Development of high accurate impact echo method and its application to filling evaluation of PC grout

One of the problems with the standard impact echo method is the loss of the repeatability of the elastic wave waves. The peak of the target in the frequency domain is sometimes not clear. We have devel- oped a more accurate impact echo method using multiple impacts and averaging their time domain signals. We applied this improved method of evaluating grout filling in tendon ducts. The time domain signals were superposed so that the reflected waves strengthened each other. We were successful distinguishing the pres- ence of grout filling in tendon ducts with the diameter of 38 mm and the center depth 275 mm was possible. 1 INSTRUCTION 2 EXPERIMENTAL METHOD The problem of ungrouted tendon ducts in PC struc- 2.1 Specimen tures should be solved as soon as possible because Figure 1 shows the dimensions of the specimen for the ungrouted tendon ducts may cause corrosion or the impact echo tests. The mixture proportion of the severance of the PC steel bars/wires. The X-radar 3 method, the radar method, the supersonic method concrete is cement of 296 kg/m , water of 167 3 3 and the impact echo method (Sansalone & Streett kg/m , fine aggregate of 903 kg/m , and coarse ag- 3 1997) have been applied to evaluate grout filling in gregate of 1041 kg/m . The ratio of water to cement tendon ducts (Uchida et. al. 2005, Kawashima et al. is 56.6 %. The maximum coarse grain size is less 2005). However the performances of those methods than 20 mm. The embedded tendon ducts are made are not accurate enough for the evaluation of grout from steel and are 38 mm in diameter. The un- filling in tendon ducts. grouted tendon duct is empty and the grouted tendon In this paper we discuss the improvement of the duct has a steel bar with a diameter of 32 mm at the impact echo method. One problem of the impact center of the duct. echo method is the loss of the repeatability of the elastic waves passing through concrete bodies.