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. :D
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 :D

[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. :D

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?

[journeyman Mick]

I'd drill some 12mm holes, pour in some epoxy patch ar chemset and drive in some starter bars (lengths of 12mm reinforcing steel. Pour your footings on top of that and it will never move.

Mick

[Harry72]

Dig the area out enough to get a real hammer in there, start swinging!
Do you own a sledgey?

[Gingermick]

Yes a 15lb hammer will make short work of 150 slab. But let the hammer do the work, otherwise you'll end up busting your back.

[Iain]

Get a few attractive young females, a couple of sledge hammers and wait for the young blokes to try and impress them with their feats of strength :D
I did that once when I needed some wood split at a youth drop in centre.
Wood was hard as nails and the splitter was bouncing off it, young sheilas were watching and the young bucks came out to 'show how it was done'
The power of vanity.

[Velophile]

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.

I'm with Bodgy on this one.

Your post hole is 250 of 300mm.
Sound like a lot of work to gain 50mm. Key your post &/or post foundation into the buried slab.
Job done, have beer.

[outback]

When I was aboy, 300 wasn't deep enough for a fence post, let alone a gate post. I'd bet Al's left knacker, of which he has two :eek: , it will sag real quick.

[Iain]

Al's left knacker, of which he has two.
:D

[echnidna]

When I was aboy, 300 wasn't deep enough for a fence post, let alone a gate post. I'd bet Al's left knacker, of which he has two :eek: , it will sag real quick.

Right on Outback,
Fenceposts need to be 500mm deep and gateposts 600mm deep.
Cheat by digging a shallow hole and you will be doing it all over again in a few months.

To dig through a slab.
Clean out the hole.
Drill around the perimiter of the hole with 1/2" or thereabouts bits and a hammer drill. (Good way to use up a few elcheapo masonry bits)
The guts will then smash out very easily with a crowbar.
Finish digging hole.

[glock40sw]

:D

How did I get dragged into this????

My nuts are fine where they are (Not burried).

Hooroo.
Regards, Trevor (Richard Nixon voice on) "I am not a Squirrel".
Grafton

[Velophile]

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?

Did you finish your post hole?

I just rembered, I have a Roto-Hammer that could do the job for you. You're in Melb? Cheap hire rate, ie beers.

[Timmypig]

When I was younger and sillier I was an assault pioneer in the Army. In the 2 decades since then I forgot how bloody hard breaking up slabs, or going through rock can be ....

I had to break up a modestly sized but depressingly thick slab 18 months ago so I hired an electric jackhammer from Kennards. It took my twice as long as I thought it would and I was so knackered I was ill. But the job was done at least twice as quickly as any other method would have taken.

Good luck Tiger!

[Tiger]

Thanks, Velophile

I finished the job a few days ago. Your tool would have been handy but I'll remember it for next time. How many beers do you charge for use of your tools? I'm not much of a drinker, and when people bring me beer etc. my wife takes care of it.

[Iain]

That could have been phrased a lot more carefully, consider the edit key :D :D :D

[Tiger]

Iain,

Which part are you referring to the tool or my wife.

Anyway my keyboard doesn't have an edit key, looks like I'll have to upgrade again.

[Iain]

I think I shall pass on that :rolleyes:

[Toby]

If all else fails, call Australia Mail their experts in breaking things