ENHANCEMENT OF IMPACT RESISTANCE OF CONCRETE USING INNOVATIVE SHAPE OF STEEL FIBRES

Concrete is oftenly subjected to impact and other dynamic loads in service.
These loads may occur due to blasts, traffic, and seismic activity. To enhance
the impact resistance of concrete, many types of fibers can be used. In this
research, two shapes of steel fibres are used: hook-ended shape (SF) and a
new spiral shape (SSF) Fig.1. The innovative shape is introduced manually in
fresh concrete with suitable vertical and horizontal alignment.
The test program is designed to study the effect of SF, and SSF on the
impact resistance of concrete and selected mechanical properties. The two
shapes of steel fibres were added at the fraction volume of 0.5%, 1.0%, 2.0%,
and 3.0%. The compressive strength of steel fibers reinforced concrete
(SFRC) enhanced by 43.4% at 2.0% volume fraction relative to plain
concrete. The compressive strength of spiral steel fibers reinforced concrete
(SSFRC) enhanced by a 65% at 3.0% volume fraction relative to plain
concrete. The splitting tensile strength and modulus of rupture of SFRC
improved with increasing of fiber volume fraction recording 52.6% and
137.5% enhancement, respectively, at 2.0% volume fraction. The splitting
tensile strength and modulus of rupture of interlocked spiral steel fibres
(SSFRC*) improved with the increase in volume fraction up to 3.0%,
recording 147% and 62.5% enhancement, respectively. Also, The toughness
index of SFRC enhanced with the increase in the fraction up to 2.0%. The
toughness indices I5, I10, and I20 registered values of 10.7, 20.5, and 35.1,
respectively, at 2.0% fraction volume. The toughness index of SSFRC*
enhanced with increasing the fraction volume up to 3.0%. The indices I5, I10,
and I20 recorded values of 9.76, 18.78, and 35.8, respectively, at 3.0% fraction
volume.
The impact resistance of SFRC improved with the increase in the fiber
content up to 2.0%, recording 33 times that of the impact resistance of plain
concrete, at 2.0% fraction volume. The impact resistance of SSFRC*
enhanced with the increase in the fiber volume fraction recording 116 times
the impact resistance of plain concrete, at 3.0% fraction volume.