JP7645481B2 - Expansive lightweight concrete deck with embedded shear reinforcement - Google Patents

Description

Article 30, paragraph 2 of the Patent Act applies [Name of submitted material] Report "Research and development of lightweight deck slabs using expansive materials that contribute to improving productivity and reducing life cycle costs" [Place of submission] National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure, Transport and Tourism [Date of submission] February 28, 2019 [Publications, etc.] [Name of submitted material] Report "Technological research and development that contributes to improving the quality of road policy" [Place of submission] National Institute for Land and Infrastructure Management, Ministry of Land, Infrastructure, Transport and Tourism [Date of submission] July 31, 2019

The present invention relates to a lightweight concrete deck slab with embedded shear reinforcement and expansive material.

Road bridges, which support the road structure with piers and other structures, sometimes use RC (reinforced concrete) decks made of lightweight concrete using lightweight aggregate in order to reduce the weight of the road structure.

Lightweight concrete usually has lower tensile and shear strength than ordinary concrete. RC decks are subject to punching shear failure due to the repeated wheel loads of vehicles traveling above them, and diagonal cracks penetrate between the top and bottom surfaces of the deck, leading to its ultimate failure. However, the durability of RC decks made of lightweight concrete is highly 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 decks made of ordinary concrete.

In response to this, there is a technique for improving the strength of lightweight concrete that introduces prestress using tension members into the concrete. 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, eliminating the need to mechanically introduce prestress. Patent Document 3 discloses a lightweight concrete deck that introduces chemical prestress using expansive materials and also improves water resistance.

JP 2008-44806 A Patent No. 3658568 Patent No. 6082207

Currently, there are high 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.

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 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 large, which could lead to cracks in the deck.

The present invention was made in consideration of the above problems, and aims to provide a lightweight concrete deck using expansive materials that can achieve improved durability and weight reduction.

The present invention for solving the above-mentioned problems is a deck formed of concrete, the deck being a precast deck for a road, having a thickness of 22 cm or less, the concrete containing an expansive material in addition to lightweight aggregate and cement to generate chemical prestress in the concrete , the expansive material being contained in an amount of 1.1 times or more of the standard admixture amount, the water-binder ratio of the concrete being 15% by weight or more and less than 38% by weight, a low-water content lightweight aggregate having a water content of more than 0% by weight and not more than 5% by weight is used for the coarse aggregate, pre-absorbed lightweight aggregate is used for the fine aggregate, and the deck is provided with a thickness direction of the deck. a lattice having a vertical length equal to a plurality of pitches of the horizontal rebars and a horizontal length equal to a plurality of pitches of the vertical rebars, and a lattice having a vertical length equal to a plurality of pitches of the horizontal rebars and a horizontal length equal to a plurality of pitches of the vertical rebars, wherein the lattice has a ratio of the sum of the cross-sectional areas of the shear reinforcement materials present within the lattice to the area of the lattice that is 0.28% or more in percentage.

In this invention, by arranging shear reinforcement in the deck thickness direction, it is possible to resist punching shear failure, and the shear reinforcement can also resist the expansive force in the deck thickness direction caused by the expansive material. Therefore, by increasing the amount of expansive material, strong chemical prestress can be introduced, and sufficient durability can be obtained even if the deck thickness is thin, making it possible to reduce the deck weight and improve its durability.

In addition , the shear reinforcement in the thickness direction of the deck can be positioned so that both ends are hooked onto the steel bars above and below the deck and fixed into the concrete, thereby providing effective resistance to the expansive force of the expansive material and punching shear failure of the deck.

The shear reinforcement is preferably located at the intersections of the longitudinal and transverse 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.

In addition, in the present invention, since the expansive force can be resisted by the shear reinforcement, a strong chemical prestress can be obtained by adding the expansive material in an amount 1.1 times or more the standard mixture amount.

In addition, in the present invention, by setting the water-binder ratio to less than 38% by weight, a deck slab with higher strength can be obtained, and by setting the water-binder ratio to 15% by weight or more, it is possible to ensure the necessary workability for the deck slab.

Furthermore , the lightweight concrete deck of the present invention is a precast deck, which reduces the labor burden associated with adding shear reinforcement.

Furthermore , in the present invention, by using a low-water-content lightweight aggregate as the coarse aggregate, the frost resistance of the deck slab can be improved, making it possible to use the deck slab in cold regions.

The present invention makes it possible to provide a lightweight concrete deck using expansive materials, which can improve durability and reduce weight.

FIG. 2 is a diagram showing a cross-sectional configuration of the road structure 3 in the thickness direction. A diagram showing the reinforcement state of the deck 31. A diagram showing a road structure 3. FIG. 2 is a diagram showing the concrete mix of specimen 30. FIG. FIG. 1 is a diagram showing a test apparatus 10. FIG. A diagram showing the concrete mix of the test specimens. FIG. A diagram showing the deck 31'.

The following describes in detail a preferred embodiment of the present invention with reference to the drawings.

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

As shown in FIG. 1, the road structure 3 has a deck 31, a pavement layer 35, etc.

The deck 31 is an expansive lightweight concrete deck made of concrete containing expansive materials, lightweight aggregate, cement, etc., and has reinforcing bars 311 and shear reinforcement 312 embedded inside. The deck 31 is also a precast product (precast deck) that has been manufactured in advance at a factory.

There are no particular limitations on the expansive material used in concrete, so long as it expands upon hydration. As described in Patent Documents 1 and 2, for example, expansive materials that conform to JIS A 6202, such as those that expand upon hydration through the production of calcium hydroxide, can be used.

In this embodiment, a standard type expansive material with a standard mixing amount of 30 kg per 1 ^m3 of concrete is used as the expansive material, and is mixed in an amount 1.1 times or more of the standard mixing amount, i.e., 33 kg or more per 1 ^m3 of concrete. This allows a strong chemical prestress to be obtained 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, an expansive material with a standard mixing amount of 20 kg per 1 ^m3 of concrete may be used as the expansive material, and in this case, it is sufficient to mix an amount 1.1 times or more of the standard mixing amount.

The lightweight aggregate can be a conventionally known artificial lightweight aggregate made from expanded shale, for example. The lightweight aggregate can be 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 the latter case in particular, 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.

There are no particular limitations on the type of cement, and various known Portland cements can be used. It is also possible to add various admixtures, such as water reducers and air content adjusters.

Here, it is desirable that the water-binder ratio when preparing concrete be 15% by weight or more and less than 38% by weight. Note that binder refers to cement and expansive material, and the weight of the binder is the combined weight of the cement and expansive material.

By setting the water-binder ratio to less than 38% by weight, a deck 31 with higher strength can be obtained. 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.

The reinforcing bars 311 are provided at the top and bottom of the deck slab 31, and are arranged vertically and horizontally so as to intersect at right angles on a plane.

The shear reinforcement 312 is provided in the thickness direction of the deck. For example, steel bars (shear reinforcement bars) are used as the shear reinforcement 312. However, the shear reinforcement 312 is not limited to this.

Both ends of the shear reinforcement 312 are bent toward the center in the thickness direction of the deck. These bent parts are positioned so that they hook onto the reinforcing bars 311 above and below the deck slab 31, and are fixed into the concrete.

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, a means for resisting the expansive force is secured, and then strong chemical prestress is introduced by increasing the amount of expansive material as described above.

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 cover thickness, in consideration of the case where the end of the reinforcing bar 311 is a loop joint. In this way, the deck 31 is made thinner, and the deck weight per unit area of 1 ^m2 is reduced, making the deck 31 lighter. Furthermore, making the deck 31 thinner also leads to a reduction in 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 above-mentioned joint conditions are not taken into consideration.

Figure 2(a) shows the reinforcement state of the deck 31, and shows the steel bars 311 and shear reinforcement members 312 arranged within the deck 31 as viewed from above.

As described above, the reinforcing bars 311 are arranged in a lattice pattern so that they intersect at right angles in 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 effectively resist the expansive force of the expansive material and the 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 between adjacent shear reinforcement members 312 vertically and horizontally where no shear reinforcement member 312 is arranged. However, the specific reinforcing bar arrangement method is not limited to this.

In this embodiment, as shown in FIG. 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 illustrated example) and a horizontal length corresponding to multiple pitches of the vertical reinforcing bars 311 (four pitches in the illustrated example). A lattice D is present 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 sufficient density of the shear reinforcement members 312 is ensured to obtain high resistance to the expansive force of the expansive material and punching shear failure of the deck slab 31.

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 reinforcing bar that is the shear reinforcement 312. Furthermore, for the shear reinforcement 312 located at the apex 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.

The pavement layer 35 constitutes the road surface on which vehicles and the like run. The pavement layer 35 can be a conventionally known material, and can be formed, for example, from asphalt. It is also possible to provide a waterproof layer between the deck slab 31 and the pavement layer 35.

The road structure 3 of this embodiment can be placed 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 placed 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 road construction, but also for replacing existing decks.

The effects of the deck of this embodiment will be explained below using examples. However, the present invention is not limited to these.

[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.

Example 1
The following materials were used as water, cement, expansive agent, aggregates (fine aggregate and coarse aggregate), and a high-range air-entraining 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 air-entraining 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 Expansive agent: CSA#20 manufactured by Denka Co., Ltd. Fine aggregate: Artificial lightweight aggregate Mesalite fine aggregate manufactured by Nippon Mesalite Industry Co., Ltd. Coarse aggregate: Artificial lightweight aggregate Mesalite coarse aggregate manufactured by Nippon Mesalite Industry Co., Ltd. High-performance AE water reducer: Masterglenium SP8SV manufactured by BASF Japan Ltd.

The expansive material used here is the standard type with a standard mixing amount of 30 kg per 1 ^m3 . The lightweight aggregates, both fine and coarse, are pre-absorbed with water, and surface-dried aggregates are used in the hope that the amount of expansion will be maintained over a long period of time due to the internal curing effect.

(Wheel load running test)
A test piece, which was a deck slab, was made using the concrete prepared according to the mix ratio shown in FIG. 4, and a wheel load running test was carried out.

Figure 5 shows this specimen 30. Figure 5 shows the plan view of specimen 30, and the internal reinforcement arrangement is also shown in the same manner as in Figure 2(a). As shown in Figure 5, specimen 30 is a flat plate with 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 specimen 30 in the same arrangement as reinforcing bars 311 and shear reinforcement 312 described above.

The concrete age of specimen 30 was 37 days. Tensile strain was also generated in the shear reinforcement 302 at the center of specimen 30, and it was confirmed that the shear reinforcement 302 resisted the expansion of the concrete caused by the expansive material.

The wheel load running test was carried out using a test device 10 shown in Figure 6 (a). This test device 10 has a load 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 specimen 30 from this load section 13.

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

The specimen 30 is supported by supports 17, 18 provided on the stand 16. Figure 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 the long sides, and is elastically supported by supports 18, 18 along each of the short sides.

A wheel is provided at the lower end of the load section 13. This wheel moves back and forth on the specimen 30 as the load section 13 moves back and forth. The load section 13 applies a wheel load to the specimen 30 by using this wheel.

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

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

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 by the formula shown below.
Neq＝Σ（Pi/157） ^m ×Ni
In the above formula, Pi (kN) is the actual load, 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.

As shown in Fig. 7, in the specimen 30 of Example 1, cracks occurred near the upper surface loading plate 19 at an equivalent number of runs of about 1.25 x 10 ^(100,000 times). At this point, the test did not clearly show a punching shear fracture state, but the displacement had increased significantly, so the test was terminated.

On the other hand, the inventors also conducted similar tests on a 25cm thick lightweight concrete slab (slab A) which did not use expansive material or shear reinforcement, and a 25cm thick lightweight concrete slab (slab B) which used 30kg of expansive material ^per 1m3 of concrete, with the standard mixing amount of 20kg per ^1m3 . Cracks penetrated diagonally from the top to the bottom of the slab after approximately 2.17 x 10 ^80,000 runs (equivalent number of runs) in the former slab A, and after approximately 1.84 x 10 ^90,000 runs (equivalent number of runs) in the latter slab B, leading to punch-out shear failure.

Thus, specimen 30 of Example 1 has durability more than 50 times that of deck A and more than 5 times that of deck B, confirming that lightweight concrete decks that use both expansive materials and shear reinforcement have high durability despite their 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.

[Frost resistance]
When lightweight aggregate that has absorbed water in advance is used, 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 described below as Example 2.

(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 aggregate and coarse aggregates A and B), hollow microspheres, and a high-range air-entraining water-reducing agent and air-entraining agent, which are admixtures, according to the mix ratio shown in Fig. 8. The amounts of the high-range air-entraining water-reducing agent and air-entraining agent shown in Fig. 8 are expressed as weight ratios (wt%) to the weight of the binder.
Water: tap water Cement: ordinary Portland cement Manufactured by Denka Co., Ltd. Expansive agent: ettringite-based expansive agent (30 type) Manufactured by Denka Co., Ltd. Fine aggregate: artificial lightweight aggregate Mesalite fine aggregate (pre-soaked product) Manufactured by Nippon Mesalite Industry Co., Ltd. Coarse aggregate A: artificial lightweight aggregate Mesalite coarse aggregate (pre-soaked product) Manufactured by Nippon Mesalite Industry Co., Ltd. Coarse aggregate B: artificial lightweight aggregate Mesalite coarse aggregate (low moisture content) Manufactured by Nippon Mesalite Industry Co., Ltd. Hollow microspheres: KIND air Manufactured by Denka Co., Ltd. High-performance AE water reducer: Masterglanium SP8SV Manufactured by BASF Japan Ltd.
Air entraining agent: Master Air 303A, manufactured by BASF Japan Ltd.

Here, the expansive agent is a standard type expansive agent with a standard mixing amount of 30 kg per cubic ^meter . The concrete of Example 2 is intended to improve the frost resistance by using low-moisture coarse aggregate B, 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/ ^cm3 .

Using each of the concretes of Example 2 and Comparative Examples 1 and 2, specimens were prepared for the freeze-thaw test described below. The specimens were rectangular columns measuring 100 mm long x 100 mm wide x 400 mm high.

(Freeze-thaw test)
The freeze-thaw test was conducted according to JIS A 1148 A (underwater freeze-thaw test method). In JIS A 1148 A, 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.

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 after 300 cycles, or when the relative dynamic modulus of elasticity fell to 60% or less, in accordance with JIS A 1148.

Figure 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 improved freeze-thaw resistance. Comparative Example 2, which contained 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 used low-moisture coarse aggregate B, had better frost resistance than Comparative Example 2, which contained hollow microspheres.

As described above, in this embodiment, by arranging the shear reinforcement 312 in the deck thickness direction within the deck 31, it is possible to resist punching shear failure, and the shear reinforcement 312 can also resist the expansive force in the deck thickness direction due to the expansive material. 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 reduce the weight of the deck 31 and improve its durability.

In addition, both ends of the shear reinforcement 312 are hooked onto the upper and lower reinforcing bars 311 and fixed into the concrete, providing excellent resistance to the expansive force of the expansive material and punching shear failure of the deck.

As mentioned above, the shear reinforcement 312 is placed at the intersection of the vertical and horizontal reinforcing bars 311 in a plan view, so that it can effectively resist the expansive force of the expansive material and the punching shear failure of the deck 31.

As described above, in this embodiment, the shear reinforcement 312 can resist the expansive force, so strong chemical prestress can be obtained by adding an amount of expansive material that is 1.1 times or more the standard mixing amount.

In addition, in this embodiment, by setting the water-binder ratio of the concrete of the slab 31 to less than 38% by weight, a slab 31 with higher strength can be obtained. Furthermore, if the water-binder ratio is 15% by weight or more, it is possible to ensure the necessary workability for the slab 31, which is a precast product. Furthermore, since the slab 31 in this embodiment is a precast slab, the labor burden associated with adding the shear reinforcement 312 is small.

Furthermore, by using low-moisture lightweight aggregate, the frost resistance of the deck 31 can be improved, making it possible to use it 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, as the self-drying effect caused by the hydration of cement consumes more water contained in the lightweight aggregate.

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 the shear reinforcement 312' has widened portions at both ends and is fixed into the concrete, as shown in the deck 31' in FIG. 10, and the widened portions are hooked onto the reinforcing bars 311.

In addition, the deck 31 in this embodiment is a precast product, but if labor burden is not a consideration, it can also be formed by pouring concrete in place.

The above describes preferred embodiments of the present invention with reference to the attached drawings, but the present invention is not limited to these examples. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the technical ideas disclosed in this application, and it is understood that these also naturally fall within the technical scope of the present invention.

3: Road structure 31, 31': Deck 35: Pavement layer 311: Steel bars 312, 312': Shear reinforcement material

Claims (2)

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,
A low-moisture lightweight aggregate with a moisture content of more than 0% by weight and not more than 5% by weight is used for the coarse aggregate.
The fine aggregate is lightweight aggregate that has been pre-absorbed.
and,
The floor slab,
At the top and bottom of the thickness direction of the deck, a plurality of reinforcing bars are embedded vertically and horizontally within the plane of the flat plate of the flat plate-shaped 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. The expansive lightweight concrete deck slab according to claim 1 , wherein the shear reinforcement is disposed at the intersections of the vertical and horizontal reinforcing bars in a plane.

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