Study Of Ultrasound Monitoring Reinforcing Steel Corrosion Based On Piezoelectric Sensor

With the development of economy in China, all kinds of large-scale complex engineeringstructures are constantly emerging, structural health monitoring in civil engineering technologyhas gradually become a hot research topic of the academia. In recent decades, the application ofsmart material structures in the field of engineering provides effective ways to achieve the truesense of the structural health monitoring. In recent years, with its unique sensing and actuationfunctions, piezoelectric ceramic has been one of the widely studied and used intelligentmaterials in civil engineering circles. Because of its fast response speed, good linear relation,wide frequency response range, low energy consumption, easy cutting, low cost and easyprocessing and other advantages, it has huge application potential in engineering structuralhealth monitoring. Therefore, with the piezoelectric material as the basic element and thendevelope a set of convenient, practical structure health monitoring system is also consistentwith the situation of our country. Based on the above background, the use of piezoelectricceramic materials for concrete structure corrosion damage of health monitoring technology isstudied, including the following several aspects:(1) According to the characteristics of concrete structure and properties of piezoelectricceramic material, with the PZT piezoelectric ceramic as a sensing drive element and cement orpolymer as a packaging material for preparing piezoelectric sensor, we tested and analysed itsperformance. As the results showed: the use of the packaging material prepared by thepiezoelectric sensor with high mechanical strength, dynamic output ability, good durability,high reliability, excellent performance. Among them, the piezoelectric ceramic elementpreparing piezoelectric sensor with low acoustic impedance, broadband characteristic, highlinearity, the good output response, good repeatability, high compressive strength can meet thelong-term, on-line, real-time monitoring requirements of concrete structure.(2) This paper we studied from the piezoelectric sensor which were affixed to thereinforced section, and used electrolyte accelerated corrosion method to accelerate thecorrosion of steel bar, so we can get the desired corrosion rate in a relatively short time. Relativeto the screw thread steel, round steel bar can accelerate corrosion and eliminate the surfaceirregularities (such as ribs) which can effect the corrosion rate calculated, so that the corrosion is more uniform,thus the calculated theory which is according to the steel bar corrosion rate andweight loss by error between the measured corrosion rate is more practical. Through theanalysis of the ultrasonic signal amplitude changes with time trends, we can draw thereinforcement corrosion and corrosion rate, with corrosion, the produce of the corrosionproduct, the amplitude of the ultrasonic wave have undergone significant changes, this studycan clearly reflect the relationship of the steel, reinforced concrete, corrosion products.(3) Using strain gauges and the piezoelectric sensor to research on steel corrosionmonitoring at the same time, through the analysis of test result of strain gauge strain and sensorsto receive the ultrasonic wave amplitude with corrosion time trend of knowable, about120h,strain gauge strain produced mutation, the amplitude of the ultrasonic wave is no longer growthbegan to become more stable, illustrated with corrosion products of accumulation andexpansion, to the surrounding mortar produced larger tensile stress, internal cracks andcontinuous development to the surface, stimulating and affixed to the resistance strain gauge,the micro strain increases rapidly. While the mortar interior also due to reinforcement andmortar interface detachment, making ultrasonic propagation along the bar only, amplitudestabilized.(4) We used acoustic emission instrument and the electric resistance strain chip at the sametime to detect on the steel corrosion, the experimental results show: strain gauge strain andacoustic emission signal quantity have the same growth trend along with the growth of thecorrosion time. Two parameter values appear the mutant on about the8th hour, the change canreflect the ongoing corrosion at this time, the continuous expantion of corrosion products,gradually produce tensile stress to the around mortar, so that the mortar generates a largenumber of micro crack and gradually develops to the surface.(5) This test used three methods which include piezoelectric sensors, resistance straingauge and acoustic emission instrument to research steel corrosion, parameter value such as thestrain gauge strain and acoustic emission signal number which comes from the experimentpresents a good corresponding relationship with the ultrasonic wave amplitude changes whichcome from the use of piezoelectric sensors for monitoring corrosion. Thereby, the new methodof the piezoelectric ceramic sensor for monitoring corrosion of steel adopted in the study notonly can achieve real-time, on-line monitoring, but also has certain feasibility and validity. In this paper, the experimental results show that, using the piezoelectric ceramic sensor iscapable of on-line, real-time, field of rebar corrosion on concrete structure safety monitoringand can make timely prediction and assessment on the damage of concrete which suffers fromcorrosion.