Change in consistency and composition of trichloroethylene- and trichloroethane-treated asphalts

Solvent extraction of asphalt from pavement mixtures is a technique used to study the change in asphalt during service. Rheological measurements indicate that asphalts recovered from trichloroethylene or trichloroethane are markedly hardened. Compositional studies on asphaltic fractions reveal a notable decrease in saturates, naphthenes, H, N, Ni and V, and increase in polar aromatics and asphaltenes along with incorporation of Cl in all fractions. These structural changes are responsible for the hardening of the asphalt and are interpreted in terms of cyclization of saturates, aromatization of naphthenes, coupling of free radicals with neutral species to give a high content of asphaltenes, and in terms of loss of the relatively volatile Ni and V porphyrins during the extraction—recovery process.