When the internal vibrator is inserted into concrete, it generates vibrations, which improve the consolidation process and facilitate the removal of air pockets and voids from the concrete. A typical internal stick vibrator is comprised of a motor, a whip and a head. The vibrator can be electric or gas powered.
The motor drives the whip and the head to rotate at a high speed. The vibrating motion causes the aggregates in the concrete to liquefy and segregate under the force of the vibration, resulting in the coarse aggregate sinking and the mortar flotting to the top. The longer the duration of vibrating, the more dense the concrete will become.
This process requires careful planning and precise execution. The operator needs to know what kind of mix design, reinforcement configuration and vibrator type he or she is using so that the equipment can be used to its fullest potential.
It is important to know how long to vibrate the concrete to release entrapped air bubbles without segregating the heavier coarse aggregate particles from the paste matrix. The length of time to be used varies according to the vibrator type, size and settings.
The first step is to insert the internal vibrator head into the poured wet concrete. The operator should push the head into the concrete with a forward direction and pull it in a reverse direction in the same direction, thus maximizing contact between the outer wall 32 of the vibrator head and the poured wet concrete.
To improve the effectiveness of the insertion operation, the front half portion of the elongated body 2 of the improved concrete vibrator head 30 is provided with a straight line or stepped taper or slope. This angle of taper 13 maximizes contact between the outer wall 32 of the vibrator cylinder and the poured wet concrete in order to transmit more vibrations into the wet concrete and facilitate the consolidation process.
As a result, the improved concrete vibrator head will tend to penetrate into the poured wet concrete along a greater axial length than with conventional vibrator heads. This will improve the traction of the injected water in the concrete and further facilitate the re-consolidation process.
This is especially true when the vibrator is inserted into the concrete under its own weight. The insertion should be done at a rate of about one foot per second, and the vibrator should be withdrawn at a slower rate of about one foot every three seconds.
When the vibration process is completed, the accumulated water in the concrete will be released as air bubbles begin to rise. These escaping bubbles will eventually slow down and appear as a sheen on the surface of the concrete.
The concrete will also be consolidated as the vibrating head moves around the circumferential area. The radius of vibration that the head reaches is called the zone of influence, and the operator should always insert the vibrator at this same spot so that the zones of influence overlap each time they are inserted.