Suggested Citation:
Roy, Souvik, Angel Mateos, Julio Cesar Paniagua, Somayeh Nassiri (2025)

Improving Sensor Encapsulation for Long-Term Monitoring of Relative Humidity and Temperature Inside Concrete Pavements

Capacitance-type sensors have long been used to measure the relative humidity (RH) in concrete but often fail due to inadequate encapsulation, resulting in intermittent data and a short sensor lifespan. This study aims to enhance sensor reliability by evaluating three encapsulation prototypes in two stages, using solid and porous plastic tubes and caps with varying pore sizes. Namely, the prototypes are as follows: slotted frame with membrane (SFM), porous tube (PT), and polyvinyl chloride tube (PVCT).

In the initial stage, the sensors were exposed to air, and their data was compared to sensors without encapsulation. The PT prototype emerged as the best-performing encapsulation based on real-time data correspondence, RH and temperature data accuracy, sensor survival, and repeatability.

Next, six replicate PT-encapsulated RH sensors were evaluated in a concrete pavement test section constructed with three different concrete mixtures and monitored for 20 months. All PT-encapsulated sensors remained functional over the monitoring period, effectively capturing the differences in concrete RH between the three mixtures and showing diurnal and seasonal variations corresponding to ambient conditions.

The data collection from this study will continue, offering long-term insights into the durability and reliability of these encapsulation techniques for RH sensors in concrete.