Introduction%20to%20Foamed%20Asphalt

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Introduction to Foamed Asphalt
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How is Foamed Asphalt Produced?

• Source material for foamed asphalt is ordinary
  hot asphalt cement (AC-5 or PG 52-28).
• Foam is produced using hot asphalt with a
  temperature between 325 to 340 F and a
  precisely defined amount of water (2.5 by weight
  of asphalt).
• When the water comes in contact with the hot
  asphalt it evaporates explosively, causing the
  asphalt to Foam.
• The asphalt expands up to 15 of its original
  volume.
• When foamed, the asphalt has a very large surface
  area making it ideal for mixing with aggregates.

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Expansion Chamber

• Cold water and air are injected simultaneously
  into the hot asphalt.
• The hot asphalt foams explosively and shoots down
  into the mixing chamber.

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Mixing Chamber Diagram
Hot Asphalt
Water For Foam Generation
Compaction Water
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Foamed Asphalt Recycled Material

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3 Asphalt Binder by Weight of Recycled Material
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Foamed Asphalt Work Done in Alaska

• Kenai Peninsula Paving Program 2001
• East Hill Road and West Hill Road, Homer
• Project Staff Bob Lundell, PE, Project Manager
• Gary Walklin, PE, Project Engineer
• Paul Dougherty, Grade Inspector
• Contractor Alaska Road Builders
• Eric Uppick with Wirtgen Group

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Project Location Homer, Alaska
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Mix Design

• Mix design was done by Wirtgen and Loudon
  Partners
• East Hill Road 2.5 0.3 Foamed Asphalt and
• 1 Portland cement by mass of material
• West Hill Road 3.0 0.3 Foamed Asphalt and
• 1 Portland cement by mass of material
• 1 Portland cement was added to increase the
  percentage passing the No. 200 sieve, which is
  critical for proper dispersion of the foamed
  asphalt.

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Mix Design

• Fines are critical for proper dispersion of the
  foamed asphalt.

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Wirtgen WR 2500
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Compaction Water
Hot Asphalt
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Initial Compaction
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Initial Compaction and Grading
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Final Grading and Compaction
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Final Compaction
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One Day After Foam Treatment
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Paving
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Final Driving Surface
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Advantages of Foamed Asphalt

• Allows the use of unsuitable base material (6 to
  20 passing the No. 200 sieve).
• Eliminates the need and expense of removing
  unsuitable bases.
• Can be opened to traffic immediately after
  compaction.
• Increased strength

Material Design Resilient Modulus (Ksi)
Foamed Asphalt Treated Base Crushed Asphalt Base Crushed Aggregate Base Coarse 110 80 40-50