Conventional fiber reinforced concrete, sometimes called FRC, is concrete that has been strengthened by adding shreds of other materials to the wet concrete mix. Concrete is quite brittle; it has very good compressive strength but comparatively little tensile strength, which makes it likely to crack under many conditions. Cracking leads to further damage. Fiberreinforced concrete is less likely to crack than standard concrete.
Current research suggests that microfibers, rather than long fibers, best increase tensile strength. However, adding fibers causes relatively little improvement in impact resistance. Polypropylene fibers reduce damage from freeze-thaw cycles and reduce the chances of spallingor explosion if there is a fire. Cellulose fibers from genetically modified pine trees have also shown promise in testing.