41 research outputs found
Natural stone sludge as secondary raw materials: towards a new sustainable recovery process
L'abstract è presente nell'allegato / the abstract is in the attachmen
Stone roofing in the Aosta Valley, Italy: Technical properties and durability of traditional Lithotypes
The Aosta Valley Region has promulgated in 1990 a law to partially finance stone roofs to the owners of houses in the historic centers of the valley, provided that the stone material chosen was suitable for this use. This suitability was certified by physical, mechanical and durability tests. More than twenty years ago, roofing slabs were extracted in north-western Alps mainly from schistose rocks. In recent time instead roofing slabs, according to global market, have an international origin. All the traditional stones tested showed excellent technical features according to the local legislation on roof slates. One of these traditional stones is a phyllite whose trade name is “Porfiroide” having the best physical and mechanical properties compared to the other kinds of traditional stones, but with a high standard deviation in the results of flexural strength performed after the freeze and thaw cycles. In the roofing installed 40 years ago, despite their best technical features, the “Porfiroide” roof slabs show a poor state of conservation with widespread detachments, fractures, growth of mosses and lichens, variations in colours. Otherwise, stones with a lower value of flexural strength and higher water absorption instead show good behaviour in the roofing in situ and also in terms of colour change. Evidently the only characterisation of the stone materials is not sufficient but it must be associated to a on-site verification, comparing each slab to be installed with a reference sample, part of the sample submitted to the tests, and to a control on site of the resistance of the stones to degradation
Ornamental Stone Cutting Processing and Sludge Production Evaluation with the Goal of Ending Waste
In the quarry sector, the reduction of landfill material may be obtained not only by finding
a suitable recovery of the material as a by-product, but also by identifying the best available cutting
technique to be used on the basis of the physical, chemical, and mechanical characteristics of the
stones. The choice of the best cutting technique could lead to high efficiency and performance, high
quality of the cut surfaces, and a very low environmental impact by reducing energy consumption,
decreasing the concentration of heavy metals in the sludge, and producing less waste. In this context,
an analysis of the procedures for cutting different types of ornamental stones into slabs together with
the evaluation of sludge production for the different cutting methods has been carried out. Two types
of analysis were carried out in parallel: evaluation of the stones workability and calculation of the
amount of sludge produced in the three different cutting technologies and from the cutting of blocks.
A comparison was carried out on the quality of the sludge produced, on type and quantity of metals
present, taking into account the different cutting technologies. The performed tests were: chemical
analysis, magnetic separation test, and SEM analysis of the metal fraction. The study could provide
stone producers with a technological, scientific instrument to identify the best cutting techniques
for the processing of their stones, in order to obtain a high-efficiency process, optimize the recovery
process, increase the economic advantages, and evaluate the possible reuse of the sludge through a
proactive waste management strategy
Ornamental stone cutting processing and sludge production evaluation with the goal of ending waste.
The End-of-waste concept was introduced by the ‘Thematic Strategy on the prevention and recycling of waste’ adopted by the European Commission, in which it proposed to specify the conditions for the cessation of waste status as part of the revision of the Waste Framework Directive (Directive 2008/98/EC). The Directive states that a waste shall lose its status if it is submitted to a recovery operation (including recycling) and comply with specific eligibility criteria. The strategic goal of the End-of-waste is to promote recycling, helping to ensure a high level of environmental protection through the reduction of the consumption of critical raw materials and the quantities of waste destined for disposal.
In the mining sector, the reduction of landfill material may be obtained not only by finding a suitable recovery of the material as a by-product, but also identifying the best available cutting technique to be used on the basis of the physical, chemical and mechanical characteristics of the stones. The choice of the best cutting technique could lead to high efficiency and performance, high quality of the cut surfaces and a very low environmental impact by reducing energy consumption, decreasing the concentration of heavy metals in the sludge and producing less waste.
In this context, an analysis of the procedures for cutting different types of ornamental stones into slabs together with the evaluation of sludge production for the different cutting methods has been carried out.
Three types of analysis were conducted in parallel. The first concerns the characterization of the stones and the choice of the type of cutting machine. The analyses carried out were: petrographic analysis, compression strength, flexural strength, apparent density and water absorption. Also ultrasonic pulse velocity (UPV) and Knoop analyses were performed in order to establish the workability class of the stones, and their classification in accordance with previous research works (EASE R3).
The second analysis involves calculating the amount of sludge produced in the three different cutting technologies, taking into account the same block characteristics. The third analysis was conducted on the sludge resulting from the processing of blocks cut into slabs. A comparison was carried out on the quality of the sludge produced, or type and quantity of metals present, taking into account the three different technologies. The tests carried out were: chemical analysis, magnetic separation test and SEM analysis of the metal fraction.
The study could provide stone producers with a technological, scientific instrument to identify the best cutting techniques for the processing of their stones, in order to obtain a good efficiency process, optimize the recovery process, increase the economic advantages, and evaluate the possible reuse of the sludge through a proactive waste management strategy
Characterization of sludge resulting from the extraction and processing of natural stones. focus on a Piedmont case
The problem of the management of sludge resulting from the extraction and processing of ornamental stones is currently one of the key issues for the European Union and for Italy.
The European Community, through Directive 2006/21/EC (Management of waste from extractive industries – Mining waste), Directive 2008/98/EC (Waste Framework) and Directive 1999/31/EC (Landfill Waste), has provided guidelines for its member countries on how to handle wastes, in view of a future sustainable development of the sector, especially as far as critical raw material (CRM) is concerned.
In this context, an analysis of the procedure applied to extract and cut two similar Piedmont silicatic stones into slabs and to manage their sludge has been carried out.
The ornamental stones taken into consideration are Diorite of Traversella and Perosa Stone (Dioritic gneiss). The following procedures were conducted to characterise the stones: petrographic analysis, as well as compressive strength, flexural strength, impact resistance and water absorption tests. This characterization is important to help choose the best available technique to extract and process the stones. The methodologies adopted in two different plants, according to their processed stones, are discussed hereafter. In addition, UPV and Knoop analyses were performed in order to establish the workability class of the two stones, and the classification developed in previous research works was applied.
Subsequently, an analysis was conducted on the sludge resulting from the extraction and processing of blocks used for the production of slabs. A chemical analysis, a particle size analysis, a magnetic separation test, to obtain two fractions (metallic and mineral), and an SEM analysis of the two separated fractions were performed on the two sludges.
This characterization was useful to understand whether the produced sludge could be recovered as by-products. The study will help stone producers to identify the best techniques for the extraction and processing of their stones, while obtaining less waste and less pollution
Marble Durability Assessment by Means of Total Optical Porosity and Adjacent Grain Analysis
The presence of pores, cracks and microcracks in marble is one of the main features that
govern the processes of decay of this stone material and, although marble is characterised by a
modest porosity, there is a clear correlation between the presence and movement of fluids, and the
phenomena of alteration. Through the study of porosity, it is possible to better understand the
phenomena of alteration and degradation in order to obtain useful information, not only in the field
of modern building, but also for the protection and recovery of historical and artistic heritage goods.
This study was conducted through the characterisation of parameters directly related with the
degree of alteration of the materials: water absorption at atmospheric pressure (EN 13755), open
porosity (EN 1936), flexural strength (EN 12372) and bowing (EN 16306 par. 8.2). The physical
and mechanical measurements have been compared with the Total Optical Porosity method (TOP)
and the Adjacent Grain Analysis (AGA) index (a suggested method to evaluate the marbles’
tendency to bow, in EN 16306 annex C); two different methodologies both based on image
analysis. The purpose of this study is to demonstrate the effectiveness, for the assessment of marble
durability, of the two techniques of microscopic image analysis, the first correlating to the grain
shape and the second to the open porosity index. This was done by comparing the microscopic
image analysis results with the physical and mechanical properties, both after artificial ageing and
after ten years of natural ageing. The results obtained with the TOP method seem to represent the
tendency to decay better than the AGA index. The comparison of image analysis of the thin
sections, in different portions of the marble specimens, shows the development of degradation due
to atmospheric agents, from the surface to the inside, of naturally aged specimens, confirming
recent studies made on different marbles
CIRCULAR ECONOMY IN THE EXTRACTIVE SECTOR
The mining and the quarry sector shares the need to enhance the by-products as one of the most effective tools to limit waste production. This has the aim of minimizing the environmental cost of raw materials upstream production chains and to support research and technological innovation, providing opportunities for growth, competitiveness and creation of added value for important sectors.
The exploitation of mines, quarries and the related treatment plants produces large quantities of "tailings". The by-product can be reused for different purposes within the construction supply chain (construction of road embankments, concrete, pre-mixed products, fillers etc.) thanks to their shape, size, physical and petrographic characteristics. For this reason it is essential to enhance the use of by-products of the extractive industry according to the last European regulation and implementing the National ones.
In particular, the main crucial points in extractive industry to be faced and improved applying the Circular Economy approach are:
- mining/quarry tailings.
- sawing sludge from ornamental stone industry.
- waste water from aggregate processing.
The “circular approach” in the extractive industry is possible considering by-products in zero-waste supply chains as valuable secondary raw materials since the very beginning of every operation planning. A change in this vision is needed to sustain, also by means of proper indicator, an even more efficient circular economy
Vinyl-Asbestos Floor Risk Exposure in Three Different Simulations
Vinyl floors are widely used in public areas for their low cost and easy cleaning. From 1960
to 1980, asbestos was often added to improve vinyl floor performances. The Italian Ministerial Decree
(M.D.) 06/09/94 indicates asbestos vinyl tiles as non-friable materials and, therefore, few dangerous
to human health. This work aims to check through three different experimental tests if asbestos floor
tiles, after decades of use, maintain their characteristics of compactness and non-friability. The effect
of a small stone fragment stuck in the sole of rubber shoes was reproduced by striking the vinyl floor
with a crampon. A vinyl tile was broken into smaller pieces with the aid of pliers to simulate what
normally happens when workers replace the floors or sample it to verify the presence of asbestos.
The third test reproduced the abrasion of the tile surface due to the dragging of furniture or heavy
materials or sand grains that remain attached to the soles of shoes. The tests were carried out in
safe conditions, working under an extractor hood with a glove box. Airborne sampling in the hood
obtained the concentration of asbestos fibers produced in each test. The simulation tests performed
confirms the possible release of fibers if the vinyl tiles are cut, abraded or perforated, as indicated by
the Italian M.D
A new scientific approach to determine the stone workability
The prediction of stone ‐ diamond wire interaction is important for the extractive sector,
both to improve the productivity and efficiency of quarry work and to avoid dangerous
and expensive endeavours of cutting when an unknown stone has to be introduced in the
plant. Combining two simple test as the measurement of ultrasonic pulse velocity of the
stone and the Knoop micro hardness, a scientific classification of workability have been
found. In particular, in this work the application of this scientific classification
methodology to the stone plant has been studied, performing UPV measurements on
stone block before their cutting The correlation of ultrasonic measurements by indirect
method with the index HK25 allowed to order the stones in classes of workability that
correspond to what the owners of the plant used to give to such stones. Moreover the
correspondence with the in situ cutting parameters has confirmed the reliability of this
scientific methodology.
THE RE-USE OF SILICATIC STONE SAWING SLUDGE IN THE BUILDING SECTOR
The problem related to the reuse of sludge deriving from the cutting of ornamental stone is a relevant topic for many countries. Even if many studies are carried out on the recovery of sludge resulting from carbonatic cutting rocks the reuse of silicatic sawing sludge remains a challenge due to higher amount of metals than carbonatic stone sludge.
Two kind of silicatic sawing sludge reuse in the building sector have been analysed on the basis of their physical-chemical characteristics. The recoveries were planned based on the sludge metals content. The first use, as CLSM (Control Low Strength Material), provided the use of sludge as filler with the goal to increase the capacity to dissipate thermal energy, due to the passage in the sub-road network of sub-services. The second reuse is for thermo-eco-mortar for plaster, as filler which allow a thermal insulation and at the same time a good mechanical resistance. The properties of mortar for plaster and of CLSM have been evaluated by means technological test on specimens made with different composition (mix design).
The choice of the type of recovery was carried out on the basis of chemical and magnetic separations carried out during the sludge characterization steps. Moreover, chemical analysis and leaching tests were performed on the finished product to verify the amount of metals present in the product obtained.
Economic evaluation has been carried out on the cost sludge disposal in comparison with its recovery as raw material for building construction, demonstrating an interesting approach not only on the environmental but also on the economic point of view