This research presents an experimental study about the effect of steel fibers on the
main variables of stress- strain curve for high strength concrete on simple compression,
which are: shape of stress- strain curve, ductility factor, energy absorpt
ion capacity. For
this purpose, series of cylinders concrete specimens were prepared in compressive strength
(70 MPa). the steel fiber with aspect ratio of L/D =70 were added at the volume fractions
of (0-1-1.5-2)%. The cylinders were tested under a monotonic loading at compression, and
as a result of the tests, the total curve of stress- strain was obtained. The experimental
results of research showed a positive effect of steel fibers on the behavior of high strength
concrete, this effect increased with increasing volume fraction of steel fibers. It can be seen
from stress-strain curve, whereas the slope of the ascending branch is not much affected.
The descending branch of the stress- strain curve decreases by the increase in the fiber
volume fraction. This means the ductility and toughness improve with the addition of steel
fibers and as a result the behavior of high strength concrete has gone far away from being
brittle as it is used to be.
