RAP and RAS:Where Are We
Where are We Going
Gerald HuberHeritage Research Group
RAP Use
Drivers
Economics◦ RAP reducesinput costs
Environmental◦ Pressureagainstwasting
Environmental Pressure
AASHTO STANDARD
M323SuperpaveVolumetricMix Design
Proposed Changes◦ Ballot Dec 2014
M323 Terminology
Percent RAP◦ Reclaimed Asphalt Pavement Binder Ratio(RAPBR)
◦𝑅𝐴𝑃𝐵𝑅 =𝑃𝑏
𝑅𝐴𝑃𝑥 𝑃𝑅𝐴𝑃
𝑃𝑏𝑡𝑜𝑡𝑎𝑙
M323 Binder Grade Selection
Virgin Binder Grade
X1: Procedure for Estimating Properties of Blended RAP and Virgin Binders
No Change in Grade < 25%
Follow Recommendations X1
>= 25%
FHWA Memo
Premature CrackingReported
FHWA Recommendations
Increasing RAP (and RAS)◦ May reduce cracking resistance
Potential increased aging
BUT
Existing Pavement Condition being Overlaid
Mix Design using Actual Gsb
Quality Assurance Process
Effect of Recycle Content
300oF - 320oF 240oF - 270oF
- Foam Chem
0% - -
20% RAPBR≈ 23% by weight
20% RASBR
≈ 6% Shingle by weight
40% RAPBR≈ 44% by
weight
PG58-28 PG58-28PG58-28
PG64-22
PG64-22
PG64-22 PG64-22
PG58-28
PG64-22
PG64-22
Diffusion
1
10
100 60
1.7
105
Vis
@1
00
C,
Pa.s
shear
Virgin asphalt
acts as a
‘lubricant’
Pavel Kriz
Esso Canada
Diffusion
Happens with Time
1
10
100
1 100 10000
η*,
Pa.
s
Diffusion Time, s
1
10
100
1 100 10000
η*,
Pa.
s
Diffusion Time, s
1
10
100
1 100 10000
η*,
Pa.
s
Diffusion Time, s
1
10
100
1 100 10000
η*,
Pa.
s
Diffusion Time, s
RAP
50/50 Blend
Virgin
Diffusion
𝐿𝑦
Pavel Kriz
Esso Canada
Effect of Temperature on Diffusion
Time to equilibrium
Homogenous Blend
Blending by Diffusion
Pavel Kriz
Esso Canada
Diffusion In Practice
Pavel Kriz
Esso Canada
10-4
10-2
100
102
104
0.5
0.6
0.7
0.8
0.9
1
Time, days
* /
* ho
mo
gen
ou
s b
len
d, 10
7 P
a.s
HMA
WMA
100 days
mix
silo
transport
paving
service
Fra
cti
on
of
Ho
mo
gen
ou
s V
isco
sit
y
Time, days
HIGH RAP Workshop
Sponsored by◦ Dutch Ministry of Transport
◦ TU Delft
Current Practice◦ High MINIMUM RAP
(50%?)
Theoretical
Practical
Dutch Experience
TU Delft Research
Looking atBlending Zone
Mixing
Occurs by Diffusion
Contractor Visits
Trials at 90%
RAP entry point
into weigh hopper
Contractor 2
JAPAN
NAPA Tour to Japan
High RecycleContent
50% min?
U.S. Experience
RAS
North American Issue
Recycled Asphalt Shingle Use
AASHTO Standards Change
Gradation adjusted finer◦ 95% passing 9.5-mm sieve
Deleterious ◦ Reduced from 3% to 1%
Asphalt Binder Availability Factor◦ Simplified methodology
Future?
Increased RAP and RAS
Increased use of “Rejuvenators”◦ Soft hydrocarbons
◦ Crude oil-based
◦ Bio-based
Continued Research◦ RAP: Reasonably Mature
◦ RAS: More information is needed
Recommended
