Slip-form concrete is an alternative method of construction that involves pouring concrete into a top of a moving, shallow form. The concrete is poured vertically and the formwork is lifted at a speed that allows the concrete to harden without being removed from the bottom.
A hydraulic jacking system can be used to move the formwork vertically. Because no continual dismantling and re-assembly of formwork by crane is required during the construction period, silo slip form construction is a very safe technology.
Concrete pour rate, time to add reinforcing/opening blocks outs, and concrete setting time are all factors that determine the rate of lifting.
The slip-form construction system includes working levels or decks. The lower deck allows for easy access to newly exposed concrete, allowing surface finishing processes to be completed.
The work deck is used for installing the reinforcement steel and for facilitating the placement of concrete. This saves time and helps to reduce the amount of work required.
Some of the advantages of slip form construction are:
Pushing can produce high production speeds, but there is minimal flexibility for modifications once a long casting process has begun, necessitating meticulous planning.
At the bottom of the rising formwork, exposed concrete can be covered.
The formwork must be constantly removed and rebuilt in newer locations.
Concrete must be able to form and set easily by vibration, but it should also be strong enough to be deformed with force. Shear formwork is a great technique for the fast construction of unusual structures like cooling towers, chimneys, and silos.