Search Results (118)

The disposal of tunnel waste slag has emerged as a major ecological challenge. Highway pavement bases require large quantities of graded crushed stone as fill material, but large-scale quarrying of such stone also poses significant environmental problems. An innovative approach involves crushing tunnel waste slag into graded crushed stone for use as fill material, offering an economical and environmentally friendly solution to both issues. However, the performance of this recycled graded crushed stone needs to be carefully evaluated. This study employed particle flow analysis software to simulate the California Bearing Ratio (CBR) test process, followed by analysis and verification to assess its performance. A CBR model was developed and validated, the meso-mechanical parameters of the penetration process were analyzed, and the results were examined in terms of both CBR values and particle contact force fields. The findings indicated that different particle stiffness ratios $k_n/k_s$ had no significant effect on the CBR test, while the friction coefficient $\mu$ showed a linear positive correlation with the CBR value. It was also concluded that the slenderness ratio of the contact force field first increased and then decreased with an increase in the stiffness ratio $k_n/k_s$. As the friction coefficient $\mu$ increased, the slenderness ratio of the contact force field decreased accordingly. This study provides valuable insights into the influence of meso-mechanical parameters on the performance indicators of graded crushed stone pavement and offers a promising approach for the processing and reuse of tunnel waste slag to alleviate ecological pressures. Full article

Worldwide, large volumes of industrial residues, such as water treatment sludge (WTS), biomass ash (BA), iron slag (IS), and quarry fines (QF), are generated with limited reuse. This study evaluates their potential as additives for two soils, using two types of soils as matrices. A comprehensive laboratory program (particle size distribution, Proctor compaction, Atterberg limits, falling-head permeability, oedometer consolidation, consolidated undrained triaxial tests, and scanning electron microscopy) was performed on soil–residue mixtures across practical dosages. Optimal mixes balanced strength and transport properties: 15% WTS lowered hydraulic conductivity (k) into the 10⁻⁹ m/s range while reducing plasticity; 20% BA rendered the soil non-plastic but increased k into the 10⁻⁸–10⁻⁷ m/s range; 50% IS increased friction angle while maintaining k ~10⁻⁸ m/s; and QF produced modest changes while preserving k ~10⁻⁹ m/s. These findings support the sustainable reuse of these industrial wastes for soft soil stabilization, also contributing to the circular economy in the industrial and construction sectors, and are aligned with the United Nations’ sustainable development goals 6, 9, 11, 12, and 15. Full article

This study explores a sustainable strategy for enhancing high-strength concrete (HSC) by partially replacing natural fine aggregates with stone quarry sludge (SQS), a byproduct of quarrying operations. The aim is to promote environmental conservation and waste valorization while maintaining or improving concrete performance. Concrete mixes were prepared by substituting fine sand with SQS at incremental levels of 10%, 20%, 30%, 40%, and 50%. Mechanical properties were assessed through specific weight measurements, compressive strength tests, and three-point bending evaluations. FTIR analysis was conducted to investigate microstructural changes, and a carbon footprint assessment was performed to quantify environmental benefits. The mix containing 20% SQS exhibited optimal performance, achieving a compressive strength of 61 MPa and a bending strength of 5.1 MPa. FTIR results confirmed enhanced C–S–H gel formation, indicating improved microstructural integrity. Carbon footprint analysis revealed that moderate SQS substitution significantly reduces embodied carbon. These findings support the use of quarry sludge as a viable component in eco-friendly HSC, with potential for further optimization and long-term durability studies. Full article

One of the environmental concerns today is the increasing amount of waste generated from marble quarrying and processing. This study evaluates the mechanical and durability properties of marble waste-modified rigid pavement material. A series of laboratory tests was conducted to obtain the properties of marble waste-modified rigid pavement material. The slump value decreases as the percentage of marble waste increases. As the percentage of marble waste increases, the dry density gradually decreases from 2770 kg/m³ to 2590 kg/m³. Comparison of the 7-day and 28-day compressive strength indicates that replacing the gravel with marble waste resulted in early strength gain, making it suitable for use in conditions that require early strength gain. The scanning electron microscopy results indicated higher calcium content for the 10% marble waste sample, which is responsible for the cementation and supports the higher compressive strength obtained for the sample at 7 days of curing, due to early strength gain. The study is the first to show the synergistic effect of marble waste on early strength and durability in rigid pavements. These findings showed that marble waste can be used as a modifier in rigid pavement materials. The study contributes to Sustainable Development Goals 9 and 11. Full article

The limestone quarrying and processing industry generates huge amounts of waste, with limestone sludge being one of the most prevalent and challenging by-products. This study aims to evaluate the potential of limestone sludge as a sustainable secondary raw material for the mechanochemical synthesis of bioceramics, specifically hydroxyapatite (HA), for high-added-value applications in bone tissue engineering. High-energy milling is innovatively used as the processing route: dry sludge (functioning as the calcium source), a phosphate source, and water were milled with the aim of producing calcium phosphates (in particular, hydroxyapatite) via mechanosynthesis. The industrial sludge was thoroughly analyzed for chemical composition, heavy metals, and mineral phases to ensure suitability for biomedical applications. The mixture of reagents was tailored to comply with Ca/P = 1.67 molar ratio. Milling was carried out at room temperature; the milling velocity was 600 rpm, and milling time ranged from 5 to 650 min. Characterization by XRD, Raman spectroscopy, and SEM confirmed the progressive transformation of calcite into hydroxyapatite through a metastable DCPD intermediate, following logarithmic reaction kinetics. The resulting powders are fine, homogeneous, and phase-pure, demonstrating that mechanosynthesis provides a low-cost and environmentally friendly pathway to convert limestone waste into functional bioceramic materials. This suggests that Moleanos sludge is a viable and sustainable source to produce tailored calcium phosphates and confirms mechanosynthesis as a cost-effective and reliable technology to activate the low-kinetics chemical reactions in the CaCO₃-H₃PO₄–H₂O system. This work highlights a novel circular economy approach for the valorization of industrial limestone sludge, turning a difficult waste stream into a high-value, sustainable resource. Full article

Growing concerns about industrial waste have intensified the search for practical reuse strategies in the construction industry. One of the most problematic types of waste is decommissioned wind turbine blades, which are tough, lightweight glass fibre composites that resist conventional recycling. In this study, shredded glass fibre-reinforced polymer (GFRP) recovered from such blades was used to partially replace the 2–8 mm fraction of natural aggregate in concrete at 10%, 20%, 30%, and 40% by volume. X-ray fluorescence (XRF) analysis showed that the material consists mainly of SiO₂, CaO, and Al₂O₃. X-ray computed tomography (XCT) revealed uneven fibre dispersion and a clear increase in porosity. Compared with the control mix, compressive strength reduced by 7–25%, splitting tensile strength by 18–24%, and elastic modulus by 17–35%. All mixes achieved watertightness class W12 (1.2 MPa), though the depth of water penetration increased with GFRP content. After 50 freeze–thaw cycles, frost-resistance class F50 was only met at 10% replacement. While these trends underline the performance trade-offs, they also point to a realistic route for diverting composite waste from landfills, reducing reliance on quarried aggregate and producing ‘green’ concretes for non-structural, prefabricated elements, where moderate strength is acceptable and reducing weight is advantageous. Full article

The construction industry increasingly integrates technological advancements to enhance efficiency and meet technical, environmental, and economic requirements. Self-compacting mortars are gaining popularity due to their superior fluidity, optimized compaction, and improved mechanical properties. This study explores the potential of statistical mix design methodology to optimize self-compacting mortars’ fresh properties and strength development by replacing up to 20% of cement with pozzolana, limestone, and marble powder. A self-compacting mortar repository was used to develop robust models predicting slump flow, compressive strength at 28 days, water absorption, and capillary absorption. Results indicate that marble powder mixtures exhibit superior slump flow, up to 9% higher than other formulations. Compressive strengths range from 50 MPa to 70 MPa. Pozzolana and marble-based mortars show 15% and 12% strength reductions compared to the limestone-based mix, respectively. Water absorption increases slightly for mortars with marble (+2%) or pozzolana (+3%). The mortar containing marble powder has the lowest sorptivity coefficient due to its high specific surface area. The statistical analysis was conducted using a mixture design approach based on a second-order polynomial regression model. ANOVA results for the studied responses indicate that the calculated F-values exceed the critical thresholds, with p-values below 0.05 and R-squared values above 0.83, confirming the robustness and predictive reliability of the developed models. Life cycle assessment reveals that cement production accounts for over 80% of the environmental impact. Partial replacement with pozzolana, limestone, and marble powder reduces up to 19% of greenhouse gas emissions and 17.22% in non-renewable energy consumption, demonstrating the environmental benefits of optimized formulations. Full article

Macrophytes are important components of aquatic ecosystems performing essential ecological functions. Their species composition and density reflect the ecological status of water bodies. The optimal ratio of morphological types of macrophytes is an important condition for preventing eutrophication. The aim of the study is to analyse the species composition, distribution, and density of macrophytes in the Vyzhyvka River (Ukraine) in a seasonal aspect (2023–2024) under constant physical and chemical characteristics of water. To assess the seasonal dynamics of water quality, changes in indicators in three representative areas were analysed. The MIR method of environmental indexation of watercourses was used to assess the ecological state of the river. The water quality in the Vyzhyvka River at all test sites corresponds to the second class of the “good” category with the trophic status of “mesotrophic”. This is confirmed by the identified species diversity, which includes 64 species of higher aquatic and riparian plants. Among the various morphological types of macrophytes, submerged rooted forms account for only 10.56% of the total species composition. To ensure a functional balance between submerged and other forms of macrophytes, a scientifically based approach is proposed, which involves the use of mineral raw materials of local origin, in particular, mining and quarrying wastes rich in silicon, calcium and other mineral components. The results obtained are of practical value for water management, environmental protection, and ecological reclamation and can be used to develop effective measures to restore river ecosystems. Full article

Italy supplies about one-seventh of the European Union’s total glass production, and the sector’s sizeable resource demands make it a linchpin of national industrial strategy. With growing environmental regulations and the push for resource efficiency, Material Flow Accounting has become essential for companies to stay compliant and advance sustainability. The investigation concentrates on Italy’s glass industry to clarify its material requirements, ecological footprint, and overall sustainability performance. STAN software v2, combined with an Economy-Wide Material Flow Accounting (EW-MFA) framework, models the national economy as a single integrated input–output system. By tracking each material stream from initial extraction to end-of-life, the analysis delivers a cradle-to-grave picture of the sector’s environmental impacts. During the 2021 production year, Italy’s glass makers drew on a total of 10.5 million tonnes (Mt) of material inputs, supplied 76% (7.9 Mt) from domestic quarries, and 24% (2.6 Mt) via imports. Outbound trade in finished glass removed 1.0 Mt, leaving 9.5 Mt recorded as Domestic Material Consumption (DMC). Within that balance, 6.6 Mt (63%) was locked into long-lived stock, whereas 2.9 Mt (28%) left the system as waste streams and airborne releases, including roughly 2.1 Mt of CO₂. At present, the post-consumer cult substitutes only one-third of the furnace batch, signalling considerable scope for improved circularity. When benchmarked against EU-27 aggregates for 2021, Italy registers a NAS/DMI ratio of 0.63 (EU median 0.55) and a DPO/DMI ratio of 0.28 (EU 0.31), indicating a higher share of material retained in stock and slightly lower waste generated per ton of input. A detailed analysis of glass production identifies critical stages, environmental challenges, and areas for improvement. Quantitative data on material use, waste generation, and recycling rates reveal the industry’s environmental footprint. The findings emphasise Economy-Wide Material Flow Accounting’s value in evaluating and improving sustainability efforts, offering insights for policymakers and industry leaders to drive resource efficiency and sustainable resource management. Results help scholars and policymakers in the analysis of the Italian glass industry context, supporting in the data gathering, while also in the use of this methodology for other sectors. 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

In order to alleviate the risk of landslides on high and steep slopes during excavation, slope protection coal pillars are commonly increased at the site to maintain slope stability, which causes a considerable waste of coal. In roof cutting for pressure relief at quarries, the movement of the overburden structure is artificially regulated by blasting. However, there is a lack of theoretical research on the impact on the slope movement. In order to explore how blasting roof cutting affects the deformation and fracture of slopes, a case study of the 10101 working face of Xinyuan Coal Mine was carried out. The particle flow code numerical simulation of the mining with different heights of roof cutting was performed to analyze the impact of the height of roof cutting on the movement of overlaying rock formation, the development of slope fractures, stress distribution, collapse angle, slope deformation and fracture, etc. The research results are as follows: the overlaying rock formation can be divided into the stable zone, the rotary zone and the subsidence area by displacement; a reasonable roof-cutting height allows the cutting and crushing of the overlaying rock formation, as a result of which the movement boundary is offset to cutting line and the slope is within the stable area; at the same time, the horizontal displacement of the rock formation in the rotary zone, the collapse angle and the stress at slope bottom are reduced, which controls the deformation and failure of slope by inhibiting the development of cracks at slope bottom and reducing the rotation of the rotary zone to the goaf zone. The research results provide certain references for controlling ground sedimentation and slopes in blasting roof cutting. Full article

Chert gravel, a byproduct of sand quarrying, remains an underutilized material in construction due to its low microwave (MW) absorption and high mechanical strength. The present study deals with the potential of MW irradiation as a novel, energy-efficient method for processing chert gravel into high-quality aggregates, reducing reliance on virgin materials. The research systematically examines MW exposure duration (1–2.5 min), rock size (150–800 g), moisture conditions, and cooling methods (air vs. water quenching) to optimize fragmentation. Experimental results indicate that larger rock sizes (600–800 g) yield coarser, less uniform aggregates, while prolonged MW exposure (>2 min) induces extensive micro-fracturing, producing finer, well-graded particles. Water quenching significantly intensifies fragmentation, generating irregular but highly fragmented aggregates, whereas pre-wetted samples exhibit finer and more uniform breakage than dry samples. The findings introduce a novel approach for optimizing chert gravel fragmentation, a material previously considered unsuitable for MW treatment. The study proposed a customizable methodology for tailoring aggregate properties through precise control of MW parameters, offering a sustainable alternative to conventional crushing. The results contribute to resource conservation, reduced energy consumption, and climate change mitigation, paving the way for more sustainable construction practices. 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

The disposal and recycling of industrial by-products such as marble and limestone powders pose pressing environmental challenges due to the substantial amounts of waste generated annually by marble processing plants and limestone quarries. The integration of these by-products into concrete production is justified by their widespread availability and the potential to alleviate the environmental burden. This study used a statistical mixture design approach to systematically assess the effects of limestone and marble powders, with varying fineness levels, as partial cement replacements (up to 17%) on the rheological and mechanical properties of self-compacting concrete (SCC). The experimental findings revealed that the density of the SCC mixtures ranged from 2475 to 2487 kg/m³. Mixtures incorporating limestone powder exhibited superior flowability, achieving a slump flow of up to 69 cm, an 8% improvement compared to those containing marble powder. However, marble powder with a specific surface area of 330 m²/kg demonstrated significant improvements in compressive and tensile strengths, with increases of 18%. Statistical analysis using analysis of variance (ANOVA) validated the reliability of the predictive models developed, which demonstrated coefficients of determination (R²) that exceeded 0.94 and p-values below 0.05. These models enable precise predictions of critical performance metrics, including density, slump flow, box flow, compressive strength, and tensile strength, thus reducing the need for extensive experimental procedures. Full article

The excessive use of materials that are generally difficult to discard, such as stone materials, has caused growing ecological concern. Among these, marble is extracted from quarries, but when the raw material is exhausted, these places are deserted. For this reason, several measures have been adopted in recent years to requalify these areas. In addition, recent technological developments involve the creation of innovative green materials that privilege the circular economy and waste recycling. This research presents the development of innovative, sustainable filaments for the fused filament fabrication (FFF) printing technique from recycled marble waste (MW) and biocompostable and biodegradable polylactic acid (PLA) matrix. MW was added to the polymer in concentrations of 10 wt.%, 20 wt.%, and 30 wt.%, and the blends were extruded to develop innovative green filaments. The chemical/structural properties of the raw materials and the thermal and mechanical features of the new composites were investigated. Composites containing 10 and 20 wt.% of MW showed good printability. In contrast, extrusion and printing difficulties were observed with 30 wt.% of MW. Finally, this paper proposes a project to renaturalize and requalify a disused marble quarry located in Trani (Apulia, Italy) with 3D printing devices using the newly produced eco-filaments, which have better features. The main purpose of this article is to propose a concrete, economic, and sustainable application of 3D printing involving processes such as waste and by-product recycling and renaturalization of disused quarries, with both economic and environmental benefits. Full article