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Asphalt Pavement Sustainability

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					Asphalt Pavement Sustainability




               Kent Hansen, PE
           Director of Engineering
    National Asphalt Pavement Association
Sustainability ‐ Definition

• Development that meets the 
  needs of the present without 
  compromising the ability of 
  future generations to meet their 
  own needs.
• Doing what is right
Why is asphalt sustainable

 •   100% Recyclable
 •   Can use other recycled materials
 •   Low carbon footprint pavement
 •   Long life & Fast resurfacing
 •   Warm‐Mix Asphalt
 •   Porous pavement for stormwater
        Recycleability

• Asphalt is the No. 1 reused material
• 1995 FHWA Report to congress
  – 90 Million tons reclaimed
  – 80% recycled
• 2006 Contractor Survey
  – ~69% reused in HMA
  – ~27% other recycling
  – ~3% discarded
Why Recycle RAP into HMA

•   Best and Highest use
•   Reduces demand for new materials
•   Reduces carbon footprint
•   Contains valuable materials
    – Aggregate ~95% >$10/ton
    – Asphalt ~5% > $600/ton
    – Value >$39.50/ton (minus processing)
RAP from Multiple Sources
    Shingles
• Materials already used in 
  HMA
     •   >20% asphalt binder
     •   Fibers
     •   Sand
• Usually 5% of mix
     • Saves 1% binder > $6.00 ton
• Primarily from Mfg. Waste
• Tear‐offs
     • Concern about asbestos
     • Not used since early 80’s
     • 27,000 samples ~1% detected
Over the past two years, MoDOT has allowed contractors to put used 
shingles that have been removed from rooftops into their asphalt mix. 
The result is a very durable, more‐rut resistant asphalt at a much 
lower price.


The use of recycled shingles saves $3 to $5 per ton of asphalt. That 
may not sound like much at first, but consider this: a typical 
resurfacing project would use about 30,000 tons of asphalt, for a 
savings of $90,000 to $150,000. 
      Other Recycled Materials
• Crumb rubber (from tires)



• Steel slag



• Glass
            Energy Consumption per Tonne

                                                                 HMA
                                                                  High Modulus HMA

                                                            HMA w/ 15% RAP

                                      WMA will reduce               Reduction w/ 15% RAP

                                                                       PCCP

                                                                                                   CRCP




Ref: Analysis of energy consumption and greenhouse gas emissions, Pierre T. Dorchies, M.Sc., P.Eng, Michel
Chappat, Julian Bilal
                                   CO2 eq kg/tonne

                                                 HMA
                                                High Modulus HMA
                                               HMA w/ 15% RAP

                                                                  Reduction w/ 15% RAP
                                   WMA will reduce

                                                                            PCCP
                                                                                                    CRCP




Ref: Analysis of energy consumption and greenhouse gas emissions, Pierre T. Dorchies, M.Sc., P.Eng, Michel
Chappat, Julian Bilal
BEES: econ. & env. impacts
BEES
Urban Heat Islands
myth or reality ?
reflectivity & temperatures
               ?? ?




reflectivity & temperatures
cooler pavements
cooler pavements
                   Interstate w/ PCC   Highway w/ PCC




                                                                                   Below grade 
                                       mo                                          w/ sound 
                                         un
                                              ta                                   walls
                                                in 
                                                   r   an
¾ inch asphalt‐                                           g   e
based OGFC over                                                                     Above 
dense pvmt                                                                          grade w/ 
                                                                                    landscape


                                                                                   Below grade 
                                                                                   w/ sound 
                                                                                   walls
                                                                  Airport: 23‐inch thick pvmt



cooler pavements
                                               e
                                         is su
                                  hite
                                w
                          a nd
                   lack                pavement thickness

               a  b            material capacities      .

          OT              surface vs. air temperature   s    


  ’s    N               pavement air voids (OGFC) cooler

It                   UHI does NOT cause Global Warming
LEED
LEED: Leadership in Energy and Environmental Design

• Developed by USGBC
• National benchmark for design, construction, and operation of 
  “green” buildings
• 5 key areas:
   –   Sustainable site development
   –   Water savings
   –   Energy efficiency
   –   Materials selection
   –   Indoor environmental quality
• Earning LEED certification
   – Must meet certain criteria  credits / certification process
   – Levels based on total credits
• How asphalt pavements contribute to LEED credits



LEED process
LEED for new construction                                                                  Distribution              200+
                                                                                                                     100‐199
buildings as of 07/06                                                                     by geography               50‐99
                                                                                                                     20‐49
                                                                                                                     1‐19



                  186
  480
                                                                                                                     23 (DE)
                                                                                                                       24 (NH)
                 134
                                                                                                               174
                                       9                                                                                 33
                                                   4        22                                               173         105
                                                                          36            119
                             11                    9
                                           11
AK=10                                                                          120                       68                  12
                        40                                       23                           79                     61 27
HI=16                             28       69      14                                                         95       9 (DE) 38 (DC)
PR=1                                                                                 19       4
                                                   8                  57
                                                        5 (OK)                                                74
                             82                                                         11
                                       25
                                                                                   22                    52
                                                  125                                             102
                                                                  19                 18
                                                                               6
                                                                      6
                                                                                                        73


                                                Test
                       LEED Credits
Rating Category   Credit Description           Pavement Type      Credits
SS Credit 6.1     SW Design: Quantity          Porous Asphalt         1
                  Control
SS Credit 6.2     SW Design: Quality Control   Porous Asphalt         1
SS Credit 7.X     Heat Island Effect: Non‐     Reflective Surf.     1 – 3
                  Roof                         OG Asphalt
                                               Porous Asphalt
MR Credit 2.X     Const. Waste Mgt.            RAP                  1 – 2
                  Divert from disposal
ID Credit 1.X     Exceptional Performance or  WMA                   1 – 4
                  areas not addressed         High RAP
        Long Life

• Lower Life Cycle Cost
  – Better Use of Resources
  – Low Incremental Costs for
    Surface Renewal
• Lower User Delay Cost
  – Shorter Work Zone Periods
  – Off-Peak Period Construction
           Perpetual Pavement


     }
                         40-75 mm SMA, OGFC or Superpave
            100 mm      Zone
            to         Of High
            150 mm
                     Compression       High Modulus
                                       Rut Resistant Material
                                       (Varies As Needed)


                                   Flexible Fatigue Resistant
Max Tensile Strain                 Material 75 - 100 mm




              Pavement Foundation
                                Rehabilitation
                                   Possible Distresses
                                         › Top-Down Fatigue      Solutions
                                         › Thermal Cracking         › Mill & Fill
                                         › Raveling                 › Thin Overlay


                           50 - 100 mm
                                                  Mill Surface – Use for RAP
                                               High Quality SMA, OGFC or Superpave
Structure Remains Intact




                                                       20+ Years
                                                         Later
           Warm Mix

• Will dominate the market in < 5 years
• Reduced energy consumption
• Reduced emissions
    No hazardous fumes/worker exposure
• Plants compatible in congested areas
• No odors
Porous Asphalt Pavements
 w/ Stone Recharge Beds
       What are Porous Pavements?

    Open-Graded HMA ~ 2 ½”
½” Agg. (#57) ~ 1 – 2” Thick

Clean Uniformly Graded 2”-3”
Crushed Agg. (#2) – 40% Voids


Non-Woven Geotextile
Uncompacted Subgrade
Port of Portland
                           Median Polutant Removal Efficiency




                     -20
                              0
                                   20
                                        40
                                             60
                                                  80
                                                       100
                                                             120




Infiltration
                  Total
               Phosphorus




Wetlands
                Soluable
               Phosphorus


                   Total
                 Nitrogen




Wet Ponds
                   Nitrate



Filtering
                                                                   Water Quality




                     Zink
Swales




                      TSS
Dry Ponds
Water Quality
                          Detention vs. Infiltration
             4
                     Post-Dev. Inflow
                     Infiltration Bed Discharge
                     Pre-Development Runoff
             3
                     Detention Basin Discharge
Flow (cfs)




             2



             1



             0
                 0       400         800          1200   1600   2000   2400
                                           Time
                Walden Pond 1977
1997 Report: “Twenty years later, a long time for one paving 
job on that busy parking lot, it still looks good and works well.”




                                                  2008
                    Roads
          Arizona

                                                 Portland, OR

                                         e   d
Porou
      s                             r ad
                                 e G
                         n   s
                      De




               Salem, OR                         Chicago, IL
What else are we or could we be doing

      • Reducing energy consumption
        – Covering stockpiles 
           • 1% moisture = 10+% production
        – Insulating tanks & lines
        – More efficient burners/heat 
          transfer
        – VFD
RAP + Porous + Warm Mix

  = Sustainability
Innovation

				
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posted:11/9/2011
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