Hydration of belite–ye'elimite–ferrite cements with different calcium sulfate sources

Belite–ye'elimite–ferrite (BYF) cements are a sustainable alternative to ordinary Portland cement in attempts to reduce carbon dioxide emissions. The aim of this research was to understand the influence of the sulfate source on the hydration of two laboratory-prepared BYF cements. One of the studied clinkers contained β-belite and orthorhombic ye'elimite (non-active) and the other contained α′H-belite and pseudo-cubic ye'elimite (activated with borax during clinkering). The pastes were mainly characterised through Rietveld quantitative phase analysis of powder patterns, thermal analysis and scanning electron microscopy. The active mortars developed higher compressive strengths than the non-active mortars, regardless of the sulfate source. The highest values of compressive strength for active mortars (w/c = 0·55) were 40 ± 1 MPa (28 d) with anhydrite and 68 ± 1 MPa (120 d) with gypsum.