Concrete Coring Machine

Yes. Coring bits are diamond encrusted and will cut rebar, but cutting rebar in the floor can lower the floor load rating according to some building codes.

Yes it can & very well- depending on the placement and thickness of the rebar, it often only shows up as a reduction in the drilling rate of about 50%. In my younger days I worked on a job were we cored a number of 10" holes in a hospital, about 6 floors directly over each other. Turned out that we'd cored through concrete beams on several of them, and nicked or severed rebar! We won't get into the "discussions" as to responsibility that followed, but suffice it to say that it was an expensive fix all around.

Note that it will also go through electrical conduit like butter, but that's another story!

I want to core a number of holes, around 2" diameter and 2' depth at pile caps with dense reinforcement.

As I need to construct concrete plinths for tower crane. I believe the extra structure can counter-balance the cutting of rebar.

Do you have any idea how many holes can a boring machine finished per day?

Anybody knows?

Thanks

A typical floor mount rig (115 VAC, 15/20A rating, with a good power supply, good quality bit in decent shape) can bore a 2" hole 1' deep in medium strength concrete, including punching through 6x6 reinforcing wire, in less than 5 minutes if you don't have to worry about where the water goes. I would allow another 2-3 minutes for every bar you have to cut through.At 2' you're going to have stop & clear the core out, drop the bit & throw on an extension, and you'll probably find your cutting rate slows with more hole cleaning & higher amp draw on side drag. So let's say 15- 20 minutes per hole including a couple of bars, plus 5 minutes setting up & anchoring the base (these are all vertical straight down, right?). If the existing concrete is relatively smooth & flat, a vacuum base will shave a couple of minutes off that.

Now- if you have to put these holes exactly were they have to go, and if there is rebar there you have cut through it then you need a diamond core. If you have a bit of flexibility-even to just angle the hole a bit if needed, I would recommend a cruciform bit on a large SDS or similar demo hammer. These won't damage bar, and once you're done you have a clean hole the depth you want- with no set up time! I'd imagine one guy can drill all the holes you want in a day!!

Like everyone else has said...

What grout will you be using to set your starter bars? I have a similar job in hand now. Just want to compare notes if that's ok....

Make sure the slab is not a PT (Post-Tension) slab. The coring process will cut through everything (mentioned previously) including the PT cables which has devastating results. X-ray the slab if electrical or data conduits are critical as replacing/re-routing these can also be a can of worms.

Yes you can drill into concrete if the drill bit is diamond encrusted, and in most cases it will cut through rebar as others before me have stated.

BUT, why would you want to do so? It is never a good idea to cut through reinforcement steel, which will weaken the load carrying capacity of the structural element, thus hastening it's failure.

Do some intense planning where you want to place the new rebar in the existing concrete element. This means employing an ultrasonic rebar locating device so that you can miss the rebar while drilling.

The Law of the 6 P's that I learn in the Army Rangers: Proper Planning Prevents Piss Poor Performance.

Learn it, live it, adhere to it.....

I figured it wouldn't be long till you noticed this posting Moosie.

Cutting thru rebar for starter bar insertion had me wondering too.

OP did say that the starter bar locations were "fixed" so it sounds like he/she has a site specific limitation/constraint to contend with. Most probably introduced by an architect.....

Hope OP can tell us a bit more about the job.

Happy Pagan Festival mate.

Yes it would help giving us more details....

Where are the Druids when you need them!? LOL

Merry Christmas to you as well friend! [somehow I don't think you'll find any real Christmas trees where you're at...... ;-) ]

Answer is: If you don't know (by X-ray or some other technique) exactly where every bit of metal (PT bars, rebars, beams, etc.) and can avoid them, I urge you to re-think this project and go around, i.e. put what ever pipe or installation on the outside of the structure (with its own structure), if you are not already in the stratosphere within your existing structure. I am not the expert, but I should think that cutting the wrong thing could bring down the whole entire sand pile.

OP's not coring penetrations he is coring concrete for insertion of starter bars for connecting additional structural reinforced concrete elements.

You're right on the visions of collapsed sand piles....

"xray" surveys (radar really) would be ideal, however, the apparatus may not be readily available at the OP's locale...I have this limitation at present.

So what to do?

Thankfully the placement of steel in RC is reasonably predictable and careful planning can get a hole threaded past the steel (unless you snag a hooked rebar end at the spot one is drilling). A small diameter masonary drill bit is handy for drilling feeler holes to determine exactly what line the rebars take....stirrups are hard to avoid. Sheer pins are another pain.

OP hasn't explained why the starter bar hole locations are so "fixed". I wonder what he is building?