What are the best characterization methods to know if you have geopolymers or just alkali-activated material? Finally, could you recommend a good reference showing the differences to share with some colleagues?
Hi Ahmed again,
I have just answered to your message.
Anyway, between AAM and GP technologies there are different raw materials, different reactions, different pH of the systems (AAM strong alkaline in corrosive user hostile conditions, while GP can be obtained in lower pH so user friendly and not corrosive ambient with specific molar ratio, for the alkaline GP and also in acidic medium using phosphate acid with precise molar Ratio), different mix design and different mixing methods. So definitely GP aren’t AAM or a subset of them. Geopolymers as Davidovits coined the name are mineral (geo means geological sources) polymers (not an hydraulic or aerial material that increase it volume from a starting powder that reacts with water. Not the result of a precipitation too). AAM instead follows a hydraulic process where the powder selected as precursor must be activated because not perfectly reactive by itself so the Binder of the system is the liquid composed by water and strong concentration of alkalis with pH even 14+. Consequently the material used as precursor is dissolved in a chaotic mud that precipitates and after drying by air the material is hardened without containing any mineral polymer, but only hydrates CSH-like called by AAM scientists KASH and NASH. It’s OPC like reaction but less stable in water because Calcium of CSH is insoluble, while sodium or potassium are very soluble in water. In these minerals H is water because these crystals are water based. Inside GP there isn’t any KASH or NASH because the newborn minerals, family of feldspar rocks, are still amorphous after hardening and for prolonged time before crystallizing (durability, acid resistance, water immersion resistance, fireproofing properties and so on).
The characterization of a technology or other starts with the selection of: raw materials, mix design and the knowledge about the fundamentals of geo-chemistry necessary to understand why selecting what. I cannot teach you how to do because my NDA, I hope you will understand, but the book of Davidovits can be super useful to start if you select the GP process. Find that book at www.geopolymer.org
For AAM I think there are more than a study done from Glukovsky to nowadays that could be used if you select that approach.
The essential is to not misunderstand the systems just because they could be obtained in alkaline medium (pH scale is logarithmic so there is lot of difference in terms of alkalinity rising till 14, GP are organized structures cannot be formed if the starting ambient is too much caustic). Even Portland and limes are alkaline but aren’t absolutely the same and all people knows.
As fast checks if you still don’t know what could have done in your testing: 10’-15’ boiling test (immediately after demoulding) GP = polymers remain untouched, AAM expands or shrink losing material till failing. Water immersion curing for 28 days (put in water after the demoulding) and check the mechanical strength in comparison with air curing samples (acceptable difference from 0 to 25% from air due to the lack of capturing CO2). GP normally are inside this range, AAM usually fail before the end of the curing or if resist lose more than 50 to 90% of the strength had by air, so aren’t stable.
Write me if you need other informations.
Best
Alex Reggiani
Article Properties of alkali-activated slag mortar and prediction of...
This paper will definitely answer your questions
I went quickly through the paper. It seems it does not show any clarification about the difference between AAM and geopolymers.
Ibrahim Zidan I can see in the article just a characterization of AAS with no comparison with GP alternative or suggestions about how to recognize that a system is GP so polymeric or Alkali Activated so hydraulic 🤷🏻♂️. I think Ahmed Abdelaal asked about how to distinguish and which test should be done to understand better where each system works and where it doesn’t work (maybe understanding why).
Best regards
Dr. Alex Reggiani
CTO GeoMITS
Hi Dr. Alex Reggiani
I read your paper related to geopolymer cement. You explained that the way to make the GP Cement is by mixing the precursor and reagent, metakaolin and potassium silicate, then adding the aggregates after some time.
I have industrial waste and I plan to employ this material in GP Cement. Should I follow the procedures you did by mixing the reagent and precursor at the initial step, and then adding the waste material after several minutes?
Also, is there any assessment that should be conducted to know the materials/aggregates that can be added to GP Cement? And what is the material characteristic that can be added to GP Cement? Thank you.
Hi Idham Kholid Rahmatullah ,
technically speaking the Geopolymer cement that I suggested to use in the paper you are talking, was simply the Metakaolin itself. This because Geopolymer cement and precursor are the same thing.
About your specific case you need to know the amorphous content, the mineralogy (plus its chemistry) and the particles size distribution of the “waste” that you are considering to use. Depending on its reactivity lot of things can be done.
I’m not an academic, I cannot explain precisely here. Please write me an email at [email protected] and I will explain how GeoMITS could help you.
All the best
Alex
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