A basic consideration in setting up a slip-form is the type of concrete finish
that is going to be required. The normal “slip-form finish” is a rubber-float
finish that is applied to the wet surface of the concrete as the slip progresses
or applied dry after the slip is complete, In the first method, a finisher’s
platform is suspended below the form and the finishing crew works with the
freshly exposed concrete to give it the texture required. A membrane cure is
sprayed on the surface after the finishing operation is complete, and it is
usually unnecessary to go over the surface again once the slip is complete. The
finisher’s platform can be seen below the form.The second method, that of
applying a “dry” finish, is to avoid touching the surface to be finished until
after the slipping operation is completed full height. When complete and the
form has been removed, the walls are float-finished from a swinging stage by
applying either a sand finish or a cement-plaster finish. If this method of
finish is to be used, (the finisher’s scaffold) is usually omitted except at
critical areas where it is, or may be necessary lo have access under the form.
Thus, the cost of fabricating and installing a finisher’s platform is saved and
can be applied to (he higher unit cost of applying the finish in this manner. If
a smooth finish is desired on the exterior of the building, a piaster skim coal
can be applied over the rubber-float finish. Sandblasting of slip-formed
concrete is not recommended. The possibilities of uniform texture are
practically nil. Furthermore, if sandblasting is attempted and found
unacceptable, corrective procedures are costly in both time and money.