How long for mortar to reach full strength?

Discussion in 'Horn Depot' started by 14tokihorn, Apr 21, 2008.

  1. 14tokihorn

    14tokihorn 1,000+ Posts

    I did some hardscape (technical term from

    - Set some native slabs of rock on the vertical to form a terrace-like edging for a new plant bed, and applied mortar in the joints and the trench for an informal footing

    Some of you in the know - is 48 hrs. enough time before I start putting soil over the mortar joints and the make-do footing? I did this over the week-end, and it would be nice to have it hold up as long as possible.

    Of course the construction technique says a lot about a sound installation, but lets not get into that

    The mortar doesn't feel cool to the touch this morning. All I know is this indicates that the moisture is getting out.

    What do ya think?
  2. l00p

    l00p 10,000+ Posts

    It's a humid day today so that may affect it. But rains are not expected, even slight chances, till Wednesday. I would say that by the end of today. How much the humidity affects it, I don't know but I am pretty sure it will prolong it some. I know it affects paint drying.
  3. jerich9701

    jerich9701 25+ Posts

    Mortar and all other concrete products usually reach 95% of their strength in 7 days. That being said and given that you want to add dirt behind it (dirt is one of the heaviest materials including concrete). I'd give it 3 days to set. We usually wait 3 days after a concrete pour to let equipment get on it. You should be home free after 3 days.
  4. Thunderhoof

    Thunderhoof 250+ Posts

    Mortar, like concrete, cures. Putting dirt around the joints will probably help them cure more slowly, which is actually a good thing and will help with the strength of the mortar.

    The thing I would worry about is how much you will actually be impacting your new rock work. If you are rolling wheelbarrows over the stuff and generally knocking the crap out of it, you should probably wait a few days before you do that. The three day rule mentioned above is probably a good one if that is the case.
  5. TexasEd

    TexasEd 1,000+ Posts

    Right, you want it to cure slowly for maximum strength. If it was 100 degrees out I would say cover it with plastic to slow it down. The dirt will help slow down the process. Just don't stress the mortar.
  6. AstroVol

    AstroVol 500+ Posts

    Full strength/design strength, by definition, is the strength at 28 days.
  7. BigWill

    BigWill 2,500+ Posts

    Agree with Astro, but I would add that it gains most of it's strength in the first few days, then the rate slows quite a bit.
  8. 14tokihorn

    14tokihorn 1,000+ Posts

    Well, today makes 3 days. I could fill the landscape bed this evening. I've slapped the stonework pretty good, and so far so good.

    Then again, if I filled now, then the joints would then have only one side against the added soil, the other side being open to air.

    Sounds like the cement component actually has a chemical reaction in which water is required? Since a longer cure is better.
    I mean, the mortar might seem solid (and it is) in this initial period , but chemically, what moisture remains in the mix goes toward curing? ...and the evaporation effect is the another factor working against the cure.

    Anyway, I read the printed stuff on the bag... it did say that curing can be helped by misting with water, after such and such a time. That applies, as someone stated for real hot, dry weather.

    ... this is not a huge amount of dirt - I've got right at 3 inches per foot on the slope I want to fill in for a level surface. So the lowest edge will have 12 inches behind it (4 ft. total length).

    I guess I could wet down the sides exposed to air, or does is that total overkill? its easy to do, though.

    [edit] its Google time
  9. AstroVol

    AstroVol 500+ Posts

    Concrete usually gains 70% of its design strength in the first 7 days.

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