rebar question

[railrider]

hi ,
needed to get some opinions, i will be building a house in the carribean using cmu 8" thick and all cells grouted. my question is to use epoxy coated or galvanized rebar or use a heavier bar for the rust factor.
thank you

 

[dbuzz]

For both epoxy coated and galvanised reinforcement there is potential for damage to the surface treatment during transport, handling and placement.

I've never heard of including a "corrosion allowance" to the diameter of untreated reinforcing bars. If the reinforcement starts to corrode it will eventually break off the cover, since corroded steel has approximately seven times the volume of non-corroded steel.

Perhaps of more importance is the mortar mix and the cover to the reinforcement. Check out the CCAA's "Durable Masonry Specification Checklist" (

http://www.concrete.net.au/pdf/buildchecklist1.pdf)

which proposes mortar mixes and minimum cover for different exposure environments.

 

[structuresguy]

Well, first off, I have never heard of anyone using corrosion resistant rebar in the cells of masonry walls, at least not here in Florida. The carribean should not be much different.

Second, what dbuzz said is true on all counts.

I would concern myself with providing adequate cover to the steel and a good quality grout mix. Also the block itself can help you out. You can use block with intergral waterproofing, which will limit any water getting thru the block to the steel.

If you are really concerned about corrosion beyond this, I would look at using a corrosion inhibiting admixture or MMFX rebar. But I think these are overkill. If you have exposed tie beams/columns, you could spray exterior surface with a migrating corrosion inhibitor, rather than using an admixture.

 

[Ron]

Ditto on dbuzz and structuresguy....the most important impediment to corrosion is the quality of the cover concrete and the amount of cover. You can also use a nitrite corrosion inhibiting additive in the concrete. Used in the Bahamas as well as here in Florida.

 

[railrider]

thank you guys for the info.

 

[sdz]

The cmu manufacturer's here recommend that for single skin walls (whih I asume you are using) that the external face be painted with 3 coats of 100% acrylic based paint for waterproofing.

I also agree with what the others said about grout quality and cover. I usually specify that horizontal brs in bond beams be supported in preformed wire hangers, known here as W2 hangers.