Search Results (134)

To elucidate the effects of iron ore tailings (IOTs) and basalt fiber (BF) on the durability of recycled aggregate concrete (RAC) with different recycled aggregate replacement rates, this study used IOTs to replace natural sand at mass replacement rates of 0%, 20%, 40%, 60%, 80%, and 100% and incorporated BF at volume fractions of 0%, 0.1%, 0.2%, and 0.3%. Carbonation and freeze–thaw cycle tests were conducted on C30 grade RAC. The carbonation depth and compressive strength of RAC at different carbonation ages and the mass loss rate, relative dynamic elastic modulus, and changes in compressive strength of RAC under different freeze–thaw cycle times were determined. Scanning electron microscopy (SEM) was utilized to meticulously observe the micro-morphological alterations of BF-IOT-RAC before and after carbonation. We then investigated the mechanisms by which BF and IOTs enhance the carbonation resistance of RAC. Utilizing the experimental data, we fitted relevant models to establish both a carbonation depth prediction model and a freeze–thaw damage prediction model specific to BF-IOT-RAC. Furthermore, we projected the service life of BF-IOT-RAC under conditions typical of northwest China. The results showed that as the dosages of the two materials increased, the carbonation resistance and frost resistance of RAC initially improved and then declined. Specifically, the optimal volume content of BF was ascertained to be 0.1%, while the optimal replacement rate of IOTs was determined to be 40%. Compared to using BF or IOTs individually, the composite incorporation of both materials significantly improves the durability of RAC while simultaneously enhancing the reuse of construction waste and mining solid waste, thereby contributing to environmental sustainability. Full article

The accelerated industrialization in China has precipitated a dramatic surge in solid waste generation, causing severe land resource depletion and posing substantial environmental contamination risks. Simultaneously, the cement industry has become characterized by the intensive consumption of natural resources and high carbon emissions. This review aims to investigate the current technological advances in utilizing industrial solid waste for cement production, with a focus on promoting resource recycling, phase transformations during hydration, and environmental management. The feasibility of incorporating coal-based solid waste, metallurgical slags, tailings, industrial byproduct gypsum, and municipal solid waste incineration into active mixed material for cement is discussed. This waste is utilized by replacing conventional raw materials or serving as active mixed material due to their content of oxygenated salt minerals and oxide minerals. The results indicate that the formation of hydration products can be increased, the mechanical strength of cement can be improved, and a notable reduction in CO₂ emissions can be achieved through the appropriate selection and proportioning of mineral components in industrial solid waste. Further research is recommended to explore the synergistic effects of multi-waste combinations and to develop economically efficient pretreatment methods, with an emphasis on balancing the strength, durability, and environmental performance of cement. This study provides practical insights into the environmentally friendly and efficient recycling of industrial solid waste and supports the realization of carbon peak and carbon neutrality goals. Full article

As a highly active mineral admixture, metakaolin is often used as an efficient performance-enhancing material for concrete, but its performance in long-term complex service environments still needs to be verified. This article presents a composite green concrete with a substitution rate of 30% for recycled coarse aggregates (RCAs) and iron tailings (IOTs) and a waste polypropylene fiber (WPF) content of 0.6%. Concrete with different mixing conditions of metakaolin was prepared, and its carbonization resistance was studied with macro- and micro-experimental methods. The results indicated that when the content of metakaolin was less than 10%, its mechanical and deformation properties gradually improved, resulting in a maximum increase of 70% in its cubic compressive strength. Overall, carbonization improved the corresponding mechanical properties. For example, when carbonized for 14 days, the compressive strength growth rate increased by nearly 30%, and the elastic modulus did not change significantly. Through microscopic testing, it could be seen that when the content of metakaolin reached 10%, an appropriate amount of metakaolin (10%) promoted the hydration of cement, with the least number of pores and the best compaction performance, resulting in the best overall performance. But when added excessively, the coupling effect of secondary hydration and carbonization reactions could lead to the emergence of new harmful pores in the matrix structure. In future engineering applications of metakaolin, it is recommended that its mixing ratio be less than 10% to achieve better concrete performance. Full article

There is no doubt that additive manufacturing (AM) with mortars presents an opportunity within the framework of a circular economy that should not be overlooked. The concepts of reduce, reuse, and recycle are fully aligned with this technology. One of the less explored possibilities is the utilisation of mining tailings as aggregates in printing mortars. This idea not only incorporates the concept of recycling but also contributes to a reduction in the production of potentially hazardous waste that would otherwise require storage in dams, thereby decreasing long-term environmental risks and improving the management of mineral resources. We employed a mortar composed of 12.5% material derived from mining tailings to highlight aspects of AM that are typically not subject to analysis, such as the necessity of considering contact interfaces between layers in structural design, the stackability of layers during the construction process, and the behaviour under fire and seismic events, which must be taken into account during the operational phase. Without aiming for exhaustiveness, we conducted a series of tests and computational modelling to show the significance of these factors, with the intention of drawing the attention of different stakeholders—including construction companies, regulatory authorities, standardisation agencies, insurers, and end-users. Full article

Geopolymer foam concrete (GFC) is a green, lightweight material produced by introducing bubbles into the geopolymer slurry. The raw materials for GFC are primarily silicon–aluminum-rich minerals or solid waste. Lead–zinc tailings (LZTs), as an industrial solid waste with high silicon–aluminum content, hold significant potential as raw materials for building materials. This study innovatively utilized LZTs to prepare GFC, incorporating MK, GGBS, and alkali activators as silicon–aluminum-rich supplementary materials and using H₂O₂ as a foaming agent, successfully producing GFC with excellent properties. The effects of different LZT content on the pore structure and various macroscopic properties of GFC were comprehensively evaluated. The results indicate that an appropriate addition of LZT effectively optimizes the pore structure, resulting in uniform pore distribution and pore shapes that are more spherical. Spherical pores exhibit better geometric compactness. The optimal LZT content was determined to be 40%, at which the GFC exhibits the best compressive strength, thermal conductivity, and water resistance. At this content, the dry density of GFC is 641.95 kg/m³, the compressive strength reaches 6.50 MPa after 28 days, and the thermal conductivity is 0.176 (W/(m·K)). XRD and SEM analyses indicate that under the combined effects of geopolymerization and hydration reactions, N–A–S–H gel and C–S–H gel were formed. The preparation of GFC using LZTs shows significant potential and research value. This study also provides a feasible scheme for the recycling and utilization of LZTs. Full article

This study proposes a sustainable method to convert high-silicon lead-zinc tailings (HS-LZT) into lightweight and high-strength ceramsite, aiming to address the issues of solid waste management and resource efficiency by using HS-LZT and kaolin as the main raw materials and silicon carbide (SiC) as the pore-forming agent. A sintering process was employed to prepare lightweight, high-strength ceramsite. X-ray diffraction (XRD), X-ray fluorescence (XRF), Thermogravimetric-differential scanning calorimetry (TG-DSC), and inductively coupled plasma optical emission spectrometer (ICP-OES) were used to analyze the physical composition and physical and chemical properties of the raw materials. The influence of raw material ratios, SiC content, sintering temperature, and sintering time on ceramsite properties was investigated, and the microstructure of the optimal finished ceramsite was analyzed. The results show that under optimal preparation conditions (70% [by mass percentage] of HS-LZT, 30% [by mass percentage] of kaolin, with an addition of 0.5% [by mass percentage] of SiC, a sintering temperature of 1200 °C, and a sintering time of 20 min), the LZT ceramsite achieved a compressive strength of 11.39 MPa, a bulk density of 724 kg/m³, and a 1 h water absorption rate of 4.82%. The leaching content of Pb and Zn of the sintered ceramsite samples is far less than the limit values of hazardous components in the leachate specified in the relevant standard. This study provides a potential pathway for the reduction, recycling, and environmentally sound utilization of HS-LZT, which is in line with the sustainable development concept of “treating waste with waste.” Full article

The historical industrial waste deposit Gater was used to dispose of different metallurgy wastes from lead and zinc production. The metallurgical waste deposit was situated in the open space, between the tailing waste deposit Žitkovac and river Ibar flow. Large amounts of lead-containing wastes are produced in the non-ferrous metallurgical industry, such as lead ash and lead slag generated in Pb smelting, lead anode slime, and lead sludge produced in the raw lead refining process. In addition to the lead concentration, numerous valuable components are found in the lead refinery waste from the group of Critical Raw Materials, such as antimony, arsenic, bismuth, copper, nickel, magnesium, scandium, as well as Rare-Earth Elements. Samples with eight characteristic points were taken to obtain relevant data indicating a possible recycling method. The chemical composition analysis was conducted using ICP; the scanning was completed using SEM-EDS. The mineralogical composition was determined by using XRD. The chemical analysis showed a wide range of valuable metal concentrations, from Ag (in the range from 14.2 to 214.6, with an average 86.25 mg/kg) to heavy metals such as Cu (in the range from 282.7 to 28,298, with an average 10,683.7 mg/kg or 1.0683% that corresponds to some active mines), Ni and Zn (in the range from 1.259 to 69,853.4, with an average 14,304.81 mg/kg), Sc (in the range from 2.4 to 75.3, with an average 33.61 mg/kg), Pb (in the range from 862.6 to 154,027.5, with an average 45,046 mg/kg), Sb (in the range from 51.7 to 18,514.7, with an average 2267.8 mg/kg), Ca (in the range from 167.5 to 63,963, with an average 19,880 mg/kg), Mg (in the range from 668.3 to 76,824.5, with an average 31,670 mg/kg), and As (in the range from 62.9 to 24,328.1, with an average 5829.53 mg/kg). The mineralogy analysis shows that all metals are in the form of oxides, but in the case of As and Fe, SEM-EDS shows some portion of elemental lead, pyrite, and silica-magnesium-calcium oxides as slag and tailing waste residues. The proposed recovery process should start with leaching, and further investigation should decide on the type of leaching procedure and agents, considering the waste’s heterogeneous nature and acidity and toxicity. Full article

The cleaning circuit of the collective Cu-Mo flotation plant at Collahuasi (north of Chile) consisted of two parallel flotation rows, each one of three first cleaner cells in series with six cleaner–scavenger cells. The second cleaner consisted of 10 parallel columns (6 rectangular and 4 circular), whose tailings were directly recycled to the first cleaner. Recently, a project was developed to upgrade the cleaning circuit by decreasing the large Mo circulating load and improving the cleaning circuit performance. For this purpose, a testing strategy was set up at a pilot scale to evaluate the use of intensified flotation (Jameson cells), mainly for collecting the fine Mo particles accumulated in the circulating load, which contributes to the Mo losses from the scavenger stage into the final tailings. The preliminary results regarding kinetics at the pilot scale showed good potential to improve the metallurgical performance of Mo and Cu, and a sensitivity study was carried out to evaluate the application of this technology in the industrial cleaning circuit. Then, two parallel Jameson cells were selected to re-treat the whole column tailings stream. This operation allowed for the generation of a direct final Cu-Mo concentrate (that joins the columns concentrate) while recycling their tailings to the first cleaner. After commissioning, three sampling campaigns were performed on the whole flotation plant, particularly on the overall cleaning circuit, to evaluate the impact of the new flotation cells. Results showed that the Jameson cells effectively decreased the minerals circulating loads in the cleaning stage, mainly for Mo (in 49%). The Jameson cells directly contribute 48% of Mo and 25% Cu of the minerals in the final concentrate and allow for increasing the Mo final grade (0.45% Mo vs. 0.29% from columns). These results were in good agreement with predictions from the pilot testing. Full article

Silicon–calcium–potassium–magnesium fertilizer (Si–Ca–K–Mg fertilizer), a critical acidic soil conditioner for remediating polluted acidic soils, encounters a significant challenge: substantial potassium loss through flue gas during high–temperature calcination, which increases production costs. This study optimized the blending ratio of molybdenum tailings (MTs) with CaCO₃ and CaSO₄, systematically investigating the interplay between clinker–soluble potassium, volatile potassium loss, and total activated potassium content during calcination. Key findings include the large–scale utilization of molybdenum tailings; a mass ratio of mMTs:mCaCO₃:mCaSO₄ = 1:0.5:1.0 leads to a total activated K₂O content of 3.05 wt.%. Enhancing nutrient efficiency by increasing the proportion of additives (with a mass ratio of 1:0.7:0.4) results in a total activated K₂O content of 4.50 wt.%, which is 1.5 times the national standard. Mechanistically, calcination decomposes potassium feldspar (K–feldspar) in the tailings into leucite and SiO₂. CaO derived from CaCO₃ reacts with SiO₂ to form calcium silicate, facilitating the decomposition of leucite into water–soluble kaliophilite. Simultaneously, thermal diffusion promotes the ion exchange between Ca²⁺ of CaSO₄ and K⁺ of feldspar and leucite, thereby forming potassium sulfate. However, part of this potassium sulfate, along with some water–soluble kaliophilite, volatilizes at high temperatures, contributing to flue gas loss. Recycling the lost potassium back into fertilizers enables complete potassium utilization. This work establishes a robust framework for efficiently producing Si–Ca–K–Mg fertilizer from molybdenum tailings, addressing key challenges in potassium retention and resource recycling during industrial synthesis. Full article

The increasing production of iron ore has led to the accumulation of iron ore tailings (IOTs), which pose significant environmental and safety risks when stored in tailings dams. This study investigates the potential of IOTs as a precursor in alkali-activated binder systems, aiming to provide a sustainable solution for mining waste management. Industrial calcium carbide lime and sodium silicate (Na₂SiO₃) were used as activators in varying concentrations (Na₂SiO₃: 10%, 15%, 20%, 25%, and 30%; carbide lime: 5%, 7.5%, and 10%), with curing conditions of 23 °C for 7 days. Techniques including unconfined compressive strength tests, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and metal leaching tests were employed to evaluate the mechanical performance and environmental safety of the alkali-activated binders. The results reveal that a mixture containing 20% Na₂SiO₃ and 10% carbide lime achieved the highest compressive strength of 0.33 MPa at 7 days. The binder also showed negligible metal leaching, meeting environmental safety standards. These findings confirm the viability of using IOTs in the development of durable, eco-friendly construction materials, offering a scalable and sustainable solution for the management of mining waste and promoting circular economy principles in the construction sector. Full article

Lead–zinc tailings are waste materials generated from mineral processing and smelting, and their long-term accumulation poses potential threats to the environment and soil. To achieve resource recycling and sustainable development, this study used lead–zinc tailings and clay as raw materials and glass powder as a modifier to prepare modified lead–zinc tailing sintered bricks. Through full-factor experiments and single-factor experiments, the effects of the material proportions, the sintering temperature, and the holding time on the properties of the sintered bricks were investigated. The results show that the addition of glass powder significantly enhanced the compressive strength of the sintered bricks, reduced their water absorption rate, and improved their volume shrinkage rate. The optimal preparation conditions were as follows: 9% glass powder content, 90% lead–zinc tailings content, a sintering temperature of 1060 °C, and a holding time of 60 min. The resulting sintered bricks met the MU30-strength-grade requirements of the national standard for ordinary sintered bricks (GB/T5101-2017). The sintering temperature has a significant impact on brick performance; the compressive strength first increases, and then decreases, the water absorption rate continues to decrease, and volume change shifts from expansion to contraction. The influence of holding time was relatively weaker, but as the holding time increased, the compressive strength and the water absorption rate of the sintered bricks gradually stabilized. XRD and SEM analyses indicated that the minerals in the lead–zinc tailings decomposed and recrystallized during the sintering process. The liquid phase melt from the glass powder filled the pores and enhanced skeletal strength, thereby improving the microstructure and properties of the sintered bricks. The research findings provide a theoretical basis and practical guidance for the efficient utilization and building material application of lead–zinc tailings. Full article

Zinc processing tailings (ZPTs) of the Kharzet Youcef processing complex, Setif, Algeria, are mainly stockpiled in tailing dumps without use, occupying significant surfaces and negatively influencing the human environment and health. Incorporating ZPTs into building materials manufacturing is an effective solution to meet the dual objectives of environmental protection and economic development. This study investigates the influence of firing temperature and integrating ZPTs as a partial replacement for clay on the physic-mechanical properties of fired clay bricks (FCBs). Microstructural, chemical, and mineralogical analyses of ZPTs and clay were carried out by SEM-EDS, XRF, and XRD, respectively. Seven mixtures were produced with various percentages of ZPTs added to clay (0%, 5%, 10%, 15%, 20%, 25%, and 30%) and were fired at two different temperatures (900 and 1000 °C) at a ramp rate of 5 °C. Physic-mechanical tests were carried out on different brick specimens, and the results obtained showed that the FCBs incorporated with 10% of ZPTs produced the highest flexural strength of 6.24 MPa, compressive resistance of 29.78 MPa, bulk density of 1.37 g/cm³, and water absorption of 15.1% at 900 °C. Therefore, the recycling of ZPTs for FCBs manufacturing is feasible and an effective alternative waste disposal solution for sustainable development while reducing negative environmental impacts. Full article

The present investigation introduces a novel approach, using As-Zn-Fe mining tailings (MT) and recycled bottle glass (cullet) to enable the manufacturing of a new glass for ornamental articles, with characteristics similar to those of soda–lime–silicate glass (SLS), and at the same time, immobilizing potentially toxic elements (PTEs) from mining tailings, which cause environmental pollution with severe risks to human health. The glass used was obtained from transparent glass bottles collected from urban waste, which were later washed to remove impurities and then crushed until they reached No. 70 mesh (212 μm) level; in the case of mining tailings, the sample used comes from the ore benefit process, with 96.8% of particles below the No. 50 mesh level (300 μm). Six mixtures were made by varying the composition of the mining tailings and glass, K₂CO₃ and H₃BO₃ as fluxes were also used in constant proportion. The mixtures were melted at 1370 °C, and later, the glass samples were cast on a steel plate at room temperature. The characteristics of the glasses were studied using thermal analysis (TA), X-ray diffraction (XRD), Fourier transform infrared (FTIR), and scanning electron microscopy (SEM). Likewise, their chemical resistance in acid and basic media and density were evaluated. The results unequivocally demonstrate the feasibility of manufacturing glasses with a light green color, the increase in the content of mining tailings increased the apparent T_g from 625 to 831 °C. Glasses with 17 and 21.3% MT presented lower density values due to a better-polymerized glass structure, attributed to the increase in SiO₂ and Al₂O₃ and the decrease in alkaline oxides, which allowed for the retention of PTEs in their structure. Full article

Concrete is known for its high structural performance and workability, but its environmental impact is significant in terms of the utilization of virgin resources and greenhouse gas emissions. To mitigate the negative climate effects of concrete, it is essential to continuously develop and adopt eco-friendly practices in the construction sector. This paper provides an overview of current practices, opportunities, and challenges for developing and adopting eco-friendly concrete. Promising paths for eco-friendly concrete construction include using supplementary cementitious materials (SCMs) instead of energy-intensive traditional cement, incorporating locally available, waste-based materials rather than virgin resources, adopting recycling and reusing techniques, employing advanced technologies, such as performance-enhanced concrete and carbon capture and utilization techniques, etc. Among the studied materials, some waste materials such as rice husk ash, mine tailings, and municipal solid waste ash have found potential and demand further research. The adoption of new materials in concrete and attributing them in practices faces significant social, economic, and regulatory challenges. Addressing these obstacles requires interdisciplinary research and development, the establishment of clear standards and incentives, and educating skilled professionals and efforts to raise social awareness. Full article

Tailings ponds can recycle water resources through the water recirculation system by clarifying and purifying the wastewater discharged from the mining production process. Due to factors such as flooding and heavy rainfall, once a tailings dams burst, the spread of heavy metals in the tailings causes underground and surface water pollution, endangering the lives and properties of people downstream. To effectively assess the potential impact of tailings dams bursting, many problems such as the difficulty of taking values in predicting the volume of silt penetration through empirical formulae, model testing, and numerical simulation need to be solved. In this study, 65 engineering cases were collected to develop a sample dataset containing dam height and storage capacity. The Support Vector Machine (SVM) algorithm was used to develop a nonlinear regression model for tailings discharge volume after tailings dam failure. In addition, the model penalty parameter C and kernel function g were optimized using the powerful global search capability of the Slime Mold Algorithm (SMA) to develop an SMA–SVM prediction model for tailings discharge volume. The results indicate that the volume of tailings discharged increases nonlinearly with increasing dam height and tailings storage capacity. The SMA-SVM model showed higher prediction accuracy compared to the predictions made by the Random Forest (RF), Radial Basis Function (RBF), and Least Squares SVM (LS-SVM) algorithms. The average absolute error in tailings discharge volume compared to actual values was 30,000 m³, with an average relative error of less than 25%. This is very close to practical engineering scenarios. The ability of the SMA-SVM optimization algorithm to produce predictions with minimal error relative to actual values was further confirmed by the combination of numerical simulations. In addition, the numerical simulations revealed the flow characteristics and inundation area of the discharged sediment during tailings dam failure, and the research results can provide reference for water resource protection and downstream safety prevention and control of tailings ponds. Full article