BITUMEN IN DIFFERENT FORMS
- Cutback Bitumen
It is common practice to heat bitumen to lower its viscosity. In other cases, liquid binders, such as cutback bitumen, are preferred. An appropriate solvent is utilized to reduce the viscosity of cutback bitumen.
Cutback bitumen is also favored from an environmental standpoint. The bituminous material’s solvent will evaporate, and the bitumen will bond the aggregate. Cutback bitumen is used in the building and maintenance of cold-weather bituminous road construction.
Naphtha, kerosene, diesel oil, and furnace oil are the distillates used to make cutback bitumen. Cutback bitumen comes in three varieties: rapid curing (RC), medium curing (MC), and delayed curing (SC).
Surface treatment and patching should be done with RC. MC is recommended for premixes containing less fine particles. SC is used to premix with a significant amount of fine aggregates.
- Bitumen Emulsion
Bitumen emulsion is a liquid product in which bitumen is suspended in an aqueous medium in a finely divided state and stabilized with appropriate material. In India, cationic emulsions are typically employed.
The bitumen component of the emulsion is around 60%, with the remainder being water. When the emulsion is laid for bitumen road construction, it degrades, releasing water and causing the mixture to set. The time required for setting is determined on the quality of bitumen.
There are three varieties of bituminous emulsions: rapid setting (RS), medium setting (MS), and slow setting (SS) (SC). Bitumen emulsions are excellent binders for the building of steep roads. Where bitumen or aggregate heating is problematic. For surface treatment, rapid setting emulsions are utilised. For premix projects and patch repairs, medium setting emulsions are suggested. In the rainy season, slow-setting emulsions are preferable.
- Bitumen Primers
The distillate in bituminous primer is absorbed by the road surface on which bitumen road construction is spread. As a result, the porosity of the surface influences absorption. Bitumen primers can be used on stabilised surfaces as well as water-bound macadam base courses.
Bituminous primers are often made on bitumen road construction sites by combining penetrating bitumen with petroleum distillate.
- Modified Bitumen
Bitumen modifiers are additives or blends of additives that can improve the qualities of bitumen and bituminous mixtures. Modified bitumen is bitumen that has been treated with various modifiers. Polymer modified bitumen (PMB)/ crumb rubber modified bitumen (CRMB) should be utilised only in wearing courses where extreme climate fluctuations are required. It should be emphasised that the performance of PMB and CRMB is highly reliant on temperature management during construction. The following are the benefits of utilising modified bitumen:
- Reduced sensitivity to daily and seasonal temperature fluctuations
- Higher deformation resistance of bitumen road structure at high pavement temperatures
- Improved ageing resistance characteristics
- Mixtures with a longer fatigue life
- improved aggregate and binder adhesion
- Crack prevention and reflective cracking