The measurement of internal defect in the half-grouted sleeves by low frequency ultrasonics

Abstract

Half grouted sleeve connection has been widely used in the rebars connection of prefabricated concrete (PC) structure. Mostly, the implementation of grouted should be finished on site. Meanwhile, the internal defects are inevitable due to the concrete nature. Currently, there is few methods available, which can effectively and rapidly evaluate the quality of the connection. Therefore, in this paper, we propose a combination of low-frequency linear ultrasound (LUT) and nonlinear ultrasound (NLUT) to quantitatively characterize defect. The internal artificial defects are concentrated defects, and the defect content is 10%, 20%, 30% and 40% respectively. Through transmission mode was adapted for both LUT and NLUT. The UT wave propagation was distorted by different defects, which was the results of LUT. For NLUT with higher resolution, the complex distribution and different level of defect together will introduce nonlinearity. The experimental results show that the grouted defects reduce the ultrasonic energy of LUT, and increase the nonlinearity from NLUT with the increase of the defect size and randomness. The defect has a significant impact on the ultrasonic features. Therefore, Low-frequency LUT and NLUT methods are potential to realize the visualization the defects of half grouted sleeve connection.