Comparison of Rheological Properties for Recovered Residue from Emulsified Asphalt obtained by Three Recovery Procedures

Subject area: Quality/Test Procedures Several recovery procedures for asphalt emulsion residue have been used over the years, but there is no one procedure that has been universally accepted. In this study three recovery methods are used to obtain the residue of the emulsified asphalt: 1) distillation (ASTM D 6997), 2) evaporation (ASTM D 6934) and, 3) the newly approved moisture analyzer balance procedure described in ASTM D 7404. Five types of emulsified asphalt used for different applications for various pavement treatments were investigated: 1) a cationic slow-set tack coat, diluted CSS-1h; 2) a cationic rapid set used for chip seals, CRS-2; 3) a solvent containing cationic medium-set CMS-2h; 4) ananionic high float medium-set, HFMS-2; and 5) a rapid-set polymer modified used for chip seals, CRS-2P. The residue obtained from each emulsified asphalt was characterized by a Dynamic Shear Rheometer (DSR) by performing frequency sweep and a temperature sweep on each recovered residue. The preliminary rheological characterization of the binders performed at 60C and 25C show that the Complex Modulus, G* can be used to rank the recovery procedure for each emulsion type. Increasing G* was observed for all emulsion types: G*(D-7404) > G*(D-6934) > G*(D-6997) except for CRS-2P where the G* was comparable for all three recovery procedures. These preliminary rheological results suggest that aging of the binder during recovery for the three methods is ranked as moisture analyzer balance (D 7404) > Evaporation (D-6934) > Distillation (D 6997). Master curves were generated for each emulsion residue using the temperature and frequency sweep. Furthermore the extrapolated crossover frequencies deduced from the master curves for the residues obtained by the different recovery methods are shown to be a way to assess the ‘cured’ state of the residue and to differentiate the procedures.