Elisabetta Zendri

Advanced Byzantine cement based composites resisting earthquake stresses: the crushed brick/lime mortars of Justinian's Hagia Sophia

Abstract Structural studies to determine the earthquake worthiness of Hagia Sophia in Istanbul have proved that the monuments static and dynamic behavior depends very strongly on the mechanical, chemical and microstructural properties of the mortars and bricks used for the masonry. Hence, the classification of the crushed brick/lime mortars under the category of advanced cement-based composites is concluded, explaining the fact that the monument still stands, as well as the very large static deformations which it has undergone, since such mortars have a very long curing period. According to the analysis of the dynamic data, the first three natural frequencies of the building were determined. These results show a decrease of approximately 5–10% in the natural frequencies, as the amplitude of the accelerations increases and returns to their initial values, due to the non-linear nature of the masonry. The above-mentioned behavior allows the structure to absorb energy without affecting irreversibly its material properties. The determination of the mortar properties indicated that they are of considerable mechanical strength and longevity. The dated mortar samples examined proved to be resistant to continuous stresses and strains due to the presence of the amorphous hydraulic formations (CSH), investigated by transmission electron microscopy (TEM) at the crushed-brick powder/binder interfaces and at a sufficient content in the binding matrix, as proved by TG-DTA, which allowed for greater energy absorption without initiations of fractures, let alone the transition of the gel to a higher order of formation. Furthermore, the interpretation of the amorphous nature of the hydraulic formations of the crushed brick/lime mortars is attempted by the experimental validation of real chemical interaction between lime and clay and the characterization of the fundamental structural units of the calcium silicate hydrates, produced by mass spectroscopy.

Characterization of binders employed in the manufacture of Venetian historical mortars

Abstract This research focuses on the characterization of historical mortars collected from a covered dockyard, called tezone 105, erected in the Arsenal of Venice during the XVI century. The mortars date back to different building phases. A stratigraphical analysis of tezone 105 has proposed a chronology of building interventions. The building phases recognized by the stratigraphical analysis belong to the original structure (XVI century) and to later interventions from XVI to XX century. Mortar samples are investigated by granulometric analysis, infrared spectroscopy (FT-IR), simultaneous thermal analysis (DSC/TG) and X-ray diffraction analysis (XRD) in order to identify the technology peculiar of each building phase. Mortar sampling was carried out on indoor masonry and foundation. Masonry mortars appeared to be characterized by the application of air-hardening binders, whereas foundation mortars were characterized by hydraulic binders.

Thermoanalytical research on traditional mortars in venice

Abstract The study of traditional mortars has recently been attracting considerable attention, in connection with both diagnosis and applications required for restoration. The mortar is only apparently a simple system; in reality the lime is often accompanied by hydraulic components. The inerts often interact with the binder and the technologies used in the application are very diversified. These situations make the study of the mixtures rather complex, as it is difficult to distinguish the neoformation compounds from the older ones. A basic approach is offered by granulometric analysis, allowing separation of the mortar into its components, in which the finer fraction is richer in binder. Some analyses on this fraction ( μ m) were performed to define the nature and quantity of the binder in the mortar. Samples were taken from various sites in Venice and were examined by calcimetry, TG-DTG and FTIR analysis. Moreover the investigation of this fraction by optical microscopy enabled us to distinguish the binder from the inert particles.

Characterization of the lumps in the mortars of historic masonry

The present work focuses on the investigation of mortar joints of historic masonries consisting traditionally of aerial binder and inerts which contain lumps. The presence of lumps, usually white in colour and of various dimensions, was often recorded inside these mixtures and does not appear to be random, as they are rather frequent, These lumps could confer some physicochemical properties to the mixture, that favour the overall compatibility of the system. For this purpose, various samples taken from historic Venetian masonry were examined by TG-DTG and FTIR analysis. Moreover SEM and fibre optical microscope observations were performed. The results indicate mainly the presence of completely carbonated lime and lead us to assume that the lumps arise from technologies based on the non-seasoning of the lime.

Interaction between clay and lime in “cocciopesto” mortars: a study by 29Si MAS spectroscopy

Abstract The structure of historical “cocciopesto” mortars (utilized in Venice and more generally in the Mediterranean area) have been mimicked with samples of phyllosilicate rich (by 58%) clay heated at different temperatures (between 500 and 700 °C) and treated with lime over a 5-month seasoning period in the air (in the presence of CO2) or alternatively under N2 atmosphere (in the absence of CO2). The structural transformations have been detected with 29Si MAS NMR spectroscopy. Heating converts the crystalline Q3 phyllosilicates into the amorphous Q3am phase. The Q3am phase is partially converted by lime in the presence of CO2 into amorphous Q2am inosilicates, while the Q3 phase remains unchanged. In the absence of CO2, lime converts swiftly the Q3am phase (and more slowly the Q3 phase) into the crystalline Q2 inosilicates and Q1 sorosilicates. As the conditions encountered by historical “cocciopesto” mortars during their secular seasoning are better mimicked by clay treated with lime in the air, the hydraulic properties of the former material are temptatively attributed to the presence of the Q2am phase.

Quantitative determination of un-derivatised amino acids in artistic mural paintings using high-performance liquid chromatography/electrospray ionization triple quadrupole mass spectrometry

The tempera painting technique is one of the most common methods used throughout art history. Tempera is defined by the type of binders used and in this work we study protein-based temperas. Proteinaceous binders can be characterized by the chromatographic determination of the amino acids present where techniques are either based on gas chromatography or high-performance liquid chromatography (HPLC) coupled to mass spectrometry. The objective of this work was to develop a derivatisation-free HPLC method with triple quadrupole tandem mass spectrometric detection (HPLC/ESI-MS/MS) of 21 amino acids contained in the protein-based binders of tempera paints. The analytical method identifies the painting techniques of two contemporary artists: Sironi and DeLuigi. The sample data are compared to painting material standards. The results show that the samples from works by DeLuigi contain mainly animal glue binders, while the samples from Sironi paintings contain binders that are an amino acid mixture with an overall composition between that of eggs and casein.

Hot lime technology imparting high strength to historic mortars

Abstract In previous works the mineralogical and physico-chemical properties of crushed brick-lime mortars in response to stresses, simulating earthquakes or dynamic soil structure interactions, were studied. It was proved that the effective mechanical properties of the mortars could be attributed to the alkali-silicate reactions occurring at the brick fragment-lime interface. Since the category of the pozzolanic mortars presents a wide spectrum, spanning from the crushed brick to various cementitious mortars, the idea was to study the effectiveness of other hydraulic mortars as well. The Symonos Petra Monastery at Mount Athos was selected for investigation as pilot monument, because in our previous works it was found to be scientifically sound. The mortars were analysed following a procedure correlating chemical and instrumental analysis to determine CaCo 3 CaOsil . TA, IR, SEM and EDX were performed and tensile strength and adhesion was measured. The amounts of Ca ++ and Mg ++ were determined by AAS. Old mortars, from the Arsenal tower (16th c.) present higher tensile strengths than traditional hydraulic lime mortars and are effective against dynamic stresses exerted onto the greater Serbomacedonian mass as well as against the intense marine environment. Fine ground magnesium-alumino-silicate dust of the montmorillonitic clays in the area could have been mixed in a ratio of 2 ( 1 5 ) of lime/‘pozzolanic’ or active clay admixtures/inert aggregates reacted with the in situ slaked lime, their hydraulic components augmenting considerably with Mg ++ . Hence Arsenal mortars present an intermediary between Roman and modern concrete for marine structures produced by hot lime technology.

Modern Oil Paints – Formulations, Organic Additives and Degradation: Some Case Studies

This study examines some of the degradation phenomena exhibited by modern oil paintings and twentieth century oil paint formulations and possible correlations with the various organic additives typically introduced by manufacturers. The research takes into consideration historical and modern tube oil paints produced by different European manufacturers and selected twentieth century oil paintings which showed degradation problems such as efflorescence, softening, cracks and sensitivity towards water and polar solvents. The composition of oil paints and paintings samples was studied with XRF, SEM-EDX, ATR-FTIR and GCMS. The results showed that both artists’ oil paints and paintings samples contain a complex mixture of additives to the oil binders and pigments. The presence of aluminium and zinc stearates, added as dispersion agent gelling agents, was detected in most paint formulations of HKS, W&N, Talens and Maimeri (c. 1940-present). Several paint films showed an unusually high content of fatty diacids, suggesting that, in drying, an oxidative reaction was favoured above polymerisation. This occurrence, together with the diversity of lipidic media, additives, pigments and driers present in the industrial formulations could play a crucial role in paint failure and instability, as showed by the analysed case studies. The obtained results may help understanding the behaviour of modern oil paints and painting surfaces and contribute to improved conservation methods.

Effects of condensed water on limestone surfaces in a marine environment

Abstract We have evaluated the effects of condensed water on limestone surfaces through a procedure that foresaw the cooling of the samples before their exposition to the open air, so that the condensation phenomena could occur easily. The effects of the condensed water were evaluated by measuring the weight change of the samples, through SEM observations and analysis of the 3-D profile, using laser profilometer. The results show the weak action of condensed water on the stone surface, particularly if compared with that of rain.

Chemico-Physical Interactions Among the Constituents of Historical Walls in Venice

Investigates the possible chemical interactions between the constituents of historic walls. In Venice, but also in the whole Mediterranean area, the cocciopesto (consisting of brick and powder fragments which traditionally confer hydraulic properties to the mortar) has been widely employed both for mortars and the so-called marmorino plasters. An examination of the brick-mortar interaction on historic buildings in Venice was carried out. The samples were chemically analyzed through x-ray photoelectron spectroscopy (XPS) and XPS-imaging techniques in order to ascertain the chemical composition of the interface layers. The results clearly indicate that a true physicochemical interaction between brick and lime is present in the historic materials. A calcium carbonate accumulation has been observed at the brick-mortar interface. -- AATA