G. Zappia

Atmospheric deterioration of ancient and modern hydraulic mortars

Different types of ancient and recent hydraulic mortars were collected from well-documented archaeological, historic and modern buildings in various geographical locations (urban, suburban, rural and maritime) of Italy, Spain and Belgium, representative of different environmental impacts, types and degrees of deterioration. A synthesis of the characteristics of the collected samples is presented, along with the identification of the formation products that occurred on the sample surfaces as a result of the reaction of the mortars with atmospheric pollutants. The analyses were performed by means of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM-EDX) and ion chromatography (IC). The results obtained prove that sulphation processes takes place on hydraulic mortars, leading to gypsum formation on the external surface of the samples. Through the reaction of gypsum with the aluminate hydrate of the binder, ettringite formation was found to occur on a cement-based restoration mortar sampled in Antwerp.

Determination of elemental and organic carbon on damaged stone monuments

An analytical methodology was developed for the discrimination and evaluation of the different types of carbon matter, particularly carbonate, elemental and organic carbon, present on monuments and historical buildings, due to interaction between materials and atmospheric pollution. With this aim samples of black patinas were analysed by a procedure consisting of three different steps. Total, noncarbonate and elemental carbon were measured by combustion-chromatographic CO2 determination: Ct was obtained by burning the bulk samples (step 1), while Cnc and Ce were quantified after elimination of Cc with acid treatment (step 2) and elimination of Co by means of alternate attacks, followed by centrifugation, with concentrate acid and base solutions at high temperature and pressure (step 3); the carbonate carbon and the organic carbon were then calculated. Furthermore, for a complete sample characterization, oxalate, acetate, formate and the main anion contents were detected by ion chromatography. The methodology was also tested on standard samples containing the same carbon species as the black crusts. The results obtained indicate that this approach satisfactorily distinguishes between elemental and organic carbon and allows reliable elemental carbon determination at the ppm level in black damage crust samples from historic monuments and buildings.

Black crusts on ancient mortars

Samples of mortar damage layers found on ancient masonry have been analysed. The paper presents the characterisation of the black crusts, which are the accumulation areas of material damage and atmospheric deposition, and includes a complete identification of the sulphur, nitrogen and carbon compounds. The presence of anthropic aerosol and its role in the process of damage is evidenced.

Sulphite quantification on damaged stones and mortars

Abstract An analytical procedure was developed for the simultaneous identification and quantification of the sulphite and main anions found in degradation patinas on historic buildings and monuments, as well as on stones and mortars exposed in simulation chamber and field tests. The quantification of anions was performed by means of ion chromatography (IC), after the stabilisation of sulphite with aD(−) fructose solution. The utilisation of two different chromatographic columns, connected in series, allowed the simultaneous determination of fluoride, acetate, formate, chloride, nitrite, bromide, iodide, oxyhalides, nitrate, phosphate, sulphite, sulphate and oxalate, in a time of approximately 25 min, without interference and with high reproducibility. Finally, the results show how in the majority of cases the formation of sulphite is an intermediate stage in the sulphation process affecting building materials exposed to the environment and needs to be measured together with sulphate, in order to obtain a correct interpretation of degradation mechanisms on such materials.

Environmental Deterioration Of Ancient AndModern Hydraulic Mortars

Little is known about the nature and durability of hydraulic mortars in ancient buildings. Furthermore, the characterisation of the type of binder is important in order to proceed to the design of conservation interventions. A procedure has been set up to identify the type of binder used in historic hydraulic mortars. A number of mortars has been sampled from historic buildings, on which analyses have been performed to verify the set up methodology and evaluate their deterioration due to environmental deposition. Being sulphation one of the most important mechanisms of degradation found on historical buildings, SCV exposure tests were performed on different replicas of hydraulic mortars. The formation of sulphur containing species, such as gypsum, ettringite and thaumasite, has been studied in controlled conditions. The results obtained prove that the sulphation occurs on hydraulic mortars, depending on the composition of the binder. Transactions on the Built Environment vol 39

Anion determination in damage layers of stone monuments

Abstract An analytical procedure was set up for the dissolution of damage layers from stone monuments with the aim of performing ion chromatography analyses. The dissolution was performed using ion exchange resin H-form and the ion chromatography analysis with two serial detectors (conductometer and spectrophotometer). The problem of interferences of different ions is discussed.

Soluble And Non Water Soluble Sulphates InDamage Layers On Hydraulic Mortars

The present work attempts to fill the gap in knowledge on the behaviour and durability towards atmospheric multipollutants of hydraulic mortars used as a construction material in buildings and monuments. Different types of ancient and recent hydraulic mortars were collected from the Arsenal in Venice. A summary of the characterization of the samples is presented, along with the identification of the formation products found on the surfaces due to the reaction between the mortars and atmospheric multipollutants. A series of analyses was performed by means of optical microscopy (OM), X-ray diffractometry (XRD), scanning electron microscopy (SEM-EDX), thermal analysis (DTA-TGA) and ion chromatography (IC). The results prove that sulphation processes occur on hydraulic mortars, leading to the formation of a gypsum layer on the external surface of the samples. In addition, non water soluble sulphates were quantified by calculating the difference between the water soluble sulphate measured by IC and the total sulphates measured, using a methodology specifically set up for this purpose. The resulting data reveal that the sulphation of hydraulic mortars is not limited to gypsum formation alone, but that secondary damage processes also occur.

Characterisation Of Ancient Hydraulic Mortars On Roman Monuments

Mortar samples were collected on ancient masonry of the Roman period in archaeological sites of the Latial and Campanian regions (Italy). In order to verify the presence of pozzolan, samples were taken particularly from hydraulic structures, such as aqueducts, water reservoirs and baths. The characterisation of the ancient mortars was performed by optical microscopy (OM), scanning electron microscopy (SEM-EDAX), X-ray diffraction (XRD) and ion chromatography (IC). Observations in thin sections and XRD data permit the identification of typical tracers of the pozzolan, such as glassy, vacuolar grains, leucite crystals, alongwith nefeline, analcime, pyroxenes (augite and diopside). IC data show the presence of sulphate, nitrate, chloride and organic anions in different concentrations in the samples collected from urban sites compared with suburban, rural and marine sites. The obtained data permit a complete characterisation of the mortars composition and their state of conservation.