ncat pavement test track - rocky mountain asphalt ... · minimum’’faa ... >3.0 100 45 40 45...
TRANSCRIPT
Thin Li' Mixes
Outline
• “Thin Li.s” defined
• Advantages & Disadvantages of 4.75 mm mixes
• 4.75 mm NMAS mix design
• ConstrucGon with 4.75 mm mixes
• Performance
What is a Thin Li.?• Compacted thickness ≤ 1 ¼” (32 mm)
• Using rule of min. thickness = 3x NMAS– 3 x 9.5 mm = 28.5 mm
– 3 x 4.75 mm = 14.25 mm (0.56”)
• ApplicaGons: – Surface layers for low volume roads
– Overlays
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Design ESALs(millions)
Ni Nd Nm Typical Applications
<0.3 6 50 75 Local roads with very light traffic volumes
0.3 to <3 7 75 115 Collector roads, medium trafficked city streets & county roads
3 to 30* 8 100 160 Many two-lane, multilane, & partially or completely controlled access roadways. Medium to heavy traffic city streets, state routes, US highways, and some rural Interstates
>30 9 125 205 Majority of Interstate system…
Current Superpave Ndesign Table
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Current 4.75 mm Mix Design Criteria
Design ESALs (Millions) Ndes
Minimum FAA Depth from SurfaceMinimum FAA
Depth from Surface Minimum Sand
EquivalentMin.VMA VFA % Gmm @ Nini
Design ESALs (Millions) Ndes ≤ 100 mm ≥ 100 mm
Minimum Sand
EquivalentMin.VMA VFA % Gmm @ Nini
<0.3 50 -‐ -‐ 40 16.0 70-‐80% ≤91.50.3 to <3.0 75 40 40 40 16.0 65-‐78% ≤90.5
>3.0 100 45 40 45 16.0 75-‐78% ≤89.0
Sieve size Min. Max. Air voids = 4.0%Air voids = 4.0%Air voids = 4.0%Air voids = 4.0%Air voids = 4.0%12.5 mm 100 Dust-‐to-‐Binder RaDo: 0.9 to 2.0Dust-‐to-‐Binder RaDo: 0.9 to 2.0Dust-‐to-‐Binder RaDo: 0.9 to 2.0Dust-‐to-‐Binder RaDo: 0.9 to 2.0Dust-‐to-‐Binder RaDo: 0.9 to 2.09.5 mm 95 100 4.75 mm 90 100 1.18 mm 30 60 0.075 mm 6 12
Disadvantages of 4.75 mm Mixes• High asphalt contents, not economical
• Low fricGonal resistance due to low surface texture
• Greater potenGal for permanent deformaGon
Advantages of 4.75 mm Mixes• Thin li.s, covers a lot of area
• Good use of surplus fine aggregates
• Can be feathered and used in wedge applicaGons
• Good workability with hand tools
• Excellent smoothness
• PracGcally impermeable
Par<cipa<ng States in Pooled Fund Project to Refine 4.75 mm Mix Design Criteria
Participating States
Baseline Mixes
4.75 mm Research Plan
• Obtained materials from each sponsor agency
• Designed mixes with 4.0 to 6.0% air voids and Ndesign using 50 and 75 gyraGons
• Evaluated resistance to rueng, moisture damage, and cracking.
Phase 1
Design Mixes13 Aggregate Blends
4 & 6% Air Voids50 & 75 Gyrations
Fractional Experimental Design
Obtain Field ProducedBaseline Mixes
Rutting Test using MVT
Permeability Test ASTM PS 129
Stripping Test AASHTO T283
Aging Test using FE Ratio
Start
Draft Phase 1 Report
Analysis
Refine Criteria for 4.75 mm Mixtures
Performance Testing
Phase 2Four Field Projects
Design Mixes as Needed
Rutting Test using MVT
Permeability Test ASTM PS 129
In-PlaceDensity
Start
Draft Final Report
Analysis
Validate Criteria for 4.75 mm Mixtures
Document Production & ConstructionTest AC Content, Gradation, Gmb, Gmm, Dynamic Friction, CT Meter Obtain Cores
Conclusions & RecommendaGons• Most mix gradaGons were very fine, had high asphalt contents, VMA and VFA
• Rueng resistance can be improved by reducing asphalt contents without sacrificing durability
• Other changes to improve rueng resistance:– Avoid very fine gradaGons
– Limit natural sand to 15%, Use FAA > 40 even for low traffic category, > 45 for med. traffic category
– Increase min. D/A raGo
– Use min. & max. Vbe rather than VMA & VFA
Other Ways to Improve 4.75 mm Mixes
• Use polymer modified binder for improved rueng resistance
• Use RAP or RAS for improving rueng resistance and mix economics
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Recommended 4.75 mm Mix Design Criteria
Range (Millions) Ndes
Minimum FAA
Minimum Sand Equivalent
Minimum Vbe
Maximum Vbe %Gmm@Nini
Dust-‐to-‐ Binder RaCo
<0.3 50 40 40 12.0 15.0 ≤91.5 1.0 to 2.00.3 to ≤ 3.0 75 45 45 12.0 15.0 ≤90.5 1.0 to 2.03.0 to ≤ 30 100 45 45 11.5 13.5 ≤89.0 1.5 to 2.0
GradaGon LimitsSieve Size Max. Min. Design Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 Percent12.5 mm -‐-‐-‐ 100
Design Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 Percent
9.5 mm 100 95
4.75 mm 100 90
1.18 mm 30 55
0.075 mm 13 6
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Recommended 4.75 mm Mix Design Criteria
Range (Millions) Ndes
Minimum FAA
Minimum Sand Equivalent
Minimum VMA
VFARange %Gmm@Nini
Dust-‐to-‐ Binder RaCo
<0.3 50 40 40 16.0 67 to 79 ≤91.5 1.0 to 2.00.3 to ≤ 3.0 75 45 45 16.0 66 to 77 ≤90.5 1.0 to 2.03.0 to ≤ 30 100 45 45 16.0 66 to 77 ≤89.0 1.5 to 2.0
GradaGon LimitsSieve Size Max. Min. Design Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 Percent12.5 mm -‐-‐-‐ 100
Design Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 PercentDesign Air Void Range= 4.0 to 6.0 Percent
9.5 mm 100 95
4.75 mm 100 90
1.18 mm 30 55
0.075 mm 13 6
ConstrucGon
• No in-‐place density requirement for li.s < 1”– Use “standard” roller papern
– Need ≥ 90% of Gmm in-‐place
• Fast paving rate is typical, take care not to out run the rollers
• Rubber Gre rollers are recommended
• Thin li.s will cool very fast, WMA will help in cool weather paving
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Permeability
4.75 mm on NCAT Test Track
• Mississippi DOT
• ¾” mill & overlay in 2006
• Gravel screenings, limestone screenings, sand and PG 76-‐22
• Carried 27 million ESALs to date
• 7 mm rueng
• No cracking or raveling
Example Cost per Ton & Square Yard
9.5 mm NMAS @ 1 ¼”
• AC: 6.0% x $500/ton = $30.00• Agg.: 94% x $12/ton = $11.28
• Total Mix: = $41.28
• 144 lb/.3
• 135.3 lb/yd2
• 1 ton covers 14.8 sq. yards
• $2.79/yd2
4.75 mm NMAS @ ¾”
• AC: 6.5% x $500/ton = $32.50• Agg.: 93.5% x $12/ton = $11.22
• Total Mix: = $43.72
• 138.4 lb/.3
• 76.1 lb/yd2
• 1 ton covers 26.3 sq. yards
• $1.66/yd2
www.NCAT.us