Emulsions 101

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Emulsions 101
Sponsored by Minnesota LTAP Center Presented
by Michael Marti, P.E. SRF Consulting
Group, Inc. Dan Wegman, P.E. SemMaterials
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Why are there Emulsions?

• Asphalt is a semi-solid or solid at room
  temperature
• For workability it must be in a liquid state
• It can be liquefied by
• heating (HMA)
• adding petroleum solvents (Cutbacks)
• emulsifying in water (Emulsions)

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Cutbacks

• Petroleum solvent (naphtha or kerosene) is added
  to base asphalt to make fluid
• Solvent then evaporates restoring asphalts
  binding properties
• Health and environmental concerns
• Flammable Working temps of 275-300ºF
• Hydrocarbon emissions into atmosphere
• Other concerns expense, sensitive to bleeding

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Emulsions

• Definition of emulsion
• Suspension of small droplets of liquid in a
  second liquid with which the first liquid will
  not mix
• Allows for handling at air temperatures.
• Consists of
• asphalt
• water
• emulsifying agent (surfactant)

• Breaking occurs (separation of the asphalt and
  water)
• Upon curing, the residual asphalt retains all of
  the adhesion, durability, and water-resistance of
  the original asphalt cement

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Emulsions

• Definition of emulsion
• Suspension of small droplets of liquid in a
  second liquid with which the first liquid will
  not mix
• Allows for handling at air temperatures.
• Consists of
• asphalt
• water
• emulsifying agent (surfactant)

• Breaking occurs (separation of the asphalt and
  water)
• Upon curing, the residual asphalt retains all of
  the adhesion, durability, and water-resistance of
  the original asphalt cement

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Emulsifying agent

• Surface-active agent, or surfactant
• Keeps asphalt droplet in stable suspension
• Controls breaking time
• Determines classification

• Rapid Set RS
• Medium Set MS
• Slow Set SS
• 1 or 2, relative viscosity
• h indicates harder asphalt

Cationic C, positively ()
charged Anionic, negatively (-) charged
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Factors Affecting Breaking/Curing

• Weather Conditions
• Temperature, humidity, wind
• Water Absorption
• Aggregate moisture content
• Although wet aggregate may facilitate coating, it
  tends to slow the curing process
• Mechanical forces
• Roller pressure forces water from mix
• Surface area
• Excessive fines or dirty aggregate accelerate
  breaking
• Surface chemistry

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Advantages of Emulsions

• Safer (Working temps 150º vs 275ºF)
• Delivered at useable temperature (no need to
  heat)
• No solvents released to environment
• Will adhere to wet aggregates
• Less expensive
• Ability to control breaking process
• Built in anti-strip (better adhesion)

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Modifiers

• High Floats

Emulsion Grade AC
High Float Residue

• Polymers

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High Floats

• Most emulsifiers are designed to have little
  effect on the properties of the asphalt after the
  emulsion has cured.
• High Floats are the exception.
• High floats are designed to form a networked
  gel structure with the asphalt.
• Gel structure, similar to Jell-O, keeps the
  asphalt from flowing

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Why use High Floats?

• Gel structure has little effect at low
  temperature but keeps asphalt from flowing at
  higher temperatures (road surface on hot summer
  days)
• Allows the use of a softer base AC
• less brittle at lower temps
• (reduces thermal cracking)
• less runny at high temps
• (reduces bleeding)

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When should High Floats be used?

• Very good for dirty aggregate
• Emulsion are designed to begin breaking when they
  come in contact with aggregates
• High Floats set slow enough to soak through
  dust/dirt and lock on to rock
• Dusty hand test
• Areas susceptible to bleeding

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Why is it called High Float?

• Refers to passing the float test
• ASTM D139 AASHTO T-50
• Emulsion residue poured into aluminum float
• Placed in water bath (140ºF) for 20 minutes

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Polymer Modification

• What is it?
• Made of many (poly) small molecules (monomers)
• Monomers chemically reacted to one another
• Why?
• Extra performance and durability
• Reduced life cycle costs
• How?
• Many different process

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Benefits of Polymer Modification

• Early chip retention
• Better adhesion and elasticity at low
  temperatures (pushed rocks will get pulled
  backed)
• Reduced bleeding and flushing
• Enables use of chips seals for higher volume
  roads
• Retards aging process (more self healing)

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Handling Emulsions
Storage

• Use vertical tanks (less surface area)
• Keep warm (check with supplier)
• If over extended period, gently mix

• Dos
  

• Do not store for extended periods of time
• Do not contaminate
• Do not store at high temperatures (gt185ºF)
• Do not let freeze

Don'ts

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Handling Emulsions
Heating

• Heat slowly with indirect heat
• Agitate slowly while heating
• Follow suppliers recommendations

• Dos
  

• Do not heat above 185ºF
• Do not heat with steam
• Do not heat for a long time
• Do not heat too quickly
• Do not allow to cool lower than 60ºF

Don'ts

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Handling Emulsions
Pumping

• Use pumps with proper clearance
• Warm pumps before pumping
• Fill pump with fuel oil to prevent seizing
• Pump in and out of the bottom of the tank

• Dos
  

Don'ts

• Do not splash material when pumping
• Do not pump excessively

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Review

• What does CRS stand for?
• Cationic Rapid Set
• When would you use a high float emulsion?
• With dirty/dusty aggregates
• Areas susceptible to bleeding
• What factors effect curing/breaking?
• Temperature, humidity, wind, Water Absorption,
  Aggregate moisture content, Mechanical forces,
  Surface area, Surface chemistry