Cutback Bitumen

Cutback asphalt is simply a combination of asphalt cement and petroleum solvent. Like emulsions, cutbacks are used because they reduce asphalt viscosity for lower temperature uses (tack coats, fog seals, slurry seals, stabilization material). Cutback bitumen is used for cold weather bituminous road construction and maintenance

Cutback bitumen in normal environment temperature is liquid, or is changed to liquid with a little heat. Similar to emulsified asphalts, after cutback asphalt is applied, the petroleum solvent evaporates leaving behind asphalt cement residue on the surface to which it was applied and the bitumen will bind the aggregate. Cutback asphalt is said to “cure” as the petroleum solvent evaporates away.

The speed of its clotting or hardening depends on the kind of liquid. For example because of high speed of gasoline evaporation, bitumen solved in gasoline hardens faster. The distillates used for preparation of cutback bitumen are naphtha, kerosene, diesel oil, and furnace oil.

Depending on the kind of solvent, there are different types of cutback bitumen, like rapid curing (RC), medium curing (MC), and slow curing (SC). RC is recommended for surface dressing and patchwork. MC is recommended for premix with less quantity of fine aggregates. SC is used for premix with appreciable quantity of fine aggregates.

The use of cutback asphalts is decreasing because of firstly environmental regulations. Cutback asphalts contain volatile chemicals that evaporate into the atmosphere. Emulsified asphalts evaporate water into the atmosphere. The second reason is due to high amount of energy and money required. The petroleum solvents used require higher amounts of energy to manufacture and are expensive compared to the water and emulsifying agents used in emulsified asphalts. In many places, cutback asphalt use is restricted to patching materials for use in cold weather.

Sources: cdeep.iitb.ac.in, pavementinteractive.org, petrotarco.com

P.S: Gildatar Bitumen is proud to make possible the supply of Middle East bitumen in multiple grades 60/70, 80/100, 85/100, 85/25, 40/50, and 30/40.