Impacts of consolidation procedures on colour and absorption kinetics of carbonate stones

Abstract

The aim of this research work was to test the influence of stone properties, consolidation product, and application procedure on the potential harmfulness of consolidation on carbonate stones as assessed through the impacts on colour and water absorption kinetics. This article contributes to understanding the immediate and delayed impacts of consolidation treatments through the assessment of colour variation and modification of water absorption kinetics. The investigation was carried out on two limestones having a porosity of 10 and 27%, which were treated with three consolidating products (ethyl silicate, acrylic, and epoxy resins) using three treatment procedures: capillary absorption, brush, and full immersion. All products showed negative impacts at different degrees. We could show that their impact on a given stone depends not only on the consolidant type, but also on the treatment procedures. We demonstrated this way that the assessment of the potential harmfulness of a consolidation treatment for a specific intervention should be carried out in conditions as similar as possible to those expected to occur in practice and should never be based on extrapolations made from any other different conditions. The results also contribute to the definition of standard testing protocols in stone consolidation, privileging the application of a consolidant by direct contact capillary absorption when reproducibility is pursued, or by brushing when the potential highest impacts on colour are the target to evaluate.

Keywords:

• Consolidation
• Treatment
• Limestone
• Harmfulness
• Colour
• Capillary water absorption

Acknowledgements

DGEMN, IST, and LNEC financially supported this work under the project ‘Conservation of carbonate stones. Study and selection of treatments’. The first author acknowledges the support of FEDER and Fundação para a Ciência e Tecnologia through the funding of the research unit ICIST, Instituto de Engenharia de Estruturas, Território e Construção.