A modified adhesion evaluation method between asphalt and aggregate based on a pull off test and image processing

Abstract The adhesion between asphalts and aggregates is an important parameter affecting moisture damage in asphalt mixtures, and a pull-off test is usually used to evaluate the adhesion performance between asphalts and aggregates due to the ease of operation. To analyze the influence of aggregate lithology on asphalt adhesion performance, two types of asphalts and four types of aggregates were tested via pull-off tests. The pull-off force data showed that the variance in the results gradually decreased as the test temperature increased. Then, an image processing software package, cover-area, was developed based on MATLAB to calculate the asphalt coverage area of the pull-stub, and the accuracy of its calculation results was verified. Finally, the modified pull-off strength was obtained by dividing the pull-off force by the asphalt coverage area to analyze the influence of aggregate lithology on asphalt adhesion. The results show that the modified pull-off strength of basalt and diabase is the highest, followed by that of limestone, and that of tuff is the worst, which is consistent with the actual application situation. The proposed method could be used to evaluate the adhesion performance between asphalt and aggregates well.