The design of an instrumented rebar for assessment of corrosion in cracked reinforced concrete

An instrumented rebar is presented which was designed to have a realistic mechanical performance and to provide location dependent measurements to assess the environment with regards to reinforcement corrosion. The instrumented rebar was constructed from a hollowed 10 mm nominal diameter standard rebar with 17 electronically isolated corrosion sensors.

Instrumented and standard rebars were cast into concrete beams and bending cracks were induced and held open using steel frames. Epoxy impregnation was used to assess and compare cracks in the concrete around the instrumented and standard rebar. As bending-induced cracks reached the reinforcement, slip and separation occurred along the concrete-reinforcement interface.

Cracks in the concrete surrounding standard and instrumented rebars are largely similar in appearance; however, sensors protruding from the instrumented rebar reduced the separation between the steel and concrete. Cracked beams with cast-in instrumented and standard rebars were ponded with a 10\% chloride solution and the open circuit corrosion potential (OCP) of the 17 sensors was measured for up to 62 days.

Measurements from the individual sensors indicate when and where active corrosion may be thermodynamically favored based upon the local environmental conditions. Results indicated the length along the instrumented rebar where active corrosion was thermodynamically favored increased with exposure time due to the increased aggressivity of the local environmental conditions.