Superpave TM Asphalt Binders. Chapter 6-2

Transcription

1 Superpave TM Asphalt Binders Chapter 6-2

2 Traditional Grading Temperature ( C) Viscosity (cp)

3 Performance Grading Temperature ( C) Dynamic Shear Modulus (kpa)

4 Superpave Grading Uses fundamental physical and mechanical properties, not index properties Performance-based: criteria remain constant but the test temperature changes Lowest 1-day temperature Highest 7-day temperature Explicitly addresses aging, thermal cracking, fatigue cracking and rutting CIVL

5 Superpave Grading Equipment Rotational Viscometer Dynamic Shear Rheometer Rolling Thin-Film Oven Pressure Aging Vessel Bending Beam Rheometer Direct Tension Tester Purpose Properties at construction temps Properties at high service temps Aging due to volatilization Aging due to oxidation Properties at low service temps Properties at low service temps CIVL

6 Performance Grading CIVL

7 Performance Grading CIVL

8 Rotational Viscometer 20 rpm Can be used with modified or unmodified binders w/out clogging The viscosity of the unaged binder must be less than 3000 cp at 135ºC for good pumping and mixing CIVL

9 Viscosity of Common Liquids Water Cream Vegetable Oil Tomato Juice Honey Chocolate Syrup Sour Cream Ketchup Peanut Butter Vegetable Shortening 1 centipoise 20 centipoise 100 centipoise 200 centipoise 2000 centipoise centipoise centipoise centipoise centipoise centipoise CIVL

10 Rotational Viscometer CIVL

11 Dynamic Shear Rheometer Applied Stress Applied Stress 1.59 Hz time Fixed plate 46 o C to 82 o C CIVL

12 Dynamic Shear Rheometer CIVL

13 Dynamic Shear Rheometer Stress time Stress time Strain time Strain time Elastic Solid = 0 deg Viscous Liquid = 90 deg CIVL

14 Dynamic Shear Rheometer max Stress t G * max min time min max min Strain max time f t min CIVL

15 Dynamic Shear Rheometer Applied Stress G*/sin of unaged binder must exceed 1.00 kpa at the high service temperature to prevent rutting Fixed plate CIVL

16 Rolling Thin-Film Oven 85 min Air Jet 325 o F Sample Bottle Simulates aging of asphalt cement during mixing and laydown CIVL

17 Rolling Thin Film Oven CIVL

18 Dynamic Shear Rheometer Applied Stress G*/sin of the stiffer RTFO-aged binder must exceed 2.2 kpa at the high service temperature to prevent rutting Fixed plate CIVL

19 Pressure Aging Vessel 20 hours 2070 kpa sample pan air o C Simulates aging of asphalt cement over years due to oxidation CIVL

20 Dynamic Shear Rheometer Applied Stress G* sin of the stiffer PAV-aged binder must be less than 5000 kpa at the mean of the high and low temperatures to prevent fatigue cracking Fixed plate CIVL

21 Bending Beam Rheometer 100 g Air Bearing P Fluid Bath D 0ºC to -36 o C t CIVL

22 Bending Beam Rheometer S t P t L 3 3 4bh D t P Creep Stiffness D t CIVL

23 Bending Beam Rheometer CIVL

24 Bending Beam Rheometer CIVL

25 Bending Beam Rheometer 100 g Fluid Bath Air Bearing S(t) of the PAV-aged binder must not exceed 300 MPa after 2 hours at the low service temperature to prevent thermal cracking 0ºC to -36 o C CIVL

26 Direct Tension Tester L eff L eff + L f L L eff 0ºC to -36 o C CIVL

27 Direct Tension Test CIVL

28 Direct Tension Test CIVL

29 Direct Tension Tester f of the PAV-aged binder must exceed 1% at the low service temperature to prevent thermal cracking CIVL

30 Superpave Grading High Grades PG 46 PG 52 PG 58 PG 64 PG 70 PG 76 PG 82 Low Grades 34, 40, 46 10, 16, 22, 28, 34, 40, 46 16, 22, 28, 34, 40 10, 16, 22, 28, 34, 40 10, 16, 22, 28, 34, 40 10, 16, 22, 28, 34 10, 16, 22, 28, 34 Typical Performance Grade PG CIVL

31 Superpave Grade Selection PG70-22 PG Lowest 1-day Pavement Temperature Highest 7-day Pavement Temperature CIVL

32 Normal Probability Distribution Standard Deviations CIVL

33 Normal Probability Distribution PG % 30% Temperature ( C) CIVL

34 Superpave Grade Selection Reliability = (0.84)(0.70) = 59% PG64-16 ~16% ~84% ~70% ~30% Lowest 1-day Pavement Temperature Highest 7-day Pavement Temperature CIVL

35 Superpave Grade Selection PG70-22 Reliability = (1.00)(0.98) = 98% ~0% ~100% ~98% ~2% Lowest 1-day Pavement Temperature Highest 7-day Pavement Temperature CIVL

36 Superpave Binder Grades CIVL

37 Superpave Binder Grades $ $ $ Cost per ton based on TDOT reimbursement rates for October 2012 CIVL

38 Grade Bumping PG PG PG PG CIVL