Application of electric arc furnace slag in building concrete: environmental and structural characterization

Abstract

Recycling industrial by-products into sustainable building products is essential for advancing to a circular economy. These products must meet structural requirements and be environmentally safe and not contaminate soil or water through leaching. This study assesses the leaching of hazardous elements into the environmental and the structural performance of replacing natural aggregate with Electric Arc Furnace Slag (EAFS) in the manufacture of structural concretes (Fcu ? 25 MPa). The study compares Slag Concrete (SC) and Limestone Concrete (LC) as a reference, throughout different stages of the life cycle of the material. A battery of harmonized leaching tests, including dynamic surface, granular compliance, percolation, and pH-dependence tests, were conducted alongside mechanistic modelling to evaluate the performance of slag-based concrete across different scenarios. The study found that among the trace elements, As, Ba, Cd, Cr, Cu, Hg, Mo, Ni, Pb, Sb, Se, V and Zn, determined in leachates, during the service life stage, only Vanadium (V) showed significant leaching differences in EAFS-based concrete, with diffusion being the main release mechanism. At the end-of-life stage, granular specimens met European inert material standards for secondary resource use. The pH-dependence test revealed varying leaching behaviours, likely due to surface adsorption with Fe oxides for Chromium (Cr) and solid solution formation with cement minerals for Molybdenum (Mo) and Vanadium (V). The results highlight the importance of multiple leaching tests for thorough environmental assessment during the product lifecycle. The results obtained can contribute to the basis of a pre-normative study for the use of EAFS aggregate in the manufacture of structural concretes and thus move towards sustainable building.