Methodology

The Slip Form method has been developed by Swedish Technologies for constructing chimneys, Silos(i.e. Blending, Cement, Chip, Coal Clinker, Fly Ash, Grain, Kaolin Lime, LNG, MALT, ORE, Sludge, Slurry, Salt, Sugar etc.), Silo Re-Lining(Interior& Exterior), caissons, Dams, Glass Batch Plant, High Rise Building, Feed & Flour Mills, Nuclear Shield Walls, Offshore Structures Shafts, Bridge Pier & cooling towers etc. Slip Form means a continuously moving form, moving at such a speed that the concrete when exposed has already achieved enough strength to support the vertical pressure from the concrete still in the form so as to withstand lateral pressure caused by wind, inclination of walls and so on.

The Slip Form is moved by hydraulic jacks spaced at equal intervals lifting the forms about 1" at a time every 5 to 10 minutes depending on the required sliding speed. An average sliding speed of 9" an hour is achieved in slip forming during construction. Vertical Slipforming is the fasted & most efficient method for casting reinforced concrete wall in many types of structures. It is a construction technique that utilizes a mechanized moving platform system enabling semi � continuous placement of concrete. Slipform differs from conventional concrete forming, in that concrete is placed or pump into the Slipform and the forms act as moving dies to shape the concrete.

The rate of movement of the form is regulated so that the forms leave the formed concrete only after it is strong enough to retain its shape while supporting its own weight. Form ties are not used. Pouring of the concrete, placement of reinforcement, installation of all blockouts and embedment, as well as finishing and inspecting the concrete surfaces, is performed gradually from work platforms permanently attached to the Slipform which rise together with the forms. Our staff members have a wealth of experience in the slip-forming of chimneys, tanks and silos. Amfah owns all the necessary specialized equipment needed to construct slip-form structures. This equipment can be packed into 20�/40� containers and shipped anywhere in the world.

Slip form

The lifting rate (or speed) of rig is determined by the slip-form technician and is based on speed of the placement of the concrete and reinforcement as well as the setting time of the concrete. Careful monitoring of the position of the slip form allows the hydraulic jacking system to control of the plumb of the finished concrete. The design of the slip form allows for any twisting to be countered. Openings with varying wall thicknesses and cross-sections can be accommodated and all contribute to an acceptable lifting rate. The slip-form rig typically comprises three levels of working:

1.Upper reinforcement deck

The reinforcement deck is the uppermost deck on the slip-form rig and facilitates the fixing of the reinforcement . Some slip-form rigs combine the reinforcement deck with the middle working deck.

Working deck

The working deck is the main deck of the slip-form rig. Typically this deck will support the hydraulic jacking system and provides the working platform from which to place and compact concrete. It is important that the concrete is placed in even layers around the formwork shutters. The control of the concrete quality, supply and setting rate is vitally important for slip form operations.

Lower rubbing up deck

The rubbing up deck is located under the working deck and provides access to the faces of the poured concrete as they emerge from the underside of the shutters. The concrete is made good from this deck to provide a smooth surface finish.