Breaking up concrete

[Tiger]

Dear all,

While digging for one of the posts for my gate, I noticed about 250 mm deep that there was concrete. More digging and I could see that it was an old slab. I wanted to put my post to be at least 300 into the ground but the concrete was resilient. First I tried the crowbar,it didn't do much. Then I tried an air chisel, that did even less, then a masonry bit in a hammer drill, that didn't do much either. A jack hammer would do the job but I thought hardly worthwhile for a little bit of concrete.

So my question is for small areas of concrete what do you guys do? Assuming that you don't run out and hire a jack hammer, what sort of tools do you use?

[outback]

A combination of crow bar, elbow grease and sweat.

The good news it it's probaly only 150mm thick max.

When I was a boy I used to dig holes by hand, OK crow bar through solid rock, 900mm deep. :eek: Unfortunately that's not a fib.

[Tiger]

Does your crowbar have a motor in it? Seriously, which end of the crowbar and how heavy. I reckon the slab I've got would be 150 and the crowbar was barely denting it.

[outback]

Use the sharp end, and the only moter it had was the purr of a virile young bloke.
Hang in there, you will fracture the concrete after a little while. Then its all over.

[Tiger]

How about you come and show me and I'll take notes.

[outback]

How about you come and show me and I'll take notes.

Absolutely, no problems. You may not like the remuneration package I have worked out for you, but hey, if your'e happy to pay, I'm happy to break.

[Tiger]

By the way Al, what do you do for a living?

[boban]

Tri-Nitro-Toluene will do the trick. Very easy too.

[ozwinner]

By the way Al, what do you do for a living?

star.

Al

[Tiger]

Well that explains the picture, the years haven't been good to you, my friend. But gee you look a lot like that guy who used to be on tv.

[DavidG]

Go and spend ~$80 on one of those SDS rotary hammer drills (not a ordinary drill which hammers) and drill some holes through it.
Turn the rotary action off and put a chisel in and break it up.


OR

Sit the post on the slab and bolt it down with some bracket dynabolted to the concrete. Possibly the easiest and strongest.

[Bodgy]

Tiger


Suggest you get creative and save the blisters.
You're digging a hole to give a solid foundation to your post. You just hit a 150mm slab which is a far more solid foundation than you're ever gonna make. Us the slab to secure your post. If you intended setting in concrete, rough up and key the slab, maybe drill some holes and shove in 150mm nails, drill reciprocal holes into your posts, concrete a collar around.

Betcha this post will outlast the other.

[glock40sw]

Yep...Go for a SDS Rotary Hammer.

It will give you an excuse to buy a new toy.

Said with big round doe eyes to the old woman...."Honey...If you want the gate up, I really really really need a SDS"


Hooroo.
Regards, Trevor.
Grafton

[davidt]

Tiger,

I'd also use a rotary hammer. I bought the $98 GMC version (with 20ish bits and 3 chisels), and it's a surprisingly good tool. Heavy, but effective.


David

[Tiger]

Any excuse to buy a new toy. Wondering though, what limits are there on these rotary drills? Will they be able to break up a square metre worth of concrete or is it a job for a jack hammer? Have seen rotary drills for around $70 or $80 at Bunnies which were supposedly trade quality, think it was Wagner brand, anyone bought one?