Mix Design: Changing the Recipe Book

Transcription

1 Mix Design: Changing the Recipe Book DAVE NEWCOMB AND FUJIE ZHOU TEXAS A&M TRANSPORTATION INSTITUTE March 22-24, 2016 Nashville, TN

2 How have asphalt materials changed? Age of Uncomplicated Almost all unmodified asphalt Recycling in 1970s 90s: Low amounts of RAP Almost all dense-graded mixes Marshall and Hveem become displaced Volumetric design works OK Recycled as Roads

3 How have asphalt materials changed? PG System in full swing Refineries change asphalt gets expensive Warm mix PPA to make high PG REOB to make low PG Polymers More RAP and RAS Smaller NMAS SMAs

4 Refinery Changes ROSE (Residuum Oil Supercritical Extraction) Cokers More terminal blenders

5 REOB and PPA Recycled Engine Oil Bottoms (Steve Escobar) Most common additive High flash point, high visc. index, low wt. loss, low visc., etc. Also paraffinic Polyphosphoric Acid (TRB Circular E-C160) Commonly used additive High visc., no free H 2 O, does not oxidize asphalt or lower m-value May react with anti-strip Both are dependent upon asphalt chemistry!

6 What Does This Mean? Asphalt Asphaltenes Aromatics Resins Saturates Most Reactive Least Reactive

7 RAP and RAS Resource Conservation Energy Conservation Price Stabilization

8 Greenhouse Gases Pavement construction very low compared to vehicle operations 82 MT for pavements out of 1600 MT for all transportation Using RAP/RAS reduces CO 2 e about the same amount as removing 270,000 vehicles 3/17/2015 WOA High Binder Replacement Webinar 8

9 Cost Savings Reference Material Cost Savings Zhou et al. (2006) 5% RAS 2 5% Brock (2008) 20% RAP 50% RAP >16% >40% NCAT (Willis et al., 2012)* 25% RAP 50% RAP 14 20% 29 35% * Used different amounts and stiffness of virgin binders used in mixtures. 3/17/2015 WOA High Binder Replacement Webinar 9

10 RAP/RAS and PG RAP/RAS binder too stiff?

11 The Need Volumetric Mix Design Does it make sense when our materials have changed so much? Balanced Mix Design Max. set by AC for 98% density Max. AC set by rutting test (must be less than 98% density) Min. AC set by cracking test Optimum is between max. AC and min. AC November 2015 NCHRP 9-57

12 November 2015 NCHRP 9-57 Balanced Mix Design

13 Asphalt Pavement Analyzer Rutting Tests Hamburg Wheel Track Test November 2015 NCHRP 9-57

14 HWTT Rut 1000 Passes (mm) HWTT Rut Passes (mm) OT Cycles OT Cycles Approaches for Improving Cracking Resistance of RAS Mixes Decrease design air void 5.2% AC with 3.0% air voids 5.7%AC with 2.3% air voids Impact of Decreasing Design Air Voids on Cracking Impact of Decreasing Design Air Voids on Cracking TOAS-E Impact of Decreasing Design Air Voids on Rutting/Moisture Damage TOAS-E TOAS-E 5.2% AC with 3.0% air voids 5.7% AC with 2.3% air voids TOAS-E 5.2% AC with 3.0% air voids 5.7% AC with 2.3% air voids MWAS-C MWAS-C Impact of Decreasing Design Air Voids on Rutting/Moisture Damage MWAS-C MWAS-C

15 Types of Cracking Thermal Reflection Top-Down Fatigue Bottom-Up Fatigue November 2015 NCHRP 9-57

16 Temp Thermal Cracking Two types Cold Temperature Contraction Temperature Cycling Fatigue Elko, NV October 2015 Summer Fall Winter November 2015 NCHRP 9-57

17 Reflection Cracking Due to movement of underlying material Shrinkage from Temperature Change or Hydration Lack of Load Transfer November 2015 NCHRP 9-57

18 Bottom-Up Fatigue Cracking Repeated loads cause bending with cracks starting at the bottom and propagating up. Usually occurs in thin pavements. November 2015 NCHRP 9-57

19 Top-Down Fatigue Cracking Aged pavements are stiffer at the top, and that starts the crack that propagates down very slowly. Usually occurs in thick pavements Aging Stiffness November 2015 NCHRP 9-57

20 9-57 Project Objectives Identify cracking tests for thermal, reflection, T-D fatigue, B-U fatigue Literature review State survey Workshop Develop experimental design for field validation Experimental design Plans for sampling, storing, shipping and testing materials Estimated schedule and budget Develop plans for laboratory evaluation Precision and Bias Ruggedness November 2015 NCHRP 9-57

21 Goals Cracking Tests Workshop Select cracking tests for 4 cracking types Identify potential field/apt test sections What we prepared for the workshop: Interim report Cracking test webinars Cracking test booklet 9 cracking test videos November 2015 NCHRP 9-57

22 Interim Report Cracking Tests Low-temp. Reflection Bottom-up Top-down DCT (D ) Texas OT (Tex 248-F) Beam fatigue ( T321) IDT (UF) SCB (TP105) DCT (D ) S-VECD (TP107) S-VECD (TP107) IDT (T322) SCB (LTRC) RDT (TAMU) RDT (TAMU) TSRST/UTSST (UNR) SCB (LTRC) Texas OT (Tex 248- F) SCB (LTRC) November 2015 NCHRP 9-57

23 Strain level Monotonic Very high strain Cracking types vs. tests Low Overlay High strain High Fatigue Lower strain 1 No. of cycles November 2015 NCHRP 9-57

24 9 Cracking Test Videos IDT for low temperature cracking SCB at low temperature TSRST/UTSST DCT OT RDT S-VECD Bending beam fatigue SCB at intermediate temperature Available at NCHRP 9-57 web page on TRB web site. November 2015 NCHRP 9-57

25 Cracking Test Videos DCT: SCB at low temperature: UTSST: IDT: OT: SCB at int temp: BBF: S-VECD: RDT: November 2015 NCHRP 9-57

26 A quick reference Discussion guide Test simplicity Training, spec. prep., instru. testing, analysis, interpretation Test variability Test sensitivity Correlation to field performance Test equipment cost/availability State adoption Cracking Tests Booklet Available at NCHRP 9-57 web page on TRB web site. November 2015 NCHRP 9-57

27 November 2015 NCHRP 9-57

28 Workshop Outcomes Items Thermal Cracking Reflection Cracking Bottom-up Fatigue Cracking Top-down Fatigue Cracking Selected cracking tests 1. DCT 2. SCB-IL 3. SCB at low temp. 1. OT 2. SCB at intermediate temp. 1. BBF 2. SCB at intermediate temp. 1. SCB at intermediate temp. 2. IDT-UF 3. BBF Key factors for designing field experimental test sections Potential field test sections 1. Climate (temperature, moisture, solar radiation); 2. Traffic; 3. Pavement structure and subgrade; 4. Asphalt mixtures; 5. Existing pavement conditions for reflection cracking. 1. LTPP; 2. SPS10; 3. MnRoad; 4. NCAT Test Track; 5. Test sections under NCHRP 9-55, 9-58, and November 2015 NCHRP 9-57

29 Disc Compact Tension (DCT) Semi-Circular Bending (SCB) Selected Cracking Tests University of Minnesota Low Temperature Louisiana Transp. Research Center Intermed. Temp University of Illinois Intermed. Temp Overlay Tester (OT) Indirect Tension Test (IDT) Bending Beam Fatigue (BBF) November 2015 NCHRP 9-57

30 Stress Creep Compliance Load Strain DCT SCB Fracture Energy What s Measured? BBF OT Number of Cycles Crack Opening Time Tensile Strength + IDT Creep Compliance Strain November 2015 NCHRP 9-57 Time

31 Disk Compact Tension (DCT) Low Temp. Cracking ASTM D7313 Fracture Energy Relatively Simple Training Sample Prep 4 cuts, 2 holes Instrumentation Quick Analysis Low Variability Correlated to Thermal Cracking at Mn/ROAD Cost ~ $49,000 State Adoption: MN and WI. Under review in CO, SD, MT November 2015 NCHRP 9-57

32 DCT Video November 2015 NCHRP 9-57

33 Semi-Circular Bend (SCB) Thermal, Reflection, Bottom-Up, Top-Down AASHTO TP105 Fracture Energy Relatively Simple Training Sample Prep 4 cuts Instrumentation ~30 min Analysis Medium Variability Correlated to Thermal Cracking at Mn/ROAD Cost ~ $52,000 State Adoption: Low Temp: Under Review by UT, SD, PA, MT Intermed Temp: LA, WI. Under Review by OK, NM. IL adopting mod version. November 2015 NCHRP 9-57

34 SCB Low Temp Video November 2015 NCHRP 9-57

35 SCB Intermediate Temp Video November 2015 NCHRP 9-57

36 Overlay Tester (OT) Reflection, Bottom-Up Fatigue Tex-248-F No. Cycles to Failure Relatively Simple Training Sample Prep 4 cuts, plate mount No Instrumentation min. Analysis High Variability Correlated to Refl. Cracking in TX, NJ, CA. Fatigue Cracking at ALF, NCAT Cost ~ $46,000 State Adoption: TX and NJ. Under review in NV, FL, OH, MT November 2015 NCHRP 9-57

37 OT Video November 2015 NCHRP 9-57

38 Bending Beam Fatigue (BBF) Bottom-Up Fatigue AASHTO T321 No. Cycles to Failure or 50% Modulus Reduction Relatively Simple Med. Training Sample Prep 4 cuts Instrumentation Hours to days Analysis Very High Variability Correlated to Bottom-Up Cracking Cost could be > $100,000 State Adoption: CA for Long-life asphalt. Under review in NV and GA November 2015 NCHRP 9-57

39 BBF Video November 2015 NCHRP 9-57

40 Indirect Tension (IDT) Thermal Cracking AASHTO T322 Creep Compliance/Tensile Strength Relatively Simple Med Training Sample Prep 2 cuts Instrumentation can be complex 4-6 hrs Analysis Low Variability Correlated to Thermal Cracking in SHRP and MEPDG Cost can be > $100,000 (hydraulic test machine) November 2015 NCHRP 9-57

41 IDT Video November 2015 NCHRP 9-57

42 Laboratory Evaluation Review Existing Information and Studies SCB ILS Asphalt Institute NCAT Available Test Equipment Ruggedness Testing Precision and Bias November 2015 NCHRP 9-57

43 Ruggedness Testing Purpose: Identify factors that influence test results and determine how closely they must be controlled. Sensitivity test on variables instead of materials. Example: SCB Specimen thickness Loading rate Test temperature Notch depth Air voids November 2015 NCHRP 9-57

44 Interlaboratory Study Purpose: Determine repeatability and reproducibility of test method. Repeatability single operator Reproducibility multiple laboratories Test familiarization is important Test specimens from one laboratory Virgin DGA with 19 mm NMAS Virgin DGA with 9.5 mm NMAS DGA with high binder replacement November 2015 NCHRP 9-57

45 Objective: Validate Cracking Tests Not Study Cracking Mechanisms Field Validation Experimental Design Want to make sure cracking test differentiates mixes that will crack from those that will not. November 2015 NCHRP 9-57

46 Consider Factors Pavement Structure Climate Traffic Mix Types Binders Existing Facilities vs. New Sections Field Validation Experimental Design November 2015 NCHRP 9-57

47 Available Facilities and Characteristics Items APT Full-scale test tracks Full-scale Test Roads In-service Pavements Examples Traffic load FHWA-ALF, Louisiana-LAF, CalTrans-HVS, Florida-HVS, Illinois-ATLAS, TxDOT-APT Known traffic; well controlled traffic; often overloaded Traffic speed Slow; around 5-12 mph WesTrack NCAT test track Known traffic; WesTrack: 4 units of tractor/ trailer triple combinations NCAT Track: four fully loaded trucks Around mph MnRoad Known traffic; Real traffic Real traffic and real speed (around 60 mph) LTPP-GPS/SPS sections and state DOT sections NCHRP Sections Unknown traffic (most of time); Real traffic; many SPS sections equipped with WIMs Real traffic and real speed (around 60 mph) Test period Several months one-three years 4 years Several years to more than 15 years Environment Temperature is often Natural weather Natural weather Natural weather controlled Aging effect Artificial aging can be considered, but Impact of short-term aging on performance is considered. Impact of short/medium-term Impact of long-term aging is addressed November 2015 not natural aging NCHRP 9-57 aging is considered

48 Balanced RAP/RAS Mix Design for Project- Specific Service Conditions Texas Example

49 Benefit of RAP/RAS Economics Saving aggregates Saving asphalt binder Reducing rutting Introduction Environment Reducing demands of non-renewable resources Reducing landfill space demands RAP/RAS must be used!

50 No.1 concern- variability Binder grade variation Binder content variation Aggregate gradation Solution: Best practices for RAP/RAS processing and stockpile management Multiple sources RAP Well Separated RAP

51 Limitations of current design methods for RAP/RAS mixes Feature of RAP/RAS mixes: Unknown VMA (V BE ) Don t know how RAP/RAS blends with virgin binder. Virgin RAP/RAS Need a mechanical test to assure cracking resistance.

52 Balanced RAP/RAS mix design for project specific condition Current mix designs not suitable for RAP/RAS design Need to assure rutting resistance Need to assure cracking resistance Need volumetric-air voids for QC Need project-specific rutting and cracking requirements Traffic Climate Structure

53 RAP/RAS field test sections and performance Amarillo-Overlay: (Aug 2009) IH40: Heavy traffic; Cold weather; Soft binder RAP: 0, 20, 35% Pharr district-new Const.: (April 2010) FM1017: low traffic; Hot weather; stiff binder RAP: 0, 20, 35% Laredo-Overlay: SH359, 20%RAP (Mar. 2010) Houston-New Const.:SH146, 15%RAP/5%RAS (Oct. 2010) Fort Worth-AC/CRCP: Loop 820 (July 2012)

54 RAP/RAS field test sections and performance Test sections Highway Overlay/ new const. Weather Traffic MESAL OT cycles Performance Amarillo Pharr Laredo Houston 0%RAP IH40 (severely 20%RAP 4 inch/ 103 cracked thick Cold 30 overlay asphalt pavement) 35%RAP yrs: 100% refl. cracking 3 yrs: 57% refl. cracking 0%RAP 28 3yrs: overall - 20%RAP FM1017-Very 1.5 inch/ good conditions Very hot good support new const. 35%RAP 7 20%RAP 15%RAP/5 %RAS Dalhart 5%RAS US87 SH359-regular support SH146-Very good support 3 inch/ overlay 2 inch/new const. 3 inch/ Overlay Very hot hot Cold /96 3yrs: No cracking 2.5yrs: No cracking 96 cycles-20% RCR; 48 cycles- 50%RCR

55 RAP/RAS field test sections and performance 1. RAP/RAS mixes perform well at certain locations. 2. One OT requirement cannot fit for all. 3. Successful use of RAP/RAS mixes depends on Weather/Traffic AC overlay Overlay thickness, Existing pavement structure (AC/AC; AC/PCC) Existing pavement conditions New construction Pavement structure and which layer (surface, base, etc.) 4. Design the mix for project-specific conditions

56 Balanced RAP/RAS mix design for project specific condition Cracking Rutting Mix Design

57 Balanced RAP/RAS Mix Design Hamburg test for rutting/moisture damage Overlay test for cracking OT requirement determined by Overlay program Max. density-98% for controlling potential bleeding

58 Mixture engineering properties at selected asphalt contents RAS (/RAP) Virgin binder WMA additive Raw aggregates Existing pavement conditions (crack severity level, LTE) if asphalt overlays Mixing temperature and time Traffic Pavement structure Climate Conditioning temperature and time S-TxACOL SGC(N design ) Compactability/ workability Volumetric properties Predicted cracking development Select at least 2 asphalt contents Cracking: Overlay test Rutting/moisture damage: Hamburg wheel tracking test Meet requirements No Yes Balanced mix for project-specific conditions

59 Overlay Life (months) Balanced RAP/RAS Mix Design for Project-Specific Conditions Simplified Overlay design system Required main inputs: 1. OT cycles 2. Existing pavement conditions Determination of Min. OT cycles " Overlay over 10" JPCP under 3 MESALs/20 Years OT Cycles

60 Demonstration of project-specific OT requirement AC overlay scenarios AC/PCC AC/AC/CTB AC/AC/granular base Traffic level: 3 MESAL SH/US: 3-5 MESAL Weather: Amarillo Austin McAllen

61 Demonstration of project-specific OT requirement Amarillo

62 Demonstration of project-specific OT requirement Austin

63 Demonstration of project-specific OT requirement McAllen

64 Approaches for Improving RAP/RAS Mix Cracking Performance Available approaches Increase virgin AC (higher density) Soft, modified binders: PG64-28, PG64-34, PG58-34 Decrease air voids Rejuvenators

65 Summary and Conclusions RAP/RAS mixes can have same or better performance with proper design. Balanced RAP/RAS mix design for project-specific conditions is recommended for use. Hamburg test for rutting/moisture damage OT for cracking; Project-specific OT requirement Max. density to control potential bleeding Different approaches are available for improving RAP/RAS mix performance if needed.

66 Overlay Life (months) 72 2" Overlay over 10" JPCP under 3 MESALs/20 Years OT Cycles

67 What do We do with This? BalancedMix Design Set Volumetrics QC Volumetrics Opt. AC Set Tolerances Description Table 11 Operational Tolerances Test Method Allowable Difference Between Trial Batch and JMF1 Target Allowable Difference from Current JMF Target ±6.0 1 Individual % retained for #8 sieve and larger Tex-200-F Must be within Individual % retained for sieves smaller than #8 and or master grading limits ±4.0 larger than #200 Tex-236-F in Table 8 % passing the #200 sieve ±2.0 1 Asphalt binder content, % Tex-236-F ±0.5 ±0.5 Laboratory-molded density, % Tex-207-F ±1.0 ±1.5 VMA, %, min Tex-204-F Note 2 Note 2 1. When within these tolerances, mixture production gradations may fall outside the master grading limits; however, the % passing the #200 will be considered out of tolerance when outside the master grading limits. 2. Mixture is required to meet Table 8 requirements. November 2015 NCHRP 9-57 QA Volumetrics Some Day QA Performance Testing

68 NCHRP 9-57 November 2015

69 At the 2016 AAPT Meeting: Leading Edge Workshop: Cracking Tests 5 Presentations on Cracking Tests Symposium: Balanced Mix Design 5 Presentations on High RAP/RAS Implementation of Specifications Aging Behavior Forum Topic: World Asphalt Market NCHRP 9-57 November 2015

70 Thanks for your Participation Please complete the evaluation to provide your feedback on this session and suggest topics for future events. Remember to mark these upcoming events on your calendar! March 7-11, March 22-24, 2016 Nashville, TN