Rheology of portland cement pastes with calcined clays additions

摘要

In this paper, the rheological behavior of pastes of Portland cement and different calcined clays additions were analyzed. For this purpose, two Portland cements with different mineralogical composition (low C_3A and high C_3S content and low C_3S and high C_3A content) combined with different replacement percentages of three minerals additions of aluminic nature (quartz as control, and two metakaolins) are used. Mineral admixtures have different crystallinity and morphology: the quartz is fully crystalline; metakaolins are vitreous with a small fraction crystalline. The vitreous phase gives to the calcined clays, pozzolanic properties. All determinations were performed on Haake Roto Visco at 25°C, just on the latency period of hydration. The results show that paste of Portland cement with low C_3A content and high C_3S content presents a great shear strength and the replacement by calcined clays addition affects the rheological behavior of pastes depending on the pozzolanic nature and the reactivity of addition.