## 1 Introduction  
Metallurgical industry is one of the world's largest contributors to the anthropogenic CO2 emissions. Until the last years of 19 th century, most of the produced steel derived from the integrated process (blast furnace, BF/basic oxygen furnace, BOF route) used coal as the reducing agent and iron as raw material [1]. Nowadays, in order to reduce energy consumption and bring CO2 emissions close to zero, a secondary production route using an electric arc furnace (EAF) is becoming far more widespread. According to previous researches, by 2060, the share of secondary steel production will exceed the share of the primary one. In the secondary steelmaking process electricity is used to melt iron scraps with chemical additives into steel. Even if the secondary production route requires 56% less energy than the primary one (Institute of Scrap Recycling Industries 2012), a large amount of solid waste materials are produced [2]. As estimated in Steel Industry By-Products Project group report 2007-2009 by World Steel, the average production of 1 ton of steel results in about 200 kg (EAF) to 800 kg (BF/BOF) of solid wastes globally [3]; other studies show that the amount of wastes is 100-180 kg and 200-400 kg for each ton of liquid steel for EAF and BF respectively [4]. In the light of the above, the management of this kind of wastes is becoming a crucial issue especially for the countries with the largest annual production such as India (29 million tons [5]), China (90 million tons [6]), Europe (21 million tons [7]). Therefore, reusing, recycling, and recovering steel wastes in many other industrial applications is extremely important. They are found to be useful in many fields, such as constructions, asphalt concrete, agricultural fertilizer, and for soil improvement. However, better utilization for value-added purposes can be achieved [8, 9]. Among industrial wastes, the EAF slags have good physical, chemical, and mechanical characteristics and their use in the construction industry is increased in the last years. Analyzing their intrinsic properties such as granules size, specific weight, or porosity, EAF slags can be considered similar to stone aggregates commonly used in construction engineering [10; 11]. This is due to the high iron content, which gives to the EAF slags a hard and wear-resistant constitution. The chemical composition of EAF slags is shown in Table 1[6]. Although this composition is slightly different in relation to the kind of scraps and additives used, the high levels of FeO and CaO determine the need to carry out special treatments on the raw slags before their use as aggregate. In fact, when free CaO comes in contact with water, it hydrolyzes (CaO + H\({}_{2}\)O \(\rightarrow\) Ca(OH)\({}_{2}\)), and its volume duplicates; Ca(OH)\({}_{2}\) is a cementitious material resulting in the fine particles cemented on the slag surface, thus compromising the formation of an embedded concrete structure [10; 12]. Previous researches [13; 14] show that a proper stabilization treatment of EAF slags by exposing them to outdoor weather and regular spraying for at least 90 days may avoid any expansive phenomenon, allowing a safe use of such slag as aggregate in concrete production. Furthermore, the fine powder covered on the slag surface after crushing needs to be removed in order to have edged shaped granules. Steelmaking slags also contain a high amount of iron oxide (FeO) that may lead to corrosion. Therefore, these wastes need an \"iron-removal\" process by means of a permanent magnetic separator [12; 15] for their adequate use in other engineering applications. After the abovementioned and other specific treatments, EAF slags have generally excellent stone-like mechanical properties.