WO1998003276A1

WO1998003276A1 - Concrete products

Info

Publication number: WO1998003276A1
Application number: PCT/GB1997/001942
Authority: WO
Inventors: Nijad Ibrahim Fattuhi; Leslie Arthur Clark
Original assignee: The University Of Birmingham
Priority date: 1996-07-19
Filing date: 1997-07-17
Publication date: 1998-01-29
Also published as: GB9615161D0

Abstract

Concrete products are reinforced by incorporating cut strips (42) of waste tyre material containing wire and/or textile cord reinforcement material bonded to the rubber of the tyre. This is done by disposing the cut strips (42) within a mould or formwork (40), introducing a settable concrete mix into the mould or formwork (40) so as to surround the strips (42) at least partially, and allowing the concrete mix to set to form a concrete product containing said cut strips (42) as reinforcement.

Description

CONCRETE PRODUCTS

This invention relates to products formed from concrete and is more particularly concerned with reinforced concrete products incorporating tyre materials. The term "concrete" as used herein includes cementitious material which may contain (a) aggregate having a particle size of more than about 10 mm, (b) aggregate having a particle size of less than about 10 mm (often referred to as "mortar"), or (c) no aggregate (often referred to as "grout"). The term "concrete" as used in the description and claims is to be construed accordingly.

There have been many previous proposals to produce concrete products containing waste tyre material because such waste tyre material is readily available and the disposal of tyres represents a considerable problem. For example, "Use of Ground Rubber Tyres in Portland Cement Concrete" by Ali, N.A. et al Proceedings of International Conference Concrete 2000, University of Dundee (UK) 1993, pp 379-390 proposes the incorporation of ground tyre rubber into concrete to provide a low or zero shrink fill material for back-filling holes in pavements etc. Such proposal involves tearing scrap tyre rubber apart, size-reducing it and micro-milling the rubber to provide a very fine ground particle wherein the tyre steel or fibre may or may not be present. Similar proposals are also made by H. Rostami, H. et al in "Use of Recycled Rubber Tyres in Concrete", Proceedings of International Conference Concrete 2000, University of Dundee (UK) 1993, pp 391-399.

The reinforcement of concrete using pulverised tyres is disclosed in JP 5205962, whilst the use of steel wires from waste tyres in reinforced concrete has been proposed in DE 4104929 and DE 2625810, for example.

The disadvantage of these proposals is that a considerable amount of effort and cost is put into separating the required tyre components before they can be used for the intended application in concrete. In addition, including only rubber in the concrete mix reduces the mechanical properties of the concrete, and including only chopped steel wire provides discontinuous rather than continuous reinforcement.

It has also been previously proposed to use whole tyres which are filled with or encased in concrete, but this does not lend itself to the wide variety of concrete products which can be produced by the present invention.

It is an object of the present invention to obviate or mitigate this disadvantage.

According to one aspect of the present invention, there is provided a concrete product which is reinforced by cut strips of tyre material wherein the cut strips contain wire and/or textile cord reinforcement bonded to the rubber of the tyre.

According to another aspect of the present invention, there is provided a method of manufacturing a concrete product comprising the steps of disposing cut strips of tyre material containing wire and/or textile cord reinforcement material bonded to the rubber of the tyre within a mould or formwork, introducing a settable concrete mix into the mould or formwork so as to surround the strips at least partially, and allowing the concrete mix to set to form a concrete product containing said cut strips as reinforcement.

Adjacent cut strips may be interconnected using rods, nails or other connection means like of which at least some may be employed to retain the strips in the desired positions in the mould or formwork before the settable concrete mix is introduced into the mould. The use of rod, nails, pins or the like can also help in improving the mechanical bond between the strips. The rods, nails or the like may be formed of metal, eg. steel or of plastics material.

In one convenient embodiment, strips are mutually arranged so as to provide a mesh-type reinforcement with intersecting strips being secured together, for example by use of rods, nails, pins or the like. Strips formed from the tread of a tyre are preferably up to 50mm in width and may be of any desired length to suit the particular concrete product being manufactured.

When using strips defined by tyre beads, one or more of the strips may be defined by the whole or part of the tyre bead and thus may be of annular or part shape. The resulting rings and/or part rings may be tied together to form various reinforcing patterns. This is considered to be particularly useful in the manufacture of concrete products in the form of concrete slabs or circular shafts.

If broad strips of tyre are produced from the side walls, holes may be punched in the strips to improve the mechanical bond with the concrete. Complete side walls and side walls cut to various lengths and widths may be used as desired depending upon the particular product to be manufactured.

The strips may be cut from scrap car tyre or truck tyres and may be cut using a band saw, an electrically heated cutting element, by pressing or stamping or by any other appropriate technique.

Strips from radial tyres may be used in small beams and slabs, for example.

There are several advantages to be gained from using strips cut from tyres. Besides environmental factors and low cost, the strips are durable because the metal reinforcement therein is protected to a large extent by the rubber of the tyre. Thus, the present invention can be of considerable benefit to concrete products in a marine environment. They are also of considerable benefit in concrete products which are designed to undergo considerable deformations such as those which are subjected to blast or impact loadings.

The present invention will now be described, in further detail, with reference to the accompanying drawings, in which:-

Figures 1 (a) to 1 (f) are schematic diagrams illustrating the manner in which tyre strips can be held together in spaced apart relationship and supported within a mould for the manufacture of reinforced concrete products according to the method of the present invention, Figures 2(a) and 2(b) are schematic side and cross-sectional views of a metal rod-reinforced concrete beam which is not in accordance with the present invention but which is provided for comparison purposes,

Figures 3 and 4 are schematic cross-sections showing the arrangement of reinforcement based on Figures 1 (d) to 1 (f) and Figures 1 (a) to 1 (c) , respectively, in first and second embodiments of concrete beams according to the present invention,

Figure 5 is a schematic side elevation showing the arrangement of reinforcing strips in a third embodiment of concrete beam according to the present invention,

Figure 6 is a schematic cross-sectional view showing the strip arrangement in a fifth embodiment of concrete beam according to the present invention,

Figures 7(a) and 7(b) are respective plan and side views showing the arrangement of strips in a mould for the manufacture of a first embodiment of concrete slab according to the present invention,

Figure 7(c) is a view similar to Figure 7(b) showing a modified arrangement of strips,

Figure 8 is a plan view similar to Figure 7(a) showing an alternative arrangement of strips for a second embodiment of concrete slab according to the present invention, Figure 9 is a graph showing the Load-Deflection relationship for the first embodiment of slab produced from the mould illustrated in Figure 7(a) and 7(b), and

Figure 10 is a graph similar to Figure 9 but in respect of the second embodiment of slab incorporating reinforcement strips as illustrated in Figure 8.

BEAM TESTS Preparation of Mixes

Two concrete mixes were used to make 100 x 100 x 500 mm beams. In order to shorten the time between making and testing beams, Kaffir ' D' plaster or high alumina cement was used as binder. The weight ratio of binder: Midland sand (medium): crushed Midland gravel of 10 mm maximum size: drinking tap water used was 1 .00 : 1 .41 : 2.82 : 0.44.

Preparation of mixes

Each mix prepared was enough to make one beam. The dry materials placed in a galvanised steel pan were mixed uniformly by hand using trowels. Then water was added and mixing continued until a uniform mix was achieved.

To prepare rubber reinforcements, various strips of either tread or bead were cut from radial tyres to desired lengths and were placed in the moulds. Tyre details, are described in Table 1 hereinafter. To position strips in moulds and achieve the required concrete cover and alignment, spacers made from steel rods were used. The rods were cut to length and bent to form various shapes as required. Then spacers were pushed into rubber strips and the strips positioned in the moulds.

In Figures 1 (a) to 1 (c), a pair of strips 10 are held with their cut side edges horizontally disposed in the desired horizontally spaced disposition by means of a plurality of horizontal linear rods 12 (only one shown). Downwardly cranked rods 14 are engaged in the respective strips 10. The horizontal rods 12 also serve to retain the strips 10 at the desired spacing from side wall of beam mould 16, whilst the cranked rods 14 hold the strips 10 at the desired spacing above the bottom of the beam mould 16.

In Figures 1 (d) to 1 (0, strips 10 are held with their cut side edges vertically disposed in the desired mutual dispositions by a series of inverted U-shaped rods 18 and are also pierced by cranked rods 20. The resultant beams 22 and 23 are as illustrated in Figures 3 and 4 respectively, the reinforcement strips 10 of Figure 3 corresponding to Figures 1 (d) to 1 (f) and the arrangement of strips 10 in Figure 4 corresponding to Figures 1 (a) to 1 (c). In Figures 3 and 4, the various rods 12, 14, 18 and 20 are present but are not actually illustrated.

In Figures 2(a) and (b), a beam 24 is illustrated which, for comparison purposes, has been reinforced with two 8mm diameter steel bars 26 which extend longitudinally of the beam 24 and which have upwardly bend ends as illustrated in Figure 2(a).

In Figure 5, there is illustrated a beam 28 which has been reinforced with two pairs of overlapping lengths of tyre bead 30. In Figure 6, there is illustrated a beam 32 wherein a single longitudinally extending strip 10 is provided in a non-idealised position adjacent to the top of the beam rather than adjacent to the bottom of the beam.

During manufacture of the beams, concrete was cast in moulds in two or more layers and compacted on a vibrating table. Then the filled moulds were covered with polyethylene sheets and left to cure in the laboratory until demoulding about 24 hours later. All beams were tested on the day of demoulding. Table 2 hereinafter shows beam details.

Testing Arrangement

A Denison Universal Testing Machine of 500 kN capacity was used for loading the beams. All beams were loaded in flexure at their third points (four-point bending) over a span of 406 mm.

Test Results

Table 3 hereinafter shows results of flexure tests carried out on the beams. All beams showed significant increase in capacities beyond first crack loads. The highest ratio of ultimate to first crack load of 3.12 was that obtained from beam 24 which was reinforced with deformed steel bars. Beams 22, 23, 28 and 32 produced ratios of ultimate to first crack loads which ranged from 2.16 to 2.49. The lowest ratio was that for beam 32 where the single rubber strip 10 used rose unintentionally towards the compression zone (spacers were not used) whilst vibrating the fresh concrete. However, these results indicate that a considerable improvement in flexural strength of concrete can be obtained when using and appropriately positioning various tyre strips in beams. Unlike beam 24 which failed by shear cracking, beams 22, 23, 28 and 32 tended to fail in flexure which is a desirable mode of failure.

It is estimated that a 30 mm width rubber strip contains approximately 9.2 mm² of metal wire. However, these wires are not aligned in the direction of the principal stress in beams. To obtain a comparative idea of the amount of steel used, it is estimated that beam 22 contained about 18% of the steel reinforcement used in beam 24.

Table 1 Tyre Details

Property Specification

Type Uniroyal Rallye 340/60 - Radial Size 185/60 HR14

Sidewall Plies Rayon 2 Tread Area Plies Steel 2 + Nylon 2 + Rayon 2 Max. Load Rating 475 kg

Table 2 Beam Details

Characteristic Beam No

24 22 23 28 32

Binder High High High High Kaffir 'D'

Alumina Alumina Alumina Alumina

Cement Cement Cement Cement

Reinforcement 2 No 8 mm 2 No tread 2 No tread 4 No bead 1 No (see Figs. 2 to 6) deformed strips each strips each strips tread strip steel bars 30 mm in 45 mm in 45 mm width width wide

Average cover (mm) to: tension face 8 3 5 Varied 45 (4mm mm.) side 20 10 20 20 43 Table 3 Beam Test Results

Property Beam No

24 22 23 28 32

Cracking Load (kN) 26.00 10.22 1 1.84 13.00 4.33

Ultimate Load (kN) 81.1 25.4 27.9 28.9 9.35

Load Ratio Ultimate 3.12 2.49 2.36 2.22 2.16

Cracking

Type of Cracking Flexural Flexural Flexural & Flexural Flexural

& Shear Shear & Shear

Mode of Failure Shear Flexure Shear- Flexure Shear-

Flexure Flexure

SLAB TESTS

Preparation of Mixes

The concrete mix used for preparing slabs was similar to that for beams. However, ordinary Portland cement was used as the binder.

Preparation of Slabs 1 and 2

Concrete was prepared in a similar manner to that described for beams. A mould 40 (600 x 600 x 45 mm) with a steel base and timber sides was used for making the slabs (see Figures 7(a), 7(b) and 8).

To prepare the reinforcement for Slab 1 , strips 42 of tyre tread 25-30 mm in width were cut to the required lengths and interwoven to form a mesh, as shown in Figures 7(a) and 7(b). The average spacing between strips was about 120 mm. Steel nails 44 were used to join the strips 42 and also to provide a concrete cover of about 10 mm to the base of the slab. In order to reduce the mesh thickness at the joints, some of the rubber was removed from the strips 42. An alternative arrangement of the strips 42 is shown in Figure 7(c) where one set overlies the other set instead of the sets being interwoven.

To prepare for the reinforcement for Slab 2, various strips 46 of tyre bead and a complete tyre sidewall strip 48 were used as shown in Figure 8. The sidewall strip 48 contained no steel reinforcement, and holes 50 were punched through it to improve the mechanical bond with concrete. The various strips 46 and 48 were not provided with concrete cover to the base of the slab.

Concrete was cast continuously in the mould while compacting on a vibrating table. The mould was covered with polyethylene sheet until demoulding about 24 hours later. Then the slabs were left in a humidity room until they were tested. Slabs 1 and 2 were tested at the ages of 101 and 98 days, respectively.

Testing Arrangement

A Mand testing machine provided with a 400 kN loading jack was used to test the two slabs. The load was applied at the centre of each slab via a spherical seat with a loading plate 223 mm in diameter. Each slab was supported on its four sides on a steel frame via rollers and steel plates over a span of 500 mm in (each direction). A dial gauge with accuracy of 0.01 mm was used to measure the central deflections of each slab. Test results

Test results showed that there was little difference in the ultimate loads carried by the two slabs. The maximum loads supported by slabs 1 and 2 were 1 1.0 and 10.0 kN, respectively. No observations as to when first crack loads occurred were made. However, load-deflection measurements shown in Figures 9 and 10 indicate that first crack loads were close to ultimate loads. The main reason behind this is due to the relatively small amount of reinforcement used in the slabs. The load- deflection relationships also show that the slabs exhibited considerable toughness, where they continued to carry substantial loads after undergoing large deformations.

Potential Uses

It is considered that concrete products according to the present invention have potential application in the following areas:-

1. In coastal protection such as manufacture of breakwaters, defence walls and ground covering.

2. Where improved resistance to impact or explosion is required such as in the manufacture of crash barriers, bollards, buffers, bunkers etc.

3. Manufacture of concrete fencing panels, small beams and sills, and paving slabs. 4. In the construction of lightly loaded foundations where they are subjected to aggressive soil conditions, impact or vibration.

Rubber strips can also be partially embedded into concrete surfaces, such as in paving slabs, concrete floors, crash barriers, bollards, etc. to soften tread or dampen any impact.

Claims

1. A method of manufacturing a concrete (as defined herein) product comprising the steps of disposing cut strips of tyre material containing wire and/or textile cord reinforcement material bonded to the rubber of the tyre within a mould or formwork, introducing a settable concrete mix into the mould or formwork so as to surround the strips at least partially, and allowing the concrete mix to set to form a concrete product containing said cut strips as reinforcement.

2. A method as claimed in claim 1 , wherein adjacent cut strips are interconnected using rods, nails or other connecting means before the settable concrete mix is introduced into the mould or formwork.

3. A method as claimed in claim 1 or 2, wherein at least some of the cut strips are mutually arranged so as to provide a mesh-type reinforcement with intersecting strips being secured together.

5. A method as claimed in any preceding claim, wherein at least one of the cut strips is formed from the tread of a tyre and has a width of up to 50mm.

6. A method as claimed in any preceding claim, wherein at least one of the strips is formed from a tyre bead and is of annular or part- annular shape.

7. A method as claimed in claim 6, wherein a plurality of annular or part-annular cut strips are tied together to form a reinforcing pattern.

8. A method as claimed in any preceding claim, wherein at least one of the cut strips is formed from a tyre side wall and has a plurality of holes therethrough.

9. A concrete (as defined herein) product which is reinforced by cut strips of tyre material wherein the cut strips contain wire and/or textile cord reinforcement bonded to the rubber of the tyre.