Research on setting process of dam concrete based on ultrasonic combined method CUI Bo, WANG Zijun, LIU Changxin, REN Bingyu (State Key Laboratory of Hydraulic Engineering Simulation and Safety, Tianjin University, Tianjin 300350, China) Abstract: The determination of the condensation state of fresh concrete is crucial to the quality control of dam concrete construction. The traditional method for measuring the setting time of concrete is the penetration resistance method, which is detrimental to monitoring and is difficult to achieve continuous and real-time monitoring of the concrete setting process. The emerging ultrasonic nondestructive monitoring mainly adopts a single transmission method or reflection method. However, the reflection method is greatly affected by the incident angle, and the calculation of the wave velocity of the transmission method needs to manually determine the first wave occurrence time accurately. In view of the above problems, this paper puts forw