asphalt rubber mixture design adot’s ar-acfc and arac
TRANSCRIPT
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Asphalt Rubber Mixture Design
ADOT’s AR-ACFC and ARAC
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AR-ACFC
Mix Design Considerations
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AR-ACFC: Purpose
• Final wearing surface
• Typically nominal 1/2 inch lift
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AR-ACFC: Aggregate
• Gradation
• Flakiness
• Sand Equivalent
• Crushed Faces
• Abrasion
• Percent Carbonates
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AR-ACFC: Gradation
Sieve Size Percent PassingWithout admixture
3/8” 100
#4 30-45
#8 4-8
#200 0-2.5
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AR-ACFC: Mineral Admixture
1% Lime or Cement is mandatory
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AR-ACFC: Flakiness
• Maximum Flakiness = 25
• To insure good particle shape, and minimize particle breakage.
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AR-ACFC: Sand Equivalent
• Minimum 55
• To insure that there are not excessive amounts of clay in the aggregate
• Done on washed aggregate
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AR-ACFC: Crushed Faces
• Minimum 95% Single Crushed Faces
• To insure good particle interlock and good frictional characteristics
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AR-ACFC: Abrasion
• Maximum at 100 rev. 9 at 500 rev. 40
• To insure that the aggregate will hold up to the wear and tear of traffic
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AR-ACFC: Percent Carbonates
• Maximum 30%
• To minimize the amount of limestone which has a tendency to polish under traffic.
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AR-ACFC: Mix Design Steps
• Prepare Aggregate
• Determine aggregate specific gravities
• Determine maximum theoretical specific gravity
• Check draindown
• Determine mix density
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AR-ACFC: Design
• Determine aggregate specific gravities for fine and coarse mineral aggregate
• Calculate combined specific gravities (oven dry, saturated surface dry, apparent)
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AR-ACFC: Design
• Determine the maximum theoretical specific gravity (Rice test)
• Done at 3.5 to 4.0% binder content
• Determine the amount of asphalt absorption.
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AR-ACFC: Design
• Calculate Binder content:
((.38)(W) + 8.6)(2.620/C)= Binder content
W=% water absorption
C=combined oven dry specific gravity
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AR-ACFC: Design
• Check Draindown using the Schellenberg test
This test is performed in the laboratory in order to determine whether or not an
unacceptable amount of binder drains down from the mix.
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AR-ACFC: Design
1. Place Mix in a beaker
2. Place beaker in oven for 1 hour
3. Empty beaker
4. Determine % mass loss
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AR-ACFC: Design
Based on the results of the draindown test, adjust binder content if necessary
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AR-ACFC: Design
• Determine mix density– Compact in Forney (4” diameter, 200 psi)
– Determine density by volumetrics
• Information used for determining spread, may also calculate voids for information only
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AR-ACFC: Typical Design
• Typically 2 stockpiles: 95% intermediates, 5% fines
• Typical binder content 9.2-9.3% (general range 8.7-9.7%)
• Over PCC add 1% to design binder content
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ARAC
Mix Design Considerations
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ARAC: Purpose
• Highly flexible lift
• High quality structural lift
• Typically nominal 2 inch lift
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ARAC: Aggregate
• Gradation
• Sand Equivalent
• Crushed Faces
• Abrasion
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ARAC: Gradation
Sieve Size Percent PassingWithout admixture
¾” 100½” 80-1003/8” 65-80#4 28-42#8 14-22
#200 0-2.5
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ARAC: Mineral Admixture
1% Lime or Cement is mandatory
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ARAC: Sand Equivalent
• Minimum SE=55
• To ensure that there are not excessive amounts of clay particles on the aggregate
• Done on washed aggregate
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ARAC: Crushed Faces
• Minimum 95% Single Crushed Faces
• To insure good particle interlock
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ARAC: Abrasion
• Maximum at 100 rev. 9 at 500 rev. 40
• To insure that the aggregate will hold up to the wear and tear of traffic
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ARAC: Mix Design Steps
• Prepare Aggregate
• Determine aggregate specific gravities
• Determine maximum theoretical specific gravity
• Compact mix, determine optimum binder content
• Check mix volumterics
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ARAC: Design
• Determine aggregate specific gravities for fine and coarse mineral aggregate
• Calculate combined specific gravities (oven dry, saturated surface dry, apparent)
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ARAC: Design
• Determine the maximum theoretical specific gravity (Rice test)
• Done at 6.0% binder content and calculated to other binder contents as needed
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ARAC: Design
• Compact with Marshall hammer at three binder contents
• Typically 6.5, 7.5, 8.5 or 6.0, 7.0, 8.0 depending on aggregate source
• Mix/Compact at 325°F
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ARAC: Design
• Check Volumetrics, select optimum binder content.
• Minimum VMA 19.0%
• Effective Voids 4.0 - 6.0%
• Maximum 1% binder absorption
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ARAC: Design
• Watch to make sure that the VMA is not being created by the binder
• Typically when VMA is being created by the binder, voids will drop
• VMA/Voids are very interrelated for this mix type
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ARAC: Design
If necessary, adjust gradation to improve VMA or voids. Repeat compaction process
and remeasure maximum theoretical specific gravity.
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ARAC: Typical Design
Typical binder content 6.5-8.5% depending on aggregate source and gradation
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Thank you