Search Results (1,204)

Barium slag is classified as a hazardous waste due to its high content of soluble Ba²⁺. To achieve safe disposal and high-value utilization, this study developed a novel all-solid-waste road base material by synergistically combining harmlessly treated barium slag (HTBS) with steel slag, blast furnace slag, and flue-gas-desulfurization gypsum (SWB). The primary novelty of this work lies in the dual-immobilization mechanism of barium within a multi-solid-waste cementitious system. Our results showed that the mixture containing 16% binder achieved unconfined compressive strengths of 4.24 MPa (7 days) and 8.06 MPa (28 days), meeting the technical requirements for heavy-load road bases. Microstructural analyses revealed that the system evolved into a dense network composed of C–S–H gels and ettringite (AFt). Mechanistically, environmental safety is ensured by two pathways: (1) the chemical precipitation of stable BaSO₄ and (2) the physical encapsulation of ions by the dense gel matrix. Leaching tests confirmed that Ba concentration remained far below the regulatory limit, ensuring environmental safety. This work provides a scalable, eco-friendly solution for the “waste-to-resource” conversion of hazardous barium slag in road engineering. Full article

The increasing emphasis on sustainability in construction materials has led to a surge of research focused on recycled aggregate self-compacting concrete (RA-SCC). However, the critical gap in predicting the compressive strength of concrete remains challenging because of the nonlinear interactions among the mix’s constituents. The distinct contribution of this study is to develop an interpretable machine learning (ML) framework to accurately forecast the compressive strength of RA-SCC and identify the most influential mix parameters. A dataset comprising 400 experimental samples was compiled, incorporating eight input variables: age, cement strength, cement, fly ash, blast furnace slag, water, recycled aggregate, and superplasticizer, with compressive strength as the output variable. Four ML algorithms such as support vector regression (SVR), random forest (RF), Multilayer Perceptron (MLP), and extreme gradient boosting (XGBoost) were trained and optimized using Bayesian-based hyperparameter tuning combined with 10-fold cross-validation. Among the evaluated models, XGBoost demonstrated superior accuracy, with R² = 0.98 and RMSE = 2.95 MPa during training, and R² = 0.96 with RMSE = 3.25 MPa during testing, confirming its robustness and minimal overfitting. SHAP (SHapley Additive exPlanations) evaluation indicates that superplasticizer, cement, and cement strength were the most dominant factors influencing compressive strength, whereas higher water content showed a negative impact. The developed framework demonstrates that explainable ML can effectively capture the complex nonlinear behavior of RA-SCC, offering a reliable tool for mix design optimization and sustainable concrete production. These findings contribute to advancing data-driven decision making in eco-efficient materials engineering. Full article

In the research, the effect of basaltic pumice powder on the mechanical and thermal resistance properties of alkali-activated mortars (AAM) was studied. The class F fly ash, basaltic pumice powder (BPP), and ground granulated blast furnace slag were utilized as sustainable binder materials. The BPP was incorporated instead of fly ash and slag at concentrations of 10, 20, 30, 40, and 50%. In addition, the effects of different sodium hydroxide (NaOH) molarities (8, 12, 16 M) were investigated on the thermal resistance properties. The influence of curing time and its effects on different elevated temperatures (200, 400, and 600 °C) were also studied together at 7, 28, and 56 days on the AAMs. Flexural strength, compressive strength, weight change, and ultrasonic pulse velocity tests were carried out at the macro-scale. The microstructures of the AAM samples were analyzed using SEM and EDX spectroscopy. The results showed that dissolution of basaltic pumice particles requires a longer curing time. The 50% pumice-incorporated 8 M samples at 7 d exhibited the worst, whereas 16 M samples without pumice at 56 d performed the best in terms of mechanical strength and thermal durability. The optimal formulation for the best elevated temperature resistance is the 30% BPP and 16 M NaOH molarity. Full article

To improve dynamic thermal measurement accuracy on aero-engine hot-section components, integrated heat flux/temperature thin-film sensors (TFHFs) were fabricated using micro-nano technology. This study simulated and compared the time constant calibration of the TFHFs’ temperature component under step laser heating and step furnace heating, demonstrating the necessity of power feedback control in laser-based dynamic calibration. Factors influencing the dynamic response of the heat flux component under both radiation and convection were also analyzed. A laser-based test platform with constant-temperature feedback control was developed to validate the simulations. Tests revealed that overshoot in the heat flux response originates from non-ideal longitudinal heat transfer, while the feedback control reduced the temperature time constant by at least half (At the 1000 °C step steady state, the time constant decreased from 2 s to 0.85 s), overcoming the challenge of inaccurate calibration due to non-steady conditions. High-speed wind tunnel tests under convective conditions confirmed that the dynamic response of TFHFs is predominantly influenced by flow velocity. The study enables accurate dynamic measurement of composite thermal parameters under varied thermal boundaries. Full article

Utilizing waste red-clay brick powder (WRCBP) as a precursor for manufacturing geopolymers is increasingly popular due to its environmental and economic benefits. However, the geopolymerization of this waste remains insufficiently explored. This study evaluates the differences in physical–mechanical properties and microstructural evolution of WRCBP- and fly ash (FA)-based geopolymers to determine the reactivity of WRCBP. Mineral admixtures, including granulated blast furnace slag (GF) and metakaolin (MT), were incorporated with WRCBP to fabricate geopolymer pastes, while FA was used in parallel for comparison. The effects of activator modulus (1.2 and 1.4 for Na₂SiO₃) and curing conditions (65 °C and 90 °C) on the mechanical and microstructural performance of the prepared pastes were investigated through water demand analysis, compressive strength testing, mercury intrusion porosimetry (MIP), and scanning electron microscopy (SEM). The results indicate that WRCBP-based pastes achieved a comparable compressive strength (39.8 MPa) under appropriate alkali-activated and curing conditions relative to FA-based pastes (42.5 MPa). The modulus of the alkaline activator exerted a greater influence on strength development than the raw material composition. For both WRCBP- and FA-based pastes, 65 °C was identified as a more suitable curing temperature. Moreover, compared with FA-based pastes, pastes produced using WRCBP provide enhanced social and economic benefits. Overall, this study confirms that high-performance binders can be engineered by incorporating WRCBP, thereby supporting the development of sustainable low-carbon construction materials. Full article

Achieving adequate frost resistance in cementitious composites made with low-clinker binders remains challenging, as conventional air-entraining admixtures often show limited effectiveness in such systems. This study examines an alternative approach that involves incorporating preformed polymeric microspheres to create a stable air–void system and enhance freeze–thaw durability. Cementitious composites were prepared using a low-clinker binder containing fly ash and ground granulated blast furnace slag (GGBFS) as supplementary cementitious materials, with natural sand partially replaced by fine recycled aggregate derived from concrete waste. The influence of polymeric microspheres on workability, compressive strength, pore structure, and frost resistance was evaluated. Compared to the reference mixture (32.8 MPa), the mortar modified with polymeric microspheres exhibited clearly higher compressive strength—about 25% greater after 28 days—while the AEA-modified mixture showed a slight reduction. Total porosity measured by MIP was 18% for REF, 19% for AEA, and 17% for PPMThe results showed that adding polymeric spheres initially introduced a network of discrete voids that improved the material’s resistance to early freeze–thaw cycles. However, due to the prolonged hydration of the low-clinker system, hydration products progressively filled the initially created voids after the partial degradation of the polymeric spheres. Consequently, the air–void system gradually disappeared, leading to a loss of frost resistance at later ages. After 100 cycles, the PPM mixture exhibited a 75% loss in flexural strength and a 35% loss in compressive strength, whereas the AEA mixture retained its durability, with compressive strength loss limited to 6%. This finding suggests that, although early tests may indicate improved performance, the long-term durability of low-clinker cementitious composites incorporating fine recycled aggregate cannot be reliably enhanced by preformed polymeric spheres alone. Full article

This article reports results of the geoarchaeological investigation of an early historical bloomery iron smelting site in northern Central Europe. Based on earlier field archaeological and experimental archaeological findings, which date back to an excavation in Sehnde (Hanover Region, Lower Saxony, Germany) in 2017, further experimental archaeological iron smelting experiments (furnace runs) have now provided information about the raw materials used in Sehnde during the Early Roman Imperial Period in Germania Magna (Inner Barbaricum) and the smelting process itself. The results of the present study suggest that no bog iron ore (BIOre) was smelted. Rather, manganese-rich carbonatic clay ironstone concretions (OCISCs) that had been oxidized by weathering and that were very rich in iron were apparently used as ores. Our study provides insights into metallurgical operations in the southern North German Plain during the Early Roman Imperial Period using a sampling and experimental archaeological test design created specifically for the local conditions. Full article

Reactive Powder Concrete (RPC) is widely recognized for its high strength and durability, yet its dependence on large amounts of Portland cement (PC) and silica fume (MS) raises environmental and economic concerns. This study explores the combined incorporation of milled electric arc furnace slag (MEAS) and calcium carbonate powder (CCP) as partial substitutes for cement and MS in RPC, employing a Central Composite Design (CCD) to optimize cement dosage, water-to-binder ratio, and polycarboxylate ether (PCE) content. Particle packing was guided by the Modified Andreasen–Andersen (MAA) model. The experimental program included 20 mixtures, evaluating rheological performance through slump flow and mechanical strength at 1, 7, 14, and 28 days. Incorporating MEAS (up to ≈20% of the binder) and CCP (≈15%) improved workability, with slump flow values reaching ≈285 mm compared to ≈230 mm for the baseline mixture. The optimal formulation achieved a 28-day compressive strength of ≈152 MPa, comparable to the reference RPC (≈138 MPa), while reducing cement consumption by ≈15% and MS by ≈50% relative to conventional dosages. Quadratic response surface models for slump flow and compressive strength at 1–28 days showed excellent goodness of fit (R² = 0.90–0.98, adjusted R² = 0.85–0.96; model F-tests p < 0.001), confirming the adequacy of the statistical optimization. Moreover, statistical analysis confirmed that cement dosage was the dominant factor for strength development (p < 0.05), while the interaction between cement content and water-to-binder ratio significantly influenced flowability. These results demonstrate the potential of MEAS and CCP to lower binder demand in RPC without compromising mechanical performance, advancing sustainable alternatives for ultra-high-performance concrete. Full article

The article presents a method of measurement and a test stand for determining the specific electrical resistivity of granular carburizing materials most commonly used in foundry practice. The research was conducted for synthetic graphites (GS) and petroleum cokes (KN) using a test stand proposed by the authors of the study and protected by a patent. It was shown that this measurement method allows for a clear distinction between the tested materials. For synthetic graphites, specific resistivities in the range of 35.9–144.5 μΩ·m were obtained, while for petroleum cokes the range was 172.1–1390 μΩ·m. The main aim of the study was to determine whether there is a correlation between the measured electrical resistivity of the tested materials and the carburization efficiency obtained in melting experiments. Therefore, the article also presents the course and results of studies on the process of cast iron melting in laboratory induction furnaces, where the carburizing material was introduced into the induction furnace with a fixed charge. Carburization efficiencies obtained for synthetic graphite ranged from 86.6% to 94.4%, and from 65.5% to 85.31% for petroleum coke. Based on the measurement results, a statistical analysis was carried out, yielding a relationship with a coefficient of determination R² = 0.92. The research confirmed the possibility of a quick assessment of carburizers in terms of their assimilation degree by molten metal. This is valuable information both for scientific research and industrial applications. The presented results form part of ongoing studies aimed at explaining the differences occurring within a given group of materials (petroleum cokes and synthetic graphites). Full article

In this research, a preconcentration procedure was developed for the sequential determination of chromium and vanadium using high-resolution continuum source graphite furnace atomic absorption spectrometry (HR-CS GFAAS). Due to low concentrations, chromium and vanadium were determined following preconcentration onto exfoliated graphite using ultrasound-assisted dispersive micro-solid-phase extraction (US DMSPE). The experimental parameters, including pH of the sample solution, the amount of exfoliated graphite, extraction time, elution conditions, as well as the main parameters of HR-CS GFAAS, were investigated. The calculated limits of detection for Cr and V were 0.003 µg g⁻¹ and 0.006 µg g⁻¹, respectively. The preconcentration factors obtained for Cr and V were 28 and 34, respectively. The RSD ranged from 0.3% to 3.4% for Cr and from 0.9% to 4.6% for V. The accuracy of this method was validated by analyses of INCT-MP4-2 (Mixed Polish Herbs) certified reference material. The measured chromium and vanadium contents were in satisfactory agreement with the certified values according to the t-test for a 95% confidence level. The proposed method was successfully applied for the determination of both elements in herbs such as hawthorn flower, hawthorn fruit, motherwort, white mulberry leaf, common milkweed, mistletoe, valerian root, and horse chestnut bark. Full article

The aim of this work was high-temperature synthesis of PtPdCoNiCu/C nanoparticles with high-entropy alloy (HEA) structure as catalysts for oxygen reduction reaction. The materials were synthesized using a highly dispersed PtPd/C support, which was impregnated with Cu, Ni, and Co precursors followed by their precipitation with an alkali. Subsequently, the material was subjected to thermal treatment in a tube furnace at 600 °C for 1 h in a stream of argon containing 5% hydrogen. In combination with HRTEM, element mapping and line scan, XRD, and XPS data, these results confirm the successful synthesis of five-component PtPdCoNiCu high-entropy alloy nanoparticles on the surface of the carbon support. The obtained materials are characterized by a high electrochemical surface area of up to 63 m²/g(PGM), as determined by hydrogen adsorption/desorption and CO-stripping, and a high specific oxygen reduction reaction (ORR) activity of approximately 269 A/g(PGM) at 0.9 V vs. RHE. The synthesized material demonstrated outstanding stability, as confirmed by an accelerated stress test of 10,000 cycles. After the test, the electrochemical surface area decreased by only 12%, while the catalytic activity for ORR even increased. The proposed synthetic strategy opens a new pathway for obtaining promising highly stable five-component HEA nanoparticles of various compositions for application in catalysts. Full article

The surface quality of hot-rolled steel products derived from recycled materials is critically impacted by oxide scale formation and adhesion, a behavior significantly influenced by residual silicon (Si) and the processing atmosphere. This study addresses a key research gap by thoroughly investigating the combined effect of water vapor content (10% to 30%) and residual Si content (across various slab types) on scale formation and adhesion, with a direct focus on process optimization to minimize surface defects. Crucially, this research introduces a novel quantitative assessment utilizing a macro-tensile test. This innovative method provides accurate mechanical scale adhesion energy data (measured in J/m²) directly applicable to hot-rolled recycled steel, a technique previously underexplored for this challenging material system. Results reveal that increasing water vapor concentrations significantly accelerate the formation of thicker and more defective oxide scales, thereby directly diminishing scale adhesion strength substantially across tested conditions. Conversely, steel with higher residual Si consistently maintained significantly higher scale adhesion energy than low-Si steel under similar steam conditions. Based on these quantitative findings, this study proposes a specific two-factor strategy for industrial application, strictly minimizing residual Si content while maintaining the furnace water vapor concentration at an intermediate level (approximately 20%). This strategy is shown to optimize scale formation conditions, facilitating efficient scale removal. Such results are crucial for optimizing hot-rolling parameters in recycled steel production, enabling enhanced surface quality and promoting sustainable manufacturing practices by providing a reliable quantitative metric (adhesion energy) for industrial quality control. Full article

The risk of environmental accumulation of aluminum ash and red mud is increasing, emphasizing the demand for high-value utilization. In this study, the conversion of aluminum ash and red mud into porous refractory materials with good thermal insulation performance is successfully demonstrated, demonstrating that both residues can be recovered as a resource and their environmental impact can be reduced in a sustainable manner. The phase composition and microstructure of the waste are evaluated by XRD and SEM/EDS, respectively, while their high-temperature behavior and performance were assessed through visual high-temperature furnace testing. The influence of the aluminum ash-red mud ratio on the rheological behavior of slurries containing surfactants at a constant alkaline pH was highlighted. A slurry composition of 40% red mud and 30% aluminum ash exhibited the lowest shear stress and viscosity values, required to facilitate bubble growth. Building on this formulation, foaming with 2% (mass fraction) H₂O₂ at 80 °C and sintering at 1250 °C produces a material with the optimum performance: a compressive strength of 1.03 MPa, a porosity of 58.55%, and thermal conductivity of 0.19 W/(m·K). The material exhibits long-lasting stability at temperatures ≤ 1100 °C. Thus, complementary compositions of aluminum ash and red mud show potential for practical application and value addition in the preparation of porous refractory materials with thermal insulation properties. Full article

Glass furnaces are a key component of the energy-intensive glass industry. Therefore, optimization of their energy performance is crucial for both economic and environmental sustainability. This study focused on optimizing the performance of an electric-boosted natural gas glass furnace. For this purpose, firstly, raw operational data were collected from a glass furnace. Next, reconciled data were obtained via a modelling process, data reconciliation, and gross error detection to establish a reliable dataset. Two linear regression models were developed and tested using both raw and reconciled data and compared with each other. The constrained optimization problem was constructed using a linear regression model and other process constraints and solved via the interior-point method to minimize specific energy consumption. The findings indicate that the reconciled data-based linear regression model yielded more reliable results. The specific energy consumption can be reduced to a minimum of 3660.088 kJ/kg-glass under an optimal setpoint for raw material, cullet, water, raw material temperature, electric boosting, and fuel. Furthermore, the analysis reveals that energy performance is enhanced with increased glass production and greater utilization of electric boosting. These results emphasize that the integrated statistical modelling approach provides valuable and actionable insights for energy performance improvements in the glass industry. Full article

Basic oxygen furnace slag (BOFS) is one of the major by-products of the steelmaking industry. Its limited utilization as a construction material is primarily attributed to its chemical properties, which hinder its stability and hydraulic activity due to its high free lime (f-CaO) content. This paper explores the performance of supplementary cementitious material (SCM) synthesized with ground granulated blast furnace slag (GGBFS), freshly produced BOFS (f-BOFS), and stockpiled BOFS (s-BOFS). A total of 10 mixtures with ordinary Portland cement (OPC) replacement percentages were assessed, maintaining a total replacement of 50% OPC, incorporating 15%, 25%, and 35% of each material by weight. The laboratory experimental program encompassed material characterization, fresh and hardened properties, pozzolanic activity, and durability assessment, with comparative studies conducted for each evaluation item. Test results indicate that f- or s-BOFS, when used with GGBFS, can be a viable alternative SCM with the potential for hydraulic activities and pozzolanic reaction. The newly synthesized SCMs demonstrated improved strength development in mortar mixtures. The mixture containing [15% f-BOFS + 35% GGBFS] achieved a 28-day compressive strength of 20.6 MPa, while the [25% BOFS + 25% GGBFS] blend reached a compressive strength of 19.7 MPa. These mixtures meet Grade 80 criteria as per ASTM C989/C989M Standard Specification for Slag Cement for Use in Concrete and Mortars. A performance-based ranking system was developed by integrating results from flowability, air content, strength activity index, drying shrinkage, alkali–silica reaction, and sulfate attack. The novelty of this work lies in assessing BOFS–GGBFS blends as SCMs using this multi-criteria approach to identify the most sustainable and technically viable mixtures. Moreover, the study highlights the influence of storage-induced weathering by directly comparing the reactivity and performance of f- and s-BOFSs in ternary blends, providing new insights into optimizing the utilization of slag. Notably, regardless of f- and s-BOFSs, proportions of [15% BOFS + 35% GGBFS] demonstrated superior strength development and achieved an excellent overall ranking. These findings confirm the potential of such slag blends as suitable SCMs for mortar and concrete applications, thereby advancing the sustainability and efficiency of cementitious materials. Full article