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Re: Fusion Bonded Epoxy (FBE) Coated Reinforcement

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Eqbal M. Kassam wrote:
> 
> I would appreciate all views on this issue.
> 
> What is the experience of FBE coated reinforcement used in concrete in aggressive environment- high chloride / sulfate exposures?
> 
> I believe durable concrete can be obtained by proper materials, mix design, curing, etc. Is there any additional benefit in using FBE coated reinforcement?
> 
> Also, I understand that poorly handled and damaged FBE can actually result in faster deterioration of reinforcement. Any comments ? Since coatings contain pinholes, can this cause more problems.
> 
> Can the coating debond after say 15 to 20 years?
> 
> A few years ago, a structure in Florida that used FBE reinforcement actually deteriorated much faster. Are there any similar results ? What about highway bridges?
> 
> Thanks in advance
> 
> Eqbal Kassam
> 


As you said, durable concrete can be obtained by good concrete
practices. Sometimes, even more durable concrete can be obtained in one
of the following ways. 

Admixtures referred to as corrosion inhibitors can also be added in
order to improve the performance further. 

Inorganic corrosion inhibitors such as DCI by W.R. Grace will prevent
corrosion as long as the nitrite concentration provided by the admixture
in the concrete is greater than the chloride concentration. The nitrite
concentration will reduce with time since it continually neutralizes the
chlorides.

Organice corrosion inhibitors such as Rheocrete 222+ by MasterBuilders
will prevent corrosion by blocking the pores of the concrete and forming
a film on the steel. Since this product does not neutralize the
chlorides, the effectiveness of the product should not be reduced with
time.

I agree that handling of epoxy coated rebar is critical since any damage
would reduce its performance. Yes, pinholes if in sufficient quantities
will reduce the effectiveness. Yes, the coating can debond after so many
years. Yes, there were many structures in the Florida Keys which have
deteriorated very fast due to extremely severe corrosive corrosion, very
bad construction practices and relaxed fabrication standards. Note that
these structures in the Florida Keys where built at the early stage of
epoxy coated rebar existance. There is now a lot more knowledge about
the potential problems and how to avoid them. Fabrication standards are
now more severe as far as pinholes and bond to the steel.

Some authorities still specify epoxy coated rebar but use the following
precautions.

- The fabricator must be part of the CRSI voluntary certification
program

- ASTM specs for fabrication are applied strictly

- Bundle handling practices such as placing the bundle on timber mat and
lifting bundles with nylon straps are specified for both shop and field
work.

- The rebar is inspected at the plant, at arrival to site, and in the
formwork for pinholes and other defects.  

- Repair of defects is only done as per ASTM standards otherwise the
rebar is rejectd.

- The amount of time that the rebar can be exposed to the sun is
limited.

- Plastic coated vibrators are specified for placing concrete



If you allow my humble opinion on this topic, I believe that it is much
easier to enforce proper epoxy coated rebar practices if the quantity is
small. If there is lots of epoxy coated rebar, I believe that the
contractor will have the natural tendency to just do the job quickly
rather than carefully and I don't think that the construction supervisor
will be able to attend the bar handling operations at all times. I would
be more reluctant to specify epoxy coated rebar when large quantities
are required.



Bruno Côté
BOCTE(--nospam--at)ibm.net