Distributed Humidity Sensing in Concrete Based on Polymer Optical Fiber

Area of Science:

• Materials Science
• Civil Engineering
• Optical Engineering

Background:

• Accurate monitoring of concrete moisture content is crucial for structural integrity and durability.
• Traditional humidity sensors can be limited in distributed sensing capabilities within concrete structures.
• Polymer optical fibers (POF) offer potential for embedded sensing due to their unique optical properties.

Purpose of the Study:

• To investigate the feasibility of using embedded polymer optical fibers (POF) for distributed humidity monitoring during concrete drying.
• To analyze the changes in optical properties of POF due to water dissipation.
• To correlate optical signal variations with concrete moisture content.

Main Methods:

• Embedding POF within a concrete sample for in-situ monitoring.
• Utilizing optical time domain reflectometry (OTDR) to measure Rayleigh backscattered light.
• Acquiring optical signals at two wavelengths (650 nm and 500 nm).
• Comparing POF sensor data with electrical humidity sensors.

Main Results:

• The received optical signal at 650 nm increased as the concrete dried.
• The fiber attenuation factor at 500 nm increased with decreasing moisture content.
• Optical signal changes in the hygroscopic range showed good agreement with electrical humidity sensor measurements.

Conclusions:

• Embedded POF can serve as a distributed humidity sensor for monitoring concrete drying processes.
• Changes in optical properties of POF are sensitive to moisture variations.
• The OTDR technique combined with POF offers a promising method for structural health monitoring in concrete.