Literature Search and Survey Report On Recycled Asphalt
- Slides: 42
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/m 3 (120 - 140 pcf) 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/m 3 (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/m 3 Content, % 2332 5. 5 Bennert RAP(3) Standard 1872 5 Guthrie R 1(6) Modified 2083 5. 6 Guthrie R 2(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/m 3 Content, % 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 Material Proctor Effort Bennert RCA(3) 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 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 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 Immediately 1, 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, 17% 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%
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% 50, 000 Tons to 75, 000 Tons, 2, 7% 25, 000 Tons to 50, 000 Tons, 5, 17% Less than 1, 000 Tons, 2, 7% 1, 000 to 5, 000 Tons, 6, 21% 5, 000 to 10, 000 Tons, 4, 14% 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% 25, 000 Tons to 50, 000 Tons, 1, 6% 5, 000 to 10, 000 Tons, 3, 17% 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 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 More than 10 Years, 18, 62% 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% 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 11 1 0 2 0 11111 000 RAP 0 11 0 RCA Material Type Dynamic Cone Penetrometer w/ Lightweight Deflectometer Resistance Value 000 RPM Pre-Qualify with Los Angeles Abrasion and Sulfate Soundness (5 cycles):
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 Freeze. Thaw 4 Aggregate Durability Index 3 2 1 0 3 Magnesium Sulfate Soundness 2 1 0 RAP 1 1 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?
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