Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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NON-METALLIC REINFORCEMENT MEMBER FOR THE REINFORCEMENT OF A STRUCTURE AND
PROCESS OF ITS MANUFACTURE
FIELD OF THE INVENTION:
The present invention generally relates to a member for the
reinforcement of a structure of material. More specifically, the present
invention is
concerned with a fiber reinforced plastic rod for the reinforcement of
concrete.
BACKGROUND OF THE INVENTION
Concrete materials have been used extensively in many civil
engineering structures. These include bridges, walls for buildings, parking
garages,
wave breaking structures along seashores etc. This is because concrete has
good
durability at ambient operating conditions, and also because of its low cost.
However, concrete is usually strong in compression but weak in tension. As
such, to
reinforce concrete in applications where tension load is present, steel
reinforcing
rods have been used. Steel reinforced concrete is ever present in our everyday
lives, and these materials have been used in construction projects for many
years.
Steel is used to reinforce concrete due to its good strength, toughness
and ductility. However, steel does suffer from corrosion. Moisture and water
does
2o attack and corrode steel. Particularly in cold climates like in Canada an
in many
states in the United States, where salt is used to de-ice each winter, the
problem of
corrosion of steel in concrete used in roads and bridges is even worse. The
repair of
the Montreal Champlain bridge across the St. Lawrence River is one example.
Every
year, workers have to cut up the concrete, dig up the steel reinforcing rods,
clean
them of rust, and apply an epoxy coating before putting the concrete over them
again. This repair is expensive, not only in the cost of cutting, digging,
repair but also
in terms of the disruption of traffic and causes disturbance to many
commuters. This
problem is not unique to just the Champlain bridge alone. Many infrastructures
in
many cities in Canada, the U.S., and even Europe have been in operation for
more
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than 40 years, and they are reaching a stage where either rehabilitation or
replacement is necessary. The enormous cost of this project certainly requires
some
good thinking about how one should do the job better, so that at least the
life of
these structures can be longer than what they used to be.
Fiber reinforced plastic (FRP) rods have been receiving a lot of
attention as an alternative for steel in the reinforcement of concrete. This
is due to
the excellent corrosion resistance of FRP materials in environment that
corrodes
steel, such as water and alkali. As such, there has been accelerated research
going
on in this area and there are many companies that manufacture and sell the FRP
rods. The current FRP rods have diameters that vary from 12.7 mm to 25.4 mm.
They are made by pultrusion technology where the fibers wetted with resins are
pulled through a heated die where they consolidate and cure. A product made by
this technique has good properties in terms of stiffness and strength along
the
direction of the rod. However, the cross section is uniform. This uniformity
in cross
~5 section allows long length to be made economically. However, in terms of
providing
reinforcement to the concrete, the uniformity of cross section can only rely
upon
friction at the interface between the rod and the concrete. There is no
mechanical
interlock between the rod and the concrete. Steel rods have some form of
mechanical interlock built in by the calendering process. Some manufacturers
of
20 FRP rods also try to mimic this mechanical interlock either by adding
helical tows on
the surface of the FRP rods, or to add sand particles to the surface of the
FRP rods
to increase the roughness. However, these additions are only bonded to the
main
rod by secondary bond with very low shear resistance. The result is that the
FRP
rods exhibit low shear transfer to the concrete as compared to that of steel.
25 Fiber reinforced plastic materials consist of fibers such as glass fibers,
carbon fibers, kevlar fibers; and matrix materials such as epoxy, polyester,
thermoplastics. These fiber reinforced plastic materials are strong, and
corrosion
resistant. These materials lend themselves well as an alternative to steel in
making
reinforcing rods for concrete. Over the past ten years, there has been
intensive
3o research activity in the development of these fiber reinforced plastic
rods. These
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rods are made by a process called Pultrusion. In this process, the fibers
(wetted
with resins) are pulled through a heated die. During this pulling process, the
resin
hardens and the fibers and resins consolidate into a hard and strong material.
These
pultruded rods have been made and commercialized by companies in North America
and in Japan. In Canada, there is Pultrall in Thetford Mines. In the United
States,
there are Hughes Brothers, Master Builders etc. The pultruded rods seem to be
an
excellent alternative to steel for the reinforcement of concrete.
However, conventional fiber reinforced plastic rods still suffer from two
major drawbacks. Firstly they are made by the pultrusion process. As such
their
cross section is uniform along the length of the rod. Since the rod depends on
friction between the concrete and the rod for the reinforcement, the uniform
cross
section does not provide much resistance. Many of the manufacturing companies
have added external ribs to improve the frictional resistance. However, these
ribs
are held to the rod by weak secondary bonds and the resistance is only
marginally
~5 improved. Secondly, the resin used is polyester, which is a thermoset. As
such, the
material is brittle and it is very difficult if not impossible to bend a rod.
This lack of
workability limits the ability of the field worker to bend the rod to fit to a
certain
geometrical constraint on the job.
OBJECT OF THE INVENTION
2o The general object of the present invention is therefore to provide an
improved reinforcement member for the reinforcement of a structure of
material.
SUMMARY OF THE INVENTION
More specifically, in accordance with the present invention there is
provided a reinforcement member to be embedded in a structure of material,
this
25 member comprises a longitudinal main body having an outer surface and
spaced
apart embossments formed along the length of the longitudinal body, these
embossments are integral with the longitudinal main body, wherein, when the
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member is embedded in the structure, the embossments mechanically interlock
with
the structure.
In accordance with another aspect of the present invention there is
provided a process for making the reinforcement member disclosed herein, the
process comprises:
(a) making a core having the configuration of the member;
(b) making a tube of yarns;
(c) incorporating the core within said tube so as to provide a core-
tube assembly;
(d) placing the core-tube assembly within a bag of high temperature
resistant material;
(e) exposing the bagged core-tube assembly to such temperature and
pressure as to mold said core-tube assembly into the reinforcement member;
(~ providing for the reinforcement member to solidify; and
~ 5 (g) removing the bag from the reinforcement member.
An advantage of the present reinforcement member is that the
embossments along the length of its longitudinal main body provide for the
mechanical interlock of the reinforcement member with the structure that is to
be
reinforced, rather than just interfacial friction alone.
2o Another advantage of the present reinforced member is that it is made
using thermoplastic resin which allows the reinforcement member to be
bendable.
An advantage of the process for making the reinforcement member of
the present invention is that it is relatively inexpensive.
It should be understood that the term "rod" herein may be construed to
25 mean "bar", "rebar" and the like.
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It should also be understood that the term "non-metallic" may be
construed to mean substantially having no metal so as to substantially avoid
corrosion.
Other objects, advantages and features of the present invention will
5 become more apparent upon reading of the following non restrictive
description of
preferred embodiments thereof, given by way of example only with reference to
the
accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS:
In the appended drawings in which the reference numbers indicate like
elements and in which:
Figure 1 is a perspective view of a reinforcement member in
accordance with a preferred embodiment of the present invention;
Figure 2 is a lateral elevational view of the reinforcement member of
Figure 1;
Figure 3 is a cross-sectional view of the reinforcement member of
Figure 2 along the line 3-3; and
Figure 4 is a view of the reinforcement member similar to Figure 3, with
the reinforcement member being embedded in concrete.
DESCRIPTION OF THE PREFERRED EMBODIMENT
2o With reference to the appended drawings a preferred embodiment of
the present invention will be described hereinbelow:
Figures 1 and 2 illustrate a preferred embodiment of the reinforcement
member according to the present invention, generally denoted 10, and adapted
to
be embedded in a structure of material for the reinforcement thereof.
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Member 10 may be used to reinforce a variety of structures made for a
variety of materials as is known in the art, in one aspect of the present
invention
member 10 is used for the reinforcement of a mass of concrete.
Member 10 can be a rod or any like elongated structure in accordance
with the present invention.
The member or rod 10 is made of a non-metallic material or includes
substantially no metal. In this way the rod is substantially non-corrosive.
Hence, the
rod may be made of non-corrosive materials. Advantageously, member or rod 10
is
made of a plastic material. Preferably the plastic material is a thermoplastic
resin.
Thermoplastic resin provides for rod 10 to be bendable.
As aforementioned this rod 10 may be a solid piece of material or may
be a tube over an appropriate core as will be more clearly explained when the
process of making the present invention is described below.
Rod 10 comprises a longitudinal main body 12 having an outer surface
14 ( see Figures 3 and 4). It is advantageous that this outer surface 14
includes no
metal or non-corrosive materials.
The body 12 may be a generally cylindrical configuration. Of course, it
is within the scope of the present that the longitudinal main body 12 may have
another suitable configuration, what is advantageous is that the longitudinal
main
2o body 12 be configured and sized for being embedded in a structure of
material for
the reinforcement thereof.
As shown, the longitudinal main body 12 includes embossments 16.
Embossments 16 are structurally integral with the longitudinal main
body 12 and are spaced apart in non-contiguous fashion along the length of the
2s longitudinal main body 12. As shown, embossments 16 have a generally
ellipsoidal
configuration. Of course, the embossments 16 may have any other configuration
that would provide the best efficiency of reinforcement as is known to the
ordinary-
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skilled artisan. Furthermore, the embossments 16 may be equally or unequally
spaced apart depending on the requirements from the design of the structure
that is
to be reinforced. The selection of the size, width, general configuration of
the
embossments 16 as well as the space between each embossment 16 is a function
of the dimension of the rod 10 and the type of material and structure that is
to be
reinforced.
Figure 3 shows that layers of outer fiber reinforcement 18 be placed
along the length of the rod 10.
As will be better explained when the process of making the present
1o invention is detailed below the fiber reinforcement material 18 may be a
braided tube
over an appropriate core 20 (see Figure 3).
Of course the rod 10 may be made of a single piece of material.
In operation and with particular reference to Figure 4, rod 10 will be
embedded in a structure of material such as concrete 30 for example.
As is known to the skilled artisan, the general configuration and size of
the rod 10 will depend on the type of concrete 30 that is to be reinforced.
Due to its thermoplastic resin composition rather than being made of
thermoset resin (such as polyester or epoxy) as with the current.rods, the rod
10 will
be bendable allowing flexibility for the field worker to work on the rod 10 to
fit the
2o constraints of the geometry of the job.
The embossments 16 provide for the rod 10 to have varying cross
sections along its length, which provide mechanical interlock with the
concrete 30
rather than just interfacial friction alone. Hence, the shear transfer between
the rod
10 and the concrete 30 is through mechanical interlock, in addition to the
friction
between the rod outer surface 14 (including the layers of fiber reinforcement
18) and
the concrete 30. As such, rod 10 is a much more effective reinforcing member.
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The reinforcement member of the present invention may be produced
as described hereinbelow.
As shown in Figures 3 and 4, a core member 20 is made having the
configuration of the reinforcement member 10 including the embossments 16. The
core member 20 material is made of high temperature resistant material.
Advantageously, the core 20 is a solid cylinder with embossments 22
(see Figures 3 and 4) along its length. The embossments 22 of the core provide
the
form for the embossments 16 of the reinforcement member 10. The core 20 can be
made of an inexpensive material such as low-cost ceramic, metals or plastics.
The
1o embossments 22 along the length of the core can be made by machining a
larger
diameter rod (not shown) into a smaller diameter rod (not shown) with the
embossments 22 remaining. The total core member 20 with embossments 22 can
also be molded or cast using appropriate tooling. The aspect ratio of the
embossment 22 (width over length) on the core depends on the reinforcement
effect
required. The pitch of embossments 22 (distance between embossments) varies
depending on the required reinforcement effect.
A tube 18 is made of mingled fibers and plastic yarns. Advantageously
the comingled fibers and plastic yarns are braided into a braided tube.
Preferably, this tubular braid 18 is made by braiding tows consisting of
2o comingled stifF and strong fibers (such as carbon, glass, aramid) together
with fibers
made of a thermoplastic material (such as polyamide, polypropylene,
polyethylene).
The braid consists of axial tows and helical tows. Advantageously, the amount
of
axial tows is much larger than the amount of helical tows to ensure good
properties
along the axial direction. The tubular braid 18 should have an inside diameter
25 appropriate to the size of the reinforcing member 10 to be made. The braid
18 can
be made with a mandrel or without the mandrel. When the braid 18 is made with
the
mandrel, then the core member 20 is used as the mandrel. When the tubular
braid
18 is made without the mandrel, then the core 20 is inserted into the braided
tube 18
afterwards as will be described below. Making the tubular braid 18 without the
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mandrel provides flexibility in infinite length of the braided tube 18, which
can
significantly reduce the cost of production.
The core 20 is incorporated into the braided tube providing a core-tube
assembly.
In one example, the incorporation of the core 20 inside the braided
tube 18 is done by using the core 20 as the mandrel for braiding as described
above. If the core 20 is not used as the mandrel and the braid tube is made
without
the core 20, then the core 20 can be inserted into the braided tube 18.
Insertion can
be done by sliding the core 20 along the length of the braided tube 18. Care
should
be taken to assure the uniform distribution of the braided tows on the core
20.
The core-tube assembly is then placed inside a high temperature
resistant bagging material (not shown).
Advantageously, the high temperature bagging material should
withstand temperatures high enough to melt the thermoplastic fibers mentioned
above. For example, a bagging material made of Kapton can be used. The edges
of
the bag should be sealed so that vacuum can be drawn inside the bag. , The bag
is
subjected to vacuum so that the bag material presses the braided material 18
against the core 20 to conform to the configuration of the core 20.
The bagged core-tube assembly is then exposed to high temperature
2o and pressure for a sufficient amount of time for the thermoplastic to melt
and to
consolidate the fibers 18 to the shape of the core 20.
The whole bagged assembly is placed inside an oven with facilities to
apply both temperature and pressure. The temperature should be large enough to
melt the thermoplastic fiber material mentioned above. For example, if
polyamide is
used, a minimum temperature of 200° C should be applied for 30 minutes.
Pressure
is applied to consolidate the reinforcement member 10. The pressure can range
from 100 psi (683 kPa) to 200 psi (1367 kPa).
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After the molding process (heating and pressurization for sufficient
amount of time), the heat and pressure can be turned off to allow sufficient
time for
the reinforcement member 10 to cool down and solidify. The oven can be left to
cool
normally to room temperature.
5 ~ The bagging material is removed from the reinforcement member 10.
It is to be understood that the invention is not limited in its application
to the details of construction and parts illustrated in the accompanying
drawings and
described hereinabove. The invention is capable of other embodiments and of
being
practiced in various ways. It is also to be understood that the phraseology or
terminology used herein is for the purpose of description and not limitation.
Hence,
although the present invention has been described hereinabove by way of
preferred
embodiments thereof, it can be modified, without departing from the spirit,
scope and
nature of the subject invention as defined in the appended claims.
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