How Are Precast Concrete Piers Built?

Preparing The Form

Before the concrete can be poured in the mold, or form, the inside surfaces must be thoroughly cleaned with a high-pressurize water gun. After removing dirt and concrete residue, the surface is coated with special grease or other lubricant to keep the final product from sticking. Piers generally have a rectangular block shape with beveled edges and an opening on the top designed to receive the building's stud, beam or pipe. For I-beams and square posts, the mold will have a tall, rectangular block in the center that creates a preformed opening. For pipes, the mold won't have a block. Instead, a hole will be bored into the top of the finished pier.

Precast concrete manufactures use a mixture of Portland cement, sand, aggregates (i.e., gravel pebbles), water and special chemicals that speed up the curing process. These ingredients are fed into a machine which mixes them in pre-set ratios.

Dozens of pier forms are arranged into tight rows inside the factory, separated by one-inch thick walls that extend about five inches above the surface. The mixing machine then pours the cement into a filling machine, which diverts the liquid cement into eight different shoots. The filling machine moves along the rows of forms as its shoots evenly fill the forms eight at a time.

Once all of the forms are complete, they dry for about 30 minutes before the workers insert a pair of hooks into each one. The forms continue to dry for several hours before being moved outside to dry outdoors. This combination of sunlight and open air allow the curing process to occur, hardening the concrete.

After the curing process is complete, hydraulic cranes lift each pier out of its mold using the hooks previously inserted. The piers are then inspected for cracks, buffed for smoothness and drilled to create pipe openings (if need be). Finally, the precast concrete piers are shipped by truck to customers.