## 1 Introduction  
Electric arc furnace dust (EAFD) is generated from the electric arc furnace production of steel in amounts of approximately 1-2% (by weight) of the steel produced. More than 30% of steel production now uses electric arc furnaces [1] and approximately 6 million metric tons of EAFD are generated on an annual basis worldwide, and of that amount, only an estimated 2.5 million metric tons are recycled, mainly in the United States, Europe, Taiwan and Japan [2, 3]. EAFD is identified as a hazardous waste in the European Waste List and by the US-EPA, as it contains high quantities of Cd, Cr, Pb, and Zn [4, 5, 6, 7, 8, 9]. The \"Best Available Techniques (BAT) Reference Document for Iron and Steel Production\" [10] includes as EAFD recycling option the pyrometallurgical or hydrometallurgical processes or hybrid of both (Waelz Process). These processes aim, on the one hand, to extract non-ferrous metals such as zinc and lead that can be incorporated into other processes, and on the other allow the recycling of the matrix in the steel industry and thus avoid its disposal in landfills. However, despite the high iron content, for waste with less than 15% of Zn, the most used management continues to be the landfill of hazardous waste after solidification/stabilization treatment. In the EU two-thirds of EAFD generated are deposed in landfills [11, 12]. The recent recovery processes of EAFD include stabilization within materials with potential uses in the construction sector. Due to its ability to assimilate alternative materialsof different nature (without significant changes in the production process) and without negative effects on the properties of the final product. This way of management is the most favorable because of its low cost and environmental benefit of reducing waste, minimizing the impact on the environment by avoiding disposal in landfills, and reducing the amount of natural resources that the activity needs. The stabilization of EAFD is carried out, by vitrification, obtaining a vitreous material [13], or by cementation, with hydraulic binders, a cement matrix [6; 14; 15], and recently by alkaline activation of different aluminosilicates [16; 17], resulting in low-cost and environmentally friendly materials. The manufacturing process of these new cementitious materials, generate less polluting gas emissions and significant energy savings. Among these alternative materials, ceramic geopolymers are a subgroup, where fly ash, with a low calcium content, and calcined clays are the most common precursors used in the synthesis of geopolymers [18]. Ceramic geopolymers can be carried out in two temperature ranges, geopolymers at low temperatures, ranging from room temperature to 450 \({}^{\circ}\)C and those at high temperatures ranging up to 1200 \({}^{\circ}\)C. The geopolymers obtained with setting temperatures between 65 \({}^{\circ}\)C and 450 \({}^{\circ}\)C, are equivalent to conventional ceramic bricks, stable to water and with medium mechanical resistance [19; 20; 21]. Geopolymers that use industrial waste or by-products have the potential to introduce pollutants into the environment. Laboratory leaching tests are applied by different authors to evaluate the degree of immobilization of hazardous materials, as well as to estimate the elimination of toxic trace elements during the beneficial reuse of secondary materials on the ground [22; 23]. In this way, leaching tests are basically carried out for the purpose of providing information on material/water contact conditions and their influence on potential release of pollutants to the water of the soil, being an essential stage in the absorption by plants and also in the elimination to water resources. The most used tests are the toxicity characteristic leaching procedure (TCLP, 1992), and the equilibrium batch leaching test (UNE-EN 12457, 2002).