Dear Elsayed,

Geopolymer technology isn’t the same that Alkali activation technology.

Organic additives don‘t work for Geopolymer materials, you can more easily retard managing the recipe of Geopolymer binder.

If you are using Alkali activated materials instead, all can depend on what raw materials have selected to use normally : slag , fly ash type C, or what? Activator is necessary for Alkali activated materials, not for Geopolymer materials where what has been activated (only by calcining ) is the precursor in powder , that is amorphous and super reactive because its mineralogy. The liquid part used is called “hardener or reagent “ and isn’t too strong alkaline silicate in comparison to the activator you use for Alkali activated recipes.

So without more information about what raw materials are in your system and what alkaline reagent are using it isn’t possible to suggest you something.

Check at www.geopolymer.org , the site of Geopolymer Institute all informations about “why alkali activated materials aren’t Geopolymers “ will find there 4 videos and dedicated scientific paper that explain technically all reasons.

Please have a look and after try to use correct terminology or you risk to do mistakes and your work never will be good.

About the difference from AAM and Geopolymers there is a simple and fast testing that you can do to understand if your product is one type or other: after demolding , usually after 24h, put one sample in water for 27 days. If sample in water resists till 28days , you will test about mechanical resistance and will compare to air cured one.

For genuine geopolymer mortars and concrete water curing doesn’t create problems and strength development is comparable to air (some variations can be find in the order of more or less 10 to 15-20%, depending on precursor used. This because Geopolymers are Carbon negative so in water you can have carbonation at the same rate of development than by air, so you can lose something). Specially because alkaline ions in your case potassium are engaged inside new minerals formed by geopolymerization process , so aren’t soluble in water. For AAM instead you have to use stronger pH (corrosive, while Geopolymers are only irritant , like Portland cement) so bigger amount of alkalis that aren’t involved in polymerization that creates new minerals but work like binding glue , still easy soluble in water, so mechanical strength development is seriously damaged and reduced. AAM are hydraulic systems while Geopolymers are non hydraulic ones (are familiar the acronyms KASH or NASH? H means hydrate , so crystalline water inside minerals , very similar to Portland cement technology, but about 10 times more unstable because leaching). At the end usually AAM have big problems to arrive at the end of curing in water or if they resist , the lose the most part of strength (more than 50%, to 70-80%) and the worst is that there isn’t a rule about this leaching so if you repeat the same test maybe you can observe sometime higher losing or other time little lower. Instability i never good property for building material .

Last thing , when you talk about that you used Alkali activator potassium based , you really say nothing . The key Factor to be checked is what is your liquid (I don’t need your formula of course) , but in these terms: is it a silicate or KOH or blend of them ? What is pH that you are using?

I’m sorry for the long speech but to be helped you should give more informations, even about what retard do you need and what are your hardening timings now.

All the best

Alex Reggiani

Thanks so much

The raw material is rock-based geopolymer(normalized natural rock)

The hardener is a blend of Potassium silicate and potassium hydroxide

So what do you recommend to use?.@Alex Reggiani

Dear Elsayed,

I’m sorry but what rock are you using ? granite, felspar, basalt , volcanic tuff these are all rocks but I’m geologist so I know their mineralogy and I know that they can work well or not depending on quality, size and amount.

If you need more write me an email, I’m working as CTO for 2 companies about Geopolymer technology (GeoMITS in Italy where I live and Renca Rus in Russia ) and I have NDA too but maybe I can give you suggestions to solve your problem.

Let me know the pH of your liquid because probably that is the problem.

Regards

Alex

I will try it.Thanks@Elijah Adesanya

Also lignosulfonate might work. It also acts as a superplasticizer.

However, precursor, alkali activator, and mix design affect the suitability of superplasticizers.

See:

Article Suitability of commercial superplasticizers for one-part alk...

Many of these mentioned superplasticizers are based on complexation of for example calcium or magnesium in terms of chemistry.

thanks for your recommendations, I will try when I could back to work@Tero Lukkonen@Faris Matalkah

Sugar is used as retarder for concrete mixes, it can have sense to try it on your system.

You can find more about its influence on this paper. Conference Paper Effect of Sugar on Setting-Time and Compressive Strength of Concrete