Try to add chemical admixture which can delay setting time.

Or u can try ....to add sugar or sucrose

Hello, happy to hear that you are working on Geopolymer concrete. Normal PCE admixtures wont give satisfactory workability requirements, try new generation dispersants. I think MBCC People come up with new dispersants which fits for workability requirements

Thans for the resposne.

Maybe you can increase the setting time by addig OPC. It worked on my metakaolin-based geopolymer products.

Attila Baranyi

Thank you sir.

Dear Tipraj,

first of all you have to decide which technology you want to use.

Geopolymerization isn’t alkali activation so you are misunderstanding some fundamentals to work correctly. GP is mineral polymer while AAM is still an hydraulic process closer to Portland cement reaction, but very less resistant under water immersion.

GGBS isn’t the best precursor for geopolymerization because its lack of alumina, but of course can be used ONLY if you change raw material as main precursor source. Using 100% blast furnace slag as precursor is the main mistake. Never you could obtain a true GP.

Flash setting is generated by the immediate precipitation of calcium and magnesium minerals (CSH also) when you try to mix. The reagent or should be better to name activator , because you are doing 100% an AAM, is very alkaline so precipitation is quick.

Being AAM you can use the same retarders used for Portland cement so citric acid, tartaric acid mainly. But the dosages can be significantly higher than OPC recipes, because the high alkalinity is more efficient as accelerator than the retarders. Other practical trick can be to refrigerate both reactive parts (powder and liquid) to delay the starting of the reaction.

Sucrose can also be used but it will destroy more the strength development.

If you want to do a real Geopolymer I suggest you to select better the raw materials for the precursor and to use a user friendly silicate (less alkaline) for the reagent. Too high pH isn’t necessary and high amount of Hydroxide promotes efflorescence due over saturation.

Also mixing method is completely different from GP and AAM because for GP you need to prepare at best before your binder adding the mineral charge in second moment properly like happens for organic resin products. AAM is mixed all together because there aren’t mineral polymers that need special mixing so finally the material is more unstable (efflorescence, leaching and blooming are normal consequences of AAM process).

Extra water and curing are also treated differently between AAM and GP.

Of course using slag you can work at room temperature even with AAM but you have flash setting, probably efflorescence and great losing of strength in water (due to leaching). While all GP materials harden under room temperature, have balanced binders avoiding or reducing efflorescence at best and are stable not only under water, but they can resist at boiling water test.

There’s too man things to check, my suggest is to start knowing better the field you want to explore and then you will follow the best way to obtain your goals.

Best regards

Alex Reggiani

Dear Thambi

I have read an article on the recovery of calcium sulphate from solid waste generated during the zinc process.

In general Zinc/Zinc sulphate is used in Agriculture.

My suggestion is to add some(assumed) percentage of zinc in the matrix and find the behavior, ie setting time- increased or not.

If there is an increase in setting time observed, then try the trial and error method to establish the optimum utilization of zinc in GP Concrete.

best wishes

Dear Tipraj,

Which type of concrete you use.

If you use normal concrete and don't attention about the high strength , maybe you can use natural river aggregate (i.e. not the crushed one), becuse it is not important in the conventional concrete in terms of the surface texture.

On the other hand, If the high strength of concrete is important, maybe you can use a suitable fine aggregates which will be inherently lesser consumption of water in the mixture such as (cooper slag as fine aggregate) and should has a higher finenus modules as well.