Shooting nails into concrete

I am confused as to what happens when concrete nails are shot into concrete with nail shooting guns. Why don't the nails get bent? Where does the concrete that is displaced from the hole, go? Why would the incompressible nail hold in incompressible concrete and not fall out of its hole?
i

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1) Concrete is not incompressible. It's somewhat porous, and will crush under the insertion force of the nail.
2) the nail is not incompressible, at least in the sense you suspect. It will be shrunk in diameter as it's forced into the hole it's making. But because it is somewhat elastic, it will still present significant expansion force in the hole.
3) it doesn't bend because it is driven in very straight. A column is a strong form.
Sometimes power nails do bend, and sometimes even curl out of the work and go flying.
LLoyd

Ignoramus677 wrote:
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Concrete is less compressible than wood, but not incompressible

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The nails are heat treated, so are far more robust than are common nails. The high speed appears to allow the nail to go where they otherwise wouldn't, but it's not fool-proof. I use one of the simple Remington power hammers for nailing to concrete and have had mixed results. Occasionally you'll hit a rock that is so hard the nail won't go to prescribed depth, or it hits nothing but soft rock or sand it will go too deep. Nailing through an electrical knockout with a stronger charge often helps control the depth. If nothing else, it provides a larger area for the nail head to insure the board stays where intended.
I don't subscribe to the theory that concrete is incompressible. It has a given amount of air space by its nature, and is rarely stronger than, say, 4,000 psi in compression, and generally not that strong. I get the idea that the nail, driven at much higher pressure than that, easily compresses the concrete in the proximity of the nail. When you get the desired results, the nails hold quite well, so I can't help but think I'm on the right track with my thinking. Do bear in mind you're talking to a high school graduate with no mathematical training, and no engineering schooling. It will be interesting to hear from those in the know.
Harold

Apart from the other answers it may also be down to the strain rate sensitivity of the nail material. Although I don't know much about it its basically that under a high rate of strain the material may behave as though it stiffer than you would normally expect. This was mentioned to me regarding armour piercing shells and the like.
Ignoramus677 wrote:
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| I am confused as to what happens when concrete nails are shot into | concrete with nail shooting guns. Why don't the nails get bent? Where | does the concrete that is displaced from the hole, go? Why would the | incompressible nail hold in incompressible concrete and not fall out | of its hole? | | i
If the concrete is a day or two old you can use a regular carpenter's hammer, and for the next three weeks or so a power nailer will do just fine, but after a few years you'd likely be better off boring holes. That's pretty much been my experience, but YMMV.

carl mciver wrote:
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Yeah, you ain't kidding! I have some of the hardest concrete I've ever seen. Powder-actuated nailers do NOTHING to this stuff except chip the surface a little. This place is now 30 years old, and the aggregate is all Jasper, a round, reddish rock that is slightly less hard than diamond, apparently. Carbide drills bounce off it, and follow a meandering path between the jasper rocks. If you want to set an anchor in it, you have to stop drilling every 30 seconds, squirt water to remove the dust, figure out which piece of stone is deflecting the drill and smash it with a star drill and a 5 Lb hammer, and then drill a little more. It is a royal pain. I've even been trying to make my own diamond core drills to make anchor holes less than an all-day project PER HOLE! (Some people have said to rent a Hilti or Bosch professional-grade drill, and I will have to try that the next time I need to mount something on the wall.)
Jon

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I've power-nailed into 5 year old Spancrete without trouble.

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Dave, I go ya one better. We re-modeled a thirty year old poured-in-place, three story IBEW building into a computer programmer's office farm. Power-nailed all the plates. No problems, but we did have to use heavy loads.
The bigger problem was core-drilling all the beams to route network wiring!
LLoyd

Had that problem in an old school building. Had to put in the anchors for a drop ceiling, Ended up drilling every one. Karl
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As others have stated, the nails are heat-treated for this specific application. Don't try it with common bright nails. Older concrete does tend to spall or shatter, making hole-drilling preferable. A rotary hammer is then the preferred tool. I once had to mount PT 2x4 to steel pipe (approx. 1/4" wall) that appeared to be used drill stem. As long as I used the heaviest loads, a washer to limit penetration and hit the pipe squarely, it would secure the 2x4 to the pipe in order to mount a gate latch. There was nowhere else to go - the existing gate ended at the pipe and the pipe was at the corner of the fence line. It worked fine with about 1/2" penetration.
On Fri, 19 Aug 2005 17:13:50 GMT, Ignoramus677
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I own a Mosin Nagant rifle, and it easily shoots holes in railroad tie support plates (about 1/2").
i

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Mine's a Remington. Drills real pretty .30 holes in those plates. Kinda noisy, though... :)

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I love it, it cost me just $70 and shoots relatively well and has mild recoil. It is a finnish M39.
i

On Sat, 20 Aug 2005 03:28:11 GMT, the opaque Ignoramus677
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Good price! Here's a link to a MN site with lots of info. http://www.surplusrifle.com/russianmosin189130/index.asp The Huber ball trigger mod looks like a good idea, and that Vulcan V50 rifle on his page looks like fun.
I've been thinking it might be time to get one of these long guns to replace Grandpa's old single-shot, bolt-action Winchester 22.
Oregon just outlawed my sinus medicine (It now takes a doctor's visit and a prescription to get Tylenol Allergy/Sinus medicine) and with the threat of Homeland Security, the political climate is ominous. Ayup, we civilians will need more personal security and protection.
What do multiple case lots of 7.62x54 cartridges for that baby cost?
----------------------------------------- Jack Kevorkian for Congressional physician! http://www.diversify.com Wondrous Website Design ================================================

I was on a siezmic upgrade to a control tower and when I saw how they put the cladding on the outside I stayed well away. The nails they used pierced the columns and 3/8 wall tubes like nothing. I was told that if the shot is not square they will shoot the nail sideways which could kill a bystander. Concrete nails also make good divider and trammel points. I have brazed them onto my large homemade dividers. Randy
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Randy Zimmerman wrote:
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In the High school in Arlington Texas - oh maybe in 70 or 75 - sometime in there - they replaced the 'old' lights with the long tube lights to save money.
A week after Christmas break the lights began to tumble down. On top of students.
It seemed the standard load on the 22 shell nail guns wasn't set for the very old and very hard concrete.
So it seems those that do it simply best pick the correct load or get the job over.
No telling who paid for it - insurance maybe.
Martin