The following precautions should be taken while working during tremie concreting:
- Concrete should be consistent, rich in cement (not less than .) 370kg/m3) and a drop between 150 and 180 mm.
- When concreting under water, a temporary cover should be installed to the full depth of the bore hole or 2 square meters In a non-collapsible layer so that pieces of ground do not fall from the sides of the hole into the concrete as it is laid. Temporary casing may not be required except near the top when concreting under drilling mud (bentonite slurry).
- The hopper and trellis must be a closed system embedded in the laid concrete, through which water cannot pass.
- The tremie should be large enough to take into account the size of the aggregate. For 20 mm The overall size of the tremie pipe should be diameter 200 mm. not less than, Aggregates of size greater than 20 mm shall not be used.
- The first charge of concrete must be placed with a sliding plug that pushes down the tube next to it or with a steel plate of sufficient charge to prevent mixing of the concrete and water. However, the plug should not be left as a lump in the concrete.
- Tremi pipe should always penetrate the concrete well with a sufficient margin of safety against accidental ejection of the pipe for the discharge of concrete.
- The pile should be completely concreted and the method of deposition should not be changed over the pile to prevent accumulation within the pile.
- All Tremi tubes should be thoroughly cleaned after use.
- Generally the concreting of piles should be seamless. In an exceptional case of interruption of concreting, but which can be resumed within 1 or 2 hours, the tremie shall not be pulled out of the concrete.
Instead, it should be raised and lowered slowly from time to time to prevent the concrete from freezing around the tremie. Concreting a. should be resumed by introducing slightly enriched concrete with approx 200 mm. decline of For easy displacement of partially set concrete. If the concreting cannot be resumed before the final setting of the concrete then the pile may already have been put in place, so the cast may be rejected or accepted with modifications.
- In case of either accidentally retracting the tremie from the concrete or to remove a choke in the tremie, the trammie can be restarted in the following manner to prevent impregnation of the laden or scum lying on the concrete deposited in the bore: Is.
The tremie will be lowered gently over the old concrete with very little penetration initially. A vermiculite plug should be installed in the tremie. amidst the slump of fresh concrete 150mm and 175mm should be filled into the trammie which will push the plug and exit the tramy displacing the lattices/scum. The trellis will be further extended in steps allowing the fresh concrete to remove the latent/scum in its path. Concreting can be resumed when the trellis has been pressed down to about 60 to 100 cm.
- In the case of concreting by means of tremie or such tubes which are subsequently withdrawn, the concrete should be placed in sufficient quantity to ensure that the soil and water or bentonite slurry are prevented from flowing during the retraction of the tube. Adequate top of concrete should be maintained for ,
- The top of the concrete in the pile should be brought above the cut-off level to allow the removal of all latent and weak concrete prior to capping and to ensure good concrete at the cut-off level for proper embedding in the pile cap.