The electric arc furnace (EAF) steelmaking route has grown in recent decades, owing to its advantages of treating scraps and direct reduced iron (DRI). The EAF technology and more specifically, the one based on recycling of scraps, largely contributes to reducing the environmental footprint of the steel industry, the preservation of natural resources, and sustainable production. With 0.25-1.15 tons of CO2 emitted per produced ton of liquid steel (tCO2/tLS), the EAF can be considered superior to the alternative blast furnace-basic oxygen furnace (BF-BOF) route with 1.6-2.2 tCO2/tLS [1, 2]. However, EAF steelmaking faces other industrial challenges which yet remain to be improved/resolved, such as the refractory pre-mature failure and the associated costs which bear on the process through operation downtime, replacement costs for new refractory bricks, and manhour requirements. Moreover, prolonging the refractory lifetime can largely contribute to waste minimization. The MgO-C refractory bricks have been widely used as the lining for the EAF because of their superior properties such as high thermal conductivity, low thermal expansion, high temperature mechanical strength, thermal shock resistance, and chemical corrosion resistance. However, the refractory bricks, functioning under extreme operational conditions, may undergo various microstructural changes (e.g., the graphite oxidation, gas phase evolution, formation of phases in the liquid state, and solidstate phase transformations), adversely affecting the thermomechanical properties, and therefore, shortening the refractory lifetime. For instance, the exposure to high thermal radiation from electrodes and the oxidizing atmosphere is detrimental to the service life of the MgO-C bricks [3]. A vast number of lab-scale studies have been conducted in the past few years with the objective to improving the properties of MgO-C refractories. The micro- or nano-carbon/graphite-Si/SiC composites were introduced to the refractory structure to enhance its oxidation resistance [4, 5], or calcium-magnesium-aluminate aggregates were added to improve thermal shock resistance [6]. Cheng et al. [7] studied the effect of carbon content on the mechanical properties of MgO-C refractories. They reported that, although carbon decreased the cold modulus rupture of refractory, it improved the fracture displacement, due to the good sliding ability of the graphite flakes. Liu et al. [8] investigated the effect of carbon content (3-16 wt%) on the oxidation resistance and oxidation kinetics of MgO-C refractories. They revealed that the bulk density, apparent porosity, and cold crushing strength decreased with increasing the carbon content. Xiao et al. [9] also investigated the oxidation behavior of the MgO-C refractories with respect to different Si/SiC contents. The results showed that the deoxidation efficiency of Si is better than that of SiC, and finer grain size and higher surface area of deoxidizers increased the deoxidation efficiency. In addition, the oxidation rate of the refractory at temperatures ranging from 1100℃ to 1300℃ was mostly dependent on the permeation path of O2 and contact with C governed by the pore size and distribution in the refractories. In addition to the small-scale experiments, post-mortem analysis of the MgO-C bricks is essential to better understand the deterioration mechanisms of refractory from both design and operation perspectives, and identify parameters affecting its premature failure in the real context. Calvo et al. [10] studied the degradation mechanism of Al2O3-MgO-C (AMC) refractories used in secondary metallurgical ladle furnaces (LF). They reported that an increase in open-pore volume and size, resulting from volatile elimination of the phenolic resin during the first preheating before receiving the molten metal, could be the main cause of refractory degradation. The degradation process would result in increased contact surface between the refractory and liquid steel and molten slag during operation, thereby, accelerating the brick chemical corrosion and erosion by the liquid media. Another similar post-mortem study was carried out by Tabatabaei-Hedeshi et al. [11] on AMC refractories with three different compositions, used in the LF slag line. The results indicated that the corrosion resistance of the samples containing a stoichiometric spinel (MgAl2O4) was superior to the ones containing an Al-rich spinel. However, to the best of the authors’ knowledge, so far, there is no study reported on the post-mortem bricks from the thermal radiation zone of the EAF. Therefore, the present study aims to investigate the degradation mechanisms of the refractory used in the upper zone of the EAF above the slag line, exposed to thermal radiation, over its service life cycle. The current work will be leveraged to possibly improve the operational parameters and refractory design to prolong the refractory performance in service.