Experimental Researches On Grout Quality Detection Of Tendon Ducts

In the recent decades, as the fast development of road constructions in China, a large of the post-tensioned concrete structures were used widely. How to control the "lifeline"—the strands of the long-span bridges in the bridge construction period and the corrosion problems of the strands have become more and more urgent. The key to solve this problem is the density of the cable grouted ducts. In 2001, poorly grouted tendon duct was classified as one of the top ten quality defects in construction of roads and bridges by Ministry of Communications of the People's Republic of China. According to the quality defects generated on internal grout condition of tendon ducts, the comprehensive analysis of the common cable ducts of deficiencies in internal as well as the research of non-destructive testing technique for grout quality at home and abroad were performed. Based on the comprehensive exposition of the theory of non-destructive testing, such as ultrasonic, impact echo, ground penetrating radar technology, the study focused on internal grout condition evaluation of tendon ducts and detecting depth of the three non-destructive testing methods. The combination of three methods could give full play to their own advantage and make up for there weaknesses to solve some practical problems of engineering.1. The reasons for the quality status and existent problems of the prestressed grouted pipe were introducted. The necesserity and urgency of nodestructive qualilty testing technique for prestressed pipe grouting and the current detection methods with existent problems were summarized. The application techniques of ultrasonic waves, impact-echo method and ground penetrating radar on pipe grouting quality testing were mainly discussed. The utilization of three methods which could fully and comprehensively test various problems were proposed.2. This thesis is composed of three chapters, introducing the propagation characteristics through medium, technical parameters and the basic detection principles of ultrasonic waves, impact-echo method and ground penetrating radar. Three methods are systematically discussed and would provide theoretical basises for further study.3. The fundamental principle of ultrasonic-waves method is that observing the relative variation of acoustic parameters, such as sound (velocity) or amplitude, to analyze whether the quality of duct grouting is good. In terms of the experimental research, ultrasonic-wave method as testing technology for duct grouting was futher studied and the best acoustical parameters were evaluated.4. As a new type of non-destructive testing technology, impact-echo method was applied in non-destructive evaluation of grouting condition. Impact-echo scanning was used in this thesis for interior and exterior experimental research on grouting situation in prestressed pipe and main-frequency response rules of box beam were studied. Thus, grouting saturation can be the estimated. By using 3D imaging technology of this instrument, the influence of material quality of bellows, grouting duration and thickness of box beams on imaging quality were discussed.5. Ground-penetrating radar method (GPR) offers advantages of intergrity analysis about overall-regional, which can determine the pipeline position and direction and judge the likely location of the existent flaws. Wireless high frequency antenna and high resolution are used to test the quality of grouting condition. This thesis offers a tentative solution to pipeline position and evaluation of grouting condition with the research of judgement basis by means of GPR.