Measuring Alkali-Silica Reaction Expansion in Concrete with Optical Fiber Sensors

Several degradation mechanisms can affect concrete, and the alkali-silica reaction (ASR) is considered one of the most worrying. Several techniques and procedures have been developed during the last decades to assess concrete infrastructure affected by ASR. Among them, structural health monitoring techniques are considered the most reliable to understand the expansion rate over time and to predict the potential damage in affected structures. In this context, fiber optic sensors inscribed with Bragg gratings (FBG or Fiber Bragg Grating) have been gaining more attention for applications in structural monitoring. These optical sensors have small dimensions, low signal loss, and high precision for strain measurements. However, the application of FBG in degraded concrete is incipient. Therefore, this work aims to evaluate the efficiency of FBG for strain determination compared to traditional techniques. The expansion measurements taken by the optical sensors on the sample's surface showed statistically equivalent expansions with lower errors than those obtained in traditional studs’ measurements. This result demonstrates the reliability of using optical sensors for long-term monitoring of concrete structures and would allow a better investment in the repair of works, ensuring the integrity of the infrastructure of dams, bridges, viaducts, tunnels, walkways, and large buildings.