Setting Time Measurement of Concrete Mixtures through Monitoring of Shear-Wave Velocity with Shear-Horizontal Waves

While the monitoring of longitudinal (P) waves has been widely investigated to estimate the initial setting time of concrete mixtures based on the variation in P-wave velocities, it is difficult to accurately estimate the setting time owing to the sensitivity of P-waves to air voids and the difficulties in identifying the final setting time from smooth velocity variations. Furthermore, shear-horizontal (SH) waves are advantageous over P waves for monitoring the setting time owing to their high signal-to-noise ratio and sensitivity of the shear-wave velocity (V-s) to solid structure development. This study proposes an SH-wave-based method to identify the abrupt increase in the V-s values at the initial and final setting times. The proposed method was verified against traditional penetration resistance tests and P-wave tests with two sets of concrete specimens having different water-to-cement ratios. Although the initial setting times from the P-wave and SH-wave tests are close with the differences of 9% and 21% for the two sets of specimens, however, the smooth velocity variations from the P-wave tests cannot identify the final setting time that can be clearly captured with the abrupt increase of V-s from the SH-wave tests. Both setting times from the SH-wave tests and the penetration resistance tests have a high correlation with a coefficient of determination (R-2 ) of 0.9875. The results demonstrated the high sensitivity of V-s to the setting time and the potential applications of SH waves for monitoring the setting time of concrete mixtures. (C) 2022 American Society of Civil Engineers.