Recovery and valuation of ultrafine marble dust contained in waste slurries deriving from carbonatic natural stones processing plants

The research, conducted in Italy and in Spain, aims at recovery and enhancement of marble powder, deriving from marble processing plants, in the building sector. The building industry is very capable of incorporating and reusing different types of waste materials deriving from different industries. The goal of the investigation is to identify potential uses for the sawing sludge as an alternative to its disposal in dumps, a practise no compatible with the concept of sustainable development. By utilizing the stone processing waste retrieved through recovery-recycling operations this material is no longer considered as waste but as primary or secondary raw materials for use in other production processes, thereby pursuing the dual objective of minimizing waste generation and disposal and producing added value. The investigation focused on the marble district area in Orosei (North-East Sardinia). Firstly, chemical physical and mineralogical determinations were carried out in order to characterize the material; secondly, test specimens were prepared to be submitted at the experimental phase, including mechanical studies. The data emerging from the chemical and mechanical analysis demonstrate the feasibility of these uses (concrete production; brick making; plaster industry; autoclaved aerated concrete manufacturing). Economic evaluation is also considered. ---------------------------------------------------------------------------------------------------------------------------------La ricerca svolta, in Italia ed in Spagna, è stata finalizzata al recupero ed alla valorizzazione, nel campo dei materiali per uso civile, del carbonato di calcio micronizzato proveniente dalle torbide recuperate dagli impianti di segagione e trattamento del marmo. Di fatto, il settore edile è capace di incorporare e di riutilizzare svariati tipi di materiali di scarto prodotti da differenti attività industriali. Nello specifico l’obiettivo della ricerca è stato quello di identificare possibili utilizzi per i fanghi di segagione così da ottenere soluzioni alternative al loro conferimento in discarica, procedimento questo non più compatibile con il concetto di sviluppo sostenibile. Attraverso l’utilizzazione dei rifiuti di lavorazione questi prodotti di scarto non vengono più considerati come rifiuti ma come materie prime o seconde da inserire in ulteriori processi produttivi, conseguendo così il duplice obiettivo di minimizzare le generazioni dei rifiuti da smaltire in discarica e di ottenere un valore aggiunto per le imprese detentrici di tali residui. Lo studio si è concentrato sul polo estrattivo di Orosei (Nord-Est Sardegna). In primo luogo si sono effettuate le determinazioni chimiche, fisiche e mineralogiche per caratterizzare il materiale; in secondo luogo, sono stati preparati provini per sottoporli alle successive fasi della sperimentazione. I risultati ottenuti dimostrano la fattibilità delle applicazioni considerate (produzione di calcestruzzi, mattoni per edilizia, stucchi e calcestruzzo areato autoclavato). Nel presente studio è inoltre proposta una valutazione economica

Acute Delta Hepatitis in Italy spanning three decades (1991–2019): Evidence for the effectiveness of the hepatitis B vaccination campaign

Updated incidence data of acute Delta virus hepatitis (HDV) are lacking worldwide. Our aim was to evaluate incidence of and risk factors for acute HDV in Italy after the introduction of the compulsory vaccination against hepatitis B virus (HBV) in 1991. Data were obtained from the National Surveillance System of acute viral hepatitis (SEIEVA). Independent predictors of HDV were assessed by logistic-regression analysis. The incidence of acute HDV per 1-million population declined from 3.2 cases in 1987 to 0.04 in 2019, parallel to that of acute HBV per 100,000 from 10.0 to 0.39 cases during the same period. The median age of cases increased from 27 years in the decade 1991-1999 to 44 years in the decade 2010-2019 (p < .001). Over the same period, the male/female ratio decreased from 3.8 to 2.1, the proportion of coinfections increased from 55% to 75% (p = .003) and that of HBsAg positive acute hepatitis tested for by IgM anti-HDV linearly decreased from 50.1% to 34.1% (p < .001). People born abroad accounted for 24.6% of cases in 2004-2010 and 32.1% in 2011-2019. In the period 2010-2019, risky sexual behaviour (O.R. 4.2; 95%CI: 1.4-12.8) was the sole independent predictor of acute HDV; conversely intravenous drug use was no longer associated (O.R. 1.25; 95%CI: 0.15-10.22) with this. In conclusion, HBV vaccination was an effective measure to control acute HDV. Intravenous drug use is no longer an efficient mode of HDV spread. Testing for IgM-anti HDV is a grey area requiring alert. Acute HDV in foreigners should be monitored in the years to come

Overview: Health and Safety in the Italian dimension stone quarrying industry

When it comes to human health and safety, the extractive industry represents one of the most hazardous activities. When accidents occur in mines, quarries or processing plants, consequences are usually very serious. A description of Italy’s state of the art is made herein, with a special focus on occupational injuries occurred during the 2012-2019 period of time as well as fatal injuries of the last eight years. The mining and quarrying economic activity had been intensely scrutinised and its outcome was further applied to the 5 economic division as per NACE classification. A further investigation was lead on the quarrying of stone, sand and clay, which is the most affected division with regard to occupational safety. The causes of fatal accidents of the past six years, were analysed and reported in this treatise. Based on the outlined data, the study aims to assess the main safety risks linked with the mining and quarrying industry with a focus on the Dimension Stone sector. It also analyses the diamond wire sawing process in more detail. Suggestions and ideas are offered to mitigate risks

Sustainable reuse of marble sludge in tyre mixtures

The problem of the large amounts of waste products deriving from ornamental stone industrial activities affects not only the environmental impact but also the resources maintenance and the problem of waste management. This paper presents the essential features of an environmentally attractive reuse of what is currently considered a marble waste: marble sludge, recovered from marble sawing and slurry processing. A research is currently carried out in order to join this by-product with possible industrial applications. Simplified rubber formulations, filled with dewatered marble sludge and cross-linked by vulcanization, have been investigated with the objective of making a comparison with tyre compound obtained by using commercial calcium carbonate filler. From this, rigorous analyses have been carried out. The structural effect of calcium carbonate particles on tyre mixtures tensile strength, hardness, rheometric and morphological properties was inspected. The investigation focused on the materials collected by Orosei marble producing area (NE Sardinia - Italy) and it was carried out in cooperation with the Research & Development Laboratory by Marangoni Spa (Italy). The data emerging from the tests demonstrate how environmental burdens in conjunction with stone production could be reduced to much lower levels, by identifying the way to use marble sludge as filler in high added value products

Filler calcium carbonate industrial applications: the way for enhancing and reusing marble slurry.

Since ancient times marble has been the most praised material due to its multi-use possibilities. The investigation conducted by the authors started several years ago with the aim to outline the study of industrial applications for marble dust deriving from marble processing plants as calcium carbonate. The matter of fact is that this stone slurry is composed primarily of calcium carbonate and has a great potential as secondary raw material or byproduct, although it has up to now been considered as waste and treated as such by their producers. Seeing as how calcium carbonate product specifications vary depending on the application, the marble sludge was submitted to a characterization in order to evaluate the compatibility with the specifications required by particular sectors. Firstly, mineralogical, physical and chemical determinations were carried out. Secondly, tests and analyses have been accomplished for the use of micronized calcium carbonate in building industry (brick, plaster and concrete making). More recently, the possibility of using micronized stone powder to produce different commodities for tyre industries has been studied. The data emerging from the analyses ensure that the sludge production can have a potentially high economic value and allow to go along with the concept of sustainable development

Recovery of sawdust resulting from marble processing plants for future uses in high value added products

The disposal of microfine marble sawdust contained in marble slurry waste, currently represents an additional economic burden for dimension stones companies. This is because the sawdust is considered less important in comparison with the crushed calcareous aggregate produced in stone processing plants. In addition, the sludge is mistakenly viewed as waste that has to be disposed of in landfill. State of the art in recovery and utilisation of calcareous sawdust is mainly aimed in uses as substitute for more expensive ingredient in the building sector. Moreover limestone dust, recovered from marble sawing and processing slurry, has not yet found real economically feasible industrial usage. Due to the high market value of micronised CaCO3, we study the use of limestone sawdust as functional filler in industrial products having higher added value, such as paper, rubber, paints, pharmaceuticals. Standard requirements of CaCO3 for this kind of products are very tight, especially those relating to purity level, particle size distribution and brightness. The high Calcium limestone deposit and the factories in Orosei Marble producing area (Sardinia, Italy) allow the production of high quality microfine dust. To evaluate the properties of the sawdust, several analysis were carried out to compare the results with the standard requirements of CaCO3 for paper, rubber and tyre production. The assessment concerns five different factories and it highlights the possible usage of the sawdust produced in Orosei by carrying out simple and inexpensive changes in both stone-working process and wastewater treatment. Finally, a commentary on environmental laws pertaining to the recycle of this kind of waste is also made in this paper

An investigation of colour properties of Orosei limestones (Italy) by using computer program

In this study, a new computer program developed to determine the colour properties of natural stone products is introduced. The program can scan any digitalised picture of natural stone products and produce several statistical results such as mean, variance, minimum and maximum colour values, skewness and kurtosis values of the colour histogram, energy, contrast, entropy and homogeneity values of the data which may be used to classify the typology and/or quality of natural stone products. As a case study, Orosei limestones (Sardegna, Italy) were used. There are several typologies of Orosei limestones such as Nuvolato (Cloudy), Venato chiaro (Light Veined), Venato medio (Medium Veined), Venato scuro (Dark Veined), Perlato chiaro (Light Pearled), Perlato medio (Medium Pearled) and Perlato scuro (Dark Pearled). The remarkable results produced by the program are presented

Circular economy in marble industry: from stone scraps to sustainable water-based paints

Huge amounts of sludge waste are produced every day during the sawing and processing of carbonate ornamental stones. Most of these materials are landfilled and create serious environmental and health hazards. Thus, it is mandatory to find alternative solutions to recycle them. Since calcium carbonate is the most widely used mineral filler for interior and exterior emulsion paints, this investigation focused on the feasibility of trying out innovative methods of circular economy in a waste processing area. Focusing in the Orosei Marbles’ producing area (North-East Sardinia, Italy), the aim of this study was to compare the performance of water-based paints, through the use of marble sludge waste, as mineral fillers, rather than commercial CaCO3. According to standard normative tests were carried out on paint samples, prepared according to an experimental formulation, after a preliminary chemical and physical characterization of the fillers. The results indicate that the marble sludge waste can be successfully used as mineral filler in water-based paints, and that it requires only light pretreatments consisting of deagglomeration and mechanical dispersion in a wet medium, thus confirming its environmental and economic benefits

Reduction of Marble Waste Landfills through the Enhancement of CaCO3

The purpose of this research is to show how to reduce the amount of landfilled marble waste/scraps by collecting and re-purposing the marble microfine sawdust, which is produced after the sawing and processing of carbonate dimension stones. Our ultimate goal is to identify alternative uses, rather than landfilling. The current solution so far preferred - landfill - does not fully meet sustainable development criteria. Our reduction strategy is based on a regulatory framework which identifies waste, by-product and end of waste status clearer. After a careful characterization, the marble sawdust can be reused and marketed for industrial applications, that employ micronized calcium carbonate, as a new material. During the first few years of study, the research focused on the construction industry (i.e. concrete – plaster - brick), by assessing the extensive use of marble sludge. The building industry is able to incorporate and reuse waste materials deriving from different industries, although, in this way, such material would be regarded as of poor quality. The current trend is to add high economic value to this waste. Since product specifications for calcium carbonate vary depending on its application, a comparison with the paper - rubber - and tyre calcium carbonate requirements is described herein and, in addition, the final results of the tests carried out on marble sawdust in tyre mixtures are also reported in detail