s52_emulsions - tack coat to chip seal_ltc2013

8/12/2019 S52_Emulsions - Tack Coat to Chip Seal_LTC2013

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EmulsionsTac k Co at to Ch ip Seal

Danny Gierhart, P.E.

Regional Engineer Asphalt Institute


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Emulsion Properties

Storing, Handling, andSampling

Common Uses of AsphaltEmulsions

Overview


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What is an asphalt emulsion?

Microscopic asphaltdroplets suspendedin water.

Mostly about 5 m indiameter, rangingfrom 1-20 m

Emulsifiers orsurfactants holdthese droplets insuspension.

100 micron/0.1mm


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Negatively- Charged Emulsions areclassified into 3 main types

RS (Rapid Setting)

MS (Medium Setting)

SS (Slow Setting)


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CRS (Rapid Setting)

CMS (Medium Setting)

CSS (Slow Setting)

Positively- Charged Emulsions are alsoclassified into 3 main types


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Additional Nomenclature

QS = Q uick SetHF = High Float1 = Binder residue = 60% Minimum

2 = Binder Residue = 65% Minimumh = Hard Pen Asphalt Bases = Soft Pen Asphalt Base or sometimes

Solventl and/or p = Latex and/or Polymer


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Emulsifier HeadLoves WaterHates Oil

Emulsifier Tail

Loves Oil

Hates Water

Asphalt Emulsifier


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Emulsifier Orientation at the Asphalt/WaterInterface

Opposite charges attractand same charges repel

Surface charge determined byemulsifier type and water pH


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Stabilization of Asphalt Droplets

+ + +++ +

Cationic emulsion-electrostatic repulsion prevents close approach ofdrops

no charge- droplets can come into contact and coalesce

- - --- -

Anionic emulsion-electrostatic repulsion prevents close approach ofdrops


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Aggregate Charge

Limestone

Dolomite

Basalt

Granite

pos. negative


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Anionic emulsions(negatively charged)typically bond best withpositively chargedaggregates (limestones).

Cationic emulsions(positively charged)typically bond best withnegatively chargedaggregates (granites,sandstones, basalts).

Asphalt Emulsions


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Slowest Fastest

Emulsifier / Emulsion Reactivity

CSS CQS HF CMS CRS


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Larger particles settle faster Denser particles settle faster Low viscosity, Low residue emulsions are liable to settle Settlement is less in hot storage temperature The opposite is called creaming If unchecked settlement can be very hard to re-disperse.

Asphalt Emulsion Storage and Handling


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Hard water, pH changes, or contamination can reducethe charge on the droplets

When charge is insufficient to keep particles apart thenthey stick together (flocculation)

Flocculation may be reversible or lead to coalescence. High shear can also force particles together

Asphalt Emulsion Storage and Handling


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Old Material

Old material fromlast season will

not work well. A small amount ofold material willcontaminate aload of newmaterial.


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Temperature Problems

Dont overheatemulsions

(Distributors) Dont allowemulsions to freeze(ever)

Dont add cold waterto emulsions


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Tanker and Distributor Contamination

Dont Mix Hot Asphaltswith Emulsions

Dont Mix Cationic and

Anionic Dont Mix Old and New Dont Mix Emulsions

with sealers

Dont Mix Emulsionswith other chemicals,salts, etc.


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Job Site Storage of Emulsions

Try to order so allmaterial is usedevery day

Fresher is better Less exposure to

air is better Clean out all

storage tanks overthe off season


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Testing and Sampling

Only good samplefrom the emulsion

storage tank Samples must behandled correctlyand tested quickly


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AASHTO T 40 - Sampling Containers

Allowable containers: Anionic Emulsions - wide-mouth plastic or

glass jars or bottles.

Cationic Emulsions - wide-mouth plastic jars or bottles or wide-mouth cans withscrew caps.

Containers need to be new, not washed,

rinsed, or wiped with an oily cloth.


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Major Uses of Asphalt Emulsions

Chip Seal Sand Seal Slurry Seal Micro surfacing Cape Seal Fog Seal Scrub Seal Penetration

Macadam

Surface Treatments


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Cold In-Place Full Depth

Reclamation Hot In-Place

Asphalt Recycling


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Tack Coat Prime Coat Dust Palliative Crack Fill Cold Mix Paving Maintenance

Patch

Other Applications


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s52_emulsions - tack coat to chip seal_ltc2013

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