Rebar Corrosion Inspection By Active Wave Propagation Approach

Durability is essential for reinforced concrete structures to bear design load andfullfill functionality. Rebar Corrosion is key factor for structures'loss of durability andcollapse. In this thesis, PZTs were utilized as acutators for active stress wave monitoringmethod. The received signals of intact and corroded steel rebar were compared. It wasproved that this method could detect pitting and cavity on the rebar induced by chlorideions.The main works of this thesis are as follows:(1) The research literature of the detriment and remedial measures for rebar corrosionwas summarized. The pros and cons of various health monitoring method for thisstructrual degration phenomenon were listed. PZT was employed as actuators and sensors.(2) The phase velocity and frequency relationship of the single frequency narrowband impluse wave which propagated along the rebar was worked out. Specific centralfrequency was chosen for the actuator's signal.The mechanic model of PZT glued onthe rebar which worked as actuators and sensors was set up. It was figured out thatlongitudinal and flexual mode guided wave would propagate along the speciemen rebar.(3) Three PZTs were attached to a four meter long round rebar. Three stress wavepitch-catch experiments were carried out. The phase velocities of two mode were measuredand the propagation paths were illustrated according to boundary condition.(4) Two rebars were immersed into chloride ion solution and accelerated corrodedby electrochemical method. The stress wave pitch-catch experiments were carried outalong the corrosion process. The recieved signals were studied to study the pit severityand cavity position.This thesis proved that active wave propagation could be used to inspect the globalpitting and the cavity's location and extent.