1. How Compaction Affects Smoothness

2. How Compaction Affects Smoothness
Transverse Joints
Patterns
Stops

3. Joint Compaction -- Team Effort
Start with good paving and minimal hand work
Mat depth must allow for rate of compaction
Rule of thumb: ¼” of compaction for each 1” mat depth

4. Poor Starting Point
Rounded face at the joint
Plunge cut too deep

5. Good Starting Point Cut straight starting joint Butt joint flat
Tack butt joint
Clean area where screed will rest

6. What We’re Trying to Avoid
Profile Summary -- MN Hwy 65, 9/14/06, start of paving 1.1 miles

7. Transverse Joint Compaction
Whenever possible roll from the side in static mode
Pinches joint
Rolling straight --drum tends to bump over joint

8. Transverse Joint Compaction#1
12”
Hot
Cold
Joint

9. Transverse Joint Compaction#2 #1
30”
Hot
Cold
Joint

10. Transverse Joint Compaction#3 #2 #1
30”
60”
Hot
Cold
Joint

11. Transverse Joint Compaction
Hot
Cold #1
Paver
Joint

12. Transverse Joint Compaction#2
Hot
Cold #1
Paver
Joint

13. Transverse Joint Compaction#3 #2
Hot
Cold #1
Paver
Joint

14. Transverse Joint Compaction
Straight edge tells the story
Too high -- more rolling may help
Too low -- hand work needed to fill in

15. Breakdown Roller Pattern
5-pass pattern
Forward adjacent to centerline
Back along unconfined edge
Forward in center of mat
Back adjacent to centerline
Medium amplitude
250 fpm

16. Breakdown Pattern Marks
Occasionally left narrow step in the center of the mat
Crossover marks resulted from unusual rolling pattern

17. Intermediate & Finish Roller
Operating minutes behind breakdown roller
Mat temp o F
Two vibe passes, low amplitude at 237 fpm
Three passes static at 264 fpm
Barely reaching 92% density spec
Compaction process affecting smoothness

18. Mapping Options [ Optional systems aid operator consistency
GPS shows operator machine position and counts passes
Screen turns colors as passes are completed
Removes guesswork
Allows corrective action
There are options available for asphalt compactors to help operators maintain uniform rolling patterns. Screens in the operator’s compartment can be programmed to show the operator where the roller is located on the mat and how much of the pattern has been completed. Global positioning systems provide very accurate maps of rolling patterns. The control can be programmed with the required number of passes. Then, the screen will display different colors as the passes are completed. The operator no longer has to guess at the end of a pass for reversing. And, there is less chance that the operator will miss any of the areas in the pattern because the screen provides immediate feedback for corrective action.

19. Temperature options ]
Optional temperature sensors help confirm temperature uniformity
Located ahead of front and rear drums
Activated by direction of operation
Operator checks display to see if machine is in proper zone
Infrared temperature sensors are another option for some asphalt compactors. On Caterpillar models, sensors are installed on front and rear drum yokes. The front sensor is activated when the machine is going forward. The rear sensor is activated when the machine is operating in reverse. The sensors are continually cleaned by compressed air that keeps dust, fumes and moisture away from the sensor lenses. The temperature systems are accurate and provide constant, visual reference at the operator’s station display for the compactor operator. Not only does the operator know where the machine is located in relation to the defined rolling pattern, the operator knows where the machine is located relative to the desired temperature zone.

20. How Pattern Marks Affect Smoothness
Paint stripe #01 marked location of breakdown roller crossover mark
Mark resulted in higher than normal deviation score

21. Driveways, Turnouts Breakdown roller maintains straight path
Aggressive steering will mark the fresh driving lane mat
Intermediate roller – OK
Finish roller -best

22. Bends, Tight Radius Compaction
Street project paving 12- feet wide
66” drum width breakdown roller
Operator followed radius in continuous pass

23. Bends, Tight Radius Compaction
Outside edge of drum is shoving hot mix
Mat distorted and cracked

24. Bends, Tight Radius Compaction
Roller operator trained to roll straight into radius
Pattern takes more passes but leaves smooth tight mat

25. Bends, Tight Radium Compaction
Bends or Junctions

26. Roller Reverse Marks
84-inch drum on 12-foot mat yields small reversing angle
Deep mark left by outside drum edge during turn
Reversing close to paver on hot, tender mix accentuates mark left by drum edge
Marks may not clean up during successive passes

27. Roller Reverse on Adjacent Cold Mat
Paving westbound lane breakdown roller could reverse on cold eastbound mat
Less marking on hot mat
Profilograph showed less deviation on westbound lane due to fewer roller marks

28. Roller Reverse on Shoulder
12-foot driving lane and 6- foot shoulder with 18” slough
All compactors stop / reverse on shoulder
No stop marks in driving lanes
Project earned 100% of available ride bonus

29. What We’re Trying to Avoid
Breakdown roller pattern
Stops too close together
Hard to erase completely with finish rolling

30. Compaction Issues - Rolling off Edge
Never roll off unconfined edge
Collapsed edge will create a joint failure
Never roll off the edge of an unconfined mat. The edge will collapse under the weight of the drum and cause a problem for the paver crew as the adjacent lane is being paved. There will be uneven compaction and joint failures at points like this.
It’s very easy to see that an improper operating technique was used here.

31. Compactor Stopped during Paver Stop
Breakdown roller caught up to paver during stop
Parked on mat 100’ behind paver
Drums dented mat
Six minute roller stop

32. Thermal Effect of Roller Stop
Drums act as heat sink on mat
Two cold dents created
P2 and P3 150o F
Dents will not be removed by next roller passes

33. Effect of Roller Stop on Smoothness
Dents left by drums are easily identified -- two sets of bumps and dips about 8 feet apart
0.18 added to score in 8 feet of paving
Proves that finish roller could not clean up these marks

34. Stopping for Water
Always try to find a place to park off the driving lane
Shoulders, turn-outs, driveways

35. Breakdown Roller Stopped for Water
Compactor stopped 10 minutes on mat for water
Mat cooled to 150 o F under the drums
Drums created depression and bump
Sometimes this is unavoidable -- right?

36. Thermal Image of Roller Stop
Drums act as heat sink
Rapid loss of heat in mat under drums
Intermediate and finish passes will not remove bumps

37. Intersection Tie-ins
Note: small roller working on tie-in to intersection

38. Pick-up on Pneumatic Tires
Operate roller at high speed before getting on mat
Use approved release agent on tires
Most critical when rolling “sticky” mixes with polymer modified oil

39. Pneumatic Tire Marks Finish roller must be able clean up tire marks
Especially problematic in cold weather
Be sure tire skirts are in place

40. Pneumatic Tire Marks
What would do when tire pick up is this severe?

41. How Compaction Affects Smoothness
Plan your work to match the application
Ask questions if you’re not sure
Stop rolling when you see a problem
Consult the supervisor or QC person

42. © 2017 Caterpillar All Rights Reserved
QESQ1942 (1/17)
© 2017 Caterpillar All Rights Reserved
Materials and specifications are subject to change without notice.
Featured machines in photography may include additional equipment for special applications.
CAT, CATERPILLAR, BUILT FOR IT, their respective logos, “Caterpillar Yellow,” and the POWER EDGE trade dress,
as well as corporate and product identity used herein, are trademarks of Caterpillar and may not be used without permission.

43. [ INCONSISTENT DENSITY ]
UNIT 7: COMPACTION ISSUES
[ INCONSISTENT DENSITY ]
Quality Control verifies:
- density behind each phase
- communicates results to operators
- communicates changes to operators
Quality control personnel are responsible for verifying density on the project. They check the density of the asphalt layer after every phase of compaction. Then, they communicate the results to the compactor operators and discuss any changes in the process that are required to improve quality. If density is inconsistent, quality control is responsible for finding reasons for the inconsistency.

44. [ INCONSISTENT DENSITY ]
UNIT 7: COMPACTION ISSUES
[ INCONSISTENT DENSITY ]
Maintain pattern and working speed
Paving crew and initial phase compactor operator communicate
All paving speed changes are approved and told to compactor operator
Some operators have difficulty repeating the same pattern as they follow the paver. They do not always hit each portion of the mat the same number of times. Therefore, density checks made by the quality control technician will vary. When this happens, the quality control technician or supervisor must work with the compactor operator to define the pattern and make sure that the pattern is being repeated.
Verify that the paving speed has not been changed. Very often changes in paving speed are not communicated to the compaction team and the quality control team. A rolling pattern that has been working well is suddenly causing the compactor to fall behind the paver and to be working in a lower temperature zone, for example. The compactor falls behind because the paving speed has been increased. And, the operator tries to alter his or her rolling pattern to stay close to the paver. Never change paving speed without doing two things. First, communicate the speed change to the compaction team. Second, verify that the initial phase compactor can keep up if the speed is being increased.