Uncertainty-based on-site carbonation depth estimation of underground concrete structures using portable Raman spectrometer

This study presents and validates a novel methodology integrating a portable Raman spectrometer with the Weighted Average with Probability Density Function and Entropy (WAPE) method for the in-situ estimation of carbonation depth in concrete structures. The methodology establishes a robust correlation between Raman peak intensities and carbonation depths, leveraging probabilistic models and entropy calculations to address the inherent variability and uncertainty associated with field measurements. Empirical results indicate a strong positive correlation between Raman peak intensity and carbonation depth, with entropy values revealing increased uncertainty at greater depths. The efficacy of the proposed method was verified through accelerated carbonation testing and field evaluations, demonstrating an accuracy of approximately 95 % in estimating carbonation depths relative to actual measurements. Sensitivity analyses further illustrated that adjustments to the weighting parameter λ can refine estimations to better suit specific site conditions. The application of the portable Raman spectrometer in conjunction with the WAPE method was successfully validated in underground concrete structures, achieving measurement accuracies of around 95 %. These findings suggest that the integration of portable Raman spectroscopy with advanced statistical techniques provides a powerful non-destructive tool for assessing carbonation in concrete, offering significant potential for enhancing the maintenance and durability of aging infrastructure.