Reactions of Chromium during the Calcination of Cement Clinker Produced Using Steel Slag

Abstract

We investigated the effects of calcination temperature (950–1 450 °C), steel slag content, and the total chromium content of steel slag on the Cr⁶⁺ contents of clinker samples produced using steel slags with different chromium contents. Additionally, the reactions of chromium in clinker (produced using steel slag) during calcination were studied. It is found that Cr⁶⁺ conversion increases with increasing calcination temperature to 1 250 °C, reaching a maximum of 43%–79%, before decreasing to 18%–42% at 1 450 C. Cr⁶⁺ is mainly formed by the oxidation of trivalent chromium (Cr³⁺) during the solid-phase reaction stage of clinker calcination. Furthermore, the Cr⁶⁺ content of a clinker sample is proportional to the chromium content of its raw meal precursor and is mainly in the form of water-insoluble calcium chromate (CaCrO₄). The chromium in clinker is mainly distributed in tricalcium aluminate and tetracalcium aluminoferrite, however, some is present in silicate minerals. We expect to inform the monitoring and control of the Cr⁶⁺ content of clinker (produced using steel slag) and resulting cement.

Keywords

chromium / cement clinker / steel slag / hexavalent chromium / reaction characteristics