings from corrosion in aggressive environments, thereby preventing instability and the potential collapse of slabs [12][13][14]. The application of hydrophobic treatments is a preventive maintenance practice to face the damaging effects of salt and ensure the longevity of construction materials.…”