1. Consolidation
Consolidation does not mean vibration. Vibration can be a method to consolidate

2. Consolidation What is Consolidation as related to concrete?
The even distribution of all ingredients in the concrete mix but……. does not necessarily reduce the size or volume.
When good consolidation is achieved it allows for better COMPACTION which is the process of reducing the size or volume. In this case it is very dense concrete that we are looking for.
It is the packing of the concrete by the
removal of air.
Consolidation does not mean vibration. Vibration can be a method to consolidate

3. How does Vibration Assist in Consolidation?
Pressure waves from the vibration separate the aggregate particles thereby reducing friction.
It also drives out the air which reduces the volume

4. Why Vibrate?
Freshly placed concrete can contain as much as 20% entrapped air
Proper vibration increases density by driving out entrapped air (vs.. entrained)
Results in:
Optimum strength
Durability
Quality appearance
Water tightness
1) Philosophical (depends on the type of mixer – high speed vs.. ribbon)
2) Explain entrained vs. entrapped here (We want entrained to stay, entrapped out) Big drops and transporting by Tuckers
3) Ultimate goal

5. Proper Vibration Should
Eliminate voids and honeycombs
Release entrapped air
Fully encase reinforcement, embedded items, and block outs with fresh concrete
Vibration will accomplish these goals IF proper amplitude and frequency are applied.

6. THE THEORY MASS FREQUENCY AMPLITUDE ACCELERATION FORCE RESONANCE
Mass…the total off balance in the vibrator that creates the vibration
Amplitude….the distance that the vibrator will influence the concrete
Frequency….how fast the vibrator spins. RPM or VPM
Force….the pounds of impact that the vibrator puts into the load
Resonance…when all of the materials vibrate together

7. MASS=WEIGHTS
COUGAR D-SERIES
ISKCO HKM75LFS
OLI 5100
OLI 3550

8. It is how many RPM or VPM that the vibrator shaft rotates.
Frequency
It is how many RPM or VPM that the vibrator shaft rotates.
, ,000

9. Amplitude It is affected by frequency….
The higher the frequency the lower the amplitude. Which means the lower the frequency the higher the amplitude.

10. Determine the FREQUENCY Which affects the AMPLITUDE
Take the MASS
Determine the FREQUENCY
Which affects the AMPLITUDE
Which is also affected by the ACCELERATION (CENTRIPETAL)
And you come up with the FORCE
FORCE IS WHAT IS ACTUALLY DOING THE WORK OF CONSOLIDATION
But you have another factor to account for when describing an object in simple harmonic motion: its acceleration at any particular point. When an object is going around in a circle, the acceleration is the centripetal acceleration

11. Amplitude & Frequency of Vibration
Effects heavier mass
Moves the aggregate
Determines the radius of action
Frequency
Effects lighter mass
Moves the paste
Governs liquefaction
We mount the vibrator so it doesn’t move, we are trying to get the skin on the form to move.

12. Amplitude and Frequency Example
HOW MUCH FORCE CAN YOU APPLY WHEN YOU SWING THE HAMMER?

13. In order to match the vibrator you would have to hit the board
Hit the board as hard as you can with one blow
Now hit the board 10 times as fast as you can
In order to match the vibrator you would have to hit the board
60 TIMES PER SECOND!!

14. What changed in the way the hammer was used?
AMPLITUDE
FREQUENCY
AND FORCE

15. Methods of Vibration INTERNAL – Stingers (flexible shaft or immersion)
EXTERNAL – Mounted on forms both jacket and core. Vibrating tables
Internal is not putting the vibrator in the core

16. Internal Vibration
Stingers - commonly used for smaller wet cast items and flat work

17. Stinger Vibrators Rule of Thumb
The Head Diameter should be approximately
Wall Thickness 4
It is important to assess your common cage configurations
Hydraulic most common, but also most expensive
Stick diameter – more rule of thumb…..what will fit, what type of clearance do you have

19. Stinger vibrators are usually
Vibration Frequency
Stinger vibrators are usually
VERY HIGH
Vibrations per minute
10,000-17,000 VPM
(however they typically loose 20% when inserted in the concrete unless the motor is in the head of the stinger)
Be careful when using an air entrainment additive as it may significantly reduce the air if over vibrated
Important to have regulators

20. Stinger Vibration Procedure
Drop vertically under own weight (~1sec/ft.)
Let gravity do its job
Withdraw slightly slower than inserted (~3sec/ft)
Flowability is the key
Place stick into each area only once
overlapping the vibrating radius.
Flowability note – if it leaves a hole when removed, it was too fast

21. Overlapping Field of Action

22. No vibration

23. Stinger Vibration Procedure
When layering concrete, place stick ~4” into previous layer
Vibrate until surface is shiny and level, and no more large breaking bubbles
Avoid touching formwork
Duct tape on housing for level indicators
Avoid touching form work – critical with architectural, more of a maintenance issue with our industry

24. Effects of not overlapping fields of action
Reduced strength and durability because of:
voids
honeycombing
entrapped air
Reinforcement
not covered
If vibration is not overlapped, may find voids as shown above – but this also depends on the flowability of the mix. There may not be a need to vibrate each are if the mix is flowable (trials)

25. External Vibration
Hangs on forms
Vibrating table

26. Electric 3600 RPM Electric 7200 RPM Pneumatic 6600 RPM

27. Electric Pneumatic Hydraulic
Form Vibration
Electric Pneumatic Hydraulic
Faster filling than stinger vibration but forms must be stronger
Faster than a stinger

28. What size goes on which form?
THE CONCEPT IS QUITE SIMPLE….
ENOUGH VIBRATION TO CONSOLIDATE THE CONCRETE WITHOUT DESTROYING THE FORM!!!!
Rule of thumb: Use vibrator with an impact force that is 1.5 to 2 times larger than the weight of the concrete plus the weight of the form

30. H I G F R E Q U N C Y O L PNEUMAT I C
CONVEYOR PRODUCTS / WAM CORPORATION
CR-5500
20 PSI
40 PSI
60PSI
80 PSI
VPM
LBS
CFM
5,800
1350 34
8,500
2750 46
12,300
6000 54
16,000
11,000 60
MARTIN ENGINEERING COMPANY
CCR-5500
6,600
1560 32
10,000
3582 42
12,500
5596 55
14,000
7,020 58
PNEUMAT I C

31. Form Vibration Mounting brackets should be welded onto the stiffener.
Don’t fasten vibrator directly onto the skin.

34. Torque
Vibrator bolts must be properly torqued to manufacturers recommendations!!!

35. DO YOU TORQUE THE MOUNTING BOLTS?

36. Check vibrator weight settings

37. Check with supplier for orientation and location of vibrators on forms
Check with supplier for orientation and location of vibrators on forms. They can also recommend the number of vibrators to use.

38. WHICH WAY DO THE VIBRATORS ROTATE?X

39. Form Vibration Sizing The harsher the mix = more power
The stiffer the form = more power
More flowability = less power
*Take away: it all varies by plant, forms size and raw materials. Work with your suppliers on sizing
Work with supplier

40. This type of vibrator needs air to cool itself
Use of mud flap

41. Form Vibration Procedure
Ideally start when concrete is 6” above vibrator (Not always the case)
Stop when concrete is level, glossy surface, and no more large breaking bubbles
Air bubbles go to vibrating surface

42. Table Vibration Rotary or linear vibrators
Shaker tables - eccentric shaft
With rotary vibrators, vibration must be unidirectional to avoid “walking” the concrete
Sizing
Use vibrator with an impact force that is 1.5 to 2 times larger than the weight of the concrete plus the weight of the form
“walking” is when there is only 1 vibrator going in 1 direction walking the concrete down the form. Suggest at least 2 rotating in opposite directions.

43. Unidirectional Vibration
This vibration is all vertical

44. Clamping is critical!!!
Notice rubber cushions to dampen the vibration to be put into the concrete, not the floor

45. Box form for Betodan Equipment (Notice the struts and point out no vibrator mounts are available, table only system)

46. Effects of Under-Vibration
Can have serious detrimental effects
Inadequate Concrete Strength & Durability
Excessive entrapped air
Unbonded Reinforcement
Honeycombing
Poor Appearance
Sand streaks
Bug holes

49. Effects of Dry Concrete
This can have serious detrimental effects
You can vibrate all you want but if the concrete can’t flow it will be very difficult to make it compact or consolidate.
This adds critical minutes to vibrating time that adversely affects production time and often results in a rejected piece of product.

50. Test Your Concrete !!!!
The Dry Cast Slump Test will give you a benchmark that can be used to determine the correct range of moisture that will make the fill time much more consistent

51. Understand what fill rate means to the product!!
The amount of concrete put in per pass is critical to consolidation and that rate MUST
be controlled if you are to achieve good, watertight concrete.

52. Effects of Over-Vibration
Segregation
Form deflection and Damage
Sand streaks
Water bleed areas
(Usually near a vibrator)

53. Form Deflection Prevention

54. Important Note
Dry-cast vibration is very different from wet-cast vibration
Dry-cast forms are designed for specific vibration system
Don’t mix & match dry and wet-cast systems!
Looking for different results

55. Keep this in mind…….
It is the form vibrating that consolidates the concrete. If the form remains rigid, the concrete has a very difficult time moving and it will require a larger vibrator to get the required results.

56. The concept of consolidation is to get the concrete to compact by removing trapped air and forcing the aggregate, sand, and cement to spread uniformly throughout the form while forming a water and air tight matrix that will meet the designed compressive strength requirements.

57. QUESTIONS?