Guofu Qiao

Optimization Design of a Corrosion Monitoring Sensor by FEM for RC Structures

Structural health monitoring techniques provide the scientific basis for damage early-warning, safety assessment and maintenance design of reinforcing concrete structures. Solid-state and current confining corrosion sensor, the key hardware component in corrosion monitoring system based on electrochemical theory for reinforcing concrete structures, is investigated here. The finite-element method is applied to simulate the distribution of the electric field in concrete and optimize the geometric configuration of the sensor. The simulation results indicate that the electric field can be confined accurately in a fixed region by the optimized corrosion sensor.

An Experimental Study on the Performance of Piezoceramic-Based Smart Aggregate in Water Environment

A number of smart aggregate (SA)-based monitoring systems have been developed to monitor the early age hydration process of concrete. In these systems, the embedded SAs act as sensors and work in a solid-liquid mixture. However, the influence of water on the performance of SA is still unclear. This letter presents some efforts to study the working performance of SA in water environment. A SA-based monitoring system, with the SA sensors immersed in tap water for various periods, was designed to monitor the variation of sensing signals. The test results show that the influence of water on SA is vital. The amplitude of sensing signals increases greatly for the early hours in water, and is tending toward stability for subsequent time. This can thus explain why the amplitude of sensing signals increases fast during early hours in concrete hydration monitoring process.

Experimental Investigation on the Dynamic Properties of RC Structures Affected by the Reinforcement Corrosion

Reinforcement concrete (RC) structures in service are suffered from environmental attacks, especially the rebar corrosion, which may lead to the deterioration of mechanical characteristics of steel bars, surrounding concrete and bond strength, and therefore jeopardize their performance in earthquake events. In this paper, an electro-chemical accelerated corrosion process was introduced to RC frames and columns, and then the half-cell method, linear polarization method and constant potential step method were performed to monitor the corrosion status. Furthermore, for studying the dynamic properties of RC structures affected by reinforcement corrosion, the dynamic tests were carried out to study the fundamental frequency and damping ratio of control frame and frames which designed steel losses were 10% and 30%, respectively. The experimental results show that the influence of corrosion damage on fundamental frequency and damping ratio is significant. Substantial increases were observed in fundamental frequency and damping ratio after the accelerated corrosion occurred. It indicates that the decreased bond strength or ultimate bearing capacity cannot ensure that the stiffness of healthy member is always greater than that of damaged member. Moreover, the variations of frequency and damping ratio, induced by steel corrosion, are not inconsistent. This investigation provides further insight into the use of fundamental frequency and damping ratio to detect damage of RC structures.

Corrosion Energy: A Novel Source to Power the Wireless Sensor

Compared with traditional sensors powered by the grid, energy-harvesting wireless sensors have many significant advantages, especially when applied in harsh environments. A novel power supply element, i.e., concrete battery, is designed for the wireless corrosion-monitoring sensors. Then, the power generation capacity of the corrosion-sensitive materials (Mg and Zn) is verified in a series of simulated concrete pore solutions. Furthermore, the electric quantity generated during the corrosion process is analyzed in detail. The results indicate that the novel concrete batteries based on Mg or Zn materials are a promising solution for powering wireless corrosion-monitoring sensors.

Qualitative and Quantitative Sensors Based on Electrochemical Techniques for the Corrosion Assessment of RC Panels

Corrosion assessment of the steel bar in reinforced concrete (RC) structures is a very urgent for the structural health monitoring and life-cycle design in civil engineering. Half-cell potential map and guard ring techniques are applied as typical qualitative and quantitative methods to assess the corrosion status, respectively. A RC panel has been formed to be an actual testbed to verify the effectiveness of these techniques. Its potential map and corrosion rate have been investigated by the electrochemical sensors before and after NaCl solution injected, respectively. The results indicate the corrosion status of RC panels can be identified effectively.

Corrosion in Reinforced Concrete Panels: Wireless Monitoring and Wavelet-Based Analysis

To realize the efficient data capture and accurate analysis of pitting corrosion of the reinforced concrete (RC) structures, we first design and implement a wireless sensor and network (WSN) to monitor the pitting corrosion of RC panels, and then, we propose a wavelet-based algorithm to analyze the corrosion state with the corrosion data collected by the wireless platform. We design a novel pitting corrosion-detecting mote and a communication protocol such that the monitoring platform can sample the electrochemical emission signals of corrosion process with a configured period, and send these signals to a central computer for the analysis. The proposed algorithm, based on the wavelet domain analysis, returns the energy distribution of the electrochemical emission data, from which close observation and understanding can be further achieved. We also conducted test-bed experiments based on RC panels. The results verify the feasibility and efficiency of the proposed WSN system and algorithms.

Corrosion monitoring of reinforcing steel in RC beam by an intelligent corrosion sensor

Health degradation by corrosion of steel in civil engineering is a persistent problem. Structural health monitoring techniques can lead to improve estimates of structural safety and serviceability effectively. The corrosion sensor and the monitoring method have been explored and applied in RC beams corrosion monitoring. A novel five-electrode corrosion sensor has been developed to provide the platform for corrosion monitoring of the steel bar in concrete beam by electrochemical method. Half-cell potential of the RC beam has been measured to identify the corrosion statues of the steel bar qualitatively. Galvanostatic step method has been used to excite the steel-concrete system and the transient response of the system has been obtained. The data of the transient response has been analyzed by segmented method. Some important electrochemical parameters have been extracted by this method. The results show it is effectively to analyze the data of the transient response by segmented method.

Preparation and characterization of the solid‐state Ag/AgCl reference electrode for RC structures

Purpose – Corrosion sensors and networks are the most effective techniques to obtain the corrosion information and recognize the corrosion status of reinforced concrete structures. However, reference electrode is the key element to provide the baseline for potential control of the corrosion monitoring sensors during corrosion measurement process. Therefore, the purpose of this paper is to provide the novel solid‐state reference electrode for the corrosion sensors.Design/methodology/approach – A solid‐state Ag/AgCl reference electrode has been prepared. Furthermore, the performance of the reference electrode, such as stability, temperature response, anti‐polarization and influence of the concrete admixture, has been investigated.Findings – The results indicate that the balance potential and the temperature coefficient of the reference electrode are 3.64±1mv (vs. SCE) at 25°C and −0.51 mv/°C±0.03 mv/°C, respectively. Furthermore, the polarization curve exhibits characteristics of three stages as the polariz...

Potential Sensor Based on Electrochemical

The potential sensor is the key element and the major obstacle to realizing corrosion monitoring and control of the infrastructures in civil engineering. A novel solid-state potential sensor is prepared by the electron-beam physical vapor deposition technique. The phase composition of the oxidation film is investigated by X-ray diffraction. Also, the montmorillonite material with three-dimensional layered structure is used as the carrier material to prepare the conductive layer of the potential sensor. Furthermore, the potential stability of the sensor is verified in the simulated concrete pore solution. The results indicate that the potential sensor based on NiFe2O4 film is suitable to assembling the corrosion monitoring and control systems in civil engineering.

{\rm NiFe}_{2}{\rm O}_{4}

Health degradation by corrosion of steel in civil engineering, especially in rough environment, is a persistent problem. Structural health monitoring (SHM) techniques can lead to improved estimates of structural safety and serviceability. A novel all solid state-current confined corrosion sensor has been developed to provide the platform for corrosion monitoring of the steel bar in concrete beam by electrochemical method. Finite element method has been used to certify the current confined effect of the sensor. The sensors have been used in concrete beams to monitor the corrosion of the steel bar. Also, half-cell potential of the beam has obtained. The results shows that the corrosion sensor can effectively confine the current in the fixed area which is 45mm×π×Dsteel bar and the monitoring results of the corrosion sensor are accurate.