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Responsible Use of RAP
Partners in Quality Road Tour
London ‐ May 3, 2016 ; Toronto ‐May 5, 2016; Ottawa ‐May 10, 2016 ; Sudbury ‐May 12, 2016
Tom Dziedziejko, CETDirector QualityAecon Infrastructure
Responsible Use of RAP
• To Produce Quality Pavements • Understand Impacts of Recycled
Materials Used In Production
• Impacts on Performance
• Understand Current Practice and Adapt As Required
• Recycling Practice Changing as Experience Increases
• Understand Limitations of Current Knowledge Base
Hot Mix Asphalt Recycling in Ontario
• Hot Mix plants in Ontario produce over 14Million tonnes of hot mix annually
• RAP Most Recycled material
• Four out of every five tonnes of asphalt pavement removed during widening and resurfacing projects is re‐used
Why Recycle• Advantages
• Environmentally Responsible• Saves Landfill
• Conserves Natural Resources• Extends the life of aggregate and asphalt
sources• Improves mixture performance
• Reduced Rutting• Reduced moisture damage
• Disadvantage:• At Higher Percentages ‐Cracking Resistance
Decreased
Why RecycleCost of Asphalt Cement
Financial Benefit of Recycling
% RAP 0% 10% 20% 25% 30% 40%
AC Type 58‐28 58‐28 58‐28 52‐34 52‐34 52‐34
AC Cost $ 27.50 $ 25.30 $ 23.10 $ 22.80 $ 21.66 $ 19.38
Aggregate Cost $ 14.25 $ 13.35 $ 12.45 $ 12.00 $ 11.55 $ 10.65
RAP Cost $ ‐ $ 0.90 $ 1.80 $ 2.25 $ 2.70 $ 3.60
Total Cost $ 41.75 $ 39.55 $ 37.35 $ 37.05 $ 35.91 $ 33.63
Assumed cost per Tonne; AC Cost 58‐28 = $520, AC Cost 52‐34 = $570, Aggregate Cost = $15, RAP = $9
Financial Benefit of Recycling% RAP 0% 10% 20% 25% 30% 40%
% RAP 0% 10% 20% 25% 30% 40%
AC Type 58‐34 58‐34 58‐34 52‐40 52‐40 52‐40
AC Cost $ 31.25 $ 28.75 $ 26.25 $ 25.00 $ 23.75 $ 21.25
Aggregate Cost $ 14.25 $ 13.35 $ 12.45 $ 12.00 $ 11.55 $ 10.65
RAP Cost $ ‐ $ 0.90 $ 1.80 $ 2.25 $ 2.70 $ 3.60
Total Cost $ 45.50 $ 43.00 $ 40.50 $ 39.25 $ 38.00 $ 35.50 Assumed cost per Tonne; AC Cost 58‐34= $625, AC Cost 52‐40 = $625 Aggregate Cost = $15, RAP = $9
Specifications
• OPSS 1151
• OPSS 1150
Specifications
Specifications
• SP111F11
Specifications
Development of Recycling Guidelines
• 1987 through 1993 ‐ Strategic Highway Research Program (SHRP) ‐ Developed Superpave System• Provisions for Use of RAP not addressed in mix
design procedures developed.
• NCHRP Project 9 – 12 “Incorporation of Reclaimed Asphalt Pavement in the Superpave System” initiated.
• 2001• NCHRP Report 452: “Recommended Use of
Reclaimed Asphalt Pavement in the SuperpaveMix Design Method, Technician's Manual.
• Mix design procedures for mixtures using of RAP
Development of Recycling Guidelines
• Procedures Developed• Characterization of Aged RAP to determine
Critical Temperatures• High, Medium and Low
• Test Method Proposed for recovery and grading of Aged Asphalt in pavement being recycled
• Guidance for development of Blending Charts
• Provided general Guideline on Grade Changes based on Grade of Aged AC.
Evolving Recycling Guidelines • NCHRP 452 Recommended Procedures for Grading Aged RAP
• Since Implementation Experience Shows Results Unreliable
• Between Lab and Within Lab Variability Very High
• Toluene Solvents used in Current procedure Highly Flammable
• Explosion proof equipment required
• Results represent total AC in RAP but Not All RAP AC Blends with New AC
• Degree of Blending is mix dependent
• Comparison of properties of Samples made with different amounts of AC and RAP
• Low Blend Ratio mixes show high percentage of blending
• High Blend Ratio mixes show lower percentage of blending
• Some Jurisdictions assume blending as low 60%
• 80% to 95% more reasonable
Evolving Recycling Guidelines • Guideline: Publication No. FHWA‐HRT‐11‐021 (2011)
• Basic Approach similar to NCHRP 452 but recognizes limitations
• Aged RAP Characterization not straight forward
• Recommends Regional Development of RAP Characterization.
• Addresses Alternate Bituminous Materials and New processes used in Pavement Recycling
• Shingle Tabs, RAP Fractionation, RAS
• % Binder Replacement vs % RAP
• Importance of Grade Change with increased RAP
• Proper Characterization of Aged AC in RAP
• Careful Consideration if >25% Binder Replacement
• Ontario data for RAP Grading Limited and Variable
• Poor correlation from available test methods.
• Limited sampling gives poor confidence in result accuracy.
Impact of RAP on Blend AC Low Critical Temperature
Impact of RAP on Blend AC Low Critical Temperature
• Low Critical Temperature of AC Affected by Addition of RAP • Impact to Low Temperature inconsequential with less than 20% RAP used.
• High RAP Mixes require Grade Change to maintain protection against low temperature cracking.
• OPSS 1150, OPSS 1151, SP111F11 all have similar requirements
Grade Requirements for Major Cities in Ontario
FHA ‐ LTPPBindVersion 3.1 Uses local historical temperature data to calculate PG grade requirements. Reliability = 98%
City
Surface Mix Critical Low Tempeature
Critical Temperature at 50mm
below surface
Specified Low Temperature Base AC Grade
Orangeville ‐27.5 ‐24.5 ‐28Toronto (Zoo) ‐25.8 ‐22.8 ‐28Woodbridge ‐26.7 ‐23.7 ‐28Kingston ‐28.6 ‐25.6 ‐28London ‐24.2 ‐21.2 ‐28Muskoka ‐33.3 ‐30.3 ‐34Ottawa ‐29.1 ‐26.1 ‐34Subdbury ‐33.3 ‐30.3 ‐34Kenora ‐36.5 ‐33.5 ‐34Timmins ‐37.9 ‐34.9 ‐34
Importance of Following Grade Change Guidelines
• Low percentage of RAP results in minimal impact to pavement performance.
• High Volume RAP ‐Grade Change Specifications
• Aged RAP with Critical Low Temp = ‐16.
% RAP AC Blend0 ‐3410 ‐32.220 ‐30.425 ‐29.530 ‐28.635 ‐27.740 ‐26.850 ‐2560 ‐23.2
% RAP AC Blend0 ‐3410 ‐32.220 ‐30.425 ‐3430 ‐32.835 ‐31.640 ‐30.450 ‐2860 ‐25.6
No Grade ChangeWith Grade Change
Base Grade ‐34/ Zone 2
Importance of Following Grade Change Guidelines
• High Volume RAP ‐Grade Change Specifications
• Aged RAP with Critical Low Temp = ‐16.
% RAP AC Blend0 ‐2810 ‐26.820 ‐25.625 ‐2530 ‐24.435 ‐23.840 ‐23.250 ‐2260 ‐20.8
% RAP AC Blend0 ‐2810 ‐26.820 ‐25.625 ‐29.530 ‐28.635 ‐27.740 ‐26.850 ‐2560 ‐23.2
No Grade ChangeWith Grade Change
Base Grade ‐28 / Zone 3
Alternate Processes and Sources for Recycled AC in Hot Mix
• Original NCHRP Project 9‐12
• % RAP Limits Based on recycling whole RAP
• Growth of Recycling of Alternate Materials has Changed Balance
• Using % RAP Guidelines Can result in:
• Excess Recycled AC in High RAP Mixture
• Exceeding Critical Low temp in High RAP Mixtures
• Low Temperature Cracking
• Unnecessarily Restricts RAP Use
• Materials with Lower than typical AC content
Alternate Processes and Sources for Recycled AC in Hot Mix
• RAP Fractionation• During processing RAP is screened into different sizes
• Can be 2 or 3 different sizes
• Each size fraction has different AC content
• Fine fraction may have 20% more AC than Non Fractionated RAP
• Shingle Tabs / Cut offs• New Material cut from shingles during manufacture
• High AC content – 20 % to 30 %
• Not paving grade Asphalt• Highly Modified blown asphalt typically used
• RAS – Recycled Asphalt Shingles• OPSS does not allow RAS in Hot Mix
• Ground aged shingles
• AC is highly oxidized
• High Critical low temp (about 1C) High AC content 15% to 20%
% Binder Replacement vs. % RAP
RAP Fractionation, Shingle Tabs / Cut offs, RAS
• AC contents are different than AC content of typical RAP.
• Specifying Recycling Ratio based on %RAP does not work for these and similar materials.
• % Binder replacement calculates amount of Recycled AC in mix based on amount of AC in recycled material:
Where:A = RAP percent binder content.B = RAP percent in mixture.C = Total percent binder content in mixture.
% Binder Replacement vs. % RAP • Examples
• Typical 5% AC Recycled mix has 20% RAP, and RAP has 5.0% AC
• Binder Replacement = 20%
• Fractionated Fine RAP has 6.0% , AC Recycling Ratio to have equivalent 20% Binder Replacement
• 17%
• Fractionated Coarse RAP has 4.0% AC. Recycling Ratio to have equivalent 20% Binder Replacement
• 25%
• Using % RAP there is potential to:
• Excess Aged AC in mix with Fine RAP
• Unnecessarily restrict amount of AC from Coarse RAP
Use of RAS
• RAS is not allowed in Hot Mix• Some suppliers are selling some product indicating that
some is being used in hot mix.
• Associate membership application recently rejected.
• Low Critical Temp on RAS samples +1C.
• Significant impact on Low Temp Grade of Blended AC• 2% RAS = 7% Binder Replacement
• Same Low Critical Temperature Impact as 20% RAP)
• 6% RAS = 22% Binder Replacement
• Same Low Critical Temperature Impact as +50% RAP
• RAS use requires grade changes
% RAS
% Binder Replmt'
AC Blend
0 0% ‐28
1 4% ‐26.84
2 7% ‐25.97
4 14% ‐23.94
6 22% ‐21.62
8 29% ‐19.59
10 36% ‐17.56
Use of RAS• RAS is not allowed in Hot Mix
• Some suppliers are selling some product indicating that some is being used in hot mix.
• Associate membership application recently rejected.
• Low Critical Temp on RAS samples +1C.
• Significant impact on Low Temp Grade of Blended AC
• 2% RAS = 7% Binder Replacement
• Lower Critical Temperature Impact as 20% RAP)
• 4% RAS = 14% Binder Replacement
• Same Low Critical Temperature Impact as +40% RAP
• RAS use requires grade changes
% RAS% Binder Replmt'
AC Blend
0 0% ‐34
1 4% ‐32.6
2 7% ‐31.55
4 14% ‐29.1
6 22% ‐26.3
8 29% ‐23.85
10 36% ‐21.4
Binder Availability • RAP AC does not necessarily Blend completely with new AC
• Less than 100% of AC blends in high RAP mixes
• Exact amount varies with each mix
• Reduced Effective AC Negatively Impacts Pavement Performance• Fatigue Cracking / Raveling etc.
• RAP: Assumed Binder Availability= 85%
• Impact at Low AC minimal.
% AC in RAP % AC Design % RAP Effective AC %
4.5 5 20 4.87
4.5 5 25 4.83
4.5 5 30 4.80
4.5 5 35 4.76
4.5 5 40 4.73
Binder Availability– Using RAS• Significant impact with higher AC Replacement
• Example:
• RAS: Assumed Binder Availability= 75%
• FHWA Mixture ETG ‐ RAS Taskforce
•April 2016 Recommendation
•Increase Minimum VMA 0.1% for each % of RAS
% AC in RAS % AC Design % RAS Effective AC %
18 5 2 4.69
18 5 4 4.37
18 5 6 4.01
18 5 8 3.70
18 5 10 3.38
Conclusions• Mixes with Low Binder Replacement (<20%)
• Impact on Low Temperature Grade is Typically Inconsequential
• Mixes with High Binder Replacement Need Special Consideration • Virgin AC Grade Must be Changed as appropriate
• Characterization of RAP / RST / RAS• Understanding Critical Low Temperature of Aged AC is
necessary.
• Available Test Methods provide information on Aged AC when testing a limited number of samples but results should be looked at critically .
• Establishing Regional RAP Characterization allows increase in samples tested and increases confidence.
Conclusions• Regardless of Specified Maximum Recycling Ratio Use Special
Considerations when using a Binder Replacement Ratio of more than 25%.
• Blending Charts Should be used:• 100% Blending of Aged and New AC does not occur with High
Recycling Ratio’s
• Test Method for Grading RAP AC is flawed ‐ But..
• The Concept of Blending Charts is Reasonable given understanding of the Aged AC being used.
• Consider Binder Replacement when determining Recycling Ratio• Using current % RAP Specifications can result in
• Excessive Recycled AC in mix
• i.e.: Recycled Materials with AC content higher than typical RAP
• Restriction of amount of Recycled Material Used
• i.e.: Recycled Materials with AC content lower than typical RAP
•
Conclusions
• Effective AC Content of Mix is reduced at High Recycling Ratio’s
• Actual binder availability from RAP is based on properties of the aged AC and New AC in mix.
• Binder Availability and amount of reduction of Effective AC % in mix depends on the amount of blending.
• Reduced AC causes increased fatigue cracking
• FHWA recommends increase in VMA for RAS use
• Should similar adjustements be considered for RAP??
Thank You
•Questions??