[TowerTalk] How best to keep the rebar cage centered in thehole?

[ersmar at comcast.net]

Keith:

    I have no experience with a foundation failing due to corrosion of the rebar.  However, I based my advice on the following postings, among others, that I've read here on TT over the past 8 years of my subscription:

http://lists.contesting.com/archives//html/Towertalk/2003-08/msg00332.html

http://lists.contesting.com/archives//html/Towertalk/2003-08/msg00335.html

http://lists.contesting.com/archives//html/Towertalk/1998-11/msg00148.html

http://lists.contesting.com/archives//html/Towertalk/1998-11/msg00133.html

http://lists.contesting.com/archives//html/Towertalk/2003-08/msg00330.html

http://lists.contesting.com/archives//html/Towertalk/1998-10/msg00034.html

Etc., etc.

     Plus my copy of the UBC (1997), in Section 1907.7.1 which covers (pun intended) reinforcing for cast-in-place concrete (nonprestressed), requires a minimum reinforcement cover of three inches for concrete cast against and permanently exposed to earth (the situation for my tower's concrete base.)  

     Plus the Rohn drawings I've seen over the years, and my own Trylon tower's drawings, specifically call for a three inch cover over all rebar, including the bottoms of the vertical pieces.

     So I guess you could say I have no empirical evidence and it's just my opinion.

73 de
Gene Smar  AD3F




 -------------- Original message ----------------------
From: "Keith Dutson" <kdutson at sbcglobal.net>
> >Do NOT use the rebar in the foundation hole as an anchor point for your
> rebar cage.  The ends of the rebars sticking into the dirt will eventually
> corrode and follow the rest of the rebar into the concrete mass.  That could
> lead to cracking, especially that close to the top of the concrete.
> 
> ------------------------------------
> Is there any empirical evidence to say this is what will happen, or just
> your opinion?  The reason I ask is that I recently uprooted an old satellite
> antenna base (the old 8 foot dish) that had the mast (pipe) buried about a
> foot in the bottom of the hole and 1 yard of concrete poured around it.
> This thing was planted in 1982, more than 20 years ago.  The pipe is still
> intact below the bottom of the concrete with very little rust.  Also, the
> concrete is still quite solid with no sign of cracking.
> 
> 73, Keith NM5G
> [snip]
> 
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