Maurizio de Gennaro

Influence of zeolites on the sintering and technological properties of porcelain stoneware tiles

Low-cost zeolitic rocks are promising substitutes for feldspathic fluxes in ceramic bodies, since their fusibility, modest hardness and high cation exchange capacity (CEC) should improve grinding and sintering. Five large-scale Italian deposits of natural zeolites with different mineralogy were characterised and tested in porcelain stoneware bodies. Their behaviour during processing was appraised and compared with that of zeolite-free bodies. Zeolites increased the slip viscosity during wet grinding, causing a coarser grain size distribution and consequently some drawbacks in both unfired and fired tiles. After overcoming this hindrance by dry grinding of zeolite rocks, the technological behaviour of zeolite-bearing tiles appear to be similar to that of current porcelain stoneware, though with larger firing shrinkage and residual closed porosity.

Use of thermal analysis for the evaluation of zeolite content in mixtures of hydrated phases

Abstract A method, based on water vapour desorption, for the estimation of zeolite content in mixtures of hydrated phases is presented. The accuracy and reliability of the method and the ease of its application are demonstrated through an evaluation of the chabazite and phillipsite contents of Italian tuffs. The method is suitable for more general use provided that the pure phases of the mixture under investigation are available and their thermal features are known.

Building stone and related weathering in the architecture of the ancient city of Naples

Abstract The survey of materials constituting the buildings of the ancient city centre of Naples and of their decay typologies was carried out. Reports were entered in a database which enabled us to draw two thematic maps in a digital format: one of materials and lithotypes, and one showing weathering. On this basis, quantitative evaluations of the lithotypes were carried out. The research pointed out that the use of different lithotypes was mainly as a result of their availability and/or ease of exploitation. Furthermore, the importance of the preservation of the quarrying sites was stressed, both for their historical and cultural interest and, above all, for possible forthcoming provisioning finalized to restorations. The analysis of the results, made on a geo-mineralogical basis, as well as the thematic maps, gives a basic tool which will be very useful to those professionals involved in preservation of cultural heritage.

THERMAL BEHAVIOR OF NATURAL AND CATION-EXCHANGED CLINOPTILOLITE FROM SARDINIA (ITALY)

The thermal behavior of two clinoptilolites from an epiclastic and a pyroclastic deposit of central-northern Sardinia and of their exchanged forms (Li, Na, K, Cs, Mg, Ca, Sr and ammonium) were investigated by differential thermal analysis and thermogravimetry up to 1000°C. Their thermal stability was studied by evaluating the residual crystallinity (expressed as rehydration capacity) after 2 h thermal treatments at 450, 600 and 900°C. The water loss at 1000°C was linearly related to the radius (r) and the charge (z) of the exchangeable cations by the equations r2/z or r3/z, which are proportional to the inverse of the charge density over the surface or to the charge density over the volume of the cations.The cation composition plays a crucial role in determining the thermal behavior of clinoptilolite. The presence of cations such as Cs or K, which have low surface or volume charge densities, was found to increase the thermal resistance. In particular, the crystallinity of Cs- and K-exchanged forms of both clinoptilolites was not affected by thermal treatment at 450°C and was only slightly reduced by thermal treatment at 600°C.Predicting the thermal behavior of natural and cation-exchanged forms of these clinoptilolites can provide useful information for possible applications in catalysis, in the case of high thermal stability, or for thermal transformation into ceramics or lightweight aggregates.

Evaluation of Natural Phillipsite and Chabaziteas Cation Exchangers for Copper and Zinc

ABSTRACT Chabazite and phillipsite, two zeolites widespread in many volcaniclastic deposits in central-southern Italy, were evaluated as cation exchangers for the removal of copper and zinc from aqueous solution. Equilibrium and kinetics of copper and zinc exchange reactions for sodium were investigated in order to verify the selectivity and the uptake rate of both zeolites for these heavy metals. Thermody-namic quantities, such as equilibrium constant, K a, and δG′, as well as rate constant, K, were computed, and they showed that Na-chabazite displays a moderate selectivity and a favorable kinetics for copper, whereas in all the other cases uses in wastewater treatment are not recommended.

Hydrothermal conversion of trachytic glass to zeolite; 3, Monocationic model glasses

Experiments on zeolitization were conducted on four synthetic monocationic glasses (Na, K, Ca, or Mg-rich glass) with Si/Al molar ratios of 2.67, similar in acidity to many volcanic glasses of partially zeolitized Italian tuffs. The products of the hydrothermal treatment at 100, 150, and 200°C of single glasses or glass mixtures with deionized H2O or monosaline solutions (NaCl, KCl, CaCl2) were characterized by X-ray diffraction, thermal, microscopic and chemical analyses. Chemical analyses of mother liquors were also performed. Mineral assemblages, containing chabazite, phillipsite, analcime, and K-feldspar, very similar to those found in altered, volcaniclastic alkali-trachytic or trachytic glass deposits were produced. Potassium was essential to chabazite and phillipsite crystallization, although phillipsite was obtained also in Ca-Na mixed systems. Sodium was necessary for analcime formation. Calcium plays only a secondary role in zeolitization, and magnesium does not favor zeolite crystallization but promotes the formation of smectite. Glass composition determines the mineral assemblages obtained and hence in those commonly found in nature.

Zeolitic Tuffs as Raw Materials for Lightweight Aggregates

The aim of this research is to assess the possible use of Italian zeolitic rocks for the production of lightweight aggregates. In particular, both the expansion at high temperature and the technological features of fired products were investigated. Fifteen zeolite-bearing volcanoclastites from Northern Sardinia and three zeolitized tuffs from Campania and Tuscany (Sorano and Campanian ignimbrites and Neapolitan Yellow Tuff) were taken into account. The firing expansion turned out to be mainly dependent on the chemical composition (especially SiO 2 and fluxing oxides such as Fe 2 O 3 , Na 2 O, K 2 O, MgO and CaO) and the water content (largely related to the zeolite amount) of the raw materials. Other relevant parameters were the temperature of maximum expansion (ranging between 1350 and 1500 °C, without additives) and soaking time (between 2 and 5 min). Some products are highly impervious to water (water absorption below 1%) and exhibit a considerable firing expansion (> 100% in volume), a low bulk density (0.5–0.7 g•cm −3 ) and fair technical properties (loose weight and strength of particles). These encouraging results make some of the investigated tuffs interesting raw materials for the production of lightweight aggregates.

Geological features, technological characterization and weathering phenomena of the Miocene Bryozoan and Lithothamnion limestones (central-southern Italy)

Bryozoan and Lithothamnion limestones (BLL) from centralsouthern Italy, commercially known as Perlato Royal Coreno, were used for a long time in the monumental architecture of the Campania and Lazio regions. In this paper, new mineralogical-petrographical and engineering geological data about BLL are reported and the relations between the lithofacial and technical features of this stone are investigated. A field survey of the main limestone outcrops allowed a lithostratigraphic reconstruction of this formation to be drawn and the eight main lithotypes presently used as dimension stones to be recognized. Mineralogical and petrographical characterization was performed by means of X-ray powder diffraction and optical microscopy observation of thin sections (under transmitted, UV-reflected light and cold cathodoluminescence). Petrophysical characterization enabled to compare some engineering-geological properties and to evaluate the influences of rock fabric, chemical composition, fractures and stylolithes on the technical features of the stone. Ageing tests were also performed. Finally the main weathering phenomena affecting the stone were recognised through a detailed study on the facades of the bell tower of the Santa Chiara monastery in Naples

Palaeomagnetic controls on the emplacement of the Neapolitan Yellow Tuff (Campi Flegrei, Southern Italy)

Abstract Two outcrops of Neapolitan Yellow Tuff at Torregaveta and Posillipo have been investigated palaeomagnetically. Analyses of low blocking temperature components, in association with mineralogical, volcanological and magnetic anisotropy data, suggest the following sequence of events: (i) deposition of pyroclastics at temperatures not lower than 275°C, at least at Torregaveta; (ii) cooling associated with zeolitization and modification of the original positions of the clasts; (iii) further dislocation of the clasts after cooling; and (iv) lithification. Such a model reconciles otherwise conflicting volcanological and palaeomagnetic data.

Preliminary contribution on durability of some macroporous monumental stones used in historical towns of Campania Region, Southern Italy

Publisher Summary In Campania region (Southern Italy), the large availability of volcanic products determined the utilization of these products for structural purposes. Neapolitan Yellow Tuff (NYT), Campanian Ignimbrite (CI), and Piperno (PI) were the most widely used volcanic products in historical architecture of Campania region.. This chapter describes the mineralogical and petrographical features of these materials and the research conducted to study the decay phenomena by means of laboratory simulations, which reproduce the aging processes of the stone. Mineralogical characterization was carried out by scanning electron microscopy (SEM) observations and by X-ray powder diffraction analysis (XRPD). Open porosity was calculated by He-pycnometer. Water absorption was measured by immersion test. Ageing tests, wet-dry and salt crystallization tests, were performed to study the decay phenomena. From the mineralogical analysis, a substantial difference was found out between the NYT on one side, and CI and PI on the other. The matrix of the former is mainly constituted by zeolites, amorphous phases, and volcanic glass; and the latter (CI and PI) have a matrix constituted by feldspars and minor amount of glass. The chapter provides table to illustrate variation of the physico-mechanical properties (porosity, water absorption, and uniaxial compressive strength) after aging tests. The overall results obtained show poorer durability of Neapolitan Yellow Tuff, when compared to other stones.