Mortar and concrete sprayed structure and spraying method

Abstract

To improve durability of a sprayed layer while omitting labor to coat a water repellency agent.SOLUTION: The present invention relates to a mortar and concrete sprayed structure 1 comprising a sprayed layer including cement, water, a rapid hardening agent and a silane and siloxane-based water repellency agent. In the mortar and concrete sprayed structure, an addition rate of the silane and siloxane-based water repellency agent is increased gradually as it goes to an outside in a layer thickness direction. The silane and siloxane-based water repellency agent is contained in an outer part from the middle of the layer thickness direction, and the silane and siloxane-based water repellency agent is not contained in an inner part than that.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a mortar / concrete sprayed structure, consisting of a sprayed layer of mortar or concrete, constructed on the outer periphery of an existing concrete structure for seismic reinforcement, and a spraying method. [Background technology]

[0002] Conventionally, as earthquake-resistant reinforcement structures for existing concrete structures such as viaduct piers and building columns, there have been known methods such as the steel plate wrapping method (Patent Document 1 below), in which steel plates are wrapped around the periphery of an existing concrete structure and non-shrink mortar is filled between this steel plate and the existing concrete structure, and the RC (reinforced concrete) wrapping method (Patent Document 2 below), in which main bars and shear reinforcement bars are provided around the periphery of an existing concrete structure, formwork is installed around this periphery, concrete is poured into this formwork, and the formwork is removed after the concrete has hardened.

[0003] However, the steel plate winding method requires on-site welding to assemble the steel plates, and requires lifting work with a crane, which has the drawback of making on-site quality control and work management time-consuming.In addition, the RC winding method requires the installation and removal of formwork, which has the drawback of lengthening the construction period.

[0004] On the other hand, a mortar spraying method is also known in which reinforcing steel bars are wrapped around an existing concrete structure and mortar is sprayed onto it. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2015-214857 A [Patent Document 2] JP 2005-320819 A Summary of the Invention [Problem to be solved by the invention]

[0006] However, the sprayed layer formed by the mortar spraying method is thinner than the reinforcing layer formed by the RC lining method, so it is prone to cracks due to drying shrinkage and deterioration due to moisture penetration. For this reason, measures have been taken to reduce cracks by mixing expansive materials and shrinkage reducing agents into the sprayed mortar, but there are cases in which the effect is not necessarily sufficient.

[0007] On the other hand, a technique is known in which a water repellent is applied to the surface of a concrete structure to form a water absorption prevention layer in order to prevent the infiltration of water accompanied by deterioration factors such as chloride ions and acid rain into the concrete. However, conventional water repellents can only be applied after the surface to be applied has been sufficiently dried (for example, the surface moisture content is 8% or less) after demolding, which takes a long time to apply and increases the application cost. In addition, most conventional water repellents have the disadvantage that they require multiple applications, which is time-consuming and labor-intensive to apply. In other words, the first application of the water repellent must be applied to the surface of the concrete that has been sufficiently dried, and then the second application must be applied after waiting for a sufficient amount of time for the water repellent to dry. This process must be repeated at least three times. Conventional water repellents also have problems such as scattering and dripping during application, making it difficult to control the amount of application.

[0008] Therefore, the main object of the present invention is to provide a mortar / concrete sprayed structure and a spraying method that can improve the durability of the sprayed layer while eliminating the need for the labor of applying a water repellent agent. [Means for solving the problem]

[0009] In order to solve the above problems, the present invention according to claim 1 provides a mortar / concrete sprayed structure comprising a sprayed layer containing cement, water, a quick-setting agent, and a silane / siloxane-based water repellent, The present invention provides a mortar / concrete sprayed structure, characterized in that the content of the silane / siloxane water repellent agent is gradually increased toward the outside in the thickness direction of the sprayed layer.

[0010] In the invention described in claim 1, a silane / siloxane-based water repellent is used as the water repellent. This silane / siloxane-based water repellent is a water repellent that utilizes the characteristic of silane, which is highly permeable, and suppresses volatilization with polymeric siloxane. In the mortar / concrete sprayed structure of the present invention, the addition rate of this silane / siloxane-based water repellent is gradually increased toward the outside in the layer thickness direction of the sprayed layer, so that the water repellent effect and the shrinkage reduction effect can be effectively imparted to the surface layer where they are required. These effects can be imparted simply by spraying the mortar / concrete, eliminating the need to apply the water repellent after spraying. In addition, the water repellent is densely distributed in the required range from the surface to the inside of the sprayed layer, so that the sprayed layer can be imparted with sufficient durability.

[0011] The present invention according to claim 2 provides a mortar / concrete sprayed structure according to claim 1, in which the silane / siloxane-based water repellent agent is contained in the outer portion from the middle of the layer thickness direction, and is not contained in the inner portion beyond that.

[0012] In the invention described in claim 2, the silane-siloxane water repellent is contained in the outer portion from the middle of the layer thickness direction, and is not contained in the inner portion from that point on. This allows the water repellent to be concentrated in the outer portion without containing the water repellent in the portion where the water repellent effect is not required, so that water repellency can be effectively imparted while the amount of water repellent used can be reduced, which is economical.

[0013] According to a third aspect of the present invention, there is provided a sprayed mortar / concrete structure as described in the first aspect, in which a layer made of 100% of the silane / siloxane-based water repellent agent is formed on the surface thereof.

[0014] In the invention described in claim 3, the content of the silane-siloxane water repellent is gradually increased toward the outside in the layer thickness direction, and preferably a layer containing 100% silane-siloxane water repellent is finally formed on the surface, so that the surface of the sprayed layer is protected by the water repellent.

[0015] According to a fourth aspect of the present invention, there is provided a spraying method for forming a sprayed layer by spraying a spraying material containing cement, water, a setting accelerator, and a silane-siloxane water repellent, comprising the steps of: The spraying method includes kneading materials other than the quick-setting agent and the silane-siloxane water repellent, pumping the mixture with a pressure pump, adding the silane-siloxane water repellent to the mixture while gradually increasing the addition rate toward the outside in the layer thickness direction of the sprayed layer, and then adding the quick-setting agent and spraying the mixture.

[0016] The invention described in claim 4 above is a spraying method for gradually increasing the content of the silane-siloxane water repellent agent toward the outside in the thickness direction of the sprayed layer.

[0017] The present invention according to claim 5 provides the spraying method according to claim 4, in which the silane-siloxane based water repellent is not added in the initial stage of spraying, and the silane-siloxane based water repellent is added from the middle of the layer thickness direction of the sprayed layer, with the addition rate gradually increasing toward the outside of the layer thickness direction of the sprayed layer.

[0018] The invention described in claim 5 above is a spraying method in which the silane-siloxane-based water repellent is contained only in the outer portion of the sprayed layer from the middle of the layer thickness direction, and the silane-siloxane-based water repellent is not contained in the inner portion beyond that.

[0019] The present invention according to claim 6 provides a spraying method as described in claim 4, in which, when spraying of the cement-containing spraying material is completed, the pressure pump is stopped and a spraying material consisting of 100% silane-siloxane-based water repellent is sprayed onto the surface of the spray layer.

[0020] The invention described in claim 6 above is a spraying method for forming a layer made of 100% silane-siloxane water repellent on the surface of a sprayed layer. Effect of the Invention

[0021] As explained above in detail, the present invention can provide a mortar / concrete sprayed structure and spraying method that can improve the durability of the sprayed layer while eliminating the need for the labor of applying a water repellent agent. [Brief description of the drawings]

[0022] [Figure 1] 1 is a cross-sectional view of a mortar / concrete sprayed structure 1 according to the present invention. [Diagram 2] FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings.

[0024] As shown in Fig. 1, a mortar / concrete shotcrete structure 1 according to the present invention (hereinafter referred to as "shotcrete structure 1") is a shotcrete structure consisting of a shotcrete layer of mortar or concrete with reinforcing bars 2 arranged inside, constructed on the outer periphery of an existing concrete structure 30, such as an elevated bridge pier or a building pillar, for seismic reinforcement of the existing concrete structure 30. The shotcrete structure 1 according to the present invention is composed of a shotcrete layer containing cement, water, a quick-setting agent, and a silane / siloxane water repellent agent, as well as aggregate and various admixtures.

[0025] The silane-siloxane water repellent is a water repellent for mortar and concrete that is a mixture of silane molecules and polymeric siloxane molecules. Most of the general water repellents available on the market so far are silane-based water repellents. Although this silane-based water repellent has high permeability, it has the property of being easily volatile, so multiple applications are required to form a water repellent layer by coating. On the other hand, there is a water repellent that is less likely to volatilize, and is mainly composed of polymeric siloxane, a silicon molecule, but it has low permeability and has issues with long-term durability. To solve these issues, there is a silane-siloxane water repellent that is mainly composed of silane but has reduced volatility. This silane-siloxane water repellent has high viscosity and almost no scattering or dripping during application, making it possible to control the amount applied, and it has been reported that the amount of active ingredient is as high as about 80%, so a sufficient water repellent effect can be obtained with one application. Furthermore, by incorporating a silane / siloxane-based water repellent into the spray material, a water-repellent layer is formed inside, which inhibits the penetration of water from the outside. At the same time, the shrinkage reduction effect reduces cracks caused by drying shrinkage, and efflorescence inhibition effects can be imparted, improving the durability of the structure.

[0026] In the sprayed structure 1 according to the present invention, the water repellent is not applied to the surface, but the silane-siloxane water repellent is added to the sprayed material itself. In this case, as shown in FIG. 1, the silane-siloxane water repellent is gradually increased in content toward the outside of the layer thickness direction of the sprayed structure 1. That is, in the cross-sectional view of the sprayed structure 1 shown in FIG. 1, the content of the silane-siloxane water repellent is gradually increased in the layer farther from the concrete structure 30 (the layer closer to the surface of the sprayed layer 1) than in the layer closer to the concrete structure 30. In FIG. 1, the content of the silane-siloxane water repellent is expressed by a gradation in which the part with a high content is dark black and the part with a low content is light black. Here, the content of the silane-siloxane water repellent is the weight ratio (% / C) of the silane-siloxane water repellent to the cement.

[0027] The silane-siloxane water repellent is preferably added only to the outer portion from the middle of the layer thickness direction of the sprayed structure 1, and is not added to the inner portion beyond that. Also, the surface layer of the sprayed structure 1 may be a layer containing 100% silane-siloxane water repellent as long as the addition rate of the silane-siloxane water repellent is maximized in the layer thickness direction.

[0028] That is, as shown in FIG. 1, layer A, which includes reinforcing bars 2 arranged along the outer peripheral surface of concrete structure 30, is a layer sprayed with only mortar or concrete that does not contain silane-siloxane-based water repellent agent, and the outer layer B is a gradation layer in which the addition rate of silane-siloxane-based water repellent agent gradually increases toward the outside in the layer thickness direction of sprayed structure 1, and the surface layer C is a layer in which the addition rate of silane-siloxane-based water repellent agent is at its maximum in the layer thickness direction, preferably a layer made of 100% silane-siloxane-based water repellent agent.

[0029] The A layer does not contain silane / siloxane water repellent (addition rate 0%) and is a layer sprayed with a spray material that is made by adding an accelerator to mortar or concrete, similar to conventional spray materials. This A layer is formed to a thickness at least thick enough to bury the reinforcing bar 2, and it is preferable that the B and C layers form a covering portion for the reinforcing bar 2. Note that the spray material forming the A layer does not contain a silane / siloxane water repellent, but the spray material forming the adjacent B layer contains a silane / siloxane water repellent. Therefore, a small amount of silane / siloxane water repellent may be present in the A layer of the sprayed structure 1 due to the inclusion of the spray material sprayed when forming the B layer or the penetration of the silane / siloxane water repellent added to the B layer.

[0030] The B layer is a layer sprayed with a spray material in which the addition rate of the silane-siloxane water repellent is gradually or stepwise increased, for example, in the range of 0.05 to 5% / C, preferably 0.1 to 0.5% / C. The addition rate of the silane-siloxane water repellent can be adjusted by adjusting the amount of the silane-siloxane water repellent sent to the mortar or the like pumped by the pressure pump 11 in the spray system diagram shown in Figure 2 using the water repellent supply device 16. When the addition amount of the silane-siloxane water repellent is increased stepwise, it is preferable to form a spray layer in which the amount is changed in at least three steps, preferably five or more steps. The thickness of the B layer is preferably formed to correspond to the appropriate covering thickness of the reinforcing bar 2.

[0031] The C layer is a layer in which the content of the silane-siloxane water repellent is greater than that of the A layer and the B layer, and is the layer in which the content of the silane-siloxane water repellent is the greatest in the layer thickness direction. It is preferable to form a layer formed by spraying 100% of the silane-siloxane water repellent without including cement, etc. In order to form a layer containing 100% of the silane-siloxane water repellent, in the spraying system diagram shown in Figure 2, when the spraying of the B layer is completed, the pump 11 for pumping the mortar, etc. is stopped, the quick-setting agent supply device 14 is stopped, and only the water repellent supply device 16 for the silane-siloxane water repellent and the compressor 13 are operated, and the silane-siloxane water repellent is sprayed from the nozzle 12.

[0032] To spray the spraying material, as shown in Figure 2, cement, water, aggregate, admixtures, etc. are charged into a mixer 10 and mixed, and the mixed mortar or concrete (hereinafter referred to as "mortar, etc.") is pumped by a pressure pump 11 toward a nozzle 12. On the way, compressed air is mixed in from a compressor 13, a setting accelerator 15 is added by a setting accelerator supply device 14, and a silane-siloxane water repellent 17 is added by a water repellent supply device 16.

[0033] In this spraying device, when spraying a spraying material containing no silane-siloxane water repellent, the operation of the water repellent supply device 16 is stopped so that the silane-siloxane water repellent 17 is not added to the mortar, etc. When the addition rate of the silane-siloxane water repellent 17 is gradually increased toward the outside in the layer thickness direction of the sprayed structure 1, the operation of the water repellent supply device 16 is adjusted to adjust the supply amount of the silane-siloxane water repellent 17 to the mortar, etc. When spraying a spraying material containing 100% silane-siloxane water repellent, the operation of the pressure pump 11 and the quick-setting agent supply device 14 is stopped so that the water repellent 17 supplied from the water repellent supply device 16 is sprayed from the nozzle 12 by the compressed air of the compressor 13.

[0034] Next, a procedure for forming a sprayed structure 1 on the outer periphery of an existing concrete structure 30 will be described. First, as shown in Fig. 1, the surface of the concrete structure 30 is scraped, missing parts are reinforced, and exposed reinforcing bars are subjected to rust prevention treatment, and reinforcing bars 2 are arranged around the concrete structure 30. The reinforcing bars 2 are composed of main bars 2a arranged in the vertical direction and at a predetermined interval in the circumferential direction, and hoop bars 2b arranged in the vertical direction and at a predetermined interval in the circumferential direction so as to wrap around the main bars 2a.

[0035] Once the placement of the reinforcing bars 2 is complete, the spraying material is sprayed using the spraying device shown in Figure 2. To spray, first the materials other than the quick-setting agent and the silane-siloxane water repellent, i.e. cement, water, aggregate, admixtures, etc. are mixed in a mixer 10, and this is pumped by a pressure pump 11, and compressed air from a compressor 13 and quick-setting agent 15 from a quick-setting agent supply device 14 are mixed in and sprayed from a nozzle 12. The spraying method at this time can be performed according to the usual method.

[0036] When a sprayed layer thick enough to bury the reinforcing bars 2 is formed by spraying a spray material that does not contain a silane-siloxane water repellent, the mortar or the like pumped by the pressure pump 11 is sprayed on top of the sprayed layer 1 with the silane-siloxane water repellent added at a gradually increasing rate toward the outside in the thickness direction of the sprayed layer 1.

[0037] Thereafter, when forming a layer consisting of 100% silane-siloxane-based water repellent on the surface of the sprayed structure 1, after spraying of the cement-containing spray material is completed, the pressure pump 11 is stopped and the quick-setting agent supply device 14 is also stopped so that mortar, etc. and quick-setting agent are not supplied, and only the silane-siloxane-based water repellent from the water repellent supply device 16 and the compressed air from the compressor 13 are sprayed from the nozzle 12.

[0038] In the sprayed structure 1 of the present invention, the addition rate of the silane / siloxane water repellent agent gradually increases toward the outside in the layer thickness direction of the sprayed layer, so that the surface layer can be imparted with water repellency and shrinkage reduction effects simply by spraying the spray material, eliminating the need to wait for the surface to dry after spraying before applying the water repellent agent, as was done in the past. In addition, the water repellent agent is distributed at high density in the required range from the surface layer to the inside of the sprayed structure 1, so that the sprayed structure 1 can be imparted with sufficient durability.

[0039] Furthermore, the silane / siloxane water repellent is added from midway through the layer thickness to the outer portion, but not further inward. This allows the water repellent to be concentrated in the outer portion where the water repellent effect is needed, reducing the amount of water repellent used and making it more economical.

[0040] Furthermore, when a layer made of 100% silane-siloxane water repellent is provided on the surface of the sprayed structure 1, the surface of the sprayed structure 1 is protected by the water repellent.

[0041] [Other examples] In the above embodiment, the case where the present invention is applied to a wet spraying method has been described, but the present invention can also be applied to a dry spraying method in the same manner. [Explanation of symbols]

[0042] 1... mortar / concrete sprayed structure (sprayed structure), 2... reinforcing bar, 10... kneader, 11... pressure pump, 12... nozzle, 13... compressor, 14... quick-setting agent supply device, 15... quick-setting agent, 16... water-repellent agent supply device, 17... water-repellent agent, 30... existing concrete structure

Claims

1. A mortar / concrete sprayed structure comprising a sprayed layer containing cement, water, an accelerator, and a silane / siloxane-based water repellent, A mortar / concrete sprayed structure, characterized in that the content of the silane / siloxane water repellent agent is gradually increased toward the outside in the thickness direction of the sprayed layer.

2. 2. A mortar / concrete sprayed structure according to claim 1, wherein the silane-siloxane water repellent agent is contained in the outer portion from the middle of the layer thickness direction, and is not contained in the inner portion therebetween.

3. 2. The sprayed mortar / concrete structure according to claim 1, further comprising a surface layer formed of 100% of said silane-siloxane water repellent.

4. A spraying method for forming a sprayed layer by spraying a spraying material containing cement, water, a quick-setting agent, and a silane-siloxane water repellent, comprising the steps of: A spraying method characterized in that materials other than the quick-setting agent and the silane-siloxane water repellent are mixed and pumped by a pressure pump, the silane-siloxane water repellent is added to the mixture while gradually increasing the addition rate toward the outside in the layer thickness direction of the sprayed layer, and then the quick-setting agent is added and the mixture is sprayed.

5. 5. A spraying method as described in claim 4, in which the silane-siloxane-based water repellent is not added in the initial stage of spraying, and the silane-siloxane-based water repellent is added from the middle of the layer thickness direction of the sprayed layer, with the addition rate gradually increasing toward the outside of the layer thickness direction of the sprayed layer.

6. A spraying method as described in claim 4, wherein, when spraying of the cement-containing spraying material is completed, the pressure pump is stopped and a spraying material consisting of 100% silane-siloxane-based water repellent is sprayed onto the surface of the sprayed layer.

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