Today precast concrete manufacturers are adding synthetic fibers to their products. Through experience, they have found that fibers not only control cracking but improve impact resistance and watertightness.
DOUBLE PROTECTION: THE BELT AND SUSPENDERS APPROACH
An Ohio precaster/contractor who builds multistory structures uses synthetic fibers in addition to conventional nonstructural reinforcement (shrinkage and temperature steel). A Chicago-area firm that makes sculptures and fountains also combines fiber concrete and welded wire mesh reinforcement. A Texas manufacturer uses fibers to replace wire mesh in precast septic tanks. The mesh was hard to place and fibers required less labor.
Fibers aren't intended as a replacement for principal reinforcement used for structural purposes. In units such as steps, fence rails, and wall and floor panels, structural strength must be provided by rebars.