New insights into strain evolution of concrete under different freeze-thaw conditions: Investigation based on real-time and full-field monitoring

Understanding the strain development behavior of concrete during the freeze-thaw process is important to assess the remaining service life of structures in cold regions. In this study, a real-time, in-situ, and full-field strain monitoring method based on Fiber Bragg grating sensors was designed to measure the strain inside the concrete under different freeze-thaw processes. A temperature compensation method was employed to ensure the precision and reliability of the experimental procedure. Results indicated that the strain inside the specimen was consistent in the same cross-section and showed a declining trend from the surface to the middle cross-section. The mechanisms of these phenomena were discussed based on the thermodynamics and mechanics perspective. Furthermore, a layered mathematical model of the maximum compressive strain development was established. A novel method for assessing strain development during the freeze-thaw process was proposed based on the energy perspective to reveal the evolutionary characteristics of energy dissipation.