Real-Time Monitoring of Early-Age Concrete Strength Using Piezoceramic-Based Smart Aggregates

It is well known that concrete is the most common type of structural material, and a proper estimation of concrete strength in its early age can provide guidance for staged concrete construction and ensure the load-bearing capacity of concrete structures during construction and service periods. In this study, an active sensing approach integrated with piezoceramic-based transducers called smart aggregates (SAs) was experimentally investigated to estimate the strength development of the entire early-age (0th h to 28th day) concrete in real time. A pair of SAs was embedded in a reinforced concrete specimen prior to casting. During the 28 days of the curing period, one SA was employed as an actuator to periodically generate a designed stress wave that propagated along the specimen; meanwhile, the other SA was applied as a sensor to detect stress waves. The wave responses of the SA sensor were recorded and analyzed during the 28-day testing period. The experimental results demonstrate that the magnitude of the detected stress wave in the concrete increased with the strength of the concrete in the 28-day curing period. In addition, a hydration monitoring index was established and compared to the previous results of the 28-day concrete strength curve obtained by standard compressive tests. The proposed hydration monitoring index and the 28-day concrete strength curve show similar trends, which indicates that the proposed method has the potential to estimate early-age concrete strength in real time.