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Author: Subject: Calcium Silicate from concrete rubble?
nikotyna1939
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[*] posted on 18-3-2024 at 02:20
theoretical repursposing


i also just want to know is there another feasible ways to recycle concrete rubble other than Construction aggregate and fillings




[Edited on 18-3-2024 by nikotyna1939]

[Edited on 18-3-2024 by nikotyna1939]
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bnull
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[*] posted on 18-3-2024 at 02:31


Quote: Originally posted by nikotyna1939  
i also just want to know is there other ways to recycle concrete rubble other than Construction aggregate or fillings

Fertilizer. Concrete is rich in calcium (of course), magnesium, and iron, and is a source of silicon for rice and other cultures. It can also be used to adjust the pH of soil.

[Edited on 18-3-2024 by bnull]




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nikotyna1939
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[*] posted on 18-3-2024 at 02:34
Calcium chloride + silica= product ?


what is the main product of reacting Calcium chloride + silica at room tempreature in water ?
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nikotyna1939
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[*] posted on 18-3-2024 at 02:37
very useful products


i meant other very high valued useful products for recycling
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bnull
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[*] posted on 18-3-2024 at 02:48


Quote: Originally posted by nikotyna1939  
what is the main product of reacting Calcium chloride + silica at room tempreature in water ?

Silica is sparingly soluble in water (about 120mg/L). The best case scenario is a light coat of calcium silicate of indefinite composition on the silica particles. It will take years to make an usable quantity of CaxSiyOz.

Quote: Originally posted by nikotyna1939  
i meant other very high valued useful products for recycling

Let me guess: you have a huge pile of rubble lying in your backyard and you want to make money with it. Forget it. Concrete recycling is only economically viable for the industry.

Unless you want to work in landscape designing.

[Edited on 18-3-2024 by bnull]




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[*] posted on 18-3-2024 at 07:13


Quote: Originally posted by bnull  
Quote: Originally posted by nikotyna1939  
what is the main product of reacting Calcium chloride + silica at room tempreature in water ?

Silica is sparingly soluble in water (about 120mg/L). The best case scenario is a light coat of calcium silicate of indefinite composition on the silica particles. It will take years to make an usable quantity of CaxSiyOz.

I'm afraid it would take millions of years for a chemical reaction to take place between SiO2 and CaCl2 in H2O at room temperature, and maybe even that wouldn't be enough;)
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nikotyna1939
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[*] posted on 19-3-2024 at 21:41
Preparation of Calcium Silicate from Calcium Chloride and Silica ?


What is the simple and fastest ways to prepare Calcium Silicate from Calcium Chloride and Silica for about 10 grams ?



[Edited on 20-3-2024 by nikotyna1939]
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[*] posted on 19-3-2024 at 22:05


Quote: Originally posted by nikotyna1939  
What is the simple and fastest ways to prepare Calcium Silicate from Calcium Chloride and Silic Acid for about 10 grams ?

[Edited on 20-3-2024 by nikotyna1939]


That's not the way... Silicic acid is a very weak acid that cannot easily displace HCl. You'd need extremely high temperatures for that to happen! And you might as well use SiO2...I mean, it's nonsense.
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[*] posted on 19-3-2024 at 22:26


A small amount of pure calcium silicate is better to buy;) It is sold, for example, as a pharmaceutical raw material. For example, here: https://www.drhoffmann.cz/kremicitan-vapenaty-cisty-id262.ht...
Although here this company does not sell it cheap...I believe you can find a seller who sells pure CaSiO3 in small quantities cheaply...
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nikotyna1939
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[*] posted on 19-3-2024 at 22:59
temperature for preparing calcium silicate from calcium chloride and silica?


at what temperature do i need for preparing calcium silicate from calcium chloride and silica in 5 minutes?

[Edited on 20-3-2024 by nikotyna1939]
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[*] posted on 19-3-2024 at 23:11


If you have some caustic soda (sodium hydroxide) drain cleaner lying around, the following is a viable route:

Sodium Hydroxide + Silicic Acid -> Sodium Silicate

Sodium Silicate + Calcium Chloride -> Calcium Silicate (precipitate) + Sodium Chloride

The Alkali-Silica Reaction (ASR), otherwise known as concrete cancer, covers the first reaction. Given your interest in obtaining calcium silicate, the end product of these reactions, it's probably good reading material:

https://en.wikipedia.org/wiki/Alkali%E2%80%93silica_reaction

Silica can replace silicic acid:

https://www.youtube.com/watch?v=xltvwhogklI

but be very careful when heating the sodium hydroxide solution (hot concentrated NaOH solutions are dangerous).
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[*] posted on 19-3-2024 at 23:26


Quote: Originally posted by nikotyna1939  
at what temperature do i need for preparing calcium silicate from calcium chloride and silica in 5 minutes?

[Edited on 20-3-2024 by nikotyna1939]


I'm not sure if calcium silicate is formed, but these are the kind of temperatures you need to decompose calcium chloride in the presence of silica:

873K to 1143K

https://www.jstage.jst.go.jp/article/kakoronbunshu1975/9/5/9...
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[*] posted on 20-3-2024 at 05:05


In 5 minutes, starting from calcium chloride and silica? No. The only way to make calcium silicate (of uncertain composition) in 5 minutes or less is by mixing a solution of calcium chloride (or other soluble calcium salt) with a solution of sodium silicate.

Silica is reasonably inert, forms a weak acid and won't displace the chlorine either in solution at ambient temperature or at high temperatures. In the paper pointed by @Precipitates, it is oxygen (or steam) what displaces the chlorine, with silica acting as a catalyst.

Quote: Originally posted by Precipitates  
I'm not sure if calcium silicate is formed, but these are the kind of temperatures you need to decompose calcium chloride in the presence of silica:

873K to 1143K

https://www.jstage.jst.go.jp/article/kakoronbunshu1975/9/5/9...

It's more like CaO diffused in silica, which takes us back to @Admagistr's suggestion of heating the mixture above 1400 °C.

What bothers me is that, when performed under oxygen atmosphere or air, one of the products is chlorine. For a small quantity, say, 5 g of calcium chloride plus silica, the amount of chlorine is (let's say) safe to handle.




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[*] posted on 20-3-2024 at 08:08


Quote: Originally posted by bnull  
In 5 minutes, starting from calcium chloride and silica? No. The only way to make calcium silicate (of uncertain composition) in 5 minutes or less is by mixing a solution of calcium chloride (or other soluble calcium salt) with a solution of sodium silicate.

Silica is reasonably inert, forms a weak acid and won't displace the chlorine either in solution at ambient temperature or at high temperatures. In the paper pointed by @Precipitates, it is oxygen (or steam) what displaces the chlorine, with silica acting as a catalyst.

Quote: Originally posted by Precipitates  
I'm not sure if calcium silicate is formed, but these are the kind of temperatures you need to decompose calcium chloride in the presence of silica:

873K to 1143K

https://www.jstage.jst.go.jp/article/kakoronbunshu1975/9/5/9...

It's more like CaO diffused in silica, which takes us back to @Admagistr's suggestion of heating the mixture above 1400 °C.

What bothers me is that, when performed under oxygen atmosphere or air, one of the products is chlorine. For a small quantity, say, 5 g of calcium chloride plus silica, the amount of chlorine is (let's say) safe to handle.


Good analysis of the problem and you explained it nicely:)!
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