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August 9 - August 14, 2015

What’s the best way to prevent corrosion of reinforcing bar in concrete?


Selected Answers

From Joe Miller of NextGen Green Building Products, Inc. dba Direct2Contractors.com on August 24, 2015:
I do not understand if the question is for new or existing bridges. For existing bridges, I have been involved with many projects over the years ranging from impresssed current CP mesh systems to wires in troughs to wires and mesh on the undersides. Also, I have used all kinds of surface-applied chemicals, from very low viscosity MMA's to split slab membranes to sacrificial anodes. For new bridges, likewise, I have seen fusion-bonded epoxy on rebars, epoxy-coated rebars,surface-applied treatments and split slab membranes. Given the very high costs to build bridges or to try to maintain them and extend their useful service life (protect the rebars from rusting), it seems like several of these methods should be used in concert. A new material is now available to also consider. That would be a patented liquid, crystalline penetrating sealer. Applied to the surfaces of cast-in-place or precast concrete, this new technology enters into the pores and capillaries. It does not form a film on these surfaces, so it is unaffected by weathering, abrasion or impact damage. So if steel rebars are used in the elements, add this to the mix, save taxpayers money, extend the useful life of these costly and critical parts of our transportation system. Hope this helps. Thanks.

From H. J. BOSWORTH of BOSWORTH ENGINEERING on August 21, 2015:
Galvanizing is the way to go in areas of road salts or near marine environments. The rebar coated with epoxy is very slick and the development of the rebar for anchorage forces is reduced with the epoxy coatings.  In most cases, having the cover recommended by ACI will provide a good service life.

From Tom Schwerdt of Texas Department of Transportation on August 20, 2015:
Michael,  I'm not sure where pot life is coming in for you. Epoxy coated rebar is typically fusion-bond epoxy (FBE), applied in a powder coating process. No pot. No potlife.

From Warren Brand of Chicago Corrosion Group on August 15, 2015:
Pete, why would you choose fusion-bond epoxy over hot-dipped galvanizing?

From Michael Quaranta of OPERATIONS 40 on August 14, 2015:
In 1976 there was a re-bar corrosion-proofing test program conducted in Utah on some new bridges. The coating was ceramic and it was developed by the then Chief Engineer at Hill AFB. Someone might want to review that performance project if the data was collected. The thought of coating re-bar with epoxy is out of most cost parameters, and the short pot life of the small batch mixing of epoxy (UGH) would be a defeating challenge

From Pete Engelbert, CIH, CSP, PCS of Level 3 Coating Inspection, LLC on August 14, 2015:
Current thinking is to use fusion bond epoxy (FBE) on the rod. I have seen a bridge that was in service where its concrete had been drilled to reach the rebar, and a connection was made to the concrete surface in several places. Then the bride surface was covered with thermal spray aluminum. Some concrete bridges have also used impressed current. The service conditions always dictate, but fiberglass has its own inherent issues. FBE is a nice general catch-all.

From Michael Quaranta of OPERATIONS 40 on August 13, 2015:
It is purely a matter of physics. Keep the buried rebar at a pH above 12.

From peter gibson of GRC Fiberglass Coatings on August 13, 2015:
Coat the rebar with epoxy.

From Tom Schwerdt of Texas Department of Transportation on August 13, 2015:
One big problem with the carbon and fiberglass bars is that, typically, they can't be bent onsite, and the minimum bend radius is larger.

From Warren Brand of Chicago Corrosion Group on August 12, 2015:
I like John's answer better. John, what is the approximate cost difference? And do the size or placements of the bars need to be different, as well?

From John Sexton of NYSDOT on August 12, 2015:
Use carbon fiberglass reinforcing bars.

From Warren Brand of Chicago Corrosion Group on August 11, 2015:
Have the re-bar hot dipped galvanized.

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