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Stripping at the Bitumen–Aggregate Interface: A Laboratory Method To Assess the Loss of Chemical Adhesion

Research paper by J. Vinet-Cantot, V. Gaudefroy, F. Delfosse, E. Chailleux, E. Crews

Indexed on: 29 Mar '19Published on: 26 Feb '19Published in: Energy & Fuels



Abstract

Moisture damage, cracking, and deformation are the three chief distresses caused by traffic and climate during the service life of an asphalt pavement. One manifestation of moisture damage is the loss of bond between bitumen and aggregate, resulting in the displacement of the bitumen in a process called stripping. While numerous tests try to evaluate moisture damage in the laboratory, most of them show poor correlation with field performance. A fuller understanding of stripping is still needed to enable paving technologists to predict and prevent the effects of moisture damage. This study aims to develop a new stripping resistance evaluation technique, wherein adhesion is measured exclusively as a function of the chemical interaction between bitumen and aggregate. A key element of the evaluation technique discussed herein uses a time-lapse image analysis method to characterize the dynamic wetting of precisely applied bitumen droplets on the surfaces of polished mineral aggregates during immersion in a thermo-regulated water bath. At fixed water immersion temperatures, the applied bitumen droplets contract and the image analysis technique allows for measurement of the change with time in the surface area of the contracting bitumen droplet. Different bitumen–aggregate pairs were used in this study. This technique allows for the bitumen–aggregate pairs to be ranked according to their resistance to moisture damage. This technique also allows for the calculation of stripping kinetics and the loss of the bitumen–aggregate adhesive bond of nine samples in exactly the same conditions. Repeatability of the new method is reported. Lastly, the results of the dynamic stripping analyses are compared to the results from the boiling water test on the loose mixture to compare ranking of performances according to the mineralogy.