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Two zeolite-rich rock samples extracted from Campanian Ignimbrite tuff quarries, southern Italy, usually used as binding and anticaking agents in animal feeding, were characterized and tested in terms of their resistance in stomach, small and large intestine of pig, using a three step in vitro digestibility trial. The mineralogical composition and major and trace-elements analysis were performed after each digestion step using XRPD and ICP-OES techniques. The main zeolite phases identified are phillipsite and chabazite. Results showed that in vitro physical-chemical conditions (pH 2–3 and T 39 °C) the release of Pb and other elements from the zeolite structure is extremely low and due to the limited breakdown of the zeolite framework and glass/amorphous matter hydrolysis, by the gastric liquids. This aspect also suggests that zeolites, after the total permanence in the animal body digestive tract, can further perform their important function of cation exchanger, with also relevant relapses on the growth and health of the animal species, as well as on the environment. Moreover, the contact of zeolite material with liquids of small and large intestine leads to negligible release of undesirable elements, which are far less than those envisaged by the European Regulations.

This paper aims at testing the use of mixtures constituted by natural zeolitized products and SiC-bearing industrial wastes (sludge deriving from polishing of porcelain stoneware tiles, hereafter DPM) for the production of lightweight expanded aggregates as constituents of structural and/or thermo-insulating lightweight concretes. Two commercial products have been used as zeolite natural source: Cab70 (Yellow facies of Campanian Ignimbrite) and IZclino (Turkish clinoptilolite-rich epiclastite). Different amounts of a calcareous material (Pozzano limestones — hereafter CP) from the Sorrento peninsula (Naples — Italy) were also added to a Cab70–DPM mixture. All raw materials were characterized by means of mineralogical (XRPD) and chemical (XRF) analyses. All the products and mixtures were tested from a technological point of view by means of fusibility and firing tests in order to evaluate the expanding properties. It was evidenced that the expansion of the mixture was deeply depending on the occurrence of SiC in the industrial waste. The addition of CP (10 wt.%) to the mixtures accounts for an even increased expansion, though this is accompanied by a worsening of the mechanical features of the material. These results along with literature data allowed to select 3 mixtures (70% Cab70–30% DPM, 70% IZclino–30% DPM, 60% Cab70–30% DPM–10% CP) and each of them was used for the preparation of 5 l of lightweight aggregates afterward employed for the manufacture of lightweight concretes. It was remarked that natural zeolitized materials mixed with DPM (30 wt.%) can provide lightweight aggregates with densities ranging between 0.8 and 1.0 g/cm 3 suitable for the preparation of structural lightweight concretes. The addition to the mixture of CP (10 wt.%) produces less dense aggregates (0.6–0.7 g/cm 3 ) potentially useful for the manufacture of thermo insulating lightweight concretes.

Aim of this research is an evaluation of the zeolitized facies of Campanian Ignimbrite as raw material for the production of lightweight expanded aggregates (LEA). A commercial product (Cab70) was used as reference for this rock. Tests were carried out on “pure” samples or mixed with an industrial waste mud (DPM — Dried Polishing Mud) deriving from a porcelain stoneware tile polishing process. This mud contains SiC, a phase known to act as bloating enhancer. Raw materials were subjected to mineralogical (XRPD–RIR method) and chemical (XRF) analyses. Bloating upon heating was measured (Leitz heating microscope) on Cab70, DPM and on three mixtures having the following Cab70/DPM ratios: 85/15 (Mix1); 70/30 (Mix2); 50/50 (Mix3). LEA production was assessed both in static (muffle kiln) and in dynamic (rotating kiln) conditions by firing pellets, 3–8 mm in size, between 1220–1380 °C. The unit weight of the single particle was determined on fired and unfired products. All materials evidenced a decreasing density with temperature whereas the same parameter decreases with DPM increasing content. Cab70 LEAs never dropped below 0.90 g/cm3, even at the highest temperature, whereas DPM LEAs range between 0.86 g/cm3 (at 1260 °C) and 0.46 g/cm3 (at 1380 °C). A direct but not linear relationship between DPM content and density was evidenced. Among the three mixtures, Mix2 showed the lowest DPM content able to produce the strongest density reduction. To get LEAs with the same density the rotating kiln required temperatures generally 60–80 °C higher than those of the muffle kiln. This difference should be related to the different thermal insulation of the two systems during firing. Two sets of LEAs were massively produced in dynamic conditions from Cab70 (at 1380 °C) and Mix2 (at 1300 °C). These latter showed better technical performances in terms of unit weight of the single particle (0.81 vs. 0.98 g/cm3), bulk unit weight (460 vs. 565 kg/m3), water absorption coefficients (1.4 vs. 5.5% after 24 h) and compressive strength of the particles (2.9 vs. 0.6 MPa). Differences in pore shape, dimension, abundance and spatial distribution were observed by SEM between the two sets. The technical features of these LEAs were comparable to some expanded clays, with similar grain size, commercialised in Italy. These results are worth interesting as they reveal new perspectives of application both for a rock characterized by a low exploitation cost and widely available in central-southern Italy, as well as for an industrial waste produced in high amount but not recycled at all.

This paper reports novel data concerning the volcanic formation of the Piperno, a stone that has been used for a long time in the monumental architecture of Naples and the Campanian region (Southern Italy). A careful field survey of the outcrops or underground sites so far accessible allowed us to draw a lithostratigraphic reconstruction of the formation and enabled the recognition of the three main layers exploited in past centuries and which provided dimension stones for architectural and structural purposes. Petrophysical and mineralogical characterization also enabled us to discriminate the same layers previously identified. Different scoriae/matrix ratio, scoriae dimension and welding degree are the most peculiar features of these horizons. The combination of these three parameters, even though they did not affect the use of Piperno as dimension stone, somehow determined its variable susceptibility to the weathering agents. However, a linear relationship between the exposure time and the decay of the stone itself, at a parity of weathering intensity, was not observed. This assumption was proved by verifying that the specific layers of the volcanic sequence controlled the weathering degree of Piperno from monuments disregarding their age of emplacement.

This paper investigates the thermal transformation of powders of volcanic tuffs that are used as building stones and aims at thermally transforming them into ceramics. The following positive indications concerning this thermal transformation were found: (1) the structural evolution which brings products similar to traditional ceramics, (2) the good ability to give rise to dense and compact final products, and (3) the good mechanical properties and the lovely appearance of the final products. Nevertheless, the high values of linear shrinkages recorded in this work seem to strongly hinder the thermal transformation of this powder-like waste into ceramics. However, mixing this by-product with other powder-like waste exhibiting higher-dimensional stability, such as those deriving from sawing of granites, appears proper.

A detailed mineralogical and petro-physical characterization was carried out on Campanian Ignimbrite (CI) formation, a volcaniclastic rock widespread over the Campania region. This stone represented and still is an important building material since historical times. Given the huge extension of this formation (about 30 000 km 2 ) the attention was mainly focused on the historical exploitation areas that provided building materials for the medieval village of Casertavecchia. Building stones (different facies of CI) used facciavista in some relevant monuments of this village were also characterized to carry out a comparison with the in situ corresponding rock. At the same time a complete survey of all the lithotypes used for the facades of the village as well as their state of conservation and weathering phenomena was also performed. As expected, CI in its different facies resulted the most common building stone, also affected by severe weathering such as lacks, alveolization and biological patinae, decay forms likely related to the high textural heterogeneity of the rock. Mineralogical and petro-physical characterization allowed to distinguish, within the investigated outcrop area, three different facies: dark, light and earthy grey tuff (DGT, LGT and EGT, respectively). Differences in mineralogical data mainly consist in the presence of clay minerals in the EGT facies only. K-feldspar always occurs in very high amounts (80–90%). As far as geomechanical parameters are concerned, the most pronounced differences are recorded in water absorption capacity, ultrasonic velocities and UCS values. These tests evidenced a substantial homogeneity of DGT and LGT facies and an overall worse behavior of EGT. Tests performed on CI samples from both monuments and outcrops gave similar results. This evidence strengthened the former hypothesis of a location of CI historical quarrying sites close to Casertavecchia. The only exception is the tuff used for the Mastio of the castle, whose chemical features are definitely referable to a different volcaniclastic formation. © 2004 Elsevier SAS. All rights reserved.

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.

An attempt to correlate differnt facies of an important volcaniclastic formation of southern Italy, the Campanian Ignimbrite, with their zeolite content and physico-mechanical properties was carried out. The following parameters were measured: total zeolite content, solid unit weight (γ s ), porosity, and uniaxial compressive strength. Samples were formerly grouped on the basis of the displayed colour in four categories each of them characterized by a different zeolite grade. An increase of zeolite content determines a decrease of porosity and a good positive correlation with UCS values. The relationship existing between zeolite grade and UCS becomes less pronounced or even lost, when zeolite content reaches about 50% wt. Here, UCS values scatter in a quite wide range (3–6 MPa). It is hypothesized that the lithification of zeolite-bearing rocks is the result of two combined effects playing a different role during the zeolitization process: the transformation of the amorphous fraction in zeolite and the rock texture. In the first stage of the zeolitization process the role played by the rock texture (clasts/matrix ratio, pumice concentration, fractures, etc.) is totally masked by the overwhelming behaviour of zeolite itself up to that threshold value, above which the influence of these two leading parameters is inverted.

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.

The Campi Flegrei volcanic field, Southern Italy, is composed of a large variety of pyroclastic deposits related to both magmatic and hydromagmatic activity. In spite of similarities of composition, grain size, age and pre-eruptive environment, the various deposits exhibit great differences in terms of degree and type of alteration of the juvenile components. In particular, detailed analyses of pyroclasts collected in the numerous monogenetic volcanic cones show the broad range of alteration, from fresh glass to complete replacement of the glass by the zeolites. The comparative analysis of 17 different deposits has allowed us to conclude that the eruptive and emplacement conditions were the major controls on the zeolitization processes. The relationships between volcanological features of deposits and secondary mineralization are consistent with the glass-fluid phase reaction in a near-closed post-depositional system. Eruptions characterised by separation of water vapour from the pyroclastic particles produce unaltered or poorly altered deposits. In contrast, eruptions characterised by mechanisms that permit the capture and retention of pore water and water vapour produce zeolitized deposits. According to these lines of evidence the zeolitization of pyroclastic products of Campi Flegrei took place immediately after emplacement, during the cooling of wet deposits.