## 1 Introduction  
Through applying alternative use cycles, the circular economy (CE) aims at reducing dependency on (new) natural resource extraction, while expanding the time that resources spent within the technology sphere [1]. In essence, this approach of CE imitates Earth's naturally circular systems [1]. CE envisions a balance between industry and the environment, ensuring that human civilization will continue to thrive in the long run. All waste is designed to become reusable material through different processes. Following the example of the ecosystems, material cycles in CE are closed [1]. Many researchers have studied the different aspects raised by the two main pillars of CE, namely, the technical model [2; 3; 4; 5; 6; 7] and the biological model [8; 9; 10]. [PERSON] et al. [2], [PERSON] et al. [3], [PERSON] et al. [4], [PERSON] et al. [5], [PERSON] et al. [6], and [PERSON] et al. [7] dealt with refractory characterization and recycling. [PERSON] et al. [8] and [PERSON] et al. [9] concluded on issues related to the stabilization and potential reuse of sewage sludge and municipal waste incineration ashes. Moreover, [PERSON] et al. [10] suggested a framework supporting the decision making for biodegradable waste management. On the other hand, [PERSON] et al. [11] concluded that there are still many issues leading to the negative environmental impacts that arise from the fundamental assumptions of CE. Environmental characterization is crucial throughout all stages of refractory material life as it assists in evaluating, mitigating, and controlling risks. Refractory solid materials are used in industries (steel, cement, aluminum, glass, ceramics, etc.) where there are requirements to withstand very high temperatures. Refractory materials are produced from abundant industrial minerals, including chromite, dolomite, SiO\({}_{2}\), MgO, and Al\({}_{2}\)O\({}_{3}\)[2]. Refractories are the primary materials applied as the internal lining of kilns, incinators, and furnaces. Because these materials are exposed to elevated temperatures and corrosive liquids or gases, they have to meet different challenging specifications, such as thermal expansion, mechanical strength, and corrosion resistance [2]. Refractories are produced in shape form (bricks) for lining subsystems of the industry or in powder form, which is shaped on the installation site. Refractories are classified into acidic, basic, or neutral according to the interaction of water with the primary raw material. Acid refractories, including silica, zircon, and alumina silicates are typically applied for lower operating temperatures [3]. Basic refractories, such as doloma, spinel, and magnesia, are usually combined with graphite and carbon and applied in highly basic environments [3]. Neutral refractories, including alumina and chromia refractories, are applied broadly by the metal industries because of their moderate price, elevated melting temperature, and ability to be applied in basic and acidic environments [3; 4]. The industries (metal, cement, glass, etc.) from time to time (depending on the type of production) replace the refractories into the frame of maintenance of the industrial units. It is estimated that, worldwide, 35-40 million tons of refractories are produced and used yearly, and an amount of about 28 million tons of spent refractories are produced [3]. Even in this vast amount of spent refractory material, it is worth mentioning that, in the last 20 years, the recycling processes have not seen a massive utilization since (a) the production cost of the raw material was low, and (b) the cost of disposal of the used refractories was not high. Many of the abovementioned elements were changed recently, while many environmental issues were raised concerning the handling of the refractory wastes and the increased cost of landfilling.