Cement-based Piezoelectric Sensor Research Articles

Experimentation and simulation study of electromechanical response characteristics of a 2-2 type cement-based piezoelectric composite sensor

In the manuscript, the piezoelectric functional element was prepared by slicing and adding method using piezoelectric ceramic PZT-5H and ordinary silicate cement 42.5 was as base materials, and then a 2-2 type cement-based piezoelectric composite sensor was prepared by an encapsulated epoxy resin. The experimental and simulation analysis was carried out to obtain the quasi-static linear sensitivity of the electromechanical response of the sample under conditions of compressive loading. The development process of the sample from local failure to overall fragmentation was observed using a high-speed camera. Found that the electrical nonlinear threshold of 35 MPa appeared before the mechanical nonlinear threshold. Further, the results showed that when the loading frequency was increased from 5 to 15 Hz under equal amplitude, the response waveform remained unchanged, however, the electrical displacement was attenuated by 19.7%. Packaging schemes using various lengths and thicknesses of an epoxy layer were conducted by using simulation. It is indicated that, under the premise of ensuring the protection package and considering the manufacturing process, the length of the package side could increase appropriately, and the single-side package side length is set to 4 mm. When the thickness of the package layer becomes less, it would be better.

Cement-based piezoelectric composite sensor designed for charactering the three-dimensional stress state in concrete

We reported a sensor, designed based on the specific working modes of piezoelectric, to characterize the three-dimensional (3-D) stress state in concrete. The sensor contains 6 piezoelectric elements: 3 elements working in normal mode to measure the normal stress, and 3 elements working in shear mode to measure the shear stress. Cement-based piezoelectric composite, fabricated by cutting-filling method, was used to fabricate the sensor, as it has better mechanical compatibility with concrete than piezoelectric ceramics. By embedding the sensor into a cement mortar column, we systematically characterized its performance under dynamic uniaxial load from 3.0 MPa to 7.5 MPa with frequency from 1 Hz to 20 Hz. Results demonstrate that the sensor can measure the 3-D stress state in concrete well, and has good linearity, high sensitively, and excellent working bandwidth. The cross sensitivities of the sensor were also calculated and discussed.

Electromechanical impact analysis of 2–2 cement-based piezoelectric sensor considering resistor

The model of the 2–2 type cement-based piezoelectric sensor, which is connected with a resistor while under the impact mechanical load, is established in this article. The dynamic theoretical expressions are acquired by utilizing the separation variable method and the matrix coefficient method and then used to analyze and discuss the electrical properties and the influence of the resistance value, which is verified correctly by numerical analysis. Also, the effect of resistor value and different material parameters on dynamic properties of such sensor is further investigated. And a reverse voltage is proposed to balance the displacement of the free-end and the stress of the fixed-end to enhance the safety. At last, the acoustic impedance ratio associated with the compatibility of the composite is discussed. The conclusions discussed in this work could provide some theoretical references for optimizing the design of the 2–2 cement-based piezoelectric sensor connected to electrical components in practical application.

Impact Mechanical Response of a 2-2 Cement-Based Piezoelectric Sensor Considering the Electrode Layer Effect.

Cement-based piezoelectric composite, has been widely used as a kind of smart material in structural health monitoring and active vibration control. However, transient dynamic loads such as impact loads may cause serious damage to the composite. Considering the electrode layer effect, this paper aimed to investigate the theoretical response of a 2-2 cement-based piezoelectric composite sensor subjected to an impact load. The vibration behaviors are analyzed by using the mode summation method and the virtual work principle. To simulate the impact load, transient haversine wave loads are assumed in the numerical simulation. Close agreements between theoretical and numerical solutions are found for peak transient haversine wave loads larger than 500 kPa, therefore proving the validity of the theory. Moreover, the influence of the electrode material and geometrical parameters on the dynamic characteristics of this sensor are considered. The present work should be beneficial to the design of this kind of sensor by taking into account the electrode layer effect.

Steel corrosion in magnesia–phosphate cement concrete beams

The acoustic emission (AE) technique was employed to investigate the corrosion-induced deterioration of steel-reinforced magnesia–phosphate cement (MPC) concrete beams under the coupling effect of loading and accelerated chloride diffusion. A cement-based piezoelectric sensor was used for AE detection owing to its high sensitivity and good compatibility with the concrete matrix. Power spectral density analysis and continuous wavelet transform were used to process the detected AE signals. It was found that the average frequency shift was closely related to the damage accumulation level in the reinforced MPC concrete beams. Based on the frequency characteristics of the detected AE signals during wet–dry cycles, the corrosion-induced degradation process of MPC beams was divided into three stages, from micro-cracking to localised macro-crack propagation. Wavelet analysis revealed the energy density distribution of the AE waveform, which was used to differentiate signal features between reinforcement corrosion and concrete cracking. In addition, comparisons in terms of the accumulated AE event number and half-cell potentials showed that MPC and OPC concrete had comparable corrosion inhibition capabilities.

In-situ crack propagation monitoring in mortar embedded with cement-based piezoelectric ceramic sensors

This paper describes a study on using embedded cement-based piezoelectric ceramic sensors to detect crack propagation in mortar specimens under cubic-splitting load by acoustic emission (AE). The main objective is to characterize the fracture process in mortar specimen in the cubic-splitting test. AE sensors (piezoelectric composites as core elements, and a mixture of cement, epoxy resin and hardener as packaging material) can be embedded into concrete and still have broadband frequency response and good matching ability with the cement material. The three-dimensional localization of the AE sources, signal-based AE energy index and variation characteristics of the AE frequency content were used to explain and quantitatively evaluate the fracture processes of the mortar specimens. The results show that the fracture processes in the mortar under the cubic-splitting are evidently brittle fracture and the variation behaviors of the AE frequency content, which exhibited a close relationship with the applied loading processes during the tests. It was also found that the application of cement-based piezoelectric ceramic sensors by means of AE represents a good option to analyze the crack growth in the specimens under increasing load, the location of the cracks and, in addition, it offers the potential for in-situ application.

In-Situ Structural Health Monitoring of a Reinforced Concrete Frame Embedded with Cement-Based Piezoelectric Smart Composites

ABSTRACTThe application of a novel cement-based piezoelectric (PZT) ceramic sensor to the in-situ stress-time history monitoring of a reinforced concrete frame structure is described in this article. Smart frame composite structures were produced and characterized by a range of experimental methods. ADINA, a finite element analysis program, was used to analyze the mechanical response of the concrete frame under static loading. The results show that the mechanical-electrical response of sensors embedded in a reinforced concrete frame structure follows a linear relationship under various loading conditions. The sensors are able to record the stress history of the frame under static loads. Moreover, the measured stress maxima agree well with the simulated results, and the smart structure is found to be capable of reliably monitoring the response of a frame structure during stress testing for different loading modes to real concrete structures. The study indicates that such cement-based PZT composites have a high feasibility and applicability to the in-situ stress-time history monitoring of reinforced concrete structures.

In situ stress monitoring of the concrete beam under static loading with cement-based piezoelectric sensors

In this paper, the application of a novel cement-based piezoelectric ceramic sensor is stated for the in situ stress monitoring of the reinforced concrete beam under static loading. Smart beam composite structures were designed and characterised by a range of experimental methods. Finite element analysis is used to analyse the mechanical response of the concrete beam under static loading. The results show that the mechanical–electrical response of sensors embedded in reinforced concrete beams follows a linear relationship under various loading conditions. The sensors are able to record the stress history of the beam under static loads. Moreover, the measured stress data agree well with the simulated results and the smart structures are found to be capable of reliably monitoring the response of a beam during stress testing for static loading modes to real concrete structures. The study indicates that such cement-based piezoelectric composites have a high feasibility and applicability to the in situ stress monitoring of reinforced concrete structures.

Processing method and property study for cement-based piezoelectric composites and sensors

The cement-based piezoelectric composite is developed to fabricate smart sensors in real-time structural health monitoring. The cement-based piezoelectric sensor is suitable for applications in civil engineering because of its good compatibility in acoustic impedance. The 0–3 cement-based piezoelectric composites were fabricated by mixing the cement particles and lead zirconate titanate powders under high pressure in this paper. The parameters including the piezoelectric factors, relative dielectric constant ɛr, thickness and planar electromechanical coupling coefficients of cement-based composites with different lead zirconate titanate ceramic contents were measured to characterise the electromechanical coupling properties. Further, the acoustic impedance was detected to test acoustic compatibility with concrete materials. Laboratory tests show that the voltage output of the sensor is linearly proportional to the applied pressure. The cement-based piezoelectric sensors have better mechanical–electrical conversion property than pure ceramic sensors. The findings indicate that the 0–3 cement-based piezoelectric sensor meets all requirements of application in construction engineering, and is feasible to be utilised in concrete structures.

A new smart traffic monitoring method using embedded cement-based piezoelectric sensors

Cement-based piezoelectric composites are employed as the sensing elements of a new smart traffic monitoring system. The piezoelectricity of the cement-based piezoelectric sensors enables powerful and accurate real-time detection of the pressure induced by the traffic flow. To describe the mechanical-electrical conversion mechanism between traffic flow and the electrical output of the embedded piezoelectric sensors, a mathematical model is established based on Duhamel’s integral, the constitutive law and the charge-leakage characteristics of the piezoelectric composite. Laboratory tests show that the voltage magnitude of the sensor is linearly proportional to the applied pressure, which ensures the reliability of the cement-based piezoelectric sensors for traffic monitoring. A series of on-site road tests by a 10 tonne truck and a 6.8 tonne van show that vehicle weight-in-motion can be predicted based on the mechanical-electrical model by taking into account the vehicle speed and the charge-leakage property of the piezoelectric sensor. In the speed range from 20 km h−1 to 70 km h−1, the error of the repeated weigh-in-motion measurements of the 6.8 tonne van is less than 1 tonne. The results indicate that the embedded cement-based piezoelectric sensors and associated measurement setup have good capability of smart traffic monitoring, such as traffic flow detection, vehicle speed detection and weigh-in-motion measurement.

Fabrication of 1-3 Cement-Based Piezoelectric Ultrasonic Sensors for NDE Applications

This paper described fabrication and comparison of embedded ultrasonic sensors for NDE applications. A 1-3 cement-based piezoelectric composite was used as the sensing element of the ultrasonic sensor. As a front matching layer between test material and piezoelectric materials, cement/epoxy resin was selected. In order to make the backing materials for sensors had enough acoustic attenuation performance, the backing material of sensors doped with tungsten powder. When the mass ratio of tungsten/cement backing was two and the thickness of cement/epoxy resin front-face matching was 3mm, the 1-3 cement-based piezoelectric ultrasonic sensor showed a significant enhancement in both relative pulse-echo sensitivity and-6dB bandwidth. These promising results suggested the great potential for developing high-performance ultrasonic sensors using the 1-3 cement-based piezoelectric composite.

Research on a 0–3 cement-based piezoelectric sensor with excellent mechanical–electrical response and good durability

In this study, a novel cement-based piezoelectric sensor was prepared with 0–3 cement-based piezoelectric composites as the sensing element and a mixture consisting of epoxy resin and cement as the encapsulation part, and its mechanical–electrical response measurement was carried out by dynamic load. To realize effective load transmission from the structural material to the sensing element, and to better evaluate and improve the sensor durability, the optimum encapsulation system and sensing element location were explored, and the durability of the cement-based piezoelectric sensor under complicated conditions was studied in detail. Results indicated that the sensor possessed excellent linear performance, with the regression confidence exceeding 0.99 in a large range of 0.31–2.34 MPa, when the ratio of cement to epoxy resin was 3:1 and the sensing element was put in a position near the underside of the encapsulation material. The phase shift between the output voltage and input load was nearly zero and the sensor could respond to pulse load quickly. Environmental conditions including fatigue load and water had a negligible effect on the linearity and sensitivity (slope of fitting line) of the sensor, and in the intended temperature range of 0−40 °C the sensor showed good linearity, almost independent of temperature; nevertheless, the output voltage increased with increasing temperature and the sensitivity reached 1811 mV MPa−1 at 40 °C. Generally, the sensor prepared in this research had excellent mechanical–electrical response and good durability.

Ultrasonic monitoring of the early-age hydration of mineral admixtures incorporated concrete using cement-based piezoelectric composite sensors

The early-age hydration processes of concretes with mineral admixtures have been monitored and evaluated by a newly developed ultrasonic method based on embedded cement-based piezoelectric composite sensors. With the embedded ultrasonic (P-wave) measurement system, the waveform, wave velocity, attenuation coefficient index, and frequency-domain spectrum of detected ultrasonic waves during hydration can be recorded. The mineral admixtures examined include fly ash, slag, and silica fume, which replace part of the cement in concrete mixtures. It is found that the ultrasonic transmission parameters can be related to the microstructure changes of the concrete. Both the acceleration effects of silica fume and the retardation effects of fly ash and slag on the early hydration of concrete can be determined and explained through the analysis and comparison of the characteristics of the velocity curves. The attenuation coefficient index curve provides additional observation for the study of hydration kinetics. Moreover, the function of fresh concrete in filtering the high-frequency component of the wave varies with time, and concrete can be considered as low-pass frequency spectral filter. Frequency spectra analysis at different ages of fresh concrete provides useful information to reveal the early-age hydration process.

Corrosion monitoring of reinforced concrete beam using embedded cement-based piezoelectric sensor

The corrosion of reinforcement is a well-recognised problem in the maintenance of concrete structures that can lead to reduction of the cross-section of the rebar, thus weakening the load-carrying capacity of the structure. Under ordinary design conditions, cracks are allowed to appear in concrete beams. However, the existence of cracks can speed up the corrosion rate of reinforcement significantly. In this study, the corrosion activities of reinforcement in concrete beams with or without cracks under accelerated corrosion conditions were monitored using embedded cement-based piezoelectric composite sensors and the acoustic emission (AE) technique. The AEs generated by the initiation of localised corrosion and subsequent concrete cracks were successfully detected and recorded by a home-programmed DEcLIN monitoring system. Based on frequency domain identification, useful information was extracted to explain the process of deterioration of concrete structures. It was found that cement-based piezoelectric sensors show a good capability in AE detection and the beam with cracks corroded much earlier than the case without cracking, consequently resulting in early deterioration.

Effect of Backing Materials on the Performance of Cement-Based Piezoelectric Ultrasonic Sensors

In order to increase the sensitivity, frequency bandwidth and longitudinal resolution of the 1-3 cement-based piezoelectric ultrasonic sensor, different metal powder/epoxy resin composite materials were used to make backing layer, and the performances of sensors were evaluated and compared. The results indicated that the increase of the sensitivity and the frequency bandwidth, as well as a decrease of the pulse wave number can be observed when the backing materials of metal powder/epoxy resin composite materials were added to the sensor. A 42%-increase of the maximum peak-to-peak value of the echo pulse response, a 52%-reduction of the ring down time and a 200%-increase of the bandwidth can be achieved by using the backing material.

Study on hydration process of early-age concrete using embedded active acoustic and non-contact complex resistivity methods

The microstructure development of early-age concrete during hydration process was investigated by means of embedded active acoustic and non-contact complex resistivity monitoring methods. Embedded active acoustic method utilized cement-based piezoelectric sensors and FEbLIN acoustic system to continuously emit and receive compressional acoustic wave. Signal-based parameters such as velocity, attenuation and frequency domain spectrum variation were evaluated to analyze the microstructure development of early-age concrete. Meanwhile, non-contact complex resistivity method was utilized to measure real-time electrical impedance of early-age concrete. These two innovative non-destructive testing methods have distinguished merit. Compressional acoustic wave is sensitive to the connectivity of the solid phase network in the fresh concrete. It continuously hunts for the shortest propagation path during monitoring. While the inducted current generated in impedance measurement is more sensitive to the liquid phase network conditions of the fresh concrete. It strictly adopts the transition path with lowest electrical impedance. In this study, the behaviors and properties of fresh concrete are interpreted based on the measurement results of these two methods. It is found that the hydration stages can be distinguished according to the characteristics of acquired parameters, and so does the maturity of concrete.

Stress Test of CFRP Confined Concrete Short Column under Axial Load Based on Cement-Based Piezoelectric Sensor

This paper presents a new method of direct stress test in the core area of CFRP confined concrete short column by using cement-based piezoelectric sensor. The sensors are embedded in the core area of concrete short columns, dynamic fatigue tests are taken on the columns before and after CFRP reinforcement respectively. The results show that an obvious linear relation is found between sensor output signal and test input load, the slope of load-sensor signal curve of concrete short column is larger after CFRP reinforcement, the sensor signal peak is increased with the increase of the loading frequency, but the loading frequency is almost no effect on the increasing extent of the stress, the stresses in the core area of concrete short columns can be significantly improved after the columns reinforced by CFRP, the increment percentages are in the range of 5% ~ 20%.

Study of the Relationship between Concrete Fracture Energy and AE Signal Energy under Uniaxial Compression

When cracks occur in concrete, released fracture energy will be proportionally transformed into the energy contained in acoustic emission (AE). According to this physical phenomenon, AE technology provides an effective monitoring method for fracture process of concrete through acquiring generated AE. However, such monitoring is limited in qualitative evaluation of fracture process under most occasions. Quantitative interpretation of fracture process is difficult to accomplish by simply acquiring the amount of AE generated or conducting parameter-based AE analysis. This paper investigates the feasibility of reflecting the fracture energy released during fracture by means of evaluating the energy index of detected AE signals. An effective fracture model based on fracture behavior of concrete cylinder under uniaxial compression is introduced here to provide a mathematical relationship between acquired AE energy index and crack formation energy of concrete. Apart from reasonably estimating the energy consumed for crack formation, cement-based piezoelectric sensors are embedded inside the concrete to carry the task of detecting AE and transforming its energy into the electrical energy of AE signals. On the basis of experimental study, the energy of detected AE signal is satisfactorily correlated to the corresponding fracture energy and quantitatively represents the fracture energy releasing process of concrete during the period of stable cracks development. DOI: 10.1061/ (ASCE)MT.1943-5533.0000418. © 2012 American Society of Civil Engineers.

Signal-based AE characterization of concrete with cement-based piezoelectric composite sensors

The signal-based acoustic emission (AE) characterization of concrete fracture process utilizing home-programmed AE monitoring system was performed for three kinds of static loading tests (Cubic-splitting, Direct-shear and Pull-out). Each test was carried out to induce a distinct fracture mode of concrete. Apart from monitoring and recording the corresponding fracture process of concrete, various methods were utilized to distinguish the characteristics of detected AE waveform to interpret the information of fracture behavior of AE sources (i.e. micro-cracks of concrete). Further, more signal-based characters of AE in different stages were analyzed and compared in this study. This research focused on the relationship between AE signal characteristics and fracture processes of concrete. Thereafter, the mode of concrete fracture could be represented in terms of AE signal characteristics. By using cement-based piezoelectric composite sensors, the AE signals could be detected and collected with better sensitivity and minimized waveform distortion, which made the characterization of AE during concrete fracture process feasible. The continuous wavelet analysis technique was employed to analyze the wave-front of AE and figure out the frequency region of the P-wave & S-wave. Defined RA (rising amplitude), AF (average frequency) and P-wave & S-wave importance index were also introduced to study the characters of AE from concrete fracture. It was found that the characters of AE signals detected during monitoring could be used as an indication of the cracking behavior of concrete.

Frequency characteristic analysis on acoustic emission of mortar using cement-based piezoelectric sensors

Acoustic emission (AE) monitoring was conducted for mortar specimens under three types of static loading patterns (cubic-splitting, direct-shear and pull-out). Each of the applied loading patterns was expected to produce a particular fracture process. Subsequently, the AEs generated by various fracture or damage processes carried specific information on temporal micro-crack behaviors of concrete for post analysis, which was represented in the form of detected AE signal characteristics. Among various available characteristics of acquired AE signals, frequency content was of great interest. In this study, cement-based piezoelectric sensor (as AE transducer) and home-programmed DEcLIN monitoring system were utilized for AE monitoring on mortar. The cement-based piezoelectric sensor demonstrated enhanced sensitivity and broad frequency domain response range after being embedded into mortar specimens. This broad band characteristic of cement-based piezoelectric sensor in frequency domain response benefited the analysis of frequency content of AE. Various evaluation methods were introduced and employed to clarify the variation characteristics of AE frequency content in each test. It was found that the variation behaviors of AE frequency content exhibited a close relationship with the applied loading processes during the tests.