Research On Kaiser Effect Of Acoustic Emission In Concrete Under Uniaxial Tension

Concrete is a type of heterogeneous material with micro-cracks and its failure procedure is much more complicated than the ideal brittle material. The technology of Acoustic Emission (AE) can detect the variation of microstructure in material and can help to explore the failure mechanism of concrete under uniaxial tension. However, the application of AE technology for concrete under uniaxial tension is at the beginning, and there are so many problems to be studied and solved, such as the influence of Kaiser effect on the characteristic of Acoustic Emission in concrete under uniaxial tension. In order to make a base for applying AE technology in exploration the failure mechanism of concrete under uniaxial tension and to supply information for the application of Kaiser effect in engineering practice, research on Kaiser effect of Acoustic Emission in concrete under uniaxial tension will be executed and the influence of Kaiser effect on the characteristic of Acoustic Emission in concrete will be studied, as a subproject of the Supervisor' project "the Key Project of National Natural Science Fund of China".The possible testing plan for Kaiser effect is present based on the research result of Kaiser effect of Acoustic Emission already obtained at home and abroad. The existence and the existence condition of Kaiser effect are studied in the uniaxial tension test of Acoustic Emission in concrete. Also, the influencing factors of Kaiser effect are analyzed in detail and the application of Kaiser effect in engineering practice is discussed. Seventy specimens are tested in the study. The main contents of this paper are as follows:1) The existence of Kaiser effect and the stress range in which Kaiser effect exists are studied in the uniaxial tension test of Acoustic Emission in concrete. The mechanism of Kaiser effect is explained. The relationship between Kaiser effect and Felicity effect is analyzed, and the contents which Kaiser effect remembers are also discussed.2) The influencing factors of Kaiser effect such as loading pattern, loading rate, grade of strength, size of specimen, aggregate size, stress level, time delay and wet-dry condition are discussed and analyzed.3) The application of Kaiser effect such as noise-checking for AE test, stress historic evaluation, estimation of concrete deterioration level and the assessment of reliability of concrete are discussed.Through the work mentioned above, several main conclusions are as follows: Firstly, the existence of Kaiser effect in concrete in uniaxial tension test is validated. This is the result of the irreversibility of concrete damage. Secondly, Kaiser effect exists under certain stress range, the upper limit of which is about eighty two percent of ultimate tensile strength. Thirdly, Felicity ratio can discribe the inreversibility of Acoustic Emission clearer. It decreases monotonically with the stress increase. When the stress reaches the upper limit of stress level, Felicity ratio decreases rapidly, Kaiser effect disappears, and Felicity effect appears. Fourthly,...