MICROSTRUCTURE DEVELOPMENT IN BLENDED CEMENTS MADE WITH MEDIUMGRADE CALCINED KAOLINITIC CLAYS: EFFECT ON DURABILITY INDICATORS

The objective of this work is to evaluate the influence of the structural arrangement of kaolinite present in medium grade clays, calcined and ground, on the development of the microstructure of pastes and its effect on durability indicators. For this purpose, three kaolinitic clays were used, then blended cements containing 25% of calcined clays were elaborated. The evolution of the microstructure in pastes was studied using XRD, DTA/TG and MIP. Two durability indicators were determined in mortars at 28 days: capillary suction velocity and water vapor diffusion coefficient. The results obtained show that, for clays with similar kaolinite content, the disordered structure of kaolinite will favor resistance to water transport (smaller pore volume with diameter greater than 60 nm) and will not be favorable for water vapor transport (larger pore volume with diameter less than 30 nm).