Saving Your Asphalt!

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!