Consolidation www concretepipe org 2 What is Consolidation

Consolidation www. concrete-pipe. org

2 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. www. concrete-pipe. org

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 www. concrete-pipe. org

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

5 Proper Vibration Should Eliminate voids and honeycombs Release entrapped air Fully encase reinforcement, embedded items, and block outs with fresh concrete

6 THEORY MASS FREQUENCY AMPLITUDE ACCELERATION FORCE RESONANCE www. concrete-pipe. org

7 MASS=WEIGHTS COUGAR D-SERIES OLI 5100 ISKCO HKM 75 LFS OLI 3550

8 Frequency It is how many RPM or VPM that the vibrator shaft rotates. 3450 3600 6000 7200 10, 000 17, 000 www. concrete-pipe. org

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. www. concrete-pipe. org

10 Take the MASS Determine the FREQUENCY Which affects the AMPLITUDE Which is also affected by the ACCELERATION And you come up with the FORCE (CENTRIPETAL) FORCE IS WHAT IS ACTUALLY DOING THE WORK OF CONSOLIDATION

Amplitude & Frequency of Vibration Amplitude Frequency Effects heavier mass Effects lighter mass Moves the aggregate Moves the paste Determines the radius of action Governs liquefaction 11

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

13 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 www. concrete-pipe. org

15 Methods of Vibration INTERNAL – Stingers (flexible shaft or immersion) EXTERNAL – Mounted on forms both jacket and core. Vibrating tables

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

18 www. concrete-pipe. org

19 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

20 Stinger Vibration Procedure Drop vertically under own weight (~1 sec/ft. ) Let gravity do its job Withdraw slightly slower than inserted (~3 sec/ft) Flowability is the key Place stick into each area only once overlapping the vibrating radius.

21 Overlapping Field of Action

No vibration www. concrete-pipe. org

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

Effects of not overlapping fields of action Reduced strength and durability because of: • voids • honeycombing • entrapped air • Reinforcement not covered 24

25 External Vibration Hangs on forms Vibrating table

26 Electric 3600 RPM Electric 7200 RPM Pneumatic 6600 RPM www. concrete-pipe. org

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

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 www. concrete-pipe. org

29 www. concrete-pipe. org

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

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

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www. concrete-pipe. org

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

35 DO YOU TORQUE THE MOUNTING BOLTS?

Check vibrator weight settings 36

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

WHICH WAY DO THE VIBRATORS ROTATE? X 38

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

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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

43 Unidirectional Vibration

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

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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. www. concrete-pipe. org

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!

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. www. concrete-pipe. org

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. www. concrete-pipe. org

57 QUESTIONS?