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Architectural Engineering +Technology, Architecture and The Built Environment

The development of nanomaterials is growing exponentially in the last decade. New discoveries and their applications have taken place in different fields, such as electronics, chemistry, biology and physics. Some innovative nanoproducts have become available also for the conservation of cultural heritage (e.g. nano-Ca(OH)2, nano-SiO2, nano-TiO2, CNTs, etc.), showing interesting potentialities and advantages. However, there are also drawbacks. Extensive literature is available on nanolimes, i.e. colloidal alcoholic dispersions of Ca(OH)2 nanoparticles, which are promising materials for the consolidation of lime-based plasters and calcareous stone, often present in ancient masonry structures. Nanolimes have several advantages such as high stability, fast carbonation rate and good chemical and physical compatibility with calcareous stone and lime-based plasters. However, in comparison to other existing consolidant products, like TEOS-based (Tetraethylorthosilicate), the penetration depth of nanolime is often limited, which may consequently result in a low effectiveness. The research presented in this paper aimed at understanding the penetration and deposition process of nanolime when applied in Maastricht limestone, a soft, highly porous substrate, widely used in the Dutch and Belgian provinces of Limburg. This research focused on the nanolime transport process to clarify whether nanolime is able to penetrate and deposit in depth in the material or if it simply accumulates near the surface. In order to investigate the distribution and particle size of nanolime deposited in the stone, next to simple phenolphthalein tests, optical microscopy, AFM and SEM-EDS were used. On the basis of the obtained results, the transport and deposition of a commercial nanolime in Maastricht limestone has been elucidated. The comprehension of the nanolime transport mechanism (penetration and distribution) within the treated material is crucial for improving the effectiveness of this consol, Architectural Engineering +Technology, Architecture and The Built Environment

Architectural Engineering +Technology, Architecture and the Built Environment

Architectural Engineering +Technology, Architecture and The Built Environment

Architectural Engineering and Technology, Architecture and The Built Environment

The use of crystallization modifiers for the prevention or mitigation of salt crystallization damage has recently received a lot of research interest in the field of building conservation. However, the use of crystallization modifiers mixed in a lime-based mortar, is still a very new field of research. This paper summarizes the literature study aimed at the identification of a possible modifier for sodium sulfate, one of the most damaging salts found in porous building materials. Furthermore, the results of preliminary experiments conducted in order to test the suitability of borax as a crystallization modifier for sodium sulfate are reported and discussed., Architectural Engineering +Technology, Architecture and The Built Environment

Salt crystallization is a major cause of damage in porous building materials. Notwithstanding the extensive research in this field, the complexity of the problem has hindered the use of mathematical models for forecasting ageing and damage due to salt crystallization. Nowadays, the durability of materials with respect to salt crystallization is mostly determined by accelerated ageing tests, carried out in laboratory following different test procedures. An effective ageing test should simulate in laboratory, in a reliable way and within a relatively short period of time, the behaviour in practice. The question is whether existing test procedures are able to do so. This paper reports a critical overview of existing procedures and suggests directions for further research., Architectural Engineering +Technology, Architecture and The Built Environment

The weathering of porous materials due to the presence of salts has been known since antiquity. However, serious studies and investigations were not conducted until the 19th century. One of the fi elds of interest includes historic masonry, where salt damage can affect natural stone, brick and mortar (see Figure 1). Mortars are building materials, which are for example used in masonry, as the bonding material in between bricks or stones or as a plaster or render. Because of its pore size distribution (with both coarse as fi ne pores) and its relatively low mechanical strength, mortar is one of the building materials most affected by salt crystallization damage. As a consequence, replacement of plasters, renders and pointing mortars often constitutes a large part of total restoration costs. Salts present in masonry can originate, amongst others, from sea salt spray, rising damp, road salt, salt storage and the building materials itself., Architectural Engineering + Technology, Architecture and The Built Environment

Salt crystallization damage is one of the most common causes of decay for bedding, pointing and plastering mortar. Attempts to tackle the problem have been mainly focused on increasing the mechanical strength of the mortar, by the replacement of lime with (PTL) cement, or on reducing the moisture transport capacity, by the addition of silicone based water repellents. Both solutions showed to often have a limited durability to salt decay and a low compatibility with historical buildings. Recently research has started to explore new possibilities for improving the durability of mortars to salt damage; these include engineering of the pore size, replacing of silicone based additives with natural organic water repellent substances and mixing-in of salt crystallization inhibitors able to reduce the harmfulness of salt crystallization. Some preliminary studies show that these directions can be promising for obtaining more durable mortars, compatible with historical buildings., Architectural Engineering and Technology, Architecture

Rising damp is one of the most recurrent and well-known hazards to existing buildings and monuments. Several types of intervention exist to tackle the problem. Among these, the creation of a damp-proof course against capillary rise by means of injection of chemical products is one of the most diffused methods, thanks to the relatively easy and cheap application. Despite positive results when applied under controlled conditions in laboratory, these interventions do not always deliver the desired result in practice. Several studies have shown varying degrees of success. Various factors, like the lack of homogeneity of the substrate and a high moisture and salt content may affect the effectiveness of treatments. Moreover, the type of substrate and the combination of materials with different pore size distribution influence the spreading and the effectiveness of chemical products. Since rising damp is a problem that is mainly manifested in masonry, that is usually composed of at least two materials, the last factor may be of great importance. The current paper reports the results of a research on the transport of chemical injection products in relatively small mortar/brick combinations. Since no easy to perform test method for small combined specimens, giving results within a short time, was available, a special test method was developed. The effect of the interface between brick and mortar on the transport of the products was studied by the application of several injection products and creams. The tested products include pore filling and water repellent products and products in water as well as in organic solvent. The obtained results show clear differences in spreading and effectiveness in the different substrates and between products in organic solvent and water based ones, as well as between creams and liquid products. The results show that water based products can easily be transported through the mortar joint, differently from what occurs with products in an organ, Architectural Engineering +Technology, Architecture

Salt crystallization constitutes one of the most widespread decay mechanisms affecting historic buildings. Desalination is a conservation treatment of growing importance in the case of historic masonry. Salts present in porous materials cause damage through their interaction with moisture. Consequently, in certain situations the prevention of further moisture ingress can provide a solution to the problem. However, damage can also occur due to the hygroscopic uptake of moisture from the air by the salt. Hygroscopic salts can dissolve and re-­crystallize due to changes in air humidity (RH) that cross their equilibrium relative humidity value. In this case, climate control may provide stable RH values and thus avoid cycles of crystallization/dissolution. However, the desired climate for preservation is not always easy to be obtained in ancient buildings. In such situations, direct intervention in the form of desalination treatments may present a better solution to the problem. This paper describes the approach from pre-investigation and treatment to follow-­up care as the basis for a successful conservation of monuments suffering from salt decay. The necessity to tune the poultice properties to the substrate is underlined., Architectural Engineering and Technology, Architecture

Metselwerk kan zwaar te lijden hebben onder verschillende degradatieprocessen. Bij veel van deze degradatieprocessen speelt vocht een grote rol. Eén van de belangrijkste en tegelijk vaak moeilijk te bestrijden vochtbronnen voor metselwerk is optrekkend vocht. Men spreekt van optrekkend vocht als water vanuit het grondpakket via de capillairen van steen en mortel tegen de zwaartekracht in omhoog gezogen wordt. Bij een geschikte combinatie van steen en mortel kan optrekkend vocht zowel in oudere als jongere gebouwen voorkomen. De kans dat het hoger optrekt als gevolg van langdurige toetreding van zouten is bij oudere gebouwen groter., RMIT and Media Studies, Architecture

Zoutkristallisatie is een van de meest voorkomende bedreigingen voor historische gebouwen. Zouten, aanwezig in poreuze materialen kunnen in interactie met vocht schade veroorzaken. Omdat vocht essentieel is voor dit schadeproces, kan onder sommige omstandigheden een ingreep, die verdere vochttoetreding tegengaat, een oplossing voor het probleem betekenen. Wanneer het materiaal al een aanzienlijke hoeveelheid zout bevat, kunnen echter zelfs wisselingen in de RV van de omgevingslucht nog kristallisatie en oplossingscycli teweeg brengen en daarmee schade veroorzaken. Maatregelen als ontzouten kunnen dan overwogen worden., RMIT and Media Studies, Architecture

Ontzouten door het gebruik van kompressen is een techniek die meer en meer gebruikt wordt in de conservering van historisch metselwerk. Niettemin, wordt ontzouten nog vaak uitgevoerd op een trial and error basis, zonder wetenschappelijke kennis van de processen die vocht- en zouttransport regelen. Om het ontzoutingsproces te optimaliseren is, binnen het Europese project Desalination, een modulair systeem van kompressen ontwikkeld. Dit is gebaseerd op het afstemmen van de porieverdeling van de kompressen op die van de ondergrond, om ontzouting op de meest efficiënte manier te bereiken. Deze aanpak is in de praktijk gebruikt bij het ontzouten van twee belangrijke monumenten: de meesterproeven in het Waag gebouw te Amsterdam en bij voorbereidende proeven aan de Porticus van het Rubenshuis te Antwerpen. In beide gevallen zijn bevredigende resultaten bereikt., RMIT and Media Studies, Architecture

In the present research a test procedure was set up to reproduce self-healing on lime-based (both pure calcium and magnesium-calcium) mortar specimens in laboratory. After few months testing, during which the specimens were subjected to wet-dry cycles, thin sections of the specimens were prepared and observed by Polarization and Fluorescence Microscopy (PFM) and by Scanning Electron Microscope (SEM) equipped with Energy-dispersive X-ray spectroscopy (EDX). The specimens prepared with dolomitic lime showed the occurrence of self-healing: a magnesium compound is observed filling cracks and voids. These results suggest new possibilities for the development of dolomitic lime mortars with an increased self-healing capacity., RMIT and Media Studies, Architecture

Lime mortars have, up to a certain extent, a self-healing capacity which may contribute to their durability. Self-healing in lime mortars consists of a process of dissolution, transport and re-precipitation of calcium compounds to heal cracks and fissures. The spontaneous occurrence of self-healing in lime-based mortars is a well known phenomenon; to date, however, little research has been done on its occurrence in the practice. This study aims at gaining a better understanding of the self-healing mechanism in lime-based mortars through the investigation of case studies where self-healing has been observed. On the basis of the results obtained the relevance of the various controlling factors, the way in which they potentially interact, and how they affect the occurrence of self-healing is evaluated. Lime-based mortar samples collected from several case studies were studied. Thin sections were prepared and studied by means of Polarization & Fluorescence Microscopy (PFM). The influence of selected parameters (moisture content, degree of carbonation, binder-sand ratio, binder type, etc.) on the nature (calcium carbonate or calcium hydroxide) and crystal habits of the precipitated products has been investigated. The results obtained indicate that some recurrent patterns exist in the nature and the crystal habits of the re-precipitated products depending, among other factors, on the moisture content and on the degree of carbonation of the mortar.

Zoutkristallisatie kan leiden tot ernstige aantasting van steen en metselwerlk. Dit veelvoorkomende probleem vormt bij de zorg voor monumenten een blijvend punt van aandacht. In dit artikel wordt beschreven hoe het mechanisme van zoutkristallisatie werlct en ook op welke manieren zoutkristallisatie zich manifesteert. Het grote aantal factoren dat het schadebeeld kan beïnvloeden, maalktt het soms lastig om de oorzaak van het probleem te achterhalen. Van geval tot geval moet bekeken worden welk soort materiaaltechnisch onderzoek en welk soort onderzoek naar de herkomst van vocht en zouten noodzakelijk is., RMIT and Media Sciences, Architecture

RMIT and Media Studies, Architecture

Salt crystallization constitutes one of the most widespread decay mechanisms affecting historic buildings. Desalination is a conservation treatment of growing importance in the case of historic masonry. This paper describes the approach from pre-investigation and treatment to follow-up care as the basis for a successful preventive conservation of monuments suffering from salt decay., Architectural Engineering and Technology, Architecture

San Jeronimo 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 Jeronimo Monastery, as it demonstrates a methodological approach for the study and evaluation of salt weathering problems affecting cultural heritage., RMIT en Media Studies, Architecture

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