This investigation examined the competitive adsorption behavior of asphalt functionalities for silica and the adsorption behavior ofac-20 and asphalts oxidized to different degrees on real and actualaggregates. The competitive affinity for dry silica of paired combinations of seven model functionalities known to be present in asphalt was determined. The affinity shown by the components in a competitive situation was different from that of the individual components. Competitive adsorption was also performed on moistened silica. The nitrogen base, quinoline, was most sensitive to moisture, whereas thesulfoxide was the least sensitive. In addition, asphalt oxidized todifferent degrees was adsorbed onto silica, alumina, sandstone, andlimestone. On moist and dry silica and alumina, ac-20 was adsorbed more than the oxidized asphalts. On limestone and sandstone, the adsorption of ac-20, oxidized asphalt, and their respective asphaltene fractions was concentration dependent. Most of the adsorption behavior fitted the langmuir model better than the freundlich model. Monolayer amounts obtained from the langmuir isotherms decreased with increased oxidation levels. The nature of the adsorbed asphaltic carbonwas examined by controlled atmosphere electron microscopy. This paper appears in transportation research record no. 1228, Asphalt mixtures and asphalt chemistry.
Abstract