Detection of Sleeve Grouting Defects Based on Cascaded Two-port Networks Method

The prefabricated building has become increasingly popular and widely promoted, and a grouted splice sleeve is used for joining reinforcing bars embedded in precast assembled concrete components. The internal grouting defects in the sleeve seriously affect the safety and durability of the precast concrete structures. Therefore, it is vital to detect and evaluate the grouting quality. Effective detecting techniques are still lacking. So far, very little attention has been paid to the role of electromagnetic wave detection methods in sleeve grouting defects detection. This paper proposed a method based on cascaded two-ports networks theory. Firstly, we viewed the combination of sleeve, rebar and grouting as a four-port waveguide model which can be simplified to a two-port network under certain conditions. Different defects correspond to different cascading multiple sections of waveguides. Under the guidance of this idea, the formulas of scattering parameters of cascaded two-port waveguides are deduced. The formulas proved that it is feasible to detect and evaluate typical grouting defects by viewing the periodic pattern of S parameters. The Excitation Method based on extended SMA was proposed to use the pattern obtained above. Results of simulation models verified the feasibility of our proposed method. Some further research on this method is needed for its practical application at the industrial building site.