Carbon bread foam as aggregate in GP

[coastalrocketeer]

Six hours into drying phase, uniform gray colored surface, and down to 176.65g

calculating all my non h2O ingredients for this mix, it should weigh 137.5 grams when dry, less any losses for the small amounts of material that stuck to tools and fingers and got washed away.


Turning toaster oven up to 170-180F because, like Karl, I am impatient... and the carbon foam aggregate seems to support fairly rapid drying 

[coastalrocketeer]

Second test mix is in the mold, with 30g acid activated bentonite(30g 5% vinegar activation), 15g crayola “air-dry” clay, 3g lye, 98.5g H2O, including the vinegar’s water, 20g Red Devil TSP90/sodium metasilicate/ solid waterglass(for roughly 200g/l concentration), and 5g cement as accelerator, and 53.6 g (volume of my mold) of carbon bread foam aggregate.

This is definitely an LTGS mix, with the carbon foam as aggregate, not “flowable under vibration”, even with a “soft mayonnaise consistency” (high water) binder. I have to “tamp it” into the mold, the bread foam is softer than perlite, and needs to be tamped in at about 1/2” thick or the top layers of CBF aggregate just crush, instead of moving what ‘s below... I found “slapping it” with a silicone spatula and using the tip to push the corners and edges down to fill them in worked well, but for my 1” deep mold I should have done so in a couple of layers.

I didn’t pack the bottom of the mold as nicely as I would have liked, but would have run short at the top if I had, so in future mixes, I will add an extra tablespoon or two of carbon foam so I can pack it in a bit more and not run short.

One thing I like about this mix for a castable, is it seems to have nearly ZERO drying shrinkage up to this stage. Will be interesting to see what happens to it when I put it on top of the rocket core riser flame path and fire it up to a MUCH higher temp.

[coastalrocketeer]

3g less than calculated so far... may have been water in the dry ingredients... curing at 400F, 204C... about to go figure out how to fire it on my iron bars suspended over my prototype core.

[coastalrocketeer]

Well, my first brick, and by extension my second, are a flop... basically clay infused charcoal briquettes.

So the inference I make is that the CBF needs to be a smaller portion of the mix... i’ll try 50% by volume next.

I’m also going to try just the clays, and see if they are geopolymerizing and becoming a refractory on their own

Am going to try Zeolite and Rockwool with and without carbon foam as well.