Monitoring hardening of concrete using ultrasonic guided waves

Abstract

Evaluation of early age properties of concrete is critical for ensuring construction quality of concrete structures. Although ultrasonic wave based methods show potential for monitoring the hardening process of concrete in laboratory, there are many challenges related to sensor installation and data acquisition in practice. In this study, the authors present an ultrasonic guided wave method that uses guided waves in a steel rebar to monitor hardening of surrounding cement paste and mortar. The longitudinal L(0,1) mode guided wave in rebar is excited by an EMAT sensor and received by a piezoceramic P-wave ultrasonic transducer. Continuous measurements during cement hydration were used to monitor the longitudinal wave attenuation resulted from leakage from the rebar to the surrounding cement paste/mortar. Shear wave velocities in cement materials were also monitored at the same time. Experiments were performed on four cement paste samples and three mortar samples. Experimental results demonstrated a strong correlation between the guided wave leakage attenuation and shear wave velocity for all tested samples, and both parameters increase with the age of cement materials.