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woody with a view
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anyway.....
"Investigation by the United States National Transportation Safety Board (NTSB) concluded that the accident was caused by metal fatigue exacerbated by
crevice corrosion. The plane was 19 years old and operated in a coastal environment, with exposure to salt and humidity.[6][7]
According to the official NTSB report of the investigation, Gayle Yamamoto, a passenger, noticed a crack in the fuselage upon boarding the aircraft
prior to the ill-fated flight but did not notify anyone."
luckily, there has never been another plane that has operated in such an environment since! maybe the Asiana flight had metal fatigue also when it's
tail slammed against a rock jetty? prolly those cheap Chinese rivets!
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bledito
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so back to the varrilla (rebar) anyone seen anywhere you can get FBE fusion bonded epoxy coated varrilla (rebar) in baja.
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Ken Bondy
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I've watched this thread with great interest. In my 50-year career as a structural engineer specializing in the design and construction of concrete
building structures I have never specified cathodic protection, nor seen it used on any building in which I was involved. The primary method for
providing corrosion protection for reinforcing steel in concrete is with adequate concrete cover over the bars. Hardened concrete is very alkaline
(pH 12-13) and steel does not corrode in an alkaline environment. Certain concrete cover distances have been proven to be effective in preventing
steel corrosion in various environments, and they are specified in all model buiding codes. Some structures in extremely corrosive environments,
like bridges in areas where deicing salts are applied, require exceptional corrosion protection, and that's where you see special measures used, like
epoxy-coated reinforcing bars and cathodic protection. But these things are not presently used in building construction, residential or commercial,
and I see no signs that they will be used in the future.
carpe diem!
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J.P.
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| Quote: | Originally posted by Ken Bondy
I've watched this thread with great interest. In my 50-year career as a structural engineer specializing in the design and construction of concrete
building structures I have never specified cathodic protection, nor seen it used on any building in which I was involved. The primary method for
providing corrosion protection for reinforcing steel in concrete is with adequate concrete cover over the bars. Hardened concrete is very alkaline
(pH 12-13) and steel does not corrode in an alkaline environment. Certain concrete cover distances have been proven to be effective in preventing
steel corrosion in various environments, and they are specified in all model buiding codes. Some structures in extremely corrosive environments,
like bridges in areas where deicing salts are applied, require exceptional corrosion protection, and that's where you see special measures used, like
epoxy-coated reinforcing bars and cathodic protection. But these things are not presently used in building construction, residential or commercial,
and I see no signs that they will be used in the future. |
I worked for many years on all kinds of reinforced concrete structures in the late 60's I worked on the One Shell Plaza which was the tallest
reinforced concrete building in the South it topped out at 55 stories. as they used to say in the trade my body was wore out and beat up but my brain
was like new because I never used it.
I don't know where this guy came up with this info. on rebar buy in all my years around Cal Trans engineers I never heard of it and if it was weird
I am shure they would have specified it.
Retired Ironworker local.118 Sac. Ca
[Edited on 7-10-2013 by J.P.]
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bledito
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http://www.corrpro.com/content/186/cathodic-protection-of-a-...
this is one example there are others. Just because some one has never used it in their trade does that make it a non issue. baja has a high corrosive
enviorment high heat, salts, these salts make way into the concrete via sand mix, water, enviormental infiltration. I am not trying to sell anyone
anything here. If you spend a bit of time researching the effects of corrosion on reinforced concrete in coastal and non coastal areas, or just look
around the states at bridges and structures built you will find examples of spalled out supporting columns. I worked in an industry that utilized CP,
natural gas transportation. i was involved in design and implementation of the cp systems. most of the steel i worked on had wall thickness of .50 or
.375 sometimes less . have personally seen failures cause by corrosion. while I am not an engineer in CP, I have enough insight in this feild to
consider the protection of building structural
steel a point to make. I plan on installing some type of cp on any structure I will build, for the cost, relativly inexpensive, why not.
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Ken Bondy
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| Quote: | Originally posted by bledito
.....most of the steel i worked on had wall thickness of .50 or .375 sometimes less... |
I am puzzled by this statement bledito. Do you actually mean "diameter" instead of "wall thickness"? Also, are the units of the numbers ".50" and
".375" inches?? If the answer to both of those questions is "yes" then it appears you are talking about standard #4 and #3 bars.
carpe diem!
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Islandbuilder
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Seems like the larger concern would be starting with rusty rebar, that will have a reduced bond to the surrounding concrete due to the iron oxide on
it surface. I built in the Pacific Northwest, with lots of rain and surface water, and it seems like this would be a far more likely environment for
galvanic erosion than in Baja. Unless, you are using beach sand or sea water in your concrete mix.
I looked into using sea water for a remote island project, and found that it reduced the strength of the finished pour by less than 10%, which I
figured I could counter by going to a 6-sack mix instead of the usual 5-sack. I decided to bring in a barge and transit mixers in the end.
Another concern I have had in watching Baja concrete pours is small batched being made, making consistency through an entire pour more challenging,
and the high water content used to make the mix more user friendly. The more water, the weaker the finished product.
I always used retarding agents to slow the cure if it was sunny, a curing agent on all finished slabs which were poured over a doubled or tripled
vapor barrier. All to slow the cure which also made a stronger finished pour.
In the heat of Baja, even in the winter, I would think those steps would be of greater importance than tossing a zinc in the septic tank.
But again, I know what I don't know, and this is certainly fits into that category.
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Ken Bondy
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| Quote: | Originally posted by Islandbuilder
Seems like the larger concern would be starting with rusty rebar, that will have a reduced bond to the surrounding concrete due to the iron oxide on
it surface. |
Actually a light layer of surficial rust improves bond. This has been demonstrated numerous times in testing performed by the Concrete
Reinforcing Steel Institute (CRSI).
carpe diem!
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J.P.
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On some remodel jobs where the existing building was around 100 years old the demolition reviled old Rebar that that was Square. and it appeard to be
in near perfect condition.
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Ken Bondy
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The first deformed reinforcing bars used in concrete were square. I think they were used up through the 20s when they were replaced by round bars.
carpe diem!
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DENNIS
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| Quote: | Originally posted by Ken Bondy
they were replaced by round bars. |
I much prefer a round bar. It's easier to see everybody. 
Start time at Sharky's in 25 minutes. SALUD
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Ken Bondy
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| Quote: | Originally posted by DENNIS
| Quote: | Originally posted by Ken Bondy
they were replaced by round bars. |
I much prefer a round bar. It's easier to see everybody.
Start time at Sharky's in 25 minutes. SALUD |
I agree. In square bars I always ended up in the corner where it was hard to see anybody. And get the barkeep's attention.
carpe diem!
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Mexitron
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| Quote: | Originally posted by Ken Bondy
| Quote: | Originally posted by Islandbuilder
Seems like the larger concern would be starting with rusty rebar, that will have a reduced bond to the surrounding concrete due to the iron oxide on
it surface. |
Actually a light layer of surficial rust improves bond. This has been demonstrated numerous times in testing performed by the Concrete
Reinforcing Steel Institute (CRSI). |
That's what I had heard too...or else I've got a few patios and retaining walls to redo!
I've torn out old patios and walls at times and if the rebar was well ensconced in the concrete it was usually as shiny as new.
[Edited on 7-10-2013 by Mexitron]
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Islandbuilder
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Yeah Ken, I understand. I was referring to flaky rusty bar, the kind you get when you leave the verticals stubbed out of the footing for a few years.
Under UBC there was a threshold for rust that required really rusty bar to be removed. Seems like there's some language in the IBC that limits or
prohibits rusty reinforcing steel, but leaves room for the inspector to make the call.
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mulegemichael
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so...let's cut to the chase here....please....will i be able to outlive my patio?...is it at all possible?...i just built it...i would love to enjoy a
few years with it.
dyslexia is never having to say you\'re yrros.
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bledito
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yep it'll last long enough. were those retarding agents and curing agents guys with hoses spraying down the concrete for a week or so.
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Ken Bondy
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| Quote: | Originally posted by mulegemichael
so...let's cut to the chase here....please....will i be able to outlive my patio?...is it at all possible?...i just built it...i would love to enjoy a
few years with it. |
As long as the rebar was properly installed with the appropriate concrete cover it should be good for 100 years  . Does it even have any rebar??
carpe diem!
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Islandbuilder
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| Quote: | Originally posted by bledito
yep it'll last long enough. were those retarding agents and curing agents guys with hoses spraying down the concrete for a week or so.
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No, the retarders were added to the mix, and the curing agents were sprayed on when the forms came off, or the slab was walkable. The only times we
didn't use them was when the slab was going to be acid etched and dyed.
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