Literature Search and Survey Report On
Recycled Asphalt Pavement and Recycled
Concrete Aggregate
PI: Tuncer B. Edil
Research Assistant: Gregory Schaertl
University of Wisconsin-Madison
April 2009
Materials
•
Some ambiguity exists regarding the nomenclature for Recycled
Asphalt Pavement Production.
•
A suggested nomenclature:
•
Recycled Asphalt Pavement (RAP)
• Removal and Reuse of Hot Mix Asphalt (HMA) Layer
•
Full Depth Reclamation (FDR)
• Removal and Reuse of HMA and Entire Base Course Layer
•
Recycled Pavement Material (RPM)
• Removal and Reuse of
• HMA and Part of the Base Course Layer
• HMA, the Entire Base Course Layer, and Part of the
Underlying Subgrade
•
These three materials are often collectively referred to as RAP
Materials
•
Recycled Concrete Aggregate (RCA)
• Product of demolition and reprocessing of existing concrete
structures (buildings, roads, runways, etc.)
• Cementitious coating increases water absorption
• Un-Hydrated cement in material can increase strength and
durability
• Produced by crushing only
• Particle size distribution depends on crushing methods
•
Recycled Asphalt Pavement (RAP)
• Product of removal and reprocessing of existing asphalt
pavement
• Bituminous coating reduces water absorption
• Produced by milling and crushing
• High fines due to milling and crushing in production
Typical Physical Properties of RAP
Physical Properties
1940 - 2300 kg/m3 (120 - 140 pcf)
Unit Weight
Moisture Content
Normal: Up to 5%
Maximum: 7 - 8%
Asphalt Content
Normal: 4.5 – 6%
Asphalt Penetration
Normal: 10 – 80% at 25°C (77°F)
Absolute Viscosity or Recovered
Normal: 4000 – 25000 poises at
Asphalt Cement
60°C (140°F)
Mechanical Properties
Compacted Unit Weight
1600 – 2000 kg/m3 (100 – 125 pcf)
100% RAP: 20 – 25%
California Bearing Ratio (CBR)
40% RAP and 60% Natural
Aggregate: 150% or Higher
Typical Physical Properties of RCA
Physical Properties
Specific Gravity
2.2 to 2.5 (Coarse Particles)
2.0 to 2.3 (Fine Particles)
2 to 6 (Coarse Particles)
Absorption
4 to 8 (Fine Particles)
Mechanical Properties
LA Abrasion Loss
20 to 45 (Coarse Particles)
Magnesium Sulfate Soundness
4 or Less (Coarse Particles)
Loss
Less than 9 (Fine Particles)
California Bearing Ratio (CBR)
94 to 148%
Summary of Material Gradations
•
RAP
• Fines (Passing #200 Sieve): 1 to 8%
• Average: 2.3% / Standard Deviation: 2.7%
• Coarse (Passing 3/4” Sieve): 92 to 100%
• Average: 95.0% / Standard Deviation: 3.8%
•
RPM
• Fines: 3 to 16%
• Average: 8.0% / Standard Deviation: 3.8%
• Coarse: 93 to 96%
• Average: 95.8% / Standard Deviation: 1.5%
•
RCA
• Fines: 3 to 8%
• Average: 5.1% / Standard Deviation: 1.7%
• Coarse: 50 to 100%
• Average: 82.4% / 14.8%
Maximum Dry Density and Optimum
Moisture Content of RAP and RPM
Material
Bejarano: Pulverized
Proctor Effort
(8)
Caltrans
CTM 216
Maximum Dry
Optimum Moisture
Density, kg/m3
Content, %
2332
5.5
Bennert RAP(3)
Standard
1872
5
Guthrie R1(6)
Modified
2083
5.6
Guthrie R2(6)
Modified
1842
5.8
Saeed RAP-LS-MS(9)
Standard
1988
6.3
Saeed RAP-GR-CO(9)
Standard
2015
10.3
Saeed RAP-GV-LA(9)
Standard
1978
5.4
Carmargo RPM(11)
Standard
2161
7.5
Wen et al(13)
Modified
2162
7.5
Maximum Dry Density and Optimum
Moisture Content of RCA
Maximum Dry
Optimum Moisture
Density, kg/m3
Content, %
Material
Proctor Effort
Bennert RCA(3)
Standard
1984
7.5
Modified
1830
9.7
Modified
2020
10.6
Saeed RCP-LS-IL(9)
Standard
1971
11
Saeed RCP-GV-LA(9)
Standard
1950
9
Saeed RCP-GR-SC(9)
Standard
1990
9.5
Kuo UCF(2)
Modified
1823
11.2
Kuo FDOT(2)
Modified
1839
12.1
Blankenagel
Demolition(5)
Blankenagel Haul
Back(5)
Summary of Moisture-Density Characteristics
• Pure aggregate had higher MDD than pure RAP or pure
RCA (Saeed)
• Compaction specimens prepared by Gyratory Compaction
(GCT) correlated to field measurements better than
specimens prepared by Proctor Compaction (PCT) (Kim)
• Increased RAP content in RAP-Aggregate blends led to
decreased Maximum Dry Density (MDD) and decreased
Optimum Moisture Content (OMC) (Guthrie, Kim, Bennert,
Saeed)
• RAP-Aggregate blends compacted by GCT showed no
decrease in MDD with increased RAP content (Kim)
• Increased RCA content in RCA-Aggregate blends led to
decreased MDD and increased OMC (Bennert, Saeed)
• Haul-back material had higher MDD and OMC than
demolition material (Blankenagel)
Summary of Strength Tests
• Static Triaxial Tests:
• Shear strengths of RAP and Aggregate were
comparable in magnitude for tests under varying
confining pressures (Bejarano)
• Shear strength greater for pure Aggregate than for
pure RAP or pure RCA (Bennert)
• Shear strength in RAP or RCA - Aggregate blends
decreased as RAP or RCA content increased (Bennert)
• CBR Tests:
• Shear strength in RAP – Aggregate blends decreased
as RAP content increased (Guthrie)
• RPM had lower strength than aggregates with similar
gradation (Camargo, Wen)
Summary of Stiffness Tests
Stiffness
• Resilient Modulus (Mr):
• Pure RAP and pure RCA specimens had a higher Mr than
pure aggregate tested at the same compaction level
(Bejarano, Bennert)
• RAP / RCA – Aggregate blends had increased Mr with
Increased RAP and RCA content (Bennert, Kim)
• Increased confining pressure for RAP-Aggregate blends
resulted in increased Mr and increased permanent
deformation (Kim)
• Pure aggregate and 50/50 RAP-Aggregate blends had
equivalent stiffness at low confining pressures; blended
material had greater stiffness at high confining pressures
(Kim)
• Increased compressive strength of RCA resulted in
increased Mr (Naatmadja)
• Plastic strains for RPM may be higher or lower than those of
conventional base aggregates (Camargo)
• Addition of Fly Ash to RPM increased Mr; Mr further
increased with additional fly ash and curing time (Carmago)
Summary of Stiffness Tests
Stiffness
Free-Free Resonant Column Test:
• The stiffness of RAP-Aggregate blends decreased
from 0-25% RAP and increased from 25-100% RAP.
Trend reversed after 72 hours drying: stiffness
increased from 0-25% RAP and decreased from 25100% RAP (Guthrie)
Summary of Other Tests
Moisture Susceptibility
• Tube Suction Tests:
• Moisture susceptibility in RAP-Aggregate blends increased
with increased RAP content (Guthrie)
• Dry density of RAP-Aggregate blends decreased with
increased RAP content (Guthrie)
Durability
• LA Abrasion Tests:
• Demolition material experienced higher material losses than
Haul-Back material (Blankenagel)
• Commercial RCA had a lower hardness compared to
laboratory manufactured RCA (Nataatmadja)
• Freeze-Thaw Tests:
• RCA experienced a 30 to 90% reduction in stiffness, and a 28
to 52% reduction in strength (Blankenagel)
• RPM and aggregate with and without fly ash experienced a
decrease in stiffness of less than 15%, with no consistent
effect for materials stabilized with fly ash (Camargo, Wen)
Conclusions
•
GCT specimens correlate more closely to field density
measurements than PCT specimens
•
Pure aggregate and 50/50 RAP/Aggregate blends had equivalent
stiffness at low confining pressures, but blends had greater
stiffness at high confining pressures
•
RAP and RCA have higher Mr than pure aggregate, but pure
aggregate has higher shear strength than RAP or RCA
•
Increased RAP and RCA content in aggregate blends results in
decreased shear strength and increased Mr
•
Plastic strains for RPM may be higher or lower than those of
conventional base aggregates
•
RPM shows better response than natural aggregate for similar
gradation and compaction tests
The Usage, Storage and Testing of
Recycled Materials – Results of Survey
PI: Tuncer B. Edil
Research Assistant: Gregory Schaertl
University of Wisconsin-Madison
April 2009
Which of the following recycled materials do
you use as a granular base course?
Number of Responses
Total Responses: 34
• Recycled Asphalt Pavement (RAP): 18 (53%)*
• Recycled Concrete Aggregate (RCA): 30 (88%)*
• Recycled Pavement Material (RPM): 17 (50%)*
*More than one response possible
Which of the following recycled materials do
you use as a granular base course?
35
Number of Responses
30
25
20
15
10
5
0
RAP
RCA
Material Type
RPM
When are the recycled materials used?
Number of Responses
Total Responses: 36
When are the recycled materials used?
Number of Responses
Recycled Asphalt Pavement (RAP)
Total Responses: 26
Stockpiled
and Used
Later, 11,
42%
Both, 14,
54%
Used in Place
Immediately1,
4%
When are the recycled materials used?
Number of Responses
Recycled Concrete Aggregate (RCA)
Total Responses: 31
Both, 11,
34%
Stockpiled
and Used
Later, 20,
63%
Used in
Place
Immediately,
1, 3%
When are the recycled materials used?
Number of Responses
Recycled Pavement Material (RPM)
Total Responses: 18
Stockpiled
and Used
Later, 6, 33%
Both, 7, 39%
Used in
Place
Immediately,
5, 28%
In a given year, how much of the recycled
material do you use?
Number of Responses
Total Responses: 33
In a given year, how much of the recycled
material do you use?
Number of Responses
Recycled Asphalt Pavement (RAP)
Total Responses: 23
Less than 1,000
Tons, 4, 18%
1,000 to 5,000
Tons, 0, 0%
More than
75,000 Tons, 12,
52%
5,000 to 10,000
Tons, 2, 9%
10,000 to
25,000 Tons, 4,
17%
50,000 Tons to
75,000 Tons, 1,
4%
25,000 Tons to
50,000 Tons, 0,
0%
In a given year, how much of the recycled
material do you use?
Number of Responses
Recycled Concrete Aggregate (RCA)
Total Responses: 29
More than
75,000 Tons, 8,
27%
Less than
1,000 Tons,
2, 7%
1,000 to 5,000
Tons, 6, 21%
50,000 Tons to
75,000 Tons, 2,
7%
5,000 to 10,000
Tons, 4, 14%
25,000 Tons to
50,000 Tons, 5,
17%
10,000 to
25,000 Tons, 2,
7%
In a given year, how much of the recycled
material do you use?
Number of Responses
Recycled Pavement Material (RPM)
Total Responses: 18
Less than 1,000
Tons, 1, 5%
More than
75,000 Tons, 4,
22%
1,000 to 5,000
Tons, 4, 22%
50,000 Tons to
75,000 Tons, 2,
11%
5,000 to 10,000
Tons, 3, 17%
25,000 Tons to
50,000 Tons, 1,
6%
10,000 to 25,000
Tons, 3, 17%
How long have you been using the recycled
materials?
Number of Responses
Total Responses: 34
How long have you been using the recycled
materials?
Number of Responses
Recycled Asphalt Pavement (RAP)
Total Responses: 26
Less than 1 Year,
0, 0%
1 to 2 Years, 0,
0%
More than 10
Years, 20, 77%
2 to 5 Years, 1,
4%
5 to 10 Years, 5,
19%
How long have you been using the recycled
materials?
Number of Responses
Recycled Concrete Aggregate (RCA)
Total Responses: 29
Less than 1
Year, 0, 0%
More than 10
Years, 18, 62%
1 to 2 Years, 0,
0%
2 to 5 Years, 4,
14%
5 to 10 Years,
7, 24%
How long have you been using the recycled
materials?
Number of Responses
Recycled Pavement Material (RPM)
Total Responses: 20
Less than 1
Year, 1, 5%
More than 10
Years, 12, 60%
1 to 2 Years, 0,
0%
2 to 5 Years, 4,
20%
5 to 10 Years, 3,
15%
Are any of the following tests used in
specifications for the material?
Number of Responses
Total Responses: 32
Are any of the following tests used in
specifications for the material?
30
26
Number of Responses
25
20
20
Grain Size Analysis: Dry
Sieve
Grain Size Analysis: Wet
Sieve and Hydrometer
16
15
Liquid Limit
11
10
5
5
0
Plastic Limit and Plasticity
Index
8
0
1
RAP
2
4
1 1
RCA
Material Type
RPM
Which of the following aggregate quality tests
for shear strength do you perform on the
material prior to placement?
Number of Responses
Total Responses: 11
Which of the following aggregate quality tests
for shear strength do you perform on the
material prior to placement?
5
4
Number of Responses
Static Triaxial Test
4
California Bearing Ratio
3
2
2
Dynamic Cone
Penetrometer w/
Lightweight Deflectometer
2
Resistance Value
11
1
0
0
11111
000
RAP
0
11
0
RCA
Material Type
000
RPM
Pre-Qualify with Los
Angeles Abrasion and
Sulfate Soundness (5
cycles):
Sand Equivelancy Test
Which of the following aggregate quality tests
for toughness do you perform on the material
prior to placement?
Number of Responses
Total Responses: 21
Number of Responses
Which of the following aggregate quality tests
for toughness do you perform on the material
prior to placement?
16
15
14
13
12
11
10
9
8
7
6
5
4
3
2
1
0
LA Abrasion
15
Aggregate Impact Value
Aggregate Crushing
Value
Aggregate Abrasion
Value
Micro-Deval
5
5
Durability Mill
2
1 1
000 0 00
RAP
2
1
00
11
00
RCA
Material Type
Gyratory Test
1
00
0000
Sulfate Soundness
RPM
Texas Wet-Mill (Similar
to Micro-Deval)
Which of the following aggregate quality tests
for durability do you perform on the material
prior to placement?
Number of Responses
Total Responses: 12
Which of the following aggregate quality tests
for durability do you perform on the material
prior to placement?
9
8
Number of Responses
8
7
Sulfate Soundness
6
5
Canadian FreezeThaw
4
Aggregate Durability
Index
3
3
2
Magnesium Sulfate
Soundness
2
1
1
0
0
RAP
1 1
0
0
0 0 0
RCA
RPM
Material Type
Responses for the following aggregate quality
tests were inconclusive
•
•
•
•
•
Stiffness
Frost Susceptibility
Permeability
Mineralogical Composition
Particle Geometric Properties
Conclusions
• RCA most commonly used material, followed by RAP and
RPM
• If RAP and RPM are combined, recycling of flexible
pavements is more common in terms of frequency and
quantity
• Following reclamation operations, it is more common for a
recycled material to be stockpile and used later than to be
used immediately after reclamation (relatively, RPM is
most likely to be used immediately after reclamation)
• RAP represents the greatest total tonnage used, followed
by RCA and RPM
Conclusions
Common Tests:
• Specification Compliance: Grain Size Analysis (Dry/Wet
Sieve), Plastic/Liquid Limit
• Shear Strength: California Bearing Ratio
• Aggregate Toughness: LA Abrasion
• Aggregate Durability: Sulfate Soundness
Less Common Tests:
• Stiffness: R-Value
• Permeability: Falling Head Test
• Mineralogical Composition: Petrographic Examination
• Particle Geometry: Percent of Fractured Particles Test or
Flat and Elongated Particles Test
Conclusions
Overall:
• Data regarding structural qualities of aggregates is limited
• Recommend development of database of such properties
for recycled materials
Discussion Points
• RAP nomenclature?
• Compaction specifications to be used in the tests?
• Need for structural properties, i.e., resilient modulus and
plastic strains?
• Aggregate quality test for toughness: LA abrasion?
• Aggregate quality test for durability: Sulfate soundness?
• Frost susceptibility: UW approach?