Cutback bitumen is a type of liquid bitumen that is produced by dissolving penetration bitumen in a solvent. These solvents are obtained through the oil distillation process in refineries. Depending on the rate of solvent evaporation, which determines the drying time, cutback bitumen is categorized into three types: Slow-Curing (SC), Rapid-Curing (RC), and Medium-Curing (MC).

Cut Back Bitumen Applications:

• Prime Coat:

In road construction, a prime coat is applied directly on the base course of the flexible pavement. The prime coat layer can use any of the three types of cutback bitumen, which include SC, MC, and RC. The grades of cutback bitumen that can be used in the prime coat layer are MC30, SC70, MC70, RC70, SC250, MC250, and RC250.

• Cold Asphalt:

Cold asphalt is a combination of aggregates and liquid bitumen, which is produced at ambient temperature. Cutback bitumen and bitumen emulsion are both viable options for cold asphalt. The following grades of cutback bitumen are commonly used in road construction: SC250, SC800, SC3000, MC70, MC250, MC800, MC300, RC70, RC250, RC800, RC3000

• Spray Sealing:

If the traffic on a particular road is light or medium and the road is damaged, asphalt may not be required to fix it. In such cases, a cheaper surface treatment option is spray sealing. In this process, a thin layer of cutback bitumen is sprayed onto the road surface, which helps waterproof the road and prevent water from penetrating the bottom layer. After that, stone aggregates should be poured onto the cutback bitumen layer.

• Tack Coat:

A tack coat is a thin layer of cut-back bitumen that is used to bind two layers of asphalt together. The bottom layer consists of bitumen penetration grade or viscosity bitumen and aggregates, which act as a binder course, while the top layer is the surface asphalt layer. Although

it is recommended to use bitumen emulsion in tack coat, MC grade cut-back bitumen is usually used in this layer.