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  • Building a small rebar cage - weld it?

    I need to build a small rebar cage (about 2x2x3 feet) for a concrete foundation and have a Millermatic 175 MIG welder. Seems welding it would make it more solid and easier to handle.

    Pros and cons of welding it together vs using rebar ties?
    Perticular type of rebar needed, or can I just use the stuff from a big box home store?

    Thanks in advance!

  • #2
    For me, it would depend on whether or not it would be inspected. If it will be, then it must be tied unless specifically instructed in the plans to weld. That would be the first consideration. I have inspectors make me take sections out where electricians have welded ground lugs to the bars. They do not like the heat at all. On some jobs, we aren't allowed to even have a torch on the job much less use one.

    As to rebar, weldable bar will have a W suffix on it. Most rebar is not weldable per the rules. It will weld to be sure as I have done it a million and a half times. It won't however be an approved method on anything except W suffix bar. The box stores will not have the right bar for welding. My rebar supplier wouldn't even have it..he'd have to order it. It is NOT cheap either. http://www.dot.state.il.us/materials/rebarguide.pdf Start on page 4 and ytou will see examples of the W suffix.

    I say just tie it and be done with it. You can tie it much faster than welding anyway, any day.
    Don


    Go Spurs Go!!!!!!

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    • #3
      Tying is the norm and is generally accepted. The rebar and the concrete kind of work together to form a finished product like fiberglass cloth and resin. Welding the rebar would be akin to sewing all the fiberglass strips together before adding the resin. I know some high performance boats have sewn cloth, but it's definitely the exception.
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      • #4
        Depends on how critical it is, I have tacked a lot of it together for rather rudimentary work, does make it nice to handle.
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        • #5
          Main thing to remember when welding re-bar is not to cool the hot welded joints with water & you should be good to go.

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          • #6
            Originally posted by old skool View Post
            Main thing to remember when welding re-bar is not to cool the hot welded joints with water & you should be good to go.
            Crap.

            In case the reply is too short, I should type "Crap" and maybe the bot will take it.
            --- RJL ----------------------------------------------

            Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
            -------------------------
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            • #7
              Just tie it. All you need is tie wire and pliers. If it's a decent job you should be able to climb on it.


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              • #8
                I've been told (can't say for sure) that you shouldn't weld rebar to use in concrete.
                Thermal Arc 185

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                • #9
                  You can if its designed for it and uses the correct bar. I have done it many times. Some bars must be welded. #32 bars for instance. You overlap two 4" plus bars and you have a huge mass of steel to encase. They are usually butt welded together in columns and the like.
                  Don


                  Go Spurs Go!!!!!!

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                  • #10
                    I mean that just not cooling with water and you're good to go is nonsense. You can get brittleness even without quenching if it's not a weldable grade of rebar.
                    --- RJL ----------------------------------------------

                    Ordinarily I'm insane, but I have lucid moments when I'm merely stupid.
                    -------------------------
                    DialArc 250 (1974), Idealarc 250 (1971), SyncroWave 250 w/Coolmate 3, SP-175+, TA 161STL,
                    Lincwelder AC180C (circa 1952), Victor & Smith's O/A, Dayton (Miller) spot welder, 1200 sq.ft. of garage filled with crap and a kid that can actually run the stuff +++

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                    • #11
                      Typical overlap for most applications is 40 bar diameters.
                      Don


                      Go Spurs Go!!!!!!

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                      • #12
                        Don't weld it. Not a good idea. Tie it together with wire

                        I have an old Italian friend who is retired from the cement trade. He's now about 85 years old. Knows his stuff.

                        I asked him that very question a few years ago as I was building an earth bermed house and using concrete for a wall.

                        He told me that concrete does move to some degree when heated or cooled.
                        He mentioned that the steel reinforcement if welded would move differently than the concrete around the steel reinforcement rods which may cause spalling. He told me that welding the rods together would prevent them from moving within the concrete. He said that pre-stressed concrete cannot and should not be welded due to that very problem.

                        He did say that some rebar can be welded in certain instances but that rebar must be rated by the mill as weldable for it to be weldable. He mentioned that most rebar used in the USA cannot be welded. He said that tying with wire is the accepted practice for correct rebar placement.

                        In short, don't do it. Tie it together with wire.
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                        • #13
                          My sole comment is this...

                          Most rebar is produced from scrap steel of questionable metallurgical content, that is, rebar is very low on the quality of ingredients scale. To my knowledge, there is absolutely no rebar cast from metallurgically controlled ingredients. It's all junk.

                          Consequently, welding of rebar to form any shape will almost always change the grain structure to the detriment of the material, in other words, don't do it.

                          Wire ties are the proper and industry accepted method.
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                          • #14
                            The whole affair must have more to do with multiple independent overlapping pieces of re-inforcements (wire tied) incorporated into the poor versus a more rigid, less flexible mass (welded) and how it all works together than it has anything to do with the actual strength of the connection.

                            I mean that wire just isn't that tuff. If the man with the degree says that wire is better than weld there's no reason to doubt that, but there just has to more to it than whether two bars tied together are stronger than two bars welded together.

                            Is it possible that they tie it so that it can move rather than weld it so that it can't ??

                            I don't have a clue as to why they tie it instead of weld it but I do know if there was that much mojo in that wire we'd be tieing more chit together (farmer style) than welding.

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                            • #15
                              Well guys, never say never. I have just now opened up my plans for a concrete deck over an old chlorine pumping pit. The engineer is spec'ing A615 G60 rebar welded to the structural steel I am placing and to itself. This is the first time in 25 years I have gotten that in writing.
                              Don


                              Go Spurs Go!!!!!!

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