A concrete vibrating tool is used to remove air bubbles in newly poured concrete as it is settling when poured into a foundation or mold. Air bubbles form when the cement mixer is rotating and as the concrete is being mixed air bubbles get trapped into the mixture. If these air bubbles are not removed it will weaken the structure and not allow it to bond to the rebar inside the slab.
When inserting a cement vibrator in concrete the settling concrete and will shake or vibrate out the the tiny air bubbles to create a stronger, long lasting pour. When a vibrating tool is used in concrete there are 3 parts to them: a motor, shaft and head. These three components come in various sizes, lengths and horsepower dependent on the size of the pour. These machines also comes in different configurations like cordless, electric, gas and backpack concrete vibrators. A pencil vibrator has heads that are thinner in diameter and a lot more portable for smaller projects. The newer cordless option adds to the portability aspect of these machines, making it lighter and much more flexible to use both indoor and outdoor.
Whether choosing a gas powered or electric, ensure that it is fully functional in the setting in which it is used. For indoor use the electric version is recommend as there is no concern for harmful fumes and pollutants. For outdoor use the gas powered option will work best for most use cases. Oztec and Northrock manufactures a complete line for outdoor and indoor use and they do remain one of the more popular brands for those looking for a cement vibrating machine.
Why do we vibrate?
1. Removes trapped air pockets from concrete that weaken the structure and not adhere to the rebar.
2. Not vibrating concrete can create "honeycombing" which creates voids when the mortar does not fill the spaces between the aggregate.
3. Creates a smoother finished look.
4. Improves surface appearance and minimizes patch work
5. Slows down rust causing elements by creating a dense compaction
6. Allows the cement to bond to rebar to create maximum strength
7. Eliminates rock pockets and lift lines
How to Use
- Allow the head to sink under its own weight vertically when inserting, forcing it may get it stuck in rebar
- Hold the unit in place for 5 – 15 seconds then pull it up slowly, if it’s a large or deep pour the head should be held in place every 2 ft for about 15 seconds to avoid trapping any air
- When pulling up from the concrete a slight up and down movement will close the hole formed by the head
- When reaching the top of the pour remove head and shaft quickly to prevent air getting trapped in top layer
- When removing head from concrete let it pass 3-6 inches from the previous layer to ensure a tight bond and preventing lift lines
- Pours should not be more then 2 – 3 feet high so the air has a chance to escape
Radius Of Action
Radius of action is the distance from the center of the vibrator to the outer edge, where complete consolidation takes place. Complete consolidation is necessary for low slump concrete with close meshed reinforcement bars, high strength concrete and architectural concrete. This action can be twice the listed values when slump is high or super plastisizers are used.
By using the methods above and the right vibrator the aggregate will consolidate and bond together to create a long-lasting slab. In the end a vibrator will remove trapped air bubbles, create a strong bond and create less shrinkage cracks, less bleeding and segregation of the pour. Once this process is completed they can proceed to cut concrete using a saw and the appropriate concrete cutting blade.
