The ultimate approach in incorporating a slip-form into building construction is to sup-form all vertical concrete. This makes the slip-form the primary operation controlling the other phases of construction. All vertical concrete structural elements are extruded by the slip-form.
First, before discussing details of a slip form operation, we should evaluate the advantages and disadvantages of the basic system in order to determine whether a job should be slip formed. It is generally recognized that slip forming is a faster method of construction than conventional forming; so it follows that if the construction cycle is geared to the slip form as the controlling item, an earlier completion date can be obtained. From the owner’s standpoint, an earlier completion date means an earlier return on invested capital. From the contractor’s standpoint, an earlier completion date means lower overhead costs and more jobs that can be completed within the organization in a given period of lime.
Under ideal conditions a slip form will provide substantially lower construction costs, which directly result in lower completed-building costs. This may make possible the building of projects that otherwise could never have been built because of limited financing. Slip forming is one system of automation which can be more broadly included in building-design systems. The efficiency of its use depends on the building design and its adaptability lo construction details that are necessary to slip-forming and which are discussed later in this chapter. In order lo achieve this automation, work of all the various trades must be organized and coordinated so that they mesh with each other with a minimum of conflict. The materials deliveries, such as concrete and reinforcing steel, should be made on schedule in order to develop a maximum rate of slip. Specialized help is required for the duration of the slip form work, much more so than in conventional construction. It is imperative that some person thoroughly familiar with the overall operation be on the form at all times If care is taken in the planning stage and carried through the complete operation, many of the normal pitfalls can be avoided and an efficient operation can be achieved.
Not all jobs are suitable for slip forming, and each should be evaluated to determine whether a slip-form is feasible. This should be done in consultation with (architect and structural engineer, for sometimes limitations of structural or architectural design preclude the possibility of making the changes necessary to set up a slip-form operation, If the design is in an early stage, it is sometimes possible to design around a slip-form or. in other words, make the basic design for one that can he slip formed. Many owners have resorted to this method of architect-engineer-contractor coordination and cooperation in order to obtain the most for their money.