Hello every one,
For mixing the geopolymer concrete, we need to use sodium silicate solution, but it is sticky and hard to handle, which makes the mixture hard. The method that I used to make geopolymer concrete was mixing my sodium silicate solution (which is sticky) with NaOH solution and then after a little bit blending by hand putting it into the mixture to manufacture the geopolymer concrete.
I recently saw a video suggesting mixing sodium silicate solution (in solution, not flakes) with water and then putting it into a blender to rotate for a while, 3 hours. After 3 hours of rotating, the mixture becomes as soft as water, and then we can use it in geopolymer concrete very easily.
I want to ask which method do you use?
The vide link:
1) this shows how to make the SS soft: https://www.youtube.com/watch?v=s3R75HdaGBg&t=295s
2) this video shows how to use it when mixing concrete. You see it is soft as water (see minute 6:20): https://www.youtube.com/watch?v=8PhN3S2dK9M&t=299s
Hello Armin ,
I saw both videos ,the methode to make SS soft take a lot of time 3 hours because it's can't to change the temperature and can't do it faster, the second video use SS as a concrete, water the results is good
Hi Armin
I believe you need to improve the mixing process.
You need to mix your precursor powder and your alkaline reagent in a mixer (you must use very reactive alumino-silicate precursors and a reagent with the correct molar ratios). Allow this process to last for about 10 min in order to be sure that a good geopolymerization reaction takes place. At the end you will have a much fluider binder just by mixing. Now you can add your aggregate.
I hope I have helped you
FV
Hi Armin,
about the first video, every silicates manufacturer can manage the fluidity of every sodium based silicate adding water inside an autoclave. In this way results are more stable and durable because obtained using the best temperature and pressure. Molar ratio must be checked because it seems too much the water added, but of course all parameters depend on the final application, where will be used.
First of all you should understand what is geopolymerization and what instead is alkali activation. The mix design of Geopolymers (GP) is different from Alkali Activated Materials (AAM), because GP are mineral polymers while AAM are still hydraulic materials. Francesco Volpintesta explained quite well how should be done for GP concrete.
In the second video I can see the typical AAM mixing, for sure not a Geopolymer.
Cannot exist geopolymerization reaction if you mix like Portland concrete. Geopolymerization needs to follow correct method.
You don’t need a silicate fluid like the water to have a good GP concrete but you need a well balanced GP binder (precursor and reagent), that’s already enough fluid, stable and thanks to the good curve of aggregates that you are using, you will be able to manage the consistency adding just few % of extra water (that works like fluidizer but without reducing the GP content ).
GP concrete is stable system also under water immersion, immediately after demolding and after 28days shows comparable strength than samples cured by air at room temperature.
That AAM concrete instead, specially if mixed in that way, usually shows even good strength if cured by air. But if put in water suffers about leaching with possible failure within 14 days or even if resist till 28days, its strength will be very lower than the sample air cured. In case of humidity efflorescence can be other issue because of AAM reaction is quite unstable and alkaline ions are over saturated.
To check my words try to do several batches with the same recipe, I think you will find every time different results and don’t forget to check the water curing, because if you want to develop an alternative to Portland cement materials you must be competitive on its best “field “ .
Hoping to be useful for your future work.
Best Regards
Alex Reggiani
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