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Setup time for new cement mortar

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  • Setup time for new cement mortar

    I plan to demolish several old concrete block foundation supports for a back porch. I'll jack up the porch ajacent to each concrete block support and demolish each support individually. Then a new concrete block support for the porch will be constructed to support the porch. How long should I let the mortar between the new blocks set before I let the porch load down on the new block support?

  • #2
    Re: Setup time for new cement mortar

    Originally posted by engineer View Post
    I plan to demolish several old concrete block foundation supports for a back porch. I'll jack up the porch ajacent to each concrete block support and demolish each support individually. Then a new concrete block support for the porch will be constructed to support the porch. How long should I let the mortar between the new blocks set before I let the porch load down on the new block support?
    Too many factors to give a correct answer.

    There are different types of mortar.

    The mix ratio.

    The weather. Yes, the weather.

    The type of block used.

    The load.

    I'd get a good mason or follow the mortar mfg. to the letter.

    J.C.

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    • #3
      Re: Setup time for new cement mortar

      if it was concrete, they would keep it free of any heavy loads for 30 days, a minimum of 14 days, http://www.ce.memphis.edu/1101/notes...roperties.html

      in my experience and reading most all masonry/cement related strengths are compared to a 28 day to 30 day strength,

      I can not give you a real answer as I have never studied this out before, but I would think the curve would be a guide in the strength of mortars as well, 3 day about 25% of finished strength in compression, 7 day about 50% and 14 day about 80%.

      a porch is not normally that heavy, I would say a bare min of 3 days and preferably 7 to 14 days, if possible longer, (if weather and temperature is reasonable), It is impossible to say as I am not there can not see the situation.

      In doing a web search I can not really find much besides on how to test it for strength, most strength curves are for cement, but since mortar is a cement product I would think it would follow closely,

      http://www.ebuild.com/articles/articleId.62753.hwx
      Compressive strength. Seeing the emphasis placed on this property by architects and engineers in most project specifications, you would think that compressive strength is the single most important mortar property. In fact, it's not as important to the performance of the masonry assembly as workability and bond. Architects and engineers single out compressive strength as a selection criterion largely because it's easily measured.

      Compressive strength is increased with more cement in the mix and decreased with higher ratios of water or sand to cementitious materials. Mortar's compressive strength has significantly less influence on the compressive strength of the masonry assembly than does the compressive strength of the masonry units.

      For example, the compressive strength of Type S mortar is 140% greater than that of Type N mortar, but Type S mortar increases the strength of the masonry assembly by only about 20%. However, when the compressive strength of the masonry units is increased 50%, the compressive strength of the masonry assembly increases by about 40%.
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      Last edited by BHD; 07-26-2009, 09:23 PM.
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      • #4
        Re: Setup time for new cement mortar

        ask who ever you bought material from. breid

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        • #5
          Re: Setup time for new cement mortar

          Originally posted by breid1903 View Post
          ask who ever you bought material from. breid
          unless of course you got it at Home Depot.

          1. good luck even finding someone to ask.

          2. once you do find someone, their answer will more than likely be

          3. If by chance you do get an answer, it's sure to be wrong.
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          • #6
            Re: Setup time for new cement mortar

            I checked with the local masonry contractor we use on most of our jobs. He said the set would be sufficient in 24hrs to handle the weight of the typical porch. He reminded me that they will complete a 10' wall in two days which has much higher loading than the typical porch.....Ray
            Last edited by roadrashray; 07-29-2009, 02:33 PM.

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