Yacouba Konate¹, Layella Ziyani², Athanas Konin^3,, Anne Dony²

The use of cold-mix asphalt is an effective approach to environmental protection. These materials are intended for low- to medium-traffic roads and have significant potential for secondary road networks in African countries. The objective of this article is to study the influence of surfactant use on the bitumen emulsion-aggregate interaction from a microscopic perspective. Two surfactants (designated A and B) and four types of materials (granite, diorite, limestone, and silica) were studied. The tests performed were: emulsion-aggregate compatibility tests, tests to determine the optimal water content of the mixtures, UV-visible adsorption tests by spectrometry, and tests to assess emulsion bond breakdown upon contact with fine minerals. The results show that the surfactant adsorption differed according to the surfactant-substrate pair considered and adsorption tests performed by UV-visible spectrophotometry revealed that surfactant A adsorbed more readily onto the substrates than surfactant B. This could be due to the charge of the respective hydrophilic heads of the surfactants. Adsorption is stronger with surfactant A because its polar charge is greater than that of surfactant B at pH 2. The emulsion – aggregates rupture was all the more rapid as the SiO₂ content increased in aggregates. At the rheological level, the behavior of the emulsion-filler mixtures was influenced by the surfactant nature and content, the specific surface area of the aggregates and the emulsion-filler mass ratio.

bitumen emulsion, surfactants, adhesion, fine minerals, UV spectrometry adsorption