Original type Durock..

[turbocruiser]

well after hours of direct flames, its still togeather, i also flipped it over and the point broke off , but the fibres inside it kept it togeather.

so i smashed it on a stick, it broke apart but yet the fibers kept it in pretty much in one piece.

the weight feels the same as before.

it doesnt look anymore porus after buring.

i cant belive the fibers didnt burn.

one unusual thing i wasent expecting is, one side of the board the mesh is white, and the other side is black. wonder if its 2 different types mesh in the concrete board itself?

Wow that was really interesting to read through! Thanks for taking the time to experiment. I'm wondering whether the next time you start burning that barrel up (if you have any additional scraps) can you screw a section of 2x4 to the backside of the backerboard and place the backerboard on the fire to see if the 2x4 burns? I guess you would either have to wrap the 2x4 with backerboard or put a small section of 2x4 on a large section of backerboard but I'd be interested in seeing the results there. Out of curiousity when you were striking the stuff with sticks did it seem to have the same strength as new or was the strength somewhat diminished after burning so hot and so long? Again thanks for taking the time to do that!

 

[begreen]

I believe the fibers are fiberglass.

 

[greythorn3]

well after hours of direct flames, its still togeather, i also flipped it over and the point broke off , but the fibres inside it kept it togeather.

so i smashed it on a stick, it broke apart but yet the fibers kept it in pretty much in one piece.

the weight feels the same as before.

it doesnt look anymore porus after buring.

i cant belive the fibers didnt burn.

one unusual thing i wasent expecting is, one side of the board the mesh is white, and the other side is black. wonder if its 2 different types mesh in the concrete board itself?

Wow that was really interesting to read through! Thanks for taking the time to experiment. I'm wondering whether the next time you start burning that barrel up (if you have any additional scraps) can you screw a section of 2x4 to the backside of the backerboard and place the backerboard on the fire to see if the 2x4 burns? I guess you would either have to wrap the 2x4 with backerboard or put a small section of 2x4 on a large section of backerboard but I'd be interested in seeing the results there. Out of curiousity when you were striking the stuff with sticks did it seem to have the same strength as new or was the strength somewhat diminished after burning so hot and so long? Again thanks for taking the time to do that!

i will see what i can do with an additional experement

anyhow i was striking the cement board with the point of the stick, it was really tuff, i dont believe it lost any of its strength over before it was cooked, it took several shark smacks onto the point of the stick. i will try to get a video next time also.

 

[turbocruiser]

This is terrific information! Thanks again for all the experimentation. From what you've written I'd say that the Durock is more than adequate in terms of the safety and strength in high heat applications. I don't think we will ever know if it has any polystyrene in it but I think we definitely do know that it doesn't affect the safety or strength and that's awesome info!

More and more I'm thinking that with all the discrepancies and disinformation even from the folks at USG, what it really is, is that USG simply hasn't had the product properly rated for this application yet. I'm really interested in what BeGreen was saying about approaching them as an official presence to request that rating.

One thing that really impresses me about them is their website is so vast and so specific in so many specialized ways. As an example if i remember right, they have something like sixteen different "sheetrock wall systems" for their Type X Sheetrock, all with awesome PDF's, and specs, that spell out everything. I remember many moons ago I had to call them to ask about achieving some specific fire rating for my garage and the technicians started by explaining the extreme importance of the "system" of the wall and asked me ten to twenty things about how I had built the walls before they would then answer what I was asking (how many layers for how much rating). They didn't do that in any rude way whatsoever; they did that in a perfectly professional way that really explained and emphasized that the "system" is so important. Maybe that is part of our problem here; designing a standardized hearth that fits anyone? Or maybe it really is what the technician told me about the polystyrene they put in there? Still if that is a small and secret (at least as far as MSDS lists) part of their own "proprietary mineral blend" used as binder agent or whatever it is, I cannot see it matters much thanks to this experiment. Thanks again for taking the time to do this for everyone's education!