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Technical Cement Forum / Alkalies in pozzolans

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Davo 12/08/2009 08:38:15

Alkalies in pozzolans

Dear friends

It is well known, how alkalies from clinker influence on properties of cement and concrete (ASR etc.). Can anyone tell me about cement total alkalies influence, when with clinker are intergrinded pozzolans. Pozzolans are perlytes and amount of alkalies in perlytes is up to 7%. In that case the total amount aof alkalies in cement is about 2%. Has anyone experience with this matter.

Thanks

srini 1962 27/08/2009 09:20:00

If alkalies are of sodium base, then the early strength of the cement martor is expected to increase slightly. But the later strength will come down.

Michael Clark 27/08/2009 14:24:21

Pozzolana are not necessarily perlytes. The pozzolanic reaction fills the pores in concrete increasing the density and improving the durability.

Davo 27/08/2009 14:45:56

Dear Mr Clark

I know very well what are pozzolans. Pozzolans during hydration of cement react with Ca(OH)2 (with product of reaction of calcium silicates) and form calcium hydro-silicates, so structure of cement paste hardens and durability, hydraulic and sulphur resistant properties of concrete improve.

I asked about influence of such alkalies on properties of cement&concrete (Alkali-Silica Reactions) that enters to cement compositions with pozzolans.

Regards Davit

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