Importance of Tack Coat th Annual 39 39 th al Asphalt lt Paving - - PowerPoint PPT Presentation

▶
importance of tack coat
SMART_READER_LITE
LIVE PREVIEW

Importance of Tack Coat th Annual 39 39 th al Asphalt lt Paving - - PowerPoint PPT Presentation

Aug 26, 2023 445 likes •1.06k views

Importance of Tack Coat th Annual 39 39 th al Asphalt lt Paving ing Confer eren ence ce Charles rlesto ton, n, WV February ruary 28, 2019 19 Jason son Dietz, tz, Pavem vemen ent and d Materi erials als Engin gineer eer

slide-1
SLIDE 1

Importance of Tack Coat

39 39th

th Annual

al Asphalt lt Paving ing Confer eren ence ce Charles rlesto ton, n, WV February ruary 28, 2019 19

Jason son Dietz, tz, Pavem vemen ent and d Materi erials als Engin gineer eer Denver, nver, CO

slide-2
SLIDE 2

2014 – Pilot, VA Completed (47) Not Requested (4)

Tack Coat Workshops

CA CA AZ AZ CO CO NM NM TX TX OK OK AR AR LA LA MO MO KY KY AL AL GA GA FL FL VA VA OH OH MI MI VT VT AK AK VI VI MT MT NV NV Guam ME ME WA WA OR OR UT UT KS KS ID ID WY WY ND ND SD SD MN MN NE NE WI WI IA IA IL IL IN IN MS MS TN TN SC SC NC NC WV WV PA PA NY NY CT CT NJ NJ DE DE MD MD DC DC MA MA NH NH PR PR HI HI RI RI

2

slide-3
SLIDE 3

 FHWA Best Practices Tech Brief  AASHTO SOM Specification Was Submitted  NCHRP 20-05 Synthesis - Tack Coat Study  Increasing Application Rates  DOTs Specification Revisions

3

slide-4
SLIDE 4

 Going to Stiffer Base Asphalts (SS-1h CSS-1h)  Verifying Calibration of Distributor  Treat Tack as Separate Pay Item vs. Incidental

Item

 Tack Coat Pocket Guide (August 2019)

4

slide-5
SLIDE 5

5

slide-6
SLIDE 6

6

Survey results courtesy of Dave Johnson and Danny Gierhart of the Asphalt Institute

slide-7
SLIDE 7

Far too frequent practices.

7

slide-8
SLIDE 8

Uniform, complete, and adequate coverage

8

slide-9
SLIDE 9

 Terminology  Purpose of Tack Coats  Specifications  Materials/Products  Construction Practices  Testing and Acceptance

9

slide-10
SLIDE 10

 Undilute

iluted d Emulsi lsion

  • n—an emulsion which consists of

a paving grade asphalt binder, water, and an emulsifying agent.

 Diluted

ted Emul ulsion sion—an emulsion with additional water added to it. The most common dilution rate is 1:1 (one part undiluted emulsion and one part additional water).

 Residual

ual Asphal alt—the remaining asphalt after an emulsion has set, typically 57-70 percent of the undiluted emulsion.

Wh What at we ar are tal alking ing ab about: ut:

10

slide-11
SLIDE 11

 Tack Coat Break—the moment when water

separates enough from the asphalt to show a color change from brown to black.

 Tack Coat Se

Set—when all the water has evaporated, leaving only the residual

  • asphalt. Some refer to this as completely

broken.

11

slide-12
SLIDE 12

 T/F A Broken Emuls

lsion ion is the remaining asphalt after an emulsion has set.

12

slide-13
SLIDE 13

What’s wrong (if anything) with the following specification regarding application rate?:

“Apply the tack coat at a rate of 0.05 gallons/yd2”

13

slide-14
SLIDE 14

If the example spec intended 0.05 gal/yd2 of residual asphalt:

Undiluted emulsion applied at 0.05 gal/yd2 using an emulsion with 60% residual asphalt, leaves 0.03 gal/yd2 on the roadway?

40% less than intended

14

slide-15
SLIDE 15

If the example spec intended 0.05 gal/yd2 of residual asphalt:

Diluted Emulsion using the same emulsion diluted 1:1 with water and applied at 0.05 gal/yd2 leaves 0.015 gal/yd2 on the roadway?

70% less than intended

15

slide-16
SLIDE 16

If the example spec intended 0.05 gal/yd2 of residual asphalt:

To receive Residual Asphalt at 0.05 gal/yd2 using an emulsion with 60% residual asphalt, the contractor would need to apply:

0.083 gal/yd2 of Original Emulsion or 0.167 gal/yd2 of 1:1 Diluted Emulsion

16

slide-17
SLIDE 17

 To promote the bond between pavement

layers.

  • To prevent slippage between pavement layers.
  • Vital for structural performance of the

pavement.

  • All layers working together.
  • Apply along all transverse and longitudinal

vertical surfaces.

17

Why do we use Tack Coats?

slide-18
SLIDE 18

 Poor pavement performance

  • Early fatigue life

 Bottom up  Top down

  • Slippage cracks
  • Shoving

 Costly pavement repairs

  • Shorter than expected pavement life can be

devastating for agency budgets

  • Removal and replacement of a portion or the

entire pavement structure is very expensive

18

Direction of traffic?

slide-19
SLIDE 19

19

slide-20
SLIDE 20

Days later – significant slippage

20

Courtesy of Road ScienceTM

Shoving Surface Core

slide-21
SLIDE 21

21

Courtesy of MoDOT

slide-22
SLIDE 22

Most st agencie ncies s sp specify ify tack coat t ma materials rials us using ing the he followin llowing g AAS AASHTO TO sp spec ecific ifications ations

  • r

r so some me form rm of the hem: m:

 Asphalt Emulsions

  • M140 anionic emulsions
  • M208 cationic emulsions
  • M316 polymer-modified cationic

emulsions

 Straight Binders

  • M320 Performance Graded Asphalt Binder
  • M322 Performance-Graded Asphalt Binder

Using Multiple Stress Creep Recovery (MSCR) Test

22

slide-23
SLIDE 23

23

slide-24
SLIDE 24

1. 1.

CSS SS-1h 1h (52%) 2%)

2. 2.

Non

  • n-standard*

standard* (48% 8%)

3. 3.

SS SS-1h 1h (46% 6%)

4. 4.

SS SS-1 (36%) 6%)

5. 5.

CSS SS-1 (28% 8%)

24

  • Non-standard means that a state has come up with its own

nomenclature for an emulsion, outside those specified in AASHTO M 140 (Anionic Emulsions), M 208 (Cationic Emulsions), or M 316 (Polymer-Modified Cationic Emulsions) Examples: SS1hp, CRS-2h, EBL

slide-25
SLIDE 25

1. 1.

NTSS SS-1hm 1hm (24% 4%)

25

“Non-tracking tacks are designed to improve the pavement performance by avoiding the tracking problems associated with traditional tacks. This material is typically manufactured to harden quickly and adhere minimally to tires. When a hot lift of asphalt is subsequently placed over the tack, the hardened tack is reactivated by the heat, and bonds the new overlay with the existing surface.” (Seo, 2016) Others hers specified ecified (all ll by less ss than an 3% of the states tes) CBC-1H CBC-1HT EM-50-TT E-Tac NTCQS-HH NTCQS-1HM NTCRS-1HM NTCRS-1HSP NTHAP NTT PATT UltraFuse UltraTack

slide-26
SLIDE 26

Most agencies accept material using one or more of the following methods:

 Approved Source List

  • Specifies pre-approved products and sources
  • Typically maintained on the agency’s website

 Supplier Certification

  • Agency relies on supplier testing
  • Requires document certifying material meets

agency specs

 Testing of Samples

  • Samples from supplier or field project
  • Verify product meets AASHTO specs, some

agencies also verify performance via some form

  • f bond strength test

26

slide-27
SLIDE 27

27

slide-28
SLIDE 28

28

* Ho How w is ta tack measure ured d fo for pay? y??

slide-29
SLIDE 29

 Emulsion are the most commonly

used materials for tack coats

 Care needs to be taken to make

sure material doesn’t separate

  • Insulated storage tanks
  • Gentle agitation
  • Proper temperature range
  • Avoid contamination
  • Consult supplier for compatibility

information

29

slide-30
SLIDE 30

 Provides detailed findings on

agencies’ and contractors’ best practices

 Discusses:

  • Training and communication
  • Tack coat application rates
  • Dilution issues
  • Surface preparation
  • Application best practices
  • Asphalt distributors
  • Vehicle tracking of tack coat

30

slide-31
SLIDE 31

Agencies in the US are fairly evenly split regarding whether or not dilution is allowed

 Dilution Pros

  • Larger liquid volume allows easier flow
  • Larger liquid volume allows easier
  • verlap on “fans”

 Dilution Cons

  • Risk of losing control of the product
  • Requires additional time to break
  • Increases risk of tack flowing of

roadway surface

31

slide-32
SLIDE 32

32

slide-33
SLIDE 33

33

The FHWA/Asphalt Institute Tack Coat Workshops recommends dilution occur at the supplier’s terminal

slide-34
SLIDE 34

34

slide-35
SLIDE 35

Power brooming is the most commonly-used method of cleaning the roadway surface

35

slide-36
SLIDE 36

36

slide-37
SLIDE 37

37

slide-38
SLIDE 38

38

slide-39
SLIDE 39

39

slide-40
SLIDE 40

40

slide-41
SLIDE 41

41

slide-42
SLIDE 42

42

slide-43
SLIDE 43

43

slide-44
SLIDE 44

44

slide-45
SLIDE 45

45

slide-46
SLIDE 46

46

slide-47
SLIDE 47

47

slide-48
SLIDE 48

48

slide-49
SLIDE 49

49

slide-50
SLIDE 50

50

slide-51
SLIDE 51

 Check truck setup.

  • Spray bar height

(~12”)

  • Appropriate nozzles
  • Nozzle orientation

(15-30°)

  • Check application

rate gauge in truck

  • Check application

temperature

 Collect samples.  Know the desired

application and residual rates.

 Visually inspect

application

 Verify application.

  • Volume (most popular)
  • Mass
  • ASTM D2995

51

slide-52
SLIDE 52

 Layer Bonding is Vital  Surface Preparation

  • Clean
  • Dry

 Milling Improves Field Performance

  • Shear
  • Cleaning

52

slide-53
SLIDE 53

 When to Re

Re-Tack?

  • Tracking
  • Contamination

If in doubt … Re Re-Tack Tack

53

slide-54
SLIDE 54

 Wh

What is the Optimal mal Appl plication cation Rate?

  • Surface Type
  • Surface Condition

 Wo

Works kshop p Recommende ended d Ranges ges

Surface ace Type Residua ual l Rate (gsy) y) Ap

  • Appx. Bar Rate

Undilute uted* (gsy) y)

  • Appx. Bar Rate

Diluted ted 1:1* (gsy) y) New Asphalt 0.020 – 0.045 0.030 – 0.065 0.060 – 0.130 Existing Asphalt 0.040 – 0.070 0.060 – 0.105 0.120 – 0.210 Milled Surface 0.040 – 0.080 0.060 – 0.120 0.120 – 0.240 Portland Cement Concrete 0.030 – 0.050 0.045 – 0.075 0.090 – 0.150

*Assume emulsion is 33% water and 67% asphalt.

54

slide-55
SLIDE 55

 Application Quality Vital

  • Proper Rate
  • Consistency

 Distributor Truck

  • Setup
  • Calibration/Verification
  • Maintenance

 Tacking of Longitudinal Joints

  • Bonding
  • Confinement

 Excessive Tack is Bad

55

slide-56
SLIDE 56

 Tack Coat Rate Depends on Surface Condition

  • Fresh
  • Weathered
  • Raveled
  • Milled

 Need for Research

  • Field Performance
  • Field Testing

 Bond strength  Application amount

 Treat

at Tack as Separ arat ate e Pa Pay y Item m vs

  • vs. Incidental

idental Item

56

slide-57
SLIDE 57

Pavemen ment t & Materia rials ls Technical Service Team

57

slide-58
SLIDE 58

NHI 131139 Training

Inspecting Asphalt Pavement Construction Projects course will be available May 2019

Pavemen ment t & Materia rials ls Technical Service Team

58

slide-59
SLIDE 59

59

slide-60
SLIDE 60

60