huangyhg

cadweld vs. bar-lock
we have recently designed an expansion of an existing concrete water treatment tank. one of our details calls for the reinforcing steel at the edge of the existing base slab to be partially exposed and cleaned, and then mechanically spliced to new rebar that will be in the base slab of the new portion of the tank. our details call for cadweld to be used for the splice, but the contractor wishes to substitute bar-lock couplers by dayton superior instead of the cadweld.
based on the literature for the two products, it seems that cadweld would be the more reliable system, but we have little experience with either cadweld or bar-lock.
does anyone have any experience with or opinions about these two systems? what are the pros and cons for each?
thank you very much for your help.
tony

i don't know about "bar-lock" specifically, but we've used mechanical tension couplers a lot on very critical applications. what's the problem with bar-lock couplers?
i don't know if there is a problem with bar-lock, that's partly what i'm trying to find out. like i said, in our office we have little experience with either system. but, based on the literature for each product, it seems to me that cadweld has less room for error in the installation - it comes with a premeasured amount of filler material that fills the void between the splice sleeve and the rebar. to me that seems similar to a full-penetration weld.
for the bar-lock, there are screws that have to be tightened to clamp the sleeve to the rebar, and to me that seems similar to a slip-critical bolted connection. i'd be concerned that the rebar in the bar-lock connection is more susceptible to slipping, especially if the workers don't do an adequate job tightening the screws. or perhaps, over time, with reversal of loading, the screws may loosen. i'm not sure how likely that is because it will be encased in concrete, but that is something that wouldn't happen with the cadweld system.
but, perhaps my fears about the bar-lock are unfounded, and are simply a result of my ingorance about them.
i don't think they commonly have problems, but i guess i don't know that for sure. i've used that type of coupler a few times without any trouble, but that's a small sample size.
it couldn't hurt to look into their installation process, inspection, etc.
i've allowed bar-lock once. i went to the job-site after the installation of them. they were very big. there is a significant gap around the interior. no way was concrete (or grout) going to be able to get inside. they were a bit pricey ($50/ea.), and the contractor hadn't installed them correctly. there were three bolts on either side of the butt joint. these bolts are supposed to be tightened until they sheared off. they didn't do it. after i told him it needed to be done, his response was "do you have any idea how long that will take?!" your contractor may be thinking along the same lines.
i wasn't aware of the cadweld system until this post. had i known about it, that's what i would have specified.
i don't know anything about bar-lock, but i know that cadweld must be pretty reliable as it was the only splicing system allowed for #14 and #18 bars in nuclear power plants. the would cut out some percentage, like one in ten, and test them. very few failed.
in my region cadweld has been replaced with bar lock. it seems easier to install and later verify. guys in my office used about 1000 of them on a large football stadium where a certain detail created rebar congestion. had no problems.
found that contractors can pretty well mess anything up. i dont think you can check to see if they did cadweld correctly.
any mechanical spice method must develop 125% of the bar strength. any or all systems are as good as the installation practices.

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