Types of bitumen as it usage means, these are vary with usage such as climate conditions where it apply as well as quality of the work.
it can divided in to two groups
- Cutback bitumen
- fluxed bitumen
Cutting is the term used when a relatively volatile material such as kerosene is added to the bitumen. The added material is called a cutter and the resulting product is termed a cutback bitumen. Between 2 and 15 percent by volume of bitumen cutter is added to the bitumen, the actual percentage depending on the climatic conditions and the size of the cover aggregate. Higher ambient temperatures and use of larger sizes of aggregate will reduce the amount of cutter needed in the mix. Also less cutter will be necessary if heavy traffic is required to travel on the work soon after it is completed.
Fluxing is the term used when heavier grades of oil (e.g. diesel fuel oil) are added to the bitumen. The added oil is called a fluxing agent and the resulting product a fluxed bitumen.Fluxed bitumen are used where traffic and climatic conditions make slow curing of the binder desirable. The fluxing agent prolongs the period before serious hardening of the binder affects its performance. It is desirable that the binder remains as soft as possible, consistent with its ability to hold aggregate under the required conditions of traffic.
Loss of the volatile additive in the bitumen by exposure to air or heat is called “curing”. Cutback bitumen cure relatively rapidly. Fluxed bitumen cure very slowly. By varying the amount and relative proportion of cutter and fluxing agent and also the temperature, a wide range of curing times can be achieved.
It should be noted that although kerosene is described as a cutter, its volatility is in between that of petrol and diesolene. The lighter fractions evaporate progressively, leaving behind the heavier fractions which, being less volatile, in effect produce some fluxing effect.
There are three basic classifications for cutback and fluxed bitumen,
(1) Rapid-Curing (RC) – bitumen to which highly volatile solvents such as naphtha or petrol have been added.
(2) Medium – Curing (MC) – bitumen to which a solvent of medium volatility such as kerosene has been added.
(3) Slow – Curing (SC) – bitumen to which has been added oils of low volatility such as diesoline.
Within each of the basic classifications there exists a range of grades designed to meet the particular requirements of differing work.