Detecting Grouting Quality Of Tendon Ducts Using The Impact-Echo Method

The bonded post-tensioned prestressed concrete structure was widely used inbridge construction due to its advantages of great spanning capacity and high ultimatebearing capacity.However, in practical engineering, voids in the grout develop alongthe tendon due to improper grouting prodedures,blockages,grout material problems,which result in corrosion of the steel tendons and affect the safety and durability ofstructure.Therefore, the detection of grouting quality in tendon ducts in concretestructures is one of the key important issues in civil engineering.The impact-echomethod is a nondestructive testing method based on low frequency transient stresswave.In this paper,the method is employed to detect the grouting quality of tendonducts The study is summarized as follow:1.The research review on the impact-echo method are introduced firstly, and thebasic principle of the impact echo method and its application in nondestructive testare given a brief introduction associated with the basic wave theory.2.The numerical simulation analyses on the impact-echo response of severaltypical tendon ducts grouting conditions using the dynamic finite element analysissoftware ANSYS/LS-DYNA were conducted to provide a theoretical basis for thesubsequent study.3.Numerous simulation analyses were presented to investigate the influence oftendon duct size and embedded depth, degree of duct grouting and defect orientation,tendon ducts material and deck thickness on impact-echo testing results.It concludesthat:(1)The tendon ducts size is the key factor to affect the impact-echo response andthe defect can be detected when the ratio of diameter to thickness is greater than0.2.(2)The protection layer thickness of the duct can’t be detected if ducts were embeddedtoo shallow or too deep.(3)The orientation of the reflecting surface has significantinfluence on the effectiveness of the impact-echo method.(4)The effect of the ductthickness on the detection of protection layer thickness can be ignored.4.The advanced portable impact-echo system (PIES) was employed to conduct anexperimental test on typical grouting defects of several tendon ducts. Theexperimental results agree well with the FEM results5.A comprehensive summary of theoretical and experimental study of theimpact-echo method was conducted, and a preliminary discussion was made for the future study.