Why pile chipping is required before the pile cap works

Pile chipping 

            

Why pile chipping is required before the pile cap works

Excavation is done around the pile area so that removes the extra pile portion by chipping. Chipping of the extra pile that is above the cutoff level, which is provided for good and sound concrete. The main purpose of chipping is to remove the surplus slushy concrete (a mixture of concrete, slurry, and mud) over the cutoff level.

When concreting is going on, the black slush comes out from the bored hole. Black slush represents the mud which produced at the time of boring.