Moisture Damage to Hot Mix Asphalt

Transcription

1 Moisture Damage to Hot Mix Asphalt Keeping Asphalt Stuck to the Rock Gerry Huber Heritage Research Group

2 Durability

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4 Durability Aging (Oxidation) of Asphalt Binder Cracking Raveling Moisture Damage Asphalt Binder Stripping from Aggregate Asphalt Binder Softening

5 Durability Aging (Oxidation) of Asphalt Binder Cracking Raveling Moisture Damage Asphalt Binder Stripping from Aggregate Asphalt Binder Softening

6 Understanding How Asphalt Sticks Listen, it s only $1800 for the fuel pump. It could have been the transmission!

7 How Does Anything Stick?

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9 Aggregate Active Sites First Thoughts Limestone has more active sites Granite has fewer active sites WRONG

10 Aggregate Active Sites First Thoughts Limestone has more active sites Granite has fewer active sites WRONG Both have same number of sites

11 Bonding Energy How strong is the bond?

12 Bonding Energy How strong is the bond?

13 Bonding Energy How strong is the bond?

14 Moisture in Pavement

15 Asphalt is Waterproof?? 1.50 AAM AAG AAD Water Content, % Time, hr Source: WRI 2001

16 Asphalt is Waterproof?? % water AAM AAG AAD Water Content, % days Time, hr Source: WRI 2001

17 Affinity for Asphalt Hydrophilic (water loving) granite, quartzite Hydrophobic (water hating) limestone, dolomite

18 Affinity for Asphalt Hydrophilic (water loving) granite, quartzite Hydrophobic (water hating) limestone, dolomite Strong Bond Weak Bond

19 Stripping

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22 Asphalt Stiffness How Does it Work? Hydrogen Bonding Effect of Water

23 Asphalt Molecule Bonds Stir Magnets

24 Asphalt Molecule Bonds Stir Magnets

25 Asphalt Molecule Bonds

26 Asphalt Molecule Bonds Hydrogen Bonding

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31 Moisture Content Discharge Truck at Plant After MTV Moisture Content, % 255 F 310 F 330 F

32 Moisture Content Less than Discharge Truck at Plant After MTV Moisture Content, % 0.1% moisture 255 F 310 F 330 F

33 Effect of Moisture on Stiffness Normalized Percent Change in G* Time, hr AAM AAG AAD Source: WRI 2001

34 Asphalt Binder Softening Hydrostatic Pressure Binder Migration

35 Asphalt Binder Softening Hydrostatic Pressure Binder Migration

36 Bob McGennis 2013

37 Bob McGennis 2013

38 Moisture Damage Breaking of Asphalt Aggregate Softening of Asphalt Binder Rutting (Flushing)

39 Preventing Moisture Damage Prevent Trapping Water in Pavement Strengthen Asphalt Bond

40 Strengthen Asphalt Bond Treat Aggregate Lime Treat Asphalt Liquid Anti-Strip

41 Treat Aggregate Lime has high ph Increases bonding energy Typically 0.5 to 1.5% by wt. aggregate

42 Lime Slurry

43 Treat Asphalt Binder Typically an Amine Nitrogen containing compound Amine bonds to aggregate Asphalt binder bonds to amine 0.25 to 0.75% by wt. asphalt

44 Tests Used Boil Test Retained Tensile Strength (AASHTO T283) Hamburg Rut Tester

45 Boil Test Loose Mix Place in Boiling Water High Temperature Softer Asphalt, More Loss Nothing to do with Moisture Damage Method Sensitive Heat Source Container

46 AASHTO T283 Compacted Samples Vacuum Saturation Soak Time Influenced by Density Additives Reduce Strength Minimum Wet Strength Not Moisture Damage

47 Hamburg Rut Tester

48 Hamburg Rut Tester

49 Hamburg Rut Tester

50 Hamburg Rut Tester Generally considered too severe Steel Wheel more Severe Rubber Wheel less Severe Influenced by Asphalt Grade Hard asphalt better

51 What s the best?

52 What s the best? TAKE YOUR PICK

53 Conclusion Moisture Damage Caused by low bonding energy Treatments improve bonding energy Tests are less precise than desired Caused by asphalt softening Prevent pavement saturation

54 Conclusion Moisture Damage Caused by low bonding energy Treatments improve bonding energy Tests are less precise than desired Caused by asphalt softening Prevent pavement saturation Thank You