A kind of unbonded prestressed steel strand

Abstract

The present invention discloses an unbonded prestressed steel strand, comprising a plurality of prestressed steel strand bundles, a protective inner sleeve and a protective outer sleeve; the plurality of prestressed steel strand bundles are all arranged in the protective inner sleeve, and the gaps between the prestressed steel strand bundles are filled with an anti-corrosion layer; a plurality of flame retardant strips are evenly distributed along the longitudinal direction of the outer wall of the protective inner sleeve, and adjacent flame retardant strips are arranged closely in sequence without leaving any gaps; the cross section of the flame retardant strip is in a hemispherical shape; and a protective outer sleeve is provided on the outside of the flame retardant strip. The present invention arranges a plurality of flame retardant strips between the protective inner sleeve and the protective outer sleeve, the flame retardant strips can play a flame retardant role, the plurality of flame retardant strips are arranged closely in sequence, the adjacent flame retardant strips can play a role of isolating combustion, and because the cross section of the flame retardant strip is in a hemispherical shape, the flame retardant strips can better fit the outer wall surface of the protective inner sleeve, and at the same time increase the flame retardant area, thereby ensuring the flame retardant performance.

Description

Technical Field

[0001] The invention relates to the technical field of steel strands, and in particular to an unbonded prestressed steel strand. Background Art

[0002] Unbonded prestressed steel strands are mainly used in the post-tensioning construction of prestressed structures. The so-called unbonded means that after the prestressed steel strands are prestressed, there is no bonding force between the prestressed steel strands and the reserved channels in the concrete components, and they can slide. The prestress is completely transmitted by the anchors at both ends.

[0003] Usually, the structure of unbonded prestressed steel strands is composed of steel strand bundle + inner coating (grease or wax) + polyethylene sheath. Polyethylene, as a general-purpose plastic with excellent comprehensive performance, is widely used in the fields of automobiles, packaging, home appliances, electronic products, furniture, etc. However, polyethylene itself is a flammable material. Once a fire occurs, the overall safety of the unbonded prestressed steel strands is greatly reduced; some flame-retardant structural designs in the prior art are not only complex in structure, but also costly and have no value for large-scale application. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a non-bonded prestressed steel strand, which has a simple structure, low production cost and good flame retardant performance.

[0005] In order to solve the above technical problems, the technical solution of the present invention is:

[0006] A non-bonded prestressed steel strand comprises a plurality of prestressed steel strand bundles, a protective inner sleeve and a protective outer sleeve; the plurality of prestressed steel strand bundles are arranged in the protective inner sleeve, and the gaps between the prestressed steel strand bundles are filled with an anti-corrosion layer; a plurality of flame retardant strips are evenly distributed along the longitudinal direction of the outer wall of the protective inner sleeve, and adjacent flame retardant strips are arranged closely in sequence without leaving any gaps; the cross section of the flame retardant strip is hemispherical; and a protective outer sleeve is provided on the outside of the flame retardant strip.

[0007] Preferably, the flame retardant strip is made of a flame retardant foam material, and may be a foamed flame retardant silicone strip.

[0008] Preferably, the flame retardant strip is bonded to the outer side wall of the protective inner sleeve by flame retardant glue.

[0009] Preferably, there are 3-7 steel strand bundles.

[0010] Preferably, each of the steel strand bundles is formed by twisting 2, 3 or 7 steel wires.

[0011] Preferably, the protective inner sleeve and the protective outer sleeve are both made of low-smoke halogen-free flame-retardant polyolefin material.

[0012] Preferably, the protective inner sleeve is made of polyvinyl chloride material; and the protective outer sleeve is made of low-smoke halogen-free flame-retardant polyolefin material.

[0013] Preferably, the anti-corrosion layer is anti-corrosion grease or epoxy resin.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] (1) The unbonded prestressed steel strand in the present invention is provided with a protective inner sleeve and a protective outer sleeve on the outside of the prestressed steel strand bundle, and a plurality of flame retardant strips are arranged between the protective inner sleeve and the protective outer sleeve; through the above design, the flame retardant strip can play a flame retardant role, and at the same time, since the plurality of flame retardant strips are arranged closely in sequence, the adjacent flame retardant strips can play a role in isolating combustion, and since the cross section of the flame retardant strip is hemispherical, on the one hand, the flame retardant strip and the outer wall surface of the protective inner sleeve can be better fitted, and on the other hand, the design of the hemispherical cross section of the flame retardant strip increases the flame retardant area, thereby ensuring the flame retardant performance.

[0016] (2) The present invention has a simple structure, a wide range of raw material sources, low production costs, good flame retardant properties, and is suitable for popularization and use. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a structural schematic diagram of the present invention;

[0018] Figure 2 It is a schematic diagram of the structure of the flame retardant strip in the present invention.

[0019] In the figure, 1-prestressed steel strand bundle, 2-protective inner sleeve, 3-protective outer sleeve, 4-anti-corrosion layer, 5-flame retardant strip. DETAILED DESCRIPTION

[0020] The specific embodiments of the present invention are further described below in conjunction with the accompanying drawings. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0021] like Figure 1 , Figure 2As shown, a non-bonded prestressed steel strand comprises a plurality of prestressed steel strand bundles 1, a protective inner sleeve 2 and a protective outer sleeve 3; the plurality of prestressed steel strand bundles 1 are arranged in the protective inner sleeve 2, and an anti-corrosion layer 4 is filled between the gaps of the prestressed steel strand bundles 1; a plurality of flame retardant strips 5 are evenly distributed along the longitudinal direction of the outer wall of the protective inner sleeve 2, and the plurality of flame retardant strips 5 are arranged closely in sequence, that is, no gap is left between adjacent flame retardant strips 5; the cross-section of the flame retardant strip 5 is hemispherical; a protective outer sleeve 3 is provided on the outside of the flame retardant strip 5.

[0022] Preferably, the flame retardant strip 5 is made of flame retardant foam material, specifically flame retardant silicone foam strip. In addition to conventional flame retardant foam materials, the flame retardant foam material can preferably be ultra-light, ultra-strong, high flame retardant polypropylene foam material developed by the polymer division of Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences.

[0023] Preferably, the flame retardant strip 5 is bonded to the outer side wall of the protective inner sleeve 2 by flame retardant glue.

[0024] Preferably, there are 3-7 steel strand bundles 1.

[0025] Preferably, each of the steel strand bundles 1 is formed by twisting 2, 3 or 7 steel wires.

[0026] Preferably, the protective inner sleeve 2 and the protective outer sleeve 3 are both made of low-smoke halogen-free flame-retardant polyolefin material.

[0027] Preferably, the protective inner sleeve 2 is made of polyvinyl chloride material; the protective outer sleeve 3 is made of low-smoke halogen-free flame-retardant polyolefin material.

[0028] Preferably, the anti-corrosion layer 4 is anti-corrosion grease or epoxy resin.

[0029] This embodiment also provides a method for preparing the unbonded prestressed steel strand, which specifically comprises the following steps:

[0030] (1) First, a plurality of steel wires are twisted together to form a single steel strand bundle 1;

[0031] (2) Apply special grease or wax or spray epoxy resin to the outside of the individual steel strand bundles 1 in sequence;

[0032] (3) closing the single steel strand bundles 1 processed in the above steps, and forming a protective inner sleeve 2 on the outside of the closed steel strand bundles 1 by an extruder to cover the multiple steel strand bundles 1;

[0033] (4) The flame retardant strips 5 are sequentially bonded to the outer wall of the protective inner sleeve 2 by using flame retardant glue, and no gap is left between adjacent flame retardant strips during the bonding process;

[0034] (5) The outside of the bonded flame retardant strip 5 is extruded again by an extruder to form a protective jacket 3, thereby completing the overall preparation process.

[0035] The embodiments of the present invention are described in detail above with reference to the accompanying drawings, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. An unbonded prestressed steel strand, characterized in that: The invention comprises a plurality of prestressed steel strand bundles (1), a protective inner sleeve (2) and a protective outer sleeve (3); the plurality of prestressed steel strand bundles (1) are arranged in the protective inner sleeve (2), and the gaps between the prestressed steel strand bundles (1) are filled with an anti-corrosion layer (4); a plurality of flame retardant strips (5) are evenly distributed along the longitudinal direction of the outer wall of the protective inner sleeve (2), and adjacent flame retardant strips (5) are arranged closely in sequence without leaving any gap; the cross section of the flame retardant strip (5) is in a hemispherical shape; a protective outer sleeve (3) is provided on the outside of the flame retardant strip (5); the flame retardant strip (5) is made of a flame retardant foam material; the flame retardant strip (5) is bonded to the outer wall of the protective inner sleeve (2) by flame retardant glue; there are 3 to 7 steel strand bundles (1); the protective inner sleeve (2) and the protective outer sleeve (3) are both made of low-smoke halogen-free flame retardant polyolefin material; the anti-corrosion layer (4) is anti-corrosion grease or epoxy resin.

2. The unbonded prestressed steel strand according to claim 1, characterized in that: Each of the steel strand bundles (1) is formed by twisting two, three or seven steel wires.

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