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Open AccessArticle

The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C)

Dipartimento di Meccanica, Politecnico di Milano, Via La Masa 1, 20156 Milano, Italy
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Minerals 2019, 9(11), 706; https://doi.org/10.3390/min9110706
Received: 15 October 2019 / Revised: 7 November 2019 / Accepted: 12 November 2019 / Published: 14 November 2019
(This article belongs to the Special Issue Metallurgical Slags)
Studies conducted over the past 10 years have demonstrated the technical suitability of the electric arc furnace slag as an alternative to natural stone in several applications. Steel slag can be profitably used as a road surface layer, for foundations and embankments, or for concrete aggregates. However, a strong limitation to their use is due to the presence of toxic metals (Ba, Cr, V, Mo, etc.) that can be released into the environment in particular conditions, especially for unbound products in which the slag can come into contact with water. Recent studies have investigated the role of chemical composition and microstructure of slag on toxic metal leaching, allowing for the design of suitable stabilization treatments for hindering such leaching. In this work, four batches of electric arc furnace carbon steel slag underwent a stabilization treatment and the obtained results were compared. In two batches, the stabilizer was added directly in the slag pot and the slag was cooled down in the same pot. The other two batches were stabilized during the downfall from slag door to slag pit. Several slag samples were collected before and after the stabilization treatment and were characterized by means of ED-XRF, XRD, and SEM analysis. Leaching tests were carried out in agreement with EN 12457-2 standard on 4 mm granulated slag, and the leachate concentration was compared with the current Italian limits listed in D.M. 3 August 2005 N. 201 and D.M. 5 April 2006 N. 186. The results clearly indicated that the cooling in the slag pot improved the efficiency of the stabilization treatment, leading to a complete transformation of the microstructure by a full development of homogeneous gehlenite matrix and a coarsening of Cr-spinels, assuring better toxic metal retention behavior. On the contrary, stabilization in the slag-pit was rapid and reduced the interaction between slag and stabilizer, leading only to partial transformation of larnite into gehlenite, and also reducing the coarsening of Cr-spinel. In addition, a layering effect was observed, resulting in an inhomogeneous product from top to bottom in terms of chemical composition, microstructure, and leaching behavior. View Full-Text
Keywords: EAF carbon steel slag; stabilization treatment; leaching; gehlenite; Cr-spinel; calcium silicate; recycling EAF carbon steel slag; stabilization treatment; leaching; gehlenite; Cr-spinel; calcium silicate; recycling
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MDPI and ACS Style

Mombelli, D.; Gruttadauria, A.; Barella, S.; Mapelli, C. The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C). Minerals 2019, 9, 706. https://doi.org/10.3390/min9110706

AMA Style

Mombelli D, Gruttadauria A, Barella S, Mapelli C. The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C). Minerals. 2019; 9(11):706. https://doi.org/10.3390/min9110706

Chicago/Turabian Style

Mombelli, Davide; Gruttadauria, Andrea; Barella, Silvia; Mapelli, Carlo. 2019. "The Influence of Slag Tapping Method on the Efficiency of Stabilization Treatment of Electric Arc Furnace Carbon Steel Slag (EAF-C)" Minerals 9, no. 11: 706. https://doi.org/10.3390/min9110706

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