Performance Graded Asphalt Binders Bob Horan, P.E. Consulting Engineer Mechanicsville, VA

Transcription

1 Performance Graded Asphalt Binders Bob Horan, P.E. Consulting Engineer Mechanicsville, VA October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 1

2 What is Asphalt? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 2

3 The 3 A s of Hot Mix Asphalt Asphalt, Aggregates, and Air HMA = Asphalt + Aggregates + Air October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 3

4 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 4

5 What is Asphalt? Called different things Bitumen Asphalt Liquid Asphalt Asphalt Cement Asphalt Binder Binder But mean basically the same thing! October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 5

6 Background Asphalt Soluble in petroleum products Generally a by- product of petroleum distillation process Can be naturally occurring Tar Resistant to petroleum products Generally by- product of coke (from coal) production October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 6

7 Asphalt - Definition: A dark brown to black cementitious material in which the predominating constituents are bitumens which occur in nature or are obtained in petroleum processing. (ASTM D8) October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 7

8 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 8

9 Brief History B. C. Extensive use in Mesapotamia and Indus Valley as cement for masonry and street construction and as waterproofing agent 300 B.C. Used for mummification in Egypt 1870 First asphalt pavement laid in Newark, New Jersey 1876 First sheet asphalt pavement laid in Washington, DC with imported lake asphalt 1902 Approx. 20,000 tons of asphalt refined from petroleum in United States Now Over 30,000,000 tons produced in U.S. October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 9

10 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 10

11 Refining produces asphalt with specific characteristics for varied uses Asphalt Sources Paving asphalt Roofing asphalt Other special uses Waterproofing Sealing October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 11

12 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 12

13 Sources of Asphalt Natural asphalt deposits Petroleum asphalts October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 13

14 Asphalt Types Natural asphalt deposits Natural evaporation of volatile portions of petroleum leaving the asphalt fractions Lake asphalt Trinidad Bermudez Rock asphalt Natural asphalt deposits in porous rock October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 14

15 Trinidad Lake Asphalt October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 15

16 Background Each lake asphalt source very consistent Used solubility test to determine source Insolubles differed substantially between sources Demand for paved roads exceeded the supply of lake asphalts in late 1800 s Led to use of petroleum asphalts October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 16

17 Petroleum Asphalt Asphalt is one of the products of the petroleum industry October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 17

18 Petroleum-Based Asphalts Asphalt is waste product from refinery processing of crude oil Sometimes called the bottom of the barrel Properties depend on: Refinery operations Composition crude which are source-dependent Barrel of Crude Oil Gasoline Kerosene Lt. Gas Oil Diesel Motor Oils Burner Fuel Asphalt October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 18

19 Refinery Operation LIGHT DISTILLATE FIELD STORAGE TOWER DISTILLATION REFINERY PUMPING STATION MEDIUM DISTILLATE HEAVY DISTILLATE STORAGE GAS TUBE HEATER CONDENSERS AND COOLERS RESIDUUM OR PROCESS UNIT ASPHALT CEMENTS PETROLEUM SAND AND WATER AIR AIR BLOWN ASPHALT FOR PROCESSING INTO EMULSIFIED AND CUTBACK ASPHALTS October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 19 STILL

20 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 20

21 Asphalt Binder Behavior Temperature Time of Loading Aging is also important October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 21

22 Asphalt Binder Behavior Consistency Semi-Solid Solid Asphalt is a thermoplastic material that softens as it is heated and hardens when cooled. Liquid Temperature October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 22

23 Asphalt Binder Behavior Stiffness (Response to Load) elastic Asphalt has Viscoelastic Properties viscous elastic solid? viscous fluid Temperature, C October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 23

24 Asphalt Binder Behavior 60 C 1 hour Time versus Temperature (MS-22, Fig. 2.03) Flow 25 C 1 hour 10 hours October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 24

25 Binder Behavior - Aging Asphalt Reacts with Oxygen Long and Short Term oxidative or age hardening During Construction - Short Term hot mixing placing/compaction In Service - Long Term hot climate worse than cool climate summer worse than winter Volatilization- Short Term volatile components evaporate during construction October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 25

26 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 26

27 Early Specifications Lake Asphalts Appearance Solubility in carbon disulfide Petroleum asphalts (early 1900 s) Consistency Chewing Penetration machine Measure consistency October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 27

28 Penetration Grading Viscosity 0 sec 100 g penetration 5 sec 100 g Typical Pen Grades October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 28

29 Viscosity Grading Viscosity vacuum Typical Vis Grades AC - 20 AC - 10 October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 29

30 Stiffness of three different asphalts hard pen Penetration Test soft A B C Temperature, C October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 30

31 Stiffness of three different asphalts hard pen vis Penetration and Viscosity Test soft vis A B C Temperature, C October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 31

32 Problems with Current System Viscosity viscous effects only at 60 C Penetration empirical consistency only at 25 C No Low Temperature Properties Measured October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 32

33 Problems with Current System Problems with Modified Asphalt Characterization Specification Proliferation Long Term Aging not Considered October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 33

34 Asphalt Overview Terminology History Uses Background Asphalt Behavior Classification (Grading) of Asphalt Asphalt Modification October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 34

35 Why Modify Asphalt? Change effects of temperature and loading on physical properties of asphalt Provides a stiffer binder at high temperatures (higher PG binder grade) Reduce effects of aging/oxidation on asphalt properties Improve adhesion to aggregates October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 35

36 Modified PG Binders Many different types of modified binders elastomers (Stylink, Citgoflex, others) -SBS,SBR plastomers (Novophalt, Vestoplast, others) gelled (Multigrade) blown, oxidized Little performance history with some modifiers Use of modified binder grades will increase cost (materials cost $2 - $5/ton of mix) Is it worth the extra cost? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 36

37 When should a modified binder be specified? In extreme climatic conditions (very hot or very cold) In very heavy traffic conditions, especially when loading is slow or stopped In problem situations where rutting, shoving, instability is occurring Where improved elastic properties are needed (i.e. resistance of reflective cracking) To provide for thicker binder film thickness in open graded and gap graded mixes October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 37

38 What is Asphalt? Black, glue-like, like, waterproof material A product of the petroleum refining operation Used extensively in the paving, roofing industries Is a thermoplastic material Must be in liquid form for roadway applications (heat, dilution in solvent, emulsification) Can be used in pavements effectively in the full range of climate and loading conditions Can be polymer modified to improve properties for better performance when necessary October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 38

39 Performance Graded Binders History Testing Specification Grade Selection October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 39

40 HMA Binders- Performance Graded (PG) System Product of Strategic Highway Research Program (SHRP) New tests and specification Provides a temperature range through which the asphalt must meet certain physical properties to resist rutting and cracking Includes conditioning procedures to simulate changes in asphalt properties due to aging in the field October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 40

41 Illustration of PG Binder Tests Low Temp. Cracking Fatigue Cracking Rutting Handling Pavement Temperature, C October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 41

42 Low Temperature Cracking October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 42

43 Alligator Cracking (Fatigue) October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 43

44 Rutting in Subgrade or Base October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 44

45 Rutting in Asphalt Surface Layer October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 45

46 Rutting at a Roundabout In what layer is rutting occurring? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 46

47 Superpave Asphalt Binder Specification Grading System Based on Climate PG Performance Grade Average 7-day7 max pavement design temp Min pavement design temp October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 47

48 Performance Graded Binder Specifications Superior to viscosity and penetration grading systems Have resulted in higher quality binders Allow appropriate grade of binder for specific location based upon: air and pavement temperature loading conditions traffic speed October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 48

49 Construction Rutting Fatigue Cracking Low Temp Cracking [DTT] [RV] [DSR] [BBR] Pavement Age No aging RTFO - aging PAV - aging October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 49

50 Rolling Thin Film Oven controls fan 163 C air jet bottle carriage October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 50

51 Pressure Aging air pressure Vesselessel temperature probe asphalt pressure vessel sample rack sample pan October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 51

52 Rotational Viscometer applied torque from motor sample chamber spindle asphalt sample October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 52

53 DSR Test Equipment Binder Sample Oscillating Plate Fixed Base Plate October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 53

54 Deflection Transducer Control and Data Acquisition Asphalt Beam Air Bearing Load Cell Fluid Bath emperature Probe Loading Frame Supports October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 54

55 Direct Tension Tester L L e Load Failure L + L L failure strain (ε( f ) = change in length ( ( L) effective gauge length L e October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 55

56 Performance Grades CEC Avg 7-day Max, o C 1-day Min, o C > 230 o C < o C PG 46 PG 52 PG 58 PG 64 PG 70 PG-76 PG ORIGINAL (Flash Point) FP (Rotational Viscosity) RV > 1.00 kpa > 2.20 kpa 20 Hours, 2.07 MPa < 5000 kpa S < 300 MPa m > (Dynamic Shear Rheometer) DSR G*/sin (ROLLING THIN FILM OVEN) RTFO Mass Loss < 1.00 % (Dynamic Shear Rheometer) DSR G*/sin (PRESSURE AGING VESSEL) PAV (110) 100 (110) 110 (110) (Dynamic Shear Rheometer) DSR G* sin ( Bending Beam Rheometer) BBR S Stiffness & m - value Report Value > 1.00 % (Bending Beam Rheometer) BBR Physical Hardening (Direct Tension) DT October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 56

57 Which PG grades should I use at my facility??? Many factor to consider Suggested grades from Superpave Weather Database Amount and type of traffic loadings Desired reliability Reclaimed Asphalt Pavement (RAP) usage Current available grades Capabilities of binder suppliers Typical types of distress in pavements Binder costs October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 57

58 Developed from Air Temperatures > 20 years SHRP A-648A Superpave Weather Database 6500 stations in U.S. and Canada Annual air temperatures hottest seven-day temp (avg. and std dev) coldest temp (avg. and std dev) Calculated pavement temperatures used in PG selection October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 58

59 Effect of Loading Rate on Binder Selection 90 kph Dilemma specified DSR loading rate is 10 rad/sec what about longer loading times? Use binder with more stiffness at higher temps slow - - increase one high temp grade stationary - - increase two high temp grades no effect on low temp grade October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 59

60 Effect of Loading Rate on Binder Selection Example with heavy loading for toll road PG for toll booth PG for weigh stations PG kph Slow Stopping October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 60

61 Effect of Traffic Amount on Binder Selection 80 kn ESALs x 10 6 ESAL Consider increasing -- one high temp grade 30 x ESAL Recommend increasing -- two high temp grades > Equivalent Single Axle Loads October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 61

62 Superpave Asphalt Binder Specification Grading System Based on Climate PG Performance Grade Average 7-day7 max pavement design temp Min pavement design temp October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 62

63 Which PG asphalt should perform best in resisting PG PG PG PG thermal cracking? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 63

64 Which PG asphalt should perform best in resisting PG PG PG PG thermal cracking? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 64

65 Which of the following PG binders should perform best in resisting rutting? PG PG PG PG October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 65

66 Which of the following PG binders should perform best in resisting rutting? PG PG PG PG October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 66

67 Superpave Binder Implementation 1999 Lead State Survey Undetermined October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 67

68 PG Binders in South Carolina Adopted in 2000 for all work Two grades selected: PG Low volume secondary, primary and interstate pavements PG Heavy loaded interstate and specealty locations (intersections) October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 68

69 Performance Graded Binder Testing, Specification and Grade Selection Questions? October 30, 2003 T3S - Superpave for Low Volume Roads - R. Horan 69