Direct observation of C3S particles greater than 10 μm during early hydration

Abstract

Fast tomography, a non-destructive imaging technique, was used to study the spatial behavior of monoclinic tricalcium silicate (mC3S) from the first few seconds to one hour of hydration at a water to solids ratio of 0.43. The microstructure evolution of over 9,000 individual particles was directly observed and analyzed at 1 μm per pixel. These particles have an estimated diameter of 10 to 31 μm. These particles occupy ≈ 70 % of the total solids volume of the paste sample and so understanding the changes during hydration is important. The results show that these mC3S particles dissolve and contribute a significant amount of ions that likely participate in subsequent reactions. The dissolution of these particles occurs in localized regions with an observed depth of up to 6 µm. The findings show that these particles cannot be ignored in hydration reactions and these observations can provide further insights into the mechanism of the initial dissolution of hydration.