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Cutback

Cutback Bitumen (Liquid Bitumen) is produced by blending penetration grade with a hydrocarbon solvent, typical solvents include Naphtha, gasoline and kerosene, white spirit etc.  When the solvent has evaporated, the binder returns to its original penetration grade to tie the particles together. The type of solvent controls the curing time while the amount determines the viscosity of the Cutback Bitumen. The advantages of Cutbacks compared to Emulsions is much higher residual Bitumen percent, typically over 80% compares with over 40-65% for Bitumen emulsions. The result is more Bitumen left on the roadway after curing, for the same volume of binder applied . Cutbacks are divided into three classifications, Rapid-Curing (RC), Medium-Curing (MC) and Rapid-Curing (RC) depending on the solvent used. They are further defined by a number which indicates the minimum kinematic viscosity (fluidity) of the cutback. Two common test methods are ASTM and AASHTO which are used to specify cutback bitumen. A rapid-curing (RC) solvent will evaporate faster than a medium-curing (MC) solvent. Curing relates to the evaporation rate of the solvent which influences the setting time of the bitumen. The viscosity of the cutback bitumen is determined by the proportion of solvent added: the higher the proportion of solvent, the lower the viscosity of the cutback. Cutbacks differ from penetration grade bitumen in that they are more workable, in other words, they can be more easily reshaped. Less heat is required to liquefy cutback bitumen than penetration bitumen, making it easier to use at lower temperatures . Emulsion bitumen is more environmentally   friendly than cut back. Cutback asphalts contain volatile chemicals that evaporate into the atmosphere. Emulsified asphalts evaporate water into the atmosphere.

 

Rapid curing (RC)

Asphalt +Naphtha

Medium Curing (MC)

Asphalt+ kerosene

Slow Curing (SC)

Asphalt +oil

RC-70

MC-30

SC-70

RC-250

MC-70

SC-250

RC-800

MC-250

SC-800

RC-3000

MC-800

SC-3000


MC-3000


 

 

Applications of cut back bitumen 


Cutback bitumen’s suitable for primer sealing can also be used in the manufacture of pre-mix asphalt, which is used in patch repairs. Cutback bitumen’s are used extensively in sprayed sealing applications. Typically, a single application of the appropriate cutback bitumen is sprayed onto the primed pavement onto which aggregate is laid . Rapid curing are used for surface treatment. While, medium curing are used as prime coat