# small piece of wall fell off and metal exposed on exterior



## qmqmqm (May 23, 2015)

Hi everyone.

A small piece of wall fell off beside my garage door. The piece that fell off is about the size of a thumb.

I see that some metal is exposed. Not sure what the metal is for, but it's rusting. Please see pictures enclosed.

Does anyone know what the metal is for?

Does anyone have any suggestions as to the cause of the piece of wall falling off, and how I can do a proper repair? If I just patch the spot with concrete, I'm worried that the metal will just continue to rust underneath...

Cheers!

Paul


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## CallMeVilla (May 23, 2015)

Looks like the rebar (pronounced "ree-bar") in the form used to build your garage.  Rebar always rusts inside walls.  This is a concrete pop, nothing serious.  You can get some Cement-All and patch the pop.  Enjoy Memorial Day and the soldiers who paid for our freedom!


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## joecaption (May 23, 2015)

Just be aware any patch is going to stick out far more then that tiny rusted spot.


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## nealtw (May 24, 2015)

CallMeVilla said:


> Looks like the rebar (pronounced "ree-bar") in the form used to build your garage.  Rebar always rusts inside walls.  This is a concrete pop, nothing serious.  You can get some Cement-All and patch the pop.  Enjoy Memorial Day and the soldiers who paid for our freedom!



I hate to say it but wrong.

Rebar will rust only when air and water can both come into contact with. It should never be closer to any surface than 2" for that reason. When it does rust like this it expands and fractures the concrete.
[ame]https://www.youtube.com/watch?v=peAEMydbJts[/ame]
Drill into the rebar about 2" clean out as much steel as you can and patch the concrete.


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## mako1 (May 25, 2015)

nealtw said:


> I hate to say it but wrong.
> 
> Rebar will rust only when air and water can both come into contact with. It should never be closer to any surface than 2" for that reason. When it does rust like this it expands and fractures the concrete.
> https://www.youtube.com/watch?v=peAEMydbJts
> Drill into the rebar about 2" clean out as much steel as you can and patch the concrete.


 I hate to say it but wrong again.I did ironwork for 12 years when I was younger and all rebar is specked to be 3/4" from the slab edge.


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## nealtw (May 25, 2015)

mako1 said:


> I hate to say it but wrong again.I did ironwork for 12 years when I was younger and all rebar is specked to be 3/4" from the slab edge.



http://www.concreteconstruction.net/concrete/placing-reinforcing-steel.aspx
Minimum concrete cover
For concrete cast against and permanently exposed to earth (such as footings): 3 inches
For concrete exposed to weather or earth (such as basement walls)
#6 bars and larger: 2 inches
#5 bars or smaller: 1½ inches
For concrete not exposed to weather or in contact with ground:
Slabs, walls, and joists: #14 and #18 bars: ½ inch
Slabs, walls, and joists: #11 bars and smaller: ¾ inch
Beams and columns: 1½ inches


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## CallMeVilla (May 25, 2015)

Well, we got a professional "throw down" here !  

Honestly guys, all of us are right to some degree.  While the spec calls for rebar to be 2" away from the outside, we have a situation here where it is clearly closer.  It rusted, it popped the cement.  Now, I was trying to give the happy DIYer some easy ideas without calling in a demo crew.  Drilling out 2" of rebar could be really challenging to Mr. Harry Homeowner.  A simple Cement All fix seemed enough.....

Would it be uneven?  Probably, that is how first time DIYers start to learn troweling skills.
Could it pop again in the future?  Yes, freeze thaw sucks.

Enjoying the give-and-take.


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## qmqmqm (May 25, 2015)

Thanks everyone for the suggestions!

If I simply patch up the concrete, wouldn't the rebar continue to rust inside? Would that cause more problems inside the wall? Or is the rusting process so slow that I shouldn't worry about it?

Cheers,

Paul


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## nealtw (May 25, 2015)

Depends on what it is. If it is running sideways or up and down, this might only be the beginning as the rest of the bar might be as close as this peice. If the foundation turns right there is might be just an end of a peice running into the garage. The video is the only fix I know.


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## slownsteady (Jun 1, 2015)

You can find a rust stopper in spray cans usually on the shelf in automotive stores. Wire brush the exposed spot and spray it with this stuff. It reacts with the remaining rust to stop oxidation. The stuff turns black, so protect your work area before spraying. Then make the concrete repair.


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## mako1 (Jun 2, 2015)

Neal: Not trying to argue here.I was the superintendent  for a ironworking company in FL for 12 years doing the ironwork on many 10-25 floor structures including bridges which included the Sunshine Skyway bridge over Tampa Bay.
 I have to admit that I have never read any code books or papers on either concrete or rebar.Well,maybe a little.
Every job that we did had a engineered set of drawings. And was inspected by a structural engineer so no need to know anything accept to build by the plans for that particular job.I would say that 99% of these structural drawings call for 3/4" clearance between rebar and edge of concrete .Either in slabs,coloumns  or walls.
 Even in this salt water environment .
 Just my experience in the trade.


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## nealtw (Jun 2, 2015)

mako1 said:


> Neal: Not trying to argue here.I was the superintendent  for a ironworking company in FL for 12 years doing the ironwork on many 10-25 floor structures including bridges which included the Sunshine Skyway bridge over Tampa Bay.
> I have to admit that I have never read any code books or papers on either concrete or rebar.Well,maybe a little.
> Every job that we did had a engineered set of drawings. And was inspected by a structural engineer so no need to know anything accept to build by the plans for that particular job.I would say that 99% of these structural drawings call for 3/4" clearance between rebar and edge of concrete .Either in slabs,coloumns  or walls.
> Even in this salt water environment .
> Just my experience in the trade.



Fair enough, we all work from experience. Mine is any concrete work we prepare like footing, foundation, stairs, sidewalks, driveways and now garage floors. Any rebar closer to any surface than 2" will fail by the city and engineers.. We don't have to argue the picture above is enough for me.
There is a reason for epoxy coated rebar in bridges latley???????


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## slownsteady (Jun 2, 2015)

maybe a difference in regulation 'tween the two locations?????


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## nealtw (Jun 2, 2015)

slownsteady said:


> maybe a difference in regulation 'tween the two locations?????



different application, for sure.


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## slownsteady (Jun 2, 2015)

mako1 said:


> ....... including bridges which included the Sunshine Skyway bridge over Tampa Bay.



Arrrgh. Tampa Bay doesn't get mentioned in NY / NJ after last friday.


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## nealtw (Jun 2, 2015)

If we want to talk bridges.
Every year the nation spends about $8.3 billion, directly from the cost corrosion in our national highway bridges.
http://depts.washington.edu/matseed...orcement Corrosion/Bridge-Rebar Corrosion.htm


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## GeselleBrian (Jun 3, 2015)

You don't have to de-rust it, but the reason it's popped off is because it has rusted (kind of contradictory, I know)

The reason is, the alkalinity in the cement prevents rebar from rusting any further--provided  IS still alkaline (cement neutralizes reacting with CO2 in the air).

 The official way to treat something like this is to hammer off all neutral cement until you arrive at cement that is still alkaline enough. Minimum is pH 12, if I'm not mistaken. To test you need indicator fluid.

BUT as this spot is not likely to weaken the statics of your garage, I would just fill it with new concrete.

The neutralization process mentioned is called carbonatization. Happens to all concrete over time, as far as I know.


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