Jinrui Zhang

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 Duhamels 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.

Determination of adsorption mechanism of polycarboxylate-ether based superplasticizers using crystallization, thermal and mass spectrometry methods

In this study, a series of suspensions were fabricated by dispersing calcium carbonate (CaCO3), cement and silica fume into a polycarboxylate-ether plasticizer (PCE)/water solution. The PCE used was a comb-like copolymer containing a sodium polymethacrylate (PMA) backbone partially esterified with polyethyleneglycol (PEG) side chains. Sedimentation and optical microscopy tests indicated that both CaCO3 and cement could form homogeneous suspensions. The crystallization behavior of the PEG side chains revealed that PEG had stronger interactions with CaCO3 than with cement and silica fume particles, which was further confirmed by differential scanning calorimetry (DSC) and thermogravimetric analysis (TGA). A detailed time-of-flight secondary ion mass spectrometry (ToF-SIMS) examination suggested that PEG was mainly located on the surfaces of the CaCO3, and the PMA backbones were mainly located on the surfaces of the cement and silica fume, respectively. The different interactions between copolymer and inorganic particles were associated with their interfacial tensions, and had a remarkable influence on the paste fluidity.

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

Abstract 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.