Repair methods and repair structures for existing concrete deck slabs

Abstract

In road bridge repair work, where a replacement material layer is provided on the upper surface to repair the existing concrete deck, the objective is to improve the tensile performance of the replacement material layer having construction joints while ensuring workability. [Solution] A repair method for an existing concrete slab, comprising: performing a joint treatment on the upper surface of the existing concrete slab after cutting the existing asphalt layer, and then pouring replacement material onto the joint treatment surface to create a replacement material layer, the method comprising: pouring the preceding replacement material onto the joint treatment surface to form a vertical joint surface; and pouring the subsequent replacement material onto the vertical joint surface to form a replacement material layer having construction joints, wherein the replacement material is an ultra-high performance fiber-reinforced cement composite material, and the construction joints are formed in an uneven shape with straight sections intersecting the joint direction in a plan view when located in a region where a tensile force greater than the tensile adhesion strength when formed in a straight line in a plan view is applied.

Description

Technical Field

[0001] The present invention relates to a method for repairing an existing concrete floor slab and a repair structure for an existing concrete floor slab.

Background Art

[0002] As the aging of road bridge floor slabs progresses, among repair works, there is a widely known method of thickening the upper surface of the floor slab to repair and reinforce the existing concrete floor slab by removing the damaged part of the existing concrete floor slab and then placing new concrete to increase the thickness. In the method of thickening the upper surface of the floor slab, ultra-high early strength steel fiber reinforced concrete (SFRC: Steel Fiber Reinforced Concrete) is adopted, which can be expected to have effects such as crack suppression effect, increase in flexural and tensile strength, and toughness improvement effect for the newly placed concrete.

[0003] However, for steel fiber reinforced concrete (SFRC), after shot blasting the upper surface of the existing concrete floor slab where the paving has been cut, it is placed in a predetermined range where an adhesive has been applied on a frame in advance, and after applying an adhesive to the formed vertical joint surface, the subsequent steel fiber reinforced concrete (SFRC) is then placed continuously. When using an adhesive in this way, there are problems in workability, such as the need to carry out the joint placement process within a limited pot life.

[0004] In addition, since the adhesive is an organic material, it is inferior in durability compared to concrete, which is an inorganic material. Therefore, using an adhesive easily causes the purpose of construction to be a cause of re-deterioration. Under such circumstances, in recent years, instead of steel fiber reinforced concrete (SFRC), for example, as shown in Patent Document 1, there has been a case of adopting an ultra-high performance fiber reinforced cement-based composite material (UHPFRC: Ultra-High Performance Fiber Reinforced Cement-based Composite) having high strength and tightness.

Prior Art Documents

Patent Documents

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-172751 [Overview of the project] [Problems that the invention aims to solve]

[0006] By adopting ultra-high performance fiber-reinforced cement composite materials (UHPFRC), higher tensile bond strength can be obtained in construction joints than with steel fiber-reinforced concrete (SFRC), thus eliminating the need for adhesives. Furthermore, compared to conventional steel fiber-reinforced concrete (SFRC), it is not only less susceptible to deterioration such as reduced load-bearing capacity due to crack propagation and soil formation of the surface layer, but is also known as a dense material with a low permeability coefficient. Therefore, it is expected that the waterproofing layer laid between the composite material and the asphalt pavement can be omitted.

[0007] However, in a plan view, a straight construction joint has a tensile bond strength that is inferior to the tensile strength of the base material. Therefore, if the aforementioned construction joint is located within a region where a tensile force greater than the tensile bond strength of the construction joint acts, there is a concern that cracking, opening, and a resulting decrease in watertightness may occur. Thus, even when using ultra-high performance fiber-reinforced cement composite materials (UHPFRC), the construction joint can become a weak point, making it difficult to obtain the benefit of omitting the waterproofing layer.

[0008] The present invention has been made in view of the above problems, and its main objective is to improve the tensile performance of a replacement material layer having construction joints while ensuring workability in road bridge repair work in which an existing concrete deck is repaired by providing a replacement material layer on the upper surface. [Means for solving the problem]

[0009] To achieve this objective, the present invention provides a repair method for existing concrete slabs, comprising the steps of: performing a joint treatment on the upper surface of the existing concrete slab after cutting the existing pavement layer, and then pouring replacement material onto the joint treatment surface to create a replacement material layer, wherein the repair method includes the steps of: pouring the preceding replacement material onto the joint treatment surface to form a vertical joint surface; and pouring the subsequent replacement material onto the vertical joint surface to form a replacement material layer having construction joints, wherein the replacement material is an ultra-high performance fiber-reinforced cement composite material, and when the construction joint is located in a region where a tensile force greater than the tensile bond strength when formed in a straight line in a plan view acts, the construction joint is formed in an uneven shape with straight sections that intersect the joint direction in a plan view.

[0010] The present invention provides a repair method for existing concrete slabs, characterized in that the vertical construction joint surface is shaped by a series of parallel arrangements of roughly triangular wedge-shaped protrusions, thereby forming the construction joint into an uneven shape with straight sections intersecting the joint direction in a plan view.

[0011] The present invention provides a repair method for existing concrete slabs, wherein the compressive strength of the replacement material at 28 days is 100 N / mm². 2 The above is the characteristic feature.

[0012] The present invention relates to a repair method for existing concrete slabs, characterized by roughening the vertical joint surface and making it wet, and then pouring the replacement material in place.

[0013] The present invention relates to a repair structure for an existing concrete slab, wherein after cutting the existing pavement layer, a joint treatment is performed on the upper surface of the existing concrete slab, which is then subjected to a surface treatment and kept wet, and a replacement material layer is provided by pouring replacement material onto the joint treatment surface, wherein the replacement material layer has a construction joint formed by pouring the preceding replacement material onto the joint treatment surface to form a vertical joint surface, and then pouring the subsequent replacement material into the joint, and the construction joint is formed in an uneven shape with straight sections that intersect the joint direction in a plan view when it is located in a region where a tensile force greater than the tensile bond strength when formed in a straight line in a plan view is acting on the construction joint.

[0014] The repair structure for existing concrete slabs of the present invention is characterized in that the construction joint is formed in an uneven shape with straight sections that intersect in the direction of the joint when viewed from above, by arranging the vertical construction joint surface in a continuous parallel manner with approximately triangular wedge-shaped projections.

[0015] According to the repair method and repair structure for existing concrete slabs of the present invention, in a replacement material layer formed by casting a replacement material made of an ultra-high-performance fiber-reinforced cement-based composite material onto the upper surface of an existing concrete slab, if the construction joint is located in a region where a tensile force greater than the tensile adhesion strength when formed in a straight line in a plan view acts, the construction joint is formed into an uneven shape with straight sections that intersect the joint direction in a plan view. In this way, in addition to adhesion resistance, shear resistance acts on the construction joint, so that performance equal to or greater than the tensile strength of the ultra-high-performance fiber-reinforced cement-based composite material which is the base material can be ensured.

[0016] This prevents cracking, joint separation, and the resulting decrease in watertightness, thus ensuring that the construction joints do not become a weak point in the replacement material layer. Consequently, the entire replacement material layer can be made as durable as the base material, making it possible to directly pave the top surface of the replacement material layer without the need for a waterproofing layer. Furthermore, by omitting the waterproofing layer, which has a relatively short lifespan of about 30 years, it becomes possible to extend the lifespan of road bridge decks.

[0017] Furthermore, if the waterproof layer can be omitted, not only will the work related to the laying of the waterproof layer, such as the grinding of the replacement material layer, become unnecessary, but the construction can proceed without being affected by the weather. Also, among the construction joints formed in the replacement material layer, those located in regions where the acting tensile force is smaller than the tensile adhesion strength when formed linearly in plan view do not need to have a concave-convex shape and can remain linear.

[0018] Thus, since the construction joints can be appropriately selected in plan view according to their arrangement positions, compared with the case where all the construction joints formed in the replacement material layer are made into a concave-convex shape with straight portions intersecting in the joint direction, the construction effort can be significantly reduced. Therefore, it becomes possible to improve the workability and shorten the construction period while making the replacement material layer with construction joints have a structure without weaknesses.

Advantages of the Invention

[0019] According to the present invention, when the construction joints of the replacement material layer provided on the upper surface of the existing concrete floor slab are located in a region where a tensile force greater than the tensile adhesion strength acts, it has a simple structure formed into a concave-convex shape with straight portions intersecting in the joint direction. Even for a replacement material layer having construction joints, it is possible to ensure workability and, at the same time, ensure tensile performance equivalent to that of the base material as a whole.

Brief Description of the Drawings

[0020] [Figure 1] It is a diagram showing a repair method for an existing concrete floor slab according to an embodiment of the present invention. [Figure 2] It is a diagram showing a blending example of a replacement material according to an embodiment of the present invention. [Figure 3] It is a diagram showing a construction joint by a linear vertical joint surface according to an embodiment of the present invention. [Figure 4] [Figure 5] It is a diagram showing a concave-convex construction joint with straight portions intersecting in the joint direction according to an embodiment of the present invention. [Figure 6] It is a plan view of the replacement material layer of an embodiment of the present invention. [Figure 7] It is a view showing another example of a road bridge of an embodiment of the present invention. [Figure 8] It is a view showing the end treatment of an existing concrete floor slab of an embodiment of the present invention.

Embodiment for Carrying out the Invention

[0021] The present invention aims to ensure the same tensile performance as the base material for the entire replacement material layer with construction purposes in the repair work of a road bridge that adopts the floor slab top thickening method to repair an existing concrete floor slab. Hereinafter, the repair method of the existing concrete floor slab and the repair structure of the existing concrete floor slab based on the floor slab top thickening method of the present invention will be described in detail while referring to FIGS. 1 to 8.

[0022] ≪≪≪Repair Method of Existing Concrete Floor Slab≫≫≫ As shown in FIG. 1(a), on the upper surface of the existing concrete floor slab 10 of the road bridge floor slab 100, a waterproof layer 20 and an asphalt layer 30 are laminated. In the repair work of the road bridge floor slab 100, the process of repairing and strengthening the existing concrete floor slab 10 is carried out in the following steps based on the floor slab top thickening method.

[0023] ≪≪Cutting Process of Existing Concrete Floor Slab≫≫ First, as shown in FIG. 1(b), the waterproof layer 20 and the asphalt layer 30 are cut, and surface treatment such as hanging (for example, by water jet) is performed on the cut surface, and joint treatment is performed in a wet state. Thus, a horizontal joint surface 11 is formed on the existing concrete floor slab 10.

[0024] ≪≪Placement Process of Preceding Replacement Material≫≫ Next, as shown in Figure 1(c), the preceding replacement material 41a is poured onto the horizontal construction joint surface 11 within a predetermined range. In the deck slab upper surface thickening method, steel fiber reinforced concrete (hereinafter referred to as SFRC) is generally used as the replacement material 41, but in this embodiment, an ultra-high performance fiber-reinforced cement composite material is adopted.

[0025] ≪Ultra-high performance fiber-reinforced cement composite material: UHPFRC≫ Ultra-high performance fiber-reinforced cement composites (hereinafter referred to as UHPFRC) are ultra-high-strength cement-based materials composed of a specially mixed cement, short fibers, fine aggregate, admixtures, and water, and generally have a compressive strength of 100 N / mm². 2 The above refers to the following. Compared to the above-mentioned SFRC, UHPFRC is less susceptible to deterioration such as a decrease in load-bearing capacity due to crack propagation and soil formation of the surface layer. Furthermore, because it is a dense material with a low permeability coefficient, the infiltration of chlorides and water is limited to the surface layer.

[0026] In this embodiment, the formulation shown in Figure 2 is used as a basis, and includes a premix material consisting of Portland cement, pozzolanic material, inorganic powder, aggregate with a particle size of 5 mm or less, a fast-hardening agent, an expansive agent, a high-performance water-reducing agent, a retarder, water, and short fibers. The short fibers include, for example, a diameter of 0.16 mm, a length of 13 mm, and a tensile strength of 2700 N / mm². 2 We will use steel fibers and incorporate 2.0 vol% of these steel fibers into the mixture.

[0027] Expansion agents are not necessarily required. On the other hand, a rapid-setting agent is added to achieve early strength development, and retarders and high-performance water-reducing agents are added to adjust pot life and fluidity. For example, if the mixture is formulated so that the mortar flow is between 150 mm and 280 mm (JIS R 5201 "Physical Test Methods for Cement"), as shown in Figure 1(c), fluidity is maintained when pouring onto the upper surface of the horizontal construction joint surface 11 formed on the existing concrete slab 10, but after pouring, it becomes difficult to flow. As a result, even if the slope of the horizontal construction joint surface 11 is about 5 to 10%, it is possible to finish the replacement material layer 40 while suppressing the flow of the replacement material 41 along the slope.

[0028] Furthermore, in this embodiment, the compressive strength at 3 hours of age is 24 N / mm². 2 The above adhesive strength is 1.0 N / mm². 2 In summary, the compressive strength at 28 days of age was 120 N / mm². 2 In summary, the crack initiation strength is 6.0 N / mm². 2 The UHPFRC exhibiting the above characteristics is used as replacement material 41. The compressive strength is based on JIS A 1108 "Test method for compressive strength of concrete", the adhesive strength is based on JIS A 1171 "Test method for polymer cement mortar", and the crack initiation strength is based on JIS A 1113 "Test method for splitting tensile strength of concrete".

[0029] As shown in Figure 1(c), the preceding replacement material 41a having the above configuration is cast onto the horizontal joint surface 11 within a predetermined area, and then cured for a predetermined time to harden. Once hardened, a vertical joint surface 42 is formed on the side surface of the preceding replacement material 41a. This vertical joint surface 42 is then roughened using shot blasting or a water jet, followed by a joint treatment to create a wet state. The plan view shape of the vertical joint surface 42 will be described later.

[0030] <<The process of pouring replacement materials for the subsequent pouring>> Next, as shown in Figure 1(d), the subsequent replacement material 41b is poured in, adhering it to the vertical joint surface 42 that has undergone joint treatment. The subsequent replacement material 41b is the same material as the preceding replacement material 41a. This process is repeated to form a replacement material layer 40 with construction joints 43 on the horizontal joint surface 11 formed on the upper surface of the existing concrete slab 10.

[0031] ≪≪Paving Process≫≫ As mentioned above, UHPFRC is a dense material with a low permeability coefficient. Therefore, by using UHPFRC as the replacement material 41, as shown in Figure 1(e), the new asphalt pavement 50 can be laid directly on the top surface of the hardened replacement material layer 40, eliminating the need for a waterproofing layer.

[0032] <<<Plan view shape of the construction joint (vertical construction joint surface)>>> By the way, in the replacement material layer 40 constructed by the procedure described above, the construction joints 43 formed in a straight line in a plan view, as shown in Figure 3(a), may become a weak point of the replacement material layer 40 depending on their placement.

[0033] For example, if the road bridge deck 100 is the superstructure of a hollow deck bridge 200 with three continuous spans as shown in Figure 4(a), then, as shown in Figure 4(b), a negative bending moment is generated in predetermined areas A1 and A2 including the two intermediate support points P2 and P3, and a tensile force is introduced to the upper surface of the existing concrete deck 10, which is an integral structure with the girder. Although the tensile strength of the replacement material 41 is designed to be greater than this tensile force, the tensile bond strength of the construction joint 43, which is formed in a straight line in plan view, may be less than the tensile force introduced to the upper surface of the existing concrete deck 10, as shown in Figure 3(b).

[0034] Consequently, if a construction joint 43, formed in a straight line in plan view and extending perpendicular to the bridge axis, is located in predetermined regions A1 and A2 where a negative bending moment occurs, there is a risk of cracks or gaps forming near the construction joint 43. Furthermore, there is concern about a decrease in watertightness due to these factors, making the construction joint 43 a weak point of the replacement material layer 40. Therefore, when a construction joint 43 is located in such a position, its plan view shape is formed into a sawtooth shape to ensure performance equivalent to or better than the tensile strength of the replacement material 41.

[0035] Specifically, in the process shown in Figure 1(c), the vertical joint surface 42 is formed into a shape in which multiple approximately triangular wedge-shaped projections 421 are arranged in a continuous manner in the direction of the joint, as shown in Figures 5(a) and (b). Any approximately triangular shape can be used for the wedge-shaped projections 421, but it is preferable that the dimensions of the base b and the projection height h are approximately the same, as shown in Figure 5(b). Further details are provided in Japanese Patent No. 7366806.

[0036] By forming multiple such roughly triangular wedge-shaped projections 421 in a continuous manner in the joint direction, and by making the plan view shape of the construction joint 43 a sawtooth shape, the length of the joint itself becomes longer compared to when it is straight in plan view, thus increasing the number of short fibers that cross-link with the subsequent replacement material 41b. Furthermore, as shown in Figure 5(b), the tensile force (in the lateral direction on the plane of the paper) acting between the vertical joint surface 42 and the subsequent replacement material 41b that is joined thereto can be resisted by the resultant force of adhesion resistance and shear resistance.

[0037] This makes it possible to ensure that the construction joint 43 has tensile strength equivalent to or greater than that of the replacement material 41. Therefore, even if the construction joint 43 is located in predetermined regions A1 and A2 where negative bending moments occur, it will not become a weak point in the replacement material layer 40. With this simple structure, even when the construction joint 43 is present, the entire replacement material layer 40 can have tensile strength equivalent to that of the base material, the replacement material 41.

[0038] The process of creating a sawtooth shape in plan view of such construction joints 43 is the same not only when the construction joints 43 extend perpendicular to the bridge axis, but also when they extend in the direction of the bridge axis. For example, as shown in Figure 4(c), when the hollow slab bridge 200 is viewed from the direction of the bridge axis, a negative bending moment is generated in predetermined areas B1 and B2 including the base end of the cantilevered portion 12 of the existing concrete slab 10, and a tensile force is introduced to the upper side.

[0039] Consequently, even in the predetermined regions B1 and B2, the tensile force acting on the upper surface of the existing concrete slab 10 may exceed the tensile adhesion strength of the construction joint 43, which is formed in a straight line in a plan view and extends in the direction of the bridge axis. For this reason, even when forming construction joints 43 of the replacement material layer 40 in the predetermined regions B1 and B2, the construction joints 43 are formed in a sawtooth shape in a plan view, as shown in Figures 5(a) and (b).

[0040] As a result, when the replacement material layer 40 is viewed in plan view, as shown in Figure 6, the construction joints 43 extending perpendicular to the bridge axis in a predetermined region A2 where a negative bending moment occurs, and the construction joints 43 extending in the bridge axis direction in predetermined regions B1 and B2, are formed in a sawtooth shape in plan view. Note that predetermined region A1 is not shown in the figure.

[0041] On the other hand, for example, the construction joint 43 extending in the bridge axis direction located between predetermined areas B1 and B2 is formed in a straight line in plan view. As shown in Figure 4(b), these are within the range of positive bending moment, and even if a tensile force acts on the upper surface of the existing concrete deck slab 10, it is estimated that its magnitude will be less than the tensile bond strength of the construction joint 43 formed in a straight line in plan view. Therefore, it is not necessary to make the plan view shape of the construction joint 43 a sawtooth shape. In this way, the plan view shape of the construction joint 43 can be selected according to its placement, and construction work can be significantly reduced compared to the case where all construction joints 43 are formed in a sawtooth shape in plan view.

[0042] Furthermore, the practice of forming the construction joint 43 into a sawtooth shape in plan view is not limited to cases where the construction joint 43 is located in predetermined regions A1-A2 and B1-B2 where a negative bending moment occurs. If, for any reason, the tensile force acting on the upper surface of the existing concrete slab 10 may exceed the tensile bond strength of a construction joint 43 formed in a straight line in plan view, the construction joint 43 in that region shall be formed into a sawtooth shape in plan view.

[0043] Therefore, by planning the construction so that construction joints 43 are placed in the above-mentioned area as little as possible, it is possible to further improve constructability.

[0044] According to the present invention, even when construction joints 43 are present, it is possible to ensure tensile performance equivalent to that of the base material UHPFRC throughout the entire replacement material layer 40, so that the waterproofing layer 20 can be omitted, as shown in Figure 1(e). This eliminates the need for waterproofing work such as sanding the replacement material layer 40, and allows construction to proceed regardless of weather conditions.

[0045] Therefore, it becomes possible to improve workability and shorten the construction period while creating a structure without weaknesses in the replacement material layer 40 where the construction joints 43 exist. Furthermore, by omitting the waterproofing layer 20, which has a relatively short lifespan of about 30 years, it becomes possible to extend the lifespan of the road bridge deck 100 after the repair work.

[0046] The method for repairing existing concrete slabs and the repair structure for existing concrete slabs of the present invention are not limited to the embodiments described above, and it goes without saying that various modifications are possible without departing from the spirit of the present invention.

[0047] For example, in this embodiment, a hollow slab bridge 200 as shown in Figure 4 was used as an example to explain the concrete repair method, but it can be applied to any road bridge with I-shaped, T-shaped, or other types of bridge girders. For example, in the case of a road bridge 300 as shown in Figure 7, a negative bending moment is generated in predetermined regions C1 to C5, which include each of the five I-shaped bridge girders 310, and a tensile force is introduced to the upper surface of the existing concrete slab 10. Therefore, when construction joints 43 are placed in these predetermined regions C1 to C5, their planar shape should be a sawtooth shape.

[0048] Furthermore, in this embodiment, as shown in Figures 5(a) and (b), the vertical joint surface 42 is formed in a shape in which a plurality of approximately triangular wedge-shaped projections 421 are continuously arranged in the joint direction, thereby illustrating a case in which the construction joint 43 is formed in a sawtooth shape in plan view. However, the construction joint 43 may be formed in any shape as long as it has an uneven shape with straight sections that intersect in the joint direction in plan view. In other words, as long as adhesion resistance and shear resistance are applied between the vertical joint surface 42 and the subsequent replacement material 41b, and the construction joint 43 can be formed in any shape as long as it can have performance equivalent to or better than the tensile strength of the base material.

[0049] Furthermore, as shown in Figures 8(a) to (c), if a fiber-reinforced layer 60 using replacement material 41 is provided on the surface of existing structures 15 such as wall railings 13 and curb 14, the waterproofing layer can be omitted even at the edges of the existing concrete slab 10.

[0050] Specifically, as shown in Figure 8(a), first, the end of the existing concrete slab 10 is cut deeper than the horizontal joint surface 11 to form a recess 11a. Next, as shown in Figure 8(b), replacement material 41 is poured into the recess 11a to the same height as the horizontal joint surface 11 to form a filling layer 44. After that, a reinforcing member 45 is laid on the upper surface of the filling layer 44, and replacement material 41 is poured onto the upper surface of the horizontal joint surface 11 so as to embed one end of the reinforcing member 45, thereby forming a replacement material layer 40.

[0051] Then, as shown in Figure 8(c), the replacement material 41 is poured so as to cover the inner surfaces of the wall parapet 13 and the curb 14, and embed the other end of the reinforcing member 45, thereby providing a fiber reinforcement layer 60. In Figures 8(b) and (c), the case in which reinforcing steel is used as the reinforcing member 45 is shown as an example, but it is not limited to this, and any material that is generally used as a material to reinforce concrete structures can be used.

[0052] Furthermore, in this embodiment, we have given an example of a case in which the replacement material layer 40 is provided on the existing concrete slab 10 without changing the thickness of the existing concrete slab 10, but we are not limited to this. After cutting the asphalt layer 30 and the waterproofing layer 20, the existing concrete slab 10 may be chipped away with a water jet to the thickness of the replacement material layer 40. In this way, the upper surface of the replacement material layer 40 can be formed at the same height as the upper surface of the existing concrete slab 10 before the repair work was carried out. [Explanation of Symbols]

[0053] 10 Existing concrete slab 11. Horizontal joint surface (joint treatment surface) 11a Recess 12. Protruding section 13 Wall railing 14 Earth Cover 15 Existing structures 20 waterproof layer 30. Asphalt layer (existing pavement layer) 40 Replacement material layer 41 Replacement materials 41a Preceding replacement materials 41b Substitute materials for the later round 42 Vertical joint surface 43 Construction joints 44 Filled bed 45 Reinforcement members 50 New asphalt pavement 60 Fiber-reinforced layer 100 Road bridge deck 200 Hollow slab bridge 300 Road Bridges 310 Bridge girder A1, A2 Predetermined area including intermediate support points B1, B2 Predetermined area including protruding parts C1~C5 Predetermined area including bridge girders

Claims

1. A repair method for existing concrete slabs, which involves cutting the existing pavement layer, performing a surface treatment and moistening joint treatment on the upper surface of the existing concrete slab, and then pouring replacement material onto the treated joint surface to create a replacement material layer. A step of forming a vertical joint surface by pouring the preceding replacement material onto the joint surface, The process includes the step of joining the subsequent replacement material to the vertical joint surface to form the replacement material layer having a construction joint, The aforementioned replacement material is an ultra-high-performance fiber-reinforced cement-based composite material. A repair method for existing concrete slabs, characterized in that when the construction joint is located in a region where a tensile force greater than the tensile bond strength when formed in a straight line in a plan view is applied, the joint is formed in an uneven shape with straight sections that intersect the joint direction in a plan view.

2. In the repair method for an existing concrete slab described in claim 1, A repair method for an existing concrete slab, characterized in that the vertical construction joint surface is shaped in such a way that approximately triangular wedge-shaped projections are arranged in parallel, thereby forming the construction joint into an uneven shape with straight sections intersecting the joint in a plan view.

3. In the repair method for an existing concrete slab described in claim 1, The compressive strength of the aforementioned replacement material at 28 days of age is 100 N / mm². ２ A repair method for existing concrete slabs, characterized by the above.

4. In the repair method for an existing concrete slab described in claim 1, A repair method for an existing concrete slab, characterized by roughening the surface of the vertical joint and making it wet, and then pouring the replacement material in the subsequent pour.

5. A repair structure for an existing concrete slab, which involves cutting the existing pavement layer, performing a surface treatment and moistening joint treatment on the upper surface of the existing concrete slab, and then pouring replacement material onto the treated joint surface to create a replacement material layer. The aforementioned replacement material layer is The construction joint is formed by first pouring the replacement material onto the joint surface to form a vertical joint surface, and then pouring the replacement material onto the joint surface. The repair structure for an existing concrete slab is characterized in that, when the construction joint is located in a region where a tensile force greater than the tensile bond strength when formed in a straight line in a plan view is applied, the construction joint is formed in an uneven shape with straight sections that intersect the joint direction in a plan view.

6. In the repair structure for an existing concrete slab according to claim 5, A repair structure for an existing concrete slab, characterized in that the construction joint is formed in an uneven shape with straight sections intersecting the joint direction in a plan view, by arranging the vertical construction joint surface in a continuous parallel manner with approximately triangular wedge-shaped projections.

Images