Celitements are designated as hydraulic calcium hydrosilicates (hCHS). Is this just a slip of the pen or what is the difference from the familiar calcium silicate hydrates (CSH or C-S-H)?

No, we chose the notation very deliberately. Unfortunately, in this field there are historically different and not actually formally established ways of designating calcium silicate hydrates. In the cement chemist’s notation the important main elements are designated with the letters C, S and H. C stands for calcium or CaO, S for silicon or SiO2 and H for water (H2O) but also for the hydroxyl group (OH). The amorphous and poorly ordered structure of the phases that are formed from the hydration of the two main silicate phases C3S and C2S in the classical Portland cement is frequently, but not always, expressed by hyphens between the letters. We also follow this notation with C-S-H for the end product of Celitement hydration. However, the intermediate autoclave products of the Celitement production process are also calcium silicate hydrates. This can involve the fairly crystalline alpha-C2SH phase but also amorphous C-S-H phases. To differentiate the autoclave product from the end product and because the rather crystalline alpha-C2SH was produced at the beginning of the development of Celitement, we write the phases from the autoclave without hyphens, i.e. as the CSH phase. It can be done in this way but does not have to be. C-S-H would be just as correct a way of writing or just as wrong. Ultimately it is only a matter of stoichiometric but not structural notation. This material is converted tribochemically in the activation grinding into what we designate calcium hydrosilicate (CHS). The H moves to the middle of the notation. As a consequence we write the phase as hCHS, where the h stands for hydraulic. The sequence of the conversions along the Celitement production process is therefore as follows: CSH → hCHS → C-S-H.

What does the name “Celitement” actually mean?

This designation, which stands for both the company and the product, does not roll too easily off the tongue. The dual usage can even lead to confusion. There are also two different ways of writing it. Our original logo started with a C with a triangle above it. This is the geochemist’s symbol for CO2. Then “lite” written vertically in blue. As in Cola light/lite this stands for light or virtually free – in this case from CO2. The “ment” at the end indicates the product group, i.e. cement. This is somewhat impractical to write so the spelling has become established in which we have simply inserted the “lite” into the middle of the English word “Cement”. This then gives Ce-lite-ment or simply Celitement®….

Why is calcium silicate hydrate sometimes written without hyphens (CSH) and sometimes with them (C-S-H)?

Because (unfortunately) there is no consensus on the subject in the scientific community. There are in fact also similar problems with the nomenclature for the main clinker phase in Portland cement, the “alite”. This tricalcium silicate is usually written as C3S but sometimes in the form of an empirical formula as Ca3SiO5 or as 3CaO∙SiO2. To be entirely correct the designation should be tricalcium oxy silicate Ca3O(SiO4) as alite structurally contains oxy anions O2. This means that the confusion in the notation prevails right through from the water-free compounds to the compounds that contain water or hydroxyl groups.

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