Speciation of Cr in cement clinkers obtained from co-burning with Cr2O3

XANES was used as complementary to XRD for the investigation of speciation of Cr in cement clinkers prepared by the co-burning of raw meal blended with Cr2O3. The concentration of Cr in the mixture was 0.1, 0.5, 1.0, 2.0, 5.0, and 10.0 wt%. The mixture was burnt at 1450 °C for 90 min. XANES spectra show that all samples contain Cr6+ species. A similar ratio of different Cr containing compounds was found for all clinkers with a Cr concentration of 2.0 wt% and below. A discrepancy between XANES spectra and the changes in free lime concentration was observed when the Cr concentration increased from 1.0 to 2.0 wt%. Above 2.0 wt%, complicated changes in the XANES spectra were observed with increasing Cr concentration. Different Cr-compounds were formed in all samples, and reduction of free lime content was observed for the sample with a Cr concentration of 10.0 wt%.