Abstract: Hollow rebar may be used for structural reinforcement in a drilled shaft and to provide access tubes for a sonic integrity testing probe. Rebar (short for reinforcing bar) is steel bar used as a tensioning device in reinforced concrete that holds the concrete in compression. According to the system described herein, hollow rebar may provide high strength reinforcement in the drilled shaft while at the same time providing an access tube for a sonic integrity testing process, such as crosshole sonic logging (CSL). The high strength hollow rebar, having ridges, threads and/or other appropriate surface deformations, provides improved adhesion to concrete, thus eliminating the problem of debonding associated with non-structural access tubes made of smooth PVC or steel pipe.