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San Jerónimo Monastery (Granada, Spain) was selected as a case study for the investigation of the effect of indoor environmental conditions on salt weathering and for on-site testing of a remediation treatment using crystallization inhibitors on account of the extreme salt damage affecting both the building stone, a biomicritic limestone, calcarenite and wall paintings. A methodology combining several analysis techniques, phenomenological observations, salt and moisture analysis, environmental monitoring and thermodynamic simulations, was adopted in order to study the salt damage problems affecting this building. Within the collected samples, the majority of salts were found to be magnesium sulphate in the form of either hexahydrite or epsomite, depending on the climate conditions, together with minor amounts of gypsum, nitrates and chlorides. Comparison of empirical observations with thermodynamic simulations of the salt mixture behaviour clearly showed that salt-induced damage events take place during the seasonal changes from spring to summer and winter to spring. An aqueous solution of an organic phosphonate, which in laboratory experiments was found to be an effective inhibitor of magnesium sulphate crystallization, was sprayed over a selected test area of unpainted stonework at the site. Preliminary results seem to indicate that after the application of the treatment both the amount of efflorescence and ongoing damage to the stone support is reduced. However, long-term monitoring of the future condition of the test area is needed to confirm whether indeed this treatment is appropriate and effective in reducing salt damage at this case study site. The outcome of this study extends beyond the particular problems at San Jerónimo Monastery, as it demonstrates a methodological approach for the study and evaluation of salt weathering problems affecting cultural heritage. [ABSTRACT FROM AUTHOR]

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: 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]

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]