Fly Ash (FA) is a residual material of energy production using coal, which has been
found to have numerous advantages for use in the concrete industry. Some of the
advantages include improved workability, reduced permeability, increased ultimate
strength, reduced bleeding and reduced heat of hydration. The use of FA in concrete
is found to affect strength characteristics adversely. One of the ways to compensate
for the early-age strength loss associated with the usage of FA is by incorporating
fibers, which have proved to be very efficient in enhancing the strength characteristics
of concrete. The addition of fibers to concrete considerably improves its structural characteristics such as static flexural strength, impact strength, tensile strength,
ductility and flexural toughness. For long-term strength, toughness and high stress
resistance, Steel Fiber Reinforced Concrete (SFRC) is increasingly being used in
structures such as flooring, housing, precast, tunnelling, heavy duty pavement and
mining. Generally, aspect ratios of steel fibers used in concrete mix are varied between
50 and 100. The most suitable volume fraction values for concrete mixes are between
0.5% and 2.5% by volume of concrete. In general, the character and performance of
Fiber Reinforced Concrete (FRC) changes with varying concrete formulation as well
as the fiber material type, fiber geometry, fiber distribution, fiber orientation and
fiber concentration.
Although there were numerous studies carried out on the influence of fiber addition
in concrete mixture on mechanical and durability properties of concrete, limited
research work has been carried out concerning the influence of fiber addition in
concrete with pozzolans. Topcu and Canbaz (2007) studied the effect of steel and
polypropylene fibers on the mechanical properties of concrete containing FA.
According to them, addition of fibers provides better performance for the concrete,
while FA in the mixture may adjust the workability and strength-loss caused by
fibers, and improve strength gain. Qian and Stroeven (2003) investigated the
optimization of fiber size, fiber content and FA content in hybrid polypropylenesteel
fiber concrete with low fiber content based on general mechanical properties.
The results showed that a certain content of fine particles such as those found in FA
is necessary to evenly disperse fibers. Gutierrez et al. (2005) studied the effect of
the pozzolans on the performance of fiber reinforced mortars. They reported that in
general, pozzolanic materials, especially silica fume and metakaolin, improve the
mechanical performance and the durability of fiber-reinforced materials. The FA
addition had a low performance, which was attributed to its low degree of
pozzolanicity. Eren and Celik (1997) investigated the effect of silica fume and steel
fibers on some properties of high-strength concrete. The results showed that increase
in the amount of silica fume and fibers decreases workability. They reported that
while silica fume has an effect on compressive strength, volume percentage of steel
fibers has a little effect.
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