PRECAST and TILT-UP CONCRETE

Concrete cast in the position it is to occupy in the finished structure is called cast-inplace concrete. Concrete cast and cured elsewhere is called precast concrete. Tilt-up concrete is a special type of precast concrete in which the units are tilted up and placed using cranes or other types of lifting devices.

Wall construction is frequently done with precast wall panels originally cast horizontally, sometimes one above the other, as slabs. This method has many advantages over the conventional method of casting in place in vertical wall forms. Since a slab form requires only edge forms and a single surface form, the amount of formwork and form materials required is greatly reduced. The labor involved in slab form concrete casting is much less than that involved in filling a high wall form. One side of a precast unit cast as a slab may be finished by hand to any desired quality of finishing.

The placement of reinforcing steel is much easier in slab forms, and it is easier to attain thorough filling and vibrating. Precasting of wall panels as slabs may be expedited by mass production methods not available when casting in place.

Relatively light panels for concrete walls are precast as slabs, as shown in Figure 83.

The panels are set in place by cranes, using spreader bars as shown in Figure 84.