Asphalt 101 Materials: HMA Part 1. Rocky Mountain Asphalt Conference and Equipment Show. February 24, 2011

Transcription

1 Asphalt 101 Materials: HMA Part 1 Rocky Mountain Asphalt Conference and Equipment Show February 24,

2 SUPERPAVE 2

3 SUPERPAVE 2

4 SPECIFYING PERFORMANCE Based on Climate PG Performance Grade Min pavement temperature, C Rolling average 7-day max pavement temperature, C 3

5 To characterize (test) a PG binder individual tests - 6 major pieces of equipment - 3 conditioning steps - ~25 hours total time elapse 4

6 PG Binder Tests vs. Temperature BBR & DTT (Thermal Cracking Resistance) DSR Intermediate Temperature (Fatigue Resistance) DSR High Temperature (Rutting Resistance) Brookfield Viscosity (Workability) Cold Pavement Temperature, C Hot

7 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

8 Aging Asphalt reacts with oxygen Becomes harder, more brittle More Elastic, Less Viscous Short term During Mixing with Aggregates (280F-330F) Long term In Pavement Air, Water, Sun 7

9 Asphalt Plant and Construction Aging Rolling Thin Film Oven (RTFO) Fan Rotating Bottle Carriage Blowing Air 8

10 Pressure Aging Vessel 50 grams of Asphalt in Each Pan Pressure Aging Vessel 9

11 Pressure Aging Vessel Courtesy of FHWA 10

12 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

13 Is the binder safe to be heated? Construction RV 12

14 Cleveland Open Cup Flash Point Tester 13

15 Spec Requirement Binder safe to be heated... Cleveland Open Cup (COC) Flash Point must be greater than 232 o C (450 o F). 14

16 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

17 Will it Flow for Mixing? Construction RV 16

18 Rotational Viscometer (Brookfield) Torque Motor Inner Cylinder Thermosel Environmental Chamber Digital Temperature Controller 17

19 Spec Requirement Make sure binder is not too thick to pump... Keep Viscosity Below 3 Pa-sec at 135 o C (275 o F) 18

20 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting, Hardening Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

21 Permanent Deformation ( ) Courtesy of FHWA Caused by Warm Weather, Traffic and Wrong Mixture 20

22 High temperature or, slow loading behavior, Rutting High Pavement Temperature Desert climates Summer temperatures Sustained loads Slow moving trucks Intersections 100 F 21

23 Dynamic Shear Rheometer (DSR) Rutting, Hardening, and Fatigue 22

24 Asphalt Glued In- Between Oscillating Upper Plate B A C Fixed Lower Plate 1 cycle 23

25 Asphalt Glued In- Between Oscillating Upper Plate B A C Fixed Lower Plate Time 1 cycle 23

26 Asphalt Glued In- Between Oscillating Upper Plate B A C Fixed Lower Plate B A A A Time 1 cycle C 23

27 Asphalt Glued In- Between B B A C Oscillating Upper Plate Fixed Lower Plate Now, Measure the Force Required to Rotate the Upper Plate And, Measure When Movement Occurs in the Binder A A A Time 1 cycle C 23

28 24

29 Elastic Time 24

30 Elastic B Stress A Strain A A Time Strain Occurs With Stress δ = 0 o C 24

31 Elastic Viscous B Stress A Strain A A Time Strain Occurs With Stress δ = 0 o C 24

32 Elastic Viscous B Stress B A Strain A A Time A A A C C Strain Occurs With Stress δ = 0 o 24

33 Elastic Viscous B Stress B A Strain A A Time A A A Strain Occurs With Stress δ = 0 o C C Strain Lags Stress δ = 90 o 24

34 δ 25

35 δ Elastic, G 25

36 δ Viscous, G Elastic, G 25

37 Complex Modulus, G* δ Viscous, G Elastic, G Complex Modulus is the vector sum of Elastic and Viscous Components 25

38 Spec Requirement Mitigate rutting by... G*/sin δ on Unaged binder > 1.00 kpa G*/sin δ on RTFO Aged binder > 2.20 kpa Early part of pavement life 26

39 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

40 Caused by repeated traffic loads in wheel paths Fatigue Cracking 28

41 Spec Requirement Reduce Fatique Cracking by... G*sin δ on RTFO & PAV aged binder < 5000 kpa Later part of pavement service life 29

42 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

43 Thermal Cracking Courtesy of FHWA Caused by Low Temperatures, Rapid Loads, Hard Binder 31

44 Low Temperature, or Fast Loading Behavior-aka Cracking Low Temperature Cold climates Winter Rapid Loads Fast moving trucks σ Cracking Failure ε 32

45 Bending Beam Rheometer Thermal Cracking RV BBR 33

46 Bending Beam Rheometer Computer Deflection Transducer Load Cell Fluid Bath 34

47 BBR Measures Stiffness at Low Temperatures using Beam Theory Creep stiffness at t = 60 secs 100 grams Clear Span of Beam, 102 mm S(t) = PL 3 4 bh 3 δ (t) Deflection at t = 60 secs Beam Width, 12.5 mm Beam Thickness, 6.25 mm 35

48 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope 36

49 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope Log Creep Stiffness, S(t) Log Loading Time, t (sec) 36

50 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope Log Creep Stiffness, S(t) Log Loading Time, t (sec) 36

51 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope Log Creep Stiffness, S(t) Log Loading Time, t (sec) 36

52 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope Log Creep Stiffness, S(t) Log Loading Time, t (sec) 36

53 Bending Beam Rheometer Creep Stiffness Stiffness v. Time Slope Log Creep Stiffness, S(t) m Log Loading Time, t (sec) 36

54 Spec Requirement Protect against cracking... BBR m value > BBR S value < 300 MPa 37

55 Binder Test Sequence Binder Condition Test For Unaged Binder Flash Rot Vis DSR Safety Handling Rutting RTFO Aged PAV Aged DSR LOH DSR BBR DTT Rutting Environment / Aging Fatigue Damage Thermal Cracking Thermal Cracking

56 Thermal Cracking Question: How Much Should the Asphalt Be Able to Stretch before Breaking? Answer: at least 1% (in Colorado possibly even more) How: Find the Temperature Where the Asphalt Can Stretch 1% or More 39

57 Direct Tension Test Load Stress = σ = P / A Δ L σ f Δ L e Strain ε f 40

58 Conventional AC Grades vs. SHRP Performance Grades (typical comparisons) AC-5 AC-10 AC-20 AC-40 PG PG PG PG Typical (not absolute) for unmodified asphalts only

59 42