Development and application of cement-based piezoelectric composite in concrete behavior monitoring

Recent advances in sensor development have resulted in significant interest in developing new diagnostic techniques for damage detection of both existing and new structures. Depending upon the input signals, the structural diagnostic techniques can be divided into two types: passive sensing system without known inputs and active sensing system with known inputs. The objectives of this thesis are to develop and apply new smart composites for the sensing application of concrete material and structures.;The fabrication and property evaluation of 1-3 cement-based piezoelectric composites are emphasized. The cement-based piezoelectric composites maintain the high piezoelectric characteristics of the ceramic, and provide low acoustic impedance, similar as that of concrete material. The application of the sensors made of 0-3 composite is also summarized. It focuses on the electromechanical properties of the piezoelectric composite at relatively low frequencies (0.1 to 50 Hz) due to the special requirements of civil engineering structures.;The application of the transducers made of cement-based piezoelectric composite in ultrasonic and acoustic field is introduced in this thesis. In acoustic emission application, transducers made of the composite have broadband frequency response, which meets the requirement of AE detection. High sensitivity is also observed for the embedded cement-based transducers. That is crucial for damage monitoring for concrete structures. In ultrasonic application, the transducers are embedded into concrete specimens to generate or receive ultrasonic waves. Behaviors of cementitious material, such as the elastic modulus and hydration process, are characterized using the integrated ultrasonic system.;The work in this thesis opens a new direction for the application of cement-based piezoelectric composites in civil engineering. The materials and techniques, developed in this work, have a great potential in application of health monitoring for concrete structures.