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Guidance for bearing on wet concrete?

Guidance for bearing on wet concrete?

Guidance for bearing on wet concrete?

(OP)
ACI 308 shows that properly cured concrete (above 50F and moist) will achieve over 50% of it's strength within 7 days. We're placing a large piece of equipment on a pad and if possible don't want to wait the full 28 days. If the compressive stress due to the equipment is below 50% strength level, can the equipment be placed at 7 days? Is there a chance of settling or sinking within the pad? Is there

RE: Guidance for bearing on wet concrete?

I would think that this would be fine. You might want to do some testing to ensure that you're getting 50%f'c at seven days. In a suspended slab, early loading can lead to long term deflection issues but I doubt that would cause issues here. It might be worth giving some thought to the impact that this might have on your fasteners. If I remember correctly, some fastener capacities are governed by the concrete strength at the time of install rather than the final concrete strength.

I like to debate structural engineering theory -- a lot. If I challenge you on something, know that I'm doing so because I respect your opinion enough to either change it or adopt it.

RE: Guidance for bearing on wet concrete?

Do you have access to a schmidt hammer? At the very least that will give you a good idea of the bearing capacity of the concrete surface.

Maine Professional and Structural Engineer. www.fepc.us

RE: Guidance for bearing on wet concrete?

Increase the strength of the concrete you plan to use. Cheap insurance. Not likely an issue anyway except as KootK noted...anchor/fastener issues. You will not develop the fastener strength that quickly.

TME....bite your tongue!lol It won't tell you much other than the consistency of the surface response of the concrete.

RE: Guidance for bearing on wet concrete?

Wait, you're telling me a $160 device that is just bouncing a spring loaded rod off of the surface might not be accurate for more than surface hardness? I am shocked! Shocked, I say! :P

Figured it couldn't hurt and might provide one more check to ensure the equipment doesn't deform the concrete surface.

Maine Professional and Structural Engineer. www.fepc.us

RE: Guidance for bearing on wet concrete?

Or specify high early strength concrete. No flay ash, all portland. You can get 100% in a few days.

When I am working on a problem, I never think about beauty but when I have finished, if the solution is not beautiful, I know it is wrong.

-R. Buckminster Fuller

RE: Guidance for bearing on wet concrete?

Or thicken the slab undertow equipment and add extra resteel.

Mike McCann, PE, SE (WA)


RE: Guidance for bearing on wet concrete?

The bearing stress of the equipment on the slab should not be confused with the compressive strength of the concrete. Unless this is a VERY heavy piece of equipment, and it is on a pad sitting on the ground, there should be no issues in placing it after a few days time.

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