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

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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.

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slide1

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

slide2

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
slide3

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
slide6

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%
slide9

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)
slide10

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)
slide11

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; Mrfurther increased with additional fly ash and curing time (Carmago)
slide12

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)
slide13

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)
slide14

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
slide15

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
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 course1

35

30

25

20

Number of Responses

15

10

5

0

RAP

RCA

RPM

Material Type

Which of the following recycled materials do you use as a granular base course?
when are the recycled materials used
When are the recycled materials used?

Number of Responses

Total Responses: 36

when are the recycled materials used1
When are the recycled materials used?

Number of Responses

Recycled Asphalt Pavement (RAP)

Total Responses: 26

when are the recycled materials used2
When are the recycled materials used?

Number of Responses

Recycled Concrete Aggregate (RCA)

Total Responses: 31

when are the recycled materials used3
When are the recycled materials used?

Number of Responses

Recycled Pavement Material (RPM)

Total Responses: 18

in a given year how much of the recycled material do you use
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 use1
In a given year, how much of the recycled material do you use?

Number of Responses

Recycled Asphalt Pavement (RAP)

Total Responses: 23

in a given year how much of the recycled material do you use2
In a given year, how much of the recycled material do you use?

Number of Responses

Recycled Concrete Aggregate (RCA)

Total Responses: 29

in a given year how much of the recycled material do you use3
In a given year, how much of the recycled material do you use?

Number of Responses

Recycled Pavement Material (RPM)

Total Responses: 18

how long have you been using the recycled materials
How long have you been using the recycled materials?

Number of Responses

Total Responses: 34

how long have you been using the recycled materials1
How long have you been using the recycled materials?

Number of Responses

Recycled Asphalt Pavement (RAP)

Total Responses: 26

how long have you been using the recycled materials2
How long have you been using the recycled materials?

Number of Responses

Recycled Concrete Aggregate (RCA)

Total Responses: 29

how long have you been using the recycled materials3
How long have you been using the recycled materials?

Number of Responses

Recycled Pavement Material (RPM)

Total Responses: 20

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

Number of Responses

Total Responses: 32

slide32
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

slide33
Which of the following aggregate quality tests for shear strength do you perform on the material prior to placement?
slide34
Which of the following aggregate quality tests for toughness do you perform on the material prior to placement?

Number of Responses

Total Responses: 21

slide35
Which of the following aggregate quality tests for toughness do you perform on the material prior to placement?
slide36
Which of the following aggregate quality tests for durability do you perform on the material prior to placement?

Number of Responses

Total Responses: 12

slide37
Which of the following aggregate quality tests for durability do you perform on the material prior to placement?
responses for the following aggregate quality tests were inconclusive
Responses for the following aggregate quality tests were inconclusive
  • Stiffness
  • Frost Susceptibility
  • Permeability
  • Mineralogical Composition
  • Particle Geometric Properties
slide39

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
slide40

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
slide41

Conclusions

  • Overall:
  • Data regarding structural qualities of aggregates is limited
  • Recommend development of database of such properties for recycled materials
slide42

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?
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