Experimental Tests to Study the Influence on the Shear Behavior of Fibers of Different Characteristics - On Shear Behavior of Structural Elements Made of Steel Fiber Reinforced Concrete - page 103

Most research on elements of FRC focus only on the type of ber (shape), aspect

ratio and amount of ber is also a very

important factor to consider and there is little research about this [ 11 ].
To analyze the

bers [ 9 , 10 ]. However, the strength of the

ber contribution to shear capacity, Codes usually consider only
the residual concrete strength at 2.5 mm crack opening in the exural test (f R3 ).

However, it is possible to produce concretes with a similar f R3 but with very
different post cracking behaviors. This is possible using

fl

bers with different

geometries and yielding capacity [ 12 ].
The aim of this chapter is to obtain self-compacting ber reinforced concrete

(SCFRC) with a large variability of mechanical behaviors by using different ber

types, and to analyze its effect on the shear behavior, by considering the service-
ability limit state (SLS), the ultimate limit state (ULS), and also analyzing the
ductility on the load/de

ection and load/shear crack opening behavior of these
beams. To achieve the objectives, an experimental program consisting of SCFRC
double-T beams was designed. Beams were 2,400 mm long, with a double-T cross-
section, a height of 350 mm and web width equal to 90 mm.
The main parameters of study were: concrete compressive strength level (30, 50,
80 MPa) and steel

fl

bers with different strength levels, lengths,
and aspect ratios (length/diameter)]. The amount of steel

bers quality [using

bers (50 kg/m 3 ) was kept

constant. Beams without bers were produced as a reference.

6.2 Experimental Program

Three concrete matrices, characterized by their compressive strength (30, 50 and
80 MPa), named as Low (L), Medium (M) or High (H) strength, were produced.
With those concrete matrixes, 16 different self-compacting concretes were derived
by only adding ber content was always 50 kg/m 3 . Each bers. When used, the

concrete is then de ned by the compressive strength level and the ber geometries

(lengths and aspect ratio) as well as ber strength levels. Table 6.1 shows the

nominal mix designs.

Table 6.1 Mix designs (kg/m 3 )
Low strength
concrete (L)

Medium strength
concrete (M)

High strength concrete (H)

Cement 52.5R 290 340 450

7/12 aggregate 658 731 610

Sand 954 954 1075

Filler 180 125 0

Silica fume 0 0 50

Steel bers 50 50 50

Water 210 210 175

Superplasticizer 5.20 7.45 26.7