Presented bylibvolume3.xyz/civil/btech/semester7/pavementmaterialsandconstruction/bituminous...Bitumen is generally heated to temperature of 100-140 degree celsius. The viscosity of

Presented by:

Ankit Shrivastava 09CE1019

G Sai Anvesh 09CE3002

Vishal Vinit 09CE1044

Sai Nikhil Thirandas 09CE1040

Aravind Kumar Dammu 09CE3016

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BITUMEN � Bitumen is a black, oily, viscous

material that is a naturally-occurring organic byproduct of decomposed organic materials.

� It is sticky,thick,Tar like form of petroleum derived from polycyclic aeromatic hydrocarbon

General uses of Bitumen: • Constructions of roads, runways and

platforms. • Water proofing to prevent water seepage. • Mastic floorings for factories and go-downs. • Canal lining to prevent erosion. • Dump-proof courses for masonry.

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Bitumen plays a vital role in road construction typically as binder. Application condition requires bitumen to behave as mobile liquid. There are three ways to reduce its viscosity: •Heat it •Dissolve it in solvents •Emulsify it. In heating it involves some: •Energetic •Environmental and •Health problems As process is inefficient and involves Loss of heat and even fumes causing air pollution

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In case using solvents: We make use of volatile dilatants like kerosene petroleum which adds to its cost although viscosity get reduced as it is uneconomical.

BITUMEN EMULSIONS

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What are emulsions?

An emulsion is a dispersion Of small droplets of one liquid in another liquid.

Emulsions can be formed by any two immiscible liquids, but in most emulsions one of the phases is water.

Oil-in-water (O/W) emulsions are those in which the continuous phase is water and the disperse (Droplet) phase is an

“oily” liquid.

Water-in-oil (W/O) “inverted” emulsions are those in which the continuous phase is an oil and the disperse phase is water.

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Types of emulsions:

(a) O/W emulsion, (b) W/O emulsion, (c) multiple W/O/W.

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BITUMEN EMULSION

Bitumen Emulsion is a 2-phase system consisting of •Bitumen •Water •Other Additives

•The bitumen is dispersed throughout the water phase in form of discrete globules, held

in suspension by electrostatic charges stabilized by emulsifier

•The Emulsion contains 40-75% of bitumen,.1-2.5%emulsifier,25-60%water and other

ingredients

•Typically of .1 – 50 µm in diameter.

•It is mainly dark brown in color after breaking changes to black.

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Primary objective is to use for road surfacing without much heating.

� As main advantages this improves the handling of bitumen at room temperature.

� Promotes surface interactions .

� Its mixture with the aggregate attains full strength.

� Economical and saves energy .

� Reduced atmosphere pollution.

� Water can also added before use to dilute as per requirement.

� Rains can not effect it at the time of use and after use.

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WHY BITUMEN EMULSIONS ?

Types:

Bitumen emulsions can be divided into four classes:

1) Cationic emulsions.

2) Anionic emulsions.

3) Non-ionic emulsions.

4) Clay-stabilized emulsions.

� The first two are most widely used

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Cationic emulsions � If an electric potential is supplied between two

electrodes immersed in an emulsion containing positively charged particles of bitumen, they will migrate to the cathode.

� This emulsion is said to be cationic.

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Anionic emulsions � If an electric potential is supplied between two

electrodes immersed in an emulsion containing negatively charged particles of bitumen, they will migrate to the anode.

� This emulsion is said to be anionic.

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Non-ionic emulsions � If the bitumen particles in the emulsion are neutral,

then they will not migrate to any of the pole.

� These type of emulsions are NON-IONIC.

� Mainly used in road ways.

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Clay-stabilized emulsions � These are mainly used for industrial applications.

� In these materials, emulsifiers are fine powders, often natural or processed clays and bentonites.

� Particle size is very much less when compared with the bitumen particles in emulsions.

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Manufacture of Bitumen emulsions � Bitumen emulsions can be manufactured using batch

process or continuous process.

� Bitumen emulsions are made in continuous inline processes involving dispersing technologies like rotor stators, colloidal mills and static mixers.

� High shearing forces are required for producing emulsions.

� Colloidal mills contain high speed rotors.

� Hot bitumen and emulsifier are fed simultaneously into colloidal mill.

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Manufacturing conditions � The speed of rotors is in the range of 1000-6000

revs/min.

� Bitumen is generally heated to temperature of 100-140 degree celsius.

� The viscosity of the bitumen is kept less than 2 poise.

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Figure 2. Schematic diagram of a bitumen emulsion plant

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� As an alternative to colloid mill, a static mixer can be used.

� This contains no moving parts.

� The high shear necessary to produce an emulsion is generated by pumping the input materials at high speed.

Role of Emulsifiers in Bitumen Emulsion

� An emulsifier is a substance which stabilizes an emulsion by increasing its kinetic stability.

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� In order to be effective, it must be water soluble and have a balance between hydrophilic & litho phobic properties.

� In emulsion, the ionic portion of emulsifier is located at surface of the bitumen droplet by hydrocarbon chain.

� The ionic portion of the emulsifier imparts a charge to the droplets themselves and counter-ions diffuse into the water.

� As the concentration of the emulsifier increases, the particle size of the emulsion is reduced.

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•In Simple emulsifier( ) ‘R’ represents the Hydrophobic (Lithophilic)portion of emulsifier •Usually long chain hydrocarbon consisting of 8 to 22 carbon atoms. •The Hydrophilic can consist of amines , sulphonates , ether, alcohols.

−+

− ClNHR 3

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� It performs various functions within bitumen emulsion.

1. Makes emulsification easier by reducing the interfacial tension between bitumen and water.

2. Stabilize the emulsion by preventing coalescence of droplets.

3. Dictates its performance characteristics such as setting and adhesion .

4. Emulsifier also decreases rate of flocullation.

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Emulsifier functions

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BY USING EMULSIFIER

Types of Emulsifier:

1. Anionic

2. Cationic

3. Non-ionic

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Defined on basis of polar bonds

� Cationic emulsifier-Electrovalent and Polar head group is positively charged & imparts positively charged to the surface of the bitumen droplets.

� It is prepared by dissolving hydrocarbon amines in acids

E.g.

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−

−+

− ClNHR 3

� Anionic emulsifier-Electrovalent and Polar head group is negatively charged & imparts negatively charged to the surface of the bitumen droplets.

� It is produced by dissolving fatty acids in sodium hydroxides.

� E.g.

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+−− NaCOOR

HOCHCHCOORX

)( 22−

� Non ionic –The hydrophilic head group is covalent , polar and dissolves without ionization.

Note-There are products with amphoteric head group character which may adopt positive or negative charges depending on pH

.

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Properties of bitumen emulsion

It is stable under transportation ,storage &application condition.

But it may break soon after application.

It may have low viscosity

It may f low due to irregular spraying but not due to road irregularities

Important properties of Bitumen emulsion:

1. Stability

2. Viscosity

3. Breaking

4. Adhesivity

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Emulsion stability

� This property indicates the resistance ability to change properties over time. As stability is very important in storage ,transport & use.

� Stable emulsion will change over time slowly.

� Reason for instability can be physical or chemical process.

� As emulsion is a example of colloidal system in non equilibrium state. If system reaches to equilibrium

Emulsion will go through several process like flocculation, sedimentation, and coalescence leading to instability of emulsion

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Fig: Schematic view of some of destabilizing processes

Emulsion Viscosity

� The viscosity of the bitumen emulsion is important for pumping and transportation.

� In some applications, for example surface dressing, bitumen emulsion is sprayed on the road. In this case the viscosity is critical. As It should be low enough to permit even spraying but at the same time high enough to prevent run-off, once it is sprayed on the road.

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Emulsion breaking

Bituminous emulsions are designed to “break” deliberately in contact with moist aggregates, releasing a binder film on and between the mineral aggregates.

There can be two kind of breaking:

1. Breaking of anionic bitumen emulsions

2. Breaking of cationic bitumen emulsions

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Breaking of anionic bitumen emulsions: It involves the substantial removal of water. Mainly by evaporation but also by absorption through surfaces in contact, particularly those of mineral aggregates.

Breaking of cationic bitumen emulsions:

For cationic emulsions a significant factor which contributes

towards the breaking, in addition to removal of water, is a

physiochemical effect which involves adsorption of positively

charged emulsifiers on to negatively charged surfaces in contact,

thus assisting in the destabilization of the emulsion.

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Emulsion adhesivity

� The physical-chemical adsorption of bitumen and surfactant onto the mineral surface is governed by Vander Waals attraction forces, electrostatic forces or covalent and electrovalent bindings, and responsible for the film adhesion.

� To optimize the bitumen adsorption on substrate, surfactant

concentration should be slightly lower than the critical micelle concentration (CMC), nevertheless surfactant concentration higher than CMC is necessary to increase the stability of the unstable thermodynamic emulsion. Ionic surfactant can adsorb on slightly charged substrates. Non-ionic surfactants adsorb on mineral surfaces mostly by hydrogen bonding or Vander Waals attractive forces. The adsorption of surfactant changes the hydrophobic hydrophilic behaviour of the substrate, thus acting on the adhesion of the bitumen.

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Standards

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1- Rapid Setting

(RS-1) :

Provides rapid deposition - mainly

used for Tack Coat.

2- Rapid Setting

(RS-2) :

Provides rapid deposition – mainly

used for Tack Coat and Surface Dressing.

3- Medium

Setting (MS) :

A versatile grade, Provides

Comparatively slower deposition, used for Repair work/surface

dressing, Plant or road mixes with coarse aggregates and Penetration

macadam.

4- Slow Setting-1

(SS-1) :

Consumes long time to form

bituminous film with best penetration on a porous medium, used for Prime

coat, Crack sealing and Fog Seal.

5- Slow Setting-2

(SS-2) :

Low in solvents, provides slow

deposition of bituminous film, used for plant or road mixes like MSS,

SDBC, Slurry Seal and for Prime coat applications.

As per Indian Standard (IS-8887:2004), five grades of Cationic Bitumen Emulsions are available: The International Standard (ASTM D 2397-05) materials in four grades with sub-grades are available (which differ prominently in their chemical

and setting profiles) as: 1- Rapid Setting Sub-grade : CRS-1 & CRS-2 2- Medium Setting Sub-grade : CMS-2 & CMS-2h 3- Slow Setting Sub-grade : CSS-1 & CSS-1h 4- Quick Setting Sub-grade : CQS-1H

IS 7393:1974

Uses of Bitumen emulsion

� Crack Filling: To stop entering water in structural layer of pavement Bitumen emulsions preferably containing rubber are used as they are inexpensive and effective.

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Grouting: It is the method of construction or stabilizing of road surfaces and footpath. Emulsion is applied to compacted dry aggregate and due its low viscosity it penetrates through void structure of the aggregate.

� Soil Stabilization: For agricultural land where fresh top soil is susceptible to surface erosion ,bitumen emulsion can be used as binding agent also helps in retaining soil moisture & improving thermal insulation

� Slip layer & concrete curing: Bitumen emulsions are used to create a membrane between layers of concrete to retain strength of upper layer by preventing water seepage into lower layers by avoiding rigid adhesion. Also it is sprayed on top surface to avoid evaporation of water.

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� Tack/bond coats

� Protective coats

� Slurry seals

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It has been given us possibility to apply wide range of new technologies and methods for road construction, repair and keeping. And most important thing is that it is all inexpensive and do not affect environment However continuous development and learning how to make bitumen-emulsions which would fit with local conditions, materials, technology requirements and standards must be carried on.

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CONCLUSION

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Once an emulsion is applied to a surface the bitumen must separate from the liquid phase. The water is removed while the bitumen remains to coat the surface. Separation of the bitumen and water may be due to evaporation or due to the chemical nature of the surface.

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