Performance of Performance of Stone Matrix AsphaltStone Matrix Asphalt

Pavements Pavements in Marylandin Maryland

L. MichaelL. MichaelG. BurkeG. BurkeC. SchwartzC. Schwartz

AAPT 2003AAPT 2003Lexington, KYLexington, KY

Maryland’s First SMA 1992

First Superpave 1995

Since 1996 Maryland has

been designing SMA with SGC

1996 1997 1998 1999

2000 2001 2002

Since 1997 Maryland has been using PG Binders...

76-22 70-22 64-28

Ndesign 100VTM 4.0VMA 18.0External1.25Internal

1.16

GRADATION SPECIFICATION

0.075

0.15

0.3

0.6

1.18

2.36

4.75

9.5

12.5

19.0 mm100

82-88-60

20-28

14-20

9-11

12.5 mm100

90-9970-85

30-50

20-33

8-11

9.5 mm100

10070-90

30-50

20-30

8-13

19.0

COARSE AGGREGATEGap-Graded Mixes

TestProperty

LA Abrasion Loss,% Max.

Flat & ElongatedParticles, %

Retained on the #4 Sieve Max.

3:1

5:1

PV

Test Method

T96

D4791

---

---

MSMT 411

SpecificationLimits

30

---

20

5

8.5(d)

The Gap-Graded Specimen shall conform to the following

Hot MixAsphalt

Gap-Graded

Plant Control

VMA

18.0 Min.

17.0 Min.

VTM

4.0

±1.2

Ndes

100

AC

6.5 Min.

±0.4

Binder

70-22

Draindown% Max.

Stabilizer ByWeight of

Total Mix %

Specification

0.3

0.2 - 0.4

Plant Tolerance

0.3 Max.

±0.1

CHARACTERISTICSCHARACTERISTICS

Superpave SMASuperpave SMA

Rut ResistantRut Resistant

DurableDurable

Skid ResistantSkid Resistant

Reduced SprayReduced Spray

Reduced HydroplaningReduced Hydroplaning

Reduced SoundReduced Sound

DECISION POINTS FOR USING SMA DECISION POINTS FOR USING SMA

• 2000 ESAL’s per day

• 55 mph

• 2000 ESAL’s per day

• 55 mph

MD SMA LANE MILESMD SMA LANE MILES

NUMBER OF PROJECTS NUMBER OF PROJECTS BY MIX TYPEBY MIX TYPE

12.5 mm

19 mm

0

50

100

150

200

250

300

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 (%)

Fre

qu

en

cy

0

10

20

30

40

50

60

70

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 (%)

Fre

qu

en

cy

12.5 mm

19 mm

0

20

40

60

80

100

120

Air Voids (%)

Fre

qu

en

cy

010

20

30

40

50

60

7080

Air Voids (%)

Fre

qu

en

cy

12.5 mm

19 mm

0

50

100

150

200

250

15 16 17 18 19 20 21 22 23 24

VMA (%)

Fre

qu

en

cy

0

20

40

60

80

100

120

15 16 17 18 19 20 21 22 23 24 25 26

VMA (%)

Fre

qu

en

cy

12.5 mm

19 mm

y = 0.0082x + 0.0956

R2 = 0.0582

y = 0.0040x + 0.1054

R2 = 0.0664

0.00

0.05

0.10

0.15

0.20

0.25

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

y = 0.0082x + 0.0956

R2 = 0.0582

y = 0.0040x + 0.1054

R2 = 0.0664

0.00

0.05

0.10

0.15

0.20

0.25

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

RUTTING RUTTING PERFORMANCEPERFORMANCE

ROUGHNESS (IRI)ROUGHNESS (IRI)

y = -1.36x + 76.36

R2 = 0.01

y = 2.57x + 84.03

R2 = 0.04

0

50

100

150

200

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

y = -1.36x + 76.36

R2 = 0.01

y = 2.57x + 84.03

R2 = 0.04

0

50

100

150

200

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

FRICTIONFRICTION

y = -0.728x + 49.726

R2 = 0.025

y = 0.218x + 45.512

R2 = 0.005

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

y = -0.728x + 49.726

R2 = 0.025

y = 0.218x + 45.512

R2 = 0.005

20

30

40

50

60

70

0 1 2 3 4 5 6 7 8 9 10

Time Since Construction (years)

12.5 mm19 mm12.5 mm19 mm

CORRELATIONSAC AV VMA 0.075 mm 4.75 mm IRI/Year Rutting/Year Friction/Year

AC 1.00AV 0.29 1.00VMA 0.24 0.29 1.000.075 mm 0.06 0.18 -0.32 1.004.75 mm 0.10 -0.05 0.12 -0.31 1.00 IRI/Year -0.29 -0.09 0.24 -0.19 -0.09 1.00 Rutting/Year -0.23 -0.22 -0.17 -0.04 -0.52 0.51 1.00 Friction/Year -0.42 -0.47 -0.32 -0.08 -0.47 -0.12 0.14 1.00

12.5 mm

AC AV VMA 0.075 mm 4.75 mm IRI/Year Rutting/Year Friction/YearAC 1.00AV -0.01 1.00VMA 0.25 0.63 1.000.075 mm 0.10 0.28 0.15 1.004.75 mm -0.15 0.20 0.27 -0.09 1.00 IRI/Year -0.12 -0.06 0.04 0.05 0.08 1.00 Rutting/Year 0.20 -0.25 -0.01 -0.06 -0.18 0.09 1.00 Friction/Year -0.01 -0.04 0.11 -0.40 0.26 -0.30 0.20 1.00

19 mm

• SMALL RANGE OF PERFORMANCE

• SMALL RANGE OF MIX PROPERTIES

SUMMARYSUMMARY• 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)

SUMMARYSUMMARY

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

performance– Too little variation in mix properties

Many of the Maryland SMA sectionsMany of the Maryland SMA sectionslook better today than when firstlook better today than when first

opened to traffic!opened to traffic!

SMA looks good...

…Let’s use it!