An experimental research investigation of the fresh and hardened mater
ial properties of fibrillated polypropylene fiber reinforced concrete
is reported. Fiber lengths were 1/2 and 3/4 in., and volume fractions
were 0.1, 0.3, and 0.5%. Fiber effects on concrete properties were ass
essed. Properties studied were slump, inverted slump cone time, air co
ntent, compressive and flexural behaviors, impact resistance and rapid
chloride permeability, and volume percent of permeable voids. An inno
vative method of characterizing the flexural behavior of fibrillated p
olypropylene fiber concrete was proposed. The new method was dependent
on the post-peak flexural resistance of concrete. For impact resistan
ce and flexural behavior, it was concluded that 3/4-in.-long fibers we
re more effective than 1/2-in.-long fibers for volumes of 0.3 percent
or less, while 1/2-in.-long fibers were more effective for 0.5 percent
volume.