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Best Practices for Compaction and Rolling Patterns-Webinar
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2. Best Practices for Compaction

3. Compaction Goals
Density
Smoothness
High stability

4. Compaction WHY? Improve mechanical stability
Improve resistance to rutting
Reduce moisture penetration
Improve resistance to cracking

5. Compaction Forces PRESSURE: a downward force IMPACT: a hammer blow
VIBRATION: a rapid series of impact blows
MANIPULATION: kneading in a confined manner

6. Pneumatic Tire Roller or Static Steel Wheel Rollers
Compaction Train
4 Phases of Compaction
Screed
Breakdown Roller
Vibratory Steel Wheel
Intermediate Roller
Pneumatic Tire Roller or
Vibratory Steel Wheel
Finish Roller
Static Steel Wheel Rollers

7. Compaction Train 4 Phases of Compaction Screed Intermediate Roller
Key to smooth pavements
Provides initial compaction
Intermediate Roller
Primary role: lock up the aggregate structure
Pneumatic or steel wheeled
Breakdown Roller
Primary role: compaction
Usually vibratory steel wheeled roller
Finish Roller
Primary role: smoothness
Get out marks left from other rollers
Static steel wheeled

8. Types of Rollers Steel Wheel Roller (Vibratory and Static)
Pneumatic Roller (Rubber Tired Roller)

9. Steel Wheel Breakdown roller
Provides a compaction force by a combination of weight and vibration of their steel drums
Vary in weight (7-17 tons)
Vary in size (2-5 ft. drum diameter/4-8 ft. drum width)
Operation modes
Static (vibrating off)
Single drum vibrating
Both drums vibrating

10. Steel Wheel Roller
Amplitude: the greatest movement in one direction (up or down) of a vibrating roller drum from a position of rest
Frequency: the number of vibrations (downward impacts per minute)
Impact spacing: should be between 10 and 14 impacts per foot
Direction: the eccentric weight should rotate in the same direction as the drum

11. Steel Wheel Roller Distance the drum moves is called amplitude
Amplitude determines impact force
Higher the amplitude, Higher the force

12. Steel Wheel Roller Frequency is the number of drum impacts per minute
Typically from 10 to 14 impacts per foot

13. Vibrating Tachometer can be use to check the VPM (Vibrations Per Minute)

14. Vibrator Roller IMPACTS PER FOOT Frequency 2 MPH 3 MPH 4 MPH 5 MPH
2000 vpm
11.36
7.58
5.68
4.55
2200 vpm
12.50
8.33
6.25
5.00
2400 vpm
13.64
9.09
6.82
5.45
2600 vpm
14.77
9.84
7.39
5.91
2800 vpm
15.91
10.61
7.95
6.36
3000 vpm
17.05
8.52
3200 vpm
18.18
12.12
7.27
3400 vpm
19.32
12.88
9.66
7.72
3600 vpm
20.45
10.22
8.18
3800 vpm
21.59
14.39
10.80
8.63

15. Pneumatic Roller
Use rubber tires to compact through a kneading action (force of manipulation)
May be used in all phases of compaction, but is mostly used during the Intermediate Phase
Warm tires before compacting to avoid pickup

16. Pneumatic Roller
Overlap of tires manipulates mat under and between tire
Tight finish of mat lowers air voids

17. Pneumatic Roller Vary in weight (10 to 35 tons)
3 or 4 rubber tires on front axle
4 or 5 rubber tires on back axle
Wheels move up and down independently of each other
Weight per wheel varies from 3000 to 3500 lbs.

18. Pneumatic Roller Tires must be inflated to equal pressure
psi (range)
70 psi (tender mix)
90 psi (stiff mix)
Warm tires before compacting hot mix
Skirts keep tires warm during the day

19. Pneumatic Roller Low tire pressure = low force
High tire pressure = high force

20. Finish Roller Vary in size and weight
3 to 10 tons
8 tons typical per unit
3 to 5 foot diameter wheels
Heavier rollers may be used during the Breakdown Phase of compaction
Finish rollers may be used for the Last Phase of compaction
Drums must be smooth and clean
Vibratory rollers can run in static mode

21. Compaction Factors Mix Properties Layer Thickness
Aggregate
Asphalt
Mix Temperature
Layer Thickness
Environmental Factors
Rollers

22. Aggregate Structure

23. Asphalt Liquid Common Performance Grade (PG)
PG (usually not modified)
PG (almost always modified)
PG (almost always modified)

24. Mix Temperature Major effect on compaction
Compact the mix while the asphalt is still fluid enough to allow aggregate movement

25. Mix Temperature/Too Hot
Look for bulges in front of drum
Mat will move around and not compact
Rollers may leave deep marks
Stay back from paver until mat cools (tender zone)

26. Mix Temperature/Too Cold
No mixture movement possible
Densities results will vary
Try:
Working closer to paver
Increase the force
Add rollers

27. Environment Effects Air Temperature Surface Temperature
Weather conditions influence the roller type and size
Wind has a major effect on compaction !

28. Environment Hot weather: the mix stays workable longer
Cold weather: crust forms early and force is less effective
Adjust the rolling pattern as conditions change
Less Force
More Force

29. 4 inch Lift Thickness to 1 inch Nom Aggregate Size
Thickness effects ability to compact the mat and achieve density
Table 12 in Item 341 lists min. & max lift thickness
General rule of thumb, 4 times nominal max aggregate size
Example of 4:1 Ratio
4 inch Lift Thickness to 1 inch Nom Aggregate Size

30. Thick - Lift Thickness
Thicker lifts are more difficult to achieve uniform density from top to bottom
Try: higher amplitude setting
More than 2 inches thick

31. Thin - Lift Thickness Less than 2 inches
Thinner lifts are more difficult to achieve density
Using rollers in vibratory mode may crush aggregate
Try:
Static mode
Lower amplitude
Less than 2 inches

32. Compaction Etiquette

33. Overlaps A minimum of 6” overlap assures uniform compaction
Roller should cover mat in 2 to 3 overlapping passes

34. Mat Compaction Always start from bottom and work up on sloped mat
Adds support for successive passes

35. Best Practices
Never park a roller on a hot mat (deep marks will not roll out)
Never turn drums while the roller is stopped
Stop the roller at 30 – 45 degree angle and turn toward center of mat when necessary
Park back on compacted mat or on shoulder

36. Best Practices
Never roll off an unconfined edge (A collapsed edge will create a joint failure)

37. Best Practices Dry drums pick up hot mix Proper spray Use clean water
Change filters
Check spray nozzles
Only use approved release agent

38. Drum Ringing Too many vibratory passes Reduce number of passes
Lower amplitude

39. Roller Crawling Applying too much force
Lower amplitude and or adjust frequency

40. Tires cooling down or cold tires will pick-up hot mix

41. Prevent Pick-Up Keep tires hot Use approved release agents
Apply to clean tires before rolling begins

42. Prevent Pick-Up The use of tire skirts help keep tires hot
The use of squared profile tires eliminate tire marking and cupping from rounded bias ply

43. Roller Speed Slow and steady
Slower speed will give more compactive effort
It’s better to add rollers than to speed up rollers to catch paver

44. Roller Speed

45. Roller Patterns
Uniform compaction depends upon getting the same number of roller passes over each area of the mat
A pattern must be developed that covers the entire mat with an equal number of roller passes from each type of roller

46. Roller Patterns To ensure effective compaction of the mat
SETTING ROLLER PATTERNS
To ensure effective compaction of the mat
To achieve specified density requirements
To select the optimum combination of rollers and number of passes for each type of roller

47. Tex-207-F, Part IV, Control strip method
ESTABLISHING ROLLER PATTERNS

48. Tex-207-F, Part IV

49. Allow the roller to complete (2) coverages of the entire control strip
Tex-207-F, Part IV
Allow the roller to complete (2) coverages
of the entire control strip

50. Tex-207-F, Part IV Pass1 Pass 2 Pass 5 Pass 3 Pass 4
Width of mat
Pass1
Pass 2
Pass 5
Pass 3
Pass 4
5 pass pattern which provides 1 complete coverage

51. Perform density test at each site
Tex-207-F, Part IV
Select 3 test sites
Perform density test at each site

52. Repeat the process until there is no significant increase in density
Tex-207-F, Part IV
Repeat the process until there is
no significant increase in density

53. Tex-207-F, Part IV
Adjust the rolling pattern when conditions change – base, wind, temperatures, etc.