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. 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.@en

Nanolimes, i.e. dispersions of lime (Ca(OH)2)nanoparticles in alcohol, have been extensively investigated over the last two decades as consolidation products for calcareous substrates. The use of nanolimes for consolidation of mural paintings arises from the lack of e ective and compatible consolidants for this type of substrates; the use of nanolimes was later extended also to limestone and lime-based mortars, as an alternative for silica-precursor consolidants (e.g. tetraethoxysilan - TEOS), which had shown to have a limited e ectiveness and compatibility with calcareous substrates. Nanolime dispersions are characterized by a very small size of the lime particles, which should provide a proper penetration within the porous network of most building materials. In fact, a homogeneous and in-depth penetration of the consolidant is a crucial requirement when dealing with decayed stones and plasters/renders. The e ectiveness of nanolime dispersions reported in literature appears controversial. Some authors observed a proper penetration and moderate consolidating action, whereas others report poor penetration, poor consolidation action and sometimes the formation of a white haze on the treated surface. There is no agreement concerning the factors a ecting the transport and deposition of the lime nanoparticles within a porous network, and the causes of the observed drawbacks are not well understood. Therefore, the main research question is: Is nanolime a suitable alternative to silica-precursor consolidants (e.g. TEOS) for the consolidation of calcareous substrates? More speci cally, the following research questions can be formulated: – How and up to which extent can the e ectiveness and compatibility of nanolime be improved? How can deposition of nanolime in depth be improved and the appearance of a white haze on the surface avoided? – How can nanolime properties be ne-tuned to improve the e ectiveness and compatibility of the treatment? – What is the e ect of di erent application methods on the e ectiveness of nanolime consolidation? This research investigates and elucidates the behaviour of nanolime products for consolidation of calcareous substrates. Based on the developed knowledge, it proposes and validates a methodology (including solvent modi cation and application protocol) for improving the consolidation e ectiveness of nanolime dispersions, making these a suitable alternative for TEOS products. Firstly, an experimental campaign was carried out in order to understand the penetration and deposition of commercial nanolimes on coarse porous calcareous substrates (Maastricht limestone). The main cause of the poor nanolime deposition in-depth was identi ed in the back-transport of the nanoparticles towards the drying surface, as a consequence of the high volatility and low kinetic stability of the dispersions. The modi cation of the nanolime properties, through the optimization of the solvent, appears thus a feasible strategy to improve the in-depth deposition of the lime nanoparticles. New nanolimes were synthetized and dispersed in a selection of solvents conferring di erent stability and drying rate to the obtained nanolime dispersions. A conceptual model, correlating the properties (i.e. drying rate and kinetic stability) of nanolimes dispersed in di erent solvents, to the moisture transport behaviour of the substrates to be treated, was conceived. The model was experimentally validated on coarse porous (Maastricht) and ne-porous (Migné) limestones. Experimental results con rmed the predictions of the model that nanolimes dispersed in solvent with lower volatility and stability (e.g. water or butanol) have a good in-depth deposition within coarse porous networks. On the other hand, solvents with higher volatility and guaranteeing higher kinetic stability (e.g. ethanol or isopropanol) to the relative dispersions, should be preferred for substrates with ne porous networks. Fine- tuning the properties of the nanolime dispersion (by modi cation of the solvent) to the moisture transport behaviour of the substrate, is shown to be a successful strategy for improving in-depth deposition of lime nanoparticles. On the basis of the obtained results, the solvent mixture was further ne-tuned using ethanol-water mixtures. Results proved that ethanol-based nanolime, mixed with a minor amount of water (5%), can provide be er nanoparticles in-depth deposition within coarse porous substrates (e.g. Maastricht limestone), when compared to dispersions in pure ethanol. The application procedure of nanolime dispersions was also studied and optimized, this step being a crucial aspect for a successful consolidation; nanolimes were applied both by capillary absorption (method commonly used for laboratory tests) or by nebulization (method widely used in situ) on a coarse porous limestone and a mortar. 20 Nanostructured lime-based materials for the conservation of calcareous The research showed that results obtained by application through capillary absorption do not always correspond to those obtained by nebulization. The e ectiveness and compatibility of nanolimes with improved properties and a ne-tuned application protocol were nally veri ed. Fresh and weathered Maastricht limestone, as well as lime-based mortars, were treated. Results showed that nanolime dispersions can guarantee an in-depth consolidation both in laboratory mortar specimens and weathered limestone, with only a moderate alteration of the total porosity and of the moisture transport properties of the investigated substrates. Therefore, nanolime dispersions, provided that they are properly formulated and applied, can be a suitable and compatible alternative to TEOS for the consolidation of coarse porous substrates. This dissertation contributes to de ne guidelines to support restorers and professionals in the choice and application of nanolime dispersions for consolidation of calcareous substrates.@en

Surface consolidation is a common practice in the conservation of the built heritage. However, the effectiveness of consolidation of calcareous materials is often doubtful, due to the lack of effective and compatible consolidation products. Dispersions of calcium hydroxide nanoparticles in alcohol, the so-called nanolimes, can recover the superficial consolidation of calcareous substrates. Nevertheless, they are often not able to guarantee an in-depth consolidation. Previous research by the authors has demonstrated that the effectiveness of nanolime can be improved by fine-tuning the properties and the application protocol of the dispersions, based on the moisture transport properties of the material to be treated. In this paper, we verify the consolidation effectiveness and physical compatibility of the developed nanolimes, when applied on coarse porous calcareous materials like Maastricht limestone and lime-based mortars. The results show that a suitable mass consolidation can be achieved with nanolimes, while maintaining a good compatibility with the substrate material.@en

This research aims to evaluate the intervention techniques currently adopted for the traditional timber frame wall, using a case study in downtown Lisbon. Different rehabilitation solutions were identified and assessed through a multi-criteria decision analysis using dedicated software (M-Macbeth, Measuring Attractiveness by a Categorical-Based Evaluation technique). Five evaluation criteria, i.e. material compatibility and permanence, structural reliability and authenticity, and visual-tactile appearance, were selected for this specific context. A multidisciplinary panel of experts in conservation science were consulted for defining the performance descriptors, evaluation levels, and weightings of these criteria. Results show that Macbeth is a useful decision-aid capable of handling multiple outputs generated from qualitative expert judgments. Lastly, the predominance of five best-scoring interventions within three design-related scenarios is discussed.@en

The analytical characterization of mortar samples from the roman archaeological site of Pisões, located in Southern Portugal, were carried out by means of X-ray diffractometry (XRD), thermogravimetry (TGA-DTA), optical and electron scanning microscopy (SEM-EDS), potentiometry and combustion analysis. The Pisões archaeological complex includes a villa rustica, characterized by well-preserved mosaics and thermal baths, as well as a mill and a mausoleum. Countryside villae epitomized the Romanization of the Iberian Peninsula for over six centuries (2nd century BCE–4th century CE). Nevertheless, most of the Roman villae identified in Portugal have not yet been systematically explored and studied. This study provides valuable data on the construction materials and techniques used in Roman times in the Iberian Peninsula. The careful selection of raw materials and the use of natural and artificial pozzolanic materials can explain the favourable state of conservation, mechanical strength and long-term durability of these mortars.@en

The potentialities of nanomaterials for applica- tion in the field of conservation have been widely investi- gated in the last two decades. Among nanomaterials, nanolimes, i.e., dispersions of lime nanoparticles in alco- hols are promising consolidating products for calcareous materials. Nanolimes are effective in recovering the very superficial loss of cohesion of decayed materials, but they do not always provide sufficient mass consolidation. This limitation is mainly related to the deposition of the nanoparticles nearby the surface of the material. Experi- mental research has been set up with the aim of improving the in-depth deposition of lime nanoparticles. Previous research by the authors has shown that nanolime deposition within a substrate can be controlled by adapting the nanolimes properties (kinetic stability and evaporation rate) to the moisture transport behavior of the substrate. Nanolime properties can be modified by the use of different solvents. In this research, nanolime dispersions have been further optimized for application on Maastricht limestone, a coarse porous limestone. Firstly, nanolimes were syn- thesized and dispersed in ethanol and/or water, both pure and mixed in different percentages. Subsequently, based on the kinetic stability of the nanolime dispersions, the most promising solvent mixtures were selected and applied on the limestone. The deposition of lime nanoparticles within the limestone was studied by phenolphthalein test, optical microscopy and scanning electron microscopy. The results confirm that nanolime dispersed in a mixture of ethanol (95 %) and water (5 %) can guarantee a better nanoparti- cles in-depth deposition within coarse porous substrates, when compared to dispersions in pure ethanol.@en