Black Dross Leached Residue: An Alternative Raw Material for Portland Cement Clinker

The possibility of adding an aluminium black dross leached residue (BDLR), mainly consisted of spinel (Al2MgO4) and corundum (Al2O3), in the raw meal for the production of Portland cement clinker was investigated. This leached residue was obtained during the hydrothermal treatment of an aluminium black dross, formed during aluminium scrap melting. The process consisted of crushing and grinding of the as received dross, sieving it to recover the Al metal value, water leaching at high temperature to dissolve the salts and, finally, aluminium recovery by alkaline pressure leaching. Three samples of raw meals were prepared, one with ordinary raw materials, as a reference sample ((PC)Ref), and two others with different content (2 and 4 wt%) of BDLR ((PC)BD-2% and (PC)BD-42%). All raw meals were sintered at 1,450 ◦C and the produced clinkers were characterised by chemical analysis, X-ray diffraction (XRD), thermogravimetric/differential thermal analysis (TG/DTA) as well as scanning electron microscopy. The produced cements were tested by determining their grindability, setting time, compressive strength and expansibility. The hydration products were examined by XRD analysis at 2, 7 and 28 days. The results of the physico-mechanical tests showed that BDLR could be utilized as a raw material in the cement clinker production, presenting a promising alternative to disposal in landfills.