Compaction of concrete is the process adopted for expelling the entrapped air from the concrete. In the process of mixing, transporting, and placing concrete air is likely to get entrapped in the concrete. The lower the workability, the higher is the amount of air entrapped.
The following methods are adopted for compacting the concrete:
a. Hand Compaction
b. Compaction by Vibration
i. Internal vibrator (Needle vibrator)
ii. Formwork vibrator (External vibrator)
iii. Table vibrator
iv. Platform vibrator
v. Surface vibrator (Screed vibrator)
vi. Vibratory Roller.
c. Compaction by Pressure and Jolting
d. Compaction by Spinning.
Read More————————————- Process of Manufacture of Concrete
Hand Compaction: Hand compaction of concrete is adopted in case of unimportant concrete work of small magnitude. Hand compaction consists of rodding, ramming, or tamping.
Compaction by Vibration: Where high strength is required, it is necessary that stiff concrete, with a low water/cement ratio, be used. To compact such concrete, mechanically operated vibratory equipment must be used. The vibrated concrete with a low water/cement ratio will have many advantages over the hand compacted concrete with a higher water/cement ratio.
- Internal Vibrator: Of all the vibrators, the internal vibrator is most commonly used. This is also called, “Needle Vibrator”, “Immersion Vibrator”, or “Poker Vibrator”.
- Formwork Vibrator (External Vibrator): Formwork vibrators are used for concreting columns, thin walls or in the casting of precast units. This method of vibrating concrete is particularly useful and adopted where reinforcement, lateral ties, and spacers interfere too much with the internal vibrator ties and spacers interfere too much with the internal vibrator.
- Table Vibrator: the vibrator is clamped to the table, or the table is mounted on springs that are vibrated transferring the vibration to the table. This is adopted mostly in the laboratories and in making small but precise prefabricated R.C.C. members.
- Platform Vibrator: Platform vibrator is nothing but a table vibrator, but it is larger in size. This is used in the manufacture of large prefabricated concrete elements such as electric poles, railway sleepers, and prefabricated roofing elements.
- Surface Vibrator: Surface vibrators are sometimes known as, “Screed Board Vibrators. Mostly, floor slabs and roof slabs are so thin that an internal vibrator or any other type of vibrator cannot be easily employed. In such cases, the surface vibrator can be effectively used.
Compaction by Pressure and Jolting: This is one of the effective methods of compacting very dry concrete. This method is often used for compacting hollow blocks, cavity blocks, and solid concrete blocks. Compaction by Spinning: Spinning is one of the recent methods of compaction of concrete. This method of compaction is adopted for the fabrication of concrete pipes.
Vibratory Roller: One of the recent developments of compacting very dry and lean concrete is the use of a Vibratory Roller. The heavy roller which vibrates while rolling is used for the compaction of dry lean concrete. Such roller-compacted concrete of grade M 10 has been successfully used as base course, 15 cm thick, for the Delhi-Mathura highway and Mumbai- Pune express highways.
Compaction of Concrete
Compaction is the process of removing trapped air from the newly poured concrete and holding aggregate particles together to increase the density of the concrete. It increases the final strength of the concrete considerably and improves the bond with the reinforcement. It also increases the resistance to abrasion and the overall durability of the concrete, decreases its permeability Minimize its contraction and jitter properties. Sufficient compression also ensures that the formwork is completely filled, i.e. there are no more foam pockets and the desired finish is achieved on the vertical surfaces. high settlements contain between 5 and 20% by volume of trapped air. Covered with mortar, they tend to bulge against each other and are prevented from collapsing or solidifying by internal friction.
Watch Video ———————— Types of Mortar