Belite-Ye’elimite-Ferrite cements, BYF, are a sustainable alternative to OPC to reduce CO2 emissions. The aim of this research is to understand the influence of the sulfate source on the hydration of two laboratory-prepared BYF-cements. One studied clinker contained β-belite and orthorhombic-ye'elimite (non-active), and the other one α'H-belite and pseudo-cubic-ye'elimite (activated with borax during clinkering). Pastes were mainly characterized through Rietveld-quantitative-phase-analysis of powder patterns, thermal analysis and scanning-electron-microscopy. Active-mortars developed higher compressive strengths than non-active-mortars, independently of the sulfate source. The highest values for active-mortars (w/c=0.55) were 40±1MPa (28d) with anhydrite, and 68±1MPa (120d) with gypsum.
