Revisiting the microstructure of hydrated tricalcium silicate - a comparison to Portland cement

The microstructures of 0.40 w/s-ratio pastes of tricalcium silicate (C3S), alite and Portland cement have been studied at the hydration times 24 h and 1 month. A field-emission SEM (FE-SEM) was used to obtain high-resolution backscattered electron images. Comparison revealed no microstructural differences between C3S and alite, but there were considerable differences in microstructure between C3S and Portland cement pastes. The microstructure of the C3S paste was simpler than that of the Portland cement, and could be described by a few characteristic features. Distribution of the reaction products differed substantially in the two systems. While hollow shells (Hadley grains) were a prominent feature of the Portland cement paste, their occurrence was more limited in the C3S and alite pastes. Hollow shells were restricted to grains smaller than about 5 mum in the C3S and alite pastes, and gapped hollow shells were not a common feature. (C) 2004 Elsevier Ltd. All rights reserved.