I am trying to perform a screening DoE to further study influence of a range of factors for example Metakaolin content on various performances like compression strength and to further optimise my formulation in a next step.
Therefore I need to set the ranges for every factor which obviously has to be done in consideration of the chemical processes. To ensure that still a geopolymerisation process will be performed after changing many factors in high amounts because of the DoE protocol my plan is to set the ranges according to what are assumed to be the mini and maximal ratios to perform geopolymerisation.
It is stated in many papers and books in which direction increasing or decreasing ratios will change specific performances but I couldn't find the needed mini and maxima values.
I am very thankfull for every answer, hint or research paper you could give or recommend respectively.
some permissible ranges in works of literature, in addition other molding and curing conditions can be determining factors. watch this work: Potential use of ceramic waste as precursor in the geopolymerization reaction for the production of ceramic roof tiles
In my research, the best SiO2/Na2O molar ratio was around 2.0. Good compressive strength was within range of 1.5 - 2.5. I used fly ash as raw material and NaOH solution as activator. I also considered amount of alkalis in the the fly ash and recalculates into NaO2 equivalent.
Dear Vytautas,
what are you asking about isn’t so mathematical for Geopolymer technology maybe you are confusing with alkali activated materials.
For AAM you have an activator very caustic and dangerous (for you user that must be used with very care) like NaOH that dissolves all fly ash (which type ? For AAM both are good , while for Geopolymers only F class) and finally you have a random condensation without any polymerization of minerals but with Na ions that keep all together ...by air or in oven. But when you put in water after demolding (after 24h?) these ions , easily leached out because still soluble and your material will strongly reduce its strength after 27 days of water curing or fail before finishing the maturation . If you compare mechanical properties by air and after this water curing (the same that usually you should do for Portland cement samples) will find very different and every mixes will lose differently.
Geopolymers are different technology there isn’t minimum or maximum but specific ratios that depends on precursors that you are using (the amorphous powder rich in silicon aluminates, like fly ash class F , for your research) , considering its shape, size (also distribution) and calcining temperature (under 1300°C fly ash F, are low reactive due to bad mineralogy , while over this limit free C and free S are reduced at best and reactive glass minerals are well generated) . By the way fly ash F in Geopolymer pH isn’t dissolved totally, reaction is only on surface , you can see the glass spheres in the hardened material with SEM and the alkali ions are inside the new generated minerals based on 3D network, starting from oligomers to more complexed mineral polymers. I suggest to participate at next Geopolymer Camp from 6 to 8 th of July in France to understand better what I’m saying. Professor Davidovits explains at best all the reactions that occur during the process.
This technology must follow some important rules and also mix design is very specific and completely different from AAM and Portland cement products that more or less are mixed in the same way.
Find more details on geopolymer.org , there is s section dedicated to GP Camp 2020.
Hoping to be useful
Best regards
Alex Reggiani
- Badges
- Science topic
- Similar topics
- Books