Measuring moisture damage of asphalt mixtures: The development of a new modified boiling test based on color image processing

A new digital image processing method based on color images was developed to analyze the coating quality of asphalt mixtures with moisture damage. The asphalt coating ratio can be measured automatically and objectively, improving the accuracy of boiling test (ASTM D3625). This method is based on RGB color model and the characteristic color pixels representing virgin aggregate are directly utilized to search the damaged areas. The developed color image processing was compared to the two existing digital imaging methods. The selection of threshold value was a subjective process in the binary image processing. The problem of the grayscale-based image processing was the lack of a reasonable method to obtain the representative image of virgin aggregate. Also, the light reflection on asphalt and the shadow between aggregates might lead to grave errors. In contrast, the proposed method could avoid those issues and realize the objective inspection of stripping in asphalt mixtures.