Saving Your Asphalt! 36 th Annual Rocky Mountain Asphalt Conference & Equipment Show February 18-20,...
-
Upload
maryann-stevenson -
Category
Documents
-
view
213 -
download
0
Transcript of Saving Your Asphalt! 36 th Annual Rocky Mountain Asphalt Conference & Equipment Show February 18-20,...
Saving YourAsphalt!
36th AnnualRocky Mountain
Asphalt Conference & Equipment ShowFebruary 18-20, 2009
The Bad News
The “Good” News
Let’s not get caught off-guard next time!
The “Bad” News
NaturalDisasters
UnnaturalDisasters
Five Ways to Save Your Asphalt
• Up the RAP
• Rock the Asphalt
• Thinner Overlays
• The Right Asphalt for the Right Occasion
• Raise the Roof with Shingles
• Perpetuate Asphalt Pavements
Up the RAP
• Reuse what you have.
• Characterize it like it was any other component of your product.
• Process it properly.
• Advantages– Economics– Environment– Performance
RAP Guides
RAP Example
• Virgin mix requires 5.5% AC
• RAP has 4.0% AC
• Use 30% RAP – Reduce virgin AC 1.2%
• RAP Processing - $6.00/ton
• AC price $650/ton – Aggr. price $10/ton
• On 1 ton HMA reduce AC by 0.012 tons
• Reduce aggregate by 0.28 tons
• SAVE $8.80/ton!
AASHTO Survey of States
• Objectives– Find extent
of RAP usage
– Find the roadblocks to usage
RAP Use in Base
Allowed
Used
0%10%15%20%25%30%n/a
RAP Use in Binder
Allowed
Used
0%10%15%20%25%30%n/a
RAP Use in Surface
Allowed
Used
0%10%15%20%25%30%n/a
The Survey Says. . .
• We can do more recycling under the existing specs. Need to consider how it’s handled.
• Need to consider availability.• Not much consistency between states on
what’s allowed.• We need to work with agencies to get RAP
percentages increased, especially in surface mixes.
What is limiting RAP?
• Specification limits Superpave
• Specification limits surface
• Lack of knowledge by specifiers
• Specification limits PMA
• Binder Issues
Rock the Asphalt!
• Use Large Stone Mixes where possible.
• Larger aggregate mixes need less asphalt to provide the same coating.
• Applications– Heavy duty
pavements– Base mixes
Surface Area
10”
10”
10”
10”
10”
10” Cube of 1” BallsSurface Area = 3,142 in2
10” Cube of 1/2” BallsSurface Area = 6,280 in2
10”
Larger Stone Mixes
3.32% 3.07%
3.76%
4.66%
4.21%
2.00%
3.00%
4.00%
5.00%
6.00%
7.00%
9.5 12.5 19 25 37.5
Large Stone Example
• Compare 1-3/4” mix to 5/8” mix
• LSM uses 1.7% less asphalt
• Save 0.017 tons AC per ton HMA
• Save $11.05 per ton HMA!
Issues with LSM
• Segregation
• Equipment wear
• Sampling
• Permeability
• Noise
Thinner Overlays
• If overlay placed to correct functional deficiency (smoothness) rather than structural, consider a thinner overlay.
• Lift thickness related to aggregate size.
• Fine aggregate mixes do not rut more than coarse aggregate mixes. – NCHRP Report 539
Thin Overlay Example
• Say NMAS/lift is 4• For 12.5 mm mix ~ 50 mm
– AC content 6.0%– 217 lbs/sy = $8.14/sy @ $75/ton
• For 9.5 mm mix ~ 37.5 mm– AC content 6.5%– 163 lbs/sy = $6.93/sy @ $85/ton
• Thinner overlay = 18% less asphalt• Thinner overlay = $1.21/sy less
When not to use Thin Overlays
• When large NMAS is specified.
• When structural improvement is needed.
Don’t Be Gauche – Use the Right Asphalt
• Polymer modified asphalt has many uses:– Reduce rutting– Reduce thermal cracking– Reduce fatigue cracking– Improve overall durability
• Can also be misused:– Low volume roads– Overlays of cracked pavements– Base layers
PMA Economics
• Can be $60 to $80/ton higher than unmodified asphalt
• Can raise HMA price by $4.80/ton
Raise the Roof with Shingles
• Roofing shingles comprised of:– Polymer modified asphalt– Fiberglass or felt fibers– Grit – angular fine
aggregate– Mineral filler
Example
• Roofing shingles contain ~ 20% asphalt
• Use 5% shingles in HMA, reduce 1% asphalt
• Reduce 0.01 ton AC/ton HMA
• Reduce cost by $6.50/ton HMA
Issues with Shingles
• Tear-off shingles require more processing than manufacturing waste.
• Be careful using tear-offs and RAP in same mix. Make sure there is enough virgin asphalt.
• Sizing of shingle particles is important – should be minus ½ inch.
Not What We’re Looking For!
Perpetual Pavements
• The sixth of five ways to save asphalt!
• Save asphalt and aggregate over the long term. It’s sustainable.
• Lower Life Cycle Cost
• Lower User Cost
Concept
Max Tensile Strain
Pavement Foundation
High ModulusRut Resistant Material(Varies As Needed)
Flexible Fatigue ResistantMaterial 75 - 100 mm
40-75 mm SMA, OGFC or Superpave
}100 mmto150 mm
ZoneOf High
Compression
Perpetual Pavementversus
Conventional Design
0
5
10
15
20
25
0.1 1 10 100 1000
Traffic, ESAL
HM
A T
hic
kne
ss, i
n.
AASHTO High
PerRoad
Comparison of Structures
Year Activity
0 6” HMA/10” Base
15 Mill 2”/Overlay 3”
25 10% Patching + Mill 2”/Overlay 3”
35 Reconstruct with 8” HMA
50 Mill 2”/Overlay 3”
Year Activity
0 11” HMA/6” Base
18 Mill 2”/Overlay 2”
33 Mill 2”/Overlay 2”
48 Mill 2”/Overlay 2”
50 ------
Conventional Perpetual
Conventional (tons/lane-mile)
Perpetual Pavement (tons/lane-mile)
Year HMA* Gravel Base* HMA* Gravel Base*
0 2,376 3,168 4,356 1,901
15 1,188
18 792
25 1,426
33 792
35 3,168
48 792
50 1,188
Total 9,346 3,168 6,732 1,901
RAP 2,337 1,683
Aggregate 6,659 3,168 4,797 1,901
Asphalt Binder**
350 252
Material Usage
0
5000
10000
HM
A, t
ons
Conv. Perp. Pvmt.0
1000
2000
3000
RA
P, t
ons
Conv. Perp. Pvmt.
0
5000
10000
Agg
rega
te,
tons
Conv. Perp. Pvmt. 0
100
200
300
400
Bin
der,
ton
s
Conv. Perp. Pvmt.
Save 32% Save 28%
Save 31% Save 28%
Costs
Save 44%
Summary
• Possible to save both asphalt and aggregate.
• Need to apply proper solutions.
• Need to apply engineering principles.
• DON’T SACRIFICE QUALITY!
Other Ideas
• Get Pavement considered as part of solution to road noise – Lower Noise Barriers by 3 ft!
• Use Rubblization with Overlay rather than Remove and Replace PCC – Save 60 to 70% of Total Cost!