Influence of iron content of chemically and mineralogically modified electric arc furnace slag on the hydration and environmental behaviour of composite cements

Abstract

This work investigates the influence of the iron content of tailored electric arc furnace slag (EAFS) on hydration and strength development as well as associated heavy metal leaching properties of Portland composite cement. Further, the impact of limestone additions was investigated. EAFS from scrap smelting plant was used as starting material. Tailored EAFS was produced by re-melting, conditioning, and water quenching. By that, a glassy material with defined chemistry was obtained. The tailored EAFS strongly contributed to the compressive strength development between 7 and 28 days. Composite cements containing 35 wt.-% EAFS reached an activity index above 85 % after 28 days. The addition of limestone and amine-based quality improvers resulted in an increase of the reached compressive strength at all tested ages. That is linked to the accelerated and increased AFm phase formation. This effect is more pronounced for EAFS with high iron content. Contrary, C-S-H formation was promoted if EAFS with low iron content was used. Chromium leaching was not critical despite the high content in the tailored EAFS. The lowest vanadium leaching was observed for EAFS with low iron content.