Post by firewatcher on Sept 2, 2016 12:25:25 GMT -8
Sorry Karl...you already provided the info (as I remembered)...i couldn't find it while rereading the posts on my phone. I switched to the old PC to reread the thread and found the recipes that you had shared right away. I'm hoping to try out a couple of new test pucks tomorrow once I've "activated" some bentonite.
You could improve the mixture a lot by dissolving a few gram of aluminium in lye and adding the solution to the mixture. About 5% by weight of the bentonite. Bentonite does only contain small amounts of alumina.
I have mixed 60g bentonite with 30g of either zeolite, feldspar or clay, then acid activated the mixtures with each 5g citric acid. Later I have added powdered waterglass, lye and 300g slag sand and mixed all with waterglass and finally the usual amount of cement. All three mixtures worked well and were faster to cure and dry than the mixture with 100g pure acid activated bentonite. Resulting dry densities around 1.4.
The logical next step is acid activation of other clays.
Ball clays have the smallest particle size and the particles of kaolin may be larger than the definition of clay says.
I have made two mixtures for acid preactivation, each 95g clay and five gram citric acid. The clays Ball-Clay Hymod Prima and China Clay Grolleg. Other clays have much smaller internal surfaces than bentonite. thus there is less area where the acid can attack. To give the acid attack more power I have heated the slurries to 100°C for two hours and let them rest for some more hours.
Later I have mixed the activated slurries with each 300g slag sand, powdered and liquid waterglas and the usual amounts of lye and cement and let them cure over night at ambient temperatures. Both mixtures got solid.
It would be nice if someone with clay soil nearby could try to preactivate it and give a report.
Both mixtures got very hard and a bit denser than the mixtures with various amounts of bentonite. China clay has the lowest water demand and thus the mixture with it got denser than the ball clay mixture. A third mixture with very cheap white clay activated with the cheapest vinegar at the local supermarket, got solid too.
Post by firewatcher on Sept 6, 2016 4:03:31 GMT -8
I cast a puck and a "brick" with an acid activated bentonite recipe loosely based on your first recipe as far as the amount of slag used. I forgot to add any accelerator though...it may take a while before i can report back my results due to long drying time.
I was finally able to "camp fire cure" a couple of my other test pucks last night too. I'll share my results later this evening when I'm able to take some pictures (in the geopolymer thread though...as they were not acid activated pucks).
Matt, mix 100g dry clay with ordinary vinegar to a thick slurry, which would only flow under vibration. Heat the slurry to 100°C for at least one hour, then let it cool down. Mix 10g lye flakes with the slurry and let it rest a bit. Then mix the slurry with waterglass and 300g sand or only another 100g untreated dry clay to a thick but under vibration flowable slurry. At the very end add 10g cement or lime as an accelerator and mix all well. Cast the slurry and seal it in a plastic bag and let it cure under ambient conditions for a week or at 50°C for at least five hours. If mixed without sand it needs more care. The mixture should have become solid but still not got very hard. Then it can be slowly dried.
With commercial waterglass the solid waterglass content will be a bit low but should be sufficient. The DIY Waterglass from "Geopolymer For Low-Tech Tinkerer" is much more concentrated. You can adjust the amount of lye and silica gel for a smaller amount of liquid waterglass.
The mixture can be made flowable without vibration, but with more liquid more care is needed for curing and drying.
Last Edit: Sept 6, 2016 14:41:08 GMT -8 by Deleted
Post by matthewwalker on Sept 6, 2016 19:28:47 GMT -8
I'll see if I can put it together. If I'm using found clay, it will probably be wet. I'll worry about that when I get there I suppose. Thank you for the simple steps. I'll keep you posted on any progress.
The weight of wet formable clay is about 125%-130% of dry clay. About 5% organic acid by dry mass of the clay are needed. If you use ordinary vinegar with wet clay the water content will get to high for use of commercial waterglass. A mixture with more wet clay may not work even with DIY waterglass.
I have activated 200g china clay (kaolin) with 100g vinegar and 120g water, which equals 2.5% acetic acid. Then I have mixed it with powdered waterglas, lye, liquid waterglass, 100g untreated white clay and a small amount of cement. The mixture became hard and water insoluble stone with a density of 1.2g/cm³. Despide the low density it is actualy harder, stronger and less brittle than the low density mixtures made with bentonite and a lot slag sand. Without poreless aggregate a geopolymer does not need such an extremely high porosity to achive a total porosity of about 50% and thus can be stronger.
Obvioulsly at least clays with low alkali content and a neutral or slightly sour PH-value can be activated with smaller amounts of acid, maybe even less would be possible.
For geopolymers with only fine aggregate without sand I would recommend not to use lime or cement to accelerate curing.
Mixtures without sand need more care for curing and drying. With very high water content to achive densities around 1.0g/cm³ or lower very slow curing and drying with extreme care is needed.
With respect to insulation nothing can beat an aerogel except vacuum or another aerogel. thus it will be worth the efford.
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