Uniaxial Thermal Stress and Strain Test (UTSST)

Transcription

1 Thermal Strain (-) Temperature (C) Thermal Stress (MPa) Modulus (MPa) 9, 6, 3, Temperature ( C) Uniaxial Thermal Stress and Strain Test (UTSST)

2 Acknowledgement and Disclaimer The contents of this research effort are part of the overall effort in the Asphalt Research Consortium (ARC). The contents do not necessarily reflect the official views and policies of the Federal Highway Administration (FHWA). Slide 2

3 Thermal Cracking in AC Pavements (Cont d) Northern Nevada Courtesy: Nevada DOT Reno, NV Reno, NV Jan. Jul. Average Max. Temp ( C) Minden, NV Average Min. Temp ( C) Slide 3

4 Thermal Cracking in AC Pavements (Cont d) Bishop, CA Bishop, CA Bishop, CA Bishop, CA Jan. Jul. Average Max. Temp ( C) Average Min. Temp ( C) Slide 4

5 Thermal Cracking in AC Pavements (Cont d) Tucson, AZ Jan. Jul. Average Max. Temp ( C) Tucson, AZ Average Min. Temp ( C) Slide 5

6 Thermal Cracking in AC Pavements (Cont d) Average Temperature Ranges: Reno vs. Tucson Reno, NV Tucson, AZ Data Sources: climatespy.com, and Western Regional Climate Center Slide 6

7 Pavement Temperature Rates Average and Hourly Warming and Cooling Temperature Rates in AC Temperature ( C) Slide 7

8 Pavement Temperature Rates (Cont d) Average and Hourly Warming and Cooling Temperature Rates in AC Slide 8

9 Pavement Temperature Rates (Cont d) Measurements in AC at a Depth of 12.5 mm below pavement surface Cooling Rates Warming Rates Slide 9

10 Impact of Temperature on Binder Aging 5 4 Air Temperature Air Temperature ( ) Phoenix, AZ Reno, NV Glasgow, MT 1, 2, 3, 4, 5, 6, 7, 8, 9, Time (hour) Reno Air Temperature Phoenix Air Temperature Glasgow Air Temperature Slide 1

11 Impact of Temperature on Binder Aging (Cont d) Air Temperature ( ) Phoenix, AZ Reno, NV Glasgow, MT Air Temperature 5 1, 1,5 2, 2,5 3, Time (hour) Reno Air Temperature Phoenix Air Temperature Glasgow Air Temperature Slide 11

12 Impact of Temperature on Binder Aging (Cont d) Carbonyl Area (abs. unit) Binder CA Field Prediction for Same Asphalt Binder Reno-.1m depth film surface Phoenix-.1m depth film surface Glasgow.1m depth film surface Phoenix, AZ Reno, NV Glasgow, MT 24, 48, 72, 96, 12, 144, 168, 192, Time (hour) Slide 12

13 Thermal Cracking in AC Pavements Thermal cracking can be addressed by: Selecting the appropriate asphalt binder grade coupled with the proper rheological properties and aging characteristics. Selecting the appropriate aggregate properties and gradation. Assuring the proper mixture volumetric and properties. Slide 13

14 Thermal Stress Restrained Specimen Test (TSRST) Originally developed as a part of SHRP. Mixture specimen is started at an initial temperature then subjected to a temperature drop until fracture while height of the specimen is kept constant. Has been successfully utilized in pavement research to evaluate low temperature cracking properties of asphalt mixtures. Initially published as AASHTO TP1 (currently dropped from the AASHTO standards). European standard EN (212) to characterize asphalt mixtures for thermal cracking resistance. Slide 14

15 Thermal Stress Restrained Specimen Test (TSRST) Limitations/Potential Concerns Compaction of prismatic specimens. Variation in thermal stress build-up between replicate samples. Variation in fracture stress and fracture temperature. Implemented Enhancements UTSST Sample geometry and preparation methods (cylindrical specimens/reduce edge effect). Gluing technique (epoxy selection based on CTC and gluing jigs) End platens and fixtures (reduce eccentricity) Thermal strain measurements Draft ASTM Standard (pending D4.26) Slide 15

16 Test Procedure Specimen Preparation Four 57mm (2 ¼ in.) diam. 134mm (5 ¼ in.) height specimens Cored 9 from the axis of compaction of a SGC sample or a field core sample. Online Video: Slide 16

17 Test Procedure (Cont d) Loading Specimens into Testing Chamber Slide 17

18 Test Procedure (Cont d) Running the Test Start test at room temperature (typically 2 C) Apply thermal loading at 1 C/hour or another predetermined cooling rate through -4 C. Slide 18

19 Test Procedure (Cont d) Data Collection and Analysis Thermal Stress (MPa) Temperature ( C) Thermal Strain (-) Temperature (C) Automatic Data Analysis (MATLAB or MS Excel) Slide 19

20 Test Description Uniaxial Thermal Stress and Strain Test (UTSST) Platens Hydraulic Ram LVDTs Surface thermometer Restrained Specimen Dummy Specimen Environmental Chamber Restrained Specimen Dummy specimen Unrestrained Specimen Invar Rod Unrestrained Specimen Invar Rod Left LVDT \ Frictionless Roller Stand Thin Epoxy Right LVDT Slide 2

21 Test Description (Cont d) Uniaxial Thermal Stress and Strain Test Results Thermal Stress Build-up and Thermal Strain Slide 21

22 Test Description (Cont d) Data Analysis: Coeff. Of Thermal Contraction (CTC) 1 ; 1 Thermal Strain (mm/mm) CTC l T g CTC g Temperature ( C) Slide 22

23 Test Description (Cont d) Data Analysis: Calculation of Modulus Thermal Stress (MPa) Temperature ( C) Thermal Strain (-) Temperature ( C) Log (E) Temperature ( C) Boltzmann s Superposition Principle Slide 23

24 Test Description (Cont d) Data Analysis: Modulus as a Function of Temperature 1, 8, Crack Initiation (CI) Modulus (MPa) 6, 4, 2, Fracture Glassy Hardening Viscous-Glassy Transition Viscous Softening Temperature ( C) Crack Initiation Temp. (CIT) Slide 24

25 Test Description (Cont d) Data Analysis: UTSST Resistance Index f Thermal Stress (kpa) 4, 3,5 3, 2,5 2, 1,5 1, v 5 Av Viscous Softening Fracture Strength Ai Thermal Strain (mm/mm) Crack Initiation. Ap 1 Slide 25

26 Test Variability Prismatic versus Cylindrical Side Specimens COV 1% (Whiskers represent 95% confidence interval) Slide 26

27 Test Variability Fracture Location Failure Plane/Breakage Face Specimen alignment is critical such as with any tension test. The new gluing jig/technique reduced this issue significantly. Lab-Mix Lab-Compacted Field-Mix Field-Compacted/Cores Slide 27

28 Test Sensitivity Examples highlighting the test sensitivity to: Long-term aging; Air void level; Asphalt binder content; Aggregate mineralogy; Asphalt binder modification; Recycled materials. Slide 28

29 Modulus, E(UTSST) (MPa) Test Sensitivity (Cont d) Effect of Aging 8, 7, 6, 5, 4, 3, 2, 1, x x CA =.2 x x CA =.44 CAL19I22_7.44_7%_mo_6C CAL19I22_7.44_7%_3mo_6C CAL19I22_7.44_7%_6mo_6C CAL19I22_7.44_7%_9mo_6C CA =.59 CA = Temp( C) Property Fracture Temp ( C) Fracture Stress (MPa) Crack Initiation Temp, CIT ( C) Crack Initiation Stress, CIS (MPa) Glassy Hardening ( C) Viscous-Glassy Transition ( C) UTSST Resistance Index PG64-22 (7% Va) M 3 M 6 M 9 M Slide 29

30 Test Sensitivity (Cont d) Effect of Aging 8, 7, 6, x CA =.2 CAL19I22_7.44_7%_mo_6C CAL19I22_7.44_7%_3mo_6C CAL19I22_7.44_7%_6mo_6C CAL19I22_7.44_7%_9mo_6C 1, CAL19I22_7.44_7%_6 C Modulus, E(UTSST) (MPa) 5, 4, 3, x x x CA =.44 CA =.59 CA =.69 UTSST Resistance Index 1 1 2, 1, Temp( C) Oven Aging Period (Months) Slide 3

31 Test Sensitivity (Cont d) Effect of Air Void Level Modulus (MPa) 14, NV19I28_5.22_4%_mo_6C CAg =.3 NV19I28_5.22_4%_9mo_6C CAg =.74 NV19I28_5.22_7%_mo_6C 12, NV19I28_5.22_7%_9mo_6C 4% NV19I28_5.22_11%_mo_6C CAg =.3 NV19I28_5.22_11%_9mo_6C 1, 7% CAg =.8 8, CAg =.35 6, 11% CAg =.86 4, 2, Temperature ( C) Property Fracture Temp ( C) Fracture Stress (MPa) Crack Initiation Temp, CIT ( C) Crack Initiation Stress, CIS (MPa) UTSST Resistance Index 4% Va 7% Va 11% Va M 9 M M 9 M M 9 M , , , Slide 31

32 Test Sensitivity (Cont d) Effect of Air Void Level 14, CAg =.3 12, CAg =.3 1, 4% CAg =.74 NV19I28_5.22_4%_mo_6C NV19I28_5.22_4%_9mo_6C NV19I28_5.22_7%_mo_6C NV19I28_5.22_7%_9mo_6C NV19I28_5.22_11%_mo_6C NV19I28_5.22_11%_9mo_6C 1, 1, NV28_4%_6C NV28_7%_6C NV28_11%_6C Modulus (MPa) 8, CAg =.35 6, 4, 7% 11% CAg =.8 CAg =.86 UTSST Resistance Index 1, 1 2, Temperature ( C) Aging Period at 6 C (months) Slide 32

33 Test Sensitivity (Cont d) Effect of Asphalt Binder Content & Aggregate Mineralogy 1, 9, 8, 7, 5.4% 4.5% NV19I22_4.5_7%_mo_6C NV19I22_5.38_7%_mo_6C CO19I22_3.61_7%_mo_6C CO19I22_4.5_7%_mo_6C Property Fracture Temp ( C) Colorado Nevada 3.6% 4.5% 4.5% 5.4% Modulus (MPa) 6, 5, 4, 3, 4.5% 3.6% Fracture Stress (MPa) Crack Initiation Temp, CIT ( C) , 1, Temperature ( C) Crack Initiation Stress, CIS (MPa) UTSST Resistance Index , ,69 Slide 33

34 Test Sensitivity (Cont d) Effect of Asphalt Binder Content & Aggregate Mineralogy Modulus (MPa) 1, 9, 8, 7, 6, 5, 4, 3, 5.4% 4.5% 4.5% 3.6% NV19I22_4.5_7%_mo_6C NV19I22_5.38_7%_mo_6C CO19I22_3.61_7%_mo_6C CO19I22_4.5_7%_mo_6C 1, 1, UTSST Resistance Index , ,259 2, 1, NV_4.5 NV_5.4 CO_3.6 CO_4.5 Temperature ( C) Slide 34

35 Test Sensitivity (Cont d) Effect of Asphalt Binder Modification 8, 7, PG64-28 (SBS) NV19I28_5.22_7%_5day_85C NV19I28_5.22_7%_28day_85C NV19IBI3_5.22_7%_5day_85C NV19IBI3_5.22_7%_28day_85C Property PG64-28 (SBS) PG58-28 (Unmodified) 5 day 28 day 5 day 28 day Modulus, (MPa) 6, 5, 4, 3, 2, 1, PG58-28 (Unmodified) Fracture Temp ( C) Fracture Stress (MPa) Strain at Fracture (me) Crack Initiation Temp, CIT ( C) Crack Initiation Stress, CIS (MPa) UTSST Resistance Index , , , Temperature ( C) Slide 35

36 Test Sensitivity (Cont d) Effect of Asphalt Binder Modification Modulus, (MPa) 8, 7, 6, 5, 4, 3, PG64-28 (SBS) NV19I28_5.22_7%_5day_85C NV19I28_5.22_7%_28day_85C NV19IBI3_5.22_7%_5day_85C NV19IBI3_5.22_7%_28day_85C PG58-28 (Unmodified) UTSST Resistance Index 1, 1, 1, 1 NV19IBI3_5.22_7%Va_85 C NV19I28_5.22_7%Va_85 C PG64-28 (SBS) PG58-28 (Unmodified) 2, 1 1, Temperature ( C) Aging Period at 85 C (Days) Slide 36

37 Test Sensitivity (Cont d) Effect of Recycled Materials 14, Modulus (MPa) 12, 1, 8, 6, 64-22_2%RAP 64-22_3%RAP 64-22_4%RAP 58-28_3%RAP 58-28_4%RAP 1, 9 UTSST Resistance Index , 2, Temperature ( C) Slide 37

38 Lab to Field Correlation WesTrack Mixes Consistencies observed between lab and field aging Example: WesTrack Sections (Diff. Binder and Aggs.) Section [19 yrs field aging] Sections 38 & [17 yrs field aging] Crack initiation stress (MPa) Lab Aging at 6 C up to 9 months 19 yrs CA WT95F22 (7-8% Va) WT15 Crack initiation stress (MPa) Crack initiation stress (MPa) CA WT97C22 (7-8% Va) WT Lab Aging at 6 C up to 9 months Lab Aging at 6 C up to 9 months 17 yrs 17 yrs CA WT97C22 (11-12% Va) WT56 Slide 38

39 Lab to Field Correlation CR 112 Olmsted County, Minnesota Sections Five test sections were constructed using same aggregate gradation and four binders from different sources. Section Binder MN 1-1 MIF PG (Elvaloy modified) with 2% RAP MN 1-2 MN 1-3 MN 1-4 MIF PG (Elvaloy modified) without RAP PG Canadian blend PG Arab heavy/arab medium/kirkuk blend Transverse and Longitudinal Cracking (m) MN 1-5 PG Venezuelan blend 5 MN 1-1 MN 1-2 MN 1-3 MN 1-4 MN Distress Survey Year Slide 39

40 Lab to Field Correlation CR 112 Olmsted County, Minnesota Sections (cont d) UTSST Resistance Index (5 Days Oven Aging of Compacted Specimen at 85 C) 1, 1, 1, 1 MN 1-5 MN 1-2 MN 1-1 MN 1-3 MN 1-4 R² = , Transverse and Longitudinal Cracking (m) (21) Transverse and Longitudinal Cracking (m) MN 1-1 MN 1-2 MN 1-3 MN 1-4 MN Distress Survey Year Slide 4

41 Lab to Field Correlation CR 112 Olmsted County, Minnesota Sections (cont d) UTSST Resistance Index (5 Days Oven Aging of Compacted Specimen at 85 C) 1, 1, 1, 1 MN 1-5 MN 1-2 MN 1-1 MN 1-3 R² =.5665 MN , Transverse and Longitudinal Cracking (m) (212) Transverse and Longitudinal Cracking (m) MN 1-1 MN 1-2 MN 1-3 MN 1-4 MN Distress Survey Year Slide 41

42 Lab to Field Correlation CR 112 Olmsted County, Minnesota Sections (cont d) UTSST Resistance Index (5 Days Oven Aging of Compacted Specimen at 85 C) 1, 1, 1, 1 MN 1-5 R² =.9384 MN 1-2 MN 1-1 MN 1-3 MN , Transverse and Longitudinal Cracking (m) (214) Transverse and Longitudinal Cracking (m) MN 1-1 MN 1-2 MN 1-3 MN 1-4 MN Distress Survey Year Slide 42

43 Lab to Field Correlation CR 112 and WesTrack UTSST Resistance Index 1, 1, 1, 1 WT97C22_5.1_4%_6C WT97C22_5.1_7%_6C WT97C22_5.1_11%_6C WT95F22_5.2_7%_6C UTSST Resistance Index 1, 1, 1, 1 Sec. 56 Sec. 15 MN Test Sections WT_Cores_214 WT22_3mo_6 C WTC_7% WTC_11% WTF_7% Sec Aging Period at 6 C (months) Long. and Trans. Crack Density [1/m] Slide 43

44 Summary and Conclusions Uniaxial Thermal Stress and Strain Test Test specimens obtained from SGC specimens or field cores. Orientation of specimens is preserved by subjecting tensile stresses perpendicular to compaction direction. Allow for the determination of: CTC, fracture strength/temperature, Crack initiation stress, UTSST Resistance Index, or other thermo-viscoelastic properties. Direct tension test under thermal loading. Full characterization of asphalt mixtures as a function of temperature (various thermal transition zones). Cooling rate can be selected to simulate field conditions. Slide 44

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