Basically exposed aggregate concrete slabs can be drilled with the right drill without any problems. A minimum output of 800 watts and a hammer drill are important. A hammer drill that exerts a different direction of impact is more advantageous.
Slowly drilling into the exposed aggregate concrete slab from the underside is helpful. A block of wood as a guide, if necessary fixed with a screw clamp, can help. If hammer drilling is switched on, it can be helpful to alternate between switching the hammer mechanism on and off on a hammer drill (€ 80.73 on Amazon *).
Just before the drill emerges from the concrete floor, the pressure should be reduced. It is important that the top of the exposed aggregate concrete slab is not directed towards people or objects at risk. When piercing through, individual pebbles can burst out and fly away at any time.
When drilling exposed aggregate concrete slabs, rejects must always be expected, as the irregularly distributed pebbles can lead to chipping and flaking. If a pebble is "in the way", a new borehole should be drilled.