Paola Ligas

Kaolinitic materials from Romana (north-west Sardinia, Italy) and their ceramic properties

Abstract The Romana kaolins represent the alteration products of rhyolite-rhyodacite Oligocene volcanics from SW Sardinia, Italy. In order to assess their potentiality in the ceramic industry, samples from four prospects were analyzed from a chemical (XRF), mineralogical (XRD) and technological viewpoint. These raw materials basically consist of kaolinite + cristobalite + quartz-tridymite-feldspars, with hematite and alunite restricted to certain zones or horizons. The kaolinite-to-silica minerals ratio varies to a large extent, affecting the technological properties of Romana kaolins, which are characterized by low values of shrinkage and bending strength after pressing, drying and firing. The behaviour during firing is quite refractory, with high water absorption even at high temperatures (1200–1300°C). Overall, these kaolins could be used to manufacture vitrified tiles or sanitaryware; in both cases, the Sardinian raw materials should be added to the body in partial replacement of the quartz-rich kaolinitic clays currently used in the Italian ceramic industry.

Chemical, mineralogical and ceramic properties of kaolinitic materials from the Tresnuraghes mining district (Western Sardinia, Italy)

Abstract Kaolinitic materials crop out in the Tresnuraghes mining district (Western Sardinia, Italy). Three main kaolinitic deposits, located in the Patalza, Salamura and Su Fongarazzu areas, respectively, were investigated in order to assess their potential in the ceramic industry. The parent rock-types of this raw material are the Oligocene–Miocene rhyolitic–rhyodacitic ignimbrites. Chemical and mineralogical analyses were performed on representative samples of each deposit, by XRD and XRF methodologies. The chemical analyses generally show high silica and low alumina contents in all samples, typical of weakly kaolinized materials. The main mineralogical association consists of kaolinite and cristobalite with quartz and smectite as the minor components. Alunite may be present as a main mineral in the Salamura and Su Fongarazzu deposits, making these clay materials unsuitable for ceramic applications. The Patalza deposit exhibits low iron and sulphur contents, but low plasticity and excessive refractoriness. The Patalza materials can be used as unconventional raw materials to replace both kaolin and silica in white-firing bodies. Results show that the introduction of the Patalza “kaolins” was well tolerated in bodies for tableware, wall and floor tiles, without significant changes in porosity, bulk density, pore size distribution and coefficient of thermal expansion. The main drawback of using the Patalza material is the slight increase of firing shrinkage, while the main advantage is a systematic increase in mechanical resistance.

An experimental application of a 3D terrestrial laser scanner and acoustic techniques in assessing the quality of the stones used in monumental structures

This paper briefly describes the preliminary results of an experiment that aimed to test a new nondestructive methodology based on the integrated application of Three-Dimensional (3D) terrestrial laser scanning and acoustic techniques in the ultrasonic range (54 kHz) in evaluating the quality of stone materials. Our target is to evaluate the state of conservation of stone materials by correlating ultrasonic longitudinal pulse velocity and frequency spectra with the reflectivity or reflectance of the reflected 3D Laser Scanner (LS) beam pulse transmitted to a part of an investigated surface.

Dynamic elastic characterization of carbonate rocks used as building materials in the historical city centre of Cagliari (Italy)

This paper focuses on the dynamic characterization approach to evaluate the conservation state of carbonate building stones of monumental structures. In particular, we report the use of elastic waves at an ultrasonic frequency of 54 kHz to define quantitatively some dynamic properties of carbonate rock types used as building materials. Measurements of compressional and shear wave velocities have been carried out and the relationship between some physical properties of the investigated rocks and these geophysical measurements have been evaluated. The ultrasonic data were also supplemented by a petrographical study of these rocks to correlate their petrophysical features with the elastic ones. Based on the results of the laboratory measurements, in situ applications on a significant monumental structure have been also carried out to check zones of weakness and to assess the state of deterioration of the investigated stones. A comparison of laboratory and in situ results confirms that dynamic characterization is a useful approach.

An innovative methodology for the non-destructive diagnosis of architectural elements of ancient historical buildings

In the following we present a new non-invasive methodology aimed at the diagnosis of stone building materials used in historical buildings and architectural elements. This methodology consists of the integrated sequential application of in situ proximal sensing methodologies such as the 3D Terrestrial Laser Scanner for the 3D modelling of investigated objects together with laboratory and in situ non-invasive multi-techniques acoustic data, preceded by an accurate petrographical study of the investigated stone materials by optical and scanning electron microscopy. The increasing necessity to integrate different types of techniques in the safeguard of the Cultural Heritage is the result of the following two interdependent factors: 1) The diagnostic process on the building stone materials of monuments is increasingly focused on difficult targets in critical situations. In these cases, the diagnosis using only one type of non-invasive technique may not be sufficient to investigate the conservation status of the stone materials of the superficial and inner parts of the studied structures 2) Recent technological and scientific developments in the field of non-invasive diagnostic techniques for different types of materials favors and supports the acquisition, processing and interpretation of huge multidisciplinary datasets.

Characterization of Co2 Storage Reservoir - A Case Study From South Western Sardinia, Italy

This study presents the results of the characterization of carbonate rocks (“Miliolitico” Formation Auct.) located at the base of the Eocene stratigraphic sequence in South-Western Sardinia (Sulcis Coal Basin) that could be used as a natural reservoir for CO2 storage in a very important mining district. The Sulcis Coal Basin is characterised by a significant presence both of minable coal, and of deep carbon layers. The carbonate reservoir characterization carried out mainly by petrophysical and seismic investigations was targeted to provide experimental data useful both for the subsequent geological and numerical modelling.

3D geophysical imaging for site-specific characterization plan of an old landfill

As it is well-known, the characterization plan of an old landfill site is the first stage of the project for the treatment and reclamation of contaminated lands. It is a preliminary in-situ study, with collection of data related to pollution phenomena, and is aimed at defining the physical properties and the geometry of fill materials as well as the possible migration paths of pollutants to the surrounding environmental targets (subsoil and groundwater). To properly evaluate the extent and potential for subsoil contamination, waste volume and possible leachate emissions from the landfill have to be assessed. In such perspective, the integrated use of geophysical methods is an important tool as it allows a detailed 3D representation of the whole system, i.e. waste body and hosting environment (surrounding rocks). This paper presents a very accurate physical and structural characterization of an old landfill and encasing rocks obtained by an integrated analysis of data coming from a multi-methodological geophysical exploration. Moreover, drillings were carried out for waste sampling and characterization of the landfill body, as well as for calibration of the geophysical modeling.