Bitumen Emulsion

Description

Bitumen emulsion consists of three basic ingredients: bitumen, water, and an emulsifying agent. Based on specifications it may contain other additives, such as stabilizers, coating improvers, anti-strips, or break control agents. It is well known that water and asphalt will not mix, except under carefully controlled conditions using highly specialized equipment and chemical additives.

Uses

Cationic emulsions may be used at ambient temperatures with aggregates, which need not be completely dry. Emulsions are less hazardous to use and can be applied in a wider range of conditions

SPECIFICATION FOR EMULSION BITUMEN.

RANGE OF BIPL EMULSIONS AVAILABLE

Packing
Standard Seaworthy Exportable Packing in200 Kg Reconditioned Drums
Palletizing is required for Cutback Bitumen & Emulsions -200kg drums shall be secured as 4 drums per pallet

Steel Drum Sizes
Drum Size 200 kg Drum
Height 980mm
Diameter 520 – 550mm
Thickness 0.6 – 0.8mm

CATIONIC EMULSIONS
When asphalt is milled into microscopic particles and dispersed in water with a chemical emulsifier, it becomes an asphalt emulsion. The tiny droplets of asphalt remain uniformly suspended until the emulsion is used for its intended purpose. In the emulsion state, the emulsifier molecules orient themselves in and around droplets of asphalt. The chemistry of the emulsifier/asphalt/water system determines the dispersion and the stability of the suspension. When emulsions are used in the field, the water evaporates into the atmosphere, and the chemical emulsifier is retained with the asphalt.

Their early use was in spray applications and as dust palliatives. The growth in the use of asphalt emulsions was relatively slow, limited by the type of emulsions available and a lack of knowledge as to how they should be used. Continuing development of new types and grades, coupled with improved construction equipment and practices, now gives a broad range of choices. Virtually any roadway requirement can be met with emulsions. Judicious selection and use can yield significant economic and environmental benefits.Emulsions are less hazardous to use and can be applied in a wider range of conditions.

An asphalt emulsion consists of three basic ingredients: asphalt, water, and an emulsifying agent. On some occasions, the emulsion may contain other additives, such as stabilizers, coating improvers, anti-strips, or break control agents. It is well known that water and asphalt will not mix, except under carefully controlled conditions using highly specialized equipment and chemical additives. The blending of asphalt and water is the same as an auto mechanic trying to wash grease from his hands with only water. Only with a detergent or soapy agent can grease be successfully removed. The soap particles surround the globules of grease, break the surface tension that holds them, and allow them to be washed away.

Anionic, non-ionic and cationic emulsifiers are all available, which will successfully emulsify bitumen and provide storage stable emulsions. Cationic emulsifiers offer additional advantages, which arise from the fact that most naturally occurring aggregates are negatively-charged in aqueous media, and have a capacity to absorb cationic emulsifiers. Choice of emulsifier type, and emulsion formulation enables the rate of breaking of the emulsion to be controlled. The emulsifiers remain in the cured seal and are concentrated at the interface between bitumen and aggregate and act as antis tripping agents.

What is prime coat and tack coat?
Prime Coat– It is typically have been spray applications of low viscosity asphalt on granular base in preparation for placing an asphalt mixture. A prime coat performs several important functions:
• Coats and bonds loose mineral particles on the surface of the base
• Hardens or toughens the surface of the base
• Waterproofs the surface of the base by plugging capillary or interconnected voids
• Provides adhesion or bond between the base and the asphalt mixture

In order for the prime coat to satisfy these functions, some asphalt must penetrate into the base. Prime coats generally are being used less frequently, particularly when the total asphalt thickness is 100 mm (4 in.) or greater. With increased asphalt thickness, there is less possibility of surface water penetration into and pavement slippage on the base. A prime coat should be considered, however, when a granular base is to be carried through an extended period, such as the winter months, or when to be exposed to abrasion damage by traffic. Even though some engineers question the benefits of priming, it should be considered when any doubts exist about the results if it were eliminated.

In the past, the asphalt for prime coating was usually a low viscosity, medium or rapid curing (MC or RC) cutback asphalt. The use of asphalt emulsions is increasing and new emulsion grades have been developed for priming. SS-1, SS-1h, CSS-1 and CSS-1h can be used.

The emulsion grade and/or technique selected to replace cutback asphalt for a penetrating prime will depend upon a number of factors. The amount and size of voids in the base material will influence emulsion penetration and determine the emulsion grade, application rate, dilution, and if multiple applications and mixing are required.

When the base surface consists of fine grained materials, those passing the 75-µm (No. 200) sieve, the surface will act as a filter and not let the emulsion asphalt particles penetrate. Dampening the surface and/or the adding surfactants cannot overcome the filtering action. Being a mechanical problem, it requires a mechanical solution. Therefore, the surface may need to be loosened by scarifying and the emulsion mixed to a specific depth for an acceptable prime.

Emulsions for priming almost always require dilution with water. The dilution rates normally have ranged from 1:1 to 10:1 (water to emulsion) dependent upon the base material characteristics and method of treatment. The application rates can vary for a 1:1 diluted emulsion from as low as 2.3 l/m2 (0.5 gal/yd2) for high fines and tight bases and up to 6.8 l/m2 (1.5 gal/yd2) for loose sands and very porous surfaces. In very dense
material, it may be necessary to use a higher dilution and make multiple applications at lower rates. This is done to improve penetration and prevent runoff and puddling of the emulsion.

Tack Coat

A tack coat is a very light spray application of diluted asphalt emulsion. It is used to create a bond between an asphalt overlay being placed and the existing surface. A tack coat is recommended for all overlays. The only possible exception might be when an additional course is placed within two to three days on a freshly-laid asphalt surface.

Asphalt emulsions commonly used for tack coats are diluted SS-1, SS-1h, CSS-1 and CSS-1h. The emulsion is diluted by adding an equal amount of water. A test dilution is recommended to be certain that the water to be used is compatible with the emulsion. To prevent premature breaking, the water always is added to the emulsion and not the emulsion to the water. If practical, warm water is preferred for dilution. The diluted material typically is applied at a rate of 0.25 – 0.70 l/m2 (0.05 – 0.15 gal/yd2). Tack coat should be applied only to an area that can be covered by the same day’s paving.

The best results are obtained when the tack coat is applied while the pavement surface is dry and the surface temperature is above 25°C (80°F). The surface to be tack coated must be clean and free of loose material so it will adhere. A good tack coat results in a very thin but uniform coating of residual asphalt on the surface when the emulsion has broken.

Too much tack coat can create a slippage plane between two pavement courses as the asphalt acts as a lubricant instead of an adhesive. Fat spots or bleeding could occur on the surface of the new pavement that are not only unsightly but can produce slick pavement conditions. Pneumatic-tired rolling of spotty or non-uniform tack coats will help spread the asphalt and lessen the probability of fat spots.

After spraying the tack coat, time must be allowed before the overlay is placed for the complete breaking of the diluted emulsion (brown to black color). Traffic should be kept off of the tacked area. Freshly tacked pavement is generally too slick for safe driving, particularly before the emulsion has broken.

A tack coat also is essential in a good patching operation. The area to be patched must be thoroughly cleaned and all loose material removed. A fairly heavy tack coat of asphalt emulsion is then sprayed or painted over the entire area to be patched, including vertical sides. The tack coat helps hold the patch and provides a watertight seal between the patch and surrounding pavement.

Applications Areas

The four main application areas are surface dressing, tack coats, slurry sealing, and cold mixing.
Surface Dressing Road maintenance technique, that involves the restoration of a deteriorating road wearing course, before the main fabric of the road foundations are irreparably destroyed.
Tack Coats Provide a thin adhesive film of bitumen between an existing road pavement and overlay, or between courses in road construction.
Overlay materials include hot rolled asphalt wearing courses and slurry seal. Tack coats are also used in patching and inlay work, where further functions of priming and waterproofing are necessary.
Tack coat forms an adhesive and cohesive bond between the bituminous overlay and the existing pavement, reducing the risks of slippage between the two courses, and allowing traffic stresses to be distributed uniformly.

The problems caused by surface dust on the road are minimised. A further advantage of a tack coat is during the paving or rolling of the new overlay, pushing and sliding are reduced , thereby allowing for improved compaction, with a resultant increased life expectancy of the surfacing.

Slow Seting

Cationic asphalt emulsion designed for use as a prime coat (when it is diluted) tack coat, base stabilization, fog sealing, dust control and specialty applications.
Slow setting emulsions are the most stable of emulsions, and generally can be diluted with water and mixed with mineral fillers and aggregates for all uses, the air and pavement temperatures at construction should be sufficiently high to allow the emulsion to fully cure.

Emulsions Applications
Surface dressing- Cationic emulsions for surface dressing are 70% binder content, applied hot (80-90C), or 60¬65% binder content, applied cold. The emulsion must set rapidly to anchor the chippings to the road surface

Slurry seal 60% slow setting Mixes, open-graded 60% medium setting Mixes, dense-graded 60% slow setting Penetration macadam. Slurry Sealing is a technique for road repair in which a fluid mix of finely grained aggregate bitumen emulsion and water is applied to the road surface. On the road this slurry sets quickly to provide a new wearing surface, (the seal). The thickness of the seal is normally 2-15 mm (can be up to 40 mm) and the final surface has a texture, wearing and load bearing characteristics similar to those of fine cold asphalt, depending on the aggregate and grading used. The seal is impenetrable to water and so ensures protection against ingress of water and is ideal for sealing existing surfaces which are cracked, fissured or pitted. The seal also provides a contribution to riding quality (noise reduction) and an improved resistance to skidding.

Grouting 60-70% rapid setting Sub-base and base sealing of cement mixes 40-60% rapid or medium setting Sub-base and base sealing 60-70% rapid setting

Re-treading 60% medium setting Stone coating 60% medium or slow setting Mist spraying 40% rapid or medium setting Concrete curing 40% rapid or medium setting

Cold mixing traditionally, deferred set Macadams (hot mix) are produced by coating mixed aggregates with hot bitumen, flux oils being added to adjust the binder viscosity and so extend the storage life of the finished product. These materials are mainly used in trench reinstatement and remedial patching. The Macadam may be stockpiled for a period of time before laying, and must remain workable, while at the same time providing good stability when laid.

The disadvantages of this method are:
a) The necessity of heating the aggregate to the temperature required to ensure its dryness and so facilitate adequate coating.
b)The operating temperatures that are necessary, give rise to a fire hazard, which is associated with the use of relatively low flash point flux oils.
c) The probability of loss of volatile oils from the flux, giving rise to unpredictable properties with regard to workability.

The development of cold mixing has to a great extent overcome these disadvantages and certain additional benefits:
Control of Emulsion Breaking
The breaking of an emulsion in contact with aggregate is initiated by:
i) Adsorption of emulsifier onto the aggregate until the emulsifier remaining at the bitumen droplet surface is insufficient to prevent coagulation.
ii) Neutralisation of emulsion acidity by reactive aggregates and fillers leading to a loss in
Positive charge on the bitumen droplets and therefore coalescence occurs. So the rate of breaking depends, for example;

a) The adsorption capacity of the aggregate for emulsifier this is related to the aggregate type and grading. The fines content and type of fines present can Have a disproportionally large influence
b) The reactivity of aggregates to emulsion acidity Aggregates like limestone which react with acids, will clearly have the largest effect on emulsion breaking.

Comparison of Emulsion and Cut-Back Bitumen
Cationic Emulsions

-Sprayed 80-90 0C -Low Solvent Content -Low Fire Hazard -Breaks by Chemical Reaction
– Possible in Damp Conditions
– Coated Chippings Not Required
– Built-In Adhesion Agent Unaffected by Emulsion Storage

Cut Back Bitumen

-Sprayed 140-160 0C -High Solvent Content -Fire Hazard -Solvent Evaporation
– Not Recommended in Damp Conditions -Coated Chippings Recommended when
– Spraying at Low Temperature or with Viscous Binder.

Advantages

a) Cationic emulsions may be used at ambient temperatures with aggregates, which need not be completely dry.
b) Lower costs are incurred due to a considerable saving on fuel for heating purposes.
c) Operating at lower temperatures for cold mixing gives a greater margin of safety, even though these emulsions may contain fluxing oil.
d) Not only may cold mix be stockpiled for long periods, but it may also be packaged in small containers and stored. This facilitates the treatment of very small areas quickly, cleanly and economically.

Disadvantages

Even though cationic bitumen emulsions have many advantages over cut-back binders, they also have certain disadvantages:
Climatic – A regular water supply is required and this can be a great problem in very hot countries, where water can be in very short supply.

Also aggregates in arid regions are often very dry and cationic emulsions work most effectively, especially mixing with moist aggregate.
ii) Stability Emulsions are inherently unstable with limited shortage life, (generally maximum 6 to 12 months).
iii) Plant Emulsion manufacture requires specialised plant and quality control procedures.
iv) Bitumen Special emulsifier grade binders are needed to make the best quality emulsions.

• Penetration @ 25 degC , 100 g, 5 Seconds
  2. Soulbility in Trichloroethylene
  3. Maximum Sieve – 0.1%
  4. Max Storage Stability @ 1 day – 1%
  5. Particle Charge- Positive