Kinetics and Surface Alteration of Limestone: Impact of Acid Solutions on the Surface Finishes of Monumental Stones

Stone-cutting marks left on architectural stones are essential for preserving the authenticity of craftsmanship. These surface finishes, tangible witnesses of historical events, traditional construction practices and tooling techniques, embody cultural and technical aspects of intangible heritage.
Although stone is traditionally considered as a durable and permanent, it is not immune to deterioration and undergoes irreversible physico-chemical deterioration caused by environmental interactions. The Nara Document on Authenticity (1994) acknowledges that both natural and anthropogenic material alterations is part of the monuments’ authenticity as well as the material itself, even if the most delicate aesthetic details gradually fade over time. The increasing impact of climate change, including acid rain and pollution, accelerates stone decay, raising concerns about heritage preservation. Acidic compounds from environmental and anthropogenic sources, like acid rain, maintenance products or biological colonisation, significantly contribute to limestone deterioration.
This study investigates the alteration of the Belgian Blue Stone, widely used in Belgian architectural heritage, under the influence of acidic conditions, focusing on three common surface finishes. Laboratory simulations assess weathering kinetics and material loss, initially assessing exposure to household acids to develop a controller system and refine the protocol. 3D optical profilometry quantifies surface roughness and specific surface areas. On saw-cut surfaces, the dissolution of the calcite matrix exposes fossils, increasing roughness, whereas initially rougher surface finishes (pitted, Antique) evolve differently. Comparing exposed and unexposed surface finishes using controller system provides insights into the long-term degradation processes and evolution of roughness, the role of initial texture and deterioration kinetics.