Physico-chemical stone-mortar compatibility of commercial stone-repair mortars of historic buildings from Paris

• Commercial stone-repair mortars for surface damaged limestone.
• Raw anhydrous mortars, stone/mortar samples, buildings/laboratory characterization.
• Physico-chemical stone-mortar compatibility assessment.
• Chlorides, sulfates and nitrates from past restorations and environmental pollution.
• Better chemical and mechanical compatibility of mortars with no phyllosilicates.

The physico-chemical compatibility of the most frequently used commercial stone-repair mortars applied to repair surface damage of a common limestone (Euville stone) employed in the basements of historic buildings from Paris was assessed. The characterization of anhydrous raw mortar materials, of stone and mortar samples collected from these buildings and laboratory specimens was carried out.The presence of chlorides and sulfates (gypsum and mixtures of calcium and sodium sulfates) with minor amounts of nitrates in mortar samples collected from the buildings suggest an origin of salts caused by contamination/pollution coming from past restoration products and environmental pollution. The mortar containing quartz, marble aggregates, portlandite and hydraulic components (C3S, C2S and C2AS) with addition of aluminosilicate micro-spherical particles with cementitious properties, and no phyllosilicates, shows a better chemical compatibility with the stone. The mechanical properties of this mortar are also closer to those of the limestone. However, some differences in the hydric properties due to their different pore systems and aesthetic features should be improved in further restoration works.

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