Characterization of cement concrete specimens during hydration process with piezoelectric-based smart aggregates

![CDATA[Characterization of cement concrete during hydration process has been performed using different methods. The determination of initial water-to-cement ratio is one of the challenging tasks since hydration process determines the microstructure of cement concrete and non-destructive methods with high accuracy are desired. This paper presents the results of the investigation into the stress wave transmission in cement concrete specimens with different initial water amount during hydration process. A non-destructive evaluation approach using embedded Smart Aggregates (SAs) at frequency range of 150 Hz to 150 kHz is used for this purpose. In this approach, one SA acts as an actuator when the swept sinusoidal wave is excited. The stress wave transmits through the specimen and it partially is received by the SA sensor. The time-domain receiving signals are recorded during hydration process and the corresponding power spectrum densities as transmission energy are computed and analysed, and then used for the material characterization. In addition, a destructive compression test is carried out on the 7th day and 28th day. The results show that changes of water amount in the standard-based specimens reduce their stress wave transmission performance and compressive strength value at 28th day. The feasibility of the SAs technique for the determination of water-to-cement ratio of cement concrete is also demonstrated.]]