What's this in my slab?

[JoeMal]

So I'm attempting to bore a hole in my slab to anchor a safe....I've made it about .5" and notice this...stuff. What is this? I suppose it could be rebar? Why is it so close to the top of the slab?

Should I abort and try another anchor point?

ETA: My finger looks very strange in this picture

 

[Resist Evil]

Looks like bits of stone from what I see. It should be OK to drill your holes and set your anchors.

Are you using an actual hammer drill or a vibrating-type "hammering" action that can be found on a homeowner-level drill? The hammer drill will batter through the stones with ease, while the vibrating drill will require a very good bit and patience while the bit grinds it way down. Either will get the job done, in my experience.

 

[Magoo]

Rebar and re-mesh aren't always so carefully placed (and kept in place) for pours. The fellas that pour slab houses are, in my experience, much more about quantity than quality. I did construction inspection for quite a while and you don't want to know the stuff I saw . I can say I'd never buy a slab house unless I personally oversaw the foundation work though.

 

[thefish]

What does it feel like if you scrape at it? Metal, stone, plastic?

If plastic and you have a bathroom on that level it could be sewer or waste.

 

[twofifty]

Plan B

If the safe absolutely has to go there, could you switch to plan B and epoxy a 1/4" steel plate to the slab, onto which you would have pre-welded some suitably sized hex nuts in the safe's hole pattern?

Glue the plate to the slab, move the safe into position then bolt it down. Bolt length would be to be just right. Plate might need spacers to support safe bottom flush with hex nuts.

 

[btg3]

Got a magnet? Perhaps steel conduit for electrical.

 

[BigBL87]

Really difficult to tell from the picture. My first guesses would be rebar (I've seen some very haphazard jobs of laying rebar, my recent sidewalk a prime example), conduit for electrical as someone else said, or even a water pipe of some kind.

I'd definitely try a magnet and a non-contact voltage tester to see if it's metallic and/or conduit.

 

[romulus]

Judging by the color and irregular shape, it looks like aggregate that has been exposed by the drilling. If you are going to drill concrete, you will encounter aggregate, it's virtually impossible to avoid unless its a really bad mix with inadequate aggregate content - i.e. pure grout. Rebar exposed by typical hammer drilling will shine, and WWM often goes unnoticed as it's fairly easy to drill through. This is just base on the picture and the lighting, though.

 

[SAGEEN]

they add gravel to concrete for filler I think just hammer drill into the hole and place your hardware ect.

 

[wild willy]

Its the stones in the concrete just drill thru it.I can't believe nobody here hasn't ever mixed or poured concrete

 

[medalguy]

The stone in concrete is collectively called aggregate. Its purpose is more strength than a volume expander. No aggregate = weak concrete. Good hard aggregate = hard concrete.

What I'm seeing looks like aggregate but a pic is hard to tell for sure. Check to be sure it's not metal or plastic, then drill through it. As recommended, use a real hammer drill with a good carbide drill. In my experience you may need 3-4 drills for a good safe installation if you have good concrete. Rent one if necessary or borrow one. It's a small cost compared to the strength of your safe installation.

 

[FastCut]

Hit the local home Depot for professional hammer drill. I drilled an 1 1/4 hole through my foundation wall for some conduit to connect my inlet box for generator and it took only a minute. I had never used a real professional hammer drill and it really shocked me how easy this thing went through my wall (8 inches of poured concrete). Finish on the hole was perfect, almost like drilling metal. I also drilled some smaller holes in my patio slab for bonded in anchors to secure my generator when in use...apparently some people think they can just borrow yours without asking.

I just wanted to state that I rented unit for about $35 for half day. Work with this unit only took about 10 minutes actual drilling and assembly time.

 

[hartcreek]

Just aggrigate.....what do you think concrete is? It is portland cement and aggrigate wih some reinforcing steel bar.

 

[batex]

Could be a hole that was drilled and then filled for termite treatment. Actually is pretty common.

 

[Fatdaddy]

Looks like rock from where I'm sitting...like someone else said, a good hammer drill like this: http://www.professional-power-tool-guide.com/wp-content/uploads/2008/08/bosch-rotary-hammer.jpg makes a world of difference. You have any contractor friends?
Or a friend in a Maintenance dept. somewhere that you could borrow one?

 

[HellTrain]

Just keep drillin. Don't look like conduit to me. If it's rebar, it's no big deal to drill through it, just takes longer even with a rebar eater. To me it just looks like stone from the concrete mixture