Title:
Optimization of the early compressive strength of calcined clay blended cements by sulfate carrier addition
Author(s):
Maximilian Panzer, Sebastian Scherb, Nancy Beuntner, Karl-Christian Thienel
Publication:
Symposium Paper
Volume:
370
Issue:
Appears on pages(s):
79-98
Keywords:
Calcined clay; Calorimetry; Common clay; Illitic clay; Kaolinitic clay; Mortar compressive strength; Smectitic clay; Sulfate carrier addition; Supplementary cementitious material
DOI:
10.14359/51751751
Date:
5/1/2026
Abstract:
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.
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