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Correct Sand for Homemade Refractory Cement Mix?

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  • Correct Sand for Homemade Refractory Cement Mix?

    Hi, I built a 36 inch oven following the Forno Bravo Plans about 4 years ago and unfortunately moved and had to leave it behind so am now building a smaller 30inch oven at my new house. I learned a few lessons (like proper insulation under the oven floor) so it's not a bad thing to have to build another.

    I've build by stand and laid my oven floor and am now ready to build my dome but I don't recall what type of sand I used last time. The mix I used previously is as follows:

    1 part cement
    3 parts sand
    1 part lime
    1 part fireclay

    I have nearly a ton of builders Sand left over from building the base/stand and wondered if it would be ok to use that? or if I must use silica or sharp sand instead for some reason.

    It would be great to hear if anyone else has used builders sand for their Refractory Cement Mix and if they had any issues.



  • #2
    I used mason sand im almost sure builders sand is the same
    My Build Pictures


    • #3
      Thanks Chach. Given you are in the USA it might be the same thing and what you guys call it over there as you say. I suspect last time I built my oven using Sharp Sand as the mix ingredients I was given by the firebrick supplier suggested this. I guess the key difference there is sharp sand has larger Pieces. However given I'm mixing a mortar here builders sand is what you'd use for making mortar over here (It's what I used for building my block stand). I'm just concerned if it might crack or fall out more easily as it's finer than sharp sand or if it might not be able to stand the high temperatures. How long have you been using your oven for?

      Anyone else had any issue with builders/mason sand at all?


      • #4
        almost three months not a super long time but no matter the size of the sand heat should have no factor...sand is sand and the size shouldn't matter for heat since its the same make up. now size of the sand may play a factor in how well it holds up but more than size is shape. you do not want play sand too fine and I believe more rounded. mason sand has all different shapes and sizes and gives you a good aggregate to make mortar. I seen builders sift mason sand to get the smaller aggregate so they can point tighter joints where the larger aggregate would not get I to those tight places. so in the end you INMHO you can use the builders sand because it more than likely has sharp sand in it but not the rounded sand. please if anyone disagrees chime in or if I am wrong here.
        My Build Pictures


        • #5
          Thanks, I appreciate your feedback on this. I'll go with the builders sand then for the mortar given I've got a load of it left!


          • #6
            Hi Adam. I just used normal builders sand from B&Q for my home brew mix. Have fired my 36inch oven up most weekends and many many time all summer - no problems at all. I m like you though - insulation under the floor could have been better! Only did one calsil board thickness, wish I done two!