Effect of solvent on nanolime transport within limestone: How to improve in-depth deposition

tConsolidation treatment is a common practice in the field of conservation. However, when consideringcalcareous materials, there is a lack of efficient and durable consolidants.Colloidal dispersions of Ca(OH)2nanoparticles, commonly known as nanolimes, can effectively recoverthe superficial loss of cohesion. However, they do not always guarantee in-depth mass consolidation.The aim of this paper is to give directions for improving in-depth deposition of nanolime dispersionswhen applied on limestone. A conceptual model, correlating the drying rate and the kinetic stability ofnanolimes dispersed in different solvents, to the porosity of the limestone to be treated, is conceived.This model can help to select a suitable nanolime solvent depending on the substrate.Nanolimes were synthetized and dispersed in different solvents (ethanol, isopropanol, butanol andwater). The morphology and size of the lime nanoparticles were studied by dynamic light scattering(DLS) and scanning electron microscopy (SEM-EDS). The kinetic stability of the nanolime was assessed byUv–vis spectroscopy. The porosity of the limestones were determined by mercury intrusion porosimetry(MIP), measuring as well their moisture transport properties.
The model was validated by applying the different nanolimes to two limestones with very coarse (Maas-tricht limestone) and very fine porosity (Migné limestone). The absorption and drying kinetics and thedeposition of the nanolimes within the treated limestones were investigated by phenolphthalein test,optical microscopy and SEM-EDS analysis.The results show that, as suggested by the model, less stable dispersions (as obtained by higher boilingpoint solvents e.g. butanol) are more suitable for coarse-pore limestones, while for fine limestones, morestable nanolime dispersions (as obtained by low boiling point solvents e.g. ethanol) should be preferred.Suggestions are given for further improvement and fine tuning of the nanolimes