Polimorfismo das fases do clínquer na hidratação e microestrutura do cimento Portland de alta resistência inicial

Abstract

Environmental-related issues impose several challenges concerning the production of Portland cement worldwide. This is chiefly because of its association with CO2 emissions due to the production processes. Since clinker replacement is one strategy for reducing the impact on emissions, the challenge is bigger when considering high early strength ordinary cement types. These types contain the highest amount of clinker, usually adding only 5% of limestone filler and gypsum. Since early-age hydration is of great interest, systematic studies are necessary to understand the reactivity of C3S, which is responsible for such performance. The C3S phase has seven polymorphs, although two (M1 and M3) are mostly reported in industrial cement. This study examined the hydration behavior of four industrial high early strength Portland cement, focusing on the behaviour of clinker polymorphs. The samples were evaluated by X-ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy and energy dispersive scanning electron microscopy (SEM-EDS), and thermogravimetric analysis (TGA). The results showed that the C3S phase of the clinker, particularly the M1 polymorph, strongly correlates with the formation of portlandite. The reduction in M1 polymorph phase due to hydration is directly associated with formation of Ca(OH)₂, with a better correlation than C3S content. In contrast, C2S showed no significant correlation with portlandite at the ages studied. Iron contents influenced the iron/aluminum ratio of AFt/AFm phases during hydration. Thus, the study of polymorphs is important for assessing strategies for improving the production of Portland cement, especially in terms of energy and early-age performance efficiency.