CALAPA

FALL ASPHALT PAVEMENT CONFERENCE &

EQUIPMENT EXPO

OCTOBER 28, 2015

PRACTICAL ASPECTS OF USING AND MAKINGHIGH RAP & RAS HMA

STEVEN ESCOBAR & ROBERT STAUGAARD (APART, INC.)

What is a High RAP HMA?

Any HMA that contains ≥ 15w% RAP in the HMA or Binder replacement of ≥ 12w% in the HMA.

Recommend to check consistency in the final HMA even it contains ≤ 15w% RAP. Early cracking has been observed with RAP content in this range.

RAS should always be limited to 3-5% (dwa), maximum or preferably to a lower content.

HIGH RAP HMA

HIGH RAP HMA

HIGH RAP HMA

Key Factors for using high RAP/RAS HMA:

1. Need to determine the asphalt content and the

consistency of the aged binder in the RAP/RAS and each RAP fraction.

Determine the “True PG grade” of RAP/RAS Binder.

HIGH RAP HMA

HIGH RAP HMA

Key Factors for using high RAP/RAS HMA:

2. Need to evaluate recycling agent to adjust consistency in aged RAP/RAS binder to meet PG Grade for climatic condition where the recycled pavement is placed.

3. Soft asphalt cement and/or Recycling Agents needs to be evaluated.

4. For RAS a recycling agent is needed to adjust consistency but RAS binder contribution will be limited. It is too stiff and needs plant modifications to increase dwell and mixing times to make some improvement in binder contribution but it will still be limited.

HIGH RAP HMA

Key Factors for making high RAP HMA:

3. Need to determine gradation of the recovered aggregate in the RAP.

Adjust new aggregate addition to compensate for

any deficiencies.

HIGH RAP HMA

HIGH RAP HMA

hRAP Properties:

h Similar geographic areas will have similar type of pavements based upon aggregate size & asphalt content and grade.

h Try to separate special RAP derived from crumbed rubber, polymer modified and other special pavements.

HIGH RAP HMAgRAP Properties:

g RAP Processing: To gain more control on aggregate gradation and asphalt content in the final mixture; the incoming RAP must be screened into at least four sizes, 3/4”x1/2”, 1/2”x 3/8”, 3/8”x 1/8” & Fines. Only the oversized RAP, greater than ¾”, should be crushed to less than ¾ ‘. These four stockpiles of RAP have definable asphalt content and aggregate gradation parameters which makes it possible to adjust these cuts to meet end-result specifications on the final recycled mixture.

HIGH RAP HMA

PRODUCING THE FINAL ASPHALT MIXTURE Analyze each of the four

RAP crushed stockpiles for asphalt content and aggregate gradation.

HIGH RAP HMA

HIGH RAP HMA

Asphalt Content, w%New

Aggregate

P 1/2” XR 3/8”

P 3/8” X R 4mm

P 4mm X

R 2mmP 2mm

0 2.9 3.9 4.9 6.9

HIGH RAP HMA

Percentage of Each Fraction

Total AC w%

New Aggrega

teP 1/2” XR 3/8”

P 3/8” X R 4mm

P 4mm X

R 2mmP 2mm --

50 5 20 20 5 --

0 2.9 3.9 4.9 6.9 2.25

Target AC is 6.6w% & RAP Binder Contribution is 34.1%

Analyze all data and use data to meet job mix specifications.

HIGH RAP HMA

HIGH RAP HMATests

Specifications

Min. Max.

Functions

Air Voids, %

3.0 6.0 Durability

Marshall Stability, Load, inch/lbs. Flow, 0.01”

2,200 8

4,000 14

Mix Stability

VMA, % 13.0 -- Mix Stability VFA, % 65 78 Mix Stability

Binder Content, %w

4.8

7.5

Mix Stability

Recovered Aggregate Gradation, % Passing

HIGH RAP HMA

Sieve Size Specifications Min. Max.

1” 100 --¾” 100 --½” 95 100

3/8” 72 88#4 46 60#8 28 42#30 15 27#50 10 20

#200 2 7

Key Factors to Consider for Future Hot-Mix Recycling Agents:

• Moving toward “Green” renewal sources is good news. Just because it is “Green” does not make it a suitable product for this application.

• Check phase separation because of big difference in specific gravities with asphalt.

HIGH RAP HMA

HIGH RAP HMA

Key Factors to Consider for Future Hot-Mix Recycling Agents:

• Check volatility (RTFO Oven) because many of these products have results ≥ 15w%.

• Check flask point & thermal degradation.

• Check for odor.

HIGH RAP HMA

Thank You!

Questions?