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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. [ABSTRACT FROM AUTHOR]

Abstract: Clays often constitute the main component of poultices used for salt extraction from porous materials in conservation intervention. Knowledge of the evolution in porosity and pore size of clay based poultices, due to shrinkage during drying, is of crucial importance for the selection of the most suitable poultice. We have studied the porosity and pore size distribution of kaolin and bentonite based poultices at different moisture contents. Both Mercury Intrusion Porosimetry (MIP) measurements on freeze-dried samples and cryo-FIB–SEM observations on wet samples are employed. The results show that these complementary techniques provide complete information on the porosity, pore size and pore structure of clay materials at different moisture contents. Both kaolin and bentonite poultices show a change of their total porosity and pore size distribution during drying: the changes are moderate in the case of kaolin, whereas the changes are very significant in the case of bentonite. These findings underline the necessity, when selecting a desalination poultice, of taking into account possible changes in its pore size distribution during drying, since these changes may affect the effectiveness of the salt extraction. Our results indicate that the good desalination efficiency of kaolin on substrate of pore size between 1 and 10μm observed in practice is related to the presence in the poultice of pores that are very effective in capillary transport (0.2–2μm) and to the relatively constant pore size distribution of the poultice during drying. [Copyright &y& Elsevier]

Abstract: Injection of chemicals in masonry walls is a commonly used technique for tackling rising damp. The presence of a high moisture content in the wall to be injected may sometimes limit the effectiveness of the intervention. This paper reports an experimental study of curing time, spreading and effectiveness of 15 injection products in bricks with different water saturation degrees. Significant differences in curing times and percentages of components left after curing were observed among products. The spreading and the effectiveness of products in (wet) substrates resulted to strongly depend on the solvent and, in a lesser way, on the active components. Liquid water based silane/siloxane products showed to spread homogeneously and reduce water uptake the most. [Copyright &y& Elsevier]

Abstract: Salt crystallization is a common cause of damage to porous building materials. Recent research has shown that some chemical compounds may inhibit salt crystallization or alter the mode of crystallization, thus limiting salt damage development, provided that the inhibitor was introduced prior to salt crystallization. In this paper, a pilot study is presented in which sodium ferrocyanide, a crystallization inhibitor for sodium chloride, has been mixed in a lime-cement mortar. Salt resistance of the mortar has been tested by means of a crystallization test. The results of the crystallization test show that the addition of the inhibitor significantly improves the salt resistance of the mortar. Scanning electron microscope observations carried out on the surface of the cross section of the specimens demonstrate that the inhibitor modifies the habit of the salt crystals, as well inhibits the development of specific crystal faces. [ABSTRACT FROM AUTHOR]

Abstract: In recent years several types of restoration plasters, especially developed for salt loaded substrates, have been introduced on the market. The behaviour of these plasters in the field is, however, not always satisfactory. The reasons for failures may be found both in the moisture and salt transport behaviour of the substrate/plaster combination and in the severity of the situation (salt load, moisture supply and environmental conditions). In the present paper a restoration plaster for salt loaded substrates is examined. Its properties and composition are investigated in laboratory by means of multiple techniques (MIP, PFM, ESEM, XRD and FTIR). Particular attention is given to the study of the salt (NaCl) crystallization in the plaster. Field situations are considered in which this plaster shows damage after a few years from its application. The knowledge of the specific situation, together with the information gained in the laboratory research on the plaster, explains the fast development of the decay. [Copyright &y& Elsevier]

Abstract: The mechanism of damage occurring in NaCl contaminated materials has not been clarified yet. Apart from crystallization pressure, other hypotheses have been proposed to explain the cause of decay. Irreversible dilation has been observed in a few cases but has never been studied in a more systematic way. The aim of the research is to contribute to the modeling of this phenomenon. In the present paper the effect of NaCl on the hydric and hygric behavior of a lime–cement mortar is extensively studied. The results indicate that NaCl influences the hydric and hygric dilation behavior of the material. The material contaminated with NaCl shrinks during dissolution and dilates during crystallization of the salt. This dilation is irreversible and sufficient to damage the material after few dissolution/crystallization cycles. This behavior is not restricted to NaCl, but is observed in the presence of other salts as well (NaNO3 and KCl). Outcomes of electron microscopy studies suggest that salts causing irreversible dilation tend to crystallize as layers on the pore wall. [Copyright &y& Elsevier]

Salt crystallisation is one of the main causes of masonry decay in monuments. The salt content in a wall is a very important parameter that should be known in order to give a reliable diagnosis on the causes of damage; if a restoration work and a surface treatment are necessary, the salt content has to be known. In fact the presence of salts in the wall can not only reduce the efficiency of a treatment but also form a potential risk for the occurrence of a damaging salt crystallisation process. Different methods and instruments are available to detect salt content and type of salt present, but most of them are quite expensive and time consuming. For this reason, other methods, cheaper and quicker, are preferably adopted. In building practice often the hygroscopic moisture content of powder samples is measured in order to have an indication of the salt content. This method is cheap and simple and, in case of material contaminated with a single salt, gives reliable results on the quantity of salts present because of the linear relation between HMC and salt content. However, in case a mix of salts is involved, as usual in reality, the relation between the HMC and the salt content is not clear yet and the HMC measurement can give only an indication and not a quantitative value of the salt content. This paper presents the experimental results of a research carried out on the hygroscopic behaviour of sodium salts introduced in a typical clay-brick either as single salts or as a mix. The obtained results point out a clear linear relation between salt content and hygroscopic moisture content. This proportionality is verified for (brick) specimens contaminated with pure salts as well as with salt mixtures. Salt mixtures appeared to correspond with hygroscopic moisture contents that are higher than the one calculated according to the amount of single salts present in the mixture. As expected beforehand no difference was found between the hygroscopic behaviour of solid brick specimen and brick powder, only a longer time to reach equilibrium in case of brick powder. This paper suggests in the case of the presence of single salts to use the HMC measurement instead of more complicate and expensive analyses (as for example in laboratory experiments). In building practice, the measurement of the HMC can help in selecting the most interesting spots on which to focus the research avoiding extensive campaigns of sampling and analyses. Besides, HMC measurements performed at different RH, can give suggestions about the type of salt present. [Copyright &y& Elsevier]

• Moisture transport of brick-mortar combination is crucial for bioreceptivity. • The composition of the mortar strongly affects its bioreceptivity. • Lime-trass and, in lower extent, NHL binders show the best bioreceptivity. • A compromise is needed between bioreceptivity and mechanical strength. The effect of mortar and brick properties on the growth of ivy-leaved toadflax (Cymbalaria muralis) and yellow corydalis (Pseudofumaria lutea) has been investigated in laboratory. Different mortar compositions were designed and tested in combination with two different bricks. Highly porous bricks and mortars showed good bioreceptivity; mortars with lime-trass and, in lower extent, those with natural hydraulic lime binder, gave the best results in terms of bioreceptivity. The addition of vermiculite to the mortar was beneficial for plant growth. The brick-mortar combinations most favourable for plant growth were those with estimated low compressive and flexural bond strength values. Proposals are advanced for obtaining a compromise between mechanical strength and bioreceptivity. [ABSTRACT FROM AUTHOR]

Rising damp is a recurrent hazard to ancient buildings in Europe and its relevance is expected to increase in the future, due to climate changes. The presence of rising damp in walls does not only create an unpleasant climate in buildings, but it also enhances damage processes such as frost action, salt crystallization and biological growth, with possible consequences on the health of the inhabitants. The relevance of this problem is reflected by the large variety of products on the market. The wide and differentiated offer and the scarce scientific information on the effectiveness of the methods make it difficult, (even) for professionals working in the field, to choose a suitable intervention on a sound basis. The JPICH-financed project EMERISDA (2014–2017) [1] aimed at evaluating the effectiveness of different intervention methods against rising damp. The project involved universities, research institutes, heritage agencies and companies (producers and contractors) in Belgium (BBRI, co-ordinator), Italy (CNR-ISAC, Universita’ Ca’ Foscari Venezia, Restauri Speciali s.r.l., Diasen s.r.l.) and The Netherlands (Delft University of Technology and the Cultural Heritage Agency of the Netherlands). The research methodology included the use of an on-line questionnaire and experimental research in laboratory, on scale models and on-site. Both traditional methods, such as chemical injection, and more recent techniques, such as the so-called “electro-physical” methods have been investigated. [2] The following results of the EMERISDA project are presented in this paper: - Results from on-line questionnaire. - Definition of an experimental procedure for the assessment of the presence of rising damp and of the effectiveness of the intervention. - Prototype of decision support tool, which provides insight into the feasibility and risks of existing methods against rising damp and supports actors involved in conservation in the choice and application of the methods against rising damp. [ABSTRACT FROM AUTHOR]