Early-Age Freeze–Thaw Damage Detection in Concrete Using Two-Dimensional Non-Contact Ultrasonic Sensors

Abstract

In this study, early-age freeze–thaw damage (small-scale damage) was detected on a concrete surface using developed two-dimensional non-contact ultrasonic sensors based on a micro-electromechanical system (MEMS). The wave field of ultrasonic waves passed through damaged concrete surfaces contain propagating and scattered waves, caused by refraction and reflection. To measure the wavefield, multi-channel non-contact ultrasonic sensors was developed including 128 MEMS array. Then, the amplitude of scattered waves was extracted in the frequency-wavenumber domain. The proposed method was experimentally validated through freeze–thaw cycle testing and compared to the conventional dynamic modulus reduction. The results demonstrated that the proposed method was 22.2 times more sensitive than the conventional method toward early-age freeze-thaw damage on concrete surfaces.

Keywords: Early-age freeze-thaw damage, ultrasonics, scattered wave, Concrete, small damage