Titan concrete anchors binding while tightening – GreenBuildingAdvisor

Hi all, I’m installing Simpson post bases into concrete using 1/2” Titan HD anchor screws (4” length).  I’ve overdrilled the depth to account for dust, and vacuumed out the hole (even after removing and trying again). I’ve even increased the hole diameter to 9/16”, and still I’m unable to drive the anchor more than half-way into the hole. 

Im using a standard Ryobi impact driver. I thought maybe I should use a higher impact driver, but the max torque on the screw is 65 ft/lbs, and the max torque rating for the impact driver is 300ft/lbs.  It just doesn’t seem to be doing the job. 

Any thoughts?

Adam