The effect of selected solvents on the viscosity and the oxygen and trace metal content of asphalt

Abstract

Benzene, benzene-ethanol mixture, trichloroethylene, and 1,1,1-trichloroethane were selected to study their effects as solvents on a series of asphalt cements currently used by the Texas Highway Department. For both original and recovered asphalts, the following properties have been measured: viscosity, oxygen content, and selected trace metal contents. Dissolution and recovery resulted in an increase (hardening index greater than unity) in viscosity of all asphalts tested. The effect of solvents on the hardening indices was in the following decreasing order: 1,1,1-trichloroethane (1.65 to 2.45), trichloroethylene (1.80 to 2.20), benzene-ethanol mixture (1.20 to 1.65), and benzene (1.10 to 1.30). For 40 of 49 cases, the recovered asphalts had lower oxygen contents than those of the reference asphalts. However, the oxygen content increased (1) for all seven dried asphalts recovered from dried benzene and (2) for two of the undried asphalts recovered from undried 1,1,1-trichloroethane. Since no water or hydroxyl ions were present for (1), the increase in oxygen content could not have been due to their presence. In every case, the oxygen content in the original and recovered asphalts, as determined by fast neutron activation analysis, was highest for Texaco, intermediate for Humble, and lowest for American Petrofina. ...