Research On Acoustic Emission Characteristics Of Concrete Based On Embedded Piezoelectric Sensor

Since the advent of concrete in the last century,due to its relatively low cost and durability,it has gradually developed into the largest amount of building materials in today’s engineering field.In the mass concrete structure,it has the characteristics of large amount of concrete,thick structure size and complex construction technology.In order to avoid the large temperature stress caused by the high internal temperature in the construction process,which makes the concrete structure produce temperature cracks,thus affecting the safety and durability of the structure,it is necessary to monitor the early age hydration process of mass concrete.As a kind of dynamic non-destructive testing technology,acoustic emission technology can monitor the safety of structure in real time,on-line,and is conducive to the analysis of the damage principle of the structure in the later stage.Compared with the traditional testing technology,it has the advantages of rapid response,wide monitoring range,high sensitivity,and not limited by the geometric size of materials.Based on this,the self-made 1-3 cement-based piezoelectric sensor is embedded in concrete,and the early hydration process of concrete is monitored by acoustic emission detection technology.(1)According to the requirements of acoustic emission monitoring concrete hydration experiment,a stable and effective PZT-5 piezoelectric sensor was prepared,and its high temperature performance was studied.(2)The hydration process of cement-based composites with different length(cement paste,cement mortar and concrete)and different water cement ratio was monitored by using commercial external PAC sensor and acoustic emission technology.The similarities and differences of acoustic emission signals of early hydration of various types of concrete are analyzed.(3)Based on ANSYS finite element simulation software,the temperature field of fan foundation mass concrete is simulated,and the internal temperature change of concrete structure is obtained.At the same time,the temperature monitoring and acoustic emission monitoring experiments of the fan foundation are carried out,and the relationship between the acoustic emission signal and the temperature change in the early stage of the mass concrete structure is obtained.The results show that PZT-5 piezoelectric sensor has good sensitivity and temperature adaptability to the acoustic emission signal of concrete,and can be applied to the early hydration monitoring of concrete.By monitoring the hydration process of concrete at early age,the correlation between hydration process and time is obtained,the error between finite element simulation and actual temperature monitoring is analyzed,and the variation law of acoustic emission signal at each position in mass concrete is sorted out,which enriches the theory of structural health monitoring in civil engineering.