Concrete revibration is a deliberate and systematic vibration of concrete that has been vibrated sometime before. It can be carried out at any time provided the concrete remains plastic and the vibration instrument penetrates concrete under its weight. However, the best results are achieved when this is performed before the initial setting time of concrete.
The purpose of revibration is to improve concrete properties such as compressive strength, water tightness, increase density, prevent concrete defects like a honeycomb, and enhance the appearance of the concrete surfaces. It is used to construct critical structures, such as reactor shields, dry docks, tankers, etc.
What is Concrete Revibration?
Sometimes, concrete gets revibrated unintentionally. For instance, when two layers of concrete are consolidated, the vibrator is extended to the underneath concrete or multiple passes of the vibrating-beam screed.
However, the term "revibration" is used to refer to the intentional and systematic vibration of concrete that was consolidated sometime before using vibrators.
What is the Best Time for Concrete Revibration?
Concrete revibration can be performed as long as the vibrator can liquefy concrete under its weight, which may be several hours after placement. The effect of revibration is best when carried out just before the initial setting for concrete mixture with a slump value of 75 mm or more. It is also highly effective at top 0.5-1 m concrete placement where entrapped air is high.
On the other hand, it adversely affects well-consolidated and low slump concrete because it reduces the bond between bottom reinforcements and concrete. However, the revibration enhances the bond strength of top steel bars and high slump concrete.
Revibration for concrete containing retarder admixture is highly effective at cutting time and construction costs. It can also help pour a large quantity of concrete to construct massive concrete elements without forming cold joints. As a result, cracking and deflection can be minimized.
Why is Concrete Revibration Carried out in Concrete Constructions?
Advantages of Concrete Revibration
Revibration of concrete is found to improve many concrete characteristics. The most prominent advantages are:
- It improves concrete compressive strength. Revibration increases concrete bleeding, which results in high strength. The maximum compressive strength of concrete is achieved when revibration is delayed, increasing bleeding water.
- Revibration increases the water tightness of concrete.
- It enhances the appearance of the formed concrete surface by removing entrapped air and voids appearing on the concrete surface, see Figure-2.
- Increasing concrete density subsequently prevents extensive cracking, especially at areas such as at the top of doorways, arches, and major boxouts.
- Ensures adequate concrete consolidation and eliminates honeycomb.
- Closes concrete plastic shrinkage cracks and settlement cracks if revibration is done before concrete hardening.
- Revibration does not affect the durability of air-entrained concrete.
- Reduces the required work and hence workforce.
- Improves wear resistance and surface hardness of the floor, especially when combined with troweling action.
- It expels entrapped water and air under embedded steel bars and could improve the concrete-steel bond.
- Eliminates water pockets in the concrete.
- Revibration can increase the structure's life span, reduce total construction and maintenance costs, and increase asset value.
The use of revibration offers great benefits in certain buildings and concrete members as listed below:
- Walls, deep beams, and columns
- Dry docks
- Reactor shields
- Cargo Ships
Concrete revibration is a deliberate and systematic vibration of concrete that has been vibrated sometime before.
The purpose of revibration is to improve concrete properties such as compressive strength, water tightness, increase density, prevent concrete defects like honeycombs, and enhance concrete surface appearance.
The concrete revibration can be performed as long as the vibrator can liquefy concrete under its weight, which may be several hours after placement. The effect of revibration is best when carried out just before the initial setting for concrete mixture with a slump value of 75 mm or more.
1. Improves concrete compressive strength
2. Increases the density of concrete
3. Enhances floor surface hardness and wear resistance
4. Expels entrapped air and water pockets in the concrete
5. Minimizes shrinkage cracks and plastic cracks
6. Improves the concrete water tightness
7. Enhances the appearance of surface formed concrete
8. Ensures adequate concrete consolidation and eliminate honeycomb
9. Cuts both time and cost of building construction
10. Increases the value of building as it improves concrete qualities.
Revibration of concrete has been used in the construction of several structures such as:
1. Walls, deep beams, and columns
2. Dry docks
4. Reactor shields
6. Cargo Ships