Why coated rebar is still a problem

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"I'm sure"...based on what exactly..."might easily be absorbed"...and "seems logical"...again, based on a singular youtube video that entered your feed that morning, and has therefore "cemented" (pun intended) your view of the entire issue, around what's largely a youtube rant.

Here's some data regarding splash and submerged concrete....regarding facts, data, messy and scary charts...and those thing I keep mentioning...design, and application.

http://www.adaa.asn.au/uploads/default/files/adaa-ref_data_sheet_6.pdf
http://www.adaa.asn.au/uploads/default/files/adaa-ref_data_sheet_5.pdf

Note how design also includes planned life, knowledge of the process, and standards for design and construction, so as to specify the cover over the rebar to prevent corrosion in the lifetime of the structure ...much like designing a vehicle, and specifying how it's lubed and maintained for...well....let's say it.... a DESIGN LIFE...

I know 100% that you won't read them...you don't even read the links that you provide.
 
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Originally Posted by StevieC
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My question to OP why did you post this video originally? Do you work in a field closely where rebar matters or just were posting an FYI for people building structural items exposed to harsh conditions?
 
We have a lot of aging infrastructure where I am and they are constantly scraping concrete off the side to check the rebar condition to see if they can push it further or it is becoming dangerous. Also having worked in construction for my uncle during my college years we did a lot of concrete forms and from general projects around our families houses etc. with rebar in them so it's something I know a little bit about and the video was interesting because I thought that coated rebar seemed to be the answer and it appears it is not.
 
Someone earlier made the thread killer post that public engineering isn't ever going to be done properly because that would put contractors out of work. When your entire business exists to be a lowest bidder for public works then you are doing the job for the cheapest and you need future revenue to keep your legacy alive and people employed.


Anything else is just posturing or wishing.
 
The entire premise that we engineer things to fail in public works is nothing but pure imagination run amok.

I'll use the public roads as a point of reference. Every road (and bridge, etc...) is designed to handle a specified amount of traffic to meet a specified design life. What that means is that a choice is made as to how much traffic a thing has to withstand (and what kind, since trucks are harder on things by a very large factor) and how long we want it to last, and the design is made from there.

We specify a design life purely from the stand point of cost - we pick a level that provides an adequate level of service and economy. I've not once worked on a project where cost was no object - it always is. We could build something that would likely last as long as you might want, but you likely will never want to pay the tab.

And as far as the contractor then building junk, its on the entity having the thing built to inspect and hold the contractor accountable to build it as specified. Yes, low bid is the norm in the construction process. Yes, they are all looking to save money where they can. That being said, in my years dealing with reputable contractors, they may ask for shortcuts to save money (or just try to implement them), but when called on it, and reminded of the specifications, they have complied - pointing out the importance of proper inspections. The poor contractors, not so much.

Building in a chloride rich environment (deicing salts in the transportation system), adequate cover is one part of the design solution for rebar, but it is not everything. Use of alternative rebar materials and coatings is another. Reducing the permeability of the concrete is yet another (that can come with tradeoffs - like winter snow and ice traction, but that is a whole different topic).

At the end of the day, the original video is exactly that - a rant, with a misleading thread title to boot...
 
Originally Posted by StevieC
We have a lot of aging infrastructure where I am and they are constantly scraping concrete off the side to check the rebar condition to see if they can push it further or it is becoming dangerous. Also having worked in construction for my uncle during my college years we did a lot of concrete forms and from general projects around our families houses etc. with rebar in them so it's something I know a little bit about and the video was interesting because I thought that coated rebar seemed to be the answer and it appears it is not.

What was the designed life and how old is it? You need to know this before you can conclude there is a problem on a specific project.
 
It would be interesting to know what kind of rebar and any other materials and techniques were used to construct the floating bridges here in Washington State. In particular, the Hood Canal bridge which is on salt water. The two Lake Washington bridges are on freshwater though some saltwater from the Puget Sound does make its way in through the Lake Union canal.
 
Originally Posted by PimTac
It would be interesting to know what kind of rebar and any other materials and techniques were used to construct the floating bridges here in Washington State. In particular, the Hood Canal bridge which is on salt water. The two Lake Washington bridges are on freshwater though some saltwater from the Puget Sound does make its way in through the Lake Union canal.


Looks like they are hot dip galvanizing it where coated re-bar isn't used...


https://www.newnybridge.com/what-is-rebarreinforcing-the-new-ny-bridge/
Quote
Once the bars are fully formed, they are treated with a special process called galvanization, which extends the life of the rebar. The steel bars are dipped into a hot bath of liquid zinc, which forms a crystalline "skin" over them. This helps prevent corrosive factors such as salt water from rusting or otherwise degrading the steel. Fortifying the rebar is especially important for the New NY Bridge, where the brackish waters of the Hudson River can penetrate concrete. Without galvanization, even small amounts of water or moisture could potentially compromise the rebar.



https://en.wikipedia.org/wiki/Rebar
Quote
This is a particular problem where the concrete is exposed to salt water, as in bridges where salt is applied to roadways in winter, or in marine applications. Uncoated, corrosion-resistant low carbon/chromium (microcomposite), silicon bronze, epoxy-coated, galvanized, or stainless steel rebars may be employed in these situations at greater initial expense, but significantly lower expense over the service life of the project.[11][12] Extra care is taken during the transport, fabrication, handling, installation, and concrete placement process when working with epoxy-coated rebar, because damage will reduce the long-term corrosion resistance of these bars.[13] Even damaged bars have shown better performance than uncoated reinforcing bars, though issues from debonding of the epoxy coating from the bars and corrosion under the epoxy film have been reported.[14] These bars are used in over 70,000 bridge decks in the USA.[15]
 
Last edited:
Originally Posted by StevieC
Originally Posted by PimTac
It would be interesting to know what kind of rebar and any other materials and techniques were used to construct the floating bridges here in Washington State. In particular, the Hood Canal bridge which is on salt water. The two Lake Washington bridges are on freshwater though some saltwater from the Puget Sound does make its way in through the Lake Union canal.


Looks like they are hot dip galvanizing it where coated re-bar isn't used...
https://www.newnybridge.com/what-is-rebarreinforcing-the-new-ny-bridge/

Quote
Once the bars are fully formed, they are treated with a special process called galvanization, which extends the life of the rebar. The steel bars are dipped into a hot bath of liquid zinc, which forms a crystalline "skin" over them. This helps prevent corrosive factors such as salt water from rusting or otherwise degrading the steel. Fortifying the rebar is especially important for the New NY Bridge, where the brackish waters of the Hudson River can penetrate concrete. Without galvanization, even small amounts of water or moisture could potentially compromise the rebar.




That looks like a cable supported bridge, not a floating one.
 
Originally Posted by StevieC
I was looking for a floating example but couldn't find one.



https://www.enr.com/articles/44013-the-10-longest-floating-bridges-in-the-world


The top three are here in WA state. There is one in British Columbia. The history has not been that great. We lost the Hood Canal bridge in a windstorm way back when and also lost the old I-90 bridge in a similar fashion. That happened during construction of the new I-90 bridge and almost took that out as well. Newer safety regulations close these bridges at specific wind speeds. The bridges can be opened to relieve stress.


There are not many examples of floating bridges but I picked them because of the subject discussion and figured this was an extreme environment for rebar to be in.
 
Have already provded design stuff for fully submerged concrete structures in salt water.

Worst example of the conditions for salt wetted concrete are underwater concrete tunnels (like Sydney Harbour Tunnel).

100% sea water on the outside, dry on the inside due to ventilation and traffic movement.

Inner and Outer layers of rebar are at different electropotentials as a result, almost forcing a galvanic (corrosion) cell
 
Another good example is the Confederation Bridge, which did not use "special" rebar according to the company that provided it:

Originally Posted by Chalybes Consulting

The Challenge - To achieve higher ductility, while using regular-grade rebar, so as not to incur a premium up-charge.

The Solution - Higher ductility was achieved through alloy modification of regular-grade rebar, customized by balancing carbon, manganese and micro alloy content.


Also, some engineering data on the bridge, which spans a small section of the Atlantic and is one of the longest bridges in the world:
https://file.scirp.org/Html/37782.html

This is a structure with a 100+ year design life and which has to deal with some of the worst conditions imaginable for this type of structure.
 
Originally Posted by MNgopher
The entire premise that we engineer things to fail in public works is nothing but pure imagination run amok.

I'll use the public roads as a point of reference. Every road (and bridge, etc...) is designed to handle a specified amount of traffic to meet a specified design life. What that means is that a choice is made as to how much traffic a thing has to withstand (and what kind, since trucks are harder on things by a very large factor) and how long we want it to last, and the design is made from there.

We specify a design life purely from the stand point of cost - we pick a level that provides an adequate level of service and economy. I've not once worked on a project where cost was no object - it always is. We could build something that would likely last as long as you might want, but you likely will never want to pay the tab.

And as far as the contractor then building junk, its on the entity having the thing built to inspect and hold the contractor accountable to build it as specified. Yes, low bid is the norm in the construction process. Yes, they are all looking to save money where they can. That being said, in my years dealing with reputable contractors, they may ask for shortcuts to save money (or just try to implement them), but when called on it, and reminded of the specifications, they have complied - pointing out the importance of proper inspections. The poor contractors, not so much.

Building in a chloride rich environment (deicing salts in the transportation system), adequate cover is one part of the design solution for rebar, but it is not everything. Use of alternative rebar materials and coatings is another. Reducing the permeability of the concrete is yet another (that can come with tradeoffs - like winter snow and ice traction, but that is a whole different topic).

At the end of the day, the original video is exactly that - a rant, with a misleading thread title to boot...

Well stated.
 
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