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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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Presentation on theme: "Emulsions 101 Sponsored by: Minnesota LTAP Center Presented by: Michael Marti, P.E. SRF Consulting Group, Inc. Dan Wegman, P.E. SemMaterials."— Presentation transcript:

1 Emulsions 101 Sponsored by: Minnesota LTAP Center Presented by: Michael Marti, P.E. SRF Consulting Group, Inc. Dan Wegman, P.E. SemMaterials

2 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)

3 Cutbacks Petroleum solvent (naphtha or kerosene) is added to base asphalt to make fluid Solvent then evaporates restoring asphalt’s binding properties Health and environmental concerns: –Flammable: Working temps of ºF –Hydrocarbon emissions into atmosphere Other concerns: expense, sensitive to bleeding

4 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

5 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 Asphalt particle size = 4  m Asphalt particle size = 4  m #200 sieve = 75  m #200 sieve = 75  m Grain of salt = 500  m Grain of salt = 500  m

6 Emulsifying agent Surface-active agent, or surfactant Keeps asphalt droplet in stable suspension Controls breaking time Determines classification Rapid SetRS Medium SetMS Slow SetSS 1 or 2, relative viscosity “h” indicates harder asphalt Cationic “C”, positively (+) charged Anionic, negatively (-) charged

7 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

8 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)

9 Modifiers High Floats Polymers Emulsion Grade ACHigh Float Residue

10 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

11 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)

12 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

13 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

14 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

15 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)

16 Handling Emulsions Use vertical tanks (less surface area) Keep warm (check with supplier) If over extended period, gently mix Do not store for extended periods of time Do not contaminate Do not store at high temperatures (>185ºF) Do not let freeze Don'ts Do’s

17 Handling Emulsions Heat slowly with indirect heat Agitate slowly while heating Follow supplier’s recommendations 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 Do’s

18 Handling Emulsions 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 Do not splash material when pumping Do not pump excessively Don'ts Do’s

19 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


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