Fabio Fratini

Ammonium Phosphates as Consolidating Agents for Carbonatic Stone Materials Used in Architecture and Cultural Heritage: Preliminary Research

Organic and inorganic consolidants display an unsatisfying behavior particularly in the case of artifacts highly porous stone in presence of soluble salts and water. Therefore, in this study of the mechanism for the consolidating action of ammonium oxalate, treatment with ammonium phosphate was considered. This product is very promising due to its high water solubility, absence of toxicity, and very low solubility of the reaction product, calcium phosphate. Tests were conducted on two kind of limestone applying a cellulose poultice with 5% water solutions of the following agents: diammonium hydrogen phosphate (DAHP) (pH 8.0), ammonium dihydrogen phosphate (ADHP) (pH 5.6–6.0), and ammonium-dihydrogen phosphate(ADHP) equilibrated with NH3 (30%) up to pH 7.0–8.0. Contact times of 4, 8, and 17 hours were used. The consolidating effect was evaluated with other parameters (water capillary absorption capacity, color variation), by comparison with the untreated samples and with the ammonium oxalate treatment. The results indicate a good consolidating efficacy, absence of significant color variation, and reduction of water absorption, making the ammonium phosphates greatly promising agents for the consolidation of artifacts made of porous carbonatic stones and plasters.

Ionoluminescence and Cathodoluminescence in Marbles of Historic and Architectural Interest

Ion beam induced luminescence (IBIL) was applied, along with cathodoluminescence (CL), on seven samples of marbles of historic and architectural interest. The CL colours, observed in a cold cathode device, have been related to the IBIL spectra. Moreover, a detailed analysis of the IBIL spectral features has made it possible to disclose the influence of the chemical composition and to emphasize the crystal-chemical role of the Mn 2+ . Beyond the chemical information and the crystal-chemical interpretation, the spectra are recognized as being valuable in the field of archaeological studies for their significance as fingerprints of marbles, giving information on their nature and origin.

Advanced mortar coatings for cultural heritage protection. Durability towards prolonged UV and outdoor exposure

In the present work, two kinds of hybrid polymeric–inorganic coatings containing TiO2 or SiO2 particles and prepared starting from two commercial resins (Alpha®SI30 and Bluesil®BP9710) were developed and applied to two kinds of mortars (an air-hardening calcic lime mortar [ALM] and a natural hydraulic lime mortar [HLM]) to achieve better performances in terms of water repellence and consequently damage resistance. The two pure commercial resins were also applied for comparison purposes. Properties of the coated materials and their performance were studied using different techniques such as contact angle measurements, capillary absorption test, mercury intrusion porosimetry, surface free energy, colorimetric measurements and water vapour permeability tests. Tests were also performed to determine the weathering effects on both the commercial and the hybrid coatings in order to study their durability. Thus, exposures to UV radiation, to UV radiation/condensed water cycles and to a real polluted atmospheric environment have been performed. The effectiveness of the hybrid SiO2 based coating was demonstrated, especially in the case of the HLM mortar.

Pietra Serena: the stone of the Renaissance

Abstract The most frequently used material in Florentine Renaissance architecture was Pietra Serena, a sandstone that nowadays is found in a quite satisfactory state of conservation. The reason for this is that architects and stone cutters in the past made careful selections of the materials they employed. This conscientious picking out was very important because most sandstone layers have a composition that is not always suitable for assuring an acceptable durability. This paper deals with the mineralogical, chemical, petrographical and physical characteristics of the Pietra Serena sandstone quarried in the hills near Florence in order to verify what was affirmed by Vasari (1568), Tuscan painter, architect and historian of art of the 16th century, and other Tuscan naturalists regarding the quality of this sandstone. As a matter of fact, analyses demonstrate that the Pietra Serena sandstones quarried in the hills of Settignano (to the northeast of Florence) and in the Gonfolina area (Lastra a Signa, to the west of Florence), are composed of layers particularly rich in calcite present mainly as sparitic cement. This calcitic cement gives great durability to the stone as is demonstrated by the good state of conservation of some Florentine monuments realized with Pietra Serena.

On-site evaluation of the ‘mechanical’ properties of Maastricht limestone and their relationship with the physical characteristics

Abstract Maastricht limestone is a soft bioclastic calcarenite of the Upper Cretaceous period cropping out in southern Limburg between Belgium and The Netherlands. This material was widely used from the Middle Ages to the Renaissance. Four different varieties can be distinguished according to fossil content and petrographic characteristics, which determine slight differences in compressive strength. Despite its poor mechanical characteristics, the material is very durable with remarkable frost resistance. This is mainly due to the pore dimensions (the most frequent pore radius class is 16–64 µm) but also to the particular kind of weathering that causes the formation of a protective ‘skin’ through a process of dissolution of unstable aragonite from serpulids and calcite precipitation in the pores of the external layer. The physical characteristics and the mechanical properties (using the drilling resistance measurement system (DRMS) method) of the hard layer that developed on the surface of Tongeren Cathedral, constructed using the Sibbe variety of Maastricht limestone, were investigated and compared with those of the quarry material. This comparison made it possible to emphasize the particular hardness of this surface in contrast to the outer layer of the quarry material. Moreover, it was possible to determine its thickness and to infer that this hard layer was formed after only 15 years of exposure.

Archaeometric study of natural hydraulic mortars: the case of the Late Roman Villa dell’Oratorio (Florence, Italy).

This paper shows the results of a multidisciplinary study carried out on the mortars from the Late Roman Villa dell’Oratorio (fourth-sixth ad), an aristocratic mansion built in the lower Valdarno (Florence, Italy). Thirty-one bedding mortar and plaster samples were analysed through optical microscopy, thermogravimetric analysis, X-ray powder diffraction and scanning electron microscopy with energy-dispersive X-ray spectroscopy for determining the chemical, mineralogical and petrographic characteristics, while their main physical properties were measured by geotechnical procedures. The collected data indicates that the analysed mortars are made up of very fine to coarse river sand aggregate mixed with white to yellowish-white natural hydraulic lime binder mainly consisting of mixtures of prevailing calcite and hydraulic compounds. With regard to the origin of the raw materials, the aggregates were recognized to be selected Arno river sands, and the binders are the burning product of a local marly limestone (ex Alberese). Therefore, the mortars of the Late Roman Villa dell’Oratorio are one of the first uses of natural hydraulic lime in the lower Valdarno.

The micro-sandblasting technique as a new tool for the evaluation of the state of conservation of natural stone and mortar surfaces

This work concerns a feasibility study about the possibility to evaluate the state of conservation of the monumental and historical stone and mortar surfaces with a micro-sandblasting system composed by a micro-sandblasting device and a micro-photogrammetry. The former creates a shallow crater on the surface operating at constant conditions (pressure of the jet, distance nozzle-surface), while the latter let us to quantify the volume of the crater through a 3D digital reconstruction. The work was focused on the validation of the methodology selecting the best operative conditions. To this aim, a set of tests were carried out on small glass specimens followed by tests made on natural stone materials and mortars. The results obtained have outlined the repeatability of the data and the possibility to discriminate among natural stone materials and mortar having different physical characteristics and mechanical behaviours.

On the role of hydrophobic Si-based protective coatings in limiting mortar deterioration

AbstractIn order to avoid both natural and artificial stone decay, mainly due to the interaction with atmospheric pollutants (both gases such as NOx and SO2 and particulate matter), polymeric materials have been widely studied as protective coatings enable to limit the penetration of fluids into the bulk material. In the current work, an air hardening calcic lime mortar (ALM) and a natural hydraulic lime mortar (HLM) were used as substrates, and commercially available Si-based resins (Alpha®SI30 and Silres®BS16) were adopted as protective agents to give hydrophobicity features to the artificial stones. Surface properties of coatings and their performance as hydrophobic agents were studied using different techniques such as contact angle measurements, capillary absorption test, mercury intrusion porosimetry, surface free energy, colorimetric measurements and water vapour permeability tests. Finally, some exposure tests to UV radiation and to real polluted atmospheric environments (a city centre and an urban background site) were carried out during a wintertime period (when the concentrations of the main atmospheric pollutants are higher) in order to study the durability of the coating systems applied. The effectiveness of the two commercial resins in reducing salt formation (sulphate and nitrate), induced by the interaction of the mortars with the atmospheric pollutants, was demonstrated in the case of the HLM mortar. Graphical Abstractᅟ

The ancient gypsum mortars of the historical façades in the city center of Valencia (Spain)

In the historical centre of Valencia (Spain), the brick facades of the residential buildings which were built or modified in the end of the XVIII th century and the beginning of the XX th century have been protected and decorated with continuous renderings. According to the constructive tradition, the renderings had to be made with lime mortars, but the recent studies allowed to know their real nature: they are gypsum mortars. The main aim of the study has been to know the nature and the technical aspects of the historical renderings of the facades of the centre of Valencia, in order to discover their secrets from a theoretical and experimental point of view. Therefore, together with the examination of bibliographical sources, several samples of the historical mortars have been collected from renderings. The analytical results confirm that the great majority of samples are composed by gypsum mortars, with different degrees of purity and a variable amount of aggregate and lime. Some samples are mixed mortars (gypsum and lime mortars), but there are also examples of pure lime mortars probably indicating a change in the constructive tradition of the city in a historical moment as testified by the presence of buildings with brick walls bonded with lime mortar and gypsum mortars in the rendering. This fact supposes a conscious application of the gypsum in exteriors and the existence of a specific ancient technique. Moreover the analysis of the surfaces of renderings characterized by a specific finishing and several layers of painting, allows us to confirm that organic substances have been applied in order to protect the gypsum mortars from the inclemency of the weather. Definitively, the characterization of the gypsum mortars that cover the historical facades of the centre of Valencia allowed us to discover a particular and distinguishing aspect of the constructive tradition of the city that must be protected and valued in order to achieve its preservation.

Ancient stone masonry constructions

Abstract A very large part of the vernacular built heritage consists of masonry buildings. This heritage needs to be protected and enhanced as it participates in preserving the cultural identity of a community and contributes to extending the value of stone resources for sustainable and eco-friendly new buildings. In this chapter, the masonry construction is analyzed at different scale levels: compositional and mechanical characterizations of materials, descriptions of wall types, mechanical performance of masonry structures, environmental performance of masonry constructions, and innovative applications in modern architecture.