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Ben's 39" build - Forno Bravo Forum: The Wood-Fired Oven Community


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Ben's 39" build

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  • Ben's 39" build

    Well I poured my hearth slab yesterday and thought It was time to start posting pictures.

    I built a recess in for my insulation layer, and cantilevered the front, but really regret not adding more rebar to it. The front hangs out by 12 inches and I did put one number 5 and 1 number 4, but it just seems like it should have more because as a result of the recessed area it is only tied into the rest of the slab from the sides. The truck was a bit early and I was a bit behind, I had the bar but just didn't put it in. Oh well, cross your fingers and pray for it to hold for me ok?
    By the way as the curious and adventurous type I am, I am seriously considering trying to mix up a batch of EPScrete for my insulation below my refractory board. I have been reading up on it and have acquired a free bag of Expanded PolyStyrene, and plan to mix a small test batch tuesday.

  • #2
    Re: Ben's 39" build

    Your work looks great so far. What is EPScrete, and how much heat will it tolerate

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    • #3
      Re: Ben's 39" build

      EPScrete is essentially the same as Vermacrete (Vermiculite+Portland Cement) but using Expanded Poly Styrene Foam for the aggregate. I actually did it already and will post some pic's on it. EPS has a rating of around 180F. It would not be suitable under your hearth brick directly, but I believe is should be great under other high-tech insulation board. Actually I think that even if the top layer of foam beads melted due to the heat you would still have the concrete matrix with air pockets insulating and bearing the weight like a honeycomb, If your recipe has adequate cement in it. I will post on my trial and error and what I wound up doing.


      • #4
        Re: Ben's 39" build

        On EPSCrete.
        Ok, so I have a enough difficulty finding time to work on my oven let alone write and post about it, that my postings will not be as prolific as some.
        I will try to post Items that I think may be of benefit to others.
        One such Is my experimentation with EPScrete and Foamed concrete.

        After doing a bit of reading and locating a source of free ground up ExpandedPolyStyrene waste from a foam fabricator. I got to work.

        As you are probably already aware EPS is a very lightweight and effective insulator comprised of somewhere around 80% air.

        I took my free "Santa Sack" of foam and stuck in my weed eater and proceeded to carefully whack the foam untill the balance of the particles were .5" or less with the majority being down to single bead size of 1/8".

        Then I mixed up a batch using the standard 5 to 1 ratio of Portland to aggregate, but added 75% of the water first, and added around a 1/4 cup of liquid dish soap. after this began to be quite frothy I added the EPS and then the Portland a little at a time.
        As you can see from the below picture the resulting product was VERY aerated and light; undoubtedly an excellent insulator.
        After applying it and waiting a few days I was unsatisfied with the strength it had developed, which is a common phenomenon with Vermicrete users as well at first. I tore it all out and made another batch. However 2 weeks later I now feel that this recipe has developed an amount of strength that may be sufficient, but still recommend a little stronger mix.

        The second time around I decided that the aeration of the dish soap together with the EPS was overkill and that I needed to eliminate the bubble effect of the soap. I over compensated and used a mixture of 4 parts EPS, 1.5 parts Portland , and .5 parts fine sand. to this I used only a few drops of soap to break the static charge of the EPS and facilitate its dispersal.
        This proved to be a VERY strong yet light weight mix and I am sure it will serve very well.

        After all this my opinion is that a mixture of 5 to one EPS to Portland with .5 parts of a fine aggregate such as fine sand or even fire clay would give very good results. Adding fly ash, or the like may also be a worthwhile experiment.

        Also, on top of my cured EPScrete layer, which I rubbed with an abrasive stone to smooth out and level I mixed a batch of type S mortar to which I added a tablespoon of dish soap and blended at high speed with a mixing attachment for my drill. I used a notched trowel to spread this aerated mixture and create a level bed for my refractory insulation board.

        I found several discussions and a video or two on foamed concrete which I thought were very interesting and helpful with a google search.
        For those that have a difficult time sourcing Perlite or vermiculite I think these methods will provide a very good and perhaps superior insulating layer in the right conditions.
        Last edited by captkingdom; 08-09-2009, 04:36 PM. Reason: typo


        • #5
          Re: Ben's 39" build

          One thing I forgot to mention was that I used a small Hibachi Grill to sift out the larger particles that remained after the whacking.