ASSESSMENT OF ADHESION BETWEEN MINERAL AGGREGATE AND BITUMINOUS BINDER USING DIGITAL IMAGE ANALYSIS

This work presents how to assess a rate of adhesion between bituminous binder and mineral aggregate. Asphalt mixtures composed from grade bitumen 50/70, reference or modified with adhesion promoters based on amines, and aggregate (Brant, Zbraslav, Skuteč – 8-16mm) were made and then photographed. Three adhesion assessment approaches were applied: (i) standardized adhesion visual assessment, (ii) gray level thresholding, and (iii) entropy-based image segmentation, both evaluated from digital images. It was shown that adhesion between both Brant and Skuteč and reference binder, expressed as a rate of binder-coated area onto aggregate particles, was equal to ca. 50-70 %, while mixture composed from Zbraslav exhibited ca. 70-80 %. If adhesion promoters were used, these areas increased in all three cases up to 80-90 %. It was shown that results obtained using visual and entropy segmentation analysis were very similar, while these differed in comparison with gray-level thresholding.