Casting

Casting

The casting surface is very important in making precast concrete panels. In this section, we will cover two common types: earth and concrete. Regardless of which method you use, you must cast the slab in a location that will permit easy removal and handling.

Castings can be made directly on the ground with cement poured into forms. These earth surfaces are economical but only last for a couple of concrete pours. Concrete surfaces, since they can be reused repeatedly, are more practical.

hen building casting surfaces, keep the following points in mind:

• The subbase should be level and properly compacted.
• The slab should be at least 6 inches thick and made of 3,000 psi or higher
  reinforced concrete. Large aggregate, 2 ½ to 3 inches maximum, may be used in the casting slabs.
• If pipes or other utilities are to be extended up through the casting slab at a later date, they should be stopped below the surface and the openings temporarily closed. For wood, cork, or plastic plugs, fill almost to the surface with sand and top with a thin coat of mortar that is finished flush with the casting surface.
• It is important to remember that any imperfections in the surface of the casting slab will show up on the cast panels. When finishing the casting slab, you must ensure there is a flat, level, and smooth surface without humps, dips, cracks, or gouges. If possible, cure the casting surface keeping it covered with water. If you use a curing compound or surface hardener, make sure that it will not conflict with the later use of bond breaking agents.