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RE: Coring Concrete

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>>>Our current design involves drilling a 6" diameter hole and a 1 1/4"x
long anchor bolt and filling the holes with mortar. The contractor wants to
core the hole due to the diameter. Our drawings specifically say that
is not allowed. The girder is not subject to uplift at the anchorage point
but does experience significant vibrations every ten seconds. Does anybody
know of a way to drill a 6" diameter hole and still have a rough enough
surface to ensure adequate bond between the mortar and the walls of the
hole. The contractor is squawking at using epoxy.

I would strongly suggest that you check with the manufacturer of the epoxy
you are proposing to use.  It is my understanding that epoxy manufacturers
recommend that you use hole not more than 1/4" larger than the size of the
bolt when using epoxies.  The two concerns are 1) with all that  epoxy
curing it will produce high temperatures in the epoxy that will impact its
strength and 2) there will be excessive creep if the bolt is subject to
continuious loads.

The other option is to use cemtitious grout but even so the 6" dia hole is
probably larger than needed.

As far as whether a cored hole will produce a rough enough surface I would
recommend that you check with the manufacturer of the product you

Mark Gilligan