Total binder recovery methods

The total binder recovery is carried out by using the rotary evaporator or the fractionating column method. Both methods are used mainly for the recovery of soluble binder from bituminous pavement materials in a form for further testing (penetration, softening point, viscosity, etc.). 

In both procedures, the bitumen is separated from the sample by dissolving in dichlo-romethane (or other suitable solvent). The separation is carried out by centrifuging or filtration. After removal of undissolved solids from the bitumen solution, the bitumen is recovered in the first case by vacuum distillation using a rotary evaporator. The temperature at which the distillation procedure is carried out is determined by the type of solvent used (for dichloromethane, the temperature during the first phase of distillation is 45 C and that during the second phase is 150°C the maximum temperature is 175 C). 

In the second case, the bitumen is concentrated by atmospheric distillation in a fractionating column. The last traces of solvent are removed from the concentrate by distillation at 100°C above the expected softening point or 175 C, whichever is higher, with the pressure reduced from atmospheric pressure, 100 to 20 kPa, and with the aid of a stream of carbon dioxide gas (when cut-backs contain white spirit or other high volatile fluxes, the use of carbon dioxide is omitted). 

In both bitumen recovery methods, the temperatures required for the distillation procedure are obtained with the use of heated oil bath. 

The introduction of the bitumen solution into the distillation flask is carried out at a slow rate to avoid the creation of a high volume of steam or excessive bubbling. 

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When the recovery method is used, the total binder is first recovered from the binder solution collected from the continuous-flow extractor or pressure filter apparatus, by using either the rotary evaporation method, according to CEN EN 12697-3 (2013), or the fractionating column method, according to CEN EN 12697-4 (2005) (see Section 9.6.2). 

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