Rebar Corrosion
Rebar Corrosion
(OP)
I recently examined some #8 (1" diameter) rebar in a 60 year old garage slab, where the top surface of the top slab bars appeared to be flattened. I measured with digital calipers and found that the left-to-right dimension was significantly greater than the top to bottom dimension. Although there was rust on the bars (and some of the bars were necked down and completely severed by the corrosion), for the flat topped bars it was not the flaky type of rust and did not look severe. But the only explanation I can think of as to why the top of the bars looks flat is that it has corroded away. See attached photo, although the flattening does not show up that well in the photo. The photo is 16 megapixels so you can enlarge it a lot if you wish, without it losing clarity (it takes a while to load, so please have patience). Has anyone seen anything like this flattened top surface of rebar? If so, is it attributable to corrosion?






RE: Rebar Corrosion
RE: Rebar Corrosion
RE: Rebar Corrosion
Square bars weren't used 60 years ago (i.e. 1955) that I'm aware of. Square bars were used much earlier, which is what CTW's link indicates:
Check out Eng-Tips Forum's Policies here:
FAQ731-376: Eng-Tips.com Forum Policies
RE: Rebar Corrosion
What I do not quite understand is why the top surface of the bar does not seem to be disintegrating from the corrosion. It seems quite hard and sound...although perhaps I just did not examine it thoroughly enough. Thanks for the comments. Thanks Canuck67 and JAE for the information that you have seen top flat surface bars caused by corrosion. It is re-assuring that you too have seen that and I am not looking at an illusion. For a #8 bar, a typical measurement that I made was 0.85" vertical x 1.06" horizontal. This means that 16% of the nominal 1" diameter bar area was lost due to the loss of the top part. For my calculations, I am going to assume (perhaps conservatively) that 25% has been lost, since there may be some loss on the remainder of the bar as well.
RE: Rebar Corrosion
RE: Rebar Corrosion
RE: Rebar Corrosion
RE: Rebar Corrosion
RE: Rebar Corrosion
I just received an email from ACI on an upcoming webinar, that may be of interest to you:
ACI WEBINAR
Rehabilitation of Structure with Reinforcement Section Loss
Tuesday, August 4, 2015
1:00 - 2:00 pm EDT
Link
RE: Rebar Corrosion
RE: Rebar Corrosion
to Ron - thank you for the information. Much appreciated.