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Materials for refractory concrete

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  • Materials for refractory concrete

    Hi
    My brother in law is looking to make a cylindrical oven from concrete as per photo.
    What is a suitable mortar mix suitable for (1) high temperature (2) safe for cooking (3) thickness of 75mm, with respect to cracking.
    Materials will be sourced from south-west Europe.
    Click image for larger version

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    Last edited by wood11; 12-06-2017, 12:44 AM.

  • #2
    The best, but also the most expensive, is to purchase dense castable from a refractory supplier. To this mix you just add water to get it to a workable consistency. It will contain high temperature aggregates and burn out fibres to assist in water removal to resist steam spalling. Secondly, you can make your own refractory concrete with calcium aluminate cement, sand and relatively fine (up to 7 mm) basalt aggregate also adding fine polypropylene fibres to the mix. This mix is far cheaper, but the aggregates (sand and basalt) are not high temperature aggregates and have some problems with excessive thermal expansion north of 500 C. A third and even cheaper option is to use the homebrew mortar which does not use calcium aluminate cement but uses lime and Portland cement instead. It is 3:1:1:1 sand,Portland cement,lime, clay, Also a good idea to add the fine polypropylene burnout fibres. All refractory concretes require a slow heat up firing schedule to prevent steam spalling. Usually around 50C/ hr until reaching 350C then no greater than 100C until reaching service temp. (If you see visible steam then you are going too hard’ back off)
    Also calcium aluminate concretes reach their full strength in 24 hrs so no need for damp curing. Portland cement concretes reach over 90% of their potential strength in a week so hold moisture in for a week.
    A fourth alternative, and the cheapest, is to use clay. If you dig it it’s free
    Sorry about the long answer, but it’s not a simple, there are plenty of alternatives.
    Last edited by david s; 12-06-2017, 01:14 PM.
    Kindled with zeal and fired with passion.

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    • #3
      Thank you very much.

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