Asphalt Concrete Mix Design and Construction

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Asphalt Concrete Mix Design and Construction
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Hot Mix Asphalt Concrete (HMA)Mix Designs

• Objective
• Develop an economical blend of aggregates and
  asphalt that meet design requirements
• Historical mix design methods
• Marshall
• Hveem
• New
• Superpave gyratory

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Requirements in Common

• Sufficient asphalt to ensure a durable pavement
• Sufficient stability under traffic loads
• Sufficient air voids
• Upper limit to prevent excessive environmental
  damage
• Lower limit to allow room for initial
  densification due to traffic
• Sufficient workability

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Mixing
Place pre-heated aggregate in bowl and add hot
asphalt
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Mixing
Place bowl on mixer and mix until aggregate is
well-coated
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Compaction
Example of typical full-size compactors.
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Selection of Design Asphalt Binder Content
VMA
binder
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HMA PLANT OPERATION
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Types Of Plants
BATCH
DRUM MIXER
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Basic Purpose Of HMA Plants

• To produce a quality hot asphalt mixture that
  contains the desired proportions of asphalt and
  aggregate and meets all specifications.

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Batch planttypical layout
Asphalt Storage
Conveyor Belt
Aggregate Bins
Batch Tower
Dryer
Burner
Hot elevator
Storage Silo
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Batch Plant
Batch Tower
Pug Mill
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Burner - Batch Plant
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Drum Mixer Planttypical layout
Asphalt Storage
Conveyor Belts
Aggregate Bins
Dryer
Burner
Storage Silo
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Drum Dryer Mixer
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Temperature Profile in Drum Mixer
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Dryer For Drum Dryer Mix Plant
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Dryer For A Drum Mixer Plant
Aggregate Entry Point
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Small Drum Mixer Plant
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Plants are computer controlled
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HMA PLACEMENT
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To Be Covered

• Hauling
• Placement
• Compaction

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Different types of trucks are Used
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Self Propelled Paver
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Self Propelled Paving Machine
THE BASIC PRINCIPLE HAS NOT CHANGED MUCH
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Self Propelled Paving Machine
HMA Flow
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COMPACTION
GOOD COMPACTION LEADS TO GOOD PERFORMANCE
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Reason For Compaction

• To prevent further compaction
• To provide shear strength or resistance to
  rutting
• To ensure the mixture is waterproof
• To prevent excessive oxidation of the asphalt
  binder

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Temperature is critical
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Vibratory Roller
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Pnuematic Roller
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Steel Wheeled Roller
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Extracting A Core
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Questions - ?