Physico-Chemical Characterization of the Electric Arc Furnace Slag (EAFS) of the Sonasid-Jorf Steelworks - Morocco

The steelmaking process results in the by-product formation of electric arc furnace slag (EAFS). Slag is recovered at two different stages of the steelmaking process, the first recovery is black and the second is white. The present research focuses on the composition differences between the two types of slag from SONASID-Jorf steel in Morocco. A granular separation of the black and white slag was carried out to monitor the chemical and mineralogical composition. XRD and Fourier Transform Infrared Spectroscopy are performed on the samples in this paper. The slags suggest good hydraulic binder properties. It would be useful for research in the field of building materials to correlate the results of the characterization of EAFS with other types of slag with the aim of improving the potential for partial replacement of cement in the matrix. The slag can also be used as binders in mixtures of bio-based building materials. The electric arc furnace slag (EAFS), exhibiting appropriate cementitious activity, can be utilized as mineral admixture in cement and concrete. Black and white slags are studied in this paper in order to determine their characteristics according to their granularity.

Characterization of a Chromium-Bearing Carbon Steel Electric Arc Furnace Slag after Magnetic Separation to Determine the Potential for Iron and Chromium Recovery

This study investigates the potential to recover iron and chromium from a chromium-bearing carbon steel Electric Arc Furnace (EAF) slag. This slag contains indeed about 30 wt.% Fe and 2.5 wt.% Cr. However, the minerals are intergrown at small scale (<100 µm) and iron and chromium are mostly contained in spinel phases which makes the separation challenging. Several methods including Mössbauer spectroscopy, X-ray Diffraction, Scanning Electron Microscopy (SEM) and electron microprobe analysis were used in order to fully characterize the products obtained after a low-intensity magnetic separation of this carbon steel EAF slag, with the objective to define a pre-treatment process allowing the recovery of iron-rich particles and of a chromium-upgraded fraction. The results show that even if the magnetic separation seems to be not efficient in a first approach for producing an iron-rich/chromium-poor fraction, this fraction can be obtained by adding an attrition step which means that some separation mechanisms still occurred during the magnetic separation. However, it was not possible to produce a chromium-rich fraction. The main bottleneck for reaching a good separation is most probably the very fine liberation size of the iron and chromium bearing minerals.

The Immobilisation of Heavy Metals from Sewage Sludge Ash in CO2-Cured Mortars

Sewage treatment processes are a serious environmental threat due to the difficulties involved in its waste management and disposal. Therefore, one developing trend in sewage sludge processing is its thermal treatment, which generates sewage sludge ash that may contain many environmental pollutants, such as heavy metals. Moreover, due to the European Union requirements that not only focus on the waste generation reduction but also on its reuse and final disposal, it is essential to pursue new applications of such resources, such as the waste-based material incorporation into alternative cementitious materials. Thus, this study evaluated the heavy metals leachability of CO2-cured mortars incorporating sewage sludge ash as filler. For this purpose, Portland cement, reactive magnesia, and electric arc furnace slag were used to produce three different CO2-cured mortars, which were cured though pressurised accelerated carbonation curing for 24h. These mortars presented up to 12.7 MPa as compressive strength and their carbonation was confirmed by TG-DTG and FT-IR analyses. Their leachability of heavy metals met the European requirements for all waste materials, including inert materials, and post-industrial wastewater. Therefore, the immobilisation of heavy metals in this binding technology may be considered an effective method to safely manage sewage sludge ash.

Mechanical Properties of Coarse Aggregate Electric Arc Furnace Slag in Cement Concrete

The feasibility of using EAF slag aggregate, fly ash, and silica fume in pavement Electric Arc Furnace Slag Concrete (CEAFS) is the focus of this research. EAF slag aggregate is volume stable and suitable for use in concrete, according to the findings of the testing. EAF slag was utilized to replace natural coarse aggregates in the CEAFS mixes. CEAFS was created by blending 50% crushed stone with 50% EAF slag in coarse aggregates, with fly ash (FA) and silica fume (SF) partially replacing cement at content levels (i.e. FA: 0, 20, 30, and 40%; SF: 0, 5, and 10%). The soil compaction approach was used to evaluate the optimal moisture level for CEAFS mixes containing EAF slag aggregate fly ash and silica fume. A testing program was used to investigate the weight of CEAFS units and their mechanical qualities (compressive strength, flexural strength, and elastic modulus). As a result, the fresh and hardened unit weights in the CEAFS are comparable. Moreover, variations in the concentration of mineral additives FA and SF in adhesives, as well as the CEAFS mixed aggregate ratio, have an impact on compressive strength, flexural strength, and elastic modulus at all ages. However, combining EAF slag aggregate with (FA0% +SF10%; FA10% +SF0%; FA10% +SF10%; and FA20% +SF10%) the CEAFS mixtures have improved mechanical characteristics over time. According to this study, CEAFS pavements can be made with EAF slag aggregate fly ash and silica fume. In addition, a formula correlation was suggested to compute CEAFS (i.e. compressive strength with elastic modulus and compressive strength with flexural strength). Doi: 10.28991/cej-2021-03091755 Full Text: PDF