Is this a quality fire brick?

[Brick Oven Nick]

I've found a local masonry supply source that stocks a low duty fire brick made by Whitacre Greer. Spec sheet is attached. Is this a quality fire brick for my 40" Pompeii style dome oven? I don't understand what the different elements indicate. Is Alumina % an indication of how long the fire brick will hold the heat? The FB plans call for medium duty, 38% alumina. I can't find any brick with Alumina that high. I thought I would save rather than spend the money to have the medium duty bricks shipped from FB. These are 27.6% alumina. Will this low duty brick deliver quality results? Thoughts?

Also, I'm using the fire brick as the oven floor, so that will be a thickness of 2 1/4" thickness, whereas the dome brick will be 4 1/2"'thick. Would it be smart to add a split brick of 1" underneath the oven floor brick to increase the mass there to roughly 3 1/4"s. I'm hoping to not only cook pizzas but some light bread baking as well.

Thanks!

[Tscarborough]

The Whitacre-Greer work well, especially for the floor. You do not need to add any more mass on the floor, as that is the hardest part to heat already.

The alumina content relates to the density and wearability of the brick. That is what Low, Medium, and High duty mean as a rating system: durability. It has nothing to do with use in an oven, but for use in a contact application such as in an iron crucible. Of course, the more dense, the more heat it will retain, but also the higher the conductivity. Medium duty is not that good for the floor because of this. Low duty is just about perfect, if not still a tad too high.

Just stay away from the crappy Elgin firebrick.

[Tscarborough]

Also, If I haven't talked to you already, you can call me with any questions: 431-0870

[Audionatic]

i used literally exactly the same brick for my entire 40" vaulted oven and it works very well. The only thing I'd recommend, is not laying the floor "straight".
Use a staggered or herringbone pattern, so you don't have 4 brick corners touching. The corners can crumble a little over time and if the 4 corners are lined-up you may get
little craters. Haven't had any problem with my craters, but it's better to avoid them. Good luck with your build.

[Brick Oven Nick]

Great! Thank you both for the messages! Tscarborough, thanks for reaching out. Someone in the area is great to know! I'll reach out as things progress with the build. First few steps went okay, but I'm worried about my skills as a novice mason. We will find out soon.

[Tscarborough]

Better to ask than hear that the best recourse is to tear it down. Call me tomorrow, you know the area code.