Magnesian limestone is a key construction component of many buildings of historic importance. These materials are prone to attack by various sulfur oxides, particular matter sulfates and other environmental pollutants. Despite the regulation of the sulfur dioxide emissions, sulfate release from natural sources, such as volcanic eruption are ever present and their interaction with limestone masonry causes damage to cultural heritage via dry and wet deposition pathways, which occurs due to formation of hemi-hydrate and gypsum upon the reaction of limestone with acid rain and sulfur dioxide depending on the levels of relative humidity. Gypsum solubilization and permeation through the matrices of limestone causes sub-surface sulfate accumulation, which results in high-decay rates. Hydrophobic coatings can be used to offer protection to these cultural heritage sites.
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