Cutting a hole in thick concrete slab

[Donkmeister]

Further to my earlier thread on digging a manhole, I have taken the advice onboard about finding an existing pipe to attach an access chamber to instead (definitely better than a 7-foot deep manhole!!!)

Currently investigating the route of the drain from an existing gulley. The gulley is surrounded by a concrete slab approx 7-8 inches thick (measured by drilling through it with a long SDS bit).

I have cut the outline with a 9" diamond disc to try and contain break-out but I'm stumped with breaking out the middle. I tried drilling a load of 20mm holes and chiselling out with an SDS scutch, but the concrete is bl**dy good stuff! It is possibly 91 years old, and has absolutely no spalling or cracks despite its age. It literally killed the abrasive-type grinder disc I tried at first. No rebar though.

So, I've come up with a few ideas on how to break out the middle without smashing everything else up:

1) Attack with a pick-axe
2) Attack with a sledgehammer
3) Rent a diamond chainsaw

Any ideas?

Is there some sort of wedge I can use? You know, drill a hole with SDS, place wedge in hole then batter with 14lb hammer until concrete splits/explodes?

 

[noseall]

Why are you mucking about with something as resilient as aged concrete - use an electric heavy duty breaker.

 

[Mikest]

A breaker should help you out mate, around £60 to hire for a week

 

[coliholic]

Hire a couple of Polish lads, twenty quid each a day, sit back and supervise.