Breaking up old concrete?

[LarryFahn]

What did they use in that stuff back then? I have a 16x16" piece with the remnants of a flag pole in it. I tried a 5lb hammer and stone chisel and it didn't even break the dust loose after 5 blows. I borrowed my buddy's 35lb Bosch jack hammer and only got 4" down in an hour! I was using a point and a 3" chisel. The next project is 10" in diameter and 3 1/2' deep. I'm just going down sever inches and burying this thing too.

It was probably put in the ground in the 30's to the 50's. Wtf makes this so damn hard? A buddy said they used to throw in ash? Any advice on breaking the other one up quicker?

 

[ptgarcia]

When I moved into my current home I removed a commercial quality swing set the previous owner built so I could pour an RV slab. I had the same issue as you so I just broke the posts free of the concrete and pulled them out and hammered a little off the top of the footings then buried them. Now they're under 6" of reinforced concrete.

If you have to remove them it might be less time consuming to dig them out.

 

[bcradio]

Rent or buy a full sized electric jackhammer

 

[Leaflessshadetree]

Concrete hardens with age. Wood does too, ever wonder how they drove nails in them old oak 2x4s? Answer, they didn't, they drove nails in to new oak 2x4s.

Back in the old days people put just about anything in as filler. My old house was built by a blacksmith. When breaking up concrete I'd usually find old horse shoes, metal scraps an chunks of brick.

 

[rlitman]

A 35lb electric demolition hammer has nearly the same impact as a 90lb Bosch Brute rental. Was the point totally blunted (a chisel is the wrong tool to break up concrete), or was it out of oil perhaps?

 

[bcradio]

A 35lb electric demolition hammer has nearly the same impact as a 90lb Bosch Brute rental. Was the point totally blunted (a chisel is the wrong tool to break up concrete), or was it out of oil perhaps?

I guess if you consider 15 ft-lbs nearly the same.

 

[kctyphoon]

A 35lb electric demolition hammer has nearly the same impact as a 90lb Bosch Brute rental. Was the point totally blunted (a chisel is the wrong tool to break up concrete), or was it out of oil perhaps?

I'd have to disagree with this. Bigger hammers are made for thicker concrete, plus the weight of the tool itself has a big impact on what it will do. I've looked at the Stanley hydraulic site at breakers before, and they will give a guide on what size breaker is best suited for concrete thickness.

Op, best thing to do is work from the edges in.. if it's really tough to get through, one thing you can do is undermine the area you're working on. Dig out the dirt under it, this way it doesn't help support the concrete. The thickness and strength of the concrete will determine what you need. I had to break up a piece once that was 10 to 13" thick. Just to get an area big enough to place a utility pole took hours using a 45 lb class hydraulic breaker.

 

[rlitman]

I guess if you consider 15 ft-lbs nearly the same.

Hummm, let's see:

The 35-lb hammer I have:
https://www.makitatools.com/products/details/HM1307CB

25.7 ft-lbs of impact energy @ 1450 BPM.

Bosch Brute:
https://www.boschtools.com/us/en/boschtools-ocs/demolition-hammers-bh2760vc-34552-p/

35 ft-lbs of impact energy, but only at 1000 BPM.
The 35-lb Bosch demolition hammer comes in at 22 ft-lbs. I hadn't considered that my Makita outclassed it a little.

However, all three of these are limited by the wattage you can pull on a standard outlet, and none are all that impressive when you look at my pneumatic little "toy" rivet buster, which is just around 20 ft-lbs at over 2000 BPM, and is well under half the weight of the demolition hammers. I saw that thing take apart a chimney just as easily as its bigger brethren, and you can one-hand it.

Compare that to a real jackhammer:
https://www.diamondtool.net/tamco-p...-1-14-x-6-steel/product/3124/toku pb-90-1-1-4
That comes in at 181 ft-lbs @ 1250 BPM.

 

[rlitman]

I'd have to disagree with this. Bigger hammers are made for thicker concrete, plus the weight of the tool itself has a big impact on what it will do. I've looked at the Stanley hydraulic site at breakers before, and they will give a guide on what size breaker is best suited for concrete thickness.

Op, best thing to do is work from the edges in.. if it's really tough to get through, one thing you can do is undermine the area you're working on. Dig out the dirt under it, this way it doesn't help support the concrete. The thickness and strength of the concrete will determine what you need. I had to break up a piece once that was 10 to 13" thick. Just to get an area big enough to place a utility pole took hours using a 45 lb class hydraulic breaker.

Yes, bigger hammers are made for thicker concrete. I cannot imagine breaking into a 13" thick concrete slab with anything I could man-handle around. That really calls for something on a Bobcat, etc.

And yes, working in from the edges is the best idea. If you start hammering in the middle, the broken pieces have no place to go, and you're going to make a lot of dust with little effect. You want to break off pieces, not break up pieces.

 

[bcradio]

Hummm, let's see:

The 35-lb hammer I have:
https://www.makitatools.com/products/details/HM1307CB

25.7 ft-lbs of impact energy @ 1450 BPM.

Bosch Brute:
https://www.boschtools.com/us/en/boschtools-ocs/demolition-hammers-bh2760vc-34552-p/

35 ft-lbs of impact energy, but only at 1000 BPM.
The 35-lb Bosch demolition hammer comes in at 22 ft-lbs. I hadn't considered that my Makita outclassed it a little.

However, all three of these are limited by the wattage you can pull on a standard outlet, and none are all that impressive when you look at my pneumatic little "toy" rivet buster, which is just around 20 ft-lbs at over 2000 BPM, and is well under half the weight of the demolition hammers. I saw that thing take apart a chimney just as easily as its bigger brethren, and you can one-hand it.

Compare that to a real jackhammer:
https://www.diamondtool.net/tamco-p...-1-14-x-6-steel/product/3124/toku pb-90-1-1-4
That comes in at 181 ft-lbs @ 1250 BPM.

You obviously have little to no experience with these things. There is a reason that these are one of the more common rental tools out there and they cost more than double what a 35lb demo hammer is. If there wasn't a reason for these full size electric hammers, then they would not sell or make them... and yes I own both types (demo hammer and full size electric hammer).

KC knows what he is talking about.

 

[2oolhound]

12 lb sledge hammer busts up concrete pretty good. Use it like a golf club and take full swings with speed and follow through.

 

[06 DIESEL]

If you are trying to break concrete you need a pointed tip not a 3" chisel. Concrete has typically at least 3500 pounds per square foot of strength. The larger area you are trying to break at one the harder it is. Start near the edges and work inward and use a pointed chisel not a 3" chisel.

 

[rlitman]

You obviously have little to no experience with these things. There is a reason that these are one of the more common rental tools out there and they cost more than double what a 35lb demo hammer is. If there wasn't a reason for these full size electric hammers, then they would not sell or make them... and yes I own both types (demo hammer and full size electric hammer).

KC knows what he is talking about.

I've owned both. I sold my Brute. It was a waste of my time.
My Makita (mine is actually an HM-1301, which predates the variable speed trigger) will break up a sidewalk in the same amount of time, and with less strain on my back.

The impact energy is much more closely related to the tool's overall diameter, than the hammer's weight.

Now if you're comparing these to say an SDS-Max (or it's predecessor in spline drive), which weighs no less than a 35-lb 1-1/8" demolition hammer, yeah, the SDS-Max will be an effort in futility in trying to break up a sidewalk. But that is because the tool is too thin to hit all that hard.

 

[rlitman]

If you are trying to break concrete you need a pointed tip not a 3" chisel. Concrete has typically at least 3500 pounds per square foot of strength. The larger area you are trying to break at one the harder it is. Start near the edges and work inward and use a pointed chisel not a 3" chisel.

THIS! And a sharp tip at that. As the tip rounds over (which you'll find on many rentals and old machines), it gets progressively less effective. The moil point delivers all the impact energy into one spot. A chisel spreads it out, and you end up doing nothing. 3" chisels in a machine like that are for cutting asphalt.

3000 PSI is a minimum strength for really cheap concrete after 28 days of curing (4000 PSI is a better grade, 5000 PSI is really good stuff).
But concrete does not magically stop curing at 28 days, and the OP's stuff is probably quite hard by now.

The strength in a concrete is largely in the aggregate, and how toothy it is. Fly ash makes for some strong mix.

 

[bcradio]

I've owned both. I sold my Brute. It was a waste of my time.
My Makita (mine is actually an HM-1301, which predates the variable speed trigger) will break up a sidewalk in the same amount of time, and with less strain on my back.

The impact energy is much more closely related to the tool's overall diameter, than the hammer's weight.

Now if you're comparing these to say an SDS-Max (or it's predecessor in spline drive), which weighs no less than a 35-lb 1-1/8" demolition hammer, yeah, the SDS-Max will be an effort in futility in trying to break up a sidewalk. But that is because the tool is too thin to hit all that hard.

If you are comparing the 35lb hammer to the old gen 1 brute, then yes they are pretty similar in impact energy. However, technology has come a long ways since the 2-3 decades ago that was released. The current gen full sized (which any quality rental house will now have) is much more powerful than a 35lber.

 

[rlitman]

If you are comparing the 35lb hammer to the old gen 1 brute, then yes they are pretty similar in impact energy. However, technology has come a long ways since the 2-3 decades ago that was released. The current gen full sized (which any quality rental house will now have) is much more powerful than a 35lber.

I am, and was not aware of any improvements over the years. Gotcha.

 

[LarryFahn]

Well, I don't know a thing about jackhammers. Just that my buddy gave me his that he uses for breaking up concrete floors for installing radon systems.

I used the point for the majority and started about 6" in from both sides at the corner. That point was about 4" deep and nothing was breaking up. I lifted it out and angled it. The majority of pieces that broke off were only 1"x3" or so. I did work from the outside in expecting to keep chiseling away at it. But I guess I thought it would break off from the vibration and the impact, not just dig in. The point wasn't dull by any means. Believe it or not, I actually make jackhammer bits from time-to-time at my full time job (machinist at a drilling manufacturing company) . Luckily I only used the 3" when I got around the pipe that was in the middle.

Thanks guys

 

[Marctrees]

The MAIN thing to know was mentioned a bit above.

And that is - the piece you are trying to break off absolutely HAS to have free space to break into.

So if this is a typical pole pour in the ground, supported sideways by packed dirt, you HAVE to dig out a bit of dirt around the outside to allow your break pieces room to move away from the main bulk.

Or, MAYBE, at least turn the dirt around perimeter of concrete into sloppy mud w some water jetting and a overnight soaking.

I did jackhammering of sidewalks one summer, and learned that if I did not leverage away the piece I just broke off, the next one would be a bear to even crack.

This is one of the most important fundamentals of doing this work.

And I'm pretty sure its your main problem.

It's not just that the broken piece is hard to remove, it's that it magically like reinforces the whole mass, if it is not totally out of the way, that your next piece will not even hairline crack.

Well, it could hairline crack, but then the subsequent cut will not break at all..

Marc

 

[KnurledNut]

Dexpan.

 

[nikerret]

One of my first jobs I did with my little tractor was helping a guy break up a back concrete pad. He was paying hell, with a sledge hammer. We found getting it slightly off the ground, with the backhoe and hitting it was infinitely better. If the concrete was on the ground, the hammer strike pressure spread through and into the ground. When it wasn't supported, the hammer would apply all the pressure to one spot, creating large cracks and holes.

 

[kctyphoon]

I wish I had a reason to own something like that.. I swear I'd dig holes everywhere..

 

[Dr Stan]

Find some one licensed to use explosives. Drill holes per his/her specs. Fill with C4, cover with at least 2ft of dirt and turn the concrete into stones. Shovel out with a small backhoe.

 

[slip knot]

I'll bring some of my guys over. Just tell them not to do anything to your concrete, don't touch it, don't walk on it, don't even look at it. Then go to town for a few hours. When you get back, I can guarantee your concrete will be broken up, most of it will be missing and what isn't missing will be unrecognizable as anything concrete.

They will work for beer and chips.

 

[LarryFahn]

One of my first jobs I did with my little tractor was helping a guy break up a back concrete pad. He was paying hell, with a sledge hammer. We found getting it slightly off the ground, with the backhoe and hitting it was infinitely better. If the concrete was on the ground, the hammer strike pressure spread through and into the ground. When it wasn't supported, the hammer would apply all the pressure to one spot, creating large cracks and holes.

This I fully understand.

 

[FMC1959]

I wish I had a reason to own something like that.. I swear I'd dig holes everywhere..

Sorry to sidetrack for a moment...but just wishing you had one, is reason enough to me. I got the same one 9 years ago, best toy ever! Sell your pick and wheelbarrow! For small to larger landscapping, putting up a fence, removing smaller trees, digging for a deck, shed concrete slab, moving earth, stone dust, larger gravel....once you have one, you will find tons of things to use it for. Oh, it also cuts grass and removes snow (plow or snow blower). Like a Swiss army knife.

(The bachhoe has amazing strength, straightening sagging fence posts is a breeze)

 

[barnee]

I'm breaking up a 16 by 20 4" slab this weekend that was likely poured in the 40's or 50's. Using a tracked bobcat/loader and will get under it and pop it in pieces. If that doesn't get it Ill hit it with a 20lb sledge after I lift it up a bit.

 

[Al Borland]

I broke up my 1940s sidewalk (6" slabs, 3'x3') a few years ago. I pried each section partly up, propped it up and dropped a section of the concrete (50 lbs or so) on the center of each section.

 

[PMD1966]

My wife complained about a cracked sidewalk at one of our previous homes. I jokingly told her if she broke it up, I would put in a new one. She agreed. I bought her a 16 pound hammer and tried to tell her how to use it. Let the hammer do the work. She had her own ideas. Told me to shut up and get out of the way. She did finish the job. The next day she couldn't get out of bed, thought her back was broken and she was paralyzed. Just some strained muscles. I still tease her about it 20 years later.

 

[ryan20021982]

Why not rent a saw and cut score lines so when it does break they are manageable pieces, I have removed a few good size slabs and we always cut first with wet saw.

 

[Rory Bellows]

Drill some holes in it and it should break between the holes.

 

[nes999]

I would use a 90 pound pnumatic jack hammer. I have chipped out concrete thicker than I am tall. After using pnumatic and electric there isn't any comparison, pnumatic wins all day long.

Sent from my VS985 4G using Tapatalk

 

[LarryFahn]

While I definitely appreciate your help, this isn't a sidewalk where I can pry it up and hit it. A buddy tried to move it with his mini excavtor and it didn't budge an inch. I'm not sure how deep in the ground this piece was, but the new project might give me a clue.

In between our property and the neighbors was a pole we agreed to take it out. The truck pulled it until it cracked and bent. It was still an inch above the ground and we noticed that it moved 2" or so. This thing was concreteted in also but the concrete was poured into an old cast pipe they'd use for road work. I tugged on it with the strap and we dug around it. It's 10" in Dia. This thing is buried 3 1/2 feet deep. This was probably a clothes line. Im determined to remove this pos all together.

 

[LB-1911]

While I definitely appreciate your help, this isn't a sidewalk where I can pry it up and hit it. A buddy tried to move it with his mini excavtor and it didn't budge an inch. I'm not sure how deep in the ground this piece was, but the new project might give me a clue.

In between our property and the neighbors was a pole we agreed to take it out. The truck pulled it until it cracked and bent. It was still an inch above the ground and we noticed that it moved 2" or so. This thing was concreteted in also but the concrete was poured into an old cast pipe they'd use for road work. I tugged on it with the strap and we dug around it. It's 10" in Dia. This thing is buried 3 1/2 feet deep. This was probably a clothes line. Im determined to remove this pos all together.

Consider getting that mini excavator back over - and dig it out / drag it out of the hole.

Good Luck

 

[kctyphoon]

Just wondering how you've been making out..

 

[LarryFahn]

Just wondering how you've been making out..

The first one (that actually got the jackhammer) was broken down 4-6" below ground level and the sawzall was used to cut out the pipe. It was covered over and grass was planted.

The one that's 3'+ deep- We haven't been working on since Tuesday night since the temps were in the 90's and other things arose. I know how we're going to get it out, but like everything else, it will take time.

 

[LarryFahn]

I pulled out the clothes line 2 weeks ago Fwiw. It was buried 4'+ with concrete, bricks and stone around a 4" pipe creating a 12"-18" diameter, 3' long. The last 12" were the pole only. I got it out with the truck but it took about an hour or so. I'd say it's 300lbs +/-

 

[LB-1911]

I pulled out the clothes line 2 weeks ago Fwiw. It was buried 4'+ with concrete, bricks and stone around a 4" pipe creating a 12"-18" diameter, 3' long. The last 12" were the pole only. I got it out with the truck but it took about an hour or so. I'd say it's 300lbs +/-

Thanks for the update - The day that was installed they were probably laughing about it coming out some day.

 

[Milton Shaw]

The worst breaking up concrete story I heard happened in Hollywood. A guy wanted to remove a concrete tennis court from his property that was once owned by a movie mogle in the 20"s. They started breaking it up and it didn't want to break. They eventually found out that the concrete was over 10 feet thick. I guess the original owner worried about cracking and California earthquakes and wanted it never to crack. I busted up 11 yard pour of my driveway with a bobcat and hydraulic breaker, it was over 4" thick and it broke very nicely. I broke it all into pieces no bigger than a double fist and buried it on my property as fill under gravel parking area. Both ankles were very sore for several days after that from all the foot work required to move the hammer and keep breaking it up.

 

[mike93lx]

The worst breaking up concrete story I heard happened in Hollywood. A guy wanted to remove a concrete tennis court from his property that was once owned by a movie mogle in the 20"s. They started breaking it up and it didn't want to break. They eventually found out that the concrete was over 10 feet thick. I guess the original owner worried about cracking and California earthquakes and wanted it never to crack. up.

BS. That would be over 800 yards of concrete. Sorry not buying that

 

[Firebrick43]

One of my first jobs I did with my little tractor was helping a guy break up a back concrete pad. He was paying hell, with a sledge hammer. We found getting it slightly off the ground, with the backhoe and hitting it was infinitely better. If the concrete was on the ground, the hammer strike pressure spread through and into the ground. When it wasn't supported, the hammer would apply all the pressure to one spot, creating large cracks and holes.

Hard to tell but if the backhoe is three point mounted (opposed to subframe mointed) that is a good way to bust the top of the rear end housing off. I have seen around dozen kabotas end up this way as well as a ford and a sub compact or two John Deere. Don't really know if the kabotas are weaker in that regard or just they have sold so many more of them packaged with 3 point backhoes? If mounted to a subframe it takes the stress off the tractor.

Even 100 hp tractors get the **** beat out of them with 3 point backhoes, just its typically the lift arms and draft control rods.