Effect of Cr on the Mineral Structure and Composition of Cement Clinker and Its Solidification Behavior

Abstract

In order to reveal the solidification behavior of Cr in the cement clinker mineral phase, 29Simagic-angle spinning nuclear magnetic resonance, X-ray diffraction, and scanning electronmicroscopy with energy-dispersive X-ray spectroscopy techniques were used to analyze themorphology and composition of the cement clinker mineral phase doped with Cr. The resultsshowed that the addition of Cr did not change the chemical environment of 29Si in the clinkermineral phase, and it was still an isolated silicon−oxygen tetrahedron. Cr affected the orientation ofthe silicon−oxygen tetrahedron and the coordination number of calcium, leading to the formationof defects in the crystal structure of the clinker mineral phase, by replacing Ca2+ into the mineralphase lattice to form a new mineral phase Ca3Cr2(SiO4)3. Cr acted as a stabilizer for the formation ofβ-C2S in the clinker calcination. As the amount of Cr increased, the relative content of C3S decreasedand the relative content of C2S increased. Further, Cr easily dissolved in C2S, while it was not foundin C3S. This study is conducive to further research on the mechanism of heavy metal solidificationin cement clinker. Furthermore, it is important to evaluate the environmental risk of heavy metalsin the process of sludge disposal through cement kiln and promote the utilization of sludgeresources and the sustainable development of the cement industry.

Keywords

• clinker
• heavy metal
• solidification
• 29si mas nmr
• cr