Caltrans Implementation of PG Specs. Caltrans. Presentation Overview. HMA in California. Why, When & How? How will if affect YOU?

Transcription

1 Caltrans Implementation of PG Specs PG - Performance Graded Presentation Overview Why, When & How? How will if affect YOU? Caltrans Local Agencies Industry Consultants HMA in California ~ 1 Ton HMA/Person/Yr ~ 34 Million Tons/Yr 1

2 Binder Specifications Then & Now Specification Systems Penetration Viscosity PBA Superpave PG Penetration Grading System Introduced in 1918 by Bureau of Public Roads (now the FHWA) At least 9 penetration grades 1956 PCCAS formed Goal was to reduce the number of grades & standardize specs 1957 PCCAS adopted 5 grades PCCAS = West Coast User-Producer Group 2

3 Penetration Grading System 0 sec 5 sec Pen (dmm( dmm) 100g 100g Based on magnitude of the penetration of a standard needle at 25 C Penetration Spec Classification based on pen at 25 C Also considers Penetration at 4 C4 Flash point Viscosity at 135 C Solubility Thin Film Oven Aging Penetration at 25 C Ductility Temp Susceptibility Penetration, 0.1 mm 25 C C (77 F) Temp 3

4 Viscosity Grading System Original Binder (AC) Aged Residue (AR) Viscosity Grading System AC Developed in 1960s Replace penetration system Based on unaged binder consistency at max in-service temp AASHTO M226 & ASTM D3381 AR Caltrans in the 1960s Based on aged binder to simulate post-mixing binder consistency AC Spec Tests Classification based on vis at 60 o C Also considers Vis at 135 o C Pen at 25 o C Flash Point Solubility TFO-aged residue Vis at 60 o C Ductility at 25 o C 4

5 Viscosity Grades (AC-xx) AC PCCAS and the AR RTFOT adopted as alternative to TFOT Use of RTFOT-conditioned asphalt began Formally adopted Implementation Caltrans Grades & Tests Classification based on aged-residue vis at 60 o C AR Grades* AR * Caltrans Std Specs, Section 92 Greenbook Section

6 Caltrans Grades & Tests Also considers tests on RTFO-aged residue Vis at 60 o C & 135 o C Pen at 25 o C % of Original Pen Ductility Properties of unaged asphalt Flash Point Solubility Comparison of Pen & Vis Grades Pen AC AR Log of Relative Stiffness AC 40 AC 20 AC 10 AC 5 AR AR 8000 AR 4000 AR 2000 AR 1000 AC 2.5 6

7 Relationship Between Vis & Pen Pen at 25ºC C (0.1 mm) Vis at 60ºC C (Poise) AC-2.5 AC-5 AC-10 AC-20 AC-40 Coastal Valley NB: Asphalt Institute Data Limitations of Pen & Vis Grading Systems Penetration: Empirical measurement Viscosity: Viscous effect only No low temp properties (except PCCAS-pen ratio) Long-term aging not considered Inadequate for modified binders PCCAS to the Rescue 1987 Paving Asphalt Committee charged to develop specs for modified asphalts Representatives from Industry Chevron & Golden Bear ODOT Caltrans 7

8 PBA Concept Performance Rutting, Fatigue & Low Temp Cracking Safety Environment Purity Compatibility Climate PBA Grade Binder Tests Test Criteria PBA Spec Precursor to SHRP PG Climatic guidelines to select grade Conventional tests to relate to performance Unique grades PBA (performance-based asphalt) Identifies modified binders by grade Current PBA Spec - Handout 8

9 PG Asphalt Binder System PG - Performance Graded PG System Developed in 1990s during SHRP in concert w/ PCCAS Fundamental Properties, ie,, stress and strain Unmodified binders Performance Considerations Rutting, Cracking (Fatigue & Low Temp), & Aging Environment FHWA Resources Asphalt Institute NAPA (National Asphalt Paving Assn) NCAT (National Center for Asphalt Tech) 9

10 PG Spec (eg( eg,, PG 64-16) Viscosity/Stiffness In-Service Construction Original -6 C 28 C 64 C 135 C PG Spec System Based on Climate - In-Service Pavement Temps PG XX - YY Min Pavement Performance Surface Temp (ºC)( Grade Average 7-day 7 Max Pavement Temp (ºC)( Determination of Pavement Temp Used in PG Spec Determine-Project Specific Air Temps Compute Design-Specific Pavement Temps from Air Temps 10

11 Air Temps Superpave Weather Database NOAA ~ 40 years of data 7,900+ stations in US & Canada 308 stations in California Uses Annual Air Temps Hottest, consecutive 7-day 7 temp (average & standard deviation) Coldest temp (average & standard deviation) Calculated Pavement Temps used in PG Selection Reliability Percent Probability of Not Exceeding Design Temp Generated from Site Specific Mean and Standard Deviation Frequency of observed temperatures (Total area under curve = 100 %) PG High Temp Reliability is area under curve to the Left of T des T des = T avg ± 2σ T avg T des Observed Air Temps 50% reliability = X average summer very hot summer 98 % reliability = X + 2σ Day Max Air Temps ºC 11

12 Observed Air Temps San Diego (La Mesa) very cold winter -3 average winter 1 average summer 35 very hot summer ºC Pavement Temps -3 1 Max Air Temp Calculated Pavement Temp ºC ºC PG Binders PG (98% reliability) PG (50% reliability) ºC

13 PG Concept & Equipment Low temp Service temps Intermediate temp Mixing High temp DTT (optional) DSR RV BBR Temp ( C)( PG Spec Testing Low Temp Cracking Fatigue Cracking Rutting Pumpability DTT (optional) BBR DSR RV Age Conditioning No aging RTFO (Short Term) PAV (Long Term) 13

14 PG Spec Testing Pumpability RV Age Conditioning No aging RTFO (Short Term) PAV (Long Term) PG Spec Testing Rutting DSR Age Conditioning No aging RTFO (Short Term) PAV (Long Term) PG Spec Testing Fatigue Cracking DSR Age Conditioning No aging RTFO (Short Term) PAV (Long Term) 14

15 PG Spec Testing Low Temp Cracking DTT (optional) BBR Age Conditioning No aging RTFO (Short Term) PAV (Long Term) Low temp properties Service Temps Intermediate temp properties Mixing High temp properties DTT (optional) DSR RV BBR Temp ( C)( PG Specification AASHTO M

16 Current PG Spec - Handout Tests Used in PG Binder System Safety - Flash Point Pumpability - RV at High Temp (135ºC) Rutting - DSR at High Temps Original & RTFOT-Aged; ie,, 2 conditions Fatigue Cracking - DSR at Intermediate Temps RTFOT PAV-Aged; Aged; ie,, 1 condition Low Temp Cracking - BBR & DTT (optional) at Low Temps RTFOT PAV-Aged; Aged; 1 condition PG Spec Testing Low Temp Cracking Fatigue Cracking Rutting Pumpability DTT (optional) RV BBR DSR Test Temp ( C)( 16

17 CEC Avg 7-day Max, o C 1-day Min, o C Safety & Pumpability > 230 o C < 3Pa. 135 o C PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV > 1.00 kpa > 2.20 kpa 20 Hours, 2.07 MPa (Dynamic Shear Rheometer) DSR G*/sin δ (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % (Dynamic Shear Rheometer) DSR G*/sin δ First Checks (PRESSURE AGING VESSEL) PAV >230 C 3.0 Pa s (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin δ < 5000 kpa S < 300 MPa m > Report Value > 1.00 % ( Bending Beam Rheometer) BBR S Stiffness & m - value (Bending Beam Rheometer) BBR Physical Hardening (Direct Tension) DT Pumpability During construction a contractor must be able to pump the binder. Viscosity (η) 3 Pa s at 135 C C for the unaged binder PG Spec Testing Low Temp Cracking Fatigue Cracking Rutting Pumpability DTT (optional) RV BBR DSR Test Temp ( C)( 17

18 Rutting/Permanent Deformation CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < 3Pa. 135 o C > 1.00 kpa PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV (Dynamic Shear Rheometer) DSR G*/sin δ Unaged > 2.20 kpa RTFO Aged 20 Hours, 2.07 MPa (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % (Dynamic Shear Rheometer) DSR G*/sin δ (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin δ < 5000 kpa S < 300 MPa m > Report Value > 1.00 % ( Bending Beam Rheometer) BBR S Stiffness & m - value (Bending Beam Rheometer) BBR Physical Hardening (Direct Tension) DT How the PG Spec Works Spec Requirement Remains Constant CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < 3Pa. 135 o C PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV > 1.00 kpa (Dynamic Shear Rheometer) DSR G*/sin δ (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % > 2.20 kpa 20 Hours, 2.07 MPa < 5000 kpa (Dynamic Shear Rheometer) (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) Test Temp Changes (Dynamic Shear Rheometer) DSR G*/sin δ DSR G* sin δ S < 300 MPa m > Report Value > 1.00 % ( Bending Beam Rheometer) BBR S Stiffness & m - value (Bending Beam Rheometer) BBR Physical Hardening (Direct Tension) DT Rutting/Permanent Deformation Addressed by G*/sin δ > 1.00 kpa (unaged binder) G*/sin δ 2.20 kpa (RTFO-aged binder) For the early part of the service life 18

19 Mass Loss Spec Calculate mass loss after RTFO. Mass loss, % = Original mass - Aged mass Original mass x 100 Mass Loss 1.0% Establishing Grades - DSR Data Relative Values of G*/sin δ (kpa kpa) NB: 1. Stiffness approximately doubles with each 6ºC decrease in temp. 2. G*/sin δ 1.0 kpa at 60ºC for AC-10 AC Temp (ºC) PG Spec Testing Low Temp Cracking Fatigue Cracking Rutting Pumpability DTT (optional) RV BBR DSR Test Temp ( C)( 19

20 CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < 3Pa. 135 o C Fatigue Cracking PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV > 1.00 kpa (Dynamic Shear Rheometer) DSR G*/sin δ (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % > 2.20 kpa 20 Hours, 2.07 MPa (Dynamic Shear Rheometer) DSR G*/sin δ (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin δ < 5000 kpa S < 300 MPa m > ( Bending Beam Rheometer) BBR S Stiffness & m - value Report Value (Bending Beam Rheometer) BBR Physical Hardening > 1.00 % (Direct Tension) DT PAV Aged Fatigue Cracking Addressed by stiffness at intermediate temp G*sin δ on RTFO & PAV-aged binder < 5000 kpa For later part of pavement service life Fatigue Testing Long-term performance problem Use aged binder Short-term term aging (RTFO) + Long-term aging (PAV) 20

21 Notes on the Spec Assumed strain controlled distress (thin HMA) Initially a maximum of 3 MPa Over 50% of binders tested failed Raised to max of 5 MPa; ; 15% of binders failed Basis for limiting to 5 MPa PG Spec Testing Low Temp Cracking Fatigue Cracking Rutting Pumpability DTT (optional) RV BBR DSR Test Temp ( C)( CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < 3Pa. 135 o C Low Temp Cracking PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV > 1.00 kpa (Dynamic Shear Rheometer) DSR G*/sin δ (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % > 2.20 kpa 20 Hours, 2.07 MPa (Dynamic Shear Rheometer) DSR G*/sin δ (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin δ < 5000 kpa S < 300 MPa m > PAV Aged Report Value > 1.00 % ( Bending Beam Rheometer) BBR S Stiffness & m - value (Bending Beam Rheometer) BBR Physical Hardening (Direct Tension) DT

22 Bending Beam Rheometer Evaluates low temp stiffness Creep stiffness, S(t) Slope of log creep stiffness curve, m-value Log Creep Stiffness, S(t) m Log Loading Time, t (sec) PG Spec Testing Low Temp Cracking DTT (optional) Fatigue Cracking Rutting RV Pumpability BBR DSR Test Temp ( C)( CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < 3Pa. 135 o C Low Temp Cracking PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG (Flash Point) FP (Rotational Viscosity) ORIGINAL RV > 1.00 kpa (Dynamic Shear Rheometer) DSR G*/sin δ (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % > 2.20 kpa 20 Hours, 2.07 MPa (Dynamic Shear Rheometer) DSR G*/sin δ (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin δ < 5000 kpa S < 300 MPa m > PAV Aged ( Bending Beam Rheometer) BBR S Stiffness & m - value Report Value (Bending Beam Rheometer) BBR Physical Hardening > 1.00 % (Direct Tension) DT

23 DTT (optional) σ f (no spec criterion) ε f 1.0% Summary Evolution of binder grading systems Penetration Viscosity PBA & PG PG PG Fundamental properties measured. Quantifies binder contributions to rutting, fatigue & low temp cracking. Considers the effect of aging. Summary PG System - Selection based on climatic conditions at project site. Low temp (min pavement surface temp) High temp (average 7-day 7 max pavement temp) Spec requirement remains constant; test temp changes. 23

24 Binder Topics Needs based on climate Used Special cases California Climate PG Needs CA - High Temp PG Needs Locations High Temp PG (C) 50% 98% 24

25 CA Low Temp PG Needs Locations Low Temp PG (C) 50% 98% CA - PG Needs PG Binders! PG Binder Distribution Locations /308 locations PG Binder 25

26 PG PG PG PG PG Binder Map Caltrans Strategy-2006 Special Circumstances PBA 6a & 6b for cold regions PBA at discretion of District with economic justification eg: : Dist 9 PBA-6b eg: : Dist 8 PBA-6a* Caltrans Strategy Regular Conventional PG Binder Special Circumstances PG Polymer Modified 26

27 Caltrans Binder Selection Caltrans vs AASHTO Solubility, min RTFO mass loss, max DSR Caltrans 98.5% 0.60% Min elastic recovery, max phase angle AASHTO 99.0% 1.0% Implementation 4 unmodified PGs Jan 06 Replace modified PBAs with PG Jan 07 Asphalt Rubber base PG by RACTG Jan 06 AMRL Certification Jan 07 Training (Caltrans( Caltrans,, Local Agencies & Industry) Classroom: 12 Locations, Beginning Oct 05 27

28 PG Binders are not a panacea!!! Aggregate Characteristics Mix Design Construction Quality Control Other Considerations PG for other applications? Mixing PG binders of same grade but from different sources? Critical tests for checking binders? Mix design approval; effect of asphalt different supplier? Effects of PG binders on construction process (eg( eg,, impact on compaction)? PG vs AR grades? PG for Other Applications? Commercial Parking Lots, Truck Terminals Ports Airfields Commercial & General Aviation Residential Hydraulic Local Streets & Highways 28

29 PG for Other Applications? Tack Coats PG or PG Surface Treatments, eg, ChipSeals Conventional or polymer modified emulsions AC Dikes PG Crack Sealing, Expansion Joints FHWA-RD RD Mixing Binders Same PG But Different Sources? Same precautions as taken for AR binders. Critical Binder Testing? Spec tests BBR DSR (Original & RTFO-Aged) Use AMRL-Certified Commercial Lab! 29

30 Mix Design- Different Binder Supplier? Same precautions as taken for AR binders do another mix design! PG Binder Influence on Construction? Potential for stiffer binders may require higher mixing and placement temps. Plant production and placement temps ~ ºF F higher than traditional AR- graded binders. Another test strip? Questions? Comments? 30