Search Results (31)

The flocculation-based purification of quarry wastewater continues to pose a significant challenge in mineral processing and environmental engineering, primarily due to persistent turbidity issues and inefficient floc settling behaviour. In this study, we systematically investigate the synergistic effects of organic and inorganic flocculants to reduce turbidity and improve floc settling performance. Through a series of optimised experiments using polyaluminium chloride as an inorganic flocculant, polyacrylamide as an organic flocculant, and calcium oxide as a pH regulator agent, the treatment efficiency was evaluated. Under the optimal conditions with 200 g/m³ CaO as the regulator agent and 2.5 g/m³ PAC and 12 g/m³ PAM as flocculants, the residual turbidity was reduced to 97.30 NTU, meeting stringent industrial discharge standards and enabling zero-discharge water reuse. Zeta potential measurements, optical microscopy, and DLVO theory collectively elucidated the interfacial interactions between flocculants and mineral particles, with zeta potential revealing electrostatic effects, microscopy visualising aggregation patterns, and DLVO theory modelling revealing colloidal stability, thereby mechanistically explaining the enhanced aggregation behaviour. Full article

Mining and stone processing activities generate a large amount of various types of waste. Among these, Stone Waste Sludge (SWS) constitutes 22.5 percent of the raw material processed and is disposed of by delivering it to now disused quarries with significant landscape and environmental consequences. This paper describes research aimed at identifying the possible uses of this waste, transforming it from a waste to a resource for the production of building blocks. The production of such building blocks is based on historical preparations of mixtures for artificial stone and is developed through an experimental approach and a simple and economical production methodology. Mixes consisting mainly of SWS and Portland cement (PC) were designed and tested. The aggregates and PC were mixed, wetted, and compacted under high pressure in special molds to form the specimens. The design of the mixtures and related tests aimed to define the process parameters considered such as the amount of water (W), the ratio of PC to SWS, and the compaction pressure. The compressive strength of the manufactured specimens at the age of 28 days was identified as the response variable. The results indicated that all of the mixtures had high mechanical strength values even when using high amounts of SWS relative to the amount of PC and that all of them have excellent characteristics for use as building elements in construction. This implies that such waste has an excellent potential for large-scale reuse in construction and encourages further research and testing, both in terms of the thermo-hygrometric properties of such elements and in terms of LCA analysis. Full article

The global production of waste glass and the challenges associated with its reuse and disposal highlight the urgent need for effective alternatives to prevent the accumulation of landfill. Researchers have already explored the potential of replacing naturally quarried aggregates with waste glass to minimize its accumulation in landfills and the depletion of natural resources. Previous studies have reported that recycled crushed glass (RCG) has a high silica content, angularity, shear strength, and durability, properties which make it a promising material for construction applications. However, there are limited assessments in the existing literature of the performance of RCG as a construction material for transportation infrastructure. This paper reviews the physical, chemical, and geotechnical properties of RCG reported in the literature and compares their findings; it also discusses the existing studies related to its suitability for field applications. This paper also highlights the environmental impact and health concerns of replacing natural aggregates with waste glass by emphasizing its role in sustainable development and the circular economy in the construction of transportation infrastructure. Full article

Very large quantities of stone waste sludge are disposed in exhausted quarries and have a very low reuse rate to date. The paper considers the possibility of using these types of industrial waste in partial substitution of natural aggregates for the production of lime-based plasters. Traditional materials based on lime, the only material with a carbon neutrality life cycle, have considerable potential for use as components of green materials for plastering and finishing building surfaces in both new construction and historic heritage conservation. The paper presents the preliminary results of a research activity aimed at developing pre-packaged products based on Traditional Lime Putty (TLP) by partially replacing natural aggregates with Stone Waste Sludge (SWS), with a low rate of recovery from the Apricena limestone production district in Apulia. The mineralogical and chemical analysis carried out using XRD (X-Ray Diffraction), TG-DTA (Thermo Gravimetry-Differential Thermal Analysis), and hydrochloric acid attack test showed that the SWS consisted of 98.4 % CaCO₃ by mass. The particle sizes measured by laser diffraction technique are below 22.5 μm for the 92% mass of the sample. The high fineness of the stone waste was confirmed by the Blaine-specific surface method, which equals to 9273.79 cm²/gr. The behavior of three fresh mixtures for prepacked coarse plaster, fine plaster, and finishing plaster with 12.90%, 17.94%, and 18.90 by mass of SWS, respectively, was evaluated by spreading test and applicability tests on a perforated ceramic slab. The finishing plaster has the highest consistency value of 235 mm, while the fine plaster and the coarse plaster have values of 205 mm and 155 mm, respectively. The coarse plaster is suitable for use as base plaster (arriccio) or second layer rendering (tonachino) up to a thickness of approximately 1 cm. Both the fine plaster and finishing plasters can be used for the surfaces finishing with the application of layers of a few millimeters thick. Full article

Critical raw materials (CRMs) supply is a challenge that EU countries have to face, with many thinking about domestic procurement from natural ore deposits and anthropogenic deposits (landfills and extractive waste facilities). The present research focuses on the possibilities linked to the supply of CRMs and the potential for exploiting rare earth elements (REEs), investigating a large variety of extractive waste and siliceous rocks in the Piedmont region (Northern Italy). Indeed, the recovery of REEs from the extractive waste (EW) of siliceous quarries and other siliceous ore deposits can be a valuable way to reduce supply chain risks. Starting with a review of the literature on mining activities in Piedmont and continuing with the sampling and geochemical, mineralogical, petrographic, and environmental characterization of EW facilities connected to siliceous dimension stones, of kaolinitic gneiss ore deposits, and of soils present near the investigated areas, this study shows that the degree of REEs enrichment differs depending on the sampling area (soil or EW) and lithology. The concentration of REEs in the EW at some sampling sites fulfils the indicators of industrial-grade and industrial recovery; the high cumulative production and potential market values of EW and the positive recovery effects through proven methodologies indicate a viable prospect of REE recovery from EW. However, REE recovery industrialization faces challenges such as the difficulty in achieving efficient large-scale recovery due to large regional differences in REE abundance, the mismatch between potential market value and waste annual production, etc. Nonetheless, in the future, EW from dimension stone quarries could be differentially studied and reused based on the enrichment and distribution characteristics of trace elements. The present paper shows investigation procedures undertaken to determine both CRMs potentialities and environmental issues (on the basis of literature data employed to select the more-promising areas and on sampling and characterization activities in the selected areas), together with procedures to determine the waste quantities and tentative economic values of REEs present in the investigated areas. This approach, tested on a large area (Piedmont region), is replicable and applicable to other similar case studies (at EU and non-EU levels) and offers decision makers the possibility to acquire a general overview of the potential available resources in order to decide whether and where to concentrate efforts (including economic ones) in a more detailed study to evaluate the exploitable anthropogenic deposits. Full article

Chert, a by-product rock of sand quarrying, has historically posed economic challenges for aggregate production, resulting in significant “waste” accumulation in quarries. Our study investigates the effect of microwave irradiation on the mechanical properties of chert gravel, a mineralogically homogenous material composed of fine quartz grains. The results, which demonstrate that increased irradiation time leads to a substantial decrease in chert gravel strength (by a factor of 4–6 for 2.5 min of irradiation), underscore the potential impact of this research on comminution processes. With quenching altering the fractional content of the samples after the crushing test, reducing the Gravel-to-Sand ratio, this study is driven by the promising potential of crushed chert gravel as a pivotal aggregate within the concrete and asphalt industries, offering a practical solution to their material needs. The urgent need to rehabilitate previously utilized quarry areas, offering an environmentally beneficial solution for which we all should be responsible, motivated the present study. Full article

The mineral raw materials industry is crucial for European industry, with the European Economic and Social Committee estimating that 70% of the industry relies directly or indirectly on its supply. In the context of a decarbonized and digitalized economy, the new European industrial model requires carbon-neutral raw materials and production processes. The crucial role of aggregates mining, as the primary construction material, emerges as a key supplier in this paradigm. Aggregates are the main component of the built environment and are a social and economic engine in most countries. Quarries of this type include a wide range of sizes and exploitation methods and use characteristic mining and processing equipment. Quarries are commonly close to their processing plants, which transform natural rock into crushed and ground materials with different grain sizes depending on the future uses. The quarry itself and the presence of certain equipment and facilities help distinguish it from mining sites that exploit other materials. Effective management of aggregates quarries is important in promoting circular economy practices, ensuring efficient management, reuse, and recycling of diverse wastes, including the recovery of high-value components and the production of recycled aggregates, and addressing construction and demolition waste (DCW) management. As aggregates become a progressively scarcer resource due to the increasing demand from developing countries, it is essential to provide reliable and comprehensive information on their potential to the public, policymakers, and other stakeholders to promote their use. This study focuses on employing artificial intelligence and computer vision analysis to automatically identify aggregates quarries from satellite images within continental Spain. A model has been trained to detect aggregates quarries from satellite images by computer vision. The model permits the detection of mining exploitation and the objects located at the interior, which permits determination of the type of mine and the activity status of it. The findings highlight the ability of artificial vision to discern quarries and distinguish whether the observed feature is an aggregates quarry. Additionally, the technology allows for the determination of the quarry’s operational status, distinguishing between active and abandoned quarries. The ability to detect the locations of quarries and assess their activity statuses is of significant value for resource exploration initiatives and location-allocation assessments. It can be a valuable tool for authorities involved in land planning, activities monitoring, and early detection of potential illegal mining activities. This analytical approach demonstrates substantial potential for various stakeholders, including mining companies, mining authorities, policymakers, and land use planners in both the private and public sectors. Full article

Marble has been a prominent natural stone exploited since ancient times, commonly employed as a building material and ornamental stone. However, the disposal of waste generated from marble extraction, particularly fine sludge, poses significant environmental challenges for the dimensional stone industry. The difficulty in managing and recovering these materials, exacerbated by local regulations and the absence of suitable recovery protocols, often leads to landfilling. This issue is exemplified by the Carrara Marble Basin in the Apuan Alps (Tuscany, Italy), where more than half of the extracted marble remains as quarry waste or debris. Modern cutting technologies have intensified the production of finer materials and sawing residue, known as “marmettola”, ranging in size from fine sand to silt. The disposal of these materials, commonly through landfilling or abandonment, has profound environmental repercussions. This research primarily aimed to carry out a preliminary physical, mineralogical, and morphological characterization of the fine waste and sludges generated from Carrara Marble exploitation. The findings reveal the high granulometric uniformity of the materials, and a nearly pure carbonate composition, suggesting potential for reuse in various industrial sectors such as paper, plastics, and pharmaceuticals production. Full article

In northern Campania (Southern Italy), the historic center of many towns is characterized by the widespread presence of cavities in the subsoil, excavated over the centuries for quarrying tuff blocks for buildings, along with cathedrals, churches and chapels. A singular feature of these places of worship is, in fact, the presence of a wide and frequently connected network of underground cavities and tunnels, which were used for hydraulic, religious or connecting purposes. The cavity network is often unknown, abandoned or even buried, thus representing a risk for their susceptibility to sinkholes. Such elements are important as cultural heritage of inestimable value and as attractors for tourism; for this reason, the multidisciplinary study conducted on a place of worship in the Caserta area is illustrated herein: the Cloister of Sant’Agostino, in Caserta (XVI century CE). A geological and geotechnical characterization of the subsoil was performed at first. A laser scanner survey of the accessible cavities and the external churchyard was carried out. The resulting 3D model of the underground sector allowed for a clear understanding of the room size, their location, the levels and the path of the corridors. To understand the extension and layout of the crypts, Electrical Resistivity Tomography (ERT) surveys were undertaken in the surrounding areas. The analysis of the ERT measurements revealed some anomalies that could be ascribed to unknown structures (crypts). Finally, numerical methods were applied to estimate the stress state of the soft rocks and the potential areas of crisis, with preliminary assessments of the influence of the presence of cavities on the stability of the subsoil. The results allowed us to improve the knowledge of the study site and provide useful data for the planning of future targeted investigations, underlining how integrated research between applied disciplines can provide indispensable support both in the management and mitigation of geological risks in urban areas and in the sustainable reuse of hypogea. Full article

Ceramic slurry wastes have a significant hazardous potential when dumped. Their recycling as raw material is a sustainable approach for the development of nature-friendly applications. The microstructure and mechanical properties play a key role in the success of this sustainable recycling. Ceramic slurry samples resulting from the wall and floor tiles production facility were analyzed. The mineral composition was investigated by XRD combined with mineralogical microscopy and the microstructure was investigated by SEM microscopy coupled with EDX spectroscopy and elemental mapping. The ceramic slurry contains: quartz, kaolinite, mullite and small amounts of lepidocrocite. Quartz and mullite particles have sizes in the range of 5–100 μm and kaolinite has small particles of around 1 to 30 μm. Iron hydroxide crystallized as lepidocrocite is finely distributed among kaolinite aggregates. It makes the slurry unable to be reused in the technological process because of the glaze staining risk, but it does not affect the material cohesion. Thus, the cylindrical samples were prepared at progressive compactions rates as follows: 1808.55; 1853.46; 1930.79 and 2181.24 kg/m³ and dried. Thereafter, were subjected to a compression test with a lower compression strength of 0.75 MPa for lower density and a higher strength of 1.36 MPa for the higher density. Thus, slurry compaction enhances the kaolinite binding ability. The Young’s Modulus slightly decreases with the compaction increasing due to local microstructure rigidizing. This proves the binding ability of kaolinite, which properly embeds quartz and mullite particles into a coherent and resistant structure. The fractography analysis reveals that fracture starts on the internal pores at low compaction rates and throughout the kaolinite layer in the samples with high compactness. The observed properties indicate that the investigated ceramic slurry is proper as a clay-based binder for sustainable ecological buildings, avoiding the exploitation of new clay quarries. Also, it might be utilized for ecological brick production. Full article

The damming of watercourses results in sediment accumulation and, therefore, in the reduction of useful storage capacity. The storage capacity can be recovered through dredging, but this process generates large volumes of sediments that require proper management. To avoid landfilling and promote recovery operations, sediment characterization is the preliminary step to any assessment and decision. This paper presents the results of tests on sediments sampled at two reservoirs in southern Italy, the Camastra and the San Giuliano, in Basilicata. These investigations include testing of organic matter, heavy metals grain size distribution, and the assessment of the pollution degree. A lack of correlation between the sampling point and the heavy metal content was observed in sediments, except Be, Cr and Ni for the San Giuliano reservoir. This may be attributed to the presence of agricultural activities and fertilizer use in its watershed. Similarly, there is no dependence between the organic carbon and the grain size distribution, the former being scarcely found in both reservoirs (on average 0.91% for the Camastra sediments and 0.38% for the San Giuliano sediments), the latter being predominantly characterized by sandy matrices downstream of the reservoirs (on average 64.3% ± 32.9%) and by silty-clayey matrices in the upstream areas (on average 65% ± 14.3%). Finally, the determination of the single pollution index P_i and the Nemerow integrated pollution index P_N highlights that sediments are not contaminated with heavy metals. Most of them show values of the indices above between 0 and 1 (“unpolluted”) and, in a few cases, values between 1 and 2 (“poorly polluted”). The findings suggest that these sediments can be reused for environmental and material recovery, using them as secondary raw materials for sub-bases and embankments, for filling in disused quarries, for reprofiling and reconstructing the morphology of coastlines or riverbeds, for beach nourishment and in the agronomic and construction industry fields. Full article

The production of construction and demolition waste (CDW) in urban areas is growing rapidly. While the storage and disposal of CDW waste is costly, its recovery can help to conserve natural resources. This study investigates the characteristics of recycled sand obtained from the processing of CDW waste and the possibility of its reuse for pedestrian pathways. Physico-chemical and mineralogical characteristics of the recycled sand were investigated for its reuse. The percentage of fine particles in sand (below 0.63 μm) is 2.8%. The grain size of sand fulfills the particle size requirement of French standards. The methylene blue value of sand is 0.05 g/100 g. The GTR classification of recycled sand is D2 which is insensitive to water and suitable for road applications. A mineralogical analysis of soil shows that quartz, albite and microcline are important minerals in recycled sand. XRF analysis shows that CaO and SiO₂ are major oxides in the recycled sand. The characterization of sand was followed by a manufacturing of cylindrical specimens of sand to observe the compressive strength. Samples were compacted with dynamic compaction by applying the Proctor normal energy of 600 kN·m/m³. The compressive strength testing of specimens shows that non-stabilized sand samples have compressive strength around 0.1 MPa which is considerably lower for its reuse in pedestrian pathways and road applications. Due to the low bearing capacity of sand, recycled sand was stabilized with the addition of binders such as Rolac (hydraulic binder), ground-granulated blast furnace slag (GGBS) and ECOSOIL^® (slag mixes) with different percentages of the binder ranging from 0 to 7% for the optimization of the binder and for economic efficiency. The compressive strength of sand samples increases with the increasing percentage of the binder. The increase in strength is more important with a higher percentage of binders (5%, 6% and 7%). At a 7% binder addition, specimens with Rolac, GGBS and ECOSOIL binders show the compressive strength of 1.2 MPa, 0.5 MPa and 0.5 MPa. At a 7% Rolac addition, specimens have a compressive strength higher than 1 MPa and meet the strength requirement for soil reuse in the foundation and subbase layers of roads with low traffic. The experimental work shows that recycled sand can replace conventional quarry sand for road applications and pathways with the addition of a local binder, which is an eco-friendly and economical practice. Full article

In Campania (southern Italy), the widespread presence of anthropogenic cavities in the subsoil of the Neapolitan and Caserta provinces is well known. In these towns, the underground quarrying activities were performed for centuries to extract volcanic tuffs for buildings. The urban developments have sealed many signals of the presence of cavities and their real extent is almost unknown, thus representing a geological hazard and contributing to the subsoil instability of many places. This contribution will show the main cavity typologies recognized across an area north of Naples according to the geological characteristics of the subsoil. The main aim of the study is the cataloging of the cavities and the analysis of the city subsoil as their presence may easily trigger the collapse of the shallow or deeper soils. Moreover, the recognition and sustainable reuse of cavities contributes to enhancing the cultural and touristic promotion of a territory. In this study, a database framework was elaborated that includes all the possible architectural, geological and geotechnical elements of the cavities. Data were managed in a GIS environment in order to provide a useful tool for monitoring and managing the cavities for risk mitigation and tourism enhancement. Full article

Large areas become unsuitable for full-fledged life after mining activity. To improve the state of environmental safety of post-industrial landscapes and the rational use of disturbed territories, a Decision Support System (DSS) should be created. This system should also contain proposals for restoring the soil cover and plant communities that are proposed in this article. The purpose of this study is to determine the influence of arbuscular mycorrhizal fungi on the process of vegetation formation in the post-industrial landscape of a sulfur quarry. During reclamation works in human-made ecotopes, vegetation has already formed there in a certain way due to natural succession processes. We assessed the level of vegetation self-restoration and, on the basis of the obtained data, the need and direction of phytoreclamation in relation to specific ecotopes. The set of restoration of soil cover and plant communities makes it possible to solve the problem of reusing post-industrial landscapes. The positive effect of the treatment of seedlings with a spore remedy of arbuscular, mycorrhizal fungi on the studied breeds’ height increase was observed. In the process of the revitalization of disturbed landscapes through the mycorrhization of planting material, there is a tendency to restore and increase phytodiversity at the floristic and coenotic levels. Full article

The aim of this research was to evaluate the possibility of reusing waste foundry sands derived from the production of cast iron as a secondary raw material for the production of building materials obtained both by high-temperature (ceramic tiles and bricks) and room-temperature (binders such as geopolymers) consolidation. This approach can reduce the current demand for quarry sand and/or aluminosilicate precursors from the construction materials industries. Samples for porcelain stoneware and bricks were produced, replacing the standard sand contained in the mixtures with waste foundry sand in percentages of 10%, 50%, and 100% by weight. For geopolymers, the sand was used as a substitution for metakaolin (30, 50, 70 wt%) as an aluminosilicate precursor rather than as an aggregate to obtain geopolymer pastes. Ceramic samples obtained using waste foundry sand were characterized by tests for linear shrinkage, water absorption, and colorimetry. Geopolymers formulations, produced with a Si/Al ratio of 1.8 and Na/Al = 1, were characterized to evaluate their chemical stability through measurements of pH and ionic conductivity, integrity in water, compressive strength, and microstructural analysis. The results show that the addition of foundry sand up to 50% did not significantly affect the chemical-physical properties of the ceramic materials. However, for geopolymers, acceptable levels of chemical stability and mechanical strength were only achieved when using samples made with 30% foundry sand as a replacement for metakaolin. Full article