Effect of phosphorus-doping on ternesite: Structure, thermal stability and hydration

The successful synthesis of the solid solution Ca 5 (Si 1- x /2 O 4 ) 2 S 1- x /2 P x O 4 (C 5 S 2 S ̅ P x , x = 0.05, 0.10, 0.15, 0.20) was confirmed through analysis of X-ray diffraction and energy dispersive spectrometer data. Rietveld refinement revealed that the purity of ternesite can reach up to 99.42 % at a doping concentration of 5 %. Furthermore, changes in X-ray diffraction peaks and morphology suggest a shift in the preferred growth direction of crystallites as a result of the introduction of impurity element. The incorporation of P elements in C 5 S 2 S ̅ P x not only effectively reduces weight loss under high-temperature conditions but also elevates the temperature at which decomposition occurs. Isothermal calorimetry data indicates that C 5 S 2 S ̅ P x -CSA samples display higher cumulative heat release compared to C 5 S 2 S ̅ –CSA. Furthermore, the presence of C 5 S 2 S ̅ P 0.20 accelerates the hydration kinetics of CSA cement by hindering ettringite formation . Moreover, varying levels of phosphorus doping in C 5 S 2 S ̅ P x have resulted in enhanced compressive strength at various ages of CSA cement maturation.