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Thread: questions about concrete

  1. #1
    Join Date
    Nov 2009

    questions about concrete

    I have my pond planned out and I am digging my hole, but I am still wondering what I do about the concrete bottom. I live in the north where it gets to be pretty cold and I do not know how I will be able to keep the slab from cracking. any ideas would be welcome.

    I have seen quite a few ponds here that are concrete with stucco or something else lining them and I have always wondered how to go about constructing one so that the freezing and thawing of the ground does not have an effect on it.

  2. #2
    MCA is offline
    Honmei MCA's Avatar
    Join Date
    Dec 2003
    If we talking koi pond...then depth should be 6'+. So allowing for a 2' semi-raised pond...concrete floor should be around 4' below grade. That should be be low frost line in most areas of the US. And if you go the full 6' below grade...that should put the floor well below the frost line. So if you put 3/8" or 1/2" rebar grid based on 1' increments, and suspend that grid mid depth of the concrete (which would be at least 6" thick, with deeper concrete around the BDs, drain pipes and air pipes)....that should make a nice firm floor. Make sure the dirt is well compacted before the pour.

    You can seal a koi pond the as is done with a pool....pool plaster. Other choices could be plaster/stucco with waterproofing chemicals such as Zypex or others. And there is always liquid sealants such as CIM, Koi Armour, liquid rubber...etc.

    See the thread about waterproofing concrete blocks.

    Sure you want to do this if you are moving in a couple of years?
    Koi keeping is not a belief system; it is applied science with a touch of artistry.

  3. #3
    Nisai Motown's Avatar
    Join Date
    Dec 2003
    Dearborn, MI USA
    If your ordering the concrete from a comercial outfit (Concrete Truck Delivery), ask them to add a type 3a antihydro add mixiture to the concrete. The concrete mix will have less water in it and will be less prone to cracking. The add mixture also has the added effect of making the dried concrete less capable to absorb water. Less water absorbed less damage in freezing conditions.

    Also, build your pond base well below the frost line.

  4. #4
    MCA is offline
    Honmei MCA's Avatar
    Join Date
    Dec 2003

    The only skin we care about here is koi dermis. What are your credentials in that regard? Are you a fullly certified ZNA judge perhaps?

  5. #5
    Join Date
    Dec 2003
    Well "North" is pretty subjective?
    So I'll take the "extreme" ...like Chicago?
    A 2ft above ground pond! won't a pond like that create a unique set of problems?
    Would the upper two feet freeze solid and possible result in the concrete being popped open like a galls of water left in the freezer?
    I do not KNOW...but I am asking from a naive position just so i can understand. i would have thought the walls would be built angling slightly outward so the ice had a place to go/grow

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