MAT PILE FOR USE IN CONCRETE CONSTRUCTION PARTS, MAT AS A COMPONENT THEREOF, AND A CONCRETE CONSTRUCTION PART PROVIDED WITH A MAT PILE

Abstract: A mat pile is described that is intended for reinforcing concrete parts, this mat pile being constructed of mats (1-4) of hard-drawn soft steel wire formed by welding these wires. The hard-drawn soft steel wire has a tensile strength that is greater than or equal to 900 N/mm<2> before welding and a carbon content that is less than 0.2 weight %, and the mat pile in a construction part occupies 2-10 volume % of the construction part.

Description: AT PILE FOR USE IN CONCRETE CONSTRUCTION PARTS, MAT AS A COMPONENT THEREOF, AND A CONCRETE CONSTRUCTION PART PROVIDED WITH A MAT PILE. Field of the invention. The present invention relates in the first place to a mat pile for use as reinforcement in the forming of concrete construction parts in which the pile comprises a great number of steel wire mats. Background of the invention. Such mat piles are utilized in practice. The utilization of a pile of mats is a special form of fibre reinforcement for concrete, of which SIFCON and SIMCON are important representatives. SIFCON (Slurry Infiltrated Fibre Concrete) is described in an article by David R. Lankard in Concrete International, December, 1984, pp. 44-47. SIMCON (Slurry Infiltrated Mat Concrete) is described in an article by Lloyd E. Hackman et al. in Concrete International, December, 1992, pp. 53-56. SIFCON is a reinforced type of concrete in which metal fibres are placed in a form or mould and a fine-grained cement-based concrete paste is poured over the fibres, after which infiltration takes place by means of external vibration of the mould or form. Infiltration can also take place by pressing this paste into the mould through the bottom while vibrating the mould. SIMCON is another method for forming concrete reinforced with steel fibres, in which the metal fibres, which have a larger length/diameter ratio, are joined together to form a mat, as for example a non-woven type mat, which mats are used to form construction parts utilizing moulds or forms, as described above. SIFCON, although possessing goods properties, has the drawback that its fabrication requires that quite a number of operations be carried out on the construction site itself, in the course of which irregularities resulting from the presence of poor working conditions or inattention on the part of the workers cannot be totally excluded. SIMCON produces significantly more consistent results; the transport of the non-woven type of steel wire mats to the construction site is not without problems, however, and the loosely connected nature of the mats can lead to their becoming damaged, which then results in problems of irregularity. In the known mat pile, the filling consists basically of wire meshes that are stacked on top of one another. Summary of the invention. The applicant has carried out extensive testing of such a system, in which a large number of steel wire meshes were fabricated and then utilized as reinforcement in concrete. The properties were determined for each mat pile tested and it turned out, surprisingly enough, that splendid results were obtained when each of the mats was formed out of welded mesh made of hard-drawn soft steel wire. This result was very unexpected because it is generally assumed that soft steel wire that by means of drawing has been given a higher tensile strength as measured by mechanical testing will display a brittle fracture. Surprisingly, however, it turned out that when mats formed out of such hard-drawn soft steel wire were embedded in concrete, the brittle fracture did not occur in the concrete and, conversely, the concrete objects were found to possess markedly tough bending properties for which there is no conclusive explanation at the present time. In one attractive embodiment the mats in the mat pile are joined to one another to form an interconnected whole with the aid, for example, of linking means such as wires, staples, weld links or such like. Appropriately, hard-drawn soft steel wire has a carbon content of maximum 0.2 weight % and such hard-drawn soft steel wire has a tensile strength that is greater than or equal to 900N/mm2. With respect to hard-drawn soft wire, the extent of drawing is expressed in the so-called reduction. A diameter reduction from 5 mm to 1 mm as a result of drawing through drawing dies is called a reduction R of (5 2 - 1 2 ) /5 2 = 0.96 = 96%. The reduction R can vary, though the best results are obtained when one starts with a hard-drawn soft steel wire with a tensile strength that is greater than or equal to 900 N/mm 2 . A reduction of between 85 and 95% is a commonly used reduction; a reduction of around 95% is to be preferred. The invention also relates to a mat for use as a part of a mat pile in which the mat is a mat made of welded steel wire and the steel wire has properties such as indicated above for the mats in the mat pile. That is, the steel wire has a carbon content of maximum 0.2 weight % and the tensile strength is greater than or equal to 900 N/mm 2 . The invention also relates to a concrete construction part that comprises a mat pile as reinforcement, which construction part is characterized by the fact that the mat pile is a mat pile as indicated above according to the invention. With the aid of the above-described mat pile according to the invention and depending on the wire diameter and the mesh width of the mat, a filling of the construction part with steel wire of between 2 and 10 volume % can be obtained. In general, a filling of from 3 to 6, and by preference of from 4 to 5 volume % is used. Appropiately, the mat pile is formed of mats of welded mesh manufactured of hard-drawn soft steel wire having a tensile strength larger than or equal to 900 N/mm 2 , a diameter of 0.5 to 2.0 mm, mesh dimensions of between 5 x 5 and 30 x 30 mm, and with the number of mats in the pile being between 20 and 100. The number of mats is in general 4 to 10 mats per cm thickness of the concrete part, and by preference 6 to 8 mats per cm thickness. In one attractive embodiment, the construction part comprises a mat pile in which ± 1.0 mm wire is used, the mesh dimensions are ± 19 x 25 mm, the number of mats joined to one another is ± 30, and the volume percentage of wire in the construction part is ± 4.5. Brief description of the drawings. The invention will now be explained on the basis of the figures, in which: FIGURE 1 is a very schematic sketch of a mat pile according to the invention; FIGURES 2 - 5 are graphs obtained from a three-point bending test for beams fabricated with a mat pile according to the invention Description of the preferred embodiments of the invention. FIGURE 1 shows mats 1 through 4 made of welded mesh that is formed of hard-drawn soft steel wire, as discussed above. The four mats shown here are joined to one another with means 5 and 6 that are not discussed in greater detail. The linking means 5 and 6 can, for example, be wires that are connected on the outermost mats 1 and 4. Plates can also be present that are clipped to the wires and hold mats 1 to 4 pressed against one another under a certain degree of tension. The number of mats can of course be much greater than the four shown here, as for example between 20 and 100, although other numbers are also possible. As is schematically indicated, mats 1 to 4 are arranged in a staggered manner in relation to one another. The manner and degree of staggering can of course be chosen by the manufacturer on the basis of experience. This manner of stacking has two important advantages: 1) the wires of the mesh mats are shifted in relation to one another, which results in the wire distribution in the concrete mass being much more uniform; 2) by placing such mat piles next to and against one another, the problem of weak contiguous edge zones is for the most part avoided. A three-point bending test is utilized to measure the properties of the concrete construction parts fabricated with the aid of the mat pile according to the invention. Concrete construction parts (beams) filled with mat piles were made for the purpose of carrying out the tests. The construction parts had a length of 300 mm, a width of 100 mm and a height of 50 mm. The test was done using a three-point load in which the length of the beam is supported at two points 250 mm apart from one another and the load is applied on top in the middle between the support points. The cement composition used was: Cement cem 1 52.5 1000 kg/m 3 Quartz sand 0/0.7-M31 860 kg/m 3 Silica fume 100 kg/m 3 Rheobuild plasticizer 1100 30 kg/m 3 Water 330 kg/m 3 The dry materials were mixed for 2 minutes. Then water plus plasticizer were added and again mixed for 2 minutes. The crushing of lumps and further mixing took place for 2 minutes, after which it was once again mixed for 1.3 minutes using a screw driven by a drilling machine. The testing pieces were hardened and aged for predetermined periods of time, after which the beams were subjected to testing. The most significant measured values were: 1) the bending tensile strength fo (N/mm 2 ): this is the bending tensile strength in N/mm 2 derived from the force F 0 in Newtons at which the first crack appears. Fo = (F 0 . 1.3) / (b.h 2 .2) 2) The bending tensile strength fu (N/mm 2 ): this is the maximum bending tensile strength in N/mm 2 derived from the maximum force F u (in Newtons). The values F 0 and F u are taken from the diagrams in Fig.2 to Fig.5 (H1 to H4). In diagram H,: F 0 = 16500 N F U = 19500 N L = 250 mm (length between support points) B = 100 mm H = 50 mm F 0 = (16500.250.3) /100.50 2 .2) = 24.8 N/mm 2 Calculated in the same manner, fu = 29.3 N/mm 2 . The results described below were obtained when a mat pile according to the invention made of hard-drawn soft steel wire with a tensile strength of 1000 N/mm 2 was made with a wire volume in the construction part of 4.56%. The mat pile was constructed of 31 mats that had been manufactured from a wire of 1.00 mm diameter, while the mesh dimensions were 19 x 25 mm. The results were as follows: TABLE 1 The tough deformation and cracking character of the concrete beams reinforced with the mat pile according to the invention can be seen in the load deformation graphs H 1 through H 4 (Fig. 2-5).

Claims: CLAIMS 1. Mat pile for use as reinforcement in the forming of concrete construction parts whereby the pile comprises a great number of steel wire mats (1-4), characterized in that each of the mats (1-4) is formed from welded mesh made of hard-drawn soft steel wire. 2. Mat pile in accordance with Claim 1 , characterized in that the mats (1-4) in the mat pile are joined to one another to form an interconnected whole (5, 6). 3. Mat pile in accordance with Claims 1-2, characterized in that the hard-drawn soft steel wire has a carbon content of maximum 0.2 weight %. 4. Mat pile in accordance with Claims 1-3, characterized in that before the welding of the mesh the hard-drawn soft steel wire has a tensile strength that is greater than or equal to 900N/mm 2 . 5. Mat for use as part of a mat pile, characterized in that the mat is a mat (1 , 2, 3, 4) composed of welded steel wire and the steel wire possesses properties such as those indicated in Claims 1 , 3 and 4. 6. Concrete construction part comprising a mat pile as reinforcement, characterized in that the mat pile is a mat pile as indicated in one or more of Claims 1-4. 7. Construction part in accordance with Claim 6, characterized in that the construction part comprises a mat pile that forms 2-10 volume % of the construction part. 8. Construction part in accordance with Claim 7, characterized in that the mat pile occupies 3-6 volume % of the construction part. 9. Construction part in accordance with Claims 7-8, characterized in that the mat pile is formed of mutually interconnected mats (1-4) made of welded mesh that is constructed of hard-drawn soft steel wire with a tensile strength before welding of the mesh that is greater than or equal to 900N/mm 2 , a diameter of from 0.5-2.0 mm, mesh dimensions of between 5 x 5 and 30 x 30 mm, and with the number of mats in the pile being 20-100. 10. Construction part according to one or more of Claims 6-9, characterized in that the number of mats (1, 2, 3, 4) in the mat pile is 4-10 mats/cm thickness of the construction part, and by preference 6-8 mats/cm thickness of the construction part.

Inventors: NEMEGEER DIRK, NEMEGEER, DIRK
Applicants: BEKAERT SA NV, NEMEGEER DIRK, N.V. BEKAERT S.A., NEMEGEER, DIRK
Application year: 2000
Main classification: E04C5
IPC codes: E04C5