Trench Footing Placed in Water
Trench Footing Placed in Water
(OP)
I received pictures from one of our projects showing continuous trench footings being placed in water. The water is half way up the trench, rebar has already been places, and concrete is being placed in the trench as is. Can any one come up with a reference where this would not be allowed or is this common in areas with high water tables. I guess as the concrete is placed, it would push the water down the trench and out and would not mix much, if any, of the mixed concrete with the water in the trench. Any comments on this would be appreciated.






RE: Trench Footing Placed in Water
Especially if the rebar has been sitting in this water for any length of time.
RE: Trench Footing Placed in Water
Placing concrete directly in standing water will wash out too much cement from the mix, giving unpredictable results.
For larger placements, concrete can be successfully placed under water with a "tremie". Here is a short explanation of the principle: http://en.wikipedia.org/wiki/Tremie
The concrete first placed with a tremie will go directly into water, thereby loosing cement. Once this weakened concrete is in place the tremie works successfully to place remaining concrete "from the bottom up." The initial weakened concrete is compensated for by making the under water structure (say, a cofferdam seal) of greater thickness than theoretically necessary.
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RE: Trench Footing Placed in Water
This is a bad practice! Do not allow it on your projects. My only change to what SRE noted is that you pump from a sump adjacent to the footing, not in the footing. Pumping from the footing will loosen the footing bearing soils. Pumping from a sump adjacent to the footing will actually tighten the footing bearing soils, if granular material.
RE: Trench Footing Placed in Water
RE: Trench Footing Placed in Water
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RE: Trench Footing Placed in Water
RE: Trench Footing Placed in Water
RE: Trench Footing Placed in Water
RE: Trench Footing Placed in Water
RE: Trench Footing Placed in Water