Homogeneity Evaluation of High Temperature Exposed Concrete Using Mechanical Waves

The purpose of this study is to evaluate the homogeneity of concrete based on its microstructure by measuring random scattering waves and calculating a heterogeneity index for analysis. Concrete exposed to high temperatures was used as a factor degrading the internal homogeneity of concrete, and experiments were conducted on both standard concrete and various types of fiber-reinforced concrete to verify the applicability of the process used to quantify heterogeneity. The method used to analyze internal homogeneity involves calculating a heterogeneity index based on the peak amplitude differences of the random scattering waves. The experiment was conducted on test specimens consisting of standard concrete and nine mixes with four types of fibers (Carbon, Jute, Glass, Steel) mixed at 0.5% and 1% respectively. The exposure temperatures were set at 200°C, 500°C, and 800°C to analyze the changes in homogeneity due to temperature exposure and fiber reinforcement through experimental research. The results indicate that the changes in homogeneity due to fiber reinforcement, as calculated by the algorithm used in this study, were not sensitive, and no clear relationship between homogeneity and strength was observed. While no clear relationship between homogeneity and strength was observed up to 500°C, a significant relationship was noted at 800°C. This suggests that while the algorithm used in this study has difficulty detecting microstructural changes occurring at exposure temperatures up to 500°C, it can detect changes at 800°C.