Probing the exact form and doping preference of magnesium in ordinary Portland cement clinker phases: A study from experiments and DFT simulations

Abstract A systematic study was performed to learn the exact existence form and doping behaviors of magnesium in ordinary Portland cement (OPC) clinker. Our results show that about 1.3 wt% MgO incorporates into OPC clinker phases by forming substitutional solid solutions while excess Mg accumulate and exist as periclase. Results from Rietveld refinement present a substitution preference in C3S and C3A over C2S. More in-depth analyses from density function theoretical simulations show that in C3S, C2S and C3A, the substitution occurs by replacing Ca while in C4AF, it probably occurs by substituting Fe and Ca ions. The large structure distortions and sharp increase in formation energies with increasing MgO determines its low solubility. This work provides a clear understanding of the existence states and the intrinsic mechanism governing doping behaviors of Mg, thus should be very important in guiding the synthesis of OPC clinker by utilizing high-Mg limestone.