WO2006001702A1

WO2006001702A1 - Method and equipment for the manufacturing of reinforcing bars of composite material

Info

Publication number: WO2006001702A1
Application number: PCT/NO2005/000203
Authority: WO
Inventors: Arne Roger Hole; Rune Harald Gaarder
Original assignee: Exel Oyj
Priority date: 2004-06-23
Filing date: 2005-06-13
Publication date: 2006-01-05
Also published as: NO20042647L; NO20042647D0; NO321711B1

Abstract

A method for the manufacturing of reinforcing bars (8) of composite material, in particular intended to be used for the reinforcement of concrete. The reinforcing bar, preferably being of rectangular or square shape, may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process. The bar is made in the forming process with at least 50% reinforcing fibres by weight and a matrix which impregnates the fibres through a bath, by spray injection or pressure. The surface of the reinforcing bar, after being hardened or essentially being hardened, is provided with or coated with a resin or adhesive whereby a pattern in the form of a plurality of protrusions is provided or imprinted in the adhesive on the surface of the bar by means of a tool (5) with grooves or recesses (6) corresponding to the shape of the wanted shape of the protrusions, which is pressed against the surface of the bar (8) until the adhesive is hardened or essentially hardened.

Description

Method and equipment for the manufacturing of reinforcing bars of composite material

The present invention relates to a method and equipment for the manufacturing of reinforcing bars of composite material.

The reinforcing bar according to the invention may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process. The bar is made in the forming process with at least 50% reinforcing fibres by weight and a matrix which impregnates the fibres through a bath, by spray injection or pressure.

Composite bars of the above type is used for the strengthening and stiffening of different products and constructions made of materials like metal, concrete, wood, plastics, stone, ceramic and combinations of these where sufficient bond between the bars and materials is required to achieve structural functionality and optimisation on slendemess, weight, size and cost. But this is often obtained on account of strength, stiffness or by becoming susceptible to oxidation such as steel and other metals causing problems with corrosion, discoloration and thereby loss of structural strength. In some cases where metals are used to strengthen or stiffening the products there are problems with elongation or variation in material physical behaviour that cause cracking or insufficient bond between the product's material and the strengthening elements, i.e. the reinforcing bars.

The reinforcing material according to the present invention is a continuous fibre and matrix composite often called FRP (Fibre Reinforced Polymer) which is being used in a variety of construction materials due to excellent and flexible physical material properties such as high specific strength, light weight, none or low electric conductivity, non-magnetic properties, high resistance against acids and chlorides or aggressive environments, as well as formability and shaping. As stated above, steel and metals in general are susceptible to oxidation which cause corrosion of and rust on ferrous metals due to hydroxides of iron and oxides from atmospheric oxygen in the presence of water. As long as the pH is maintained at high alkalinity (pH 12 - 14) and in combination with very good poured concrete quality, the steel keep passive leading. Too low pH, low concrete quality, insufficient product quality, poor execution of work, or exposure to strong acid can cause penetration of the protecting concrete zone that should protect the steel reinforcement rebar, i.e. chlorine ions from salt contaminated aggregates, road salt, marine environmental, seawater, carbonisation, access to CO₂, access to oxygen, and moisture. Furthermore, conditions which may result in chemical deterioration of the concrete, i.e. by sulphate or acid attack, or mechanical deterioration of the concrete from freezing and thawing in a wet or moist condition, may in turn cause rust and corrosion of the steel reinforcement, cracking of the concrete and loss of structural strength. When the reinforcement start corroding (rusting), the ferrous oxide will expand and cracks are initiated in the concrete due to internal stresses caused by the rust. Concrete will fall off and the steel reinforcement bars will be exposed to the atmosphere and the environment that caused the corrosion process, the speed of the process will further increase and the structure will be loosing structural strength and may in worst case collapse. Controlling these parameters is difficult and substantial economical and structural problems for concrete structures is caused all over the world. Due to lack of other alternative strengthening materials, steel reinforcement bars often have been misused in concrete structures.

As stated above, composite reinforcement bars are previously known and have been used to a minor extent. Such known bars are, however, encumbered with a major disadvantage, namely that bonding between the product's material (concrete) and the strengthening bar (FRP-bar) varies over the length of the bar. The fact that traditional bars are designed with a circular shape, further makes it difficult to provide the surface with the required roughness.

In the applicant's own WO 03/050364 is described a reinforcing composite bar where the bar is of a rectangular or preferably square shape with rounded corners, and where the bar under the manufacturing process is provided with a surface pattern or design comprising a multiplicity of depressions, dents or recesses formed in a texture.

With the present invention is provided a composite reinforcing bar with excellent bonding properties and where the required surface roughness is provided in a simple and cheap manner. The invention is characterized in that the surface of the reinforcing bar, after being hardened or essentially being hardened, is provided with or coated with a resin or adhesive whereby a pattern in the form of a plurality of protrusions is provided or imprinted in the adhesive on the surface of the bar by means of a tool with grooves or recesses corresponding to the shape of wanted shape of the protrusions, which is pressed against the surface of the bar until the adhesive is hardened or essentially hardened, as defined in the attached independent claims 1 and 5.

Dependent claims 2 - 5 and 6 - 9 define preferred embodyments of the invention.

The invention will be further described in the following by way of example and with reference to the drawings where,

Fig. 1 shows a schematic view of an apparatus by which a reinforcing bar according to the present invention may be manufactured,

Fig. 2 shows partly in perspective an example of a tool element according to the present invention by which the pattern on the surface of a reinforcing bar is made,

Fig. 3 a, b shows, in larger scale, an example of a segment according to the present invention intended to be provided on endless conveyers as shown in Fig. 1 , and where Fig. 3 a shows segment provided in a distance from the bar, and Fig. 3b shows the segments provided in contact with the bar.

Fig. 4 depicts a tri-dimensional sketch of the segments in Fig. 3.

Fig. 5 depicts a tri-dimensional sketch of an alternative bar design with rectangular, flat shape were alternative segments are used. The present invention relates as stated above to a method for the manufacturing of reinforcing bars 8 of composite material, in particular intended to be used for the reinforcement and strengthening of concrete. The reinforcing bar 8, preferably being of rectangular or square shape, may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process, as shown in Fig 1 , where the bar is made from fibres 2 which are drawn through a unit 1 where the matrix material is provided, and further through a forming and heating unit 3 and unit 4, including heating means (not further shown) where the bar 8 is formed, hardened or partly hardened. The bar is preferably made in the forming process on a continuous basis with at least 50% reinforcing fibres by weight and with a matrix (resin mixture) which impregnates the fibres through a bath, by spray injection or pressure. The temperature inside unit 3 shall be between 90-250 ⁰C and the temperature inside unit 4 shall be between 120-250 ⁰C.

The surface of the reinforcing bar 8, after being hardened or essentially being hardened, is provided with or coated with a resin or adhesive whereby a pattern in the form of a plurality of protrusions is provided or imprinted in the adhesive on the surface of the bar 8 by means of a tool 5, as shown in Fig. 2, with grooves or recesses 6 corresponding to the design of the wanted shape of the protrusions. It is of vital importance that the tool 5 is pressed against the surface of the reinforcing bar until the adhesive is hardened or essentially hardened.

The tool as shown in Fig. 2 may be provided on endless conveyors 9, in an imprinting and heating unit 4 (see Fig. 1) on each side of the reinforcing bar being produced, whereby the reinforcing bar is pulled between the conveyors 9 such that the tools 5 are pressed against the surface of the bar 8 by means of the conveyors. Preferably, the tools 5 when being provided on endless conveyors 9, may be in the form of individual segments 7, as is shown in Fig 3 a, b and Fig. 4 and Fig. 5, being made from aluminium or other metals, special high temperature resistant polymer materials, or ceramic materials. The tools 5 are as stated above pressed against the surface of the bar until the adhesive or resin is hardened, and the tool is then removed or retracted from the bar. To reduce sticking or avoid that the tool is sticking to the surface of reinforcing bar after hardening of the adhesive, the surface of the tool may be provided with a non-sticking coating such as Teflon®.

As is shown in Fig. 3 the segments 7 may be in the form of angularly shaped elements with the required or wanted patterns provided on each arm 10, 11 of the element. The two elements 7 may each be provided on diametrically placed conveyors 9, whereby the elements, when making the pattern on a reinforcing bar, are forced against the surface of the reinforcing bar 8. An option may be to supply the adhesive initially on the surface of the tool 5, whereby the adhesive is provided on to the surface of the reinforcing bar 8 and the pattern is formed in one operation by pressing the tool against the reinforcing bar. It should, however, be stressed that the pattern formed on a reinforcing bar as described above by initially providing a resin on the surface and then forming the pattern by a pressing tool against the surface of the bar is just an option. The pattern may as well be formed under the final forming of the bar as such, without using additional resin, for instance by pressing a tool against the surface under the hardening operation of the bar, for instance in a common hardening and imprinting unit 3, 4.

Fig. 5 shows a tri-dimensional sketch of an alternative bar design with rectangular, flat shape were alternative segments are used in the form flat elements being pressed only against the upper and lower surfaces of the bar (from two sides only).

Claims

1. A method for the manufacturing of reinforcing bars (8) of composite material, in particular intended to be used for the reinforcement of concrete, where the reinforcing bar, preferably of rectangular or square shape, may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process and where the bar is made in the forming process with at least 50% reinforcing fibres by weight and a matrix which impregnates the fibres through a bath, by spray injection or pressure characterised in that the surface of the reinforcing bar (8), after being hardened or essentially being hardened, is provided with or coated with a resin or adhesive, whereby a pattern in the form of a plurality of protrusions is provided or imprinted in the adhesive on the surface of the bar (8) by means of a tool (5) with grooves or recesses (6) corresponding to the shape of wanted shape of the protrusions, which is pressed against the surface of the bar until the adhesive is hardened or essentially hardened.

2. A method in accordance with claim 1 , characterised in that the resin or adhesive represents a reminder or rest on the bar surface after forming, not being fully hardened.

3. A method in accordance with claim 1 and 2, characterised in that the tool is provided on endless conveyors (9) on each side of the reinforcing bar (8) being produced, whereby the reinforcing bar is pulled between the conveyors (9) such that the tools (5) are pressed against the surface of the bar (8) by means of the conveyors.

4. A method in accordance with claims 1 and 3, characterised in that the tools are in the form of individual segments (7) provided on the endless conveyor (9).

5. A method in accordance with claim 1 - 4, characterised in that the adhesive initially is supplied on the surface of the tool, whereby the adhesive is provided on to the surface of the reinforcing bar and the pattern is formed in one operation by pressing the tool against the reinforcing bar.

6. Equipment for the manufacturing of reinforcing bars (8) of composite material, in particular intended to be used for the reinforcement of concrete, where the reinforcing bar, preferably of rectangular or square shape, may be formed in a forming process by pultruding, extrusion or moulding, or a combination of these, of continuous fibres and matrix (resin) in a one-line process or in combination with a second-line process and where the bar is made in the forming process with at least 50% reinforcing fibres by weight and a matrix which impregnates the fibres through a bath, by spray injection or pressure characterised in that the surface of the reinforcing bar (8), after being hardened or essentially being hardened, is provided to be coated with a resin or adhesive whereby a pattern in the form of a plurality of protrusions is provided or imprinted in the adhesive on the surface of the bar (8) by means of a tool (5) with grooves or recesses (6) corresponding to the shape of the wanted shape of the protrusions, which is provided to be pressed against the surface of the bar until the adhesive is hardened or essentially hardened.

7. Equipment in accordance with claim 5, characterised in that the tool is provided on endless conveyors (9) on each side of the reinforcing bar (8) being produced, whereby the reinforcing bar is provided to be pulled between the conveyors (9) such that the tools (5) are pressed against the surface of the bar (8) by means of the conveyors.

8. Equipment in accordance with claims 5 and 6, characterised in that the tools are in the form of idividual segments (7) provided on the endless conveyor (9).

9. Equipment in accordance with claims 5 and 6, characterised in that The segments (7) are in the form of angularly shaped elements each with arms (10, 11) on which the tool segments (5) are provided.