JP7640238B2 - How to build it - Google Patents

Description

This disclosure relates to a cement-based spraying material and a construction method for constructing a structure using the cement-based spraying material.

Various cement-based materials have been known in the past. JP 2008-239384 A describes a thick spray mortar. The thick spray mortar is used to reinforce or repair concrete structures. For example, the thick spray mortar is used in a repair or reinforcement method for deterioration of concrete structures, specifically, in a repair and reinforcement method for viaducts such as railways or roads, or tunnels.

The thickening mortar for spraying is composed of a combination of an anionic surfactant and a shrinkage reducing agent. This makes it unnecessary to add a thickener and/or an antifoaming agent. The thickening mortar for spraying contains 100 to 300 parts by weight of fine aggregate, 0.1 to 10 parts by weight of a sulfonate salt which is an anionic surfactant, and 1.0 to 5.0 parts by weight of a shrinkage reducing agent per 100 parts by weight of cement, and does not contain a thickener or an antifoaming agent. This allows the unit volume weight to be 1.5 g/ ^cm3 or less within one hour immediately after the mortar is mixed. As a result, it is possible to pump the thickening mortar for spraying over long distances.

JP 2008-239384 A

The thick mortar for spraying mentioned above requires the use of special materials such as shrinkage reducing agents. In addition, since the cement-based spraying material is sprayed onto a core material, it may be necessary for the material to stand on its own after being sprayed. Furthermore, since the cement-based spraying material is sprayed from a nozzle, etc., it is required that it can be efficiently pumped using a hose or nozzle, etc.

The present disclosure aims to provide a cement-based spraying material and construction method that can improve the self-supporting properties after spraying and can be pumped efficiently.

The cement-based spraying material according to the present disclosure is a cement-based spraying material to be sprayed onto an object, comprising cement, fine aggregate in an amount of 80 parts by weight or more and 200 parts by weight or less per 100 parts by weight of cement, water in an amount of 30 parts by weight or less per 100 parts by weight of cement, and air having a volume ratio of 40% or less to the total volume when the cement, fine aggregate, and water are mixed, wherein a certain thickness of the cement-based spraying material is sprayed onto the outer periphery of a core material which is formed into a frame shape in a plan view, and the hardened cement-based spraying material becomes the outer shell of the concrete structure, the core material comprises steel material and air tubes, the steel material comprising H-shaped steel and L-shaped steel, the multiple steel materials being arranged so as to be aligned along a first direction and a second direction intersecting the first direction, and the air tubes are arranged between the web of the H-shaped steel and the inner surface of the L-shaped steel, and between the webs of a pair of H-shaped steels aligned along the first direction .

This cement-based spraying material contains 80 parts by weight or more and 200 parts by weight or less of fine aggregate and 30 parts by weight or less of water per 100 parts by weight of cement. Therefore, by containing 80 parts by weight or more of fine aggregate and 30 parts by weight or less of water, the fluidity of the cement-based spraying material can be appropriately maintained and the shape can be maintained after spraying. In addition, by containing 200 parts by weight or less of fine aggregate, the cement-based spraying material can be prevented from becoming too hard, so that the cement-based spraying material can be pumped efficiently. Furthermore, this cement-based spraying material contains air at a volume of 40% or less of the total volume when mixed. By containing air at a volume ratio of 40% or less, the pumpability and fluidity of the cement-based spraying material can be maintained, and the cement-based spraying material can be prevented from becoming too soft, thereby improving its self-supporting property after spraying.

The above-mentioned cementitious spray material may be mixed with a foaming agent that promotes the formation of air. In this case, the amount of air in the cementitious spray material can be secured by mixing in the foaming agent, so that the pumpability of the cementitious spray material can be improved by generating air with the foaming agent while increasing the self-supporting property.

The foaming agent may contain any of an alkyl sulfate surfactant, an alkylarylsulfonic acid surfactant, and an alkyl ether compound complex. In this case, the addition of a small amount of foaming agent can increase the air content of the cement-based spray material, and the air content can be easily adjusted.

The construction method according to the present disclosure is a construction method for constructing a concrete structure using the above-mentioned cement-based spraying material, and includes a step of constructing a covering portion of a concrete structure by spraying the cement-based spraying material onto a core material. In this construction method, the above-mentioned cement-based spraying material is sprayed onto a core material to construct a covering portion of a concrete structure. Thus, since a cement-based spraying material with high pumpability and self-supporting properties is sprayed onto the core material, the cement-based spraying material can be sprayed efficiently to a certain thickness. Therefore, the spraying of the cement-based spraying material onto the core material and the construction of the concrete structure can be carried out efficiently.

The above-mentioned construction method includes a step of preparing a cement-based spraying material by mixing cement, fine aggregate, and water prior to the step of constructing the covering portion, so that the volume of air relative to the total volume of the cement, fine aggregate, and water is 40% or less, and in the step of constructing the covering portion, the cement-based spraying material may be sprayed so that the volume of air relative to the volume of the sprayed cement-based spraying material is 7% or less. In this case, by preparing a cement-based spraying material containing air at a volume ratio of 40% or less, the cement-based spraying material can be efficiently pumped. In addition, by spraying the cement-based spraying material so that the volume ratio of air in the cement-based spraying material is 7% or less, the self-supporting property of the cement-based spraying material after spraying can be further improved.

This disclosure improves the self-supporting ability of the material after spraying and allows for efficient pressure delivery.

Fig. 1(a) is a perspective view showing an example of a steel material for a concrete structure, and Fig. 1(b) is a perspective view showing an example of a core material for a concrete structure. Fig. 2(a) is a perspective view showing a state where a cement-based spraying material is sprayed onto the core material of Fig. 1(b) to form an outer shell, and Fig. 2(b) is a perspective view showing a state where the core material is removed from the constructed outer shell. FIG. 3 is a perspective view showing an example of a completed concrete structure. FIG. 4 is a perspective view that illustrates an example of a cement-based spraying material. Fig. 5(a) is a side view showing the state of spraying the cement-based spraying material according to the embodiment, and Fig. 5(b) is a side view showing the state of constructing a structure using a 3D printer according to a comparative example. Fig. 6(a) is a cross-sectional view showing a process of constructing a covering by spraying a cement-based spraying material onto a core material, Fig. 6(b) is a cross-sectional view showing a process of reinforcing bar after removing the core material from the constructed covering, and Fig. 6(c) is a cross-sectional view showing a process of pouring a filler into the constructed covering.

Below, an embodiment of the cement-based sprayed material and construction method according to the present disclosure will be described with reference to the drawings. In the description of the drawings, the same or corresponding elements are given the same reference numerals, and duplicated descriptions will be omitted as appropriate. In addition, the drawings may be partially simplified or exaggerated for ease of understanding, and the dimensional ratios, etc. are not limited to those shown in the drawings.

In the cement-based spraying material and construction method according to the present embodiment, a structure is constructed. One example of the structure is a concrete structure. In general, when constructing a concrete structure, after assembling the reinforcing bars, a formwork is placed so as to surround the reinforcing bars, concrete is poured inside the formwork, and after a certain period of curing, the formwork is removed to construct the structure. Thus, in the construction of a structure, multiple types of work, including the placement of the formwork, are mixed together, and the work is currently complicated. In addition, in recent years, there has been a shortage of construction technicians, and the number of carpenter workers, such as formwork carpenters, has decreased, and there are concerns that it will become difficult to secure carpenter workers in the future.

In the cementitious spraying material and construction method according to this embodiment, for example, the outer shell structure of a structure is constructed by spraying the cementitious spraying material. This eliminates the need to place formwork, and allows work to be carried out efficiently. As a result, even in situations where there is a shortage of workers such as carpenters, work to construct a structure can be carried out efficiently.

First, an example of the construction of a structure will be described. In this embodiment, a concrete structure is constructed. First, as shown in Figures 1(a) and 1(b), a core material 1 is installed. The core material 1 corresponds to an example of an object to which a cement-based spraying material M (see Figure 2) is sprayed. The core material 1 includes, for example, a steel material 2 and an air tube 3. As an example, the steel material 2 includes an H-shaped steel 2b and an L-shaped steel 2c. However, the type of steel material is not particularly limited. Furthermore, the core material may include an expanded metal instead of the air tube 3, and the type of the core material is not particularly limited.

First, multiple steel materials 2 are arranged so that their longitudinal direction is aligned with the vertical direction D1, and are lined up along the first direction D2 and the second direction D3. At this time, the multiple steel materials 2 are arranged so that they form a frame in a plan view. The first direction D2 indicates the longitudinal direction of the multiple steel materials 2 in a plan view, and the second direction D3 indicates the transverse direction of the multiple steel materials 2 in a plan view.

In plan view, the multiple steel materials 2 may be arranged to form a rectangular frame. In this case, the four L-shaped steel pieces 2c form the corners of the steel material 2 in plan view, and the multiple H-shaped steel pieces 2b form the sides of the steel material 2 in plan view. For example, each H-shaped steel piece 2b is arranged so that the flange portion faces the outside of the steel material 2 in plan view, and each L-shaped steel piece 2c is arranged so that the outer surface of the L-shape faces the outside of the steel material 2 in plan view.

For example, two groups C1 each consisting of a plurality (three) of H-shaped steel bars 2b aligned along the first direction D2 are aligned along the second direction D3, and then L-shaped steel bars 2c are placed at one end and the other end of each group C1. Then, H-shaped steel bars 2b are placed between the pair of L-shaped steel bars 2c aligned along the second direction D3. The steel materials 2 are arranged as described above as an example, but the type, number and arrangement of the steel materials 2 are not limited to the above example and can be changed as appropriate.

After the steel material 2 is placed, the air tube 3 is placed. The air tube 3 is, for example, columnar. The cross section of the air tube 3 cut in a direction perpendicular to the longitudinal direction is, for example, rectangular with rounded corners. The air tube 3 is placed between a pair of steel materials 2. As a specific example, the air tube 3 is placed between the web of the H-shaped steel 2b and the inner surface of the L-shaped steel 2c, and between the webs of a pair of H-shaped steels 2b aligned along the first direction D2.

For example, the air tube 3 may include a first air tube 3b having a large cross-sectional area when cut along a plane perpendicular to the longitudinal direction, and a second air tube 3c having a small cross-sectional area. As an example, the first air tube 3b is arranged so that the long side of the cross-section extends along the first direction D2, and the second air tube 3c is arranged so that the long side of the cross-section extends along the second direction D3.

For example, two sets C2 each consisting of a plurality of first air tubes 3b (four in one example) aligned along the first direction D2 are aligned along the second direction D3, and then a plurality of second air tubes 3c (two in one example) are placed between each pair of sets C2. The above is an example of the arrangement of the air tubes 3, but the shape, size, number and arrangement of the air tubes 3 are not limited to the above example and can be changed as appropriate.

After the core material 1 (steel material 2 and air tube 3) is placed, as shown in Figures 2(a) and 2(b), a cement-based spraying material M with a certain thickness T is sprayed onto the outer periphery 1b of the core material 1 in a plan view to form the outer shell S1 of the structure S. The cement-based spraying material M in this embodiment is a material that hardens over time.

In this embodiment, the hardened cementitious spray material M becomes the outer shell S1, making it possible to eliminate the need for formwork. In addition, since the outer shell S1 of the structure S can be formed by spraying the cementitious spray material M, automating the spraying of the cementitious spray material M makes it possible to mechanically construct the outer shell S1, which corresponds to the formwork of the structure S. Furthermore, since the outer shell S1 is formed from the cementitious spray material M, it is possible to eliminate the need for demolding work, improving the durability of the structure of the outer shell S1. In addition, if the core material 1 contains H-shaped steel 2b, the H-shaped steel 2b improves the structural performance of the structure S.

The cement-based spraying material M is sprayed, for example, onto the outer peripheral surface 2d of the steel material 2 and the outer peripheral surface 3d of the air tube 3. The outer peripheral surface 2d of the steel material 2 includes, for example, the outer surface of the flange of the H-shaped steel 2b and the outer surface of the L-shaped steel 2c. The outer peripheral surface 3d of the air tube 3 is the outer surface of the air tube 3 exposed between a pair of steel materials 2 (H-shaped steel 2b or L-shaped steel 2c).

After the cement-based spraying material M has been sprayed and hardened, the air tube 3 is removed and the air tube 3 is removed. Then, as shown in Figures 2(b) and 3, a reinforcing bar cage is placed in the hollow portion S2 inside the outer shell S1, and concrete S3 is poured, and the construction of the structure S, which is a concrete structure, is completed.

As shown in FIG. 4, the cementitious spraying material M according to this embodiment is made of a thick material. When constructing an outer shell or the like by spraying the cementitious spraying material, it is necessary to adhere the cementitious spraying material to the core material so as not to cause sagging. In order to prevent sagging, it is possible to add a quick-setting agent or hardening accelerator to the cementitious spraying material. However, when a quick-setting agent or hardening accelerator is added, the surface of the cementitious spraying material hardens immediately, which may make trowel finishing difficult. This poses the problem that it may not be possible to perform the surface finishing properly.

In this embodiment, by spraying a thickened cementitious spray material M, it is possible to adhere the cementitious spray material M to a vertical surface without dripping. The adhesion of this cementitious spray material M to a vertical surface can be prevented without dripping, even without adding a quick-setting agent or hardening accelerator. After spraying the cementitious spray material M, the surface of the cementitious spray material M can be finished with a trowel.

For example, the cement-based spraying material M contains cement, fine aggregate, water, and air. The cement-based spraying material M contains 80 parts by weight or more and 200 parts by weight or less of fine aggregate and 30 parts by weight or less of water per 100 parts by weight of cement. In this case, the cement-based spraying material M can be used as a thick-mixed material.

The lower limit of the amount of fine aggregate in the cement-based spraying material M may be 90 parts by weight or more, 100 parts by weight or more, or 120 parts by weight or more per 100 parts by weight of cement. The upper limit of the amount of fine aggregate in the cement-based spraying material M may be 180 parts by weight or less, 160 parts by weight or less, or 150 parts by weight or less per 100 parts by weight of cement.

The upper limit of the amount of water in the cement-based spraying material M may be 25% or less, or 20% or less, based on 100 parts by weight of cement. The lower limit of the amount of water in the cement-based spraying material M may be 10% or more, 12% or more, 13% or more, 14% or more, or 15% or more, based on 100 parts by weight of cement.

The table flow test described in "12. Flow test 12.2 Flow value characteristics" of JIS R 5201:2015 (Physical test method for cement) was conducted on the cementitious spraying material M, and the result was 100+10 mm at 0 stroke flow. Because the container used in the test was 100 mm in size, it was found that the shape of the cementitious spraying material M hardly changed.

In the above table flow test, the cementitious spray material M is packed in two layers into a flow cone placed on a flow table, and the cementitious spray material M is poked 15 times with a poker rod. After the surface of the cementitious spray material M is smoothed, the flow cone is removed vertically. The cementitious spray material M is then subjected to 15 falling movements, and the maximum diameter after the cementitious spray material M spreads and the diameter at a right angle to this are measured, and the average value of these is the table flow value.

The cementitious spraying material M contains air, for example, whose volume ratio to the total volume of the cement, fine aggregate, and water when mixed is 40% or less. This reduces the viscosity of the thickened cementitious spraying material M, making it possible to pump the cementitious spraying material M. The upper limit of the volume ratio of air may be 35% or less or 30% or less. The lower limit of the volume ratio of air may be 10% or more, 15% or more, or 20% or more.

For example, when the cement-based spraying material M contains air whose volume ratio to the total volume at the time of mixing is 20% or more and 40% or less, the properties of the cement-based spraying material M become like whipped cream, the viscosity of the cement-based spraying material M decreases, and the pumpability of the cement-based spraying material M improves. In this way, even when the cement-based spraying material M containing an air volume ratio of 40% or less is sprayed, it foams after spraying and the air content of the cement-based spraying material M becomes 7% or less (it may be 6.5% or less, or 6% or less). Therefore, it is possible to make the air content of the cement-based spraying material M after spraying the same as the air content of general concrete.

For example, a foaming agent is mixed into the cement-based spray material M. By mixing the foaming agent into the cement-based spray material M, the amount of air in the cement-based spray material M is increased when the material is mixed. The foaming agent mixed into the cement-based spray material M may be any one of a synthetic surfactant, a resin soap-based foaming agent, and a protein-based foaming agent.

An example of a synthetic surfactant foaming agent is an alkyl sulfate surfactant, which is used in lightweight embankments. In this case, simply mixing in a small amount of foaming agent can further increase the amount of air in the cement-based spray material M.

However, the foaming agent mixed into the cement-based spraying material M is not limited to alkyl sulfate surfactants. Examples of foaming agents include fatty acid soap type, acylated sarcosine salt, disproportionated rosin acid soap, fatty oil sulfate ester salt, alkyl ether sulfate salt, amide ether sulfate, alkyl allyl sulfonate, alkyl ether sulfonate, naphthalene sulfonate, sulfosuccinic acid diester salt, sulfosuccinic acid ester salt, acylated methyl taurine salt, acylated taurine salt, alkyl phosphate ester, alkyl ether phosphate ester, quaternary ammonium salt, alkyl amidoamine, amphoteric surfactant, alkyl betaine type, sulfobetaine type, alkyl amido betaine type, and imidazoline type. , amine oxide, polyoxyethylene alkyl ether, polyoxyethylene polyoxypropylene alkyl ether, polyethylene glycol alkyl ester, polyoxyalkylene glycol rosin acid ester, sorbitan fatty acid ester, glycerin fatty acid ester, glycerin fatty acid ester borate ester, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene glycerin fatty acid ester borate ester, polyoxyethylene alkylamine, fatty acid monoethanolamide, fatty acid diethanolamide, keratin protein, casein, or albumin. In this case, the amount of air in the cement-based spraying material M can be effectively increased.

Methods for mixing foaming agents into cement-based spraying materials include, for example, mixing liquid foaming agent as part of the water during mixing, and incorporating air by mixing with a mixer. Another method is to whip the foaming agent in advance in a dedicated mixer, and then mix it with separately mixed cement-based spraying material to incorporate air. Still another method is to add powdered foaming agent at the same time as the cement and fine aggregate during mixing, and then mix with a mixer to incorporate air.

Incidentally, when constructing a structure A using a cement-based spray material M such as the aforementioned outer shell S1, a method using 3D printing may be considered, as shown in FIG. 5(b). With 3D printing, it is possible to freely draw a trajectory, making it easy to form a structure A even if it has a complex shape with curved surfaces, etc.

However, in 3D printing, structure A is constructed by stacking cement-based spray material M in layers, so the adhesion strength in the interlayer areas is lower than in the non-interlayer areas. This raises concerns that the interlayer areas may become structurally weak points in structure A, and furthermore, because the interlayer areas may become paths through which deterioration factors such as water or salt may penetrate, there is room for improvement in terms of the durability of structure A.

Therefore, in the construction method according to this embodiment, structure A is constructed by spraying cement-based spraying material M. When constructing structure A by spraying cement-based spraying material M, the aforementioned interlayer portion does not exist, so the durability of structure A can be improved. Below, an example of the construction method according to this embodiment will be described with reference to Figures 5(a), 6(a), 6(b), and 6(c).

First, the core material is constructed (process of constructing the core material). For example, the core material 11 is constructed so as to be frame-shaped when viewed from above. The core material 11 may be, for example, the air tube 3 described above or expanded metal, and the type of the core material 11 can be changed as appropriate. For example, if the core material 11 is an air tube 3, it is removed after the concrete covering portion B1 described below is constructed, but if the core material 11 is expanded metal, it is buried and killed after the covering portion B1 is constructed.

Meanwhile, cement, fine aggregate, and water are mixed to prepare a cement-based spraying material M (a process for preparing a cement-based spraying material). At this time, cement, 80 parts by weight or more and 200 parts by weight or less of fine aggregate per 100 parts by weight of cement, and 30 parts by weight or less of water per 100 parts by weight of cement are mixed.

Then, the air content of the cement-based spraying material M is increased, for example, until the volume ratio of the cement, fine aggregate, and water to the total volume when mixed is 40%. At this time, for example, a foaming agent may be mixed into the cement-based spraying material M to increase the air content of the cement-based spraying material M (step of mixing foaming agent, step of increasing the air content).

Next, the cement-based spray material M is sprayed onto the outer surface 11b of the core material 11 from a material spraying device equipped with, for example, a hose H1 and a nozzle H2 (step of spraying the cement-based spray material). As described above, the cement-based spray material M is a thick material and can be applied thickly. For example, the cement-based spray material M is sprayed onto the outer surface 11b of the core material 11 so that the thickness F is 10 cm or more.

The cementitious spraying material M is continuously sprayed to construct the covering portion B1 of the structure B (the process of constructing the covering portion). Then, the surface of the cementitious spraying material M is smoothed with a trowel (the process of finishing the cementitious spraying material with a trowel). After that, the cementitious spraying material M is hardened to complete the concrete covering portion B1 (the process of hardening the cementitious spraying material).

At this time, the air contained in the cement-based spraying material M is diffused by spraying the cement-based spraying material M, and the volume ratio of the air in the cement-based spraying material M after spraying is set to 7% or less of the total volume ratio of the cement-based spraying material M (process of reducing the air volume). Then, if the core material 11 is an air tube 3, the core material 11 is removed, and a reinforcing bar cage G is placed as shown in Figure 6 (b) (process of placing reinforcing bars).

At this time, for example, a reinforcing bar cage G including a number of main reinforcements G1 extending vertically and a number of tie bars G2 arranged to surround the main reinforcements G1 is placed inside the covering portion B1. After that, as shown in FIG. 6(c), concrete J is poured inside the covering portion B1 and allowed to harden, and then structure B, which is a concrete structure, is completed.

Next, the effects obtained from the cement-based spraying material M and construction method according to this embodiment will be described in detail. The cement-based spraying material M contains 80 parts by weight or more and 200 parts by weight or less of fine aggregate and 30 parts by weight or less of water per 100 parts by weight of cement. Therefore, by containing 80 parts by weight or more of fine aggregate and 30 parts by weight or less of water, the fluidity of the cement-based spraying material M can be appropriately maintained.

In addition, by including 200 parts by weight or less of fine aggregate, the cement-based spraying material M can be prevented from becoming too hard, and therefore the cement-based spraying material M can be pumped efficiently. Furthermore, the cement-based spraying material M contains air at a volume of 40% or less of the total volume when mixed. By including air at a volume ratio of 40% or less, the pumpability and fluidity of the cement-based spraying material M can be maintained, and the cement-based spraying material M can be prevented from becoming too soft, improving its self-supporting ability after being sprayed.

The cement-based spray material M of this embodiment is mixed with a foaming agent that promotes the formation of air. Therefore, the amount of air in the cement-based spray material M can be secured by mixing in the foaming agent, so the foaming agent can increase the amount of air in the cement-based spray material M while improving its self-supporting ability, and the amount of air can be easily adjusted.

The foaming agent according to this embodiment contains, for example, any one of an alkyl sulfate surfactant, an alkylarylsulfonic acid surfactant, and an alkyl ether compound complex. Therefore, by adding a small amount of foaming agent, the air content of the cement-based spray material M can be increased, and the air content can be easily adjusted.

In the construction method according to this embodiment, the covering portion B1 of the structure B is constructed by spraying the cement-based spraying material M. Therefore, the cement-based spraying material M, which has high pumpability and self-supporting properties, is sprayed onto the core material 11, so that the cement-based spraying material M can be sprayed efficiently to a certain degree of thickness F. Therefore, the spraying of the cement-based spraying material M onto the core material 11 and the construction of the structure B can be carried out efficiently.

The construction method according to this embodiment includes a step of preparing a cement-based spraying material M by mixing cement, fine aggregate, and water so that the volume of air is 40% or less relative to the total volume of the cement, fine aggregate, and water before the step of constructing the covering portion B1, and in the step of constructing the covering portion B1, the cement-based spraying material M is sprayed so that the volume of air is 7% or less relative to the volume of the sprayed cement-based spraying material M. Therefore, by preparing a cement-based spraying material M containing air at a volume ratio of 40% or less, the cement-based spraying material M can be efficiently pumped. In addition, by spraying the cement-based spraying material M so that the volume ratio of air in the cement-based spraying material M is 7% or less, the self-supporting property of the cement-based spraying material M after spraying can be further improved.

In addition, in this embodiment, a construction method for forming the outer shell of a structure has been described, which includes a process of installing a core material 1, a process of spraying a cement-based spraying material M onto the outer peripheral portion 1b of the core material 1 in a plan view, and a process of hardening the sprayed cement-based spraying material M to construct the outer shell S1. This construction method makes it possible to eliminate the need for formwork, so that the construction work of the structure can be carried out efficiently. As a result, even in a situation where there is a shortage of workers such as carpenters, the construction work of the structure can be carried out efficiently.

The above describes the embodiments of the cement-based spraying material and construction method according to the present disclosure. However, the present invention is not limited to the above-mentioned embodiments. In other words, it will be easily recognized by those skilled in the art that various modifications and changes are possible to the present invention without departing from the gist of the claims. For example, the composition of the cement-based spraying material and the content and order of the steps of the construction method are not limited to the above-mentioned content and can be modified as appropriate.

For example, in the above embodiment, an example was described in which the surface of the cement-based spraying material M was finished with a trowel after the covering portion B1 was constructed. However, it is not necessary to finish the surface of the cement-based spraying material with a trowel after the covering portion is constructed. In addition, in the above embodiment, an example was described in which the outer shell S1 of the structure S was constructed by spraying the cement-based spraying material M. However, the cement-based spraying material and construction method according to the present invention can be applied to other than the construction of the outer shell structure. Furthermore, as described above, the cement-based spraying material and construction method can be applied to the construction of concrete structures, and can also be applied to the construction of structures other than concrete structures. For example, the present invention can be applied to repair work on members by spraying materials, and can be applied to various sites.

1, 11...core material, 1b...periphery, 2...steel, 2b...H steel, 2c...L steel, 2d...periphery, 3...air tube, 3b...first air tube, 3c...second air tube, 3d...periphery, 11b...outer surface, A, B, S...structure, B1...cover, C1, C2...set, D1...vertical direction, D2...first direction, D3...second direction, G...reinforcing bar cage, G1...main bar, G2...hoop, H1...hose, H2...nozzle, J...concrete, M...cement-based sprayed material, S1...outer shell, S2...hollow portion, S3...concrete.

Claims (2)

A method for constructing a concrete structure using a cement-based sprayed material sprayed onto an object, comprising the steps of:
The cement-based spraying material is
Cement and
80 parts by weight or more and 200 parts by weight or less of fine aggregate per 100 parts by weight of the cement;
30 parts by weight or less of water per 100 parts by weight of the cement;
Air having a volume ratio of 40% or less to the total volume of the cement, the fine aggregate, and the water when mixed;
having
A certain thickness of the cement-based spraying material is sprayed onto the outer periphery of a core material formed into a frame shape in a plan view, and the hardened cement-based spraying material becomes the outer shell of the structure,
The core material includes a steel material and an air tube, and the steel material includes an H-shaped steel and an L-shaped steel.
A plurality of the steel materials are arranged so as to be aligned along a first direction and a second direction intersecting the first direction,
The air tubes are disposed between the web of the H-shaped steel and the inner surface of the L-shaped steel, and between the webs of a pair of the H-shaped steels arranged along the first direction ,
A step of constructing a covering portion of the concrete structure by spraying the cement-based spraying material onto the core material,
How to build it: a step of preparing the cement-based spraying material by kneading the cement, the fine aggregate and the water so that the volume of air relative to the total volume of the cement, the fine aggregate and the water is 40% or less, prior to the step of constructing the covering portion;
In the step of constructing the covering portion, the cement-based spraying material is sprayed so that the volume of air relative to the volume of the sprayed cement-based spraying material is 7% or less.
The method of claim 1 .

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