Determination of the Chemical, Physical and Mechanical Characteristics of Electric Arc Furnace Slags and Environmental Evaluation of the Process for Their Utilization as an Aggregate in Bituminous Mixtures

Revolutionizing Concrete: Performance Enhancement and Elemental Insights with Electric Arc Furnace (EAF) Slag Replacement

This study explores the influence of Electric Arc Furnace (EAF) slag particle size and replacement percentage on the engineering performance of concrete, providing valuable insights into its optimal utilization for sustainable construction. By analyzing particle size ranges-R1 (0.8-2.36 mm), R2 (2.36-4.75 mm), and R3 (4.75-7.0 mm)-this research highlights their distinct contributions to compressive strength and carbonation potential. Medium-sized particles (R2) emerged as the most suitable due to consistent compressive strength across different replacement percentages, high calcium content, and superior carbonation efficiency, leading to the highest calcium carbonate formation and CO2 uptake. The novelty of this work lies in integrating advanced analytical techniques, including Scanning Electron Microscopy (SEM) and Energy Dispersive X-ray Spectroscopy (EDX), to elucidate the microstructural mechanisms driving these performance enhancements. The findings establish a quantifiable relationship between EAF slag's high calcium and magnesium oxide content and its role in mechanical improvements and carbon dioxide sequestration via mineral carbonation reactions, with R2 achieving the highest CO2 uptake. This comprehensive approach addresses the apparent contradiction between early-stage and long-term performance, emphasizing R2's suitability, with 45% of the replacement of fine aggregate as the optimal choice for sustainable high-performance concrete with superior strength stability and carbonation efficiency.

Life Cycle Assessments of Circular Economy in the Built Environment—A Scoping Review

The Circular Economy (CE) is gaining traction throughout all industries and nations globally. However, despite several attempts, no one-off solutions for assessing the benefits and pitfalls of CE have been established, and neither have any measures with which to determine decisions. In line with this general observation, the Built Environment (BE) is no different. A tendency is observed in which, for the assessment of the environmental impacts of CE, a Life Cycle Assessment (LCA) has been deemed suitable. This paper presents a scoping review, using the PRISMA statement extension for scoping reviews, documenting how LCA has been applied for assessment of CE in the BE. The review covers a broad scope of literature, scoping the landscape, and delimits it into publications where CE strategy has been defined explicitly and described as a CE investigation. Among the LCAs applied, the dominant system boundary choice is the attributional approach. The authors open the discussion on whether this is actually suitable for answering the questions posed in the CE paradigm. From the review, and the discussion, the conclusion suggests that there is no dominant procedure in applying LCA of CE in the BE, even despite commonly developed LCA standards for the BE. Few studies also present the consideration to reconsider the applied LCA, as CE puts new questions (and thereby a potentially greater system boundary, as CE may imply greater societal consequences) that do not necessarily fit into the linear LCA framework currently applied in the BE.

Modeling of Non-Ferrous Metallurgy Waste Disposal with the Production of Iron Silicides and Zinc Distillation

This paper presents studies on the possibility of utilization of technogenic waste from the metallurgical industry by the method of complex processing in order to reduce the anthropogenic load on the environment of the region with the example of the zinc silicate-magnetite-carbon system. The selected sample of clinker dump from welting was subjected to chemical and scanning electron microscopic analyses and thermodynamic modeling. Thermodynamic studies were carried out in the temperature range 1600–2200 K and pressure p = 0.1 MPa, modeling the process of electric melting of clinker from welting in an arc furnace using the software application Astra 4 developed at the Bauman Moscow State Technical University (Moscow, Russian Federation). As a result of the thermodynamic modeling, the optimal temperature range was established, which was 1800–1900 K. Thermodynamic studies established that it is possible to drive away zinc from the system under study by 99–100% in the entire temperature range under study. The maximum degree of silicon extraction (α_Si) in the alloy is up to 69.44% at T = 1900 K, and the degree of iron extraction (α_Fe) in the alloy is up to 99.996%. In particular, it was determined and proved that clinker waste from welting can act as a secondary technogenic raw material when it is processed as a mono mixture to produce iron silicides with a silicon content of 18 to 28%.

Petrographic and Physical-Mechanical Investigation of Natural Aggregates for Concrete Mixtures

The availability of different lithology with which concrete can be packaged could create substantial questions on the differences that they can provide to the same mixture. Different kinds of aggregates were analyzed individually to investigate their main characteristics, which allowed us to package five types of concrete mixtures. These five mixtures were compared to each other through compressive strength values. Furthermore, it was considered microscopically what possible differences could exist between these different mixtures, for example, differences in the cement/aggregate reaction. The chemical characterization of the aggregates, used as the skeleton of the cement mixes, was proposed as an important investigative phase in order to better understand the differences in the geotechnical and physical-mechanical characteristics and to verify the presence of any harmful phases for the durability of the concrete.

Preliminary Validation of Steel Slag-Aggregate Concrete for Rigid Pavements: A Full-Scale Study

The high wear resistance and toughness of electric arc furnace slag (EAFS) means that this industrial by-product can successfully replace natural aggregate in hydraulic or bituminous concretes that withstand vehicle traffic. This article validates the use of concrete made with large amounts of EAFS for rigid pavements. Accordingly, three EAFS–concrete mixes made with metallic or synthetic fibers were designed. Their performance was studied through laboratory tests (compressive strength, modulus of elasticity, splitting tensile strength, and abrasion resistance) and field observations on full-scale slabs made with each of the studied mixes. All mechanical properties yielded adequate results for concrete for rigid pavements. The metallic fibers increased the strength and elastic stiffness by 7–10%, while the addition of synthetic fibers slowed the development of these properties over time. On the other hand, all the mixes allowed for a successful implementation of full-scale slabs, with none of them showing excessive deterioration after five years of exposure to the outdoor environment. Only minor cracking and some chips in the surface-treatment layer were detected. The strength development of the slabs and their slipperiness were adequate for use in high-speed pavements. The overall analysis of the results shows that concrete made with EAFS can be used in real rigid pavements.