Re: Zinc in Raw Mix

Hello Silastman,

Ahaa. Now I understand the confusion. You wrote "C3A3CaSO4" in your original post which I incorrectly took to be C3A.3CaSO4, whereas what you actually meant was;- C₃.A₃.CaSO₄   or  3CaO.3Al2O3.CaSO4 (Yeelimite).   This is the danger of mixing traditional chemical formulae with cement-chemistry notation, is it not. :)

To answer your original question... I would guess that zinc would not have the same retardation effect on hydration as it does with calcium silicate based cements because there is hardly any Ca(OH)2 released during hydration of the main hydraulic mineral yeelimite.

CSA cement essentially hydrates by reaction of yeelimite (3CaO.3Al2O3.CaSO4 )and anhydrite (CaSO4) with water to form ettringite. With almost no Ca(OH)2 being created at the surface of yeelimite particles during early hydration, there would be little (if any) reaction with zinc to form any insoluble coating of calcium hydroxy-zincate.

However there are normally quite significant amounts of belite (2CaO.SiO2) in CSA cement. Zinc could therefore retard the hydration of any belite present.

Although it is not related to the question of calcium hydroxy-zincate, here is an paper on CSA cement that you may be interested in;-

http://www.springerlink.com/content/m2r34734t0t2150h/fulltext.pdf

Regards,

Ted.

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Re: Zinc in Raw Mix

Thanks Ted,

In order to completely to exclude influence of these oxides on process of clinker formation & hydration of cement we with colleagues from physico-technical faculty have decided completely them to remove & restore up to metal. Especially their cost is more, than cement.

With the best regards,

Silastman

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