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1 Asphalt Concrete Mix Design and Construction Slide 2 2 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 Slide 3 3 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 Slide 4 4 Place pre-heated aggregate in bowl and add hot asphalt Mixing Slide 5 5 Place bowl on mixer and mix until aggregate is well-coated Slide 6 6 Example of typical full-size compactors. Compaction Slide 7 7 % binder VMA % binder VFA % binder %G mm at N ini % binder %G mm at N max % binder DP % binder VaVa Blend 3 Selection of Design Asphalt Binder Content Slide 8 HMA PLANT OPERATION Slide 9 Types Of Plants BATCHDRUM MIXER Slide 10 10 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. Slide 11 Batch plant typical layout Storage Silo Batch Tower Dryer Conveyor Belt Aggregate Bins Burner Asphalt Storage Hot elevator Slide 12 12 Batch Plant Batch Tower Pug Mill Slide 13 13 Burner - Batch Plant Slide 14 Drum Mixer Plant typical layout Storage Silo Dryer Conveyor Belts Aggregate Bins Burner Asphalt Storage Slide 15 Drum Dryer Mixer Slide 16 16 Temperature Profile in Drum Mixer Slide 17 Dryer For Drum Dryer Mix Plant Slide 18 Dryer For A Drum Mixer Plant Aggregate Entry Point Slide 19 Small Drum Mixer Plant Slide 20 20 Plants are computer controlled Slide 21 HMA PLACEMENT Slide 22 22 To Be Covered Hauling Placement Compaction Slide 23 23 Different types of trucks are Used Slide 24 24 Self Propelled Paver Slide 25 25 Self Propelled Paving Machine THE BASIC PRINCIPLE HAS NOT CHANGED MUCH Slide 26 26 Self Propelled Paving Machine HMA Flow Slide 27 27 COMPACTION GOOD COMPACTION LEADS TO GOOD PERFORMANCE Slide 28 28 Reason For Compaction To prevent further compaction To prevent further compaction To provide shear strength or resistance to rutting To provide shear strength or resistance to rutting To ensure the mixture is waterproof To ensure the mixture is waterproof To prevent excessive oxidation of the asphalt binder To prevent excessive oxidation of the asphalt binder Slide 29 29 Temperature is critical Slide 30 30 Vibratory Roller Slide 31 31 Pnuematic Roller Slide 32 32 Steel Wheeled Roller Slide 33 33 Extracting A Core Slide 34 34 Questions - ?