Old concrete non-deformed rebar

[DMcGrath]

At my father-in-law's house, we stumbled across an old concrete foundation with exposed, non-deformed rebar. Any idea approximately when the transformation to deformed from plain rebar was made? (1920s?) This is in southeastern USA.

 

[msquared48]

I also ran across some old square twisted rebar in a building built in the 20's in downtown Seattle - an old power station that was demolished in the 70's to make way for a new substation. Still have the piece that I use for a paperweight. One of the ends is untwisted for about 4", then the twisting starts.

I also have an 18" piece of the #14 bar for one of the roof ribs of the Kingdome taken at a cadweld joint. Has to weigh at least 40#.

It's amazing what we save as memories. And we wonder why we have too much stuff...

Can't help as to when the change was made though. Others can though.

Mike McCann
McCann Engineering

 

[msucog]

i pulled some out of the downtown atlanta ruins that were buried long ago. it wasn't part of the civil war ruins that were from when atlanta was burned and flattened, but it was definately old. that rebar i found was about #14 size twisted and was uncovered along with early 1900's type decorative corbels. i've always thought it it was the 1920-1930 time period when it switched over, but surely there's some gurus on this board that know the actual history. i even did a quick google search and couldn't find it...which is hard to believe that someone hasn't published it on the web yet. these days, you can search for darn near anything and find someone's "history" of it (or 9063 links to pornographic websites with the word you searched for related to it).

 

[Tomfh]

I have an old Hool and Johnson concrete textbook dated 1918 that covers deformed, plain and twisted squares. It implies all were in use at that stage.

 

[JAE]

CRSI has a book that might help you:

CRSI "Evaluation of Reinforcing Steel Systems in Old Structures"

 

[dik]

Thanks for the link, JAE... the square and twisted rebar was commonly used at the turn of the 20th century and was discontinued in the early 1920's. the twisted rebar had the advantage of being 'strain hardened' as well as improved bond. One project that was undergoing alterations had a bundle of rebar complete with the metal wire and tag attached... Some contractors in the good old days had limited experience with reinforced concrete.

Dik

 

[NITTANYRAY]

If you need to know the splice length for smooth rebars find an old copy of ACI 318-63. Section 805 states "For plain bars, the minimum amount of lap shall be twice that specified for deformed bars.

 

[jike]

The most unusual type of rebar that I have run into is a deformed oval, round equivalent. I understand that these were made in the 30's by Bethlehem to make them easier to field bend (in one direction).