Investigation of Three-Dimensional Microstructure of Tricalcium Silicate (C₃S) by Electron Microscopy.

A serial block-face scanning electron microscopy (SBFSEM) system, composed of a scanning electron microscope (SEM) and an ultra-microtome installed within the SEM vacuum chamber, has been used to characterize the three-dimensional (3D) microstructure of tricalcium silicate (C₃S) grains embedded in epoxy resin. A selection of C₃S grains were segmented and rendered with 3D-image processing software, which allowed the C₃S grains to be clearly visualized and enabled statistically quantitative analysis. The results show that about 5% of the C₃S grains have volumes larger than 1 μm³ and the average volume of the grains is 25 μm³. Pores can also be clearly seen in the biggest C₃S grain, the volume of which is 3.6 × 10⁴ μm³, and the mean volume and total volume of all the pores within this grain are 4.8 μm³ and 3.0 × 10³ μm³, respectively. The reported work provides a new approach for the characterization of the 3D spatial structure of raw C₃S materials, and the resulting 3D structure of the raw C₃S is important for further systematic research on the relationships between the spatial microstructure and the hydration kinetics of C₃S and other cement minerals.