Monitoring Hydration Process of Concrete Made With Refuse‐Derived Fuel Ash Using EMI Method

Details of the investigations on an unexplored application of Electro Mechanical Impedance (EMI) technique using smart piezoelectric (PZT) sensors for damage detection of concrete shear wall structures under crack opening and closing is presented in this paper. The behavior and the ability of this method to detect damages, in a heterogeneous quasi-brittle material is studied for its effective utilization in structural health monitoring. The paper discusses the experimental investigations conducted on a concrete shear wall using PZT patches. Conductance data is acquired at different applied lateral displacements of shear wall. Damage in- dex is calculated using Root Mean Square Deviation (RMSD), Mean Absolute Per- centage Deviation (MAPD) and Correlation Coefficient (CC) computed between pristine and damaged states. It is found that compared to a metallic specimen, concrete specimens do not show a large variation in these damage metrics, due to reduced modal density and high damping. However, results and observations from these experimental case studies establish that EMI signature from surface bonded PZTs can identify damages even for a heterogeneous material like concrete, with improved and modified damage metrics.

This study explores the use of embedded piezo sensor (EPS) employing the Electro-Mechanical Impedance (EMI) technique for real-time corrosion monitoring in reinforced E-waste concrete exposed to chloride-laden environments. With the growing environmental concerns over electronic waste (E-waste) and the demand for sustainable construction practices, printed circuit board (PCB) materials were incorporated as partial replacements for coarse aggregates in concrete. The experiment utilized M30-grade concrete mixes, substituting 15% of natural coarse aggregates with E-waste, aiming to assess both sustainability and structural performance without compromising durability. EPS configured with Lead Zirconate Titanate (PZT) patches were embedded into both conventional and E-waste concrete specimens. The EPS monitored the changes in the form of conductance and susceptance signatures across a 100–400 kHz frequency range during accelerated corrosion exposure over a 60-day period in a 3.5% NaCl solution. The corrosion progression was evaluated qualitatively through electrical impedance signatures, visually via rust formation and cracking, and quantitatively using the Root Mean Square Deviation (RMSD) of EMI signatures. The results showed that the EMI technique effectively captured the initiation and propagation stages of corrosion. E-waste concrete exhibited earlier and more severe signs of corrosion compared to conventional concrete, indicated by faster increases and subsequent declines in conductance and susceptance and higher RMSD values during the initiation phase. The EMI-based system demonstrated its capability to detect microstructural changes at early stages, making it a promising method for Structural Health Monitoring (SHM) of sustainable concretes. The study concludes that while the use of E-waste in concrete contributes positively to sustainability, it may compromise long-term durability in aggressive environments. However, the integration of EPS and EMI offers a reliable, non-destructive, and sensitive technique for real-time corrosion monitoring, supporting preventive maintenance and improved infrastructure longevity.

Chee-Kiong SOH 1 & Yaowen YANG 2 ABSTRACT The electro-mechanical impedance (EMI) method is a relatively new nondestructive evaluation (NDE) method which uses the electro-mechanical coupling effect of piezoceramic Lead Zirconate Titanate (PZT) transducers to measure the force impedance of the structure. Due to the electro-mechanical coupling effect of the transducers, any changes in the mechanical impedance of the structure caused by the damage will affect the electrical impedance of the transducer. By comparing the impedance spectra of the damaged structure with the baseline, i.e., the impedance spectra for the pristine structure, the damage in the structure can be assessed. The quantity of the damage is assessed by a statistically calculated damage index, such as root mean square deviation or mean absolute percentage deviation or covariance change or correlation coefficient deviation. The EMI method has shown some advantages over the conventional NDE methods. However, it is not able to simultaneously identify the location and quantify the damage. This paper presents a technique integrating evolutionary programming and the EMI method to overcome this limitation. Essentially, the proposed technique first makes use of the EMI method to measure the variations of the electro-mechanical impedance of the structure. The damage is then identified by a system identification technique which is generally employed in the vibration-based method. Due to the numerous local optima in the search space, the traditional optimization strategies may not be able to find the correct solution. Evolutionary programming (EP) is then used as the system identification technique to find the global optimum. Thus, both the location and the quantity of the damage can be simultaneously identified. In order to enhance the integrated EP and EMI method, a fitness function, which can be generally applied to the other methods, is proposed to discriminate the variations caused by damages from the discrepancies caused by modelling errors. An experimental test is carried out on a cylindrical shell specimen to verify the damage detection results. The experiment demonstrated that both the location and the extent of damage can be simultaneously identified by the integrated EP-EMI method.

Grinding is considered one of the last processes in precision parts manufacturing, which makes it indispensable to have a reliable monitoring system to evaluate workpiece surface integrity. This paper proposes the use of the electromechanical impedance (EMI) method to monitor the surface grinding operation in real time, particularly the surface integrity of the ground workpiece. The EMI method stands out for its simplicity and for using low-cost components such as PZT (lead zirconate titanate) piezoelectric transducers. In order to assess the feasibility of applying the EMI method to the grinding process, experimental tests were performed on a surface grinder using a CBN grinding wheel and a SAE 1020 steel workpiece, with PZT transducers mounted on the workpiece and its holder. During the grinding process, the electrical impedance of the transducers was measured and damage indices conventionally used in the EMI method were calculated and compared with workpiece wear, indicating the surface condition of the workpiece. The experimental results indicate that the EMI method can be an efficient and cost-effective alternative for monitoring precision workpieces during the surface grinding process.

Nowadays, piezoelectric materials are most widely used in structural health monitoring (SHM) system for nondestructive evaluation. In this paper the damage study using electro-mechanical impedance (EMI) technique, which is nondestructive method of SHM. This paper presents a numerical analysis of four-story steel frame and multiple damages were induced in the steel frame by utilizing smart material like Lead Zirconate Titanate (PZT). A PZT-4 piezoelectric material was embedded in the beam of the frame. The type of damping used in steel frame model was Rayleigh damping. The numerical analysis was done in COMSOL MULTIPHYSICS 6.2 and frequency domain analysis was done, from that admittance values were find out for 30-300KHz frequency range. The real part of the admittance gives conductance values. Then, conductance verses frequency graph was created that will indicate the structural health and performance. Moreover, root mean square deviation (RMSD) index was found out for each case that provides a quantitative measure of deviation.

Many methods have been used in the past two decades to detect crack damage in steel joints of the offshore structures, but the electromechanical impedance (EMI) method is a comparatively recent non-destructive method that can be used for quality monitoring of the weld in structural steel joints. The EMI method ensures the direct assessment, analysis and particularly the recognition of structural dynamics by acquiring its EM admittance signatures. This research paper first briefly introduces the theoretical background of the EMI method, followed by carrying out the experimental work in which damage in the form of a crack is simulated by using an impedance analyser at different distances. The EMI technique is used to identify the existence of damage in the welded steel joints of offshore steel jacket structures, and Q345B steel was chosen as the material for test in the present study. Sub-millimetre cracks were found in four typical welded steel joints on the jacket platform under circulating loads, and root average variance was used to assess the extent of the crack damage.

Bolted connection is widely used in mechanical and civil engineering; however, in some cases, bolt looseness may cause catastrophic consequences. Bolt pre-load monitoring in real time can help to ensure the safety of component connections and durability of the entire steel structure. Previous research has demonstrated that a ‘smart washer (SW)’ fabricated by embedding a piezoceramic transducer into two flat metal rings could effectively detect the pre-load looseness of a bolted connection. The active sensing method, in which two SWs are necessary, was used in the previous research. In this research, an electro-mechanical impedance (EMI) method enabled by one ‘SW’ was developed to investigate the pre-load condition of a bolted connection. Since the installed SW is directly subjected to the same axial pre-load as that on the bolt, the piezoceramic SW with the EMI technique is uniquely suited for pre-load monitoring of a bolted connection. The pre-load reduction is directly reflected by the EMI of the piezoceramic SW. In particular, a decrease of the pre-load on a bolt connect results in the reduced of its resonant frequency, which can be revealed by the real part of the impedance. In addition, the root mean square deviation (RMSD) of the impedance signals was employed as an index to evaluate the bolt looseness degree. For the experimental study, a bolted connectional specimen with a piezoceramic SW was fabricated and investigated. In the experiment, eleven cases of different pre-loads on the bolt were studied. Experimental results clearly show that with the decrease of the bolt pre-load, the resonant frequency of the bolt joint also decreased, as reflected by the impedance of piezoceramic SW. In addition, experimental results demonstrated that the SW with the EMI based RMSD index can monitor bolt pre-load.

The Structural Health Monitoring (SHM) of concrete structures, including fiber concrete structures, receives increasing attention, and the Electromechanical Impedance (EMI)-based method is commonly used. The aim of using fiber reinforced concrete is to maintain the distress in small cracks regarding their width and range. The feasibility of the methodology was analyzed using EMI and a Lead Zirconate Titanate (PZT) patch on a fiber concrete cube to investigate the forthcoming damage. During tests, a repetitive compressive loading procedure was applied on a Fiber Reinforced Concrete Cube (FRCC), and the EMI values were measured. A well-known damage index was employed to analyze the signal values and evaluate test results. The results show that the index increases with the increase of the damage even though in very early damage states.

In India, sandstone was broadly used to construct structures like Agra Fort, Red Fort Delhi, and Allahabad Fort. Around the world, many historical structures were collapsed due to the adverse effect of damages. Structural health monitoring (SHM) is very useful to take appropriate action against the failure of the structure. The electro-mechanical impedance (EMI) technique is used to continuously monitor the damage. A piezoelectric ceramic (PZT) is used in the EMI technique. PZT is a smart material used as a sensor or an actuator in a certain specific manner. The EMI technique work in the 30 to 400kHz frequency range. This technique helped to analyze the hairline crack, location, and severity of damage to structural elements. A 10cm length and 5cm diameter sandstone cylinder was used in the experimental work. An electric marble cutter was used to create the artificial damages of 2mm, 3mm, 4mm, and 5mm respectively along the length, at the same place in specimens. The conductance signature and susceptance signature were measured for each depth of damage. The comparative result of healthy and damaged state with different depth were concluded based on the conductance signature and susceptance signature form the sample. Statistical methods like root mean square deviation (RMSD) is used for the quantification of damage. The sustainability of sandstone has been analyzed with the help of the EMI technique and RMSD values. This paper motivates the application of the EMI technique to the historical building made of sandstone as key material.

In the present study, Electromechanical Impedance (EMI) technique is utilized to assess the application of the microbially induced calcium carbonate precipitation (MICCP) to restore the integrity of cracked concrete. The artificial crack width of approximately 0.5 mm is healed autonomously using a bacteria-based healing agent, using flyash (FA) as a carrier material. Lead Zirconate Titanate sensors were bonded on the cracked specimen to monitor the continuous healing process. The EMI signatures were captured over the healing period using an impedance analyser in the frequency range of 100 to 250 kHz. Statistical crack healing indicator, root mean square deviation (RMSD) was employed for evaluating crack efficiency based on extracted signatures. Results revealed that the RMSD values were effective in quantifying the progressive healing achieved due to MICCP precipitation. This is the first study with a successful implementation of the EMI technique to monitor the crack sealing in concrete through MICCP. Healing capacity was also correlated with the crack width reduction that was evaluated by optical imaging of repaired cracked surface. Also, the bacterial mineralization products were analyzed by FESEM, EDX, XRD and TGA. The results give clear proof that the FA-based carrier material can be effectively used in healing the cracks.

In this paper idea of load and structural health monitoring (LSHM) system for assessment of composite powerboat has been presented. One of the structural health assessment method utilised in this system is electromechanical impedance (EMI). Authors have presented results related to influence of load and temperature on EMI method. EMI method is based on electromechanical coupling of piezoelectric transducer (PZT) with host structure. Due to this coupling, mechanical resonances of structure can be seen in electrical impedance characteristic of PZT. According to the literature EMI method is sensitive to change of loads in the structure and to changing temperature. Influence of changing operation and environmental conditions should be eliminated by compensation algorithms in order to reduce risk of false alarms in damage assessment system. Results of research related to simple specimen experienced the influence of changing temperature and transverse load and EMI method have been presented. Strains at bending condition for beam have been measured using fibre Bragg grating strain sensors. Some preliminary results of measurements related to powerboat have been also presented and discussed. Measurements have been related to self-diagnosis of piezoelectric transducers using EMI method and to measurements of accelerations using MEMS accelerometer.

A state-of-the-art review of concrete strength detection/monitoring methods: With special emphasis on PZT transducers

The modulus of elasticity of concrete (Ec) is an essential parameter commonly used in concrete design, concrete curing monitoring, and deterioration evaluation and damage detection of concrete structures. A quick and reliable in situ determination of Ec helps in accurate decision‐making for construction and maintenance. The electromechanical impedance (EMI) technique using surface‐bonded lead zirconate titanate (PZT) patches (referred to as SBP) has become a popular nondestructive method for monitoring concrete structures due to ease of operations. The existing research mainly utilized baseline‐dependent approaches to monitor the changes (e.g., hardening or damage evolution) of concrete structures. However, relevant baselines are greatly influenced by the status of PZT sensors and bonding layers, limiting the practical applications of this technique. This paper presents a baseline‐free EMI resonance method for measuring Ec of concrete without using prior baseline data for the first time. Numerical and experimental studies on standard concrete cubes (100 mm in width) with SBP were conducted to examine the proposed method. A dimensionless physical quantity was first proposed to view the EMI signals. Then, resonance peaks highly related to concrete properties but insensitive to the status of the sensor system were selected, physically described, and correlated to the concrete parameters through numerical analyses. Finally, experimental validations, covering the measurement of Ec, repeatability of the chosen resonance peaks, and temperature effects, were conducted to illustrate the proposed method’s stability, accuracy, and sensitivity.

This work investigates the application of structural health monitoring (SHM) in a dynamic environment with the electromechanical impedance (EMI) method. Classically, the EMI method monitors civil or mechanical structures for damage in static environments. Advances in data acquisition (DAQ) now allow the possibility of rapid damage detection in dynamic environments. An impact-based experimental setup is developed to create a repeatable dynamic event through a collision between a pneumatically actuated striker bar and a static incident bar instrumented with a piezoelectric transducer. The EMI method is employed to detect the change of state at the interface of the two colliding bars. Experimental results prove the pneumatic launching system is capable of repeatable dynamic events, but the duration of contact is only 0.03 ms and the current DAQ system is incapable of detecting the event. A 3D printed programming material interface is placed at the location of impact to increase the duration of contact to approximately 1 ms. An excitation signal is created to continuously sweep a 0.5 ms chirp signal with a frequency bandwidth from 60–70 kHz (previously identified damage sensitive frequency bandwidth from static testing) for 7.5 seconds. Results indicate that due to the sampling rate and sweep time of the excitation signal, the frequency resolution is not adequate to properly assess if the impact is detected. Improvements in the DAQ hardware must be considered for future work.

This paper describes the electromechanical impedance (EMI) method based structural health monitoring using sensor data fusion approach. The data fusion of different attributes is more effective over a single data in achieving reasonable accuracy and precision. The paper investigates an electromechanical impedance (EMI) method applied to the structural health monitoring of sensor network of thin composite plates using distributed sensor data fusion techniques and a single sensor for different levels of delamination. The information from multiple sensors and single sensor is studied in the frequency domain and a new optimized fused criteria of variable admittance (Y) and conductance (G) is explained by damage metric root mean square deviation (RMSD). The experiments are performed on a thin composite plate with attached piezoelectric transducers at different locations and a plate with single transducer with different delamination levels.