Ultrasound-excited thermography for detecting microcracks in concrete materials

摘要

This study investigated the use of ultrasound-excited thermography to detect microcracks in concrete materials. Pre-cracked concrete specimens full of standardised microcracks were fabricated to quantify the detectability of cracks. These cracks were independently assessed in terms of width by identifying the separation between two crack faces and measuring their surface widths. Thereafter, excitation experiments were performed. Three sets of specimens were excited with ultrasound frequencies of 20 and 40 kHz. The temperature fields of specimens were observed with a thermal imager and specified through a quantitative analysis with regard to crack width and temperature rise. Detectable widths of cracks excited with a remarkable temperature rise were further analysed based on width statistics of the surface cracks. The analysis showed that ultrasound-excited thermography effectively detected concrete cracks having widths of 0.01-0.09 mm.