Unraveling the doping preference of zinc ions in sulfoaluminate cement clinker minerals: A study combining experiments and DFT calculations

Abstract

Combining X-ray diffraction, elemental distribution spectroscopy, and density functional theory simulations, we systematically studied the doping preference of zinc ions in sulfoaluminate cement (SAC) clinker. Our results show that Zn atoms prefer to enter into C4AF while hardly into the other two minerals, C4A3S‾ and C2S. Quantitative analyses of the doping behaviours of Zn in C4AF were also performed with Rietveld refinements. The Zn atoms as solid solute tend to occupy the sites of Fe, which is well supported by the low formation energy, small local structural distortions, and bond order-bond length distribution overlaps between the host and the guest ions. The difference in electron contributions of spatial distributions between Zn–O and Fe–O may be the main reason determining the solid solution of Zn. The deep insights on these fundamental issues should provide an efficient way to improve the solid solution of Zn by increasing the C4AF content, thus should be helpful in guiding the synthesis of SAC clinker by utilizing Zn-bearing solid waste.