Research On Humidity And Corrosion Monitoring Of Concrete Structures Using Piezoelectric Smart Aggregates

Concrete structures are widely used in civil infrastructures. Unfortunately, however,they usually fail earlier than expected as a result of insufficient durability induced by agingand environmental pollution, hence, the issue of concrete durability has drawnincreasing concern of both domestic and foreign researchers. But how to establisheffective monitoring systems, conduct structural real-time online monitoring anddamage assessment still remains a challenging task in the field of structural healthmonitoring. In this research, an innovative piezoelectric-based transducer called smartaggregate was used to monitor the humidity and corrosion status of the concretestructures, and preliminary research has been conducted on developing smartaggregate-based sensing systems, performing signal processing and damage evaluation.Specifically, research work are done in the following three aspects:（1）The application of piezoelectric smart aggregates in humidity monitoring ofplain concrete components has been explored. Two plain concrete short columns werefabricated in our laboratory, the piezoelectric smart aggregates were preset into columnsbefore casting, a functional monitoring system are established to perform structuralhealth monitoring of these two columns in different humidity conditions. Then dataprocessing of the received signal was then conducted to obtain the relationship betweenthe internal moisture state and the sensing parameters of received signal. Experimentalresults show that the sensing parameters are very sensitive to the humidity status insidethe columns. Those sensing indicators such as amplitude, energy and average powershow a downward trend with the growth of the internal humidity, it leads to theconclusion that these parameters can be used as evaluation indexes for concrete internalhumidity monitoring.（2）The application of piezoelectric smart aggregates in deterioration monitoringof plain concrete components has been explored. A number of plain concrete columnswere fabricated and then suffered to salt-fog exposure for4months. Active monitoringmethods were performed in the same way using smart aggregates embedded in the plainconcrete specimens. Compressive tests were conducted to obtain the strength values ofthe plain concrete specimens under different corrosion ages of salt-fog exposure.Experimental results show that with the growth of deterioration age, both the amplitudeand the energy value of the received signal dropped, and a damage index was calculatedto assess the corrosion degree inside these plain concrete components.（3）The application of piezoelectric smart aggregates in corrosion monitoring hasbeen explored. A number of reinforced concrete short columns were fabricated and then eroded for certain ages using electrochemical accelerated corrosion methods. During thecorrosion process, the proposed active monitoring system was used to monitor thecorrosion degree of steel rebar in these specimens. Experimental results show that withthe growth of the corrosion severity, the sensing parameters showed an obvious declinetrend. Again, the relationship between the corrosion degree and the sensing parameterswas analyzed, and it is proved that the innovative smart aggregates possess the potentialto be used in corrosion monitoring of reinforced concrete structures.