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	Cement Assessment by optical microscopy or SEM Cements can be assessed using broadly the same approach as for clinkers. Generally, as with clinkers, examinations of cements are comparative; two or more cements are best examined which are nominally similar but which show different performance characteristics. The objective is often to determine if the cause(s) of the observed differences in performance are related to mineralogy. Note: the pages on this website refer to 'cement,' used here as shorthand for Portland cement. Other types of cement (eg: calcium aluminate cement) can, of course, also be examined by SEM or optical microscopy.

	Concrete: concrete petrography / concrete by SEM / cement / chromium (VI)

Limitations

There are some significant limitations in examining a cement compared with a clinker:

• cement contains gypsum
• the cement particle size generally precludes assessment of alite crystal size
• the nodule pore structure detail is lost during the grinding of the cement

The gypsum clearly affects the bulk composition, and hence any calculation of mineral proportions. The small cement particle size in relation to typical alite crystal sizes may reduce the extent to which alite size can be used to infer burning conditions.

Circumstances in which cement examination by microscopy may be useful include:

• differences in concrete strengths where nominally similar cements were used and where no other cause is obvious than a difference in cement performance
• differences in cement behaviour with particular admixtures
• determination of non-cementitious material content (eg: limestone)
• assessment of whether two or more cements are likely to have been produced at the same works/kiln (NB: this may or may not be possible, depending on the magnitude and nature of any distinguishing characteristics)

As the reasons for considering a detailed examination of cement vary widely, we suggest you contact us to discuss your particular interests.