THE CHALLENGES AND BENEFITS OF USING RECYCLED ASPHALT PAVEMENT (RAP) MATERIAL

Transcription

1 THE CHALLENGES AND BENEFITS OF USING RECYCLED ASPHALT PAVEMENT (RAP) MATERIAL Dave Van Deusen, PE, MnDOT Chris DeDene, PhD, PE, AET 2018 Mn Transportation Conference February 28, American Engineering Testing, Inc.

2 THE BENEFITS OF COLD CENTRAL PLANT RECYCLING (CCPR) OF ASPHALT PAVEMENTS Chris DeDene, PhD, PE 2018 Mn Transportation Conference February 28, American Engineering Testing, Inc.

3 NRRA RESEARCH CONTRACT AET Hired to analyze CCPR pavement test section at MnRoad Develop a survey for NRRA members on CCPR state of practice Look at CCPR mix-design process Recommend laboratory tests Evaluate CCPR cost with CIR and HMA Perform laboratory testing on MnROAD materials IDT, DCT, SCB, Hamburg, E*, FTIR Analyze lab testing, field performance, and MnDOT field tests

4 COMPARISON TO OVERLAYS CCPR utilizes RAP stockpile material or project millings CCPR has a lower structural coefficient, therefore a thicker overall section is needed For some projects, CCPR may be a more cost-effective rehabilitation alternative After placing, traffic can drive on the mat the same day however it must cure before the final surface can be placed Disrupts existing crack pattern in pavement 10x reduction in reflective cracking (WisDOT)

5 CCPR PROS AND CONS Pros Removes surface distresses Breaks up crack pattern in pavement Retards reflective cracking 20 year design Can be done in urban or rural areas Let savings vs. Mill and overlay 36% MnDOT CIR HWY % WisDOT CIR Cons Does not repair subgrade problems Retains the distresses and any material problems in the lower portion of the bituminous layer Must wait before placing the final surface 2018 American Engineering Testing, Inc.

6 MIX DESIGN Ensures the material will work Ensures the right amount of additive is used Allows identification of alternatives Not all oil foams correctly Not all binders will meet specifications Allows possibility for fall back position Variability in pavement thickness Wetter roadway than planned on

7 MIX DESIGN PROCEDURE Obtain samples from the RAP source being used Need a consistent RAP source Typically a 3 or 4 point mix design ( % oil) Optimize oil content based on test parameters Optimum moisture content Air voids Indirect tensile strength TSR (60-100%) Resilient modulus Marshall stability Critical cracking temperature (Low temperature) Hamburg test

8 PAVEMENT DESIGN Pavement Design Methods Structural Coefficient (α) Gravel Equivalency (GE) Hot Mix Asphalt Cold Recycled Also: MnPAVE (Design Modulus) Soil Factor Design AASHTO

9 OTHER CONSIDERATIONS Fractionating RAP More consistent end product Level of aging in RAP Other tests may provide better results than stability IDT, DCT, SCB, Hamburg, E*

10 GOOD CCPR CANDIDATES Few to no subgrade problems Little to no stripping issues in lower portion Existing asphalt thickness Needs to support the milling equipment Need a consistent RAP source 2018 American Engineering Testing, Inc.

11 PROJECT SELECTION Visual assessment of the pavement surface Historical review Geotechnical evaluation Pavement distress evaluation Rehabilitation selection Economic analysis Pavement design

12 PROJECT SELECTION Visual assessment of the pavement surface Historical review Geotechnical evaluation Pavement distress evaluation Rehabilitation selection Economic analysis Pavement design

13 GEOTECHNICAL EVALUATION Identify the subsurface conditions to limit risk Design the project around the actual conditions Develop options and analyze the economics Discuss soils, groundwater and infiltration conditions

14 PAVEMENT CORES / SOIL BORINGS Pavement Cores / Soil Borings Analyze cores for stripping/delamination/deteriorated Verify layer thicknesses and calibrate GPR data Soil classification for strength determination, if desired Stripping Core #2 Core #3 Same Project Deteriorated

15 FALLING WEIGHT DEFLECTOMETER (FWD) Falling Weight Deflectometer Non-destructive test Tells you how strong the pavement system is

16 GROUND PENETRATING RADAR (GPR) Ground Penetrating Radar Non-destructive test Provides a picture of pavement subsurface Pavement thickness + Strength => Structure Number

17 EQUIVALENT PAVEMENT SECTIONS 2 Mill & Fill 4 Old Asphalt 12 Base Chip Seal 3 CCPR 3 Old Asphalt 12 Base Subgrade Subgrade Option A HMA Option B CCPR 2018 American Engineering Testing, Inc.

18 EQUIVALENT PAVEMENT SECTIONS 2 Mill & Fill 4 Old Asphalt 12 Base Subgrade ~$100,000/ Centerline Mile Chip Seal 3 CCPR 3 Old Asphalt 12 Base Subgrade ~$85,000/ Centerline Mile Option A HMA Option B CCPR 2018 American Engineering Testing, Inc.

19 IN SUMMARY: CIR has been shown to outperform traditional pavement rehab Reuses 100% RAP Can save money Engineering costs are cheap insurance

20 QUESTIONS? Chris DeDene, PhD, PE Phone: American Engineering Testing, Inc.

21 FTIR TESTING Specimens are exposed to broadband infrared light, which is either reflected or absorbed Analogous to visible light

22 FTIR TESTING Functional Groups of Interest Compound Name Functional Spectrum Range (cm -1 ) Groups Alkanes C-H Butadiene HC=CH 965 Sulfoxide S=O 1030 Aromatic C-H, CH 2 and Hydrocarbons CH 3 Aromatics C=C 1600 Carbonyl C=O 1700 Saturated Hydrocarbons C-H

23 FTIR TESTING 100% RAP sample is more aged than virgin sample

24 QC/QA Applications Admixtures? Different RAP %? FTIR APPLICATIONS Moisture Content Opening to traffic

25 PAVEMENT AND MATERIALS ASSESSMENT APPROXIMATE COSTS Estimates for engineering a 20 mile project in Minnesota: Item Coring Soil / pavement borings FWD w/ analysis GPR analysis Sampling & subgrade testing Mix Design Cost $100-$150/core $150-$200/boring $150-$200/mile $ /mile $1,500/project $5,000 - $8,000/mix Total Project $15,000 - $25,000 Costs will vary depending on many factors, especially mobilization and traffic control