EUROPEAN STEEL TECHNOLOGY AND APPLICATION DAYS 2017 - ESTAD 2017

By mass, slag is the largest residue in iron and steelmaking. Due to excellent properties as a construction material slag is rising in popularity as a resource. Before slag can be used there are some restrictions that must be fulfilled of which the leaching of chromium is one. For slag to be considered inert material the leaching limit for chromium is at 0.5 mg/kg. The leaching of slag is governed by the leachability of the minerals. Not all minerals can contain chromium, by eliminating the soluble minerals that contain chromium the chromium leaching should decrease. The composition of low alloy EAF slag was altered by remelting the slag with different amounts of SiO2 additions. By changing the basicity the mineralogical composition is altered. The compositions of the samples were identified using SEM EDS and XRD. As ageing may affect the leaching of slag, the samples were run in an autoclave to simulate ageing before the leaching test. The autoclave treatment was successful as the remelted slag without any modification leached with the same magnitude as the naturally aged reference sample. The investigated slag had the highest leaching of chromium, at average 2 mg/kg, when basicity was 2.7. The chromium leaching decreased to 0.1 mg/kg as basicity were changed to 2.4. The decrease of leaching can be connected to the decrease of the chromium bearing phase: brownmillerite. Lower basicity did not eliminate leaching of chromium as merwinite, another mineral able to contain chromium, was formed instead of brownmillerite.