Advanced Asphalt Technologies, LLC Engineering Services for the Asphalt Industry

Transcription

1 NCHRP 9-59 Update September 12, 2016 FHWA Binder ETG Fall River, MA Advanced Asphalt Technologies, LLC Engineering Services for the Asphalt Industry

2 Outline Objectives Problem Generalized failure theory Typical failure envelope Fracture/fatigue performance ratio Results to date Future work

3 NCHRP 9-59 Objective The primary objective of NCHRP 9-59 is to develop a test or tests that will help to effectively and efficiently control the properties of asphalt binders that contribute to the fatigue resistance of asphalt mixtures

4 Presentation Objective Describe general approach to developing an improved binder fatigue test Provide summary of results to date Describe future efforts

5 Problem Bill Ahearn, Pamela Marks, Simon Hesp

6 Problem Can G* sin δ be improved? Added to? Replaced? Effect of modulus on fatigue performance Relationship between fracture and fatigue performance Binder vs mix

7 Generalized Failure Theory N N D f f FSC = ε = = n i= binder FSC [ ε ( VBE )] mix 1.38 ( ε ) ( 90 δ ) mix N i i ( VBE ) FSC = D δ ( ) ( 90 δ ) FSC = fatigue strain capacity ( 90 δ ) Phase angle δ is for the binder, not the mix

8 Typical Failure Envelope 1.E+03 Failure Strain or FSC, % 1.E+02 1.E+01 1.E+00 1.E-01 1.E-02 1.E+04 1.E+05 1.E+06 1.E+07 1.E+08 1.E+09 1.E+10 Secant Modulus/3 or G*, Pa ARC Fatigue AAT Misc. DT/NM AAT ARC/9-25 DENT/NM DT PMod Failure Envelope 9-25 Fatigue ALF2 DT/NM ALF DENT/NM DENT PMod Heukelom

9 Fatigue/Fracture Performance Ratio, FFPR FFPR = Measured FSC or ε * Typical FSC or ε * Typical FSC or ε* = ( ) T, t S( T t) S, FFPR is simply the ratio of observed to expected failure strain. Values significantly above 1 are good, below 1 are bad. The equation above is preliminary.

10 Binder Test Methods DSR frequency sweep (R value) Modified double edge notched tension (DENT) Linear amplitude sweep (LAS) Single edge notched bending (SENB) Various others from existing data

11 Master Curve PG 76-22

12 Modified DENT Test Standard ductility batch Molds/specimens same as for forceductility but with double 2.5-mm notch 50 mm/min Temperature 10 to 20 C Force, N Sample 1 Sample 2 Sample Extension, mm

13 Modified DENT as a Tension Test: ALF Air Blown at 20 C

14 LAS Test for PG C Fit 300 s 600 s 900 s S

15 Preliminary Results: Testing of ALF Binders

16 ALF Fatigue Experiments Most of the binders for the first and second ALF fatigue experiments were tested These included PG 70-22, air blown binder, Terpolymer, SBS-LG, crumb rubber binder, AC 5 and AC 20 RTFOT aging

17 ALF Binders: Correlation among FFPR Values 2.0 LAS FFPR R² = 82% Direct Tension FFPR DENT FFPR 0.0 LAS FFPR R² = 79% 0.5 R² = 65% DENT FFPR Direct Tension FFPR

18 ALF Binders: Correlation Between Cycles to 25 m Cracking 250, , , ,000 50,000 0 R² = 90% Cracking and DENT FFPR FFPR: ALF 1 & 2, 100 mm Test Sections Cycles to 25 m Cracking 250, , , ,000 50,000 0 R² = 94% LAS FFPR

19 ALF Binders: Correlation Between Cracking and FFPR: ALF 1 & 2, 100 mm Test Sections Cycles to 25 m Cracking Cycles to 25 m Cracking 250, , , ,000 R² = 90% 50, Direct Tension FFPR 250, , ,000 R² = 57% 100,000 50, Binder R-Value

20 NCHRP 9-59 Test Plans

21 NCHRP 9-59 Tests Many binder tests correlated to ALF fatigue performance Will this approach work for 9-59 materials and test methods? Will binder and mixture test data correlate? Will test data match expected performance

22 NCHRP 9-59 Binders No. Additive PG Grade Comments 1 SBS Grade is approximate; base, 6 %+ SBS 2 SBS SBS/PPA SBS Base binder = 58-28; SBS % = % 5 SBR Base binder = 64-22; SBR % = % (terminal blend) 6 EVA source source 2; significantly different chemistry/rheology 10 GTR terminal blend 11 oxidized oxidized REOB source 1 14 REOB source 2; significantly different chemistry/rheology 15 Terpolymer PPA 70-22

23 NCHRP 9-59 Mixture Testing Uniaxial fatigue (SVECD) Two temperatures Three replicates (Texas overlay test) 20 C Three replicates Bending beam fatigue

24 NCHRP 9-59 Mixture Design 9.5 mm nominal maximum size Blend of granite, limestone and sand 6.0 % binder content Designed at 4.0 % air voids at 80 gyrations Compacted to 7.0 % air voids for most tests

25 NCHRP 9-59: Laboratory Aging Binders: RTFOT + 40 hour PAV Mixture: Standard short term aging followed by loose mix aging at 95 C for 5 days. Based on data available at the start of the project, which was very limited

26 Comparison of Mix and Binder Laboratory Aging

27 Preliminary NCHRP 9-59 Results

28 Modified DENT Test Results Binder Temp Stiff/3, Pa Fail. Strain, % Expected FS, % FFPR PG SBS E E PG E E PG REOB E E LAS Test Results Binder Temp G*, Pa Avg. FSC, % Exp. FSC, % FFPR PG SBS E PG E PG REOB E

29 Uniaxial Fatigue Results Binder Temp G* Avg. FSC, % Exp. FSC, % Avg. FFPR PG SBS E E PG E E PG REOB E E Texas Overlay Test Results Binder Temp G* Cycles Avg. FSC, % Exp. FSC, % Avg. FFPR PG SBS E PG E PG REOB E

30 NCHRP 9-59 Data Compared to Typical Failure Envelope FSC or Failure Strain, % 1.E+03 1.E+02 1.E+01 1.E+00 1.E+05 1.E+06 1.E+07 1.E+08 G* or Stiffness/3, Pa Fit DENT PG FATIGUE PG TOT PG DENT PG FATIGUE PG TOT PG DENT PG REOB FATIGUE PG REOB TOT PG REOB LAS PG LAS PG LAS PG REOB

31 Mix Uniaxial Fatigue vs Binder MDENT 2.0 FFPR, Mix Uniaxial Fatigue Data Equality R² = 85% FFPR, Binder MDENT

32 Using Average Mix FFPR and Energy-Based DENT FFPR 2.0 Avg. FFPR, Mix Uniaxial Fatigue Data Equality PG PG PG REOB R² = 93% FFPR (Energy based), Binder MDENT

33 Energy-Based DENT FFPR Total Energy to Failure, N-m Specimen Stiffness at 3 Seconds, KN/m Typical ALF Blown ALF SBS LG ALF Terpolymer PG REOB PG Fit/Typical

34 Mix Uniaxial Fatigue vs LAS 2.0 FFPR, Mix Uniaxial Fatigue Equality R² = 61% FFPR, LAS

35 Mixture Uniaxial Fatigue vs R 2.0 FFPR, Mix Uniaxial Fatigue R² = 38% Binder R Value

36 Texas Overlay vs MDENT FFPR, Mix Texas Overlay Test Equality Mix Tx OT Linear (Mix Tx OT) R² = 92% FFPR, Binder MDENT

37 Texas Overlay vs LAS 2.0 FFPR, Mix Tx Overlay Test Equality R² = 46% FFPR, LAS

38 Interim Findings The proposed general failure theory and failure envelope appear to provide a powerful tool for evaluating the fatigue and fracture resistance of asphalt binders and mixes

39 Interim Findings The RTFOT + 40 hour PAV binder aging appears to produce a similar degree of aging as the 5 day loose mix aging at 95 C, but much more research is needed to verify and fine tune these aging protocols

40 Interim Findings The modified DENT test correlates very well to both field fatigue performance in the FHWA ALF studies and in laboratory tests conducted in the first stage of NCHRP 9-59 testing. The LAS test is also promising we may need to make adjustments

41 Future work Additional binder testing: 13 more binders and including SENB test Healing study Parametric study on relationship between modulus and fatigue performance Validation testing

42 Acknowledgements Those I have borrowed data from Support of NCHRP The NCHRP Panel Industry suppliers Nam Tran and his associates at NCAT My associates at AAT, including Ray, Don, and Bob