Literature Search and Survey Report On Recycled Asphalt Pavement and Recycled Concrete Aggregate

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

Unit Weight 1940 - 2300 kg/m3 (120 - 140 pcf)

Moisture ContentNormal: 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 Asphalt Cement

Normal: 4000 – 25000 poises at 60°C (140°F)

Mechanical Properties

Compacted Unit Weight 1600 – 2000 kg/m3 (100 – 125 pcf)

California Bearing Ratio (CBR)100% RAP: 20 – 25%

40% RAP and 60% Natural Aggregate: 150% or Higher

Typical Physical Properties of RCA

Physical Properties

Specific Gravity2.2 to 2.5 (Coarse Particles)

2.0 to 2.3 (Fine Particles)

Absorption2 to 6 (Coarse Particles)

4 to 8 (Fine Particles)

Mechanical Properties

LA Abrasion Loss 20 to 45 (Coarse Particles)

Magnesium Sulfate Soundness Loss

4 or Less (Coarse Particles)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 Proctor EffortMaximum Dry Density, kg/m3

Optimum Moisture Content, %

Bejarano: Pulverized (8)CaltransCTM 216

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

Material Proctor EffortMaximum Dry Density, kg/m3

Optimum Moisture Content, %

Bennert RCA(3) Standard 1984 7.5

Blankenagel Demolition(5)

Modified 1830 9.7

Blankenagel Haul Back(5)

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

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 25-100% 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 ResponsesTotal 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?

0

5

10

15

20

25

30

35

RAP RCA RPM

Material Type

Num

ber o

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pons

es

When are the recycled materials used?



Number of ResponsesRecycled Asphalt Pavement (RAP)

Total Responses: 26

Stockpiled and Used Later, 11,

42%

Used in Place Imme-diately1, 4%

Both, 14, 54%


Number of ResponsesRecycled Concrete Aggregate (RCA)

Total Responses: 31


63%

Used in Place Immediately, 1,

3%

Both, 11, 34%


Number of ResponsesRecycled Pavement Material (RPM)

Total Responses: 18


33%

Used in Place Imme-diately, 5, 28%

Both, 7, 39%

In a given year, how much of the recycled material do you use?




Total Responses: 23

Less than 1,000 Tons, 4, 17%

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%

More than 75,000 Tons, 12, 52%



Total Responses: 29


1,000 to 5,000 Tons, 6, 21%

5,000 to 10,000 Tons, 4, 14%

10,000 to 25,000 Tons, 2, 7%

25,000 Tons to 50,000 Tons, 5, 17%

50,000 Tons to 75,000 Tons, 2, 7%




Total Responses: 18


1,000 to 5,000 Tons, 4, 22%

5,000 to 10,000 Tons, 3, 17%

10,000 to 25,000 Tons, 3, 17%

25,000 Tons to 50,000 Tons, 1, 6%

50,000 Tons to 75,000 Tons, 2, 11%


How long have you been using the recycled materials?




Total Responses: 26

2 to 5 Years; 1; 4%

5 to 10 Years; 5; 19%

More than 10 Years; 20; 77%



Total Responses: 29

2 to 5 Years, 4, 14%

5 to 10 Years, 7, 24%

More than 10 Years, 18, 62%



Total Responses: 20

Less than 1 Year, 1, 5%

2 to 5 Years, 4, 20%

5 to 10 Years, 3, 15%

More than 10 Years, 12, 60%

Are any of the following tests used in specifications for the material?


Are any of the following tests used in specifications for the material?

RAP RCA RPM0

5

10

15

20

25

30

20

26

16

0

5

11

8

12

11

4

Grain Size Analysis: Dry Sieve

Grain Size Analysis: Wet Sieve and Hydrometer

Liquid Limit

Plastic Limit and Plasticity Index

Material Type

Num

ber o

f Res

pons

es

Which of the following aggregate quality tests for shear strength do you perform on the

material prior to placement?


Which of the following aggregate quality tests for shear strength do you perform on the

material prior to placement?

RAP RCA RPM0

1

2

3

4

5

0 0 0

2

4

2

1 1 11 1 1

0

1

00

1

00

1

0

Static Triaxial Test

California Bearing Ratio

Dynamic Cone Penetrometer w/ Lightweight Deflectome-ter

Resistance Value

Pre-Qualify with Los Ange-les Abrasion and Sulfate Soundness (5 cycles):

Sand Equivelancy Test

Texas Triaxial TestMaterial Type

Num

ber o

f Res

pons

es

Which of the following aggregate quality tests for toughness do you perform on the material

prior to placement?


Which of the following aggregate quality tests for toughness do you perform on the material

prior to placement?

RAP RCA RPM0123456789

10111213141516

5

15

5

0 0 00 0 001 11

2 2

0 0 01

0 001

001

0

LA Abrasion

Aggregate Impact Value

Aggregate Crushing Value

Aggregate Abrasion Value

Micro-Deval

Durability Mill

Gyratory Test

Sulfate Soundness

Texas Wet-Mill (Similar to Micro-Deval)Material Type

Num

ber o

f Res

pons

es

Which of the following aggregate quality tests for durability do you perform on the material

prior to placement?


Which of the following aggregate quality tests for durability do you perform on the material

prior to placement?

RAP RCA RPM0

1

2

3

4

5

6

7

8

9

2

8

3

0 0 0

1 1

00

1

0

Sulfate Soundness

Canadian Freeze-Thaw

Aggregate Durability Index

Magnesium Sulfate Soundness

Material Type

Num

ber o

f Res

pons

es

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?

Documents

Literature Search and Survey Report On Recycled Asphalt Pavement and Recycled Concrete Aggregate