The search for DIY light weight insulating fire brick IFB

Found some free time* to work on this project. My first attempt using some old 2300F refractory that I bought a decade or more ago from Budget Casting Supply, and subsequently swept up off the floor where a very messy and destructive racoon had spread it, didn't work very well. My first try was the super simple method I used during my lab days at Halliburton. That being to just add a bit of detergent along with some viscosity additive and mix aggressively to make bubbles. Works real well with nothing but G type cement and a bit of bentonite or FWCA. The sand in the refractory pretty well makes that simple method unworkable. I don't think taking the time to filter out the sand would be worth the effort.

So, on the the next method. Ordered some aluminum powder that arrived a few days late, but considering the supply chain problems today, and this time of year, it was kind of expected. The first try wasn't any more encouraging than the simple detergent method. It appears there isn't enough of the cementitious binder in the refractory mix to react with the aluminum. I added some lime. This test looks good enough to do some serious testing.

The pile in the foreground is the least dense and was mixed pretty dry with no detergent, like a trowel-able mortar, and exhibited a bit of exotherm. It didn't appear to rise much but I couldn't tell since it was just a lump. The other sample, in the tub, was mixed with detergent at a pour-able consistency. It didn't exhibit any exotherm. Shop temp about 40F. The picture probably doesn't show it but this sample did 'rise' about 50%.

The water crystals are essentially the same thing we called FWCA (Free Water Control Additive) at Halliburton. So far it looks like this is going to be possible as long as Lime is added to react with the aluminum and temperature is going to be a parameter that needs to be controlled.

Next - let the things dry/cure and then cook them in a toaster oven. Once those look good get my brother to cook them in his kiln.

Edit: added YT link to similar






* Stole, invented, appropriated, fabricated - since there isn't such a thing as free time.

 

Quick update:
Put the 'samples' in a toaster oven to dry. It appears that I can make material with the same density, or less, than commercial IFB.
The really light sample has really poor compressive strength - like 3/5 PSI.
The sample from the first test that showed some exotherm is around 30% denser than commercial IFB and the compressive strength is good enough to withstand saw cutting with a drywall saw.
Both samples would likely have much better compressive strength once cooked to operating temperature.

The down side:
These samples were just thrown together with a set of TLAR recipes. I'll need to get a postal scale that weighs accurately to 1 gr or less so I can do a set of proper tests - and keep track of each iteration.
There are none available locally so I'll have to wait for delivery.

In the mean time I'm considering ordering commercial IFB to build with. The desire to melt metal is growing stronger than the desire to experiment.

 

What if you got some rice bubbles (coated with wax or lacquer) or small styrofoam beads and mixed them in with the refractory?. After the cement cures it could be slowly heated over a day or so to avoid outgassing cracks.

 

Can't sleep tonight. Mind wondering around this dilemma. Maybe a nice 151 and Coke will help? Miss my Bacardi* but Don Q is almost as good.
This is my current thought using commercial IFB. I'm pretty much a 'poor boy' type and like to use what I have around. The skin is galvanized roofing/siding and the tube is 3/4" EMT.
This is a lift off patterned after AL2O3s work (THANKS! for the videos). The JPG below is pretty much what I'm thinking but is at this point little more than a sketch. The IFB is 1 1/2" thick and the ceramic wool is 2 inch in the pic but could easily be increased in CAD. I've got everything but the IFB - order pending.

I'd probably build from the outside in, placing the IFB last, and then cast the lid.

Looking for peer review - I don't consider myself much more than a 'lead' so peer is used loosely here.



* removed from the market due to flammability.

 

1) Understood and semi planned for. Thinking that the lower metal ring would be cast with the lower kiln refractory ring. I am kind of concerned that the different thermal expansion rates might eventually lead to failure. Probably should do the math............
2) Shown as fixed. I tend to over complicate/think things and CAD just makes it easier.
3) I LIKE simple. Your suggestion is being considered while the morning tea water is heating.
4) Belt and suspenders. The lift mechanism should be pretty well self centering. That little detail was made 'mid rum-n-coke'. Exterior guide pins would be easy enough to add if they were to be found necessary.
5) Hollow plinth, again, is a result of being simple in CAD. The thought was to cast them with wool inside to reduce mass. I do plan to have a couple of sizes so smaller crucibles can be moved up in the kiln.

Yes, criticism. But the GOOD kind. Much appreciated. I'm getting too old to make mistakes at the rate I did 20 years ago.

 

Current iteration:

I really liked the suggestion by AL2O3 about using ceramic board for the lid. Didn't realize until after a double check that my hoop handles are similar to his. Just wondering if they will be cool enough during use to lift with a gloved hand?
Getting close enough that I may order the rest of the parts today. I didn't know that ceramic board was so $$$. We have no local source so shipping is half the cost. Time = money.