ULTRASONIC ECHO-PULSE TOMOGRAPHY OF CONCRETE USING SHEAR WAVES LOW-FREQUENCY PHASED ANTENNA ARRAYS

摘要

The paper gives the description of up-to-date method for concrete testing based on the drypoint contact ultrasonic transducers technology, advanced methods of computer tomography and new techniques of signal processing using SAFT algorithm. The authors explain the operating principles of Low-frequency ultrasonic Tomograph for concrete A1040M MIRA, the main working element of which is 40 DPC shear wave transducers antenna array. The A1040M MIRA tomographer is applicable for concrete testing using the ultrasonic frequency range of 20-150 kHz. The main operation principle of the equipment is pulse-echo tomography based on the coherent accumulation of reflected signals, received by different elements of antenna array, with their further processing. The implemented SAFT algorithm allows building the 3D data massive of structure's reflected parameters in tested area and then reviewing it in different sections and images. The practical trials on different objects confirmed the applicability of the Tomograph A1040M MIRA for the following testing tasks on reinforced concrete, monolith concrete and other concrete objects: Thickness measurements up to 2 m; Testing of structure integrity by presence and level of backwall signal; Searching for location and estimation of sizes of different reflectors inside the objects, localization of cable ducts, reinforcement bars, hollows, delaminations and other discontinuity flaws; Estimation of integrity between hidden sides of concrete or tunnel paneling with the solid grouting behind. The paper also represents the signal processing methods, operation techniques and methodic, allowing successful and efficient testing of objects from concrete with imaging the internal structure of the objects in different areas and depths.