Abstract
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.
Highlights
As it is well known, tricalcium silicate (3CaO·SiO2, or simplified as C3 S) is the main component of ordinary Portland cement, and it plays an important role in building the strength of the cement paste during its hydration [1,2]
The C3S embedded was measured by serial block-face scanning electron microscopy (SBFSEM), and the instrument operated signals scale with the atomic masses and electron densities within the sample, the brighter features
1110 the atomic masses and electron densities within the sample, the brighter features within the backscattered electron (BSE) micrographs were identified as C3S grains, the darker regions among different brighter grains as epoxy resin, and the remaining darker regions within the grains as pores
Summary
As it is well known, tricalcium silicate (3CaO·SiO2 , or simplified as C3 S) is the main component of ordinary Portland cement, and it plays an important role in building the strength of the cement paste during its hydration [1,2]. The morphology of C3 S grains within the materials has a direct effect on the hydration capacity of cement, the amount of required cement in the cement-based materials, as well as the eventual properties and performance of the cement paste and concrete. For these reasons, researchers often treat the monophase C3 S mineral as a simplified cement for study [4,5,6,7], and so the properties and hydration behavior of C3 S have been extensively investigated [8,9,10,11]. The reported work extends such study to three dimensions, Materials 2018, 11, 1110; doi:10.3390/ma11071110 www.mdpi.com/journal/materials
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