Abstract:
Consolidation treatment is a common practice in the field of conservation. However, when
considering calcareous materials, there is a lack of efficient and durable consolidants.
Colloidal dispersions of Ca(OH)2 nanoparticles, commonly known as nanolimes, can
effectively recover the 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
dispersions when applied on limestone. A conceptual model, correlating the drying rate and
the kinetic stability of nanolimes 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.
*Manuscript
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Nanolimes were synthetized and dispersed in different solvents (ethanol, isopropanol, butanol
and water). 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 by Uv-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 (Maastricht limestone) and very fine porosity (Migné limestone). The absorption and
drying kinetics and the deposition 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 boiling point solvents e.g. butanol) are more suitable for coarse-pore limestones, while
for fine limestones, more stable 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.