TY - JOUR A1 - Schickert, M. A1 - Krause, Martin A1 - Müller, W. T1 - Ultrasonic Imaging of Concrete Elements Using Reconstruction by Synthetic Aperture Focusing Technique JF - Journal of materials in civil engineering N2 - Ultrasonic reconstruction by the synthetic aperture focusing technique (SAFT) has a great potential to image concrete elements and detect embedded objects. Its algorithm focuses ultrasonic signals received at many aperture points by coherent superposition, yielding a high-resolution image of the region of interest. Using this approach, several problems caused by the strongly inhomogeneous structure of concrete are diminished, where scattering of transmitted pulses leads to disturbing phenomena such as attenuation and structural noise. This contribution is intended to review the work of the writers on the application of SAFT reconstruction to concrete testing. First, consequences of scattering of ultrasonic waves in concrete are qualitatively explained. Then the use of SAFT is discussed in comparison to traditional A-scan and B-scan techniques. Different reconstruction algorithms and implementations are presented for one-, two-, and three-dimensional SAFT. Pulse-echo measurement systems are described, which are able to acquire large sets of data on linear and planar apertures employing single transducer, transducer array, and scanning laser Doppler vibrometer arrangements. To illustrate the application of the SAFT techniques, examples from laboratory and field experiments are described comprising imaging of back walls, tendon ducts containing faults, layers, and reinforcement in concrete elements. KW - Imaging techniques KW - Concrete KW - Acoustic detection PY - 2003 DO - https://doi.org/10.1061/(ASCE)0899-1561(2003)15:3(235) SN - 0899-1561 SN - 1943-5533 IS - May/June SP - 235 EP - 246 PB - American Society of Civil Engineers CY - New York, NY AN - OPUS4-2752 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -