Page 39 - New Trends in Green Construction

FEASIBLE USE OF ELECTRIC ARC FURNACE DUST AS A SECONDARY RAW MATERIAL IN SELF-COMPACTING MORTAR PRODUCTION
Angélica Lozano-Lunar, Pedro Raposeiro da Silva, Jorge de Brito, José María Fernández, José Ramón Jiménez
Keywords: Electric arc furnace dust, self-compacting mortar, secondary raw material, circular economy, 1. Introduction
The new model of Circular Economy has the aim of a closed cycle of waste management in which these are reintroduced into the productive process. Construction materials, specifically the mortar/concrete industry, stand out for a high consumption of raw materials (Rattanashotinunt, 2018). Therefore, these materials are the focus of implementation in the search for a more environmentally sustainable material. One of these actions is the partial or total use of secondary raw materials (SRM) to replace natural raw materials. In the production of steel, during the scrap fusion, a pulverulent by-product named electric arc furnace dust (EAFD) is generated (Issa, 2013). These materials have a high heavy metal content and their management is by landfill. This action is not consistent with the Circular Economy. Therefore, this research uses two EAFD as SRM in obtaining self-compacting mortars to avoid their deposit in landfill. The viability of using EAFD was analysed through the mechanical and leaching behaviour of mortars. The results obtained contribute to waste management through its valorisation as SRM in the self-compacting mortar production, addressing an unexplored research line.
2. Materials and methods
The self-compacting mortar dosage was defined by the Nepomuceno method (Nepomuceno, 2005). A reference self-compacting mortar (SCM) was produced using cement CEMI/42.5 R (CEM), siliceous filler (SF), two natural sand (NS0/2 and NS0/4) and a superplasticizer (Sp). Four self-compacting mortars were produced by replacing the SF by two EAFD (R1 and R2) in percentages of 25% and 100% by mass (SC1-25, SC1-100, SC2-25 and SC2-100). From each mix, prismatic specimens (40 mm x 40 mm x 160 mm) were manufactured and stored under climatic conditions (95% ± 5% relative humidity and 20 oC ± 2 oC of temperature) up to the test age. The mechanical viability was analysed through compressive strength evolution at 7, 28 and 56 days (UNE-EN 1015-11:2000). The environmental assessment was carried out through leaching tests in monolithic (XP X31-211: 2012) and granular states (UNE-EN 12457-4: 2003). The metal release results were compared with the "Non-Hazardous" limit of the European Directive 2003/33/EC to self-compacting mortars classification.
3. Results and conclusions
The compressive strength decreased with the EAFD incorporation (Fig. 1 a) and b)), due to the detriment produced by heavy metals in the cementitious matrices (Lasheras-Zubiate, 2011). However, SC2-25 (65.28 MPa) only recorded a loss of 1.4% compared to SCM (66.20 MPa). In monolithic state (Fig. 1 c) and d)), metal releases remained below the limit in all elements. Therefore, all self-compacting mortars were classified as "Non-hazardous". In granular state (Fig. 1 e) and f)), SC1-25, SC1-100 and SC2-100 were classified as "Hazardous" because the Pb release
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New Trends in Green Construction