LC3 works on the synergy between clinker, calcined clay and limestone phases. Calcined clay reacts with hydration products of clinker and limestone reacts with calcined clay, giving phases that make the microstructure denser. Calcined clays have been long used as pozzolanic materials in cements and limestone is an established semi-reactive filler in cements. The added synergy from the reaction of calcined clays with limestone producing carboaluminate phases improves the strength and durability of the cement.