In this study, the influence of the calcined kaolinite content of calcined clay on the hydration of Limestone Calcined Clay Cement (LC3-50) is investigated. It is shown that with the increase of the calcined kaolinite content of the calcined clay, the clinker hydration degree decreases. The amount of reacted metakaolin increases with the calcined kaolinite content, leading to higher formation of C-A-S-H. However, for the LC3-50 with the highest-grade calcined clay, the formation of carboaluminate hydrates is limited. For this blend, the porosity is well refined at 3 days of hydration and does not significantly change later on.