Interpretation of stripping at the bitumen–aggregate interface based on fluorescence tracing method

Abstract

Asphalt pavement field performance largely depends on the stripping resistance at the bitumen–aggregate interface. However, the conventional stripping resistance evaluation method is unsuitable for direct and precise quantification of the retained bitumen film area on the aggregate surface that designates the stripping resistance between bitumen and aggregate phases under the action of vehicle wheels or moisture damage. This study proposed a novel fluorescence tracing method to quantify the exact area of aggregate coating loss in accordance with the bituminous-coated aggregate image processing technique. The fluorescence tracing image acquisition and analysis system for precisely calculating the bitumen stripping ratio of the bituminous-coated aggregate were established after the bitumen stripping test. The thresholding manner of the two-mode threshold algorithm was devised to segment the fluorescence-traced bituminous-coated aggregate image with high quality. The results demonstrated that the appropriate threshold value for segmenting the fluorescence-traced image mainly falls in the range of 60–70 for limestone, 90–110 for basalt, and 100–110 for both granites; the ability of aggregates based on their chemisorption capacity with bitumen is in the order of limestone, basalt, and granite; the fluorescence tracing method eliminated nearly 92.3% of the undesirable reflection on bitumen phase; the detected bitumen stripping ratio, raised by 65.87% on average and by 37.82% in the median value in contrast to the conventional visual detection manner. This research introduces a practical framework from an engineering perspective for visually quantifying the interpretation of the adhesive bond at the bitumen-aggregate interface with reasonable accuracy and confidence.