Real-time monitoring of humidity inside concrete structures utilizing embedded smart aggregates

Abstract

The moisture level of hydraulic concrete structures strongly influences their strength and durability, so the real-time monitoring of the concrete humidity is crucial to ensure the regular operation of such structures. To this end, this study used an active monitoring method to observe the concrete humidity in real time by embedding pairs of piezoelectric smart aggregates (SAs) in concrete. The monitoring platform based on smart aggregates was constructed and measured five concrete specimens of two dimensions. The time-domain signals of the concrete specimens at different water content levels were obtained, and the wavelet packet energy analysis characterized the sensor signal energy quantitatively. On this basis, a humidity index was defined to describe the variation in the humidity of the concrete specimens. The experimental results demonstrate that the humidity index is practicable to monitor and evaluate the humidity inside concrete structures. Compared with traditional methods for monitoring the moisture content, the proposed technique does not need manual external excitation and can realize real-time, lossless, and long-time monitoring of concrete humidity.