SMA South of the Border

1
SMA South of the Border

• Alexander (Sandy) Brown, P.Eng.
• Technical Director, Ontario Hot Mix Producers
  Association
• Canadian Regional Engineer, Asphalt Institute

www.ohmpa.org
Were Driven www.asphaltinstitute.org
2
Use of SMA in the United States

• Used routinely as surface by 28 states in 2007
  and a few more since
• Used primarily in states where there is a ready
  source of good aggregate
• SMA requires higher quality aggregate to resist
  polishing and resist crushing from stone on stone
  contact
• Haul distance is critical to the use
• States without adequate local aggregate have
  tried SMA with limited success
• Some use of slag aggregates

3
Wisconsin Highway Research Program

• Study concluded in early 2007 on HMA surface
  types to look at SMA vs. dense graded mixes using
  FHWA RealCost 2.1 (Harold Von Quintas)
• 45 years life with 5 discount rate
• Concluded that there was a LCCA advantage for SMA
  on low volume asphalt roads (lt 300,000 ESALs)
• On moderate to high volume route there was no
  LCCA advantage for SMA overlay on JRC pavements,
  however
• Small sample of relatively young overlays
  pavements
• Substrate pavement with SMA overlay were rougher
  and more deteriorated than those with dense
  graded mixes

4
NCAT Work with Georgia Aggregate

• All granite aggregate from Georgia
• 16 to 44 LA loss
• Trials on the test track using various compaction
• 50, 75 and 100 gyrations
• 50 blow Marshall
• Regression analysis on Gmb
• 35 gyrations ? 50 blow Marshall
• Attributed to high LA loss on course aggregate
• Georgia uses 50 gyrations for SMA

5
Virginia Transportation Research Council

• 2007 study on the cost of SMA vs. other HMA
  choices for surface course
• Concluded that SMA has a cost advantage in excess
  of 7,500 per lane-mile in net present value
  costs
• Saving to Virginia based on exclusive use of SMA
  estimated to be 25 million net present value

6
Testing for Durability

• Looking for a procedure to evaluate the
  durability of HMA mixes including SMA and porous
  asphalt mixes by FHWA
• Asphalt Mixture Performance Tester
• Formerly the Simple Performance Tester

7

• Thank you
• Any questions