Prestressed concrete for non-primary structural members

Abstract

To provide a prestressed concrete which can be used for non-primary structural members such as general building members by using a chemical stress induced by an expansive material and a mechanical stress induced by a rust-resistant wire together and achieving reduction in weight and suppression of cracking. A prestressed concrete for non-primary structural members is characterized in that a mechanical stress induced by a tensional material and a chemical stress induced by an expansive material for a concrete are introduced and that the tensional material is a rust-resistant continuous fiber reinforcing wire.

Claims

1. A prestressed concrete for non-primary structural members, obtained by introducing a prestress into a concrete for non-primary structural members, wherein a mechanical stress induced by a tensional material and a chemical stress induced by an expansive material for a concrete are introduced simultaneously into the concrete, and the tensional material is a rust-resistant wire, the expansive material for a concrete is a mixture of one or more kinds selected from a lime-based expansive material, an ettringite-lime composite-based expansive material, an iron powder-based expansive material, a shale-based expansive material, and a silica-based expansive material, the rust-resistant wire of the tensional material has a wire diameter of 15 mm or less and a tensile load of 150 kN or less, and the concrete has a thickness of 50 mm or less.

2. The prestressed concrete for non-primary structural members according to claim 1, wherein the tensional material is a continuous fiber reinforcing wire.

3. The prestressed concrete for non-primary structural according to claim 2, wherein the continuous fiber reinforcing wire is a reinforcing fiber wire of one or more kinds of fibers selected from an aramid fiber, a carbon fiber, a glass fiber, and a poly-p-phenylenebenzobisoxazole fiber.

4. The prestressed concrete for non-primary structural members according to claim 1, wherein the tensional material is a wire formed of a shape memory alloy.

5. The prestressed concrete for non-primary structural members according to claim 1, wherein a mesh sheet formed of a fiber reinforced resin is used.

6. The prestressed concrete for non-primary structural members according to claim 1, wherein a porous artificial lightweight material is used.

7. The prestressed concrete for non-primary structural members according to claim 1, wherein a discontinuous reinforcing material is used.

8. The prestressed concrete for non-primary structural members according to claim 7, wherein the discontinuous reinforcing material is a reinforcing fiber material formed of one or more kinds of fibers selected from a carbon fiber, a glass fiber, a resin fiber, and a shape memory alloy material.

9. The prestressed concrete for non-primary structural members according to claim 1, wherein a pigment is mixed.

10. The prestressed concrete for non-primary structural members according to claim 1, wherein any irregularities are formed on a surface thereof using a soft form.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIGS. 1(A) to 1(C) are explanatory views of a conventional pretension bed (manufacturing apparatus).

(2) FIG. 2 is a schematic view illustrating arrangement of a tensional material in a prestress concrete according to the present invention.

(3) FIGS. 3(1) to 3(3) are schematic views of a bending test body in the prestress concrete according to the present invention.

(4) FIG. 4 is a schematic diagram illustrating a bending test situation of the prestress concrete test body according to the present invention.

(5) FIG. 5 is a diagram illustrating a load position of the prestress concrete test body according to the present invention.

(6) FIG. 6 is a diagram illustrating a bending test result of three prestress concrete test bodies with holes according to the present invention.

(7) FIG. 7 is a diagram illustrating a bending test result of three prestress concrete test bodies without holes according to the present invention.

(8) FIG. 8-1 is a diagram illustrating situations in CASE-1 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

(9) FIG. 8-2 is a diagram illustrating situations in CASE-2 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

(10) FIG. 8-3 is a diagram illustrating situations in CASE-3 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

(11) FIG. 8-4 is a diagram illustrating situations in CASE-4 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

(12) FIG. 8-5 is a diagram illustrating situations in CASE-5 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

(13) FIG. 8-6 is a diagram illustrating situations in CASE-6 at the time of cracking and at the time of unloading in a bending test of the prestress concrete test body according to the present invention.

DESCRIPTION OF EMBODIMENTS

(14) Embodiments of the present invention will be described with reference to the drawings.

(15) First, FIGS. 1(A) to 1(C) illustrate a method for introducing a mechanical prestress by a conventional pretension method.

(16) FIGS. 1(A) to 1(C) are explanatory views of a pretension bed (manufacturing apparatus).

(17) These illustrate an example in which a tension of 50 tons (490 kN) is introduced using a PC steel strand wire of φ26 mm as a tensional material.

(18) In this conventional example, as illustrated in FIGS. 1(A) to 1(C), three prestressed concrete members are simultaneously manufactured in a longitudinal direction on a pretension bed (manufacturing apparatus 1) in a long line system.

(19) As illustrated in FIG. 1(A), the PC steel strand wire is stretched between reaction force bases, and is tensed by a jack on a left side with a tensile load of 50 tons (490 kN) to add a prestress force.

(20) Subsequently, as illustrated in FIG. 1(B), a lattice reinforcement (reinforcement) and a form are assembled while the PC steel strand wire is tensed, and a concrete is poured and cured.

(21) When predetermined concrete strength is obtained, as illustrated in FIG. 1(C), the tension jack is gradually released, the PC steel strand wire is cut, and the tension is transferred to the prestressed concrete member.

(22) A conventional prestressed concrete is manufactured in this way.

(23) A prestressed concrete for structural materials is manufactured in this conventional example.

(24) The present invention provides a prestressed concrete for non-primary structural members which can be used for general buildings.

(25) A method for introducing a mechanical prestress can be similar to the conventional example (FIGS. 1(A) to 1(C)).

(26) The prestressed concrete according to the present invention is achieved by a novel composition of a concrete, a tensional material, and a tensile load.

(27) Formulation of a concrete is indicated below. (unit kg/m3)

(28) cement: 543

(29) admixture: fly ash: 63

(30) admixture: expansive material: 20

(31) water: 175

(32) fine aggregate: 783

(33) coarse aggregate: 810

(34) admixture: water reducing agent: 7.50

(35) water-binder ratio: 28%

(36) A mixing ratio of an expansive agent is 20 kg/m3 as described above.

(37) As a tensional material, a strand wire of a carbon fiber reinforced polymer (CFRP) material having a diameter of 12.5 mm was used.

(38) A prestressed concrete having a size of 3 m×2.4 m×36 mm was used as one body, and five wires of the tensional materials were disposed at an interval of 500 mm in a lateral direction.

(39) FIG. 2 illustrates an arrangement view of a tensional material.

(40) A thickness T of a prestressed concrete 1 was 36 mm, and a tensional material 2 of φ12.5 mm was disposed in a central portion of the plate thickness.

(41) A lattice reinforcement 3 was disposed on an upper surface of the tensional material. A covering thickness was about 7 mm.

(42) In the above concrete composition, the tensional material was disposed, and a tensile load of 18 kN was introduced into each wire of the tensional material.

(43) After curing was performed about for 24 hours, tension was released.

(44) After a prestressed concrete was manufactured, compressive strength was 60 MPa or more, satisfying reference strength.

(45) The prestressed concrete of the present invention has a plate thickness of 36 mm. A conventional prestressed concrete using a steel tensional material (φ12.5 mm) needs to have a covering thickness of about 30 mm considering a problem such as rust, and therefore needs to have a larger plate thickness than the prestressed concrete of the present invention by a difference in covering thickness (30 mm−7 mm), that is, about 23 mm on one side.

(46) The prestressed concrete according to the present invention had a weight of 648 kg.

(47) A conventional prestressed concrete using a steel tensional material has a plate thickness of 82 mm considering a covering thickness. When calculation was performed using an approximate weight of a general reinforced concrete (calculated using 2.5 tons per 1 m3), about 1476 kg was obtained, indicating reduction of 50% or more in weight.

(48) As for cracking, cracking occurred when one person was placed on a central portion of the prestressed concrete plate according to the present invention and jumped about 30 cm to apply a shock with a body weight of 70 kg while fulcrums were put on lower parts of four corners of the prestressed concrete plate and the prestressed concrete plate was placed horizontally. However, when the load was removed, the cracks were completely closed by a crimping effect due to a prestress, and water leakage was not observed at all when a water leakage test was performed.

(49) [Examples of Bending Test]

(50) Test for Comparison Between Mechanical Stress and Chemical Stress Using Bending Test

(51) Six test bodies 10 were subjected to a bending test according to JISA1414 while conditions of a mechanical stress induced by a continuous fiber reinforcing wire (hereinafter, abbreviated as MS) and a chemical stress induced by an expansive material for a concrete (hereinafter, abbreviated as CS) were changed.

(52) A composition of the concrete was similar to the above case in FIG. 2.

(53) Each of the test bodies 10 had a size of length (L) 2 m×width (W) 1 m×thickness (t) 38 mm. As illustrated in FIG. 3(1), each of the test bodies 10 was a concrete thin plate, and three carbon fiber wires (CFRP) of φ7.5 mm were embedded therein. The carbon fiber wires (CFRP) are indicated by a broken line, and spine reinforcement (SR) is indicated by a dashed line. As illustrated in FIG. 3(2), three test bodies had no hole. As illustrated in FIG. 3(3), the other three test bodies had two through holes (large) 4: φ150 mm and two through holes (small) 5: φ75 mm around the center.

(54) Stress conditions of the six test bodies are as follows.

(55) (CASE-1) with MS+with CS: having no hole

(56) (CASE-2) with MS+without CS: having no hole

(57) (CASE-3) without MS+with CS: having no hole

(58) (CASE-4) with MS+with CS: having a hole

(59) (CASE-5) with MS+without CS: having a hole

(60) (CASE-6) without MS+with CS: having a hole

(61) with MS: with a mechanical stress load induced by a continuous fiber reinforcing wire

(62) without MS: without a mechanical stress load induced by a continuous fiber reinforcing wire

(63) with CS: with an expansive agent

(64) without CS: without an expansive agent

(65) mechanical stress (MS) condition: continuous fiber reinforcing wire: carbon fiber wire: φ7.5 mm

(66) Three continuous fiber reinforcing wires were used in a longitudinal direction (interval of 250 mm) (refer to FIGS. 3(1) to 3(3)) .

(67) tensile load: 20 kN per continuous fiber reinforcing wire

(68) chemical stress (CS) condition: mixing ratio of an expansive agent: 20 kg/m3

(69) bending test condition: performed with a two point-concentrated load using a bending test apparatus illustrated in FIG. 4.

(70) Deflection was measured using a displacement meter 11.

(71) span (distance between fulcrums: SL): 1,000 mm (refer to FIG. 5)

(72) distance between internal load points (points to which a force is applied) (PL): 500 mm (refer to FIG. 5)

(73) [Test Result]

(74) FIGS. 6 and 7 are diagrams illustrating a relationship between a load and deflection.

(75) FIG. 6 illustrates results of CASE-1 to CASE-3.

(76) FIG. 6 illustrates a comparison result among three types each having no hole,

(77) (CASE-1) with MS+with CS,

(78) (CASE-2) with MS+without CS, and

(79) (CASE-3) without MS+without CS.

(80) FIG. 7 illustrates results of CASE-4 to CASE-6.

(81) FIG. 7 illustrates a comparison result among three types each having a hole,

(82) (CASE-4) with MS+with CS,

(83) (CASE-5) with MS+without CS, and

(84) (CASE-6) without MS+without CS.

(85) FIGS. 8-1 to 8-6 are photographs comparing situations at the time of cracking and at the time of unloading in bending tests of CASE-1 to CASE-6.

(86) In CASE3 (FIG. 8-3) and CASE6 (FIG. 8-6) into which only a chemical stress had been introduced, cracks remained even at the time of unloading after fracture.

(87) On the other hand, in CASE1 (FIG. 8-1), CASE2 (FIG. 8-2), CASE4 (FIG. 8-4), and CASE5 (FIG. 8-5) into which a mechanical stress had been introduced, cracks returned to an original state and were not confirmed at the time of unloading after fracture.

(88) The results of the bending test indicate the following.

(89) TABLE-US-00001 cracking situation fracture residual after fracture load deflection (unloading) CASE-1 20.3 0.63 0.05 mm or less CASE-2 19.0 1.05 0.07 mm CASE-3 14.2 2.73 0.40 mm or more CASE-4 14.2 0.82 0.05 mm or less CASE-5 12.6 1.36 0.05 mm or less CASE-6 11.8 2.30 0.40 mm or more

(90) Three days after the bending test, a water leakage test of a cracked part was performed. A problem of water leakage was not observed in any cracked part.

(91) This indicates that even when cracking occurs in a carbon fiber material having a tensional material embedded, cracks are removed by a restoring action at the time of unloading and a risk of water leakage disappears. Particularly when a mechanical stress was introduced into the tensional material, residual deflection was hardly observed, and a concrete was restored to such an extent that no crack could be confirmed.

(92) The above test results indicate that the cases into which both a mechanical stress and a chemical stress have been introduced (CASE-1, CASE-4) have the highest fracture load and have the highest strength. In these cases, at the time of unloading after fracture, a crack is crimped by the mechanical stress and could be hardly confirmed, and there was no problem in a water leakage test at all.

(93) In the cases only with a mechanical stress (CASE-2, CASE-4), a fracture load was higher than a case only with a chemical stress, and was lower than a case with a composite stress of the mechanical stress and the chemical stress. At the time of unloading after fracture, a crack is crimped by the mechanical stress and could be hardly confirmed, and there was no problem in a water leakage test at all.

(94) The cases only with a chemical stress (CASE-3, CASE-6) indicate a low fracture load and the lowest strength. In these cases, a crack remained as it was although having a slightly smaller size after fracture, but water leakage was not confirmed in a water leakage test.

(95) By the above results, it has been found that a case into which a composite stress of a mechanical stress and a chemical stress has been introduced has higher strength than a case into which a mechanical stress or a chemical stress is introduced singly.

(96) It is considered that this is because a compression action by a mechanical stress and an expansion action by a chemical stress act synergistically to a concrete to enhance strength.

(97) Results of the test bodies each having no hole (CASE-1 to CASE-3) and test bodies each having a hole (CASE-4 to CASE-6) indicate that in test bodies each having no hole (FIG. 6), CASE-1 (MS+CS) and CASE-2 (MS) have a high fracture load to approximately the same extent and CASE-3 (CS) has a slightly lower fracture load by comparison between the two graphs (FIGS. 6 and 7).

(98) On the other hand, in the test bodies each having a hole (FIG. 7), CASE-4 (MS+CS) has a higher fracture load, and CASE-5 (MS) and CASE-6 (CS) have a low fracture load to approximately the same extent.

(99) This is a particularly remarkable result. A case of no hole in FIG. 6 exhibits a large effect of a mechanical stress. CASE-1 (MS+CS) and CASE-2 (MS) into which a mechanical stress has been introduced have high strength. CASE-3 (CS) into which a mechanical stress has not been introduced has low strength. However, in a case where there is partially a large change in shape such as a cutout portion or an opening, like a hole illustrated in FIG. 7, it is indicated that not only a mechanical stress but also a chemical stress has a large effect on strength.

(100) Conventionally, a high mechanical stress of 150 kN or more has been introduced into a prestressed concrete as a primary structural member requiring high strength. Unlike the present invention, a case of introducing a low mechanical stress has not been studied at all, and such a test has not been performed at all. In addition, combined use of a chemical stress for increasing strength has not been considered at all. It has been judged that there is no effect by the combined use.

(101) As a conventional common sense, it has been believed that a case of introducing a mechanical stress hardly exhibits an effect even by combined use of a chemical stress. However, by this test, it has been confirmed that a low mechanical stress state of 150 kN or less at a plate thickness of 50 mm or less is effective for increasing strength by combined use of a chemical stress.

(102) In particular, it has been confirmed that combination of a mechanical stress and a chemical stress is very effective when a prestressed concrete is used as a plate material for non-primary structures, partially having an opening, a cutout portion, or a hole, or having a high design property characterized by an irregular shape on a surface.

(103) As described above, the prestressed concrete of the present invention has a significant effect of reduction in thickness, reduction in weight, and suppression of cracking, can be applied to an outer wall, a partition wall, a floorboard, a furniture material, or the like as a general building member (except for a primary structural member), and is an excellent concrete plate having a completely new design property due to a lightweight thin plate and having a potential of a design property.

REFERENCE SIGNS LIST

(104) 1 prestressed concrete 2 tensional material 3 lattice reinforcement 4 hole (large) 5 hole (small) 10 test body 11 displacement meter 12 crack T plate thickness of concrete L length of test body W width of test body t thickness of test body CFRP carbon fiber wire SR spine reinforcement SL span (distance between fulcrums) PL distance between internal load points (points to which a force is applied)