Don Lyons

Has it been tried: Aircrete Refractory

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So, most of you have heard of Aircrete.  The mixing of cement with foam to produce a lighter yet strong version of material.  I've researched this and found the right mix and ingredients for small batches.

5gal Bucket of Aircrete =

4.7lbs cement

2.5lbs H2O or 32.8oz

2.1gal foam  (Made with Drexel foaming agent)

Has anyone ever tried to use refractory cement with a foaming agent?  I use HPV®-ESX CASTABLE, from HWI, (A fused silica castable designed for thermal shock resistance) for building my ribbon burners.  Its pretty pricey (well at least to me), but i've only used it to make the burners, not as a forge lining.

Any thoughts or ideas on this?  I might try making a small batch for testing, but what would be a good way to test.

V/R

D. Lyons

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Welcome aboard Don, glad to have you.

Sorry, I can't answer your question, I have zero experience and have heard no testimony regarding Aircrete, none.

Refractory cement on the other hand is a known quantity and not particularly suitable as a propane forge liner. Cements are designed to stick things together, not act as a flame face and are generally short lived when used as a flame face. Not being familiar with Aircrete and not planning on researching it for you I can only ask if you are misusing the term Cement.

If not and without seeing examples of Aircrete being used as a flame face for an extended period, I recommend you use a proper refractory instead. Then experiment with additives as test coupons tested in a HOT forge. I know I can't afford to line a forge as a blind test. Done it, have the reject forge carcasses to prove it. I keep them to remind me NOT DO THAT AGAIN!

Frosty The Lucky.

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I've seen examples of people making higher temperature flame things using aircrete, but they generally only post about the first firing, and no follow up on long-term durability (which will be abysmal since common Portland cement loses its structural integrity at forge temperatures).  

To date I've not seen anyone try to make a refractory aircrete mix.  If you've already got the foaming equipment, try it out and report back.  The usual way we do it is to add glass microspheres to the mix- they burn out and leave small voids (the same as air bubbles).

A good way to experiment using the foaming agent with refractory mixes would be to make firebricks or tiles out of the stuff.  Good for lining forges or use as baffle walls.  Then you can make fairly small batches and test pieces that may be easier to run experiments on.

Though to reiterate, aircrete that's used as a construction product is unsuitable for forge temperatures- it will crumble to bits in only a few firings.

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It's kind of amazing how many refractory products HWI makes. How did you pick the HPV-ESX? I suppose thermal-shock resistance would be good for a nozzle especially if used to modulate forge temperature by alternating high-low outputs. 

For the foam, do you mix the F.M.-160 with water to make a foam and then mix that in, or do you foam the water used to hydrate the refractory (I suspect the latter)? Is the foam stable enough to mix with the hydrated refractory and not collapse? I'd be interested in hearing more about your technique. It's a bit like bubble alumina or even mixing with another void-leaving substance.

Just now, HojPoj said:

I'd see about trying aircrete using a proper high temperature refractory instead of Portland cement- it may not have the same strength, but would be far more insulating (though one way to achieve the same effect is adding glass microspheres to the mix in order to get an aerated product).  If you've already got the foaming equipment, try it out and report back.

It sure seems like OP is talking about using a proper refractory -- HWI's HPV-ESX:

HPV®-ESX CASTABLE: Designed to be used for port blocks on carbon anode bake furnaces that are exposed to thermal cycling, HPV-ESX CASTABLE is a fused silica based castable possessing high strength and excellent abrasion resistance.

I think casting a burner block from it is the only way to really test it. 

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Just catching that now, got thrown off by putting the normal aircrete recipe down before.  (still bears stating though, since someone will likely stumble across this thread via the google since I've seen a recent uptick in videos of people using the stuff for *everything* under the sun :-\ )

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1 hour ago, Don Lyons said:

2.5lbs H2O or 32.8oz

2.5 lbs is 40 oz.

2.5 lbs of H₂O is 2.5 pints ("A pint's a pound the world round") or five cups.

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A fused silica refractory won't be resistant to forge welding flux.

Frosty The Lucky.

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This would be a refractory aircrete mix.  Using a refractory cement instead of regular cement.  Frosty, tracking about the non-resistance to flux.  It's what I have on hand, and used only for the burner construction.  I would have to use one of the other preferred refractory compounds for a proper lining.

We have an HWI in Birmingham, AL.  I called and ordered it.  Picked up when we went to visit family on the coast.

I'm out shopping right now for wood to make aircrete landscaping forms.  I'll get back to the thread later tonight.

Cheers

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Sounds good Don, keep us in the loop please. I'm always up for new ways to do things. 

I've taken to using the term "binder" rather than "cement" to differentiate between refractory cements and Portland cement. I've been trying to get it an accepted if not standard terminology so as not to confuse folk with no grounding in what "cement" really is.

Frosty The Lucky.

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On 5/3/2019 at 12:29 PM, JHCC said:

2.5 lbs is 40 oz.

2.5 lbs of H₂O is 2.5 pints ("A pint's a pound the world round") or five cups.

Yes, I copied that from my notes on my phone.  I meant to put in 38.34 fl-oz.  But you can round up to 40.

1 pound of water lb wt. = 15.34 fl-oz

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I'm just going to order some refractory binder and use the preferred methods of forge construction.  Frosty is correct, its way to expensive to "test" in a full forge pour, however it would be nice just to pour it in and let it set around a tube form.  I'm fairly confident that i will have enough refractory left over to make a few bricks for testing.

The foam generator build is complete and tested, its working great.  jwmelvin - I mix the F.M 160 with water and put in the foam generator.  You can make 160gal with just one bottle , that's crazy right.  I mixed a test batch and covered the grass in front of my workshop that night, next morning it was still there (although not as thick as the initial spray).

I'll follow-up when i have more to report.  This month is going to be crazy for time.  Daughter's graduation, house full of guests, land maintenance etc..

D. Lyons

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