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HIGH RAP MIXTURES
Properties of Plant Mixes Containing High Asphalt Binder ReplacementHigh Asphalt Binder Replacement
Gerry Huber
Heritage Research Group
Objective
How much RAP can be used?How much RAP can be used?
Considerations Quality product
Mixing plant Mixing plant
Placement
Compaction
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Is RAP Available?
Scope
How much RAP can go through a plant?How much RAP can go through a plant? Trials up to 70%
Produce and Place on Low Volume Road Measure qualityq y
Measure properties
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Asphalt Binder Replacement
bi dl d%
RAP
Coarse RAP
Fine RAP
Shingles
bindertotal
binderrecycledtreplacemenbinderAsphalt
%
%%
Typical Asphalt Binder Content
RAP 4 5%RAP 4 – 5%
Fine RAP 5 – 7%
Coarse RAP 2 – 3%
Manufacturer Scrap 18 – 22%
Post Consumer 22 25%Post Consumer 22 – 25%
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Experiment
Field ExperimentField Experiment
Focus on High Binder Replacement RAP
Post Consumer Asphalt Shingles
Phase One
RAP Counter flow drumRAP 50%
60%
70%
Post Consumer Shingles
Counter flow drum mix plant
Embedded burner RAP inlet capacity
Mixing chamber volumeShingles
0%
3%
Water injection Mixing aid
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Phase One Mixes
Mix Size RAP RAS AC BRMix Size RAP RAS AC BR
1 25.0 70 0 6.0 33
2 25.0 60 0 4.1 41
3 12.5 60 0 (47)
4 12 5 50 3 5 6 294 12.5 50 3 5.6 29
5 12.5 50 3 7.1 31
6 12.5 50 3 6.6 33
Discharge Temperature
350
100
150
200
250
300
350
rge
Tem
per
atu
re,
F
0
50
100
Dis
cha
70% 60% 60% 50% 50% 50%
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Aggregate Temperature
900
500
600
700
800
900
gat
e T
emp
erat
ure
, F
300
400
Ag
gre
g
70% 60% 60% 50% 50% 50%
60% RAP
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70% RAP
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Drum Temperature
600
200
300
400
500
600
hel
l T
emp
erat
ure
, F
0
100
Dru
m S
70% 60% 60% 50% 50% 50%
Decisions from Phase One
Maximum 50% RAPMaximum 50% RAP
Drum Shell Temperature max 800 F
Aggregate Temperature max 700 F max 700 F
Exhaust Temperature min 220 F
max 390 F
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Phase Two Experiment
Counterflow drum mix plantCounterflow drum mix plant With mixing drum
19 mm NMPS 1.0 in crushed gravel
½ in crushed limestone
½ in pea gravel
Natural sand
RAP Feeder
Counter Flow Drum
Mixer Drum
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1.0 inch Crushed Gravel
½ inch Crushed Limestone
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½ inch Pea Gravel
Natural Sand
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Phase Two Recycled Materials
Fine RAPFine RAP
Coarse RAP
Post Consumer Shingles
Post Consumer Shingles
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Post Consumer Shingles
Coarse RAP (½ to 1 inch)
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Coarse RAP (½ to 1 inch)
Fine RAP (minus ½ inch)
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Fine RAP (minus ½ inch)
Recycled Components35
Coarse RAP
10
15
20
25
30
cycl
ed P
erce
nta
ge
Coarse RAP
Fine RAP
Shingles
0
5Rec
Mix 964-22
Mix 1052-28
Mix 1152-28
Mix 1252-28
Mix 1364-22
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Asphalt Binder Replacement
70
20
30
40
50
60
70A
sph
alt
Bin
der
R
epla
cem
ent,
%
0
10
R
Mix 9 64-22
Mix 10 52-28
Mix 11 52-28
Mix 12 52-28
Mix 13 64-22
Discharge Temperature
300
100
150
200
250
300
rge
Tem
per
atu
re,
F
0
50
Dis
cha
Mix 9 Mix 10 Mix 11 Mix 12 Mix 13
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Aggregate Temperature
800
300
400
500
600
700
800
gat
e T
emp
erat
ure
, F
0
100
200
Ag
gre
g
Mix 9 Mix 10 Mix 11 Mix 12 Mix 13
Volumetric Properties6.0
Asphalt Content
2.0
3.0
4.0
5.0
Per
cen
tag
e
Asphalt Content
Air Voids
0.0
1.0
Mix 9 64-22
Mix 1052-28
Mix 1152-28
Mix 1252-28
Mix 1364-22
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Asphalt Binder Grade
70 080.0
0.010.020.030.040.050.060.070.0
rfo
rman
ce G
rad
e
-30.0-20.0-10.0
0 0
Pe
Mix 9 64-22
Mix 1052-28
Mix 1152-28
Mix 1252-28
Mix 1364-22
Mechanical Properties
StiffnessStiffness Low frequency
Aggregate dominates
High frequencyA h l Bi d d iAsphalt Binder dominates
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Mixture Stiffness (E*)0.1 Hz 10 Hz
400
600
800
1,000
1,200
amic
Mo
du
lus,
40C
, 1
0Hz,
ksi
400
600
800
1,000
1,200
mic
Mo
du
lus,
40C
, 10
Hz,
MP
a
-
200
42 44 46 48 50Average of High and Low
Temperature Grade, C
Dyn
-
200
42 44 46 48 50Average of High and Low
Temperature Grade, CD
ynam
Cantabro Loss Test (Durability)
LA AbrasionLA Abrasion Test Machine
Test withoutSteel Balls
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Cantabro Test (Durability)
12
14
16
18
20
22
24
Can
tab
ro L
oss
, %
14
16
18
20
22
24
Ca
nta
bro
Lo
ss
, %
10
12
40 50 60 70Asphalt Binder Replacement, %
10
12
42 44 46 48 50Average Temperature Grade, C
Blending Analysis
TTM323 to calculate
virginRAP
virginblend
T - T
T-T% RAP
M323 to calculatethe limiting amount
Predicted Temperature of Blend
)(% VirginRAPvirginblend TTRAPTT
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Blending Analysis
For multipleFor multiple recycled materials
Tblend
%%%% Vi i TRAS TTRAPTRAP
)%%%(%
%%%%
VirginRASRAPRAP
VirginxTRASxTxTRAPxTRAP
CF
virginRASRAPCRAPF CF
Calculated vs Measured
66
68
70
72
74
76
78
80
82
alcu
late
d H
igh
Gra
de,
C
24
-22
-20
-18
-16
-14
-12
-10
alcu
late
d L
ow
Gra
de,
C
64
66
64 66 68 70 72 74 76 78 80 82
Measured High Grade, C
Ca
-26
-24
-26 -24 -22 -20 -18 -16 -14 -12 -10
Measured Low Grade, C
Ca
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Placement
County Road resurfacingCounty Road resurfacing 50 mm base
19.0-mm mix
38 mm surface
Placed May 31, 2011
June 1, 2011
Construction Conditions
Haul time CompactorHaul time 30 minutes approx
Weather 85F sunny
PaverRoadtec RP150
Compactor Bomag BW266
3 vibratory passes, 1 static
Roadtec RP150 50 to 60 ft/min
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Existing Condition
Laydown Operation
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Uncompacted Mat
Compaction
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Compacted Mat
Quantity Placed
Mix Number TonsMix Number Tons
9 300
10 150
11 300
12 125
13 125
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Paving Crew Observations
Flows through paverFlows through paver
Mat lays well (little handwork in this application)
Compacts well No tenderness No tenderness
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Phase 1 Conclusions
50% RAP is reasonable maximum50% RAP is reasonable maximum With conventional counterflow drum
With 60 and 70% RAP Uncoated particles present
Aggregate temperature too highgg g p g Burns the asphalt binder
Drum temperature too high Metal softens and wears
Phase 1 Conclusions (cont’d)
Criteria selected forCriteria selected for Drum shell temperature
800˚F maximum
Virgin aggregate temperature 700˚F maximum
Bag house exhaust 220˚F minimum
390˚F maximum
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Phase 2 Conclusions
Volumetric Properties Can BeVolumetric Properties Can Be Controlled With 50% RAP
With 67% asphalt binder replacement
Durable Mixtures Can Be Produced With 67% asphalt binder replacement
18% from RAS
49% from RAP
Phase 2 Conclusions (cont’d)
Mixture Stiffness (E*)Mixture Stiffness (E ) Decreased as average binder grade
increased
Counter-intuitive
Not explained
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Phase 2 Conclusions (cont’d)
High Temperature GradeHigh Temperature Grade Not well predicted with blending formula
Some under predicted
Some over predicted
Low Temperature Grade Consistently under predicted by blending
formula
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RAP in HMA
Black Rock?Black Rock? Limestone
3 million – 12 million psi
Aged Asphalt Binder 150,000 psi glassy stiffness
1,500 psi (50F)
Homogenous Blending? No
Partial Blending??
Partial Blending
CompositeComposite Material Virgin Binder
ReclaimedBinder
