MECHANICAL PROPERTIES OF MIXTURES CONTAINING RAP
ISAP Working Group WG2:
Meeting on Cold Recycling of RAP
Elie Y. Hajj, Ph.D. Assistant Professor
University of Nevada, Reno United States
Fortaleza, Brazil
September 30, 2012
Introduction
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 2
Pavement Performance
Pavement Life
Recycled Asphalt Pavement
Recycled Asphalt Shingles
Maximize The Use of Recycling Materials without Jeopardizing
Performance
Key for GOOD Performance
Good CharacterizaBon of
Recycled Materials
Introduction
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 3
Virgin Aggregat
e
RAP Mix
Virgin Binder
Target Mix For Project
Select Appropriate Virgin Binder Grade
Target Binder Grade
Target Mix Properties
Impact of RAP on Mixtures’ Properties Review of Selected Literature
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Stiffness
Rutting resistance
Fatigue resistance
Low temperature cracking
Moisture resistance
Impact of RAP on Mixtures’ Properties Review of Selected Literature
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 5
How Does RAP Affect Mixture Stiffness?
Impact of RAP on Mixtures’ Properties Stiffness
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Li et al.(2004): 10 mixes at 0, 20 and 40% RAP, two virgin asphalt binders (PG58-28 and PG58-34), and two RAP sources (RAP and millings).
20-40% RAP →|E*|↑.
No significant impact for RAP on |E*| at low temperatures & high frequencies.
Impact of RAP on Mixtures’ Properties Stiffness
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 7
McDaniel et al. (2006):
15-25% RAP → No significant impact on |E*|.
40% RAP → ↑|E*| at higher temperatures.
RAP Mix
HMA with PG64-22
0% RAP 15% RAP 25% RAP 40% RAP
HMA with PG58-28
25% RAP 40% RAP
Impact of RAP on Mixtures’ Properties Stiffness
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 8
Loria et al. (2011): High RAP test sections in Manitoba, Canada Constructed on 09/2009 (3rd & 4th lifts)
2nd liI: HMA / 50% RAP
1st liI: HMA / 50% RAP
HMA / 15% RAP
HMA / 15% RAP
HMA / No RAP
HMA / No RAP 3rd liI:
HMA / 50% RAP
4th liI: HMA / 50% RAP
∼1.5 miles ∼1.5 miles ∼1.5 miles ∼1.5 miles
HMA / 50% RAP w/ grade change
HMA / 50% RAP w/ grade change
PG58-28 PG52-34 PG58-28 PG58-28
PTH‐8 Project
Impact of RAP on Mixtures’ Properties Stiffness
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 9
Loria et al. (2011): (Cont’d)
1,E+00
1,E+01
1,E+02
1,E+03
1,E+04
1,E‐04 1,E‐03 1,E‐02 1,E‐01 1,E+00 1,E+01 1,E+02 1,E+03
|E*| at 2
1°C (ksi)
Reduced Frequency (Hz)
F‐0%‐150 F‐15%‐150 F‐50%‐150 F‐50%‐200 RAP‐100%
Impact of RAP on Mixtures’ Properties Review of Selected Literature
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 10
How Does RAP Affect Mixture Resistance to
Rutting?
Impact of RAP on Mixtures’ Properties Rutting Resistance
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NCHRP 9-12 (2000):
Impact of 0,10, 20, and 40% RAP content on mixtures’ resistance to rutting.
Generally, ↑ RAP content → ↓Shear deformation → ↑ rutting resistance
0% 1% 2% 3% 4% 5%
0 1.000 2.000 3.000 4.000 5.000
Perm
anen
t She
ar S
train
Cycles
Impact of RAP on Mixtures’ Properties Rutting Resistance
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Xiao et al. (2007): Effect of RAP (0 - 38%) and rubber on APA rutting resistance of HMA mixes.
↑ RAP content → ↑rutting resistance
Rubberized binder increases the rutting resistance
0
2
4
6
8
0 2000 4000 6000 8000
Defor
matio
n (mm
) Strokes (100/point)
Impact of RAP on Mixtures’ Properties Rutting Resistance
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Hajj et al. (2007):
Target Binder PG64-22
Source I Plant waste
(4.6% binder)
0% RAP
15% RAP
30% RAP
Source II 15-year old HMA pavement
(5.4% binder content)
0% RAP
15% RAP
30% RAP
Source III 20-year old HMA pavement
(5.8% binder content)
0% RAP
15% RAP
30% RAP
Target Binder PG64-28
Impact of RAP on Mixtures’ Properties Rutting Resistance
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Hajj et al. (2007): (Cont’d)
Criterion 8 mm at 60°C → good rutting resistance
0
1
2
3
4
5
6
7
8
0% RAP 15% RAP (Source I)
30% RAP (Source I)
15% RAP (Source II)
30% RAP (Source II)
15% RAP (Source III)
30% RAP (Source III)
APA
Rut
Dep
th a
t 60°C
, mm
Mixtures
PG 64-22 PG 64-28 NV
Note: Softer binders may have been used for 15 and 30% RAP
Impact of RAP on Mixtures’ Properties Review of Selected Literature
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How Does RAP Affect Mixture Resistance to
Fatigue?
Impact of RAP on Mixtures’ Properties Fatigue Resistance
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Puttaguanta et al. (1997): Estimated fatigue life of 0, 25 and 50% RAP mixes at 5, 22, and 40°C.
100
1.000
1.000 10.000 100.000 1.000.000
Flexu
ral S
train
(micr
ons)
Cycles to Failure
Impact of RAP on Mixtures’ Properties Fatigue Resistance
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Puttaguanta et al. (1997): Estimated fatigue life of 0, 25 and 50% RAP mixes at 5, 22, and 40°C.
At 5°C, 25 and 50% RAP mixes→ ↓ fatigue resistance.
At 22°C and 40°C all three mixes performed similarly.
Impact of RAP on Mixtures’ Properties Fatigue Resistance
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NCHRP 9-12 (2000): impact of 0,10, 20, and 40% RAP content on mixes’ resistance to fatigue.
10% RAP → no significant impact fatigue resistance.
20 and 40% RAP → ↓ fatigue resistance.
40% RAP mix resistance < 20% RAP mix resistance.
Impact of RAP on Mixtures’ Properties Fatigue Resistance
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Hajj et al. (2007): mixtures with 0, 15 and 30% RAP.
PG64-22 (unmodified): 15% RAP → better or equivalent fatigue resistance.
PG64-28 (SBS polymer-modified): 15-30% RAP → ↓in fatigue resistance but similar or better than unmodified asphalt binder.
Impact of RAP on Mixtures’ Properties Review of Selected Literature
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How Does RAP Affect Mixture Resistance to
Low Temperature Cracking?
Impact of RAP on Mixtures’ Properties Low Temperature Cracking Resistance
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NCHRP 9-12 (2000): Resistance to low temperature cracking using IDT. 10% RAP → no impact on low temperature cracking
resistance. >10% RAP → ↓ low temperature cracking resistance.
Impact of RAP on Mixtures’ Properties Low Temperature Cracking Resistance
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Li et al.(2004 & 2008): 10 RAP mixes with 0-40% RAP using IDT test and SCB fracture test.
IDT: ↑RAP → ↓ low temperature cracking resistance.
SCB fracture test: significant effect for RAP content. 20% RAP → no impact on low temperature cracking
resistance. >20% RAP → significant ↓ in resistance to low
temperature cracking.
Impact of RAP on Mixtures’ Properties Low Temperature Cracking Resistance
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Hajj et al. (2007): RAP mixes with 0,15 and 30% RAP using TSRST
0
50
100
150
200
250
300
350
400
450
500
-30 -25 -20 -15 -10 -5 0 5
Temperature (oC)
Stre
ss (p
si)
LM32-1 LM32-2 LM32-3
Construction Variability
Impact of RAP on Mixtures’ Properties Low Temperature Cracking Resistance
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Hajj et al. (2007): RAP mixes with 0,15 and 30% RAP using TSRST
-45 -40 -35 -30 -25 -20 -15 -10 -5 0
0% RAP 15% RAP (Source I)
30% RAP (Source I)
15% RAP (Source II)
30% RAP (Source II)
15% RAP (Source III)
30% RAP (Source III)
TSR
ST F
ract
ure
Tem
p, °
C
Mixtures
PG 64-22 PG 64-28 NV
Note: Softer binders may have been used for 15 and 30% RAP
Impact of RAP on Mixtures’ Properties Low Temperature Cracking Resistance
Loria et al. (2011): High RAP test sections in Manitoba, Canada
25
-33 -31 -29
-32 -33 -31 -27
-34 -40 -35 -30 -25 -20 -15 -10
-5 0
F-0%-150 F-15%-150 F-50%-150 F-50%-200 L-0%-150 L-15%-150 L-50%-150 L-50%-200
Frac
ture
Tem
pera
ture
, °C
Mixture Type
Impact of RAP on Mixtures’ Properties Review of Selected Literature
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How Does RAP Affect Mixture Resistance to
Moisture Damage?
Impact of RAP on Mixtures’ Properties Resistance to Moisture Damage
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Puttaguanta et al. (1997): mixes with 0, 25 and 50% RAP using AASHTO T283 test
25 and 50% RAP → significant ↑ in moisture resistance.
Property Virgin mix RAP mix Allowable
limit 25% 50% Tensile strength ratio, % 59 81 91 > 80 Resilient modulus ratio, % 68 85 90 > 80
Impact of RAP on mixtures’ properties Resistance to Moisture Damage Li et al.(2004 ): 10 RAP mixtures with 0-40% RAP using
AASHTO T283 test.
TSR of 20 and 40% RAP mixes > 75% (criterion)
↑RAP→ ↑ TS (both wet and dry) but ↓TSR
28
Impact of RAP on mixtures’ properties Resistance to Moisture Damage Hajj et al. (2007): RAP mixtures with 0,15 and 30% RAP
using AASHTO T283 test.
29
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0 25 50 75
100 125 150 175 200 225 250
0% R
AP
15%
RA
P (S
ourc
e I)
30%
RA
P (S
ourc
e I)
15%
RA
P (S
ourc
e II)
30%
RA
P (S
ourc
e II)
15%
RA
P (S
ourc
e III
)
30%
RA
P (S
ourc
e III
) Tens
ile S
tren
gth
Rat
io (
TSR
)
Tens
ile S
tren
gth,
TS
at 7
7°F,
psi
PG64-22 Mixtures
Unconditioned Conditioned TSR
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Hajj et al. (2007): (cont’d)
30
0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%
0 25 50 75
100 125 150 175 200 225 250
0% R
AP
15%
RA
P (S
ourc
e I)
30%
RA
P (S
ourc
e I)
15%
RA
P (S
ourc
e II)
30%
RA
P (S
ourc
e II)
15%
RA
P (S
ourc
e III
)
30%
RA
P (S
ourc
e III
) Tens
ile S
tren
gth
Rat
io (
TSR
)
Tens
ile S
tren
gth,
TS
at 7
7°F,
psi
PG64-28 Mixtures
Unconditioned Conditioned TSR
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Hajj et al. (2007): (cont’d)
15 and 30% RAP → acceptable moisture resistance (TSR>70).
15 and 30% RAP → ↓ TS conditioned and unconditioned.
31
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Loria et al. (2011): High RAP test sections in Manitoba, Canada
32
117 127
171 165
132 143
189 169
101 115
155 170
113 123
153 161
73 75
117 122
70 75
124
93
0
50
100
150
200
F-0%-150 F-15%-150 F-50%-150 F-50%-200 L-0%-150 L-15%-150 L-50%-150 L-50%-200
Tens
ile S
treng
th at
77°F
, psi
Mixture Type 0 F-T 1 F-T 3 F-T
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Loria et al. (2011): High RAP test sections in Manitoba, Canada
33
86 91 90 100
86 86 81 95
63 59 68 74
53 53 66
55
0
40
80
120
F-0%-150 F-15%-150 F-50%-150 F-50%-200 L-0%-150 L-15%-150 L-50%-150 L-50%-200
Tens
ile S
treng
th R
atio
at 77°F
, %
Mixture Type 1 F-T 3 F-T
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Loria et al. (2011): High RAP test sections in Manitoba, Canada
34
335 406
677
546
280 306
487
335
225 314
487 534
248 276
470
295
222 250
397 478
215 241
335 279
100
200
300
400
500
600
700
F-0%-150 F-15%-150 F-50%-150 F-50%-200 L-0%-150 L-15%-150 L-50%-150 L-50%-200
|E*|
at 77°F
and
10 H
z, ks
i
Mixture Type 0 F-T 1 F-T 3 F-T
Impact of RAP on mixtures’ properties Resistance to Moisture Damage
Loria et al. (2011): High RAP test sections in Manitoba, Canada
35
67 77 72
98 89 90 97 88
66 62 59
88 77 79
69
83
0
25
50
75
100
F-0%-150 F-15%-150 F-50%-150 F-50%-200 L-0%-150 L-15%-150 L-50%-150 L-50%-200
E* R
atio
at 77°F
and
10 H
z, %
Mixture Type 1 F-T 3 F-T
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Field performance (After West R.) Washington State
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 37
WA-RD-98.1, 1986
Title: Hot Mix Recycling Evaluation in Washington
Authors: Peters, et al.
Scope: 16 projects, RAP contents from 8 to 79% (half ≥ 70%), projects ranged from 1.5 to 10 years old
(Source: www.morerap.us)
Field performance (After West R.) Washington State
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 38
Findings: WSDOT's initial two projects…are still performing
very well.
The early data indicates equally promising results for the 14 other projects.
(Source: www.morerap.us)
Field performance (After West R.) Louisiana
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 39
LTRC Report No. 216, April 1995
Title: Evaluation of Recycled Projects for Performance
Scope: 10 projects, RAP content: 20 to 50%, data covered a six to nine years, evaluated pavement condition ratings, serviceability, structural analysis, and mix and binder properties
(Source: www.morerap.us)
Field performance (After West R.) Louisiana
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 40
Findings: Pavements containing RAP performed similarly to
conventional mixtures for a period of six to nine years of service life
Pavements with RAP exhibited slightly more distress with respect to longitudinal cracking
The substitution of up to 15 % [RAP in wearing courses] can provide acceptable performing pavements as long as the 12,000 poise viscosity limitation is maintained.
(Source: www.morerap.us)
Field performance (After West R.) Connecticut
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 41
Report No.: FHWA-CTRD-647-4-87-1
Title: Performance Evaluation of Hot Mixed Recycled Pavement –Route 4, Burlington
Authors: Ganung and Larsen
Scope: conventional and 30% RAP, performance compared at 6 years of service
(Source: www.morerap.us)
Field performance (After West R.) Connecticut
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 42
Findings: No rutting was detected
Roughness was low
Extracted asphalt viscosities were higher for recycled versus control, possibly explaining for the greater cracking on the recycled
This condition was reversed on the overlaid sections
(Source: www.morerap.us)
Field performance (After West R.) Georgia
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 43
TRR 1507, 1995
Title: Performance of Recycled Hot-Mix Asphalt Mixtures in Georgia
Authors: Kandhal, et al.
Scope: Detailed comparison of 5 pairs of recycled versus control projects, followed by comparison of a larger set of control and recycled HMA projects. RAP contents range from 10 to 25%
(Source: www.morerap.us)
Field performance (After West R.) Georgia
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 44
Findings: For the 5 paired comparisons, there was no rutting,
raveling, or fatigue cracking in either the recycled or conventional sections.
Comparison of recycled vs. conventional mixes on 15 projects indicated the RAP mixes performed equal to or better than the virgin mixes.
(Source: www.morerap.us)
Field performance (After West R.) California
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 45
Title: Comparative Analysis of Long-Term Field Performance of Recycled Asphalt in California Environmental Zones, TRB 2008
Authors: Zaghloul and Holland
Scope: 60 RAP sections (up to 15% RAP) in 3 climatic zones in CA, evaluations at 5 to 9 years of service, rated by Structural Service Life, Distress Service Life, and Roughness Service Life
(Source: www.morerap.us)
Field performance (After West R.) California
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 46
Findings: Performance of RAP pavements differs for the three
climatic zones
North Coast climatic zone –Excellent to good performance of pavements with RAP
Mountain climatic zone –structural performance was marginal, but distress performance was poor
Desert climatic zone –Structural performance was good but distress performance was poor
(Source: www.morerap.us)
Field performance LTPP – Specific Pavement Study 5
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West et al. (2011) compared statistically the performance of virgin to 30% RAP mixes using 18 test projects build as part of SPS-5 .
Seven different type of distresses were examined.
Overlay mixes with 30% RAP perform as well as virgin mixes in terms of IRI, rutting, block cracking and raveling.
About a third of the projects had more longitudinal cracking or transverse cracking in the overlays containing RAP.
Field performance
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 48
More data available in literature documenting field performance of RAP mixes…
Keys to Managing RAP Variability West R. (2009), Better Roads
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1. Avoid Contamination: Contamination can occur from dumping general road debris with dirt
and vegetation on the pile, including milled-up paving fabrics in the pile, …
2. Mix as You Feed: Randomly dig into different areas of the pile so that the material
going into the crusher at any time gets mixed up and is not just from one place in the pile.
3. Don’t Over-Crush: The majority of contractors crush all RAP to a single maximum size,
such as minus 1/2-inch, or minus 5/8-inch, so that the crushed RAP can be used in a wide range of mixes from black base to surface mixes. The price paid for this convenience is that as larger aggregate particles in the RAP get crushed, more dust is generated. The excess dust will often limit how much of the RAP can be used in a new mix design.
Keys to Managing RAP Variability West R. (2009), Better Roads
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 50
4. Fractionating: Screening of RAP into two or more sizes. Couple of benefits to fractionating RAP and also additional
costs with the practice. Primary benefit is that it provides much greater flexibility in
designing mixes. In general, it is easier to use more total RAP in a mix when it is fractionated compared to a crusher-run RAP
5. Stop Processing RAP When it Rains: RAP stockpiles produced during a heavy rains may change in
gradation affecting mix properties. It makes sense that RAP will not screen as efficiently when it is wet because the material sticks together more and the screens tend to clog up or blind.
Keys to Managing RAP Variability West R. (2009), Better Roads
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 51
6. Blend Again When Moving: Usually, after processing RAP through a crushing system and/or
fractionation unit, the new stockpile(s) will have to be moved from the processing location to another location closer to the asphalt plant’s cold feed bins.
Contractors want to avoid moving materials any more than needed because it adds cost to the materials, but moving the processed RAP materials is an opportunity to further improve consistency.
Moving processed RAP should be done so as to further mix and blend the material as it is being loaded and unloaded.
However, sloppy moving practices can also lead to segregation, which will have the opposite effect on consistency.
Keys to Managing RAP Variability West R. (2009), Better Roads
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 52
6. Cover, Slope, and Pave: RAP stockpiles tend to retain a lot of moisture and that will
increase the drying and heating cost for superheating the virgin aggregate and limit the mix production rate.
As with virgin aggregates, paving under stockpiles provides an even foundation to minimize yard loss and contamination underlying materials.
Sloping the surface under the stockpile away from the side where the front-end loader picks up will allow rainwater to drain away, so that drier materials go into the plant.
BEST PRACTICES FOR RAP MANAGEMENT
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Best Practices for RAP Management NCHRP 9-46 (NCAT)
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 54
Keep large milling stockpiles separate, no additional processing to minimize P0.075
Multi-source stockpiles can be made into a consistent RAP through processing. Avoid over-crushing by screening material prior to crusher.
Variability guidelines should be used rather than method specifications for processing
Fractionation is helpful for mix designs with high RAP contents Sampling & testing frequency should be consistent with
aggregate QC (typically 1 per 1000 tons of RAP) Use a loader to build mini-stockpiles for sampling RAP aggregate can be recovered for testing using solvent
extraction or ignition method.
References
09/30/2012 University of Nevada, Reno, www.wrsc.unr.edu 55
Puttagunta, R., Oloo, S. Y., and Bergan, A. T. (1997). “A Comparison of the Predicted Performance of Virgin and Recycled,” In Candian Journal of Civil Engineering, Vol. 24, pp. 115-121. Puttaguanta
McDaniel, R. S., Soleymani, H., Anderson, R. M., Turner, P., and Peterson, R. (2000). “Incorporation of Reclaimed Asphalt Pavement in the Superpave System,” NCHRP 9-12, National Cooperative Highway Research Program, Transportation Research Board, National Research Council.
Li, X., Clyne, T. R., and Marasteanu, M. O. (2004). “Recycled Asphalt Pavement (RAP) Effects on Binder and Mixture Quality,” Report No. MN/RC – 2005-02, Minnesota DOT, Research Services Section.
McDaniel, R. S. (2006). Summary of State Specifications on RAP, North Central Superpave Center, November. Hajj, E. Y., Sebaaly, P. E., Shrestha, R. (2007). “A Laboratory Evaluation on the Use of Recycled Asphalt
Pavements in HMA Mixtures,” Final Report, Regional Transportation Commission. Xiao, F., Amirkhanian, S., and Juang, C. H. M. (2007). “Rutting Resistance of Rubberized Asphalt Concrete
Pavements Containing Reclaimed Asphalt Pavement Mixtures,” In Journal of Materials in Civil Engineering, Vol. 19, No. 6, June 1, pp.475-483.
Loria, L., Hajj, E. Y., Sebaaly, P. E., Barton, M., Kass, S., and T. Liske. “Performance Evaluation of Asphalt Mixtures with High Recycled Asphalt Pavement Content,” Transportation Research Record: Journal of the Transportation Research Board, No. 2208, Vol. 2, , Washington, D.C., 2011, pp. 72–81.
Li, X., Marasteanu, M. O., Christopher W., and Clyne, T. R. (2008). “Effect of RAP (Proportion and Type) and Binder Grade on the Properties of Asphalt Mixtures,” In Transportation Research Board 86th Annual Meeting Compendium of Papers CD-ROM, TRB, National Research Council.
… VISIT www.morerap.us