This study examines the sustainable production of strontium hexaferrite by recycling mill scale, a by-product of steel manufacturing, as a source of iron. Strontium, designated as a critical raw material by the European Union, is essential for high-demand magnetic applications. In this study, various additives, including Al2O3, Cr2O3, Co3O4, and La2O3, were incorporated during the synthesis process to enhance the magnetic properties of the resulting strontium hexaferrite. Additives were included in the structure using the mechanochemical method. The results show that the incorporation of these additives has a significant influence on the coercivity, remanence, and overall magnetic anisotropy of SrFe12O19.

Hydrogen-based direct reduction of steel by-product mill scale

Dielectric properties of secondary mill scale: Advancing nondestructive terahertz hot-rolled steel surface characterization

Civil construction is considered one of the industries with the most significant environmental impact. In this sense, the main goal of this study was to investigate three different mortar sets incorporating industrial lamination waste, assessing their chemical, physical, and microstructural properties, as well as their mechanical performance to develop sustainable mortars. Cylindrical and prismatic specimens were produced using various incorporation methods: reference mortar, mortars with mill scale addition, partial replacement of cement with mill scale residue, and partial replacement of sand with residue, at proportions of 10%, 20%, 30%, 40%, and 50%. In addition, X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) analyses were performed. Physical and mechanical tests included those for bulk density, consistency index, water absorption by capillarity, axial compressive strength, and flexural tensile strength. XRF analyses showed an increase in iron oxide content and a decrease in calcium oxide with the addition of mill scale. XRD analyses confirmed the presence of compounds such as alite and portlandite, which are common in cementitious mortars. FTIR spectra confirmed the presence of functional groups through absorption bands associated with Si–O stretching. SEM images showed slight morphological changes in the composites as the amount of industrial lamination waste increased. The addition of industrial lamination waste affected the spread index and density of the mixtures, while water absorption by capillarity decreased in some formulations with mill scale. Concerning mechanical performance, the strength of the mortars varied with increasing amounts of industrial lamination waste.

Sustainable recycling of alloy steel mill scale via tailored slag refining: A low-carbon route for in-process resource recovery.

On the use of industrial steel mill scale as a high-density energy carrier: Part I. Reaction processes and particle size evolution over cycling

On the use of industrial steel mill scale as a high-density energy carrier: Part II. Microstructural and chemical evolution over cycling

New alternatives in the construction industry are essential for economic, sustainable, and environmental progress. In this context, this work investigated three sets of sustainable mortars incorporating industrial lamination waste, assessing their chemical, physical, microstructural, and mechanical properties to inform their development. Cylindrical and prismatic specimens were produced using the following incorporation methods: a reference mortar, mortars with mill scale addition, partial cement replacement with mill scale, and partial sand replacement with mill scale, at proportions of 10%, 20%, 30%, 40%, and 50%. Additionally, analyses including X-ray fluorescence (XRF), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy-dispersive spectroscopy (SEM/EDS) were performed. Physical and mechanical tests, including bulk density, consistency index, capillary water absorption, axial compressive strength, and flexural tensile strength, were also conducted. XRF results indicated an increase in iron oxide content and a decrease in calcium oxide with the addition of mill scale. XRD confirmed the presence of compounds, such as alite and portlandite, which are common in cementitious mortars. FTIR spectra exhibited characteristic functional groups through absorption bands related to Si–O stretching. SEM micrographs revealed slight morphological changes in the composites as the quantity of industrial lamination waste increased, and EDS data supported the XRF findings. The addition of industrial lamination waste affected the spread index and density of the mixtures, while capillary water absorption decreased in some formulations with mill scale. The strength of the mortars increased with the incorporation of industrial lamination waste. In conclusion, using industrial lamination waste in mortars is a technically and environmentally feasible alternative that aligns with the principles of sustainable development and the circular economy in the construction industry.

The reuse of industrial residues has gained importance due to environmental and public health concerns associated with improper waste disposal. Steel scale (CDA), a by-product of machining and rolling operations, represents a residue with technological potential for incorporation into polymer composites. This study developed a low-cost and sustainable material by reinforcing an orthophthalic polyester matrix with CDA and systematically evaluated its mechanical, thermal, and structural properties. Four formulations were prepared based on the maximum feasible filler loading: R (pure resin), C1 (50% CDA), C2 (100% CDA), and C3 (150% CDA). Composites were manufactured by cold-press molding under a two-ton compressive load. Characterization included tensile, flexural, and impact testing, thermogravimetric analysis (TGA), thermal conductivity, apparent density, liquid absorption, and morphological assessment by scanning electron microscopy (SEM). CDA incorporation reduced tensile and flexural strength but increased elastic modulus, impact toughness, and thermal conductivity. The C3 composite exhibited the highest thermal stability, retaining more than 50% of its initial mass at 500 °C. Density and liquid absorption increased proportionally with filler loading, and SEM revealed heterogeneous microstructures with particle agglomeration, sedimentation, and interfacial gaps, explaining the mechanical and thermal trends. The findings demonstrate the feasibility of producing dense and low-cost polyester composites reinforced with steel scale. The structure–property relationships identified in this study establish a foundation for subsequent investigations focusing on additional functional behaviors of this waste-derived material system.

The steel industry generates large quantities of waste, including mill scale and hot-rolled steel sludge. These by-products pose serious environmental and economic challenges. This study proposes a sustainable strategy to convert them into LaFeO3±δ-based perovskite materials for gas sensing applications. Iron oxide precursors were recovered, purified, and processed via mechanochemical milling followed by calcination at 1200 °C to produce LaFeO3±δ powders. Among all synthesized materials, the hot-rolled steel waste-derived material (LFO-HRSW) exhibited the best performance. SEM analysis revealed the smallest grain size (0.31 µm) and pore diameter (0.36 µm), which enhanced surface area and gas interaction. When exposed to combustion gases at 200 °C, its electrical resistivity increased from 19.56 Ω·m in air to 32.02 Ω·m, yielding a high sensor signal of 1.64. LFO-HRSW also responded the fastest, stabilizing within 2 min of gas exposure. These results highlight its superior sensitivity and real-time detection capability. This work is the first to directly transform mill scale and hot-rolled steel wastes into LaFeO3±δ perovskites for gas sensing applications. It offers a low-cost route to high-performance sensors, supports a circular economy approach for steel waste utilization, and provides potential benefits for environmental monitoring and industrial emission control.

Primary mill scale generated during steelmaking and hot deformation processes contains substantial iron oxides and can be directly recycled by converting it into self-reducing briquettes for induction furnaces. In this work, the roles of calcined petroleum coke as the reductant and molasses as the binder were examined to identify a balanced formulation offering both good reduction behaviour and adequate mechanical strength. Stoichiometric calculations suggested that 10−12 wt.% CPC is required to fully reduce Fe 2 O 3 present in mill scale. Thermogravimetric analysis on briquettes with 6−14 wt.% CPC showed that the 12 wt.% briquette exhibited the highest mass-loss in the 600−900°C window, indicating the most active reduction stage. After reduction, SEM-EDS revealed iron-rich phases, and a metallic iron content of 96.8% was confirmed by wet analysis. Briquettes containing 10–12 wt.% CPC and 4–5 wt.% molasses provided mechanical strength of 48 N and a bulk density of 4.6 g/cm 3 , allowing stable charging into the melt.

Study of limestone and mill scale as fluxing agents for the recovery of tin from slag concentrates

Colloidal stability and cadmium removal efficiency of chitosan-modified magnetite nanoparticles from mill scale waste.

This study explores the hydrogen reduction of industrial mill scale as a method for obtaining iron powder suitable for powder metallurgy applications. Mill scale, a by-product of hot rolling, was subjected to reduction in a hydrogen atmosphere at 800 °C, 900 °C and 1000 °C for 60 minutes under isothermal conditions. The chemical composition of the obtained products was analyzed using scanning electron microscopy (SEM) and energy-dispersive Xray spectroscopy (EDX). The results demonstrate that reduction at 800 °C produces sponge iron with approximately 95 wt.% Fe, accompanied by residual oxygen and calcium. At 900 °C, variations in impurity distribution were observed, reflecting the heterogeneous structure of the raw scale. The highest degree of reduction occurred at 1000 °C, where the iron content exceeded 98 wt.% and no harmful impurities such as sulfur or phosphorus were detected, although localized oxide inclusions remained. The findings confirm the feasibility of recycling mill scale through hydrogen reduction, providing both ecological benefits and economic advantages by converting metallurgical waste into valuable feedstock for powder metallurgy.

The development of low-carbon construction materials is essential to meeting global climate targets. This study presents a carbon-negative binder synthesized primarily from iron-rich industrial byproducts (mill scale), supplemented with fly ash, metakaolin, and limestone. Oxalic acid enhances iron dissolution and promotes stable carbonate formation during CO2 curing. Strength development occurs through direct CO2 mineralization, with carbonation curing conducted at 0, 1.5, and 3 bar using both normal and saline water. Specimens cured at 3 bar with saline water achieved compressive strengths exceeding 60 MPa and carbon sequestration rates up to 1.03% per day. Carbonation depth followed a square-root time relationship, with enhanced propagation under high-pressure saline conditions. Microstructural analyses (XRD, TGA–DTG, FTIR, FESEM) confirmed the formation of siderite, lepidocrocite, nesquehonite, and calcite within a dense matrix. Life Cycle Assessment indicated approximately 85% lower fossil-based global warming potential and over 80% reductions in water consumption compared to Ordinary Portland Cement, demonstrating a potable-water-free, resource-efficient binder suitable for circular and climate-resilient infrastructure.

Novel heavyweight geopolymer concrete with mill scale and barite aggregates for sustainable radiation shielding applications

Utilization of steelmaking by-products in the construction industry: A comprehensive review of steel slag and steel mill scale

Pulverized steel mill scale waste for green concrete production

This study evaluated the potential of steel mill scale (SMS), a steel industry byproduct primarily composed of iron oxides, as a partial replacement for fine aggregates in self-compacting concrete (SCC). SMS was incorporated at replacement levels ranging from 10 % to 40 % by weight of fine aggregate. Experimental investigations have assessed rheological, mechanical, and durability properties in accordance with the EFNARC and IS codes. Rheological results confirmed that all the mixtures met the workability criteria, with slump flows ranging from 685 mm (SMS20) to 694 mm (SMS40). SMS25 presented the shortest T50 time of 5.2 s, indicating improved flowability. The mechanical performance peaked at 15 % SMS (SMS15), yielding the highest 28-day compressive strength of 45.45 MPa, split tensile strength of 3.80 MPa, and flexural strength of 4.72 MPa. Durability assessments revealed that SMS40 had the lowest mass loss (0.9 %) under acid attack and the deepest carbonation depth of 8.0 mm at 28 days. Elevated temperature tests revealed that the SMS mixtures retained up to 85 % of the compressive strength at 500°C due to hydrothermal interactions. Microstructural analysis (SEM) revealed denser matrix development at optimal replacement levels. Machine learning models such as decision trees, random forests, and multilayer perceptrons have been applied to predict compressive strength. The random forest regressor performed best, achieving an R² of 0.98, an RMSE of 1964.47, and an MAE of 1125.55. Most existing studies focus on mechanical properties or use SMS in conventional concrete. Integrated assessments covering durability and microstructure in SCC, especially with predictive modeling, are limited. This study bridges that gap through experimental testing and advanced machine learning integration. • Steel mill scale (SMS) is an eco-friendly, effective partial replacement for fine aggregate in self-compacting concrete (SCC). • SCC with 15 % SMS achieved the highest 28-day compressive strength (45.45 MPa) and superior tensile/flexural strength. • All SCC mixes met EFNARC standards, with 25 % SMS showing the best flowability (T50 = 5.2 s). • SCC with 40 % SMS showed the best acid resistance (0.9 % mass loss) and retained 85 % strength at 500°C. • Random Forest model predicted compressive strength with R² = 0.98, and SHAP identified key predictive features.

This study focuses on the recycling of mill scale of AISI 4330 V grade using induction furnace melting. The prime objective of the work is to establish a viable pathway for efficient recovery of iron, nickel and molybdenum from briquettes made of mill scale using carbothermic reduction utilising Calcined Petroleum Coke (CPC) as a reducing agent. Briquettes were prepared by grinding mill scale into powder and mixing it with CPC and molasses as a binder. Chemical composition analysis, X-ray diffraction (XRD), and thermogravimetric analysis (TGA) were conducted to assess the effectiveness of the recovery of metals from mill scale. Both stoichiometric calculations and TGA analysis signified that, briquettes with 10% to 12% carbon can give best reduction results. Subsequently, induction furnace experiments were conducted, varying the proportion of charge constituents for making melt pool. Results indicated that using mild steel (MS) plates for making melt pool improved recovery rates compared to using pig iron. A respective recovery of 99.36%, 75.52% and 97.01% was achieved for iron, nickel and molybdenum. A rise of 24.44%, 14.45% and 47.47% was observed in recovery of iron, nickel and molybdenum, respectively, in route using MS plate for making melt pool in comparison with route using PI for making melt pool. XRD study of slag produced in various routes was conducted to assess the presence of phases which indicates loss of elements into the slag. Substantial recovery of iron, nickel and molybdenum was observed in the final ingot contributing towards circular economy. Furthermore, energy requirements for the recycling process were calculated and it was observed that significant portion of energy (78.55%) was consumed in the reduction process.