The concrete placing shall not proceed if density of fluid near about the bottom of borehole exceeds 1250 kg/m3.
Determination of the density of the drilling mud from the base of the borehole shall be carried out by taking samples of fluid by suitable slurry sample approved by the engineer in charge, in first few piles and at suitable interval of piles thereafter and the results recorded.
After flushing is completed, tremie head should be removed and funnel should be attached to the tremie pipe.
The slump of the concrete will be maintained at 150 mm to 200 mm.
Concreting operation will be carried out using the 200 mm diameter trmie pipes.
Initial charge of concrete should be given in the funnel using a plug. Total concrete quantity in the funnel should be more than the volume of the entire pipe plus free space below the tremie. This will ensure a water tight concrete pouring through tremie.
Lifting and lowering is repeated keeping sufficient concrete in funnel all the time. As the concreting proceeds the tremie pipe are to be removed one by one, taking care that the tremie pipe has sufficient embedment in the concrete until the whole pipe is concreted. Sufficient head of green concrete shall be maintained to prevent inflow of soil or water in to concrete. Placing of concrete shall be a continuous process from the toe level to top of pile.
The concrete is poured in the funnel. As the concrete reaches the top of the funnel, the plug is lifted up to allow the concrete to flow corresponding to the placing of each batch of concrete.
The concreting of pile is to be done up to minimum of 300 mm above the cut off level to get good and sound concrete at cut off level.
After completion of concreting tremie, funnel and other accessories are to be washed properly and kept greased in proper stacking condition near next pile location.
While doing under water concreting 10% extra cement over and above the design mix requirement should be added in each batch.