1,720,968 research outputs found
Recycling of sludge from ornamental stone processing as resource in civil construction
No full textThe main aim of this research is to find a feasible way to reuse mud cuttings
from ornamental stone, such as trachyte and basalt, normally disposed of in landfills,
using it in the production of full and/or aerated bricks for civil purposes. The
study examined the characteristics of full bricks produced with mud cuttings from
ornamental stone including, resistance to uniaxial compression, water absorption
and apparent density of mud alone or when mixed with two types of clay at
different firing temperatures. As temperature rose, the strength and density of the
samples increased, while absorption decreased. The use of clay improved the
sintering process during firing, giving a less porous and mechanically stronger
material that normally used to produce full bricks for civil constructions. For the
second type of product, aerated bricks, the study investigated porosity, density,
resistance to uniaxial compression and the thermal insulation capacity of bricks
made by adding lime and aluminium powder to trachyte mud at different sintering
temperatures, ranging between 980 and 1040 °C. As temperature increased, it was
observed that an increase in the resistance and density of the samples was accompanied
by a reduction in the heat-insulating capacity. When compared with commercial
aerated bricks, it was found that aerated bricks obtained from trachyte
sludge cuttings and fired at temperatures below 1030 °C, have a greater thermal
insulation capacity but a lower mechanical resistance, restricting their use to
non-load-bearing masonry applications
Carta delle rocce ornamentali della Sardegna
No full textThe poster shows a collection of decorative stones extracted over the last fifty years in Sardinia.
The term decorative stone is used generically to refer to all natural stones that can be used as decorative material, mainly for cladding and covering and secondarily in a structural role. The term ornamental stone is also used. The international industry term is dimension stones.
Reflecting multiple geological events, the lithological Sardinian landscape has offered and still offers a remarkably wide range of possibilities for researching and gathering decorative stones, according to varying requirements, the main being chromaticism and workability, not forgetting other important characteristics such as hardness and durability.
The survey in the Regional Plan of Mining Activities (Piano Regionale delle Attività Estrattive - P.R.A.E.) for the Autonomous Region of Sardinia (Regional Law 30/89) identified eight “Dimension stone producing areas”, each of which features quarries for petrographically homogeneous rock types: granite (4), limestone (1), volcanic rocks (2, basalt and ignimbrites), metamorphic rocks (1
The reuse of abandoned Acquaresi mine voids for storage of the Masua flotation tailings
No full textOften in abandoned mine sites are present both underground voids produced by mining and the tailings of treatment plant. An interesting solution for the rehabilitation of the sites would be to place the tailings of the process in the underground mining voids, thus obtaining the reclamation of surface areas and the stabilization of abandoned voids to prevent the dangerous phenomena of subsidence. However, these operations require inert waste, which must not be source of pollution, and the choice of a water/solid optimum to ensure good conditions of pumpabilit
Fanghi di segagione della trachite per la produzione di laterizi
No full textL’articolo propone l’utilizzo di un modello matematico per la previsione delle caratteristiche in cottura e post-cottura dei materiali ceramici basato sulla regressione lineare multipla fra vari parametri misurati sperimentalmente. L’obiettivo del lavoro è quello di dimostrare come attraverso l’utilizzo del modello proposto sia possibile studiare, stabilite le proprietà tecnologiche che si intende raggiungere, la composizione ottimale della miscela. Lo studio prende lo spunto dalla realtà sarda, regione ricca di materie prime per l’industria della ceramica ma priva di un prodotto naturale in grado di assicurare tal quale le proprietà tecnologiche richieste.
Lo studio è stato sviluppato in due fasi: la prima di caratterizzazione delle argille sarde e di confronto fra queste e quelle comunemente usate in ambito nazionale nelle preparazioni ceramiche.
La seconda parte riguarda l’elaborazione del modello statistico. Le proprietà che si dimostrano indispensabili ai fini dell’applicazione del modello sono risultate: la granulometria, la composizione chimica, i limiti di Atterberg, la perdita al fuoco (LoI), l’assorbimento d’acqua (WA), il ritiro in cottura (LFS) e la dilatabilità (DIL) in cottura. Nell’articolo si illustrano la procedura statistica seguita per la definizione del modello matematico ed i risultati delle verifiche eseguite su 15 tipologie di materiali, alcuni naturali altri miscele tra questi
Kinetics of heavy metals leaching from contaminated soils in metallurgical plants
No full textKinetics of Heavy Metals Leaching from Contaminated Soils in Metallurgical Plants
Paolo Desogus , Pier Paolo Manca , Giampaolo Orrù
Abstract
The work aims to highlight the main parameters that affect the efficiency of the process of leaching of heavy metals from a natural soil taken from inside a metallurgical plant. The studies were conducted by laboratory tests and the results will allow identifying the fundamental choices for the applications of the technique of in situ soil flushing.
The tested soil samples were mainly made by fine silica sand, with medium density. Their pollution was caused by waste of the metallurgy of lead and zinc released into the soil to transport by rainwater. Their depth ranges from 1 to 2 meters from ground the level from which they are separated by artificial strata composed of soil mixed with metallurgical solid waste. The layer of soil tested hosts an aquifer with a slow permeability, variable depth generally higher than 10m contaminated by heavy metals.
The leaching experiments were conducted through the batch and column tests. Acid solutions (acetic. nitric. hydrochloric and sulfuric) were used as extracting agents. During the leaching tests, concentrations of analytics Zn, Pb, Cd, Cu, Mn and Al were verified.
The results highlighted two aspects: (a) the conditions for which they get the best efficiency of leaching and (b) the laws of statistical correlation that describe the kinetics of reaction. The calculations performed have shown that the most efficient leaching agent was the CH3COOH and mainly the flow velocity of the leaching solution conditions the reaction kinetics in the column
Heavy metal leaching contaminated soils from a metallurgical plant
No full textLaboratory tests were carried out to determine the primary parameters affecting the efficiency of the process of leaching heavy metals from natural soil collected inside a metallurgical plant in Italy.
The soil samples tested consisted primarily of medium density, fine silica sand that had been contaminated with lead and zinc metallurgical wastes by percolating rainwater. Samples were obtained 1 to 2 m below ground level in an area where the surface consists of artificial strata composed of soil mixed with metallurgical solid waste. The soil layer tested hosts a low-permeability aquifer (at depths generally greater than 10 m below ground level) that is also contaminated by heavy metals. Batch leaching experiments were conducted using acid solutions (acetic, nitric, hydrochloric and sulphuric) as extracting agents. During leaching tests, concentrations of Zn, Pb, Cd, Cu, Mn and Al were monitored. Results indicate that the best leaching solution varies for all analytes and soil samples examined. Statistical analysis was used to identify correlations between efficiency and leaching rate
Stabilization–solidification treatment of mine tailings using Portland cement, potassium dihydrogen phosphate and ferric chloride hexahydrate
No full textThis paper reports the investigation aimed at verifying the influence of potassium dihydrogen phosphate and ferric chloride hexahydrate on stabilization/solidification (S/S) processes applied to tailing waste from a Pb and Zn mineral processing plant. The use of cement alone (in a percentage equal to 5%) does not permit the obtaining of a final product complying with current Italian legislation. The possibility of using potassium dihydrogen phosphate, singly or combined with ferric chloride hexahydrate, has been investigated under different pH conditions, simulating the aging phase in waste-cement mixtures. The combined effect of the additives mentioned (1% KH2PO4 and 1% FeCl3), together with small quantities of cement, permits production of inert material, through the physical encapsulation and formation of stable compounds
- …
