1. cutback bitumen
It is common practice to heat bitumen to reduce its viscosity. In some situations the use of liquid binders, such as cutbacks, is preferred. bitumen In cutback bitumen, a suitable solvent is used to reduce the viscosity of the bitumen. Environmentally, cutback bitumen is also preferred. The solvent from the bituminous material will evaporate and bind to the bitumen aggregate. Cutback bitumen is used for cold weather bituminous road construction and maintenance. The distillates used for the preparation of cutback bitumen are naphtha, kerosene, diesel oil and furnace oil. There are different types of cutback bitumen such as rapid curing (RC), medium curing (MC), and slow curing (SC). RC is recommended for surface dressing and patchwork. MC is recommended for premixes that contain small amounts of fine aggregates. SC is used for premixes with appreciable amounts of fine aggregates.
2. bitumen emulsion
Bitumen emulsion is a liquid product in which bitumen is suspended in a finely divided state in an aqueous medium and stabilized by a suitable material. Generally cationic type of emulsion is used in India. The bitumen content in the emulsion is about 60% and the rest is water. When the emulsion is applied outdoors, it breaks down resulting in the release of water and solidification of the mixture. The setting time depends on the grade of the bitumen. The viscosity of bituminous emulsion can be measured as per IS: 8887-1995. There are three types of bituminous emulsion available, which are rapid setting (RS), medium setting (MS), and slow setting (SC). Bitumen emulsions are ideal binders for hill road construction. Where bitumen or aggregates are difficult to heat. Rapid setting emulsion is used for surface dressing work. Medium setting emulsion is preferred for premix job and patch repair work. Slow setting emulsions are preferred during rainy season.
3. bituminous primer
In bituminous primer, the distillate is absorbed by the road surface over which it is spread. Hence the absorption depends on the porosity of the surface. Bitumen primers are useful on stable surfaces and water-bound macadam base courses. Bituminous primers are usually prepared on road sites by mixing penetration bitumen with petroleum distillate.
4. modified bitumen
Certain additives or mixtures of additives called bitumen modifiers can improve the properties of bitumen and bituminous mixes. Bitumen treated with these modifiers is known as modified bitumen. Polymer Modified Bitumen (PMB) / Crumb Rubber Modified Bitumen (CRMB) should be used only in the course of wear based on the requirements of extreme climatic variations. Detailed specifications for modified bitumen have been issued by IRC: SP: 53-1999. It should be noted that the performance of PMB and CrMB is dependent on the strict control of temperature during manufacturing. The advantages of using modified bitumen are as follows
- Low sensitivity to daily and seasonal temperature variations
- High resistance to deformation at high pavement temperatures
- superior age resistance properties
- High fatigue life for blends
- Better adhesion between aggregate and binder
- Prevention of Cracking and Reflective Cracking
The desirable properties of bitumen depend on the type and formulation of the mixture. In general, bitumen should have the following desirable properties.
- Bitumen should not be sensitive to extreme temperatures: the mixture should not be too soft or unstable during the hottest weather, and the mixture should not be too brittle in cold weather, which could lead to cracks.
- The viscosity of bitumen should be sufficient at the time of mixing and compaction. This can be achieved by heating the bitumen and aggregate before mixing or using a suitable grade of cutback or emulsion.
- There must be sufficient affinity and adhesion between the bitumen and the aggregate used in the mixture.