This article examines how adding sulfate carriers affects the early compressive strengths of various calcined clay blended cements. Portland cement is blended with 1:1-dominated, common, and 2:1-dominated clays at different sulfate carrier contents. The compressive strengths of their mortars are assessed as Activity Indexes and compared with calorimeter measurements on pastes. The Activity Index of 2:1-dominated clay blends increases by up to 10% with sulfate carrier addition, and oversulfation can occur with more than 1 wt% sulfate carrier addition. In some 1:1-dominated clay blends, this isn’t reached even with 9 wt% addition, with Activity Indexes increasing up to 60%. The impact of sulfate carrier addition on strength is more pronounced at 2 days than at 28 days. There is a very high correlation (R2 ≈ 0.90) between hydration heat and the Activity Index of blended cements at 2 days. When using 2:1-dominated clays, however, strength prediction based on this correlation is limited.     «

This article examines how adding sulfate carriers affects the early compressive strengths of various calcined clay blended cements. Portland cement is blended with 1:1-dominated, common, and 2:1-dominated clays at different sulfate carrier contents. The compressive strengths of their mortars are assessed as Activity Indexes and compared with calorimeter measurements on pastes. The Activity Index of 2:1-dominated clay blends increases by up to 10% with sulfate carrier addition, and oversulfation...     »