A rebar shaker is a vibratory device attached to steel bars which turns them into a vibratory instrument to consolidate the concrete.
It is designed to compact concrete in reinforced concrete elements that cannot be reached easily, such as congested reinforced concrete elements and reinforced concrete masonry walls.
The device is practical and easy to use. The rebar shaker eliminates the need for needle vibrators in shallow and heavily congested rebar members. It avoids insertion and pullout of the internal vibrator, which may splash concrete, make the construction site messy, and pose risk to workers.
In addition, the device consolidates concrete quicker than an internal vibrator and reduces labor cost since it needs less workforce to pour and compact concrete.
What is a Rebar Shaker?
A rebar shaker is designed to turn reinforcing bars into a vibrator. It is slipped over steel bars, allowed to vibrate and fluidify the concrete and consolidate within 5-7 seconds. So, it would not be required to use an internal vibrator.
The rebar shaker is suitable for circumstances where the concrete cannot be reached and consolidated easily, for instance, reinforced concrete block masonry and congested members.
Generally, concrete in reinforced concrete masonry walls moves to a plastic state quickly compared with other cases of concrete casting since concrete blocks absorb a portion of water in the concrete mixture.
Therefore, the compaction process should be done soon before concrete reaches the plastic state. This can be performed with the use of a rebar shaker. The device helps cut the time required to insert a needle vibrator to the bottom of the reinforced masonry wall.
Sometimes, table vibrators are attached to steel bars with suitable fittings to consolidate concrete in heavily congested concrete members. This concept has been suggested by ACI 309R-5. However, using external vibrators as reinforcement shakers should be avoided since the vibrator can get damaged.
Importance of Rebar Shakers
Rebar shaker tackles the problem of concrete consolidation in heavily congested and shallow members. However, in the case of heavily reinforced concrete members, steel bar spacing does not permit the insertion of proper internal vibrator head size into concrete. That is why a smaller but less effective vibrator head should be used.
Moreover, heavily congested bars act like walls that obstruct vibrations from the vibrator inside the wall to reach the formwork face. Similarly, if an external vibrator is used, the concrete at the formwork face is consolidated properly, and the steel cage's rebar wall prevents vibration from reaching the concrete inside. Attaching a rebar shaker to the top of steel bars would turn them into vibrators.
As a result, vibrations are transferred to the concrete through embedded steel bars. A rebar shaker leads to 360 consolidations from the center of the wall right up to the formwork face. It also eliminates the difficulty of inserting internal vibrators into concrete between steel bars in heavily congested reinforced concrete elements.
Applications
Rebar shakers are used to consolidate:
- Heavy congested reinforced concrete walls and columns
- Reinforced concrete unit block masonry wallsÂ
Advantages
- It is attached to the top of the steel bar easily without much effort.
- Need less workforce compared with a case of using an internal vibrator.
- Saves time required for filling and refilling concrete block cells, cleaning works, and lost time that may occur due to injury from slips and falls.
- It eliminates labor errors such as pulling the vibrator head out of the concrete quickly, resulting in poor concrete consolidation and a weak bond between concrete and steel bars.
- It adequately consolidates concrete in heavily congested elements and reinforced concrete block masonry, resulting in a good concrete-steel bar bond. Â
Disadvantages
Rebar shakers may loosen and disorient lateral ties because of excessive vibrations or improper fastening of the transfer reinforcement.
FAQs
A rebar shaker is a vibratory device attached to steel bars which turns them into a vibratory instrument to consolidate the concrete. It is designed to compact concrete in reinforced concrete elements that cannot be reached easily, such as congested reinforced concrete elements and reinforced concrete masonry walls.
Yes, rebar shakers can consolidate concrete satisfactorily and yield the same result as an internal vibrator. As a result, it can replace internal vibrators.
A rebar shaker should consolidate heavily reinforced concrete members and shallow structural elements.
1. It can be slipped over a steel bar easily.
2. Saves time required for filling and refilling concrete block cells, cleaning works, and lost time that may occur due to injury from slips and falls.
3. It eliminates labor errors such as pulling the vibrator head out of the concrete quickly,
4. It adequately consolidates concrete in heavily congested elements and reinforced concrete block masonry, resulting in a good concrete-steel bar bond.Â
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