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Post by hfosteriii on Feb 1, 2020 12:05:29 GMT -8
Considering the current formulations (that I have read) require keeping water to a minimum in geopolymer mixtures, could someone explain to me the cons (possible pros?) of adding foam (like foamcrete) to produce a lighter weight final product with increased insulative properties and would maximize material usage .
Considering the foam would be alkaline based the only change I can see would be the addition of moisture (chemically, molecularly) and air (as an additional aggregate).
Would the entrainment of air as aggregate and the increase in moisture reduce the chemical bind significantly enough to reduce strength of the finished product to a impractical/ unstable/ unusable point?
Would the addition of foam reduce surface area of bonding to make it structurally weak for any use?
Please answer with an in depth chemical/ molecular explanation, both to satisfy my own quest for knowledge and for others to reference.
Thanks in advance.
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Post by Vortex on Feb 1, 2020 15:05:02 GMT -8
That's a really good question. I've been wondering that myself for some time. I'm interested to see what Karl has to say on the subject.
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Post by hfosteriii on Feb 1, 2020 20:10:27 GMT -8
I was hoping that he would see it and be able to answer as best he can. I've never posted hear but I reference this forum quite often (for over ten years on RMHs) and read a bunch of Karl's posts and the paper on geoplymers and other stuff he has linked. I just stumbled onto it while looking into cheaper (or alternatives to) calcium aluminate mixes.
I always appreciate any one's thoughtful input, but he does seem to be the most likely one to ask.
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Post by Deleted on Feb 2, 2020 8:51:35 GMT -8
Reducing density inevitably also reduces resistance against acting forces, with resistance to cracking as the virtually only possible exception. Clay based geopolymers have already a relatively low density by nature, due to the required relatively high water content.
The outcome of blowing agents is hard to control. Lots of tests and very precise formulas required.
Pre-foamed foams are better controllable. Additional foaming equipment required.
Virtually all foams require accelerators to prevent the foam from collapsing before hardening.
Pseudo foams with hollow microspheres are very simple to make, just mix the microspheres into the geopolymer. Cenospheres, borosilicate glass microspheres, poraver expanded glass or even polymer microspheres can be used. To prevent segregation by gravity the use of an accelerator may be required as well. Mineral microspheres have a density of about 200g per liter.
Pseudo foam geopolymers made from grog can be light weight and still have a relatively high strength. I hve sent samples of Pseudo foam geopolymers and others to esbjornaneer |
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Post by hfosteriii on Feb 3, 2020 2:06:29 GMT -8
Thank you for the info Karl.
I figured due to the fast setting nature of these geopolymers (it seems as though it's always fairly quick, especially with medium to high alumina content) that a generated foam as used in foamcrete would hold as well as it would in a portland mix. I am making a foam generator (for many reasons and uses, most importantly because I want to lol); as soon as that is completed and I try a few tests runs of geopolymer recipes, I'll start experimenting with foam. Any suggestions? Especially in areas of water content?
Secondly, would a sodium hydroxide/ fireclay mix be appropriate for the binder. I couldn't find anyone using it in the forums (only zeolite) even though the papers and posts have indicated it's use. If so what would be percentages?
Thirdly, I'm still unclear as to ratios to use (after the binder is prepped) and if I was using a foam, would a fireclay/calcium aluminate refractory be suitable, in place of grog, firebrick, earth, etc., to be used with the foam? Or will this all be experimental? I just don't know what ratio to start from, to save some time.
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Post by Deleted on Feb 3, 2020 9:58:37 GMT -8
Which densities to you want to achive ? Densities down to about 1.5 Kg/ liter can be achived without foam.
Which materials can you get at your place? The United States, where capitalism clearly is not working, actually have obscene prices.
Which kind of minerals do you want to synthesize?
The higher the alumina content the higher the thermal resistance,the lower the thermal conductivity, the more brittle.
Researchgate has lots of papers.
High strength metakaolin-based geopolymer foams with variable macroporous structure
Low-temperature fabrication of SiC/geopolymer cellular composites
THERMAL CONDUCTIVITY OF REINFORCED GEOPOLYMER FOAMS
Metakaolin Geopolymer Foam Using Aluminium Powder
Fire Resistance of Alkali Activated Geopolymer Foams Produced from Metakaolin and Na2O2 |
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