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Compaction of Hot Mix Asphalt
Pavements (HMA)
Ed Lyon, PE, GE April 9, 2014
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in a...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Quality Characteristics Affected by Compaction
– Stability /...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in a...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
• “Compaction is the process by which the
volume of air in a...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
– Fatigue Resistance “A reduction in air voids from 8% to 3%...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Negative Effects of Excess
Compaction
Balance -
For dense-gr...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Aggregate Gradation
Aggregate Gradation
– Gradation has a di...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Aggregate Gradtaion – VMA
VMA – Voids in Mineral Aggregate
–...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Relative Compaction
How are common practices set up to ensur...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Common Practice – Specifying
Relative Compaction
LAB TEST MA...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
LTMD - Marshall Method
• Mechanically Compacts Briquettes in...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
LTMD California Kneading Compactor
Hveem Method
• Mechanical...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Common Practice – Specifying
Relative Compaction
Theoretical...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Theoretical Maximum Specific
Gravity - Rice
• Measures the s...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Gyratory Compactor
Super Pave Method
• Mechanically Compacts...
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
YOUR QUESTIONS
Thank you for your attention.
Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014
Hamburg Wheel Tracking Device
Super Pave Method
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Ed Lyon - HMA Compaction

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Presentation delivered at the CalAPA Spring Asphalt Pavement Conference April 9-10, 2014 in Ontario. Topic: The critical role compaction plays in the HMA construction process, plus methods and standards of measurement and problems to be avoided.

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Ed Lyon - HMA Compaction

  1. 1. Compaction of Hot Mix Asphalt Pavements (HMA) Ed Lyon, PE, GE April 9, 2014
  2. 2. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 • “Compaction is the process by which the volume of air in an HMA mixture is reduced by using external forces to reorient the constituent aggregate particles into a more closely spaced arrangement. This reduction of air volume in a mixture produces a corresponding increase in HMA unit weight, or density (Roberts et al., 1996). “ Compaction – Defined
  3. 3. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Quality Characteristics Affected by Compaction – Stability / Strength – Fatigue Life – Durability – Moisture Sensitivity – Raveling Importance of Compaction
  4. 4. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 • “Compaction is the process by which the volume of air in an HMA mixture is reduced by using external forces to reorient the constituent aggregate particles into a more closely spaced arrangement. This reduction of air volume in a mixture produces a corresponding increase in HMA unit weight, or density (Roberts et al., 1996). “ Compaction – Defined
  5. 5. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 • “Compaction is the process by which the volume of air in an HMA mixture is reduced by using external forces to reorient the constituent aggregate particles into a more closely spaced arrangement. This reduction of air volume in a mixture produces a corresponding increase in HMA unit weight, or density (Roberts et al., 1996). “ Compaction – Defined The volume of air in an HMA pavement is important because it has a profound effect on long-term pavement performance.
  6. 6. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 – Fatigue Resistance “A reduction in air voids from 8% to 3% could more than double pavement fatigue life” (Scherocman, 1984a). – Durability “compacting a well-designed paving mixture to low air voids retards the rate of hardening of the asphalt binder, and results in longer pavement life, lower pavement maintenance, and better all-around pavement performance.” McLeod (1967) – Raveling. Kandhal and Koehler (1984) found that raveling becomes a significant problem above 8% air voids and becomes a severe problem above 15% air voids. Positive Effect of Compaction – Moisture Damage. “Air voids in insufficiently compacted HMA are high and tend to be interconnected with each other. Numerous and interconnected air voids allow for easy water entry which increases the likelihood of significant moisture damage.” (Kandhal and Koehler, 1984; Cooley et al., 2002)
  7. 7. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Negative Effects of Excess Compaction Balance - For dense-graded HMA, for use on high traffic pavements in place air voids between 3 and 8 percent generally produce the best compromise of pavement strength, fatigue life, durability, raveling, rutting and moisture damage susceptibility. – Decreased Stability and Strength. Kennedy et al. (1984) concluded that tensile strength, static and resilient moduli, and stability are reduced at low air void content. – Rutting. The amount of rutting which occurs in an asphalt pavement is inversely proportional to the air void content (Scherocman, 1984a)
  8. 8. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Aggregate Gradation Aggregate Gradation – Gradation has a direct affect on the effort required to properly compact a pavement Fuller’s maximum density line:Passing (%) = (d/D)n ; n = 0,45 (FHWA)
  9. 9. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Aggregate Gradtaion – VMA VMA – Voids in Mineral Aggregate – The volume of the intergranular void space between the aggregate particles of a compacted paving mixture that includes the air voids and the effective binder content AASHTO R-35 HIGH VMA = High Voids, harsh or stiff mix • High stability • Difficult to compact LOW VMA = Low Voids, densely graded mix • Lower stability • Easier to compact
  10. 10. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Relative Compaction How are common practices set up to ensure that the finished pavements have in place air voids between 3 and 8 percent ? Relative compaction is the ratio expressed as a percentage between the field in place density and a laboratory test standard. Relative to What Standard ?
  11. 11. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Common Practice – Specifying Relative Compaction LAB TEST MAXIMUM DENSITY (LTMD) • Specified Air Voids in the lab between 3% and 5% • Compacted Briquette ÷ Theoretical Max SpG • Specified Relative Compaction 95% to 96% of LTMD • Field Density ÷ Compacted Briquette In Place Air is equal to the sum of the air voids in the lab and air voids from the field relative compaction tests Example: 3.5% Air Voids in the lab, 96.4% Compaction In Place Air = 3.5% + 100% – 96.4% = 7.1 %
  12. 12. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 LTMD - Marshall Method • Mechanically Compacts Briquettes in steel molds using the Impact from the Marshall Hammer. • Mix Design based on optimum asphalt content that yields air voids in the compacted briquettes of 4% when comparing briquette density to Rice Theoretical Density The density of the compacted briquette is used as the specified Lab Test Maximum Density (LTMD ) for comparison to determine the relative compaction
  13. 13. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 LTMD California Kneading Compactor Hveem Method • Mechanically Compacts Briquettes in steel molds using the California Kneading Compactor. • Mix Design based on optimum asphalt content that yields air voids in the compacted briquettes between of 4% when comparing briquette density to Rice Theoretical Density The density of the compacted briquette is used as the specified Lab Test Maximum Density (LTMD ) for comparison to determine the relative compaction
  14. 14. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Common Practice – Specifying Relative Compaction Theoretical Maximum Specific Gravity: – Specify a minimum in place relative compaction equal to 92% of the Theoretical Maximum Specific Gravity, commonly referred to as the Rice Test – Field Tests are performed by Nuclear Gauge or Cores – % Relative Compaction is the ratio expressed as a percentage between the in place density of the compacted pavement and the Rice maximum specific gravity. Agencies May specify a maximum in place relative compaction on the order of 96 to 97% to preserve stability in areas of heavy traffic
  15. 15. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Theoretical Maximum Specific Gravity - Rice • Measures the specific gravity of a loose mixture of the HMA after all of the air in the mix has been removed under vacuum. • Used in all mix design methods to select the design asphalt content that yields air voids in compacted briquettes between 3 and 5%
  16. 16. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Gyratory Compactor Super Pave Method • Mechanically Compacts Briquettes in larger steel molds using the Gyratory Compactor. • Mix Design based on optimum asphalt content that yields air voids in the compacted briquettes of 4% when comparing briquette density to Rice Theoretical Density. • Specifies a Minimum VMA – stiffer mixes Theoretical Maximum Specific Gravity (Rice) test used for comparison to field density to determine the relative compaction
  17. 17. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 YOUR QUESTIONS Thank you for your attention.
  18. 18. Compaction of HMA Pavements | Ed Lyon, PE, GE | April 9, 2014 Hamburg Wheel Tracking Device Super Pave Method

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