Contactless ultrasonic test system for set times of mortar and concrete

The concrete final set time (tf) is influenced by the concrete mixture and ambient conditions. Rapid measurement in the laboratory or field is difficult because of wet sieving or access and device coupling limitations. A non-contact, one-sided ultrasonic testing system (UTS) has been developed to monitor leaky Rayleigh wave (LR-wave) signals emitting from the specimen surface with an array of non-contract microelectromechanical systems (MEMS) receivers. A new ultrasonic set time (tUS) parameter was defined based on the initiation time of the LR-wave energy curve. The UTS technique implemented in the laboratory determined the tUS of multiple mortar mixtures to be between 270 and 1335 minutes. The tUS for the mortars were consistent with tf by ASTM C403 penetra tion resistance when the transmitter s incident angle was set at 12 degrees. Different incident angles (12 to 60 degrees) influence the signal quality and tUS. The non-contact UTS was deployed on three concrete pavement sections and produced tf of 210, 266, and 289 minutes.