Sciencemadness Discussion Board

Calcium Silicate from concrete rubble?

nikotyna1939 - 12-3-2024 at 09:17

Is it possible to extract and purify Calcium Silicate from concrete rubble in the range 90 to 98 percent in purity?




[Edited on 12-3-2024 by nikotyna1939]

bnull - 12-3-2024 at 11:44

No. Concrete is made of cement, which is mainly calcium silicates and aluminates (and carbonate, of course). You can't separate them physically because the particles or whatever are very small, well mixed and in the solid state. They don't melt without decomposing and they're also insoluble. You can't separate them chemically without destroying them.

You would have more luck synthesising it. Buy sodium silicate and calcium chloride, make solutions of each, mix them in the right proportion and, lo and behold, your own high purity calcium silicate.

Route by dissolving concrete rubble in HCL to get Calcium Chloride?

nikotyna1939 - 12-3-2024 at 14:57

What if I dissolve concrete rubble to get Calcium chloride first and purify it and after that reacting the Calcium Chloride with Sodium Silicate?

Concrete + HCL= products ?

nikotyna1939 - 12-3-2024 at 15:02

What is the formula products of the reaction betwen Concrete + HCL ?

Calcium Chloride substitute?

nikotyna1939 - 12-3-2024 at 15:09

Can i use Calcium Sulfate as a substitute for the Calcium Chloride?

The main reasons of using concrete rubble

nikotyna1939 - 12-3-2024 at 15:19

I'm going to use concrete rubble because I BELIEF IN THE 3R PHILOSOPHY REUSE, REDUCE AND RECYCLE!

Also to reduce monetary budgets.



[Edited on 12-3-2024 by nikotyna1939]

Admagistr - 12-3-2024 at 16:27

If you use CaCl2 and Na2SiO3 you get a basic calcium silicate of fluctuating composition. CaSO4 is almost insoluble in water, very slightly soluble in H2O, so it is hardly a substitute for CaCl2. Truly pure calcium silicate of solid composition can be obtained by fusing a stoichiometric mixture of SiO2 and CaCO3 (CaO) at high temperatures, just over 1400 C.

clearly_not_atara - 12-3-2024 at 18:39

You can just buy wollastonite IIRC

Precipitates - 12-3-2024 at 20:01

Quote: Originally posted by nikotyna1939  
What if I dissolve concrete rubble to get Calcium chloride first and purify it and after that reacting the Calcium Chloride with Sodium Silicate?


It's possible. But concrete rubble will dissolve very slowly, so best to grind the rubble to a powder first.

Quote: Originally posted by nikotyna1939  
What is the formula products of the reaction betwen Concrete + HCL ?


Depends on the composition of the concrete - calcium, aluminium and iron chlorides can be expected.

https://www.sciencedirect.com/topics/materials-science/portland-cement#:~:text=Portland%20cement%20(OPC)%20consists%20of,continuous%20compact%20mass%2 0of%20masonary.
Quote: Originally posted by nikotyna1939  
Can i use Calcium Sulfate as a substitute for the Calcium Chloride?


Possibly, but calcium sulfate isn't very soluble (approx 2 g/litre), however it is much more soluble than calcium silicate (< 0.1 g/litre). So if you dissolve approx 1 g calcium sulfate in 1 litre of water, then react with sodium silicate, if you see the solution going cloudy you can tell it's working.

Quote: Originally posted by nikotyna1939  
I'm going to use concrete rubble because I BELIEF IN THE 3R PHILOSOPHY REUSE, REDUCE AND RECYCLE!

Also to reduce monetary budgets.

[Edited on 12-3-2024 by nikotyna1939]


Unfortunately, when you take into account the cost of the hydrochloric acid and the other chemicals as required, it won't save money or resources. Best use for old concrete rubble is as hardcore (as a component of construction aggregate).



The other reasons of not just buy calcium silicate

nikotyna1939 - 12-3-2024 at 23:10

I don't just buy calcium silicate because in my area you need to buy calcium silicate in bulk quantity like 100 kg to get a reasonable price.

also i needed only about 10 kg only.

chornedsnorkack - 13-3-2024 at 00:20

How commonly available is calcium silicate from silicate bricks - new bought, demolition rubble or building leftovers?

bnull - 13-3-2024 at 04:40

@nikotyna1939: Forgive me the question but, why do you need 10 kg of it? Depending on the use, you can find something even better and easier to get. Or you can buy the sodium silicate and the calcium chloride and make your own. I know that you'll get a "basic calcium silicate of fluctuating composition". Even so, if the requirements are for a generic calcium silicate, never naming one in particular, you'll be in the same ballpark as concrete.

Try to find some rice farmer who buys it in bulk and try to buy some from him. If he has a 1000 kg stockpile, for example, 10 kg will be peanuts for him. I don't know how much he will charge you. And if you're a rice farmer yourself, buy the 100 kg. It will last a lifetime. Or use the crushed concrete. The advantage is that you also enrich the soil in magnesium and iron.

@chornedsnorkack: You mean silicate recovery, as suggested first in the post? The calcium silicates formed during the firing of the bricks are impregnated with silica (that one) and other silicates (aluminum, magnesium, iron possibly, sodium perhaps), not to mention alumino silicates and whatnot.

Same problems again, mate.
Quote:

You can't separate them physically because the particles or whatever are very small, well mixed and in the solid state. They don't melt without decomposing and they're also insoluble. You can't separate them chemically without destroying them.

You may even recover (some of) the calcium by leaching the crushed bricks with acid (which, I suppose, produces the same unbearable smell as crushed concrete with acid). But you don't want to crush them. Unless you have a way to make the process dust-free and are using your PPE, you risk silicosis. Not much funnier than asbestosis, you see.

To long, didn't read: If you want calcium silicate, buy it. If you have a furnace, make it from sand and lime. If it is for farming, use the concrete as it is, the plants won't care.

chornedsnorkack - 13-3-2024 at 09:17

Quote: Originally posted by bnull  


@chornedsnorkack: You mean silicate recovery, as suggested first in the post? The calcium silicates formed during the firing of the bricks are impregnated with silica (that one) and other silicates (aluminum, magnesium, iron possibly, sodium perhaps), not to mention alumino silicates and whatnot.

Same problems again, mate.

I was referring to "silicate bricks". Apparently go by some other names like "sand-lime brick". A popular building material - available cheaply new made, and even cheaper/the recycling moment as building waste and demolition/repair waste.
In contrast to cement concrete (which intentionally includes alumosilicates) and ceramic bricks (intentionally of alumosilicate clay), silicate bricks exclude aluminum from both lime and sand.
The one likely impurity is excess sand.
Quote: Originally posted by bnull  

Quote:

You can't separate them physically because the particles or whatever are very small, well mixed and in the solid state. They don't melt without decomposing and they're also insoluble. You can't separate them chemically without destroying them.


To long, didn't read: If you want calcium silicate, buy it. If you have a furnace, make it from sand and lime.

A classic review:
https://nvlpubs.nist.gov/nistpubs/nbstechnologic/nbstechnolo...
Unlike ceramic bricks, silicate bricks cannot be made by kiln. They require autoclave.

bnull - 13-3-2024 at 15:57

Quote: Originally posted by chornedsnorkack  

I was referring to "silicate bricks". Apparently go by some other names like "sand-lime brick". A popular building material - available cheaply new made, and even cheaper/the recycling moment as building waste and demolition/repair waste.
In contrast to cement concrete (which intentionally includes alumosilicates) and ceramic bricks (intentionally of alumosilicate clay), silicate bricks exclude aluminum from both lime and sand.
The one likely impurity is excess sand.

I know, they're also advertised as calcium-silicate bricks. Sand has not a fixed composition, it's mostly silica plus calcium carbonate and silicates, the proportions vary according to the geology of the area. The presence of aluminum in some is unavoidable; there is feldspar, for example. Or thorium, as in the monazite sands in India and Brazil.

Suppose you have a brick factory. Would you try to purifiy the sand before making the bricks? No, it costs money, you just clean it enough to remove organic material and some other things (free metals, for example), and on with it to the mixer. Maybe even add crushed flint or other silicate rock to it. The end product is basically the starting material (sand and silicates) with calcium silicate as binder and some calcium hydroxide (which becomes carbonate as the brick ages). Even so, you can't separate calcium silicate physically or chemically--without decomposing the silicate--from the rest.
Quote: Originally posted by chornedsnorkack  

Unlike ceramic bricks, silicate bricks cannot be made by kiln. They require autoclave.

I wrote, "If you want calcium silicate, buy it. If you have a furnace, make it [calcium silicate, not silicate bricks] from sand and lime." It was the suggestion offered by @Admagistr. That's why you needed a furnace, the reaction runs above 1400 °C.

nikotyna1939 - 14-3-2024 at 00:52

I needed Calcium Silicate for high quality small scale metal furnace insulation.
With starting from scratch

[Edited on 14-3-2024 by nikotyna1939]

bnull - 14-3-2024 at 05:36

Why didn't you say it before? I thought you needed it for some reaction or for rice farming. The refractory properties never crossed my mind.

Did you search the forum? There are some threads about refractory compositions not necessarily based in calcium silicate.

There was also this guy. The last time his website was updated was in 2018, so I don't know what happened to him, if he's still melting and casting, or even breathing. Take a good look around.

Or you can buy the refractory cement, either local or from China (you're in Indonesia, right?). I know it's out of the 3R philosophy and you'd rather make your own composition, but it's an option. It saves time.

Reacting calcium hydroxide and silica

nikotyna1939 - 14-3-2024 at 06:47

At what temprerature will Calcium Hydroxide and Silica reacts to produce Calcium Silicate ?



[Edited on 14-3-2024 by nikotyna1939]

clearly_not_atara - 14-3-2024 at 07:47

Quote: Originally posted by nikotyna1939  
I don't just buy calcium silicate because in my area you need to buy calcium silicate in bulk quantity like 100 kg to get a reasonable price.

also i needed only about 10 kg only.


Are you searching for "calcium silicate" or are you searching for "wollastonite"? Most small-scale vendors will use the latter term. Probably due to a bias against "chemicals" among consumers. Eg:

https://customhydronutrients.com/Wollastonite-natural-calciu...

bnull - 14-3-2024 at 08:52

Quote: Originally posted by nikotyna1939  
At what temprerature will Calcium Hydroxide and Silica reacts to produce Calcium Silicate ?

Well...
Quote: Originally posted by Admagistr  
Truly pure calcium silicate of solid composition can be obtained by fusing a stoichiometric mixture of SiO2 and CaCO3 (CaO) at high temperatures, just over 1400 C.

Both calcium carbonate and hydroxide decompose to CaO at about 1000 °C. You will need a furnace.

[Edited on 14-3-2024 by bnull]

Admagistr - 14-3-2024 at 09:49

You can use a furnace like this, you can also buy a lower volume version which is cheaper:
https://uk.vevor.com/melting-furnace-c_11137/vevor-6kg-propa...
But, for the chemical reaction to proceed quickly, it is best to have a temperature about 100 C to 200 C higher than a little over 1400 C. Over 1500 C to 1600 C. For this, one could use a coke thermally isolated from the surroundings and an air stream obtained by a blower.

using a blowtorch to produce calcium siilicate from calcium oxide and silica on a small scale?

nikotyna1939 - 16-3-2024 at 07:39

would 1800 degree celsius blowtorch sufficient to make about 5-10 gram of calcium silicate from calcium oxide and silica on a small scale?

Admagistr - 16-3-2024 at 08:12

Quote: Originally posted by nikotyna1939  
would 1800 degree celsius blowtorch sufficient to make about 5-10 gram of calcium silicate from calcium oxide and silica on a small scale?


Yes! This is the ideal temperature for a fast and smooth reaction. The temperature can be slightly higher, that's not a problem, it's a good insurance that the whole mixture will react. The problem would be if it was a few hundred degrees short of a successful reaction. And exactly what kind of burner do you have? Can you post a picture or a link;)? I don't have an 1800 C burner, I have an autogenous burner that can pull the temperature up to just over 3000 C, ideally.

j_sum1 - 17-3-2024 at 01:44

After reading this thread, it all boils down to one question.
Why?

You have a supply of something rock-like and inert which is an admixture of dozens of different minerals.
And you want to use a ton of expensive reagents to make something sand-like and inert and maybe pure but not really useful. And this product is literally dirt cheap to buy.

I am sure there is something I am not getting here.

bnull - 17-3-2024 at 11:59

At least it is not like those pearls in Detritus, as "alcohol reduction by living fish gills", or "have you tried extracting amine from bodily fluids".

Precipitates - 17-3-2024 at 22:48

The less said about them, the better.

theoretical repursposing

nikotyna1939 - 18-3-2024 at 02:20

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]

bnull - 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]

Calcium chloride + silica= product ?

nikotyna1939 - 18-3-2024 at 02:34

what is the main product of reacting Calcium chloride + silica at room tempreature in water ?

very useful products

nikotyna1939 - 18-3-2024 at 02:37

i meant other very high valued useful products for recycling

bnull - 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]

Admagistr - 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;)

Preparation of Calcium Silicate from Calcium Chloride and Silica ?

nikotyna1939 - 19-3-2024 at 21:41

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]

Admagistr - 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.

Admagistr - 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...

temperature for preparing calcium silicate from calcium chloride and silica?

nikotyna1939 - 19-3-2024 at 22:59

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]

Precipitates - 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).

Precipitates - 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...

bnull - 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.

Admagistr - 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:)!