Tag: bitumen emulsion

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priming Road Construction

Dust Laying Using Bitumen Emulsions

We already discussed concerning the dust laying under bitumen emulsions. But, i figured to go over at length here “how are we able to apply” that Dust laying can be utilized on unsealed granular pavements to minimize dust nuisance, in addition to decrease maintenance costs and lack of  pavement material.

The work tip describes using  bitumen emulsion.   Dust  laying using bitumen emulsion is usually only applicable to low  traffic roads  (under about 100 v/l/d), hard standing areas, haul roads and temporary pavements on construction sites.

Bitumen Emulsions

Types Used for Dust Laying

The best option emulsion grade for dust laying is usually anionic slow setting (ASS) although cationic slow setting (CSS) could also be used.

Dilution

The emulsion is diluted with water just before use.  Dilution rates change from 4:1 water:emulsion to 12:1 water:emulsion, based on surface condition and application rate. A wetting agent or surfactant might be put into assist dilution and surface penetration.  The wetting agent should be suitable for the kind of  emulsion used.  Advice on compatible wetting agents and recommended dosage rates is obtainable from bitumen emulsion suppliers.

Compatibility from the water should be checked before diluting emulsion. When diluting emulsions, it is important to add water towards the emulsion, not emulsion to water to prevent premature breaking of emulsion. Only sufficient diluted emulsion for immediate use ought to be produced previously, as stored diluted emulsions are usually unstable.

Application Rates

An average application rate for diluted emulsion is all about 1.0 L/m2 of total liquid. If surface run-off occurs, the speed of application ought to be reduced. Lower application rates and better concentrations of emulsion are utilized on  hard surfaces . Higher application rates and much more diluted mixtures are utilized on softer and much more  permeable surfaces .

I am expecting write some more tips on dust laying  by using   bitumen emulsions  are in next post. You can Visit here.

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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.

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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.

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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.