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Heat-holding, and heat-tolerant, concrete.

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  • Heat-holding, and heat-tolerant, concrete.

    Started my barrel-vault WFO recently, and completed the suspended, structural slab yesterday. Besides resting today, I decided to join and ask a few questions to get ready for the next steps. I have a conventional dry-stacked, filled-core masonry block base, and the suspended slab, topped out at a height of 33" above the patio. That leaves me approx. 4" for insulation, then another 4" for a heat-storage slab, that'll then have the 4.25" firebrick set on it. All together that adds up to approx. 45" height, which I beleive is on the money for a 6' person to work comfortably. I have lurked here for several months, and have become stuck on the composition or recipe for the heat-tolerant slab. I've also seen a number of threads here where the construction seems to eliminate the heat-storage slab in favor of firebrick on insulation layer on support slab (with only the firebrick as the hearth heat sink.) Can someone provide a clear description of how to make the hot slab? I'd prefer a pre-mixed, bagged product, if that's available. Also, since I'll be using 4" of the American Fibrex FBX1900 board insulation under the hot slab, I'll be adding a single rebar mat to that slab so I don't crush the FBX1900. All comments welcome, and thanks all for the collective info.