Carbon bread foam as aggregate in GP

[coastalrocketeer]

Well... a larger test, or Karl’s chemistry knowledge may well prove it’s not a geopolymer, as I haven’t done a slow cure and dry and then a water test... but I can glassify this stuff as soon as it’s dry with a propane plumber’s blow-torch, so that’s good enough for me! Lol!

I’ve made an unorthodox mix with a totally experimental binder based on what feedstocks and chemical attack agents I had on hand, which I will detail in the following posts to this thread. Not yet having what I’ve intended to use for aggregate on hand, I decided to play with some carbon bread foam as aggregate.

My zeolite Geopolymer core from the other thread is still waiting for me to get the rest of what it needs to start heating our home with it constructed.

Getting back to reading here and working on that finally, with winter approaching again.

Sorry to everyone for being gone so long, life has been challenging this year. I hope @karl , esbjornaneer , sksshel , Jura , firewatcher , pigbuttons , travis , and everyone I’ve discussed Geopolymers and Rocket Stoves with in the past here on this lovely forum are doing well...

[coastalrocketeer]

I mixed 10 grams of bentonite clay with 10 grams of vinegar, which made a paste he thickness of spreadable butter, and heated it on a low simmer (2-1/2 on my ceramic cooktop dial) until it got considerably thicker, about like cold butter from the refrigerator, which presumably upped the concentration of the acetic acid to attack the and exfoliate the layers of the bentonite. (Starting value of 10 grams vinegar provided the 5% acetic acid by weight of bentonite that Karl recommended in his “acid activated geopolymers” thread.

(With my bentonite, it takes a LOT less water to get it to a stirrable consistency with the vinegar as the water source, as acid makes it have less water demand for a given thickness, if I understand correctly)

I scraped that Bentonite paste, once cooled, out of the pan and then activated 10 grams of Clinoptilolite zeolite (SweetPDZ stall freshener powder from the feed store) with 5 grams of NaOH/sodium hydroxide/lye.

I heated the zeolite on simmer and placed the lye on top, stirring it in and then added the 10 grams of water a third or so at a time, stirring it until the consistency changed and I could feel the mix “thicken”

I kept the pan on simmer, and reduced the moisture in the zeolite lye mix until it was like very thick honey. (Note that “gritty portions” still remained within the binder, as before, but I was able to feel when the thickness and appearance of the mixture changed as the dissolution of the zeolite occurred, it also started getting a “skin on top, like gravy)

I was only able to heat this way, without a double boiler due to constant stirring, and adding water when it felt like it had gotten “way too thick, like sticky caramel. I think that evaporating out part of the original 10 grams of water helped dissolution by increasing lye concentration temporarily, until I added the “make up water” to get back to the “honey” thickness I was going for.

Each of those “cooking steps” took about 15 minutes.

Then I mixed the vinegar activated Bentonite with the NaOH/zeolite binder and it didn’t explode... LOL... So I added a few grams of water a tiny bit at a time, until it had a consistency like mayonnaise, easily stirrable, but kept peaks when I pulled the stirring stick out...

Then I added pinches of the carbon bread foam aggregate until the consistency “seemed right” (I could press it and mold it like sticky clay, and it didn’t fall apart, or lose it’s shape when pinched up in a mound, kind of like soft, lightweight adobe.)

It was somewhere around the same volume of carbon bread foam aggregate as binder... I didn’t weigh it. Will do so on future batches.

I took it from the tiny pan and put it in a ziplock bag about 3x3 inches and pressed it out, getting as much air out of the bag as possible, and sealed it.

Left it sitting on top of a lamp shade that kept it at about 38C/100F overnight. It didn’t seem to harden much, and I am impatient so I cut the tiny bits of the corners off the bag and put it in the toaster oven to dry after at 50C/120F overnight. The next day I feel impatient as it seemed about 50% dry, and cut the edges off the bag to remove the top face and dry it faster. Turned the toaster oven up to 77C/170F and left it in for 5 hours while I went shopping. Was only 2.5 mm thick, so probably was dry well sooner than that.

Then I took it out and torch-cured it... first with a tiny butane soldering torch, which created the grey pattern areas and a smal glassified area on the surface.

I forgot to weigh it before that torching so don’t really have LOI figures.

Then torched each side with a plumbers propane blow-torch, which glassiifed the entirety of it in about 2-1/2 minutes per side.

I will see if it passes the water test now... it is very lightweight, and the sublimation of carbon from the structure of it seems to be inhibited or does not affect it’s strength negatively during the torching process.

Here is a video of the torching of the first side:

www.youtube.com/watch?v=J7x6TAlD1fE

[coastalrocketeer]

Here is a video showing the hard glassy sound after firing (it was a dull thud after drying, but before firing)


www.youtube.com/watch?v=16DJhE-osuk

[travis]

Sorry Im not sure what carbon bread foam is

[coastalrocketeer]

It is basically bread biochar... Pyrolized in a closed container (vents on the bottom,for expanding gasses to escape,) so that it basically becomes a carbon foam that is highly insulative, and refractory, but it normally burns when exposed to oxygen and heated past it's ignition point.

My initial test seems to show that it no longer burns when encased in a geopolymer binder matrix as the aggregate. Still to be tested is how much of it's insulative value it retains, as the sample I made was too small and thin for that.

It is very lightweight, which could allow lightweight fireproof core materual that is cheap, and insulative, and sufficiently strong.

I'll post a few videos others have made illustrating the material's properties.

[coastalrocketeer]

[drooster]

Bread charcoal??

[coastalrocketeer]

Basically, except more completely pyrolized than BBQing charcoal

[Deleted]

A castable graphitic carbon foam could also be made by dehydrating sugar or other carbohydrates with sulfuric acid.

Molar mass of C12H22O11 is 342,2965 g/mol
Molar mass of H2SO4 is 98,0785 g/mol

C12H22O11+H2SO4 = 12C + 12H2O+ SO2 + O
Weight ratio of sugar to concentrated acid 342,3/98 = 3.5/1

C12H22O11+2H2SO4 = 12C+13H2O+2SO2+O2
Weight ratio of sugar to concentrated acid 342,3/196 = 1.75/1

Much larger amounts of H2SO4 will be neutralized as well.

SO2 reacts with water to form H2SO3 (sulphurous acid),
thus one needs a fan to blow the steam away which also may contain
small amounts of sulfuric acid.

The chemical reaction is explained here:
www.quora.com/Can-you-balance-this-equation-H2SO4-+-C12H22O11-+-O2-C-+-H2O-+-SO2-dehydration-of-sucrose

With a very small amount of acid.

Maybe this reaction could be used to blow up a phosphoric acid-based geopolymer.

[coastalrocketeer]

I found the perfect mini “brick molds” for mix testing. They hold about 250 cc full (a little more than a cup) and have square sides, which most small containers do not. They are sold as “crayon boxes” at MallWart, for $0.69 ea...

I am currently curing my next carbon foam aggregate GP test mix in one of them...

First 10 hours at about 40C/104F on top of an LED lamp with a foil “bell” over it.

5 hours in the toaster oven at 65F/150F







It is significantly solidified, and currently weighs 241 grams... I have now removed the lid and will let it dry at 65C/150F until dry enough to unmold, then continue drying from there if necessary. I will go over my ingredient weights and see how much water I have left to remove.

[coastalrocketeer]

De-molded, an hour and a half later... lost approx 10g water weight so far

 

[coastalrocketeer]

A bit stuck to the mold 

[coastalrocketeer]

Closeup of inner structire 

[coastalrocketeer]

Losing water at about 10g an hour at 65C/150F



Turning cinder block grey where it is driest

[coastalrocketeer]

By my calculations of dry ingredients, it should weigh between 140 and 150 grams when fully dried, so around .56 to .6 grams per cubic centimeter.