Page 81 - New Trends in Green Construction

POSSIBLE USE OF FINE RECYCLED CONCRETE AGGREGATES IN THE IMMOBILIZATION OF ELECTRIC ARC FURNACE DUST (EAFD)
Enrique F. Ledesma, Angélica Lozano-Lunar, José Ramón Jiménez, José María Fernández, Ruan L. S. Ferreira
Keywords: immobilization, recycled aggregates, electric arc furnace dust, circular economy 1. Introduction
The Europe 2020 strategy aims to generate smart, sustainable growth and bet on an efficient economy in the use of natural resources. The concept of "circular economy" appears whose objective is to make efficient the use of resources based on the principle of "closing the life cycle" of the products.
Another type of waste generated is the powder of the electric arc furnace (EAFD) from the manufacture of steel from scrap. This waste is generated during steelmaking, and is toxic due to the zinc, lead and cadmium content (Tahir Sofilić et al., 2004). According to Decision 2014/955/EU of the European Union, gaseous effluents containing hazardous substances are classified as hazardous waste.
Decision 2003/33 / EC of the Council of the EU establishes the criteria for classifying materials according to the concentration of heavy metals and anions in: inert, non-hazardous and dangerous. Sometimes, the concentration of some metals exceeds the limits even to be classified as dangerous, so it must be reduced so that they can be disposed of in landfills for that purpose. To reduce this concentration, the EAFD must be immobilized. There are several studies in which cement-based materials are used to immobilize hazardous materials (Jin and Al-Tabbaa, 2014, Navarro-Blasco et al., 2013).
The objective of this study is to study the feasibility of using the concrete recycling aggregate (ARH) for the immobilization of the EAFD and its deposit in landfills.
2. Material and methods
Two families of mortars have been manufactured: (i) from natural aggregate as a reference, and (ii) with recycled concrete aggregate.
The mortar was dosed in weight with the following percentages of its components: 30% cement (CEMI 42.5 R / SR), 40% aggregate (natural or recycled-depending on the family in each case) and 30% siliceous filler. Table 1 shows the dosages that have been used. The amount of water was added experimentally to achieve a liquid consistency of the mortar within the limits of 230 ± 10 mm on shaking table (UNE-EN 1015-3: 2000). To evaluate the properties of the manufactured mortars, the following tests were carried out: i) density of the hardened mortar; ii) mechanical properties of the mortars, for this purpose cylindrical specimens of 80mm in height and 40mm in diameter have been used; iii) the rate of delitescence (XP X31-212) and iv) the study of environmental risk through the leaching test.
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