Stone Matrix Asphalt (SMA) for Airfield Pavements 2010 FAA Worldwide Airport Technology Transfer...

Stone Matrix Asphalt (SMA) for Airfield Pavements

2010 FAA Worldwide Airport Technology Transfer Conference

Brian ProwellDon WatsonGraham HurleyRay Brown

Acknowledgements• This work was conducted as part of the

Airfield Asphalt Pavement Technology Program Project 04-04, Evaluation of Stone Matrix Asphalt for Airfield Pavements.

Background

• SMA designed in Germany in the 1960’s as mix resistant to studded tires

• Adopted in US in 1991

Gradation

0

10

20

30

40

50

60

70

80

90

100

Sieve Size, mm

Pe

rce

nt

Pa

ss

ing

, %

Superpave SMA Superpave Control Points

0.075 0.60 1.18 2.36 4.75 9.5 12.5 19.0

Aggregate SkeletonStone Matrix Asphalt Mix

Aggregate SkeletonDense-Graded Mix

9.5 mm NMAS SMA Surface Texture

How is SMA Different?

• Gradation• Asphalt Content• Dust Content• Stabilizing Additives

• Marshall- 50 blow design has been used• Improved performance over HMA

SMA Performance in the USA

Objectives of AAPTP 04-04 Study

The objectives:• Evaluate performance of SMA

pavements• develop technical guidance for the FAA

to implement SMA on U.S. airfields

Documented SMA Use on Airfields

• Australia• China• Europe

• Belgium• Germany• Italy• Norway

• United States

Experimental Design

Mix Combinations

Coarse Aggregate

Binder Grade

P40175-

Blow

SMA50-

Blow

SMA50

Gyrations

SMA65

Gyrations

SMA80

Gyrations

SMA100

Gyrations

Diabase 76-22 X X X X X X

Granite 76-22 X X X X X X

Gravel 76-22 X X X X X X

Limestone 76-22 X X X X X X

Limestone 64-22 X X X

Granite 76-22 X X X X X X

Rutting Susceptibility

• Laboratory evaluations typically show SMA to have increased rutting susceptibility compared to HMA

• Experiments to compare SMA and P401

• Three tests: stability and flow, repeated-load creep, and Hamburg wheel-tracking

Stability and Flow

AggregateHigh PG

SMA P4014% Air Voids 3.5% Air Voids

AC%Stability

lbsFlow 0.01 in AC%

Stability lbs

Flow 0.01 in

Diabase 76 7.5 NA  NA  5.1 4,846 11Granite 1 76 5.9 2,828 23 5.3 5,190 13Granite 2 76 7.3 1,798 21 5.3 4,720 11Gravel 76 7.6 1,808 29 5.4 3,799 11Limestone 76 6.9 1,477 24 5.4 3,940 12Granite 1 64 NA NA NA 5.3 4,200 11Limestone 64 NA NA NA 5.5 3,111 8Average 76 7.0 1,978 24 5.3 4,499 12Average 64 NA NA NA 5.4 3,656 10

Repeated Load Permanent Deformation to Asses Rutting Potential

• 100 mm diameter, 150 mm height• 6% air voids• 58 C (climatic high temp. - 6 C )• 20 psi confinement• 0.1 second load; 0.9 second rest• 100, 200, 350 psi vertical load• Continue for 10,000 cycles or until tertiary

flow

With the repeated load test the permanent deformation

performance of SMA mixtures and P401 mixtures were not significantly different.

Hamburg TestTest combines rutting performance with moisture

susceptibility• Uses a steel wheel 47 mm wide by 204 mm

diameter• Load = 685 N (154 lb)• Full test is 20,000 cycles• Temperature - 50 C• VTM - 6 + 0.5 %• Tested under water

With Hamburg, rutting very similar for P-401 and SMA

Overlay Tester Results

0

2,000

4,000

6,000

8,000

10,000

12,000

14,000

16,000

18,000

Diabase Columbus Granite

Ruby Granite Gravel Limestone PG 67-22

Limestone PG 76-22

Cycl

es to

Fai

lure

SMA P401

847%

412%

24%

258%

736%

35%

Fuel Resistance• China has reported that SMA improves

fuel resistance• AAPTP 05-02 evaluating fuel resistant

sealers and binders• Citgo Fuel Resistance Test

– Soaked in kerosene for 24 hours– Mass loss less than 5% good

Fuel ResistanceAggregate Mix Mass Loss, %

GraniteP401 7.8

SMA 4.5

GravelP401 11.6

SMA 6.6

Deicer ResistanceImmersion Tensile Test

0

200

400

600

800

1000

1200

1400

Granite P401 Granite SMA Gravel P401 Gravel SMA

Tens

ile S

tren

gth,

kPa

Dry Water 2% Potassium Acetate

98% 96%

101%

108%

Two Case Studies

• Aviano AFB, Italy• Spangdahlem AFB, Germany

Aviano SMA

• Constructed in 1999• Provided good

performance up through 2010

• Some water issues• More rubber build up• No grooving

Rubber Build Up on SMA Aviano Air Force Base 2000

Aviano Surface Texture in 2000

Seepage of Water from Underneath, Aviano 2000

Draindown, Aviano 2000

Aviano, 2006

Aviano 2008

SMA Aviano

• Provided good performance to date• Good friction• Some water issues• No grooves

Based on good performance at Aviano, SMA was used at

Spangdahlem in 2007

Spangdahlem AFB

• Milled and overlaid with SMA in 2007• High density obtained• Some water vapor (blisters) problems

Spangdahlem 2006, patch

Spangdahlem 2006, cracking and condition of grooves

After mixture was milled, approximately 2 weeks of rainfall occurred causing the asphalt mixture to become soaked with

moisture

Construction in 2007

• The contractor used two asphalt plants, two pavers, and up to 8 rollers

• In place air voids were typically 3 to 4 percent

Spangdahlem, 2007, moisture on surface of SMA

Spangdahlem, 2007, blisters caused by water vapor

Plans are underway to remove and replace the SMA at

Spangdahlem

Summary of SMA / P401 Comparison

Property Performance worse than

P401

Performance similar to

P401

Performance better than

P401Permanent Deformation X1 X2

Moisture Damage XCracking XFuel Resistance XDeicer Resistance XTexture X2

1Based on laboratory tests performed as part of this study.2Based on review of the literature or in-service performance.

Recommendations

• SMA could cost 82 to 94 percent more than dense-graded mixes and still be cost effective on a life-cycle basis.

• SMA is not typically suited to small quantity production

• 65 gyrations recommended as alternative to 50-blow Marshall

The complete report is available at: www.AAPTP.US

Contact Information for authors:Ray Brown ray.brown@usace.army.mil

Brian Prowell Brian.AMSLLC@Charterinternet.com

Don Watson Watsode@auburn.edu

Graham Hurley Graham.AMSLLC@Charterinternet.com

Questions?