Category: Bitumen

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Bitumen

Bitumen Types as It Usage

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

  1. Cutback bitumen
  2. fluxed bitumen

Cutback 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.

Fluxed Bitumen

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.

Curing

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.

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Bitumen Road Construction

Bitumen Used in Road Construction


Bitumen is used in road construction as a binder for the purpose of retaining the cover aggregate, and providing a waterproof seal to the pavement. It is a natural constituent of petroleum is refined to separate the various fractions (petrol, kerosene, distillate etc.) and recover the it.

There are also natural deposits of  bitumen . Often these deposits are mixed with variable quantities of mineral matter, water and other substances. Bitumen is a semi-solid material at normal temperatures and can be produced in a variety of classes.

One means of determining viscosity in the laboratory is to measure the time for a fixed of the bitumen to be drawn up through a capillary tube by means of a controlled vacuum
or accurately reproducible head.

Bitumen performs the functions of a binder because it possesses the following properties :-

(1)     it has a relatively strong cementing action,

(2)     it will readily adhere (under favorable conditions) to stone aggregate,

(3)     it is highly waterproof,

(4)     it is durable,

(5)     it is resistant to the action of most acids, alkali and salts,

(6)     it can be softened or liquified by –

(a)     the application of heat

(b)    the addition of kerosene or oil (i.e. “cutting” or “fluxing“)

(c)    emulsification with water.

Bitumen alone could be used as a binder in which case the only preparation necessary would be to raise its temperature just sufficiently to make it liquid enough to pump and spray. However, the usual practice is to use a  cutback bitumen binder.

Categories
Bitumen Road Construction

Cationic Bitumen Emulsions


The bitumen content of cationic bitumen emulsions used in Australia is generally between 60 and 70 percent. Bitumen used is either Class B160 or Class B80. A cationic emulsion may be used to better advantage than an anionic emulsion with acidic types of aggregate, such as granite, or in damp conditions.

Cationic bitumen emulsions are classified, according to their setting (or braking) times, into rapid setting (CRS), slow setting (CSS) and aggregate mixing (CAM).

(a)  Rapid Setting (CRS) : Rapid setting emulsion breaks rapidly on application. It is suitable for maintenance patching and sealing.

(b) Slow Setting (CSS) : Slow setting emulsion is suitable for soil stabilization.

(c)  Aggregate Mixing (CAM) : Aggregate mixing emulsion contains a proportion of oil to delay its setting time when mixed with aggregate. It is normally used for making cold mix to be stockpiled and progressively used over a period.

Bitumen emulsion used as binders seldom require any preparation other than possible warming to about 450C to facilitate spraying in cold weather. Heating above 500C should be avoided otherwise premature breaking may occur.

Categories
Bitumen Road Construction

Anionic Bitumen Emulsions


The bitumen content of anionic bitumen emulsions used in Australia is not less than 55 percent but this can be increased up to 70 percent. Bitumen used may be either Class B160 or Class B80.

Anionic bitumen emulsions are classified, according to their setting (or breaking ) times, as rapid setting (ARS), or slow setting (ASS).

(a)  Rapid Setting (ARS) : Rapid setting emulsion is one which breaks rapidly on application. It is suitable for maintenance patching and sealing. It may be diluted with water for light
application such as surface enrichment provided the dilution does not generally exceed 1 to 1 by volume. If hard water is used a suitable detergent should be added.

(b) Slow Setting (ASS) : Slow setting emulsion is one which has sufficient mechanical and chemical stability for mixing with densely graded aggregates, soils, or finely divided
materials of small maximum size. It may be used for soil stabilisation and for light applications where a high dilution with water (up to 10 to 1 by volume) is required. Slow
setting emulsions are usually produced to meet a special need which takes into account the characteristics of the materials involved.

Categories
Bitumen Road Construction

Bitumen Emulsion


A bitumen emulsion is an intimate mixture of two or more substances which normally do not mix together. Bitumen emulsion consists of a dispersion of tiny globules (4 to 10 microns in diameter) or bitumen in water, stabilized by the addition of an emulsifying agent.

The nature and quantity of the emulsifying agent controls the type and stability of the emulsion. Emulsions are manufactured by forcing the required proportion of bitumen, water and emulsifying agent into an homogenized, whereby the bitumen is broken up into the globules, dispersed and held in suspension by the emulsifying agent. The bitumen content of an emulsion can vary from 30% to 70% (usually 55-70%) by volume depending on the grade of emulsion required.

Emulsions are used primarily on maintenance work, surface enrichment, dust laying processes, slurry sealing, and in projects where weather conditions may prevent the use of hot
bitumen or cutbacks.

“Breaking” of an emulsion is the term applied when the bitumen globule suspension breaks down resulting in complete separation of the bitumen and water components. Breaking
normally occurs on the pavement surface after spraying whereby the water from the emulsion drains off or evaporates leaving behind a bitumen residue.

The surfaces of the suspended bitumen globules develop an ionic (electrical) charge. The type of charge depends on the emulsifying agent employed. The type of charge depends on the emulsifying agent employed. The presence of this charge is used to advantage to secure greater adhesion of the bitumen to the aggregate.

The basic types of bitumen emulsion are available :-
•    Anionic emulsions
•    Cationic emulsions.

The two types of bitumen emulsions are incompatible and should not be mixed under any circumstances otherwise premature breaking will occur. Some aggregates, particularly acidic types such as granite and quartzite, develop a negative ionic surface charge when wetted. If a cationic emulsion is used with such aggregate, the bitumen globules, which have a positive ionic surface charge, will be attracted electrochemically to the aggregate and a better bond will be established between the bitumen and the aggregate.

Similarly other aggregates, such as limestone, can develop positive surface charges and under these conditions an anionic emulsion containing bitumen globules with a negative ionic
surface charge is best used.

Categories
Bitumen Road Construction

Bitumen as Road Construction Material

When we discuss bitumen as road construction material, first 
Bitumen, this residue in the distillation involving natural bituminous primarily based raw petroleum is one of common binder. Distilled black is sometimes used by unique purposes. When it’s from high temperature, bitumen is usually liquid and also provides a lubrication which usually makes it possible for your asphalt to get spread and also compacted. Should the temperatures comes significantly under in which specific with regard to installing along with compacting, this mixture will probably restrict, distributing will become tough and it will be unable to end up being
compressed to the specified density.

As soon as the asphalt has become compressed and possesses refrigerated to normal heat range, your bitumen supplies the cohesion which often adheres the get aggregate together (for this reason the use of the phrase binder). At normal temperature bitumen is a semi-plastic stable. If the temperature increases or the particular pavement can be transporting slow-moving perhaps stationery traffic (at the traffic lights) the bond between blend particle is going to be reduce along with the blend a smaller amount stable. A R90 grade bitumen (80-100) penetration) is generally utilized in Queensland, on the other hand some sort of harder grade, e.g. R65 or even R45 may possibly always be attractive where traffic are very high as well as slow (at the traffic lights) or maybe the place that the local weather can be hot.


The  actual percentage of bitumen  used has to be controlled within tight limits for suit bitumen as road construction material. Too much bitumen will minimize friction involving the stone particles and therefore can lessen balance. Not enough bitumen can lead to bad compaction and a a lesser amount of dense and fewer durable pavement. The films connected with bitumen degrade while encountered with air along with climate. As a result a real mix together with way too small bitumen can decline easily particularly if it really is poorly compressed possesses too much the air void content material.