The influence of complex additives based on calcined clays and carbonate fillers on hydration products composition of blended cement stone

One of the most effective and recognizable way to solve energy and resource consumption problems in cement industry is the development of blended Portland cement with different combinations of mineral additives. The development of complex additives based on combination of calcined clays and limestone is one of the promising directions. The aim of this work was to study the influence of complex additives based on calcined kaolinitic clay with kaolinite content of 80 % and limestone with calcite content of 99 % on the blended cement stone hydration products at the age of 28 days. Using X-ray diffraction and differential scanning calorimetry the composition of blended cement stone hydration products was studied. It is established that the introduction of 20 % of the complex additive based on calcined clay and limestone leads to a significant decrease of the portlandite content, increase in the number of new growths in form of low-calcium hydrosilicates and calcium hidrocarboalumosilicates, stabilization of ettringiteand calcium hydrocarbosilicates in amorphous phase, that significantly increases the compressive strength. This effect was amplified due to the additional alumina provided by calcined clay reaction