I took a FESEM image of cement paste after 12 hours of hydration. There are numerous fibrillar structures, can anyone help what these structures are (CSH or ettringite)?
The hydration was ceased at 12 hours and samples were dried and coated before the analysis.
regards
saurabh
As clearly visible in your SEM image, all needle shaped microstructure will be ettringite, white colour hexagonal microstructure is unhydrated calcium hydroxide CH, but sheet type microstructure will be CSH, which is rarely visible or absent in this image. Here only ettringite and CH is present and CSH formation has not been occurred at this stage.
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As Mr. Kumar mentioned it could be ettringite (the needle shape structure) and CH (the hexagonal ones). It took some time for CSH formation.
Does this cement paste contain other material than a raw paste?
The microscopy image shows different crystalline phases. To ensure the presence of ettringite, CSH or portlandite, it would be convenient to add the composition to the morphologies. It would be enough to make a mapping of the S, Al and Ca.
In the same way, I suggest mapping in areas with a higher density of acicular crystals. Depending on the area of the detector, the optimization of the EDS system would be important, selecting between the normal variables, an intermediate processing time if the counts are low, and sufficient time during the acquisition. With proper Al and S mapping, phase confirmation could help.
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