Gypsum is one of the byproducts in phosphatic fertilizer manufacturing. Apart from using it in cement manufacturing and also as fertilizer, I feel there is still an unexplored region for the utilization of gypsum. But it is one of the most inert substances, so I wanted to know if there is any way one can increase the reactivity of gypsum to make it into a much more valuable product.
Requesting my community for any help/ followups/suggestions
Dear ,
which kind of gypsum are you talking about? Gypsum is not reactive only if it’s naturally stabilized by 2 molecules of water so Ca SO4 2 H2O.
If your by product has this formula I confirm it’s stable but not reactive. It’s quite easy to increase its reactivity by calcining at quite low temperature (find on internet the specific temperature but is below 180°C) for necessary time to reduce the crystal water of 1,5 molecules. The resultant Gypsum is called hemi hydrate (Ca SO4 1/2 H2O) and it‘s super reactive and when you add water it develop heating and harden within 20 minutes.
If you calcine too much eliminating all molecules of water you obtain other reactive calcium sulphate called anhydrite (Ca SO4). It’s less reactive but when you add water in an hour will harden.
If you calcine too much ant till 600°C you could obtain a superficially glazed anhydrite so completely not reactive if you don’t add a catalyzer (find on internet which one because are more than one ) and again you will have an hardening between 30 to 80 minutes depending on the amount and the yield of the accelerant.
Hoping to have been useful
Best regards
Alex Reggiani
Alex Reggiani thank you for your answer. I am talking about phospho gypsum (CaSO4.2H2O) which is a by-product of phosphoric acid manufacturing.
Actually, I was asking about the reactivity of gypsum with other chemicals/reagents, not water.
Are you asking to use your by product that isn‘t reactive because it’s already hydrated with 2 molecules of water (like Natural Gypsum of course) as binder of something, isn’t it?
In this case you have to calcine a little to reduce the crystal water inside your by product that is the same is done with natural gypsum to be used industrially for doing plasters or gypsum boards.
Admixtures in powder can be used as catalysts of reaction (hydration) to harden only if you removed completely , before using the additive, the crystal water (that is your problem if I have understood well your question ) inside your material CaSO4.2H2O.
Making everything without considering the internal water is useless.
Let me know if I wronged.
Regards
Alex