For bored or driven cast-in-situ piles, concrete shall be deposited in such a way as to preclude segregation. Concrete shall be deposited continuously until it is brought to the required level. The top surface shall be maintained as level as possible and the formation of seams shall be avoided.
For under-reamed piles, the slump of concrete shall range between 100 mm and 150 mm for concrete in water free holes.
For large diameter holes concrete may be placed by tremie or by drop between bucket; for small diameter boreholes a tremie shall be utilized.
A slump of 125 mm to 150 mm shall be maintained for concreting by tremie. In case of tremie concreting for piles of smaller diameter and length up to 10 m, the minimum cement content shall be 350 Kg /m3 of concrete. For larger diameter and /or deeper piles, the minimum cement content shall be 400 Kg /m3 of concrete.
Concrete to be used in bored or driven cast-in-situ piles shall have a strength greater than 20 Mpa and a minimum cement content of 400 Kg /m3. For such piles not exceeding a depth of 6 m, where underwater concreting is not involved and where soil conditions are favorable and nonaggressive, the concrete strength may be 15 Mpa with a minimum cement content of 350 Kg /m3, provided that a higher strength concrete is not needed from structural considerations.
For concreting under water, the concrete shall contain at least 10 percent more cement than that required for the same mix placed in the dry. The amount of coarse aggregate shall be not less than one and a half times, nor more than two times, that of the fine aggregate. The materials shall be so proportioned as to produce a concrete having a slump of not less than 100 mm, nor more than 150 mm, except where plasticizing admixtures is used in which case, the slump may be 175 mm.
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