New nanomaterials for consolidating stone

What has been described above induced us to consider the influence of relative humidity (RH) and material’s moisture content in the performance of stone consolidation [8]. [11] on lime pastes has shown that lime pastes exposed to 97% RH are resulted to have a higher carbonation rate compared with pastes exposed to 65% RH, where a small amount of calcium hydroxide was retained.The same authors [12] have also studied the strong influence of both relative humidity and particle size on the carbonation rates of lime pastes and lime mortars.

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In these last years the nanolime has been applied widely, but despite the rapid increase in the literature on nanolime as a conservation material, it is today necessary to set up more technical and practical studies focalized on real specific cases.

For practitioners, it is important to have a broader range of published case studies that describe the nanolime treatment to different environmental situation [4].

Physical chemistry experiments focused on the efficacy of consolidating treatments have been carried out with lime particles (chemical species: calcium hydroxide—Ca(OH)) both in laboratory and in hypogeum environment (catacomb), in order to understand the influence of different microclimatic conditions and to deduce the best nanolime suspension concentration by measuring the microstructure and chemical composition of stone materials differently treated.

The samples examined in the present research come from different materials: laboratory-made samples and stone samples coming from hypogeum environment such as funerary inscriptions fragments.

Callixtus’s catacomb, the site contains a great number of stone materials and wall paintings of great interest from historical, artistic, and religious point of view, by evidencing the necessity to be preserved, protected, and valued in situ.

Both stone materials and wall paintings are chiefly made of calcium carbonate matrix (calcareous stones and plaster) aggregated in various structures.

In order to evaluate the application of nanolime on hypogeum wall paintings, laboratory-made samples have been realized by using real specimens coming from two different hypogeum sites.

The true samples were very small so it has not been possible to treat them directly.

This work grows out from the need to develop consolidating treatments tailored for a specific archaeological structure [1] under hypogeal conditions [2].

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