Calcined clay-based mineral addition for the production of structural concrete

This paper presents the results of the work to develop a mineral addition produced with a blend of 60% of calcined clay of kaolinitic origin, 30% of limestone and 10% of gypsum, to be added as Supplementary Cementitious Material directly while mixing concrete. The clay used has a kaolinite content within 40-50%, and has been activated at 800°C. The three components have been interground at a ball mill. The influence of the addition on cement hydration has been studied aided by Isothermal calorimetry of cement pastes having mineral additions of 35% and 50% per weight. Concrete with the minimum cement content required for the most aggressive exposure class (350 kg/m³) has been cast and mineral additions of 17% and 34% per weight have been made. Concrete strength went above 45 MPa, despite having the minimum cement content.