Research On Rayleigh Wave Method And Its Application To Concrete Nondestructive Testing

As one of building materials widely used in modern construction, the quality of con-crete greatly affects structural safety performance. To ensure the structural safety, how to enhance monitoring and control of concrete quality becomes one of the important research subjects in constructional engineering.Routine concrete test is used for standard blocks produced in the same condition as concrete structures. Then the strength of concrete structures can be gotten from strength test of the blocks. But it is only the indirect test value of strength of concrete structures, which can't reflect the real state of concrete structures. And the test of block strength can't learn about the real strength of different parts of concrete structures (strength distribution), cer-tain the location and size of defects inside of concrete structures, and judge the degree of structure destroyed. Therefore, the measurement of blocks is only considered as the con-crete property reflection in a certain condition.NDT methods can avoid these deficiencies, with testing on the structural concrete directly and rapidly, strong adaptability and without destroying the structure itself. The paper finds that some methods are complexity in process, some ones are limited of test thickness (depth), and others are restricted by the larger oper-ating conditions, so all of them are difficult to meet the requirements of practical engineer-ing, after comparative analysis of the advantages and disadvantages of the common nonde-structive testing of concrete. At last, Rayleigh-wave method is used to test the quality of concrete structure.Rayleigh-wave test method makes use of the physical and mechanical properties in-formation arrayed by the propagation of Rayleigh-wave in the media, and then evaluates the physical and mechanical properties of the media by analyzing these propagation char-acters. In actual operation, the method is quick and easy, and has less disturbance to test objects. Further more, from testing conditions, Rayleigh-wave test method only needs one face to test the quality of concrete structures. Some scholars have studied concrete testing by use of Rayleigh-wave method, none of which is perfect. They mostly establish relation-ships between Rayleigh-wave speed and strength through statistical methods, or directly make use of relationships of Riley-wave speed and depth to reflect conditions inside the media. In previous studies, the scholars didn't study methods to extract Rayleigh-wave speed in concrete structures, nor brought forward that the compositive properties of media reflected by the Rayleigh-wave speed. Therefor it's not real that the quality of media is evaluated by relationships of Rayleigh-wave speed and depth.Therefore, to aim at the problems above, this paper's studies focus on two parts: one is to discuss the methods to extract Rayleigh wave dispersion curve and extraction of shear wave velocity; the other is to do ultrasonic testing and mechanical strength testing on dif-ferent strength concrete blocks. At last, it is expected to establish foundation for diagnostic evaluation of quality of concrete structures by use of elastic wave velocity through the re-search.