In this research the main focus is on the analysis of
short dispersed fibres on
the cement-based matrix. The aim is to test a few
structural ideas and to
compare the results with theoretical values.
When considering fibre-reinforced concrete as a
material, the main interest lies on the post-crack
tensile strength of the
fibre composite. Fibres bridge over cracks. This
post-crack strength gives the
ductility, impact strength and beneficial cracking
behaviour. Under bending
load the effect of fibres can be observed with a lower
fibre amount than under
Tests were performed in order to verify the feasibility
of some structural
ideas, which were inverted T-beam, low-pressure concrete
pipe, and thin panel.
Also, tests elsewhere in VTT are referred to, namely the
crack control effect
of fibres on beams and fibres as a shear reinforcement.
The flange of the inverted T-beam has to be reinforced,
because the flange
supports the slabs. From the load test results one can
draw a conclusion that
the fibre amount should be near 1 volume per cent, or
higher, to achieve the
same level of ultimate load as with conventional
reinforcement. For steel this
means 30 % more than in the form of reinforcement bars.
The idea of using steel fibre in concrete pipes is not
new. The difficulties
are in watertightness. With all the fibre-types used it
is possible to fulfil
the requirement of the external load.
Tests with fibre-reinforced thin panels were carried out
in order to study the
differences in deformations due to the non-symmetry. The
property here is the free shrinkage of concrete.
Fibres tend to increase the load level at which visible
cracking first appears.
The average crack width of a fibre-concrete beam was
about 75%, compared to
that of beam without fibre. The depth of the crack was
smaller with fibre
specimens. The ultimate flexural capacity of a concrete
beam with conventional
reinforcement increases slightly when fibres are added to
The nature of fracture is brittle when fibres are used.
This is because the
post-crack strength of fibre-concrete is usually lower
than the cracking
strength. Also the fracture occurs due to the fibre
pull-out. The fibres are
dispersed randomly and this also increases the
uncertaintity of capacity. The
safety level has to be studied carefully case by case.
The quality control
methods have to be chosen correctly to ensure the desired
|Place of Publication||Espoo|
|Publisher||VTT Technical Research Centre of Finland|
|Number of pages||78|
|Publication status||Published - 1995|
|MoE publication type||Not Eligible|
- construction materials
- fiber reinforcement
- reinforced concrete
- mechanical properties