Rationale

The proposed revisions to ASTM D5404 aim to optimize the solvent recovery process for asphalt binder residues using the rotary evaporator. The current methods often leave substantial amounts of solvent in the binder residue, leading some users to use the RTFO to remove remaining solvent, which causes oxidation and stiffening of the binder. The revisions include using absolute pressure instead of relative pressure, eliminating the need for carbon dioxide or nitrogen gas, increasing flask rotation speeds up to 150 rpm, and implementing two stages of distillation for the bulk removal of solvent and secondary distillation to remove trace amounts of solvent, which includes two distillation bath temperatures. Additionally, a lower vacuum pressure for rapid evaporation and longer purge times of 90-120 minutes are proposed to ensure complete solvent removal. The proposed ballot also includes addition of solvents not currently used by this practice. The added solvents are listed in Table 1, but with the revision of the standard it provides flexibility to adding additional solvents. There are rotary evaporator units equipped with automated modes that adjust to the vapor temperature and pressure in the condenser during the recovery. The unit automatically adjusts to gently and gradually remove the solvent from solution. This proposed ballot addresses the procedure used for these automated units.