Geopolymerization of coal fly ash in the presence of electric arc furnace dust

Coal Fly Ash–Clay Based Geopolymer-Incorporating Electric Arc Furnace Dust (EAFD): Leaching Behavior and Geochemical Modeling

“…However, other authors [16,17] reported a decrease in the compressive strength of the materials with introduction of EAFD in fly ash based geopolymers, respect a reference without EAFD, for curing temperature below 70 • C. This discrepancy in the trend may be due to the presence of clay, which has influence in the strength development.…”

“…On the one hand, they present zones of high densification, consisting of the aluminosilicate gel formed by the reaction of the amorphous particles of the raw materials used with the activating solution. On the other hand, within these densified zones are unreacted spherical particles, which could be particles belonging to EAFD, fly ash, and clay [16]. Furthermore, as the addition of EAFD is higher it can be observed that the geopolymers are more porous.…”

“…All the analyzed elements As, Ba, Cr, Cu, Mo, Ni, Pb, Sb, Se, Zn, and Cd except for Hg, present a concentration higher than the quantification limit for both, availability and compliance leaching test (Figure 3). Some of these elements such as Zn, Cd, Cu, Cr, and Pb, coming mainly from the EAFD, are retained in the geopolymeric matrix by means of a chemical immobilization in combination with a physical mechanism of microencapsulation [16]. For others such as As, Mo, and Se, there is evidence that chemical immobilization is weak, so unless physical microencapsulation is strong and durable over time geopolymerization is not a suitable treatment for these elements [13].…”

“…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.…”

“…Due to the hazardous nature of EAFD, its use in civil construction should be based on solidification/stabilization technologies. In this way, there are some studies that show the results of incorporating EAFD in processes of geopolymerization of coal fly ash [16,17,37]. On the other hand, it should be noted that there is a significant number of published studies that evaluate the environmental implications of geopolymeric systems based on industrial waste through leaching behavior, but exclusively using a leaching test, mostly the TCLP [38][39][40][41][42].…”