Defect detection of grouting sleeve connection with energy ratio change in frequency domain

Abstract

Controlling the grouting density is the key to ensure the construction quality of precast structures. Since the grouting sleeve is embedded in concrete, it is difficult to detect the grouting compactness of the sleeve. In this paper, the frequency domain analysis technique is used for non-destructive testing of concrete components with grouting defects. The collected ultrasonic testing signals are calibrated-denoised-decomposed-reconstructed. The damage degree of the grouting signal is evaluated and analyzed by quantifying the energy value of different frequency signals with two norms. Considering the effect of the random distribution of aggregates on the propagation of ultrasonic stress waves, a three-dimensional multi-point detection model and a two-dimensional plane single-point model based on piezoelectric effect are set up respectively. Results show that frequency energy distribution of the grout-deficient signal is concentrated to low-frequency range than that of grout-compact signal. When grouting defect accumulates to a certain extent, the main frequency may move from high-frequency band to lower-frequency band. Although the aggregates in different concrete components are randomly distributed, the test results of the two-dimensional plane model show that the validity of the defect quantitative index is 72%. The experimental tests results show that the method of using frequency energy transfer to lower-frequency band to determine grouting defects is effective, with a detection validity of 66.7%. Therefore, the non-destructive testing method for grouting sleeve compactness proposed in this paper can provide reference for engineering testing application.