Assessment of Concrete Efflorescence based on Hyper-spectral Imaging

Abstract

Efflorescence is a phenomenon mostly made by carbonation process of concrete structures. It is one of the internal damages seriously considered in evaluating the durability of concrete bridges. In Korea, the guideline for the bridge safety inspection requests to assess crack, efflorescence, spalling and reinforcement exposure in prior for the slabs and girders of concrete bridges. Currently, the assessment is performed based on the visual inspection of expertized engineers, which may result in subjective inspection result. In this study, a novel method to assess concrete efflorescence is proposed based on hyper-spectral imaging (HSI) device. The HSI acquires the light intensity for a number of continuous spectral bands of light for each pixel in an image, which makes the HSI provides more detailed information than a normal color camera that collects intensity for only three bands corresponding to the colors, RGB (red, green, and blue). A stepwise assessment algorithm is developed based on the spectral features developed to decompose efflorescence area from the inspected concrete area. The algorithm is verified in the laboratory testing using concrete specimens with the efflorescence, which shows high accuracy of the proposed HSI-based assessment.