Performance of Stone Matrix Asphalt Pavements in Maryland

Maryland’s First SMA 1992 First Superpave 1995

Since 1996 Maryland has been designing SMA with SGC 2000 1996 2001 1997 2002

Since 1997 Maryland has been using PG Binders. . . 76 -22 70 -22

Ndesign VTM VMA External Internal 100 4. 0 18. 0 1. 25 1. 16

GRADATION SPECIFICATION 19. 0 mm 100 12. 5 mm 100 9. 5 mm 100

COARSE AGGREGATE Gap-Graded Mixes Test Property Test Method Specification Limits T 96 30 D

The Gap-Graded Specimen shall conform to the following VMA VTM Ndes AC Binder Hot

CHARACTERISTICS Superpave Rut Resistant Durable Skid Resistant Reduced Spray Reduced Hydroplaning Reduced Sound SMA

DECISION POINTS FOR USING SMA • 2000 ESAL’s per day • 55 mph

CORRELATIONS 12. 5 mm 19 mm • SMALL RANGE OF PERFORMANCE • SMALL RANGE

SUMMARY • Performance and material property data for 85 SMA projects – 1300 lane

SUMMARY • Inconclusive correlations between performance and mix properties – Too little variation/deterioration of

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Performance of Stone Matrix Asphalt Pavements in Maryland L. Michael G. Burke C. Schwartz AAPT 2003 Lexington, KY

Maryland’s First SMA 1992 First Superpave 1995

Since 1996 Maryland has been designing SMA with SGC 2000 1996 2001 1997 2002 1998 1999

Since 1997 Maryland has been using PG Binders. . . 76 -22 70 -22 64 -28

Ndesign VTM VMA External Internal 100 4. 0 18. 0 1. 25 1. 16

GRADATION SPECIFICATION 19. 0 mm 100 12. 5 mm 100 9. 5 mm 100 12. 5 82 -88 90 -99 100 9. 5 -60 70 -85 70 -90 4. 75 20 -28 30 -50 2. 36 14 -20 20 -33 20 -30 9 -11 8 -13 1. 18 0. 6 0. 3 0. 15 0. 075

COARSE AGGREGATE Gap-Graded Mixes Test Property Test Method Specification Limits T 96 30 D 4791 --- 3: 1 --- 20 5: 1 --- 5 PV MSMT 411 8. 5(d) LA Abrasion Loss, % Max. Flat & Elongated Particles, % Retained on the #4 Sieve Max.

The Gap-Graded Specimen shall conform to the following VMA VTM Ndes AC Binder Hot Mix Asphalt Gap-Graded 18. 0 Min. 4. 0 100 6. 5 Min. 70 -22 Plant Control 17. 0 Min. ± 1. 2 ± 0. 4 Specification Plant Tolerance Draindown % Max. 0. 3 Max. Stabilizer By Weight of Total Mix % 0. 2 - 0. 4 ± 0. 1

CHARACTERISTICS Superpave Rut Resistant Durable Skid Resistant Reduced Spray Reduced Hydroplaning Reduced Sound SMA

DECISION POINTS FOR USING SMA • 2000 ESAL’s per day • 55 mph

MD SMA LANE MILES

NUMBER OF PROJECTS BY MIX TYPE

12. 5 mm 19 mm

RUTTING PERFORMANCE

ROUGHNESS (IRI)

FRICTION

CORRELATIONS 12. 5 mm 19 mm • SMALL RANGE OF PERFORMANCE • SMALL RANGE OF MIX PROPERTIES

SUMMARY • Performance and material property data for 85 SMA projects – 1300 lane miles – Up to 10 years service life – Primarily 19 and 12. 5 mm SMA mixes • Excellent performance: – Rutting: 0. 04 inches/year ( avg) – Roughness (IRI): 3. 2 in/mile-year ( avg) – Friction (FN): 1. 3/year ( avg)

SUMMARY • Inconclusive correlations between performance and mix properties – Too little variation/deterioration of performance – Too little variation in mix properties Many of the Maryland SMA sections look better today than when first opened to traffic!

SMA looks good. . . …Let’s use it!