huangyhg

concrete cover at reinforcing couplers
how do you deal with concrete cover at couplers.
for instance, if you have 2" of clear cover to a bar and place a coupler on it, all of a sudden you only have 1-1/2" clear cover.
my specific circumstance is a connection to existing reinforcing where 10" of reinforcing was left sticking out of the existing construction for future use. it happens to be in a waste water treatment plant, so i'm more worried about corrosion than development length.
i also have to provide a similar detail for the next guy who comes around to add further future construction.
i think my options are. 1) coat the coupler and the reinforcing around it with something like sika armatec 110 epocem which is a corrosion inhibitor (anyone have any experience with armatec? any alternative products?), 2) coat the surface of the wall with a waterproofer (subject to maintenance, yuck), 3) provide 3" of clear cover for the next guy so he doesn't have an issue (seems inefficent).
i'm interested to hear your thoughts.

i would say coating would be the best option. moving the bars in just for cover at a single point seems unreasonable. if you don't have sufficient cover, however, there is the fire resistance concern but since you are in a wastewater plant area, perhaps not a big concern.
if my basins catch on fire, something has gone seriously wrong.
jae, have you ever used armatec 110 or a similar product?
talk to the manufacturer about this.
the couplers that i have used in the past were justified on the basis of:
1. the coupler is made of a material with lower corrossion potential than reinforcing steel.
2. the area of the coupler exposed to more heat under fire is negligible compared to the overall volume of the bars that it is attached to.
i am sure these were based on tests e.t.c. that the manufacturer had done (it was a while ago), so the manufacturer of your couplers may have similar information.
csd
hot-dipped galvanized rebar mech splices are available. stainless steel rebar and couplings are available too
be careful to use stainless steel and normal steel together. it can accelerate the corrosion in the normal steel.
csd
have not used armatech. sorry.
since aci 318 does not clearly spell out where cover is measured from, for the situation you have described, why not check icc-es legacy reports for guidance? in these reports, cover is measured from surface of coupler sleeve. i did not dig deep enough to ascertain whether a reduction in cover is allowed if sleeve is coated.
do a search for the word coupler...and review reports.
aci-318 building code allows tolerences on clear cover. this tolerence can even be a negative number.
we use sika armatec-110 quite frequently as bonding agent during concrete repair work. once or twice we have used this product as corrosion inhibitor as well, when the rebars in concrete
degussa (masterbuilders, or whatever they are called now) makes a galvanic anode that can be embedded in the concrete. some people call them "hockey pucks". in my degussa book, they are called emaco corr-stops ci. perhaps these could be used instead of or in addition to galvanized couplers. i have used them for concrete rehab projects, but i don't see why they cannot be used for new construction when there is a situation like gumpmaster's.

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