AbstractWhile 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 (Vs) to solid structure development. This study proposes an SH-wave-based method to identify the abrupt increase in the Vs 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 Vs 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 (R2) of 0.9875. The results demonstrated the high sensitivity of Vs to the setting time and the potential applications of SH waves for monitoring the setting time of concrete mixtures.

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