Study on the Method to Quantify the Color Changes of Reinforced Concrete Member subjected to High Temperatures

고온을 받은 철근콘크리트 부재의 색 변화도 정량화 방법에 관한 연구

Although concrete structures suffer from damage due to high temperatures such as fire, it is possible to repair and strengthen after fire considering economic interests. To assess the remaining bearing capacity of the structural elements after high temperatures, information of the temperatures reached inside the elements is very important. The assessment of the temperatures reached inside concrete during a fire by means of its color changes has been studied using the method of spectrophotometer or digital image analysis. The purpose of this study is to quantify changes in color for reinforced concrete member including columns and beams using digital image analysis and to identify the relationship between color changes and increasing temperatures. In this paper new approach is performed to the research field of assessment of concrete structures after fire by means of colorimetry. The color measurement of digital images in reinforced concrete columns and beams exposed to $300^{\circ}C$, $500^{\circ}C$, and $700^{\circ}C$ is executed according to RGB, HSB, and Lab color space with Photoshop Software and the trend of each color value is analyzed in different temperatures. The result of this study shows that color changes of reinforced concrete member with increasing high temperatures not only a shift to red is considered, but also the development of a color path. Therefore, this color development can be related to the increasing temperature and can be used to assess the fire damage of concrete structures.