WHAT TO CHECK WHILE CONSTRUCTING PILE FOUNDATION UNDER WATER?

Guidelines to Follow While Constructing Pile under Water

1. While placing concrete by tremie method, all tremie pipes should be cleaned before and after use.
2. The diameter of tremie pipe should be preferably 200 mm for constructing piles of all diameters within 600 mm.
3. For 25 mm down aggregate, tremie pipe should have a diameter not less than 200 mm and for 20 mm down aggregate tremie pipe should have a diameter not less than 150 mm.
4. The workability of concrete when measured by slump cone method should be in between 150 to 180 mm.
5. The cement content of concrete should not be less than 400 kg/m³. This will make the concrete coherent.
6. Always keep the tremie pipe full of concrete and keep it at least one meter into the concrete in bore hole with adequate margin against accidental withdrawal of tremie pipes.
7. The pipe should be concreted wholly by tremie and the method of deposition should not be changed midway to prevent laitance.
8. If due to some reason any interruption happens while concreting, then it should be resumed within 1 or 2 hours, but the tremie pipe should not be removed out of the concrete. From time to time raise and lower the tremie pipe to prevent setting of concrete around the pipe.
9. If accidentally tremie moves out of the concrete, then reintroduce the tremie pipe 60 cm to 100 cm in the old concrete and resume the concreting operation.
10. The top of concrete in a pile should always be brought above the cut-off level. This is done to remove all laitance and weak concrete and to ensure that good concrete remain at cut-off level.
11. The reinforcing cage should be of sufficient length and after inserting it into the borehole, the cage should be left with adequate extra length above the cut-off level for proper embedment into the pile cap.
12. When concrete is placed by tremie method, concrete is cast to a minimum of one meter above the cut-off level.

Reference

IS: 2911-Part-1-Sec-2