The ultrasonic technique is very effective for non-destructive measurement of fresh and hardened cementitious composites. In this study, the ultrasonic technique is further developed with embedded piezoelectric transducers for cement paste hydration monitoring. In this method, the transducers were pre-placed in a mold before casting the specimen. After the specimen was cast, the transducers were used to generate and receive ultrasonic waves. Wave velocity and amplitude were measured. From the velocity measurement, the hydration process of cement paste could be interpreted. The interaction between the transducers and the cement paste was analyzed. In addition, the dynamic modulus was calculated using the wave velocity. Since the embedded transducers had good coupling with the cement paste, reliable test results have been obtained. It is feasible to use the technique as an in situ technique to monitor the hydration process at an early age, as well as the health condition after maturing for a concrete structure. © 2008 IOP Publishing Ltd.