Hydraulic properties of ignimbrites: matrix and fracture permeabilities in two pyroclastic flow deposits from Cimino‑Vico volcanoes (Italy)

Hydrological properties of ignimbrites are known in detail only for some areas, although these rocks cover large areas with considerable thicknesses in many volcanic regions of the world. This study investigates hydrological properties of two ignimbrites of Latium (Central Italy), different in age, composition, and origin. The dual porosity of the ignimbrites was examined through laboratory tests, pumping tests, and outcrop surveys. The degree of welding, composition, and stratigraphy of the two ignimbrites are the main factors determining their hydrological properties. The two ignimbrites share a low matrix permeability, showing a different fracturing degree. The more welded ignimbrite is characterized by lower porosity of the matrix and higher fracturing degree, while the less welded ignimbrite is characterized by higher porosity of the matrix and lower fracturing degree. Hydraulic conductivity and storage capacity of the highly welded ignimbrite mainly depend on the denser network of discontinuities. The hydraulic conductivity of the younger ignimbrite, less welded, mainly depend on the sparser network of discontinuities and on the layer of unconsolidated coarse pyroclastic deposits at its base, while the storage capacity depends on the more porous matrix. Should the pyroclastic rocks be used as aquifer for water supplies, or, in other cases, as substratum of waste disposal sites, the dual porosity of the ignimbrites must necessarily include different scales of analysis in order to evaluate the role of matrix and fractures on the permeability of rock mass. In any case, the results of laboratory and on-site tests are to be interpreted taking into account the stratigraphy of the ignimbrite

Use of zeolite-rich rocks and waste materials for the production of structural lightweight concretes

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/cm3 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/cm3) potentially useful for the manufacture of thermo insulating lightweight concretes

Lava stones from Neapolitan volcanic districts in the architecture of Campania region, Italy

Abstract Results of a research carried out on the lavas from Campi Flegrei and Somma-Vesuvius volcanic districts are reported here. The lavas have been widely employed, since Roman age, in several important monumental buildings of the Campania region, mainly in the town of Naples and in its province. They are classified as trachytes (Campi Flegrei products), tephri-phonolites and phono-tephrites (Somma-Vesuvius complex) from a petrographical point of view. Sampling was carried out from well-known exploitation districts. A substantial chemical difference between the products of the two sectors was confirmed, while petrophysical characterization evidenced similarity among the two different materials, although some differences were recorded even in samples coming from the same exploitation site

I tufi vulcanici nel costruito storico: vulnerabilità e possibili trattamenti per la conservazione e il restauro

Con questa ricerca si intende approfondire le conoscenze su alcuni litotipi che afferiscono a due importanti formazioni vulcanoclastiche: l???Ignimbrite Campana sia in facies gialla che grigia e il Tufo Giallo Napoletano. Questi materiali, largamente utilizzati nell???architettura storica della regione Campania, rappresentano un patrimonio storico-culturale, la cui tutela e conservazione deriva direttamente da un???approfondita conoscenza non solo del litotipo stesso ma anche del contesto in cui questo è utilizzato come materiale da costruzione. A tal fine sono stati censiti gli impieghi principali delle vulcanoclastiti sia come materiale da costruzione che come lapideo ornamentale e la loro distribuzione nelle aree di maggiore interesse storico. Sono state poi valutate le principali caratteristiche di questi geomateriali al fine di migliorare la conoscenza dei litotipi dal punto di vista mineralogico, chimico e soprattutto dei parametri petrofisici, poco conosciuti a tutt???oggi. Sono state osservate le modificazioni che i tufi subiscono nel tempo in conseguenza della interazione con gli agenti del degrado, sostanzialmente l???umidità (o acqua di infiltrazione) che costituisce il veicolo più importante per il degrado della pietra e le variazioni di temperatura. Al contempo sono stati approfonditi anche i processi chimici e fisici connessi ai fenomeni di alterazione, valutando le modificazioni indotte nella pietra in seguito ai trattamenti di invecchiamento artificiale. È stato infine verificato l???impiego sperimentale di consolidanti e protettivi, con l???obiettivo di migliorare le caratteristiche di compattezza e resistenza della roccia, modificandone la struttura interna e limitando per quanto possibile le infiltrazioni d'acqua meterorica

Ba and Co removal from water by elution through fixed beds of phillipsite- and/or chabazite-rich tuffs

The possibility of using phillipsite- and chabazite-rich tuffs as cation exchangers in the process of barium and cobalt removal from wastewaters was evaluated. Accordingly, fixed beds of phillipsite-rich Neapolitan yellow tuff grains and of chabazite-fich Orvieto-Bagnoregio ignimbrite grains were prepared. After exchanging them in Na+ form, the relevant breakthrough curves were determined at room temperature, using 100 mg/L solutions for each cation. Some characteristic dynamic parameters were calculated from these curves, such as length of mass transfer zone, ion, exchange capacity in dynamic conditions, dynamic selectivity and efficiency of the process, obtaining information on the conditions under which the process should be carried out. The data collected evidenced the good selectivity of both Na-exchanged zeolites for Ba and the poor selectivity for Co, confirming the results previously obtained in equilibrium conditions. The difficulty of eluting barium from the tuff beds during regeneration suggested a profitable employment of Italian phillipsite- and/or chabazite-rich tuffs in discontinuous processes, which are especially useful in the treatment of nuclear power plant wastes, in which the zeolitic sludge generated from Ba removal is usually stabilized-solidified in a cement matrix

Evaluation of an intermediate-silica sedimentary chabazite as exchanger for radioactive cations

Intermediate-silica sedimentary chabazite contained in two chabazite-rich tuffaceous rocks has been evaluated as potential cation exchanger for radioactive cation removal from nuclear waste streams. Exchange isotherms have been obtained for the cationic couples Na/Ba, Na/Co, Na/Cs and Na/Sr and the relevant thermodynamic parameters calculated with the help of a computer program. Sedimentary chabazite turns out very selective for Cs+, fairly selective for Ba2+ and Sr2+, especially at low equivalent fraction of these cations in solution, and unselective for Co2+. An explanation of the observed selectivities is attempted on the basis of the structural features of chabazite

Comparison of Latest and Innovative Silica-Based Consolidants for Volcanic Stones

This research explores the new perspectives in conservation and protection of two macroporous tuff stones, widely employed in the architectural heritage of Campania region, characterized by highly heterogeneous rock fabric and texture and a variable mineralogical composition that represent crucial factors responsible for their weak durability. The consolidation treatments were performed with a recently and widely used suspension of nano-silica crystals in water and with a lithium silicate solution that has received up to now scarce attention as a consolidant agent. Physical investigations (open porosity, Hg porosimetry, water absorption), morphological observations (SEM analyses) and visual appearance test (colorimetric measurements), along with assessments of performance indicators such as ultrasonic pulse velocity, surface cohesion test (peeling test) and durability test (salt crystallization), were carried out to investigate the consolidation effectiveness. Overall, lithium silicate consolidant showed a better behavior in terms of superficial cohesion, a most successful strengthening action and a considerable enhancement of salt resistance