Use of Epoxy coated bars in Bridges

[Hariharan]

How prevalent is the use of Epoxy coated Rebars in Bridges
in USA, apart from deck slabs? Are there any DOT
requirements in this regard in any state? My interest is in
girders, substructures including piers and other components
such as abutments, foundations. Any references, links would be
appreciated.
Thanks

 

[rubedog]

Oops, I forgot to mention two more items, when designing in conditions where you need epoxy reinf. you need to increase your clearances,especially at the top of bridge deck. Design wise you may need to use an exposure factor of 130 instead 170, see AASHTO 8.16.8.4

 

[Mithun]

I came to know that even two or three pinholes can start accelerated corrosion in rebar. Please reply and are there any chemical that will resist chloride in concrete

 

[14243]

Hi Mithun:
1. As you know that even small pinholes will accelerate the corrosion, we have to take extra precaution in touching up those pinhole areas with liquid epoxy.
2. To my knowledge there is no chemical to add in the concrete mix to resist chloride attack on steel. All aggregates and admixtures must be free of chlorides. Max. chloride ion is 0.1 perecent.

Hope this answer to your question.

JeyR

 

[RichardC]

Once the coating is damaged there will be a startpoint for corrosion on the black bar. However, I do not believe that the rate of corrosion is in any way accelerated.

Corrosion testing of epoxy coated bars (as found in ASTM 775)includes cathodic disbondment tests which will highlight accelerated underfilm corrosion. To date I have not seen any information / data that confirms accelerated corrosion of properly prepared coated bar. CD testing of good quality coated bar shows excellent resistance to underfilm creep / corrosion.

There are examples of failures (as in any industry) but this is primarily due to poor substrate / coating by the coater rather than the coating system itself. When properly controled the corrosion protection provided is good.

There are certain additives that can be incorporated to the cement / concrete to extend service life of structures. These additives provide some protection but should be used in conjunction with coated bar (belts and braces approach).