Epoxy Coated Rebar 2

[sykimm]

In ACI code base, bond strength of epoxy coated rebar shall be reduced compared to normal rebar.

Is there any recommendation about the same in BS code?

I'd like to know the important consideration in structural analaysis and design in reinforced concrete using epoxy coated rebar.

Your help would be helpful.....

 

[structuresguy]

Well, it seems the only people who like the epoxy coated rebar are the epoxy manufacturers. In theory it works well because the epoxy is an electrical insulator. Without an electrical pathway between the steel and concrete, no corrosion can occur.

In practice, structures with epoxy rebar deteriorate faster than with normal uncoated rebar. The reason for this is if there are any nicks in the epoxy coating, all of the corrosion potential of the system drives corrosion to occur at very fast rates in small localized areas. Thus, a bar can corrode right thru in one spot while everywhere else it is in perfect shape. THere are many precautions that must be used when handling shipping and installing epoxy rebar to avoid nicks. But it is almost impossible to avoid damaging the coating. Even something like the vibrator (which is supposed to be covered with rubber) can damage it by vibrating a sharp peice of aggragate against a bar, and WAMMO you got a nick. Most highway departments have outlawed it if they are smart. Otherwise they absolutely require it.

Stay away from it if you can. A good quality concrete whith proper mix design and cover will provide you all the corrosion free service life you need. If you really need a super high corrosionm resistance, consider MMFX steel rebar, or even stainless steel. THe MMFX is somewhat more expensive than normal rebar, but it also has higher strength. Plus it has the corrosion resistance similar to that of stainless steel.

 

[sykimm]

Thank you Structuresguy.

As you mentioned, proper mix design and cover depth would be the most recommendation on this matter instead of epoxy rebar.

However, in job/project specification base, epoxy rebar shall be the only option of a reinforcements.

Hence, I'd like to know the BS codes/recommendations on epoxy coated rebar, like as ACI code bond strength reduction, e.g.

I'm still opening on this matter......

 

[structuresguy]

Sorry I can't help you on BS code. Just thought I would put forward my experiences with epoxy rebar in Canada and the US.

Hope you find what you are looking for.

 

[JAE]

There are still many many U.S. states that require/use epoxy coated rebar in bridge decks. Whether its "smart" or not is still an open question, and a very debated one at that.

 

[jheidt2543]

Structuresguy,

You note MMFX and stainless steel as alternatives to epoxy coated rebar. What about galvanized rebar? I thought it was promoted pretty heavily a number of years ago. And, while we're at it, can you give us the relative cost differences between standard, epoxy coated, MMFX, stainless and galvanized rebar? I know it varies considerably based on rebar size and quantities.

By the way Wisconsin and Illinois DOT's are heavy users of epoxy coated rebar.

 

[kenvlach]

Re galvanized rebar & galvanized vs. epoxy coated rebar. The American Galvanizers Association

http://www.galvanizeit.org/

lists 3 publications on their site. The first is a free download:

Hot Dip Galvanizing for Corrosion Prevention: A guide to specifying and inspecting hot-dip galvanized reinforcing steel. After a brief look at corrosion and the hot-dip galvanizing process, hot-dip galvanized rebar's performance in concrete, design, specification, fabrication, and installation issues are addressed. 20 pages, SP-SGRS-02 $5.95 or free at

http://www.galvanizeit.org/resources/files/AGA PDFs/SP_SGRS_02.pdf

Evaluation of the Performance of Galvanized Steel Reinforcement in Concrete Bridge Decks. This report, prepared by Construction Technology Laboratories, Inc., for ILZRO & the AGA, updates the findings of an investigation by the Portland Cement Association involving 10 bridge decks. 134 pages, RE-BR-92 $20.00

Protection of Reinforcement in Concrete: An Update. This publication reviews work carried out worldwide, particularly on the performance of hot-dip galvanized and fusion-bonded epoxy-coated reinforcements, from the published information available from various journals, reports and other sources. 290 pages, RE-PROT-95 Call for price.

 

[structuresguy]

Sorry, I don't have prices for the MMFX and stainless rebar of hand. I know I priced the MMFX once, but can't find my notes for it. It seems it cost more to use the MMFX than to use a good quality mix with corrosion inhibitors.

Contact MMFX for more info on the cost and availability (

http://www.mmfxsteel.com).

I am sure they have some comparison costs versus stainless steel as well.

As for galvanized rebar, the galvanizing coating significantly reduces the bond strength of teh bar in concrete. Hence lap splices and development lengths are greatly increased. I can't remember the exact percentage, but I am sure the the publications listed above or ACI has guidance on this issue.

 

[Womprat]

Hi all,
It is very difficult to obtain unbiased, scientifically accurate information that you would want to build your bridge on. When there are large sums of money at stake the correct anwers are even more difficult to find. Can anyone point me to more information about the adverse effects of rebar that is coated with epoxy? Is using black rebar actually more corrosion resistant than epoxy covered bar? Are there any scientific studies to back this up?
Thanks,

Womp

 

[GrahamParkinson]

Does anyone have preferences regarding admixtures for corrosion inhibition or coatings for reabar that would be suitable for a salt water exposed concrete dock?

(We have a mixture of epoxy and non epoxy rebar in place and are using a silica fume mix)

Graham

 

[boo1]

Recommend you review these sites:

http://www.tfhrc.gov/structur/corros/results.htm

In Florida test results see

http://www11.myflorida.com/research-center/Completed_Proj/Summary_SMO/FDOT_0510603.pdf

Basically shoot down any extra value imparted by epoxy coating when good quality concrete is used.

I have seen ads selling low carbon , chromium-bearing steels that form a chromium oxide barrier on the steels surface - the same mechanism which protects stainless steel. Never used it so can't say how good it is!

http://www.mmfx.com/main.asp