The study was designed (a) to discover whether steam distillation of asphalt takes place in a drum dryer mixer, (b) to compare changes induced by various laboratory conditioning (aging) techniques versus those occurring in drum dryer mixers, and (c) to identify possible differences in asphalts subjected to drum dryer mixing versus batch (pug mill) mixing. Twenty-seven virgin asphalts were subjected tovarious laboratory conditioning experiments, including thin film oven exposure (tfo), rolling thin film oven exposure (rtfo), (small) steam distillation (ssd), forced air distillation (fad), and rolling forced air distillation (rfad). Various physical and chemical properties of these conditioned samples were measured. These properties were compared with those of the residues recovered from drum dryer operations for each asphalt. By comparing the laboratory conditioned residues to the recovered residues from the drum dryer operation, similarities between the variously exposed asphalts and asphalt recovered from drum dryer mixers were ascertained. This demonstrated that steam distillation does not take place in drum dyrer mixers. Eight matched asphalt pairs, one used in a drum dryer mix and one in a batch (pug mill) mix, were identified among 24 virgin asphalts from georgia by statistically comparing various physical, thermal, compositional, and molecular size properties of the virgin asphalts. Asphalts were then recovered from the mixes in which each of the eight drum dryer-batch (pug mill) asphalt pairs were used. The recovered asphalts were analyzed, and the results show the asphalt residues extracted from drum dryer operations to be slightly harder than those extractedfrom batch operations. This paper appears in transportation research record no. 1228, Asphalt mixtures and asphalt chemistry.
Abstract