JP2017115526A - Concrete construction method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a concrete construction method that makes it possible to easily increase the strength of adhesion between a steel plate deck and concrete to a sufficient level when the concrete is placed on the steel plate deck.SOLUTION: A concrete construction method includes: an application step of applying a resin adhesive to a surface of a steel plate deck; a spray step of spraying sand at or below a saturated and surface-dried condition level on the surface of the steel plate deck having the resin adhesive applied thereon; and a placement step of placing concrete on the sand-sprayed surface of the steel plate deck.SELECTED DRAWING: None

Description

  The present invention relates to a concrete construction method for placing concrete on a steel deck.

  Conventionally, when a structure having a steel slab such as a bridge is added or reinforced, concrete is placed on the surface of the steel slab and these are integrated.

  However, when concrete is placed on the steel slab in this way, the bond strength between the steel slab and concrete may not be sufficient.

On the other hand, when adding a structure with concrete or during reinforcement work, a new concrete is placed on the existing concrete to integrate the existing concrete (old concrete) and new concrete (new concrete). The construction method is known.
A concrete structure constructed by such a construction method is liable to deteriorate in strength and water tightness on the surface where old concrete and new concrete are in contact with each other. A technique for improving the strength has been proposed (see Patent Document 1).

  For example, a concrete construction method has been proposed in which an uneven surface is physically formed on the surface of existing concrete by shot blasting, etc., a resin adhesive is applied to the uneven surface, and then new concrete is placed thereon. Yes.

  In addition, for example, a concrete construction method has been proposed in which a resin material is applied to existing concrete and then an aggregate is spread by applying aggregates to ensure adhesion, and a new concrete is placed thereon (see FIG. Patent Document 2).

Japanese Patent No. 5341466 JP 2013-91982 A

  However, the techniques described in Patent Documents 1 and 2 are originally techniques for placing new concrete on existing concrete, and are not techniques for placing concrete on a steel deck.

  Moreover, in the technique described in the said patent document 1, since it is necessary to form a physical unevenness | corrugation in the surface of the existing concrete, it cannot be said that work is easy. In addition, it is more difficult to form physical irregularities in a steel slab whose surface is harder than existing concrete.

  Furthermore, with the technique described in Patent Document 2, it is difficult to sufficiently improve the adhesive strength between the steel deck and concrete. In the first place, the bond strength between the steel slab and the concrete is lower than the bond strength between the concrete, and thus the existing concrete and the steel slab differ in the adhesion state of the concrete to the surface. Even if the technique described in Patent Document 2 is applied to a steel deck, it is difficult to sufficiently improve the adhesive strength.

  In view of the above circumstances, the present invention is to provide a concrete construction method that can easily improve the adhesive strength between a steel slab and concrete when placing concrete on the steel slab. And

The concrete construction method of the present invention is:
An application process of applying a resin adhesive to the surface of the steel deck,
A spraying step of spraying sand having a surface dry saturated water state or less on the surface of the steel slab coated with the resin adhesive;
A placing step of placing concrete on the surface of the steel slab on which the sand is dispersed.

Here, “below the surface dry saturated state” means a surface dry saturated state or a state dried more than the surface dry saturated state.
More specifically, “below surface dry satiety state” means that sand flows according to the description of “4. Sample d)” in “Method of testing fine aggregate density and water absorption rate” of JIS A 1109: 2006. After filling the cone lightly and flattening the upper surface, it is swiftly struck 25 times without applying force only from the top surface of the sample, and then the flow cone without refilling the remaining space. This means that the sand cone is slumped when gently pulling up. On the other hand, in the above description, when the flow cone is pulled up, the state in which the sand cone remains without collapse corresponds to a state where the surface dry saturated state is exceeded.

According to such a configuration, when the concrete is placed on the steel slab, the adhesive strength between the steel slab and the concrete can be easily improved sufficiently.
Here, since a water film covering the sand is easily formed on the surface of the sand exceeding the surface dry saturated water state, when the sand exists between the steel deck and the concrete, the water film This prevents the adhesion of sand to the steel slab and concrete. Moreover, sand aggregates with the said film | membrane of water, and the surface area of sand will become small correspondingly.
However, since the water film is difficult to form on the surface of the sand that is below the surface dry saturated state, this sand is present between the steel slab and the concrete, resulting in the water film. Generation | occurrence | production of adhesion | attachment inhibition is suppressed and it becomes easy for sand to adhere to the adhesion surface of both a steel deck and concrete. And since the sand adhered in this way can form irregularities on both the steel floor slab and the concrete adhesion surface, the adhesion area (surface area) of the applied resin adhesive increases, and the anchor effect Can be demonstrated. Thereby, the adhesive strength by the apply | coated resin adhesive agent can be improved. Therefore, the adhesive strength between the steel deck and the concrete can be sufficiently improved without performing complicated work.

In the concrete construction method of the above configuration,
It is preferable to further include an adjusting step of adjusting the sand before being sprayed so as to be equal to or less than the surface dry saturated state.

  By further providing the adjusting step, it is possible to reliably obtain and scatter sand having the above-mentioned specific water content (surface dry saturated water or less). Therefore, the adhesive strength between the steel deck and concrete can be improved more reliably.

In the concrete construction method of the above configuration,
The particle size of the sand is preferably more than 0.15 mm and not more than 5.0 mm.

  When the particle size of the sand is in the above range, the bond strength between the steel deck and the concrete, particularly the tensile bond strength can be further improved.

In the concrete construction method of the above configuration,
In the spraying step, it is preferable scattering amount of the sand is less than 0.2 kg / ^{m 2} or more 1.5 kg / ^{m 2.}

  When the amount of sand applied is in the above range, the bond strength between the steel deck and concrete, particularly the tensile bond strength, can be further improved.

  ADVANTAGE OF THE INVENTION According to this invention, when placing concrete on a steel deck, the concrete construction method which can make it easy to fully improve the adhesive strength of a steel deck and concrete can be provided.

Graph showing the relationship between the surface dryness of sand and the tensile bond strength Graph showing the relationship between sand particle size and tensile bond strength Graph showing the relationship between the amount of sand applied and the tensile bond strength Schematic showing the specimen used for the shear strength test Schematic showing the test equipment used for the shear strength test Graph showing the relationship between sand surface dryness and shear bond strength Graph showing the relationship between sand particle size and shear bond strength Graph showing the relationship between sand application rate and shear bond strength

One embodiment of the concrete construction method of the present invention will be described.
The concrete construction method of the present embodiment includes a coating step in which a resin adhesive is applied to the surface of a steel floor slab, and sand that has a surface dry saturated water state or less on the surface of the steel floor slab to which the resin adhesive has been applied. A concrete construction method comprising a spraying step of spraying and a placing step of placing concrete on the surface of the steel slab to which the sand has been sprayed.

The construction method of this embodiment is a method of constructing a structure in which a steel deck and concrete are integrated by driving concrete into the steel deck.
The steel slab may be, for example, a steel slab part of a concrete structure such as a completed building, bridge or road, or a steel slab that constitutes a part of the structure under construction. Also good.

The concrete is not particularly limited, and any concrete may be used as long as it is normal concrete including cement, fine aggregate, coarse aggregate, water, other admixtures, admixtures and the like.
Moreover, concrete may contain the fiber. In other words, the concrete may be fiber reinforced concrete reinforced by including fibers.

(Coating process)
In this embodiment, the application | coating process which apply | coats a resin adhesive to the surface of a steel deck is implemented.
The resin adhesive used in this embodiment is not particularly limited as long as it is a resin adhesive capable of adhering concrete to a steel floor slab. For example, mortar such as polymer mortar, thermosetting resin-based synthetic resin And adhesives.
Among these, an epoxy resin-based synthetic resin adhesive is preferable from the viewpoint of adhesive strength.

  The surface of the steel floor slab to which the resin adhesive is applied in the coating process may be the entire surface of the steel floor slab where concrete is placed (contact surface with concrete), or with the concrete. It may be a part of the contact surface. From the viewpoint of adhesive strength, it is preferable to apply a resin adhesive to the entire contact surface with the concrete.

The amount of resin adhesive applied can be appropriately set according to the type of resin adhesive, the type of steel slab, the type of concrete, the required adhesive strength, etc. For example, an epoxy resin resin adhesive can be used. When used, it is preferably about 0.5 kg / m ² or more and 2.0 kg / m ² or less from the viewpoint of improving the adhesive strength.
Moreover, as a resin adhesive, what does not inhibit the hydration reaction of cement is preferable. Examples of such a resin adhesive include a highly durable epoxy resin used for joining fresh concrete.

(Spraying process)
After carrying out the coating process, a spraying process is carried out for spraying sand having a surface dry saturated water state or less on the surface of the steel slab coated with the resin adhesive.
This step is performed before the resin adhesive is cured.
The sand is not more than a surface dry saturated state, and is preferably in an absolutely dry (absolutely dry) state.
When the sand is in a surface dry saturated water state or less, when the sand is present at the interface between the surface of the resin adhesive and the concrete, the adhesive strength of the resin adhesive can be improved.

In this embodiment, that the sand is below the surface dry saturated state means that the sand is in accordance with the description of “4. Sample d)” in “Method for testing fine aggregate density and water absorption” in JIS A 1109: 2006. After lightly filling the flow cone and flattening the upper surface, swiftly squeeze 25 times from the upper surface of the sample without applying force only with the weight of the stab, and then squeeze the flow without refilling the remaining space. When the cone is gently pulled up vertically, it means that the sand cone is slumped. On the other hand, in the above description, when the flow cone is pulled up, the state in which the sand cone remains without collapse corresponds to a state where the surface dry saturated state is exceeded.
In addition, the absolutely dry state means a state of sand having a constant mass when heated at 105 ± 5 ° C.

  Examples of the sand include quartz sand, river sand, crushed sand, sea sand, and the like.

The sand preferably does not contain sulfur-containing components such as sulfates and sulfides and oxides. Moreover, it is preferable that sand does not contain a zeolite.
When the content of each of these components is increased, there is a risk of suppressing an increase in adhesive strength due to the resin adhesive.

Examples of the sand include those having a particle size of more than 0.15 mm and 5.0 mm or less, preferably more than 0.6 mm and 1.2 mm or less.
When the particle size is in the above range, the adhesive strength by the resin adhesive, particularly the tensile adhesive strength can be improved more easily.

The range of the particle size of the sand in the present embodiment is determined by the method described in JIS A 1102: 2014 using the upper and lower sieves specified in JIS Z 8801-1: 2006 as continuous sieves. This is sand that has been classified through
The upper limit and lower limit sieves refer to the sieves described in “3.2 Sieve” of JIS A 1102: 2014, that is, with a nominal aperture of 4.75 mm as defined in JIS Z8801-1: 2006. A sieve having a nominal aperture of 600 μm is called a 0.6 mm sieve.
For example, sand having a particle size of more than 0.15 mm and not more than 5.0 mm is 90 mass of sand classified by the above method using the 5.0 mm sieve and the 0.15 mm sieve as a continuous sieve. % Sand that contains more than 50%.

As the sand, for example, sand having a clay lump amount of 0.5% or less, preferably 0.3% or less, measured according to JIS A 1137: 2014 “Testing method for the amount of clay lump contained in aggregate”. Can be mentioned.
When the clay lump amount is in the above range, the adhesive strength by the resin adhesive can be further improved.

Examples of the sand include sand having a fine particle amount measured by JIS A 1103: 2014 “Aggregate fine particle amount test method” of 3.0% or less, preferably 1.0% or less.
When the amount of fine particles is within the above range, it becomes easier to improve the adhesive strength of the resin adhesive.

The it is not particularly limited quantity of sand (application rate) which is sprayed in the spraying process, for example, 0.2 kg / ^{m 2} or more 1.5 kg / ^m of less than ^2, preferably, 0.6 kg / ^{m 2} It is mentioned above that it is 0.8 kg / m ² or less.
When the amount of sand applied is in the above range, the adhesive strength by the resin adhesive, particularly the tensile adhesive strength, can be improved more easily.

  The means for spraying sand in the spraying step is not particularly limited. For example, a spraying means such as a sand spreader is preferable in that sand can be sprayed more uniformly on the surface coated with the resin adhesive.

(Adjustment process)
The concrete construction method according to the present embodiment may further include, for example, an adjustment step of adjusting the sand before being sprayed in the spraying step so as to be equal to or lower than the surface dry saturated water state.
As a method for adjusting the surface dry state of sand (adhesion state of water on the surface of sand) in the adjustment step, when the flow cone is pulled up according to JIS A 1109: 2006, the sand cone is in a slumped state. It may be adjusted by selecting the sand.
Alternatively, when the sand is dried and the flow cone is pulled up, the sand cone may be adjusted to a slumped state.
The method for drying the sand is not particularly limited, but for example, drying in the sun, drying by heating with a heating means such as a burner, drying by exposure to wind, and humidity are adjusted. For example, drying in a room.

As an adjustment method in the adjustment step, drying is preferable, and a drying method in which a drying time is short, such as drying by a jet heater, is particularly preferable from the viewpoint of time reduction.
Preferable drying conditions include, for example, drying at 90 ° C. to 110 ° C. for 3 hours to 12 hours.
Moreover, when adjusting sand to an absolutely dry state, drying to 105 ± 5 degreeC until it becomes a fixed mass is mentioned.

The adjustment process may be performed at any time before the spraying process is performed.
For example, the adjustment process is carried out in a place different from the concrete construction site, for example, a factory, and the sand adjusted to the surface dry saturated water state or less is transferred to the construction site in the factory or the like. It may be sprayed.

By providing such an adjustment step, it is possible to reliably obtain and scatter sand having the above-mentioned specific water content (surface dry saturated water or less). Therefore, the adhesive strength between the steel deck and concrete can be improved more reliably.
Moreover, even if the water absorption rate (JIS A 1109: 2006), water content, etc. of the sand to be used is different by providing the adjustment step as described above, the sand is more reliably adjusted to the surface dry saturated water state or less. Is possible.

(Placement process)
In the concrete construction method of the present embodiment, after performing the spraying step, a placing step of placing concrete on the surface of the steel slab on which the sand has been spread is performed.
In the placing process, concrete is placed on the steel floor slab as a contact surface with the concrete where the resin adhesive is applied and the sand is dispersed.
In addition, you may arrange | position steel materials, such as a reinforcing bar, at the time of concrete placement.
Further, this step is performed before the resin adhesive is cured. That is, before the resin adhesive is cured, the sand spreading step and the placing step are performed. In this way, by placing concrete before the resin adhesive hardens, the steel floor slab and concrete can be bonded not only by the adhesive strength of the concrete itself but also by the adhesive strength of the resin adhesive. Therefore, the steel slab and concrete can be bonded more firmly.

In the concrete construction method of the present embodiment, the following effects can be obtained by spraying the sand having a surface dry saturation state or less onto the surface coated with the resin adhesive.
That is, the sand sprayed from above the resin adhesive is below the surface dry saturated state, so that relatively dry sand exists at the interface between the resin adhesive applied to the steel slab and the concrete. become. Since it is difficult for a film of water covering the sand to be formed on the surface of the sand that is below the surface dry saturated water state, the sand exists between the steel slab and the concrete (interface). Generation | occurrence | production of the adhesion hindrance resulting from this film | membrane is suppressed, and it becomes easy for sand to adhere to the adhesion surface of both a steel deck and concrete. And since the sand adhered in this way can form irregularities on both the steel floor slab and the concrete adhesion surface, the adhesion area (surface area) of the applied resin adhesive increases, and the anchor effect Can be demonstrated. Thereby, the adhesive strength by the apply | coated resin adhesive agent can be improved. Therefore, the adhesive strength between the steel deck and the concrete can be sufficiently improved without performing complicated work.

In addition, the following can also be considered as the reason why sand having a surface dry saturated water state or less can improve the adhesive strength of the resin adhesive. That is, since the surface dry saturated water or less sand has very little water present on the surface, it is possible to suppress the adhesion between the sand and the resin adhesive caused by the water, Adhesive strength with steel deck and concrete can be increased. Thereby, the sclerosis | hardenability of a resin adhesive improves and it is thought that it is based on the synergistic effect of the anchor effect of sand and the sclerosis | hardenability improvement of a resin adhesive.
Moreover, by applying a resin adhesive on the steel slab, it is possible to prevent rainwater from reaching the steel slab even if cracks or the like occur in the concrete on the steel slab. That is, the adhesive layer can also act as a protective layer for protecting the steel deck.

In addition, because the steel slab and concrete can be sufficiently bonded as described above, not only the tensile strength (tensile adhesive strength) between these steel slab and concrete but also the shear strength (shear adhesive strength) is improved. It is also possible to make it.
Thereby, for example, local deformation of the steel deck can be reduced. For example, when the steel deck has a deck plate portion, local deformation of the deck plate portion can be reduced.
Also, for example, when the steel deck has a deck plate part and a U-rib shaped rib part welded to the deck plate, by reducing local deformation of the deck plate part as described above, It is also possible to reduce the generation of live load stress around the welded portion between the deck plate portion and the rib portion due to this local deformation.
Thus, it is possible to improve the fatigue durability of the steel slab by sufficiently bonding (integrating) the steel slab and concrete via the resin adhesive and sand.

Here, for example, in the case where the steel floor slab having the deck plate portion and the concrete are not sufficiently integrated, when a shearing force is generated between the steel floor slab and the concrete, There is a possibility that a deviation due to the shearing force occurs between the floor slab and the concrete. In order to suppress this shift, for example, a dive bar (a stud gbel or the like) is welded to the deck plate, and the dive bar is embedded in the concrete so that the steel slab and the concrete are sufficiently integrated. It is possible.
However, in the concrete construction method of this embodiment, as described above, the steel floor slab and the concrete can be integrated with sufficient adhesive strength by applying a resin adhesive and spraying sand. It is possible to improve the resistance against relative displacement between the concrete and the concrete, that is, the shear strength. Thereby, it is excellent in workability.
In addition, in this invention, in addition to adhere | attaching a steel deck and concrete by apply | coating a resin adhesive and spreading sand, you may reinforce by the above-mentioned gibber bar.

  In the concrete construction method of this embodiment, after applying a resin adhesive to the surface of the steel floor slab, the sand is spread on the surface of the resin adhesive so that the entire surface of the sand is covered with the resin adhesive. There is nothing. Therefore, unlike the case where sand is mixed with the resin adhesive, the surface of the dried sand which is below the surface dry saturated state is brought into contact with the concrete.

According to the concrete construction method of the present embodiment, sufficient adhesive strength can be obtained without cutting the surface of the steel slab that will be in contact with the concrete.
Therefore, when the surface of the steel slab that is to be in contact with the concrete is not cut, the construction work can be performed easily and easily.
In addition, when performing a polishing process in which the surface of the steel deck is polished by shot blasting or the like prior to the coating process, it is possible to further increase the bond strength between the steel deck and the resin adhesive.

  In addition, although this embodiment is as above, it should be thought that embodiment disclosed this time is an illustration and restrictive at no points. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

  Examples of the present invention will be described below, but the present invention is not limited thereto.

≪Steel floor slab≫
As the steel slab, a steel flat formwork (length 30 cm × width 30 cm × height 5 cm) was used.

≪Resin adhesive≫
As the resin adhesive, an epoxy resin adhesive (trade name: KC Bond, manufactured by Kashima Road Co., Ltd.) that is a two-component mixed type of a main agent containing an epoxy compound and a curing agent containing amines was used.

≪Concrete materials≫
The concrete materials shown in Table 1 below were prepared.

  Using the above-mentioned concrete material, kneaded so as to have a slump of 21.5 cm and an air volume of 2.0%, and placed on a steel slab as will be described later. Was made.

<Adjustment of sand type and surface dryness>
As shown in Table 3 below, five types of sand were prepared by sieving. The amount of clay mass and the amount of fine particles in each sand were both 0.

  The method for adjusting the particle size of the sand was as follows.

-Adjustment of particle diameter 0.15 mm (nominal aperture 150 μm), 0.3 mm (JIS A 1102: 2014) defined in JIS A 1102: 2014 “3.2 sieve” Nominal aperture 300 μm), 0.6 mm (nominal aperture 600 μm), 1.2 mm (nominal aperture 1.18 mm), 2.5 mm (nominal aperture 2.36 mm), 5.0 mm (nominal aperture 4.75 mm) ) The sieve was classified by the method described in JIS A 1102: 2014, with each sieve in the upper and lower limits of the particle size listed in Table 3 as a continuous sieve.

  Moreover, adjustment of the surface dry state of sand was adjusted with the following method.

-Adjustment of surface dry state According to "4. Sample d)" in "Method and test method for density and water absorption rate of fine aggregate" of JIS A 1109: 2006, sand is absorbed in water for 24 hours, and "4. Sample c)" Then, the water-absorbed sand was spread thinly on a flat surface (a bat was used) and dried evenly while gently sending warm air (using a dryer) while stirring. The drying condition of the surface of the sand was adjusted by this drying. Specifically, this drying is performed while checking the state with a flow cone, and the sand is collected in a state where the surface dry saturation state is exceeded (the water adhering to the sand surface is not dry). Thus, a sample was prepared (sample exceeding the surface dry saturated state). Furthermore, drying was continued while confirming the state with a flow cone, and when the surface was dry and saturated, sand was collected to prepare a sample (surface dry saturated sample). Further, the remaining sand was dried at 105 ° C. so as to be in an absolutely dry state, and then a sample (an absolutely dry state sample) having a temperature lowered to room temperature was produced.

<< Production of specimen 1 >>
A specimen was prepared as follows.
A steel plate formwork (30 cm × 30 cm × 5 cm) was used as a simulated material for a steel floor slab, and the surface was abraded with sandpaper and degreased with acetone. On the bottom surface of the flat formwork, application of a resin adhesive, dispersion of sand, and placement of concrete were sequentially performed, and specimens shown in Table 4 were produced. Table 4 also shows the particle size of the dispersed sand and the surface dry state.
Specifically, a specimen was prepared according to the following procedure.
(1) As the above-mentioned absolutely dry sample, No. 1-5 sand was prepared as described above (Examples 2 to 9). In addition, as the above-mentioned surface dry saturated state sample and the sample exceeding the above surface dry saturated state, No. 3 sand was prepared as described above (Example 1, Comparative Example 2).
(2) 1.4 kg / m ² of KS bond (manufactured by Kashima Road Co., Ltd.) was applied as a resin adhesive to the bottom surface of the plate mold (Examples 1 to 9, Comparative Examples 1 and 2).
(3) On the applied resin adhesive, the sand shown in Table 4 is not sprayed (Comparative Example 1) or a predetermined amount is sprayed (Examples 1 to 9 and Comparative Example 2), and the edge cutting material is coated thereon. As shown, four void tubes (inner Teflon (registered trademark) sheet affixed) having an inner diameter of 100 mm and a height of 50 mm were installed.
(4) Concrete is kneaded and placed in a flat formwork (in a void tube) that has been allowed to stand for 15 to 30 minutes after application of the resin adhesive. The concrete is then cured at 20 ° C. for 14 days. It produced (Examples 1-9, Comparative Examples 1 and 2).

<< Evaluation of specimen 1 >>
For each specimen, the tensile bond strength of the concrete was measured by the following method.

・ Measurement method of tensile adhesive strength An architectural laboratory type adhesion tester (Kenken type tensile tester, adhesion peel tester BA-800D, manufactured by Maruhishi Science Machinery Co., Ltd.) equipped with a dedicated jig for pulling was used. . About the said test body, the upper surface of the void pipe | tube was grind | polished with the cup sander etc., and the said exclusive jig | tool was adhere | attached and attached to the grind | polished surface with the adhesive agent (Bond Quick Mender, Konishi Co., Ltd.). After the attachment, the strength of the force (tensile strength, N / mm ² ) when pulled upward with the Kenken type tensile tester was measured.
This tensile strength was measured for four void tubes (n = 4), and the average was obtained as the tensile bond strength (average value).
The results are shown in Table 4 and FIGS.

As shown in Table 4 and FIG. 1, the example using sand having a surface dry saturated water or less tended to have a higher tensile adhesive strength than Comparative Example 1 in which concrete was adhered only with a resin adhesive. .
In Comparative Example 2 using sand in a state exceeding the surface dry saturated water state, the tensile adhesive strength was lower than that in Comparative Example 1.
As shown in Table 4 and FIG. 2, when the sand is in an absolutely dry state and the application amount is 0.7 kg / m ² , the tensile particle strength increases as the particle size increases, but the particle size is less than 0.6 mm. When it became small, there was a tendency for tensile adhesive strength to fall.
As shown in Table 4 and FIG. 3, when the sand is in an absolutely dry state and the particle size is 0.6 to 1.2 mm, when the amount of application increases, the tensile adhesive strength increases, but the amount of application is 1.5 kg / When m ² or more, the tensile bond strength tended to decrease.

<< Production of specimen 2 >>
The surface of a steel plate (φ10 cm × height 5 cm) as a steel floor slab is cleaned with sandpaper, degreased with acetone, and as shown in Tables 5 and 6, application of resin adhesive, sand dispersion, concrete The specimens were produced by placing them in order.
Specifically, a specimen was prepared according to the following procedure.
(1) In the same manner as in <Preparation of specimen 1>, classification is performed as shown in Table 3 above. Sand having a particle size corresponding to 1, 3, 5 was prepared.
(2) The surface dry state of this sand was prepared as shown in Table 6 below in the same manner as in <Preparation of specimen 1>.
(3) KS bond (for spring and autumn, manufactured by Kashima Road Co., Ltd.) as a resin adhesive was applied to the surface of the steel plate at 1.4 kg / m ² (11.0 g was applied to the φ10 cm surface of one specimen).
(4) On the applied resin adhesive, as shown in Table 6 below, predetermined sand was not sprayed or was sprayed in a predetermined amount.
(5) While placing the formwork on the steel plate, the concrete is kneaded with the same composition as in Table 2 above, and the concrete is placed on the steel plate that has been allowed to stand for about 20 minutes after application of the resin adhesive. After poking 8 times, it was vibrated with a mold vibrator for 5 seconds. Next, in order to prevent the unevenness of the surface from adversely affecting the test results, the surface is smoothed with a wooden or gold trowel, and the smoothed surface is covered with Saran Wrap (registered trademark) or the like and cured at 20 ° C. for 14 days. It was. In this way, a concrete layer (φ10 cm × height 5 cm) was formed to prepare a specimen having a total thickness of 10 cm as shown in FIG.

<< Evaluation of specimen 2 >>
About each test body, the shear bond strength between a steel plate and concrete was measured with the following method.

-Method for measuring shear bond strength As a method for measuring shear bond strength, a one-sided shear test was performed so that a relatively pure shear stress acts on the test section.
Specifically, in a room, using a shear test apparatus (Instron 5583 type mechanical fatigue tester, manufactured by Instron Japan Co., Ltd.) as shown in FIG. The steel sheet was mounted so as to face the direction and a shearing force was applied to the interface, and loaded on the steel plate side at a loading speed of 1 mm / min. In addition, resin was filled between the specimen and the jig attached to the outer periphery so as to fill the gap due to the unevenness.
And the load when a steel plate and a concrete layer peeled was measured as a maximum load, and the shear bond strength was measured by dividing the obtained maximum load by the adhesion area. This measurement was repeated using each of the three specimens (n = 3), and the average was obtained as the shear bond strength (average value).
The results are shown in FIGS.

As shown in FIG. 6, regardless of the dry state of the surface of the sand, the specimen to which sand was applied tended to have higher shear adhesive strength than the specimen to which sand was not applied.
As shown in FIG. 7, when the sand is in an absolutely dry state and the application amount is 0.7 kg / m ² , regardless of the particle size, the specimen to which the sand is applied is more than the specimen to which the sand is not applied. The shear bond strength tended to increase.
As shown in FIG. 8, when the sand is completely dry and the particle size is 0.6 to 1.2 mm, the specimen to which sand is applied is more than the specimen to which sand is not applied regardless of the application amount. The shear bond strength tended to increase.

Claims (4)

An application process of applying a resin adhesive to the surface of the steel deck,
A spraying step of spraying sand having a surface dry saturated water state or less on the surface of the steel slab coated with the resin adhesive;
A concrete construction method comprising a placing step of placing concrete on a surface of the steel slab to which the sand is dispersed.   The concrete construction method according to claim 1, further comprising an adjusting step of adjusting the sand before being sprayed so as to be equal to or less than the surface dry saturated state.   The concrete construction method according to claim 1 or 2, wherein a particle diameter of the sand is more than 0.15 mm and not more than 5.0 mm. In the spraying step, the construction method of the concrete according to any one of claims 1 to 3 scattering amount of the sand is less than 0.2 kg / ^{m 2} or more 1.5 kg / ^{m 2.}