Cheaper and user friendlier Geopolymerization Agents

[sksshel]

What is the recommended curing process for the end product?

[Deleted]

Chemistry works best if warm.

[sksshel]

Jan 15, 2018 17:25:05 GMT -8 @karl said:

Chemistry works best if warm.

So, 80 - 100 degree F?   For how long?

[Deleted]

Until it got hard.

[sksshel]

Observations from my 1st test:
- mixing the citric acid and the monopotassium phosphate caused no visible reaction (2 acids mixed)
- adding the Soda ash caused an immediate reaction in terms of bubbles, volume and gas (a base mixed with 2 acids)
- this was done at room temperature
- by the time I got the mixture up to near boiling temperatures, I could no longer detect any further reaction. This was much faster than I anticipated. POINT 1
- I continued heating until I got the mixture to boil and then backed off the temp. There continued to be bubbles from the bottom of the container which appeared to me to be an indication of "near boiling" rather than a further chemical reaction. POINT 2
- I could not detect any chemical reaction after point 2.

Questions:
Was the process complete at Point 1?

Should I heat the citric acid and monopotassium phosphate mixture prior to adding the soda ash?

[sksshel]

Approximately how long will it take to cure the product in an oven at 80 degrees? The puck is 1" thick by about 4" diameter.

1 hour, 2 hours, 2 days, 2 weeks, 2 months, 2 years?

[Deleted]

I thought it would be obvious from my description that first the soda ash should be mixed with the monopotassium phosphate
and when the reaction of both comes to a halt it should either be heated to near the boiling point or some citric acid should be added.

27°C/80°F are only slightly above ambient temperatures (20-25°C).
Curing time with some caustic lime or cement should be less than a week.

[sksshel]

I did, in fact, my first attempt (not posted) mixed the soda ash and the monopotassium phosphate first. However, they are both in powder form. From your response, I assume I should have added some water to promote the reaction. I incorrectly assumed that the liquid was provided by the acidic acid.

I probably shouldn't have slept through my high school chemistry class

[sksshel]

Jan 23, 2018 10:55:07 GMT -8 @karl said:

I thought it would be obvious from my description that first the soda ash should be mixed with the monopotassium phosphate
and when the reaction of both comes to a halt it should either be heated to near the boiling point or some citric acid should be added.

27°C/80°F are only slightly above ambient temperatures (20-25°C).
Curing time with some caustic lime or cement should be less than a week.

Is this a sound process?

Procedure:



- Bring the water to a boil


- Dissolve the monopotassium phosphate in ½ of the water


- Dissolve the Soda ash with the remaining in ½ of the water


- Mix the 2 dissolved solutions together. This causes a reaction to drive the carbon out. Look for No new bubbles on the surface, no fizzing sound, no volume increase. This should conclude within a few minutes.


- When the reaction comes to a halt, heat to near the boiling point


- Add the citric acid. Wait until the reaction comes to a halt. This should conclude within a few minutes.


- Add Rockwool, Portland Cement and Clay


- Let the end product cure until hard. 27°C/80°F is only slightly above ambient temperatures (20-25°C). Curing time with some caustic lime or cement should be less than a week.

[Deleted]

Needlessly complicated.

Just mix the powders and then add the hot water.
This allows to keep the concentration high.
The reaction releases some water and causes an immediate mass loss.

Sodium carbonate solubility ~ 217g per liter at 20°C
Monopotassium phosphate solubility ~ 222g per liter at 20°C

Reaction products:
Na2CO3 + KH2PO4 = Na2KPO4 + CO2 + H2O

Another possibility
Na2CO3 dissociates in water to NaHCO3 + Na+ and OH-
3KH2PO4 + 4NaHCO3 = K3PO4 + 2Na2HPO4 + 4CO2 + 4H2O

One needs less water in this way.

[sksshel]

6 days after I mixed 4 samples:

I cured them inside a black tote placed on its side in a window area with the daytime sun.  The daytime temperatures were 100+ degrees F on sunny days. 

I have removed all of them from their form.  All but 1 of them (sample 1) are dry to the touch.  All of them are reasonably hard.  Sample 1 is lagging behind in all categories.  All 4 samples are 1 3/4" thick. 

I have observed no cracking.   They all poured nicely into the molds and easily settled when shaken. 

I did make one other additional sample 1/2" thick.  It seems to have good strength. 

I am leaning towards using Formula 4 for my project.  I plan to do more testing of the products before I make the final decision.  Tests will include heat, water, and strength.  I also plan to saw the samples in 2.   I plan to allow them to cure 1 more week before completing the testing. 

All of the tests produced roughly the same product volume.  16.84 cubic inches or .276 liters.  3.6 times the formula makes 1 liter.   102.4 times the formula makes 1 cubic foot.   6 cubic feet of the product will cost approximately $250.  

Formula 4                                    Grams

monopotassium phosphate     9%     29
Soda ash                              7%     26

Water                                   2%     4 ounces

citric acid                              2%     4 ounces
portland cement                   18%    59
clay                                     59%  200
fiber                                      3%    10

[sksshel]

Updated Procedure:



- Mix the monopotassium phosphate and Soda ash powders

- Add boiling water This causes a reaction to drive the carbon out. Look for No new bubbles on the surface, no fizzing sound, no volume increase. This should conclude within a few minutes.

- Add the citric acid. Wait until the reaction comes to a halt. This should conclude within a few minutes.

- Add Rockwool, Portland Cement and Clay

- Let the end product cure until hard. 27°C/80°F are only slightly above ambient temperatures (20-25°C). Curing time with some caustic lime or cement should be less than a week.

[sksshel]

From what I've been able to find on the subject, true geopolymers are:

Geopolymer (Polysialates)

(Na₂O - Al₂O₃ - 4SiO₂ - 11H₂0)


1 - 1 - 4    -   1 Oxide - 1 Alumina - 4 Silica



Roughly twice the strength of Cement

Half as dense


Example clay mixture:

10% monopotassium phosphate K H₂ P O₄

8% Soda ash Na₂CO₃

2% citric acid C₆H₈O₇

2% water

18% portland cement CaO SiO₂ Al₂O₃ Fe₂O₃ SO₃

67% clay Al₂Si₂O₅(OH)₄

3% rock wool


I am way out over my skis in the area of chemistry.   I'm putting all this out here to learn more about the process.  I hope I'm at least close to accurate with what I've listed above.  I also want to be clear about whether the end product is a "true geopolymer" or something else.  I just want to know.   

I really, really wish I had payed more attention in my high school chemistry class.   
 

[sksshel]

Would it be helpful to the overall strength to add more rock wool? How much more?

[Deleted]

In the periodic table silicon is in column 14 one row below of carbon.
Both have 4 valence electrons whose exerted force is determined by the atomic radius.
Which gives both the ability to form large molecule or macromolecule composed of many repeated subunits,
which is by definition the property of a polymer.

Carbon: Polymer
Silicon: Geopolymer

The chemicals are mere means to create the required conditions for the formation of large molecule of which they are also participants.

Fibers cannot contribute to overall strength, but only to bending strenth.
Just test it.