Calcination Variability and Dispersant Demand

Hemihydrate surface area, soluble anhydrite content and trace impurities all vary with calcination conditions. Each of these directly changes how much dispersant you need to hit a target slurry fluidity.

A kettle running hot for two shifts produces a stucco that needs less PCE; the operator notices nothing because the slurry still flows at the standard dose. The result is over-dispersion, extended set, and a soft board at the knife.

The fix is not exotic: a daily fluidity-cone check on a standardized slurry, run by the same person at the same time. The number is more useful as a trend than as an absolute. When it drifts, dose to it, not to the recipe.