What Is Vacuum Concrete?
Vacuum concrete is the water removed by vacuum pressure after the concrete has been placed in the structural member. Vacuum concrete has higher strength and durability than ordinary concrete.
In the concrete mixing process, more water is added to make the concrete more efficient. Therefore excess water is not required for a complete hydration process. Excess water is removed from the concrete by vacuum pump by vacuum concrete technique. So that the concrete can be strengthened before it hardens.
The excess water-cement ratio for concrete is detrimental to strength. The water-cement ratio in Concrete must be as required to obtain high strength.
Vacuum concrete is a technique of removing excess water from efficient concrete using a vacuum pump.
The Necessity of Vacuum Concrete
The water-cement ratio of 0.38 is required for the chemical reaction of cement with water; the water-cement ratio taken more than this amount mainly affects the efficiency required for the concrete, so the concrete can be easily placed in the formwork without honeycombing.
As the efficiency of the concrete is satisfied, this excess water will evaporate out, leaving capillary holes in the concrete, which reduces the high permeability and strength in concrete. Thus the efficiency and high strength of concrete are contradictory.
The vacuum concrete method is an effective technique used to meet the requirements of efficiency and high strength. This requirement of concrete can be made possible both at the same time by using this technique.
Using this technique, the excess water remaining after placement and compaction of the concrete is removed using a vacuum pump. This technology usually works effectively in industrial units, parking lots and deck slabs of bridges etc. This technique can only reduce the surface area of concrete to a depth of 100 to 150 mm.
History of Vacuum Concreting
The technique of vacuum concreting was first used by Sweden’s Trimix AB to increase strength by removing water through a vacuum pump in concrete.
The technique became popular in the United States and has since gradually gained popularity throughout Europe.
This technique is commonly used in concrete works in Sweden.
In India, the details of this technology were introduced in 1987 by Aquarius Technologies.
Properties of Vacuum Concrete
- The strength of concrete can be increased by about 25% by using the vacuum concrete technique.
- The vacuum increases the density of concrete by using concrete techniques.
- The permeability of concrete can be reduced by using the vacuum concrete technique.
- The durability of concrete can be increased by using the vacuum concrete technique.
- The abrasion resistance of concrete can be increased by using the vacuum concrete technique.
- The impact resistance of concrete can be increased by 10% by using the vacuum concrete technique.
Application of Vacuum Concrete
- The vacuum concrete technique is mainly used in hydropower plants.
- Suitable for cooling towers as vacuum concrete application.
- The vacuum concrete technique can be used for industrial and cold storage floors.
- The vacuum concrete technique is commonly used for ports and harbours.
Advantages of Vacuum Concrete
Some of the advantages of using the vacuum concrete technique are as follows,
- The use of the vacuum Concrete technique increases the strength of concrete and, at the same time, reduces the permeability of concrete.
- The use of vacuum concrete techniques improves the quality of durability and density. It also reduces voids in concrete.
- The curing period can be reduced by using the technique of vacuum concrete. If the concrete has a curing period of 1 week, it can be reduced to 3 days.
- The vacuum concrete technique can be used to remove formwork before it is time to remove formwork for concrete slabs because concrete is able to gain strength quickly. So this vacuum concrete technique can be used in repetitive tasks.
- High strength and high efficiency of concrete can be achieved by using the vacuum concrete technique.
- The use of the vacuum concrete technique increases the final strength of concrete by 25%. (Which increases the resistance of concrete to shrinkage and tensile strength.
- The use of the vacuum concrete technique increases the bonding strength by about 20%, which forms a strong bond with the elements of concrete.
- With the use of vacuum concrete technique, the work of the structure of the building can be achieved faster earlier.
- The use of vacuum concrete provides easier and more efficient compaction of concrete.
- The vacuum concrete method creates a pet-free surface on the surface of the concrete.
- The top surface of the concrete with the vacuum concrete method has a very high resistance to abrasion. So this technique can be used especially for floor in road and industrial.
Disadvantage of Vacuum Concrete
- This method uses power for the dewatering pumps, which increases the total cost.
- The initial cost of equipment for the vacuum concrete technique is high.
- Various special equipment is required for vacuum concrete.
- The process for vacuum concrete requires skilled labour.
- The vacuum concrete technique used is suitable for concrete with a water-cement ratio greater than 0.4. This technique is not used for a lower water-cement ratio than that.
Equipment Required for Vacuum Concrete Method
Vacuum concrete is obtained using the following tools,
- Vacuum Pump
- Filtering Pad
- Suction Mat
- Power Trowel
- Power Float
- Double Beam Screed Vibrator.
The vacuum concrete technique usually involves preparing formwork for concrete using ms channels, which allows the stopper and screed vibrator to operate safely over it.
2. Vacuum Pump
This method uses an electric motor of 5-10 horsepower for vacuum.
3. Filtering Pad
Fixing is done with a rubber seal around the filtering pad. The minimum dimension of the filtering pad is kept at 90cm x 60cm. Includes backing piece and rubber seal as filtering pad.
A minimum size 90 * 60 cm mat is placed on the surface of the concrete. However, the use of small mats to create a vacuum should be avoided.
4. Suction Mat
The mats are fixed on fine filter pads to prevent cement slurry with water.
It is on a large single PVC sheet concrete. Nylon fabric acts as a filter. The top surface of the mat has a hose with a junction box.
5. Power Trowel
The water suction process forms capillaries in concrete, which is made by extracting water from concrete, which is detrimental to the strength of the concrete. Therefore power trowel is used to improve the condition of such concrete, which fills the cracks of concrete by vibration.
6. Power Float
It is used for finishing the surface of the concrete, which increases the strength of concrete.
7. Double Beam Screed Vibrator
It is a 12.5 kg electric powered vibrator for the compaction of concrete.
Process of Vacuum Concrete
- The efficiency of ordinary concrete depends on the amount of water in the concrete, which is the main factor to speed up the construction. Therefore it is advisable to use vacuum concrete techniques to compromise the efficiency and strength of concrete.
- In the vacuum concrete process, the conditions for the vacuum are created on the top surface of the concrete.
- In vacuum concrete processing, a certain amount of water is removed from the concrete to a certain depth.
- Porous mats are placed on the surface of the concrete to create a vacuum, which is connected to the scheme of pumping water out through a vacuum pump.
- Which reduces the amount of water from the concrete through the vacuum pump. And the concrete gains strength.
- The concrete surface obtained by vacuum concrete has high strength capacity, low permeability and high durability, which is suitable for the use of concrete.