Fibers as structural element for the reinforcement of concrete
The idea of using a fibrous material to provide tensile strength to a material strong in compression
but brittle, looses itself in the mists of time; in ancient Egypt straw was added to clay mixtures
in order to provide bricks with enhanced flexural resistance, thus providing better handling
properties after the bricks had been dried in the sun.
Other historical cases of fiber reinforcement exist: plaster reinforced with horsehair, or again
with straw in the poorest building conditions, so as to avoid the unsightly occurrence of cracks
due to shrinkage, counter-ceilings made of plaster reinforced through reed canes, cement
conglomerates fiber-reinforced through asbestos, etc.
But the scientific approach to such a problem is definitely more recent.
The presence of fibers having adequate tensile strength, and being homogeneously distributed
within concrete, builds a micro-scaffolding that, on the one side, demonstrates itself being ef-
ficient in counteracting the known phenomenon leading to crack formation due to shrinkage,
and, on the other side, leads the concrete’s ductility(1) to become increasingly relevant with
increasing strength of the fibers. This provides the concrete with a high toughness(2) as well.
As it is known, in the vast majority of currently applied calculation and verification rules, the
concrete’s tensile strength is generally neglected in the calculation route, given concrete’s brittle
behaviour. The use of a fiber-reinforced matrix makes it possible to stabilize tensile properties.
In this way, the tensile strength can be now be exploited as well between other mechanical
properties in the design phase. This highly relevant technical advantage will be reported in de-
tails in chapter 3 of the present publication.
but brittle, looses itself in the mists of time; in ancient Egypt straw was added to clay mixtures
in order to provide bricks with enhanced flexural resistance, thus providing better handling
properties after the bricks had been dried in the sun.
Other historical cases of fiber reinforcement exist: plaster reinforced with horsehair, or again
with straw in the poorest building conditions, so as to avoid the unsightly occurrence of cracks
due to shrinkage, counter-ceilings made of plaster reinforced through reed canes, cement
conglomerates fiber-reinforced through asbestos, etc.
But the scientific approach to such a problem is definitely more recent.
The presence of fibers having adequate tensile strength, and being homogeneously distributed
within concrete, builds a micro-scaffolding that, on the one side, demonstrates itself being ef-
ficient in counteracting the known phenomenon leading to crack formation due to shrinkage,
and, on the other side, leads the concrete’s ductility(1) to become increasingly relevant with
increasing strength of the fibers. This provides the concrete with a high toughness(2) as well.
As it is known, in the vast majority of currently applied calculation and verification rules, the
concrete’s tensile strength is generally neglected in the calculation route, given concrete’s brittle
behaviour. The use of a fiber-reinforced matrix makes it possible to stabilize tensile properties.
In this way, the tensile strength can be now be exploited as well between other mechanical
properties in the design phase. This highly relevant technical advantage will be reported in de-
tails in chapter 3 of the present publication.
It is evident that all these possible behaviours, or different ductility and toughness levels ac-
quired by the concrete, depend both from the quantity of the present fibers as well as from
their mechanical, and geometrical characteristics.
Considering the influence of the fiber geometry on the behaviour of FRC(3) and of SFRC(4),
although any aspect is relevant, it is the relationship between the fiber length and equivalent
diameter (L/D named aspect ratio or slenderness ratio) which is considered as the most charac-
terising element, since ductility and toughness of a fiber-reinforced concrete depend in large
measure on its value
It is evident that all these possible behaviours, or different ductility and toughness levels ac-
quired by the concrete, depend both from the quantity of the present fibers as well as from
their mechanical, and geometrical characteristics.
Considering the influence of the fiber geometry on the behaviour of FRC(3) and of SFRC(4),
although any aspect is relevant, it is the relationship between the fiber length and equivalent
diameter (L/D named aspect ratio or slenderness ratio) which is considered as the most charac-
terising element, since ductility and toughness of a fiber-reinforced concrete depend in large
measure on its value
quired by the concrete, depend both from the quantity of the present fibers as well as from
their mechanical, and geometrical characteristics.
Considering the influence of the fiber geometry on the behaviour of FRC(3) and of SFRC(4),
although any aspect is relevant, it is the relationship between the fiber length and equivalent
diameter (L/D named aspect ratio or slenderness ratio) which is considered as the most charac-
terising element, since ductility and toughness of a fiber-reinforced concrete depend in large
measure on its value
It is evident that all these possible behaviours, or different ductility and toughness levels ac-
quired by the concrete, depend both from the quantity of the present fibers as well as from
their mechanical, and geometrical characteristics.
Considering the influence of the fiber geometry on the behaviour of FRC(3) and of SFRC(4),
although any aspect is relevant, it is the relationship between the fiber length and equivalent
diameter (L/D named aspect ratio or slenderness ratio) which is considered as the most charac-
terising element, since ductility and toughness of a fiber-reinforced concrete depend in large
measure on its value
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