Performance of Stone Matrix Asphalt Pavements in Maryland

Performance of Stone Matrix Asphalt Pavements in Maryland L. Michael G. Burke C. Schwartz AAPT 2003 Lexington, KY Marylands 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 100 VTM 4.0 VMA 18.0 External1.25 Interna 1.16 l GRADATION SPECIFICATION 19.0 mm 12.5 mm 100 100

9.5 mm 100 9.5 82-88 -60 90-99 70-85 100 70-90 4.75 20-28 30-50 30-50 2.36 14-20 20-33

20-30 9-11 8-11 8-13 19.0 12.5 1.18 0.6 0.3 0.15 0.075 COARSE AGGREGATE Gap-Graded Mixes Test Property Test Method Specification Limits LA Abrasion Loss,

% Max. T96 30 Flat & Elongated Particles, % Retained on the #4 Sieve Max. D4791 --- 3:1 --- 20 5:1 --- 5 PV

MSMT 411 8.5(d) 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 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 ESALs per day 55 mph MD SMA LANE MILES NUMBER OF PROJECTS BY MIX TYPE 12.5 mm 19 mm 300 12.5 mm 200 150 100

50 0 5.2 5.4 5.6 5.8 6.0 6.2 6.4 6.6 6.8 7.0 7.2 7.4 Asphalt Content (%) 70 60 Frequency Frequency 250 50 19 mm 40 30 20 10 0 5.7 5.8 5.9 6.0 6.1 6.2 6.3 6.4 6.5 6.6 6.7 6.8 6.9 7.0 7.1 Asphalt Content (%) 120

12.5 mm 80 60 40 20 0 Air Voids (%) Frequency Frequency 100 80 70 60 50 40 30 20 10 0 19 mm Air Voids (%)

250 12.5 mm 150 100 50 0 15 16 17 18 19 20 21 22 23 24

VMA (%) 120 100 Frequency Frequency 200 19 mm 80 60 40 20 0 15 16 17 18 19 20 21 22 23 24 25 26 VMA (%) RUTTING PERFORMANCE 0.25 0.25 y = 0.0082x + 0.0956 y = 0.0082x + 0.0956

2 R 2= 0.0582 R = 0.0582 0.20 0.20 0.15 0.15 y = 0.0040x + 0.1054 y = 0.0040x + 0.1054 2 R 2= 0.0664 R = 0.0664 0.10 0.10 12.5 12.5mm mm 19 mm 19 mm 12.5 12.5mm mm

19 mm 19 mm 0.05 0.05 0.00 0.00 00 11 22 33 44 55 66 77 Time TimeSince SinceConstruction

Construction(years) (years) 88 99 10 10 ROUGHNESS (IRI) 200 200 y = 2.57x + 84.03 y = 2.57x + 84.03 2 R 2= 0.04 R = 0.04 150 150 100 100 12.5 12.5mm

mm 19 mm 19 mm 12.5 12.5mm mm 19 mm 19 mm 50 50 y = -1.36x + 76.36 y = -1.36x + 76.36 2 R 2= 0.01 R = 0.01 00 00 11 22 33

44 55 66 77 Time TimeSince SinceConstruction Construction(years) (years) 88 99 10 10 FRICTION 70 70 12.5 12.5mm mm 19

mm 19 mm 12.5 12.5mm mm 19 mm 19 mm y = -0.728x + 49.726 y = -0.728x + 49.726 2 R 2= 0.025 R = 0.025 60 60 50 50 40 40 y = 0.218x + 45.512 y = 0.218x + 45.512 2

R 2= 0.005 R = 0.005 30 30 20 20 00 11 22 33 44 55 66 77 Time TimeSince SinceConstruction Construction(years)

(years) 88 99 10 10 CORRELATIONS AC AV VMA 0.075 mm 4.75 mm IRI/Year Rutting/Year Friction/Year AC 1.00 0.29 0.24 0.06 0.10 -0.29 -0.23 -0.42

AC AV VMA 0.075 mm 4.75 mm IRI/Year Rutting/Year Friction/Year AC 1.00 -0.01 0.25 0.10 -0.15 -0.12 0.20 -0.01 AV 1.00 0.29 0.18 -0.05 -0.09 -0.22 -0.47 AV 1.00

0.63 0.28 0.20 -0.06 -0.25 -0.04 VMA 0.075 mm 1.00 -0.32 0.12 0.24 -0.17 -0.32 IRI/Year Rutting/Year Friction/Year 12.5 mm 1.00 -0.31 -0.19 -0.04 -0.08

VMA 0.075 mm 1.00 0.15 0.27 0.04 -0.01 0.11 4.75 mm 1.00 -0.09 -0.52 -0.47 4.75 mm 1.00 0.51 -0.12 IRI/Year 1.00 0.14 Rutting/Year 1.00

Friction/Year 19 mm 1.00 -0.09 0.05 -0.06 -0.40 1.00 0.08 -0.18 0.26 1.00 0.09 -0.30 1.00 0.20 SMALL RANGE OF PERFORMANCE SMALL RANGE OF MIX PROPERTIES 1.00 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... Lets use it!