The influence of different minerals on the mechanical resistance of asphalt mixtures

The adsorption of five asphalts processed in Brazilian refineries and designated as A, B, C, D and E, and their asphaltenes and maltenes constituents, from toluene solutions, onto quartz, feldspar and biotite and the relationship between this tendency and the mechanical properties of the asphalt pavement have been investigated. For all minerals asphalts A and C strongly absorbed the others. Their respective curves levelling off between 3.5 and 4.0 mg g− 1 for gneiss and quartz, increasing to 5 and 6 mg g− 1 for feldspar and biotite. The eletrophoretic mobility of quartz was not modified by the adsorption of asphaltenes in contrast to that observed for feldspar and biotite, indicating that the sites liable for the surface charge of the latter minerals were affected by the presence of the adsorbed organic species. Regarding the mechanical resistance tests for asphalt mixtures, only asphalts A and C gave that would be considered values acceptable by the Brazilian National Department of Terrestrial Infra-structure (DNIT) (> 80%). Those results indicate that the chemical interaction among minerals and asphalts should affect for good or bad the mechanical resistance of the asphalt mixture.