PRESTRESSED CONCRETE

Abstract

An object to provide a prestressed concrete that can be widely used for general building members, in which a chemical stress induced by an expansive material and a mechanical stress induced by a continuous fiber reinforcing wire are simultaneously used together, and due to a synergistic effect of the mechanical stress and the chemical stress, the strength is increased, the reduction in weight, reduction in thickness, and suppression of cracking are achieved, and the degree of freedom in design increased. To provide a prestressed concrete characterized in that, in a concrete into which a prestress is introduced, 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, the tensional material is a continuous fiber reinforcing wire, the expansive material for a concrete is contained in an amount of 5 to 30 kg/m3, and aluminum oxide contained in an amount of 0.2 to 2.0% by weight to the expansive material.

Claims

1. A prestressed concrete, being a concrete into which a prestress is introduced, 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, the tensional material is a continuous fiber reinforcing wire, the expansive material for a concrete is contained in an amount of 5 to 30 kg /m3 to the concrete material, and aluminum oxide is contained in an amount of 0.2 to 2.0% by weight to the expansive material for a concrete.

2. The prestressed concrete according to claim 1, 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, a poly-p-phenylenebenzobisoxazole fiber, a stone material fiber such as a basalt fiber, and a rust prevention-treated PC steel strand wire.

3. The prestressed concrete according to claim 1, wherein the expansive material for a concrete is a mixture of one or more kinds selected from a lime-based expansive material such as quick lime, an ettringite-based expansive material such as calcium sulfoaluminate, an ettringite-lime composite-based expansive material, an iron powder-based expansive material, a magnesium-based expansive material, an aluminum powder-based expansive material, a shale-based expansive material, and a silica-based expansive material.

4. The prestressed concrete according to claim 1, wherein a wire of the tensional material has a wire diameter of 18 mm or less.

5. The prestressed concrete according to claim 1, wherein the tensional material has a tensile load of 300 kN or less per the wire.

6. The prestressed concrete according to claim 1, wherein the concrete has a thickness of 80 mm or less.

7. The prestressed concrete according to claim 1, wherein a discontinuous fiber reinforcing material is used.

8. The prestressed concrete according to claim 7, wherein the discontinuous fiber 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 stone material fiber such as a basalt fiber.

9. The prestressed concrete according to claim 1, wherein a pigment is mixed.

10. The prestressed concrete according to claim 1, wherein any irregularities are formed on a surface of the prestressed concrete using a soft form.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0086] FIG. 1 is an explanatory view of a conventional pretension bed (manufacturing apparatus).

[0087] FIG. 2 is a schematic view illustrating arrangement of a tensional material in the prestressed concrete according to the present invention.

[0088] FIG. 3 is a schematic view of a bending test body in the prestressed concrete according to the present invention.

[0089] FIG. 4 is a schematic diagram illustrating a bending test situation of the prestressed concrete test body according to the present invention.

[0090] FIG. 5 is a diagram illustrating a load position of the prestressed concrete test body according to the present invention.

[0091] FIG. 6 is a diagram illustrating a bending test result of three prestressed concrete test bodies with holes according to the present invention.

[0092] FIG. 7 is a diagram illustrating a bending test result of three prestressed concrete test bodies without holes according to the present invention.

[0093] 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 prestressed concrete test body according to the present invention.

[0094] 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 prestressed concrete test body according to the present invention.

[0095] 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 prestressed concrete test body according to the present invention,

[0096] 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 prestressed concrete test body according to the present invention.

[0097] 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 prestressed concrete test body according to the present invention.

[0098] 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 prestressed concrete test body according to the present invention.

[0099] FIG. 9-1 is a diagram illustrating a bending test result of the prestressed concrete test body (expansive material of the present invention) according to the present invention.

[0100] FIG. 9-2 is a diagram illustrating a bending test result of the prestressed concrete test body (commercially available expansive material: expansive material manufactured by Buddy Rhodes) according to the present invention.

DESCRIPTION OF EMBODIMENTS

[0101] Embodiments of the present invention will be described with reference to the drawings.

[0102] First, FIG. 1 illustrates a method for introducing a mechanical prestress by a conventional pretension method.

[0103] FIG. 1 is an explanatory view of a pretension bed (manufacturing apparatus).

[0104] This illustrates an example in which a tension of 50 tons (490 kN) is introduced by using a PC steel strand wire of φ26 mm as a tensional material. in this conventional example, as illustrated in FIG. 1, three prestressed concrete members are simultaneously manufactured in a longitudinal direction on a pretension bed (manufacturing apparatus 1) by a long line system.

[0105] 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.

[0106] 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.

[0107] 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.

[0108] A conventional prestressed concrete is manufactured in this way.

[0109] The concrete manufactured in this conventional example is a prestressed concrete for structural materials.

[0110] The present invention provides a prestressed concrete that can be used for general buildings.

[0111] A mechanical prestress can be introduced by a method similar to that in the conventional example (FIG. 1).

[0112] The prestressed concrete according to the present invention is achieved by a novel composition of a concrete, a tensional material, and a tensile load.

[0113] Formulation of a concrete is indicated below. (unit kg/m3)

[0114] cement: 543

[0115] admixture: fly ash: 63

[0116] admixture: expansive material: 20

[0117] aluminum oxide in expansive material: 0.24 (1.2% by weight)

[0118] water: 175

[0119] fine aggregate: 783

[0120] coarse aggregate: 810

[0121] admixture: water reducing agent: 7.50

[0122] water-binder ratio: 28%

[0123] A mixing ratio of an expansive agent is 20 kg/m3 as described above. The aluminum oxide in the expansive material is 1.2% by weight.

[0124] As the tensional material, a strand wire a carbon fiber reinforced polymer (CFRP) material having a diameter of 12.5 mm was used.

[0125] 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.

[0126] FIG. 2 illustrates an arrangement view of a tensional material.

[0127] 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.

[0128] A lattice reinforcement 3 was disposed on an upper surface of the tensional material. A covering thickness was about 7 mm.

[0129] 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.

[0130] After curing about for 24 hours, the tension was released.

[0131] After a prestressed concrete was manufactured, the compressive strength was 60 MPa or more, satisfying reference strength.

[0132] 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 (30 mm−7 mm) in covering thickness, that is, about 23 mm on one side.

[0133] The prestressed concrete according to the present invention had a weight of 648 kg.

[0134] 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.

[0135] As for the cracking, cracking occurred when one person with a body weight of 70 kg 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 the body weight 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 cracking was completely closed by a crimping effect due to a prestress, and water leakage was riot observed at all when a water leakage test was performed.

EXAMPLE 1 of Bending Test

[0136] Test for Comparison Between Mechanical Stress and Chemical Stress Using Bending Test.

[0137] 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.

[0138] A composition of the concrete was similar to the above case in FIG. 2.

[0139] 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 holes. 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.

[0140] Stress conditions of the six test bodies are as follow

[0141] CASE 1) with MS+with CS: having no holes

[0142] (CASE-2) with MS+without CS: having no holes

[0143] (CASE--3) without MS+with CS: having no holes

[0144] (CASE-4) with MS+with CS: having holes

[0145] (CASE-5) with MS+without CS: haying holes

[0146] (CASE-6) without MS+with CS: having holes

[0147] with MS: with a mechanical stress load induced by a continuous fiber reinforcing wire

[0148] without MS: without a mechanical stress load induced. by a continuous fiber reinforcing wire

[0149] with CS: with an expansive material

[0150] without. CS: without an expansive material

[0151] mechanical stress (MS) condition: continuous fiber reinforcing wire: carbon fiber wire: φ7.5 mm

[0152] Three continuous fiber reinforcing wires were used in a longitudinal direction (interval of 250 mm) (refer to FIG. 3)

[0153] tensile load: 20 kN per continuous fiber reinforcing wire

[0154] chemical stress (CS) condition: mixing ratio of an expansive material: 20 kg/m3

[0155] bending test condition: performed with a two point-concentrated load by using a bending test apparatus illustrated in FIG. 4.

[0156] Deflection was measured using a displacement meter 11.

[0157] span (distance between fulcrums: SL): 1,000 mm (refer to FIG. 5)

[0158] distance between internal load points (points to which a force is applied) (PL): 500 mm (refer to FIG. 5)

Test Result

[0159] FIGS. 6 and 7 are diagrams illustrating a relationship between a load and deflection.

[0160] FIG. 6 illustrates results of CASE-1 to CASE-3,

[0161] FIG. 6 illustrates a comparison result among three types each having no holes,

[0162] CASE-1: with MS+with CS,

[0163] CASE-2: with MS+without CS, and

[0164] CASE-3: without MS+without CS.

[0165] FIG. 7 illustrates results of CASE-4 to CASE-6.

[0166] FIG. 7 illustrates a comparison result among three types each having holes,

[0167] CASE-4: with MS+with CS,

[0168] CASE-5: with MS+without CS, and

[0169] CASE-6: without MS+without CS.

[0170] 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.

[0171] In CASE3 (FIG. 8-3) and CASES (FIG. 8-6), into which only a chemical stress had been introduced, cracks remained even at the time of unloading after fracture.

[0172] 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 so as to be in the original state and were not observed at the time of unloading after fracture.

[0173] The results of the bending test indicate the following.

[0174] fracture load residual deflection cracking situation after fracture (unloading)

TABLE-US-00001 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

[0175] 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.

[0176] This indicates that even when cracking occurs by an external force when a tensional material having carbon fiber material is 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 was observed.

[0177] 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 was crimped by the mechanical stress and was hardly observed, and there was no problem in a water leakage test at all.

[0178] In the cases only with a mechanical stress (CASE-2, CASE-4), a fracture load was higher than the case only with a chemical stress and was lower than the case with a composite stress of the mechanical stress and the chemical stress. At the time of unloading after fracture, a crack was crimped by the mechanical stress and was hardly observed, and there was no problem in a water leakage test at all.

[0179] 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 the crack had a slightly smaller size after fracture, but water leakage was not confirmed in a water leakage test.

[0180] By the above results, it has been found that the case in which a composite stress of a mechanical stress and a chemical stress has been introduced has higher strength than the case in which a mechanical stress or a chemical stress introduced singly.

[0181] 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 increase the strength.

[0182] Results of the test bodies each having no holes (CASE-1 to CASE-3) and test. bodies each having holes (CASE-4 to CASE-6) indicate that in test bodies each having no holes (FIG. 6), CASE-1 (MS+CS) and CASE-2 (M) have a high fracture load to approximately the same extent and CASE-3 (CS) has a slightly lower fracture load, by between two graphs (FIGS. 6 and 7).

[0183] On the other hand, in the test bodies each having holes (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.

[0184] This is a particularly remarkable result. The case of no holes in FIG. 6 exhibits a large effect of a mechanical stress. CASE-1 (MS+CS) and CASE-2 (MS) in which a mechanical stress has been introduced have high strength. CASE-3 (CS) in 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 notched shape or a cutout shape, for example, holes illustrated in FIG. 7, it is indicated that not only the mechanical stress but also the chemical stress has a large effect on the strength.

[0185] Conventionally, a high mechanical stress of 300 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.

[0186] As a conventional common sense, it has been considered that in a case where a mechanical stress is introduced, an effect of the stress is hardly shown even by combined use of a chemical stress (main purpose of chemical stress is to prevent a crack on a surface). However, by this test, it has been confirmed that in a low mechanical stress state of 300 kN or less with a plate thickness of 80 mm or less, the prestressed concrete is effective for increasing the strength by combined use of appropriate chemical stress conditions.

[0187] In particular, it has been confirmed that combination of a mechanical stress and a chemical stress is extremely effective when a prestressed concrete is used as a building member, partially having a notched shape, a cutout shape, or a hole, or having a high design property characterized by an irregular shape on a surface.

EXAMPLE 2 of Bending Test

[0188] Under the Conditions of Different Aluminum Oxide Content in the Expansive Material,

[0189] Test for Comparison Between Mechanical Stress and Chemical Stress Using Bending Test

[0190] A test body having a size similar to that of the above [Example 1 of bending test] was manufactured.

[0191] As the expansive material, an expansive material for the present invention and a commercially available expansive material were used as follows.

[0192] A bending test was performed in a similar manner as in the [Example 1 of bending test].

Expansive Material 1

[0193] Expansive material: an expansive material for the present invention(PL)

[0194] Aluminum oxide content: 1.2% by weight

Expansive Material 2

[0195] Expansive material: a commercially available expansive material: Buddy Rhodes Company(BL)

[0196] Aluminum oxide content: 15 to 25% by weight

[0197] The bending test results by the difference between the expansive materials (diagrams illustrating a relationship between a load and deflection) are illustrated in FIGS. 9-1 and 9-2.

[0198] In the graph of the expansive material for the present invention (aluminum oxide: 1.2% by weight) in FIG. 9-1, G1 (with tension and with an expansive material) has apparently higher flexural strength than G2 (with tension and without an expansive material). It can be understood that a synergistic effect is shown by using an expansive material for the present invention (aluminum oxide: 1.2% by weight).

[0199] Commercially available expansive material in FIG. 9-2: in the graph of the expansive material manufactured by Buddy Rhodes (aluminum oxide: 15 to 25% by weight) , G3 (with tension and with an expansive material) and G4 (with tension and without an expansive material) have approximately the same values. Commercially available expansive material: in a case of using an expansive material manufactured by Buddy Rhodes (aluminum oxide: 15 to 25% by weight), a synergistic effect has not been observed.

[0200] From the above, it can be understood that in a case where the aluminum oxide content in a concrete expansive material is 1.2% by weight, a synergistic effect of a mechanical stress and a chemical stress is shown, and in a case where the aluminum oxide content in a concrete expansive material is 15 to 25% by weight, a synergistic effect of a mechanical stress and a chemical stress is not shown.

[0201] As described above, the prestressed concrete of the present invention has high flexural strength, and a significant effect of reduction in thickness, reduction in weight, and suppression of cracking. Therefore, the prestressed concrete can be applied to an outer wall, a partition wall, a floorboard, a furniture material, or the like as a general building member, and becomes an excellent concrete plate having a completely new design property due to the lightweight thin plate and having a potential of a design property.

REFERENCE SIGNS LIST

[0202] 1 prestressed concrete

[0203] 2 tensional material

[0204] 3 lattice reinforcement

[0205] 4 hole (large)

[0206] 5 hole (small)

[0207] 10 test body

[0208] 11 displacement meter

[0209] 12 crack

[0210] T plate thickness of concrete

[0211] L length of test body

[0212] W width of test body

[0213] t thickness of test body

[0214] CFRP carbon fiber wire

[0215] SR spine reinforcement

[0216] SL span (distance between fulcrums)

[0217] PL distance between internal load points (points to which a force is applied)