Ca3SiO5 (i.e., tricalcium silicate) and its polymorphic representations are the dominant phases present in ordinary portland cement (OPC). With environmental pressures bracketing the production of portland cement, there is increasing emphasis on designing newer, more efficient cement chemistries. While minor impurities in the form of aluminum, iron and magnesium (Al, Fe, and Mg) are understood to have substantial influences on the structure and reactivity of the siliceous cement phases, the specific nature of these influences remains unclear. Across a series of first principles calculations performed at density functional level of theory (DFT), impurities in the form of Mg, Al, and Fe species are inserted in substitutional positions in triclinic Ca3SiO5. Special emphasis is devoted in understanding changes induced in: (a) lattice and crystallographic parameters, (b) mechanical properties and (c) the electronic charge densities. Considerations are provided to better evaluate and determine the preferences for substitutional atomic sites, and rank the stability of the different phases using thermodynamic descriptors. The results suggest that Mg, Al and Fe substitutions alter charge localization and exchange, and contribute a new means to interpret and steer cementing phase reactivity, by careful manipulations of their impurity distributions.

Influence of (Mg, Al, Fe) impurities on triclinic Ca<sub>3</sub>SiO<sub>5</sub>: Interpretations from DFT calculations

247th National Meeting (2014)

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Influence of (Mg, Al, Fe) impurities on triclinic Ca3SiO5: Interpretations from DFT calculations

Influence of (Mg, Al, Fe) impurities on triclinic Ca₃SiO₅: Interpretations from DFT calculations