Abstract:
The potential use of fiber reinforcement for enhancing the mechanical properties and shear
capacity of fiber reinforced concrete beams had been clearly established and recognized that
fiber reinforcement is an effective way to enhance the mechanical performance, shear
behavior and fracture toughness of concrete in all modes of failure. An experimental study
was performed to investigate effect of two different types of fibers: micro and macro synthetic
fiber on the workability, compressive strength, splitting tensile strength, flexural strength and
shear behavior of synthetic fiber reinforced beam with concrete strengths,25and 40 MPa,
and fiber volume fractions,0.2,0.35 ,0.50, and 0.65% of concrete volume. The test results
showed that the workability of concrete decreases as the volume of fibers and concrete
strength increases. The micro SNFRC beams with a strength of 25MPa at 0.2,0.35,0.5, and
0.65% volume fractions decreases the compressive strength by 12,12.31,23.96, and 44.6%,
while macro synthetic fibers improved the compressive by at least 3.87, 5.16,5.3 and 5.39%,
respectively compared to the control specimen. Likewise, the compressive strength of fiber
reinforced concrete with 40MPa decreases by 2.17 % for 0.35%fiber content and, 72% for
0.65% fiber content and 10.48 % for 0.65% of both micro and macro SNFRC beam
respectively. As the volume of micro synthetic fibers increases the tensile strength of micro
SNFRC beam constantly decreases up to 14.93% and 61.33% for 0.65%fiber content in both
25 and 40MPa concrete strength respectively. However, macro SNFRC beam with a strength
of 25MPa at 0.20,0.35, and 0.50% volume fractions enhanced the tensile strength by
4.75,5.88 and 7.0% respectively and in the same way it increases by 10.47% at 0.35% fiber
content and by 5.71% at 0.65% fiber content in concrete with 40MPa strength. The micro
SNFRC with a concrete strength of both 25 and 40 MPa showed a decreases in flexural
strength particularly for a fiber volume fraction of greater than 0.35%. With the addition of
macro synthetic fiber, the flexural strength of concrete with 25 MPa increases by
0.46,2.77,2.3 and 7.39% at 0.20,0.35,0.50, and 0.65% fiber content and decreases by 35.1at
0.35%and 38.9% at 0.65% fiber content in SNFRC with strength of 40MPa. Average shear
strength of micro and macro synthetic FRC greatly enhanced as the fiber volume content of
the concrete increases. The flexural and shear toughness behavior of the SNFRC is highly
boosted and more effective in higher strength concrete (40 MPa) than in normal strength
concrete (25 MPa).