High Percentage RAP Mixes How do We build Them John D’Angelo D’Angelo Consulting, LLC [email protected]

Recycled Asphalt Pavement Usage

Surface Mixes -- Average Use

0% 1 - 10% 10 - 20% 20 - 30% 30% n/a

Recycled Asphalt Pavement Usage

Barriers to Increasing RAP

Recycled Asphalt Pavement Usage

Barriers • Stockpile Management - 34% – – – – –

Quality of original stone Gradation Control Origin of Material Unknown Processing Requirements Additional Testing

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Barriers • Long Term Performance – 18% – – – – – –

Durability Questions Additional Testing Requirements Variability of RAP Mixes Unknown Performance Characteristics Lack of Performance Test “Could” Have Early Failure

Recycled Asphalt Pavement Usage

Barriers • Binder Issues – 13% – – – – –

Bumping Grade Properties of Final Blend Compaction Issues Additional Tank Required Lower Grade not Available/Expensive

Recycled Asphalt Pavement Usage

Barriers • Availability of RAP – 11% – – – – –

Use in Base or Shoulders (unbound) Used by Maintenance Concern about moisture Too contaminated Cannot Meet Gradation Requirements

Recycled Asphalt Pavement Usage

Barriers • Other – 24% – – – – –

Contractor Unwilling to Use Lack of Experience Existing Specifications Resistance of Pavement Designers Research Did Not Support Performance

Recycled Asphalt Pavement Usage

Other Barriers • Resistance to Change • Perceptions – – – –

Less Quality Industry Can’t Do It Value Not Shared Difficult to Evaluate

Recycled Asphalt Pavement Usage

Other Barriers • Low Risk Tolerance – It Might Fail – Current System is Working – More Research Needed

Recycled Asphalt Pavement Usage

Agency Requirements on RAP Sources Some agencies only allow RAP obtained from their projects to be used in their mixes. This restriction hinders the use of RAP to its full advantage. The quality of materials (e.g. aggregate source properties and polishing characteristics) in the RAP can and should be verified with routine testing as part of mix design and quality control Recycled Asphalt Pavement Usage

RAP Technical Issues • Effect on Binder Grade • Current Recommendations – 25%, do blending study Many agencies have increased the percentages for when to change grades, only mix testing will determine how stiff the mix really is. Recycled Asphalt Pavement Usage

Recycled Asphalt Pavement Usage

Mix Specifications • • • •

Cannot “swap gradations” Same as for virgin (basically) Follow AASHTO specs for grade change* Air voids, VMA, VFA, etc all remain the same • Use “Gsb” for VMA calculations

Recycled Asphalt Pavement Usage

Maximum Practical RAP Usage Considerations •Mix Design •Customer Specifications •RAP Availability •Plant Type

Item

Maximum RAP %

Base

35

Intermediate

35

Surface

25

Recycled Asphalt Pavement Usage

RAP Processing • Key to successful RAP mixes

Recycled Asphalt Pavement Usage

RAP Sources Pavement Milling

Asphalt Pavement Removal

Plant Waste Material Recycled Asphalt Pavement Usage

RAP Stockpile Options Isolate RAP Sources (e.g. millings, friction aggregate)

Blend Multiple Sources

Recycled Asphalt Pavement Usage

Unprocessed RAP Piles • Keep the unprocessed RAP clean – Check haul trucks for contamination (dirt, etc.) – Monitor for other debris

• Build consistent piles – Spread materials around as pile being built • Digouts • Plant waste • Etc Recycled Asphalt Pavement Usage

RAP Processing Options Screening

Crushing

Fractionating Recycled Asphalt Pavement Usage

Using Millings Without Processing • Control mill speed at the jobsite • Mill surface / intermediate separate from the base • Use 1-inch scalping screen

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Milled RAP

Keep millings from different projects in separate stockpiles. Milled RAP can typically be used “as is” in HMA without further crushing. Source Randy West

Recycled Asphalt Pavement Usage

Multiple Source RAP also known as GOK piles

God Only Knows what’s in there

Source Randy West

Small Jobs Recycled Asphalt Pavement Usage

Processing to Minimize Variability • • • • •

Pull from different parts of the pile Keep production constant Keep screens clean of debris Build non-segregated piles Test during production for – Gradation – Asphalt content Recycled Asphalt Pavement Usage

Crushing RAP Crush to one size (½ in. minus allows use in surface)

Processed RAP Build uniform stockpile

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Fractionated RAP 3/4 x 3/16” RAP In back

+3/4” RAP

-3/16” RAP

• A huge advantage for mix design. Allows RAP to be used in practically any mix type • Screening RAP into two or more sizes

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Recycled Asphalt Pavement Usage

Fractionating Gives More Flexibility Fine minus ½ in.

Coarse ½ to 1 in.

Recycled Asphalt Pavement Usage

Recycled Asphalt Pavement Usage

Highly Variable RAP Stockpile

Recycled Asphalt Pavement Usage

Variable RAP Gradations 100 90 80

Percent Passing

70 60 50 Maximum Density Line

40 30 20 10 0

#200 #80 #50 #40 #30

1

2

#10 #8

#4 3

3/8"

Sieve Size 4

1 /2"

5/8" 5

3/4"

7/8"

1"

1 1/4"

6 Avg. Recycled Asphalt Pavement Usage

Reclaimed Asphalt Pavement (RAP) 

Fractionating RAP into 2 or more stockpiles can significantly improve variability.

 Gradation and composition of fractionated RAP are typically consistent in size and quality. Recycled Asphalt Pavement Usage

Uniform & Consistent Gradations 100

-1/2" Inch RAP

90

Maximum Density Line

80

Percent Passing

70 60 50 40 30 20 10 0

#200 1 12

#10 #8

#80 #50 #40 #30 2 13

3 14

4 15

5 16

#4

3/8"

Sieve Size 6 17

7 18

8

1 /2" 9

5/8" 10

Recycled Asphalt Pavement 19 20 Avg. Usage

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Maintaining RAP Quality • Stockpiling – Conical – Well-maintained – Sample frequently

• Comprehensive QC testing – – – –

Absorption Moisture content Asphalt content Gradation Recycled Asphalt Pavement Usage

Testing of RAP • Asphalt Content: ignition method is preferred. An aggregate correction factor must be assumed. For regions that utilize dolomite aggregates that have erratic correction factors, a solvent extraction method is recommended.

Recycled Asphalt Pavement Usage

Testing of RAP Aggregate bulk specific gravity: estimated from a three step process 1. Determine Gmm (w/ dryback) of RAP sample 2. Calculate Gse using the Gmm from step 1 and the asphalt content from the ignition method (or extraction test if ignition method is not reliable) 3. Estimate Gsb from Gse using a typical offset value or regression from historical mix designs with the aggregates in the region

Recycled Asphalt Pavement Usage

Look at best practices to optimize the use of RAP. Recycled Asphalt Pavement Usage

Recycled Asphalt Pavement Usage

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Efficient Operations • Loader operator • RAP feed system – Scalping screen

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Feed With Two Bins For High RAP Feed from two locations in stockpile

Two RAP bins to reduce variability

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At the Plant • • • •

Superheating of aggregate Air flow Baghouse Warm mix

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Insuring Quality • Final mixture – – – – –

Volumetric properties Extraction Gradation Asphalt content High-RAP • PG grade of blended binder • Quality of Aggregate

• Performance Testing

Recycled Asphalt Pavement Usage

Laydown and Compaction – No special requirement/techniques

• May require more attention than conventional mixes

– Mix Workability - Stiffer

• Density • Heat mixture, more roller passes, heavier roller?

– Cooler temperatures

• Reduced compaction times • Warm mix technologies can extend compaction times

Recycled Asphalt Pavement Usage

Summary • Asphalt Pavement Recycling

– Greatest single upfront cost saving measure available to highway agencies is increasing the use of RAP in the construction and rehabilitation of asphalt pavements.

• The majority of State DOTs use between 10 and 20% RAP.

• Contractors can effectively use RAP often and in high amounts with processing and production best practices.

Recycled Asphalt Pavement Usage

Reclaimed Asphalt Pavement • Can be used above 25% • Can be made into QUALITY hot mix asphalt pavements

Recycled Asphalt Pavement Usage

Thank you! Questions?

Recycled Asphalt Pavement Usage