Study of electric-arc furnace dust (EAFD) in fly ash and rice husk ash-based geopolymers

Electric-arc furnace dust (EAFD) is an industrial waste produced by the volatilization of metals during scrap melting in electric arc furnaces. This waste is classified as Class I - hazardous, because lead and cadmium concentrations are above the limits set in the leaching test. Processes are carried out in many countries to recover the metals contained in EAFD. In Brazil, these processes are usually not conducted in the industry because the low percentage of commercially valuable metals makes it economically unfeasible to recover them. One of the study alternatives is the use of EAFD in civil construction. Studies have shown that EAFD increases the mechanical strength of mortars and Portland cement-based concretes. However, EAFD delayed cement setting time, which can jeopardize its use in construction. Thus, this study aims to evaluate the effect of EAFD when added to fly ash (FA) and rice husk ash (RHA) based geopolymers. Geopolymer mortars were prepared at a ratio of 1:3 (FA + RHA: sand, four different granulations) and added with 0, 10, 15, and 20% EAFD in relation to the mass of FA + RHA. Compressive mechanical strength and leaching tests were carried out at the ages of 7, 28, and 91 days. Microstructural analyses were performed using XRD, FTIR, and SEM/EDS. EAFD did not negatively influence the geopolymerization process. The highest compressive strength results for the mortars containing the waste were found for 20% of EAFD. All mortars, regardless of EAFD content, were classified as non- hazardous Class II at the age of 91 days. (C) 2017 The Society of Powder Technology Japan. Published by Elsevier B.V. and The Society of Powder Technology Japan. All rights reserved.