Civil Engineering Reference
In-Depth Information
3.11.1 Amount of Fibers
It is well know that crack widths clearly decreased with increasing
ber content
[
82
]. Also, the volume of
uence on the ultimate shear load due
to the improvement of toughness and ductility [
83
].
Susetyo et al. [
26
] found that a
bers has a strong in
fl
ber content of 1 % is required to improve shear
strength, deformation ductility, crack width, and crack spacing. Dinh et al. [
6
]
added that with a 0.75 % volume fraction the increase sin shear strength is
signi
cant. With minor contents (0.5 %) no improvements can be guaranteed [
26
]
and, with contents greater than 1 % no more improvements are observed respected
with 1 %, probably due to the saturation [
6
,
26
].
The beams with
bers exhibited less de
fl
ection and larger ultimate load carrying
capacity than those without
bers [
41
].
After analyzing the results of an extend campaign of bending tests, Altun et al.
[
84
] concluded that
the addition of a 30 kg/m
3
of
bers produced a clear
improvement compared to concretes without
bers. However, when the amount of
bers was 60 kg/m
3
the bene
ts observed where small compared with an amount of
30 kg/m
3
.
Recently, Kim et al. [
85
] proposed a volume fraction of steel
bers of 1.5 % as
the optimal value.
Regarding to self-compacting concretes (SCC), Khayat et al. [
86
] found that a
volume of
bers of 0.5 % could be an upper limit for the production of SCC. A
greater amount of
bers could hinder the SCC characteristics.
3.11.2 Relation Between Casting Procedure and Fiber
Length
The mechanical behavior of the composite improves when decreases the
ber length
in extruded composites and when increase the
ber length in cast composites.
This contradictory trend is due to the difference in
ber failure mechanism,
ber
distribution and
ber orientation in these two systems. In extruded composites the
critical
ber length is shorter than in the cast composites due to the strong
ber-
matrix bond in the extruded composites [
87
].
3.11.3 Fiber Type
Strength and geometry of
uence on the load bearing capacity
of High Strength Fiber Reinforced Concrete beams without bar reinforcement. The
ductile behavior was better in the postcracking range due to the use of high strength
ber have a direct in
fl
Search WWH ::
Custom Search