ADSORPTION OF MODEL ASPHALT FUNCTIONALITIES, AC-20, AND OXIDIZED ASPHALTS ON AGGREGATE SURFACES

Abstract

This investigation examined the competitive adsorption behavior of asphalt functionalities for silica and the adsorption behavior of AC-20 and asphalts oxidized to different degrees on real and actual aggregates. 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 the sulfoxide was the least sensitive. In addition, asphalt oxidized to different degrees was adsorbed onto silica, alumina, sandstone, and limestone. 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 carbon was examined by controlled atmosphere electron microscopy.