Expansive lightweight concrete deck with embedded shear reinforcement

Abstract

To provide a lightweight concrete floor slab with expansion material and the like capable of improving durability while achieving weight reduction.SOLUTION: A road structure 3 includes a floor slab 31 and a pavement layer 35. The floor slab 31 is formed of concrete. The concrete is lightweight concrete with expansion material that contains an expansion material added to the light-weight aggregate and cement. The floor slab 31 includes shear reinforcement 312 embedded in the thickness direction of the floor slab. Reinforcing bars 311 are embedded in the upper and lower parts of the floor slab thickness direction, and both ends of the shear reinforcing material 312 are arranged so as to be hooked on the upper and lower reinforcing bars 311.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a deck slab made of expansive lightweight concrete with embedded shear reinforcement. [Background technology]

[0002] In road bridges, where the road structure is supported by piers and other structures, reinforced concrete (RC) decks made of lightweight concrete using lightweight aggregate are often used in order to reduce the weight of the road structure.

[0003] Lightweight concrete usually has lower tensile and shear strengths than ordinary concrete. RC decks are subject to punching shear failure due to repeated wheel loads from vehicles running above them, and diagonal cracks penetrate between the top and bottom surfaces of the deck, leading to ultimate failure. However, the durability of RC decks made of lightweight concrete is largely dependent on the strength of the concrete, and it is believed that the durability of RC decks made of lightweight concrete is inferior to that of ordinary concrete.

[0004] In response to this, there is a technique for improving the strength of lightweight concrete in which prestress is introduced into the concrete using tension members. On the other hand, by mixing expansive materials into the concrete as in Patent Documents 1 and 2, the tensile resistance of the concrete can be improved by chemical prestress caused by the expansion of the expansive materials, and the effort of mechanically introducing prestress can be eliminated. Patent Document 3 discloses a lightweight concrete deck slab in which chemical prestress is introduced using expansive materials and water resistance is also improved. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2008-44806 A [Patent Document 2] Patent No. 3658568 [Patent Document 3] Patent No. 6082207 Summary of the Invention [Problem to be solved by the invention]

[0006] Currently, there are expectations for improved durability and lighter weight for RC decks in road structures, and the practical application of such RC decks will contribute to improving the productivity of road structures, including repair and reinforcement, and reducing life cycle costs.

[0007] For example, it is possible to increase the amount of expansive material in the concrete of the deck and introduce strong chemical prestress to increase the strength of the concrete and improve its durability, but in this case, there is a concern that the expansive force of the concrete in the thickness direction of the deck will be so large that cracks will occur in the deck.

[0008] The present invention has been made in consideration of the above problems, and has an object to provide a deck slab made of lightweight concrete with expansive material, which can achieve improved durability and weight reduction. [Means for solving the problem]

[0009] The present invention for solving the above-mentioned problems is a deck slab formed of concrete, The deck is a precast deck for a road and has a thickness of 22 cm or less; The concrete contains an expansive material in addition to the lightweight aggregate and cement. Chemical prestress is generated in the concrete by , The expansive material is contained in an amount 1.1 times or more of the standard admixture amount, the water-binder ratio of the concrete is 15% by weight or more and less than 38% by weight, a low-moisture lightweight aggregate having a moisture content of more than 0% by weight and 5% by weight or less is used as the coarse aggregate, and a lightweight aggregate that has been pre-absorbed with water is used as the fine aggregate, And the deck, At the top and bottom of the deck thickness direction, a plurality of reinforcing bars are embedded vertically and horizontally within the plane of the flat plate of the flat deck, and the vertical and horizontal reinforcing bars are perpendicular to each other within the plane. Shear reinforcement is embedded in the thickness direction of the deck. The shear reinforcement is arranged so that both ends of the shear reinforcement are hooked onto the upper and lower reinforcing bars, the grid is partitioned vertically and horizontally by the reinforcing bars, the vertical length is a plurality of pitches of the horizontal reinforcing bars, and the horizontal length is a plurality of pitches of the vertical reinforcing bars, and the grid exists such that the ratio of the sum of the cross-sectional areas of the shear reinforcement present in the grid to the area of ​​the grid is 0.28% or more in percentage. This is a lightweight concrete deck slab that incorporates expansive materials.

[0010] In this invention, by arranging shear reinforcement in the deck thickness direction, it is possible to resist punching shear destruction, and also to resist the expansive force in the deck thickness direction caused by the expansive material by the shear reinforcement. Therefore, it is possible to introduce strong chemical prestress by increasing the amount of expansive material, and sufficient durability is obtained even if the deck thickness is thin, making it possible to realize a lightweight deck and improved durability.

[0011] Also The shear reinforcement in the thickness direction of the deck is positioned so that both ends are hooked onto the steel bars above and below the deck and is fixed into the concrete, thereby providing effective resistance to the expansive force of the expansive material and punching shear failure of the deck.

[0012] before The shear reinforcement is preferably disposed at the intersections of the vertical and horizontal reinforcing bars in a plan view. By arranging the shear reinforcement in this manner, it is possible to effectively resist the expansive force caused by the expansive material.

[0013] Also In the present invention, the expansive force can be resisted by the shear reinforcement, so that a strong chemical prestress can be obtained by adding 1.1 times or more the standard mixing amount of the expansive material.

[0014] In the present invention, By setting the water-binder ratio to less than 38% by weight, a deck with higher strength can be obtained, while by setting the water-binder ratio to 15% by weight or more, the necessary workability for the deck can be ensured.

[0015] Also The lightweight concrete deck of the present invention is a precast deck. the law of nature The labor burden associated with adding shear reinforcement can be reduced.

[0016] Also In the present invention, Coarse By using low moisture content lightweight aggregate as aggregate, And This improves the frost resistance of the deck, making it possible to use it in cold regions. Effect of the Invention

[0017] According to the present invention, it is possible to provide a deck slab made of lightweight concrete with expansive material, which can realize improved durability and weight reduction. [Brief description of the drawings]

[0018] [Figure 1]A diagram showing the cross-sectional structure of road structure 3 in the thickness direction. [Diagram 2] A diagram showing the reinforcement state of the deck slab 31. [Diagram 3] A diagram showing road structure 3. [Figure 4] FIG. 2 is a diagram showing the concrete mix of specimen 30. [Diagram 5] FIG. [Figure 6] FIG. 1 is a diagram showing a test apparatus 10. [Figure 7] FIG. [Figure 8] A diagram showing the concrete mix of the test specimens. [Figure 9] FIG. [Figure 10] A diagram showing deck slab 31'. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

[0020] (1. Road structure 3) FIG. 1 is a diagram showing a road structure 3 including a deck (expansive lightweight concrete deck) 31 according to an embodiment of the present invention, and shows the cross-sectional configuration of the road structure 3 in the thickness direction.

[0021] As shown in FIG. 1, a road structure 3 includes a deck 31, a pavement layer 35, and the like.

[0022] The deck 31 is an expansive lightweight concrete deck made of concrete containing expansive material, lightweight aggregate, cement, etc., and has reinforcing bars 311 and shear reinforcement materials 312 embedded therein. The deck 31 is a precast product (precast deck) fabricated in advance at a factory.

[0023] There are no particular limitations on the expansive agent used in concrete, so long as it expands upon hydration. As described in Patent Documents 1 and 2, for example, an expansive agent conforming to JIS A 6202, such as one that expands upon hydration through the production of calcium hydroxide, can be used.

[0024] In this embodiment, the standard mixing amount of this expansive material is 1 m of concrete. 3 A standard type of expansive material, 30 kg per m of concrete, was used, and this was mixed at 1.1 times the standard amount, i.e., 1 m of concrete. 3 The mixing amount of the expansive material is 33 kg or more per cubic meter of concrete. This allows for strong chemical prestressing by the expansive material, improving the strength of the deck 31. However, the mixing amount of the expansive material is not limited to this amount. Also, the standard mixing amount of the expansive material is 100 kg or more per cubic meter of concrete. 3 An expanding agent having a mass of 20 kg per unit may be used, and in this case, the mass should be mixed in an amount that is 1.1 times or more the standard mixing amount.

[0025] The lightweight aggregate may be, for example, a conventionally known artificial lightweight aggregate made from expanded shale. The lightweight aggregate may be, for example, one that has absorbed water in advance, or a low-water-content lightweight aggregate with a water content of more than 0% by weight but not more than 5% by weight. In particular, in the latter case, the use of lightweight aggregate as the coarse aggregate can improve resistance to freezing and thawing (frost resistance), and the effect of this will be explained in the examples below.

[0026] The cement is not particularly limited, and various known Portland cements can be used. It is also possible to add various admixtures such as a water reducing agent and an air content adjusting agent.

[0027] Here, the water-binder ratio during concrete preparation is preferably 15% by weight or more and less than 38% by weight. Note that the binder refers to cement and expansive material, and the weight of the binder is the combined weight of the cement and expansive material.

[0028] By setting the water-binder ratio to less than 38% by weight, it is possible to obtain a deck 31 with higher strength. Furthermore, if the water-binder ratio is 15% by weight or more, it is possible to ensure the necessary workability for the deck 31, which is a precast product. However, the range of the water-binder ratio is not limited to this.

[0029] The reinforcing bars 311 are provided on the upper and lower parts of the deck slab 31, and are arranged vertically and horizontally so as to intersect at right angles on a plane.

[0030] The shear reinforcement 312 is provided in the thickness direction of the deck. For example, a steel bar (shear reinforcement bar) is used as the shear reinforcement 312. However, the shear reinforcement 312 is not limited to this.

[0031] Both ends of the shear reinforcement 312 are bent toward the center in the thickness direction of the deck slab. These bent parts are arranged so as to be hooked onto the reinforcing bars 311 above and below the deck slab 31, and are fixed in the concrete.

[0032] The shear reinforcement 312 resists punching shear failure of the deck 31, and also resists the expansive force in the deck thickness direction caused by the expansive material, preventing cracks in the concrete. In this way, in this embodiment, after securing a means for resisting the expansive force, a strong chemical prestress is introduced by increasing the amount of expansive material as described above.

[0033] The thickness of the deck 31 is set to 22 cm, which is the lower limit considering the required bending diameter of a general loop joint and the corresponding covering thickness, in consideration of the case where the end of the reinforcing bar 311 is made a loop joint. 2 This reduces the deck weight per unit, making the deck 31 lighter. Also, making the deck 31 thinner reduces the expansive force of the expansive material in the deck thickness direction. However, the thickness of the deck 31 is not limited to this, and it may be greater than 22 cm, or it may be thinner than 22 cm if the joint conditions as described above are not taken into consideration.

[0034] FIG. 2(a) is a diagram showing the reinforcement state of the deck 31, in which the reinforcing bars 311 and the shear reinforcement members 312 arranged in the deck 31 are seen from above.

[0035] As described above, the reinforcing bars 311 are arranged in a lattice pattern so as to intersect at right angles on a plane, and the shear reinforcement 312 is arranged at the intersections of the vertical and horizontal reinforcing bars 311. This allows the shear reinforcement 312 to adequately resist the expansive force of the expansive material and punching shear failure of the deck slab 31. The shear reinforcement 312 is also arranged in a staggered pattern at these intersections. In other words, there are intersections where no shear reinforcement 312 is arranged between adjacent shear reinforcement members 312 vertically and horizontally. However, the specific reinforcing bar arrangement method is not limited to this.

[0036] In this embodiment, as shown in Figure 2 (b), a lattice D is partitioned by vertical and horizontal reinforcing bars 311, with a vertical length corresponding to multiple pitches of the horizontal reinforcing bars 311 (four pitches in the example shown), and a horizontal length corresponding to multiple pitches of the vertical reinforcing bars 311 (four pitches in the example shown), and a lattice D exists such that the ratio of the sum of the cross-sectional areas of the shear reinforcement members 312 present within the lattice D to the area of ​​the lattice D is 0.28% or more, and by ensuring a sufficient density of the shear reinforcement members 312, high resistance is obtained against the expansive force of the expansive material and punching shear failure of the deck slab 31.

[0037] Here, the cross-sectional area of ​​the shear reinforcement 312 mentioned above is the area of ​​a cross section perpendicular to the longitudinal direction (deck thickness direction) of the steel bar which is the shear reinforcement 312. Furthermore, for the shear reinforcement 312 located at the vertex of lattice D (see a in Figure 2(b)), 1 / 4 of its cross-sectional area is within lattice D, and for the shear reinforcement 312 located at the edge of lattice D (see b in Figure 2(b)), 1 / 2 of its cross-sectional area is within lattice D.

[0038] The pavement layer 35 constitutes the road surface on which vehicles etc. run. The pavement layer 35 may be a conventionally known material, and may be formed of, for example, asphalt etc. It is also possible to provide a waterproof layer between the deck 31 and the pavement layer 35.

[0039] The road structure 3 of this embodiment can be arranged on a bridge pier 1a as shown in Fig. 3(a), or on a box culvert 1b as shown in Fig. 3(b). It can also be arranged inside a shield tunnel 1c as shown in Fig. 3(c). It can also be applied to various other roads. The deck 31 can be used not only for new roads, but also for replacing existing decks. EXAMPLES

[0040] The effects of the deck of this embodiment will be described below with reference to examples, although the present invention is not limited thereto.

[0041] [Durability] As described above, the deck 31 of this embodiment contains expansive material in addition to lightweight aggregate and cement in concrete, and the expansive force caused by the expansive material is resisted by shear reinforcement in the deck thickness direction. This makes it possible to increase the amount of expansive material and more actively introduce chemical prestress, thereby improving the durability of the deck. First, a wheel load running test was performed on the deck, and the results of the durability study are described below as Example 1.

[0042] Example 1 The following materials were used as water, cement, expansive agent, aggregates (fine aggregate and coarse aggregate), and a high-range AE water-reducing agent, which is an admixture, and were mixed according to the mix ratio shown in Figure 4 to prepare the concrete of Example 1. The amount of the high-range AE water-reducing agent shown in Figure 4 is the weight ratio (weight %) to the weight of the binder. Water; Tap water Cement: Ordinary Portland cement, manufactured by Taiheiyo Cement Corporation Expansion material: CSA#20 manufactured by Denka Co., Ltd. Fine aggregate; artificial lightweight aggregate Mesalite fine aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate; artificial lightweight aggregate Mesalite coarse aggregate manufactured by Nippon Mesalite Kogyo Co., Ltd. High-performance AE water reducer; Masterglenium SP8SV manufactured by BASF Japan Ltd.

[0043] Here, the standard mixing amount of the expansive material is 1 m 3 The lightweight aggregates, both fine and coarse, were pre-absorbed with water, and surface-dried aggregates were used in the hope that the amount of expansion would be maintained over a long period of time due to the internal curing effect.

[0044] (Wheel load running test) A deck specimen was made using the concrete prepared according to the mix ratio shown in Figure 4, and a wheel load running test was conducted.

[0045] Fig. 5 is a diagram showing this specimen 30. Fig. 5 is a plan view of the specimen 30, and the internal reinforcement arrangement is also shown in the same manner as in Fig. 2(a). As shown in Fig. 5, the specimen 30 is a flat plate having a rectangular plane, and its dimensions are 2,800 mm long x 4,500 mm wide x 220 mm thick. Reinforcing bars 301 and shear reinforcement 302 were embedded inside the specimen 30 in the same arrangement as the reinforcing bars 311 and shear reinforcement 312 described above.

[0046] The age of the concrete in the specimen 30 was 37 days. It was also confirmed that tensile strain was generated in the shear reinforcement 302 in the center of the specimen 30, and that the shear reinforcement 302 resisted the expansion of the concrete caused by the expansive material.

[0047] The wheel load running test was carried out using a test device 10 shown in Fig. 6(a). This test device 10 has a loading section 13 attached to a rail 12 supported from the upper side of a gate-shaped frame 11, and applies a wheel load to a test piece 30 from this loading section 13.

[0048] One end of a crank rod 14 is attached to the load portion 13, and the other end of the crank rod 14 is attached to a flywheel 15. When the flywheel 15 rotates, the load portion 13 reciprocates along the rail 12 as indicated by the arrow A in the figure.

[0049] The specimen 30 is supported by supports 17, 18 provided on a stand 16. Fig. 6(b) is a diagram showing the arrangement of the supports 17, 18 on the plane of the specimen 30. The specimen 30 is simply supported by supports 17, 17 along each of its long sides, and is elastically supported by supports 18, 18 along each of its short sides.

[0050] Wheels are provided at the lower end of the loading section 13. These wheels move back and forth on the specimen 30 in accordance with the reciprocating movement of the loading section 13. The loading section 13 applies a wheel load to the specimen 30 by means of these wheels.

[0051] The wheel load is applied to the specimen 30 via the loading plate 19. The chain line C in Fig. 6(b) indicates the range of movement of the wheel on the loading plate 19, which was set to an area of ​​500 mm vertical x 3000 mm horizontal at the center of the specimen 30 here.

[0052] The results of a wheel load running test performed on the specimen 30 (Example 1) using the test device 10 are shown in Fig. 7. In the wheel load running test, the initial wheel load at the start of running was 157kN (16tf), and the load was increased by 19.6kN (2tf) for every 40,000 runs. The number of runs was counted as one when the wheel of the load unit 13 of the test device 10 moved from one end of the moving range to the other end.

[0053] Figure 7 is a graph in which the horizontal axis represents the equivalent number of runs (times) and the vertical axis represents the deflection (mm) at the center of the test specimen 30. The equivalent number of runs is the result of converting the actual number of runs into the number of runs under a constant load condition of a wheel load of 157 kN, and the equivalent number of runs Neq can be calculated using the formula shown below. Neq = Σ(Pi / 157) m ×Ni In the above formula, Pi (kN) is the load actually applied, and Ni (times) is the number of times the load Pi was applied. m is a coefficient for equivalent conversion, and 12.76 is used here.

[0054] As shown in FIG. 7, the equivalent number of runs for the specimen 30 of Example 1 is about 1.25×10 10After 10,000 cycles, a crack appeared near the upper loading plate 19. At this point, the test did not clearly reach a state of punching shear failure, but the displacement had increased significantly, so the test was terminated.

[0055] On the other hand, the inventors have developed a 25 cm thick lightweight concrete deck (Deck A) that does not use expansive materials or shear reinforcement materials, and the standard mixing amount is 1 m 3 20kg of expansive material per 1m of concrete 3 Similar tests were also conducted on a 25 cm thick lightweight concrete deck (slab B) with 30 kg per slab and no shear reinforcement. 8 When operated 10,000 times (equivalent number of times), the latter floor slab B has a load of approximately 1.84 x 10 9 After 10,000 travels (equivalent travel times), the crack penetrated obliquely from the top to the bottom of the deck, leading to punching shear failure.

[0056] Thus, specimen 30 of Example 1 has durability 50 times or more than deck A and 5 times or more than deck B, and it was confirmed that the lightweight concrete deck using both expansive material and shear reinforcement has high durability despite its thin deck thickness. Furthermore, cracks in specimen 30 of Example 1 progressed more slowly than in decks A and B, and the placement of shear reinforcement is considered to be effective in suppressing brittle fracture.

[0057] [Freeze resistance] When using lightweight aggregate that has absorbed water in advance, concrete is produced with the voids inside the lightweight aggregate filled with water. However, in this case, liquid water remains inside the lightweight aggregate even after the concrete hardens, so there is a risk that deterioration will progress from inside the lightweight aggregate when the concrete is subjected to freezing and thawing. In response to this, the freeze-thaw resistance (frost resistance) can be improved by using low-water-content lightweight aggregate as described above, so a freeze-thaw test was conducted to examine the frost resistance, and the results are explained below as Example 2.

[0058] (Example 2 and Comparative Examples 1 and 2) The concrete of Example 2 and Comparative Examples 1 and 2 was prepared by mixing the following materials as water, cement, expansive agent, aggregates (fine aggregates and coarse aggregates A and B), hollow microspheres, and a high-performance air entraining water reducing agent and air entraining agent as admixtures according to the mix ratio shown in Fig. 8. The amounts of the high-performance air entraining water reducing agent and air entraining agent shown in Fig. 8 are expressed as weight ratios (weight %) to the weight of the binder. Water; Tap water Cement: Ordinary Portland cement manufactured by Denka Co., Ltd. Expansion material: Ettringite-based expansion material (Type 30) manufactured by Denka Co., Ltd. Fine aggregate; artificial lightweight aggregate Mesalite fine aggregate (pre-soaked product) Manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate A: Artificial lightweight aggregate Mesalite coarse aggregate (pre-soaked product) Manufactured by Nippon Mesalite Kogyo Co., Ltd. Coarse aggregate B: Artificial lightweight aggregate Mesalite coarse aggregate (low moisture content) manufactured by Nippon Mesalite Kogyo Co., Ltd. Hollow microspheres; KIND Air, manufactured by Denka Co., Ltd. High-performance AE water reducer; Masterglenium SP8SV manufactured by BASF Japan Ltd. Air entraining agent: Master Air 303A, manufactured by BASF Japan Ltd.

[0059] Here, the standard mixing amount of the expansive material is 1 m 3 It is a standard type expansive material with a weight of 30 kg per unit weight. The concrete of Example 2 is intended to improve the frost resistance by using coarse aggregate B with low moisture content, while the concrete of Comparative Example 2 is intended to improve the frost resistance of the concrete itself by mixing hollow microspheres in the outer portion, thereby supplementing the amount of air contained in the lightweight aggregate with hollow microspheres. The average particle size of the hollow microspheres is 80 μm, and the apparent density is 0.13 g / cm 3 It is.

[0060] Test specimens for the freeze-thaw test described below were prepared using each of the concretes of Example 2 and Comparative Examples 1 and 2. The test specimens were in the shape of a rectangular column measuring 100 mm long x 100 mm wide x 400 mm high.

[0061] (Freeze-thaw test) The freeze-thaw test was carried out according to JIS A 1148 A method (underwater freeze-thaw test method). In JIS A 1148 A method, a test specimen placed in a container so that its entire surface is covered with water is subjected to repeated freeze-thaw cycles, and the primary resonance frequency of the flexural vibration according to JIS A 1127 is measured at a specified cycle point.

[0062] The primary resonance frequency was used to calculate the relative dynamic modulus of elasticity, and in this test, the freeze-thaw resistance was evaluated based on the change in the relative dynamic modulus of elasticity. The test was terminated at the end of 300 cycles or when the relative dynamic modulus of elasticity fell to 60% or less, in accordance with JIS A 1148.

[0063] Fig. 9 shows the test results. In Comparative Example 1, the relative dynamic modulus of elasticity fell below 60% at 90 cycles, but in Example 2, which used low-moisture coarse aggregate B, the relative dynamic modulus of elasticity remained at 60% or more even at the end of 300 cycles, confirming the improvement in freeze-thaw resistance. Comparative Example 2, which contains hollow microspheres, also showed improved freeze-thaw resistance compared to Comparative Example 1, but after 150 cycles, the relative dynamic modulus of elasticity fell below 60%, confirming that Example 2, which uses low-moisture coarse aggregate B, has better frost resistance than Comparative Example 2, which contains hollow microspheres.

[0064] As described above, in this embodiment, by arranging the shear reinforcement 312 in the deck thickness direction within the deck 31, not only can punching shear failure be resisted, but also the expansive force in the deck thickness direction due to the expansive material can be resisted by the shear reinforcement 312. Therefore, it is possible to introduce strong chemical prestress by increasing the amount of expansive material, and sufficient durability can be obtained even if the deck thickness is thin, making it possible to realize weight reduction and improved durability of the deck 31.

[0065] In addition, by arranging both ends of the shear reinforcement 312 so that they are hooked onto the upper and lower reinforcing bars 311 and fixed into the concrete, it is possible to provide suitable resistance against the expansive force caused by the expansive material and punching shear failure of the deck slab.

[0066] As described above, the shear reinforcement 312 is arranged at the intersection of the vertical and horizontal steel bars 311 in a plane, thereby enabling the shear reinforcement 312 to provide suitable resistance against the expansive force of the expansive material and punching shear failure of the deck slab 31.

[0067] As described above, in this embodiment, the expansive force can be resisted by the shear reinforcement 312, so that a strong chemical prestress can be obtained by adding the expansive material in an amount equivalent to 1.1 times or more the standard mixing amount.

[0068] In this embodiment, the water-binder ratio of the concrete of the deck 31 is set to less than 38% by weight, thereby obtaining a deck 31 having higher strength. If the water-binder ratio is 15% by weight or more, it is possible to ensure the workability required for the deck 31, which is a precast product. In addition, since the deck 31 of this embodiment is a precast deck, the labor burden associated with adding the shear reinforcement 312 is small.

[0069] Furthermore, by using low-moisture lightweight aggregate, the frost resistance of the deck 31 can be improved, enabling its use in cold regions. In this embodiment, both the coarse aggregate and the fine aggregate, or only the coarse aggregate, can be low-moisture lightweight aggregate. Note that decreasing the water-binder ratio (increasing the unit cement amount) as described above is also effective in terms of frost resistance, since the self-drying effect caused by the hydration of cement consumes more water contained in the lightweight aggregate.

[0070] However, the present invention is not limited to this. For example, the shear reinforcement is not limited to the shear reinforcement 312 in Fig. 1, but may be arranged so that widened portions are provided at both ends of the shear reinforcement 312' and the shear reinforcement is fixed in the concrete and the widened portions are hooked onto the reinforcing bars 311, as shown in the deck 31' in Fig. 10.

[0071] Although the deck 31 in this embodiment is a precast product, if the labor burden is not a consideration, it can also be formed by pouring concrete in place.

[0072] Although the preferred embodiment of the present invention has been described above with reference to the accompanying drawings, the present invention is not limited to the above examples. It is clear that a person skilled in the art can come up with various modified or altered examples within the scope of the technical ideas disclosed in this application, and it is understood that these also naturally belong to the technical scope of the present invention. [Explanation of symbols]

[0073] 3: Road structure 31, 31': Floor slab 35: Pavement layer 311: Reinforced concrete 312, 312': Shear reinforcement

Claims

1. A deck made of concrete, The deck is a precast deck for a road and has a thickness of 22 cm or less; The concrete contains an expansive material in addition to the lightweight aggregate and cement to generate chemical prestress in the concrete; The expanding agent is contained in an amount 1.1 times or more of the standard mixing amount, The water-binder ratio of the concrete is 15% by weight or more and less than 38% by weight, The coarse aggregate is a low-moisture lightweight aggregate with a moisture content of more than 0% by weight but not more than 5% by weight. The fine aggregate is lightweight aggregate that has been pre-absorbed. and, The floor slab, At the top and bottom of the deck thickness direction, a plurality of reinforcing bars are embedded vertically and horizontally within the plane of the flat plate of the flat deck, and the vertical and horizontal reinforcing bars are perpendicular to each other within the plane. A shear reinforcement material is embedded in the deck thickness direction, and both ends of the shear reinforcement material are arranged so as to be hooked onto the upper and lower reinforcing bars, A lightweight concrete deck slab with expansive material, characterized in that the lattice is divided vertically and horizontally by the reinforcing bars, the vertical length is multiple pitches of the horizontal reinforcing bars, and the horizontal length is multiple pitches of the vertical reinforcing bars, and the ratio of the sum of the cross-sectional area of ​​the shear reinforcement present within the lattice to the area of ​​the lattice is 0.28% or more in percentage.

2. A deck slab made of lightweight concrete with expansive material as described in claim 1, characterized in that the shear reinforcement is arranged at the intersection of the vertical and horizontal steel bars in a plane.

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