This paper looks at the effect of fineness of the different components in a blend containing 55% Portland cement, 30% calcined clay and 15% limestone. The calcined clay originates from a natural deposit in Cuba and contains less than 50% kaolinite. The particle size distribution (PSD) of each of the three components was varied by using different grinding times, and the consequences on heat release, strength development, pore structure and phase assemblage development were investigated up to 28 d. Higher fineness of both clinker and calcined clay can considerably improve compressive strength at all ages, while limestone fineness only plays a role at early age. The formation of carboaluminate hydrates owing to the combined addition of calcined clays and limestone is confirmed for this case of a mixed clay with moderate kaolinite content.