New and old concrete composite connecting structure and construction method

Abstract

The invention discloses a new and old concrete composite connecting structure and a construction method. The new and old concrete composite connecting structure comprises an old concrete structure, a concrete transition layer and a new concrete structure. A concave-convex interface and a grid structure are arranged between the old concrete structure and the concrete transition layer; a three-dimensional anchoring part is further arranged between the old concrete structure and the concrete transition layer, the three-dimensional anchoring part comprises a straight pipe and a plurality of branch pipes, and the gaps between the outer wall of the straight pipe and the side walls of the holes, the straight pipe and the branch pipes are filled with epoxy resin; steel fibers and nano silicon dioxide are added into concrete of the concrete transition layer. According to the three-dimensional anchoring part, the corrugated pipe and the epoxy resin are combined to form a rigid-flexible combination body, so that stress dispersion is more uniform, the shear strength is improved, and the self weight of the structure is reduced. The steel fibers and the nano silicon dioxide are added into the concrete of the concrete transition layer, so that the toughness and the strength of the concrete can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of construction engineering, and particularly to a composite connection structure and construction method for new and old concrete, which are applicable to projects such as building renovation and bridge reinforcement Background Art

[0002] The main methods for connecting new and old concrete include planting steel bars, direct lap joint, anchoring connection, embedded steel bars or connectors, etc. Existing connections between new and old concrete often use chiseling, steel bar planting or interface agent treatment. The surface of the old concrete is treated by chiseling to increase its roughness, which is beneficial to the adhesion of the new concrete. However, the existing processes still have problems such as insufficient interfacial bonding force and easy generation of peeling cracks

[0003] Therefore, there is an urgent need for a treatment process for new and old concrete structures with strong interfacial bonding force and good coordination between steel bars and concrete Summary of the Invention

[0004] Aiming at the problems of insufficient interfacial bonding force and easy generation of peeling cracks in the existing connection between new and old concrete, the present invention provides a composite connection structure and construction method for new and old concrete to solve the above problems

[0005] To solve the above technical problems, the present invention includes the following technical solutions

[0006] A composite connection structure for new and old concrete, comprising an old concrete structure, a concrete transition layer and a new concrete structure

[0007] The interface between the old concrete structure and the concrete transition layer is a serrated concave-convex interface, and a grid structure is arranged on the concave-convex interface

[0008] A three-dimensional anchor is further arranged between the old concrete structure and the concrete transition layer. The three-dimensional anchor includes a straight pipe and a plurality of fork pipes communicated with one end of the straight pipe. A part of the straight pipe is implanted into the old concrete structure through drilling, and the other part of the straight pipe and the fork pipes are poured into the concrete transition layer; epoxy resin is filled in the gap between the outer wall of the straight pipe and the hole side wall, and in the straight pipe and the fork pipes; one end of one of the fork pipes is open and serves as an injection port for epoxy resin

[0009] Steel fibers and nano-silica are added to the concrete of the concrete transition layer

[0010] Further, the grid structure adopts a carbon fiber grid

[0011] Further, an elastic sealing ring is sleeved on the straight pipe, the elastic sealing ring plugs the end of the drilling hole of the old concrete structure, and an exhaust hole is arranged at the top of the elastic sealing ring

[0012] Further, a valve is provided inside the exhaust hole, which can be opened when the pressure inside the drill hole is greater than a certain value.

[0013] Further, the three-dimensional anchor includes four radially positioned fork pipes, and the orthographic projection of the fork pipes is in a cross shape.

[0014] Further, the mass ratios of the added steel fibers and nano-silica are respectively: 1.5% steel fibers and 0.2% nano-silica.

[0015] Correspondingly, the present invention also provides a construction method for the new and old concrete composite connection structure described above, including the following steps:

[0016] Step 1: Rough the surface of the old concrete until the coarse aggregates are exposed, drill holes vertically on the surface of the old concrete, and remove the debris and powder on the surface and inside the holes of the old concrete;

[0017] Step 2: Lay a grid structure on the surface of the old concrete, implant the straight pipe of the three-dimensional anchor into the hole, inject epoxy resin into the injection holes of the fork pipes, so that the epoxy resin fills the fork pipes and the straight pipe, and the epoxy resin flows out from the overflow holes at the end of the straight pipe and reversely fills the gap between the outer wall of the straight pipe and the hole side wall;

[0018] Step 3: Apply an interface agent and construct a concrete transition layer, and the concrete transition layer covers the grid structure and the three-dimensional anchor;

[0019] Step 4: Construct a new concrete structure.

[0020] Further, in Step 1, rough the surface of the old concrete until the coarse aggregates are exposed, specifically by using high-pressure water jet to scour the surface of the old concrete to form a serrated concave-convex interface.

[0021] Further, the grid structure uses a carbon fiber grid, which is adhered to the surface of the old concrete by glue.

[0022] Further, an elastic sealing ring is sleeved on the straight pipe of the three-dimensional anchor. When the straight pipe of the three-dimensional anchor is implanted into the hole, the elastic sealing ring is stuffed into the end of the drill hole, so as to form a relatively closed space inside the drill hole and be able to fix the three-dimensional anchor;

[0023] An exhaust hole is provided at the top of the elastic sealing ring. When epoxy resin is injected into the injection hole, air is discharged from the exhaust hole. When epoxy resin overflows from the exhaust hole, stop injecting epoxy resin.

[0024] Due to the adoption of the above technical solutions, the present invention has the following advantages and positive effects compared with the prior art: By arranging three-dimensional anchors between the old concrete structure and the concrete transition layer, and forming a rigid-flexible combination with the corrugated pipe-epoxy resin for the three-dimensional anchors, the stress dispersion is more uniform, and the fatigue life under dynamic loads is increased by 3-5 times; after the epoxy resin is cured, it works synergistically with the corrugated pipe. Compared with the single implanted steel bar structure, the compressive strength can be increased by 1.8 times; the weight of the corrugated pipe-epoxy resin combination structure is reduced by 30-40% under the same bearing capacity compared with ordinary steel bars, which can significantly reduce the self-weight of the structure; the epoxy resin forms a chemical protection layer, which can effectively isolate the stainless steel corrugated pipe from corrosive media, resist corrosion media such as chloride ions, acids and alkalis, prevent the erosion of acids, alkalis, salt solutions, etc. on metals, and the salt spray corrosion resistance is improved by a large margin, and it is suitable for harsh environments such as ocean engineering and chemical plants. By adding steel fibers and nano-silica in the concrete of the concrete transition layer, the steel fibers can improve the toughness of the concrete and the tensile and crack resistance performance of the concrete, and the nano-silica can improve the strength of the concrete and the ability of the concrete to bear loads. Through the comprehensive action of arranging a grid structure and three-dimensional anchors between the old concrete structure and the concrete transition layer, filling epoxy resin, and adding steel fibers and nano-silica in the concrete of the concrete transition layer, etc., the shear strength of the new-old concrete composite connection structure is greatly improved compared with the traditional rebar implantation method, and the grid structure works synergistically with the corrugated pipe, and the crack width control can also meet the specification requirements, and it also has the advantages of simple construction and convenient operation. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of the new-old concrete composite connection structure in an embodiment of the present invention;

[0026] Figure 2 It is a front view of the grid structure and three-dimensional anchors in an embodiment of the present invention;

[0027] Figure 3 It is a side view of the three-dimensional anchor and the elastic sealing ring in an embodiment of the present invention;

[0028] Figure 4 It is a front view of the three-dimensional anchor and the elastic sealing ring in an embodiment of the present invention;

[0029] Figure 5 It is a front view of the elastic sealing ring in an embodiment of the present invention.

[0030] The reference numerals in the figure are as follows:

[0031] 1 - Old concrete structure; 2 - Concrete transition layer; 3 - New concrete structure; 4 - Concave-convex interface; 5 - Grid structure; 6 - Three-dimensional anchor; 61 - Straight pipe; 62 - Fork pipe; 63 - Injection hole; 64 - Overflow hole; 65 - Elastic sealing ring; 66 - Vent hole; 67 - Valve. Detailed implementation mode

[0032] The following further describes in detail a new-old concrete composite connection structure and construction method provided by the present invention in combination with the accompanying drawings and specific embodiments. In combination with the following description, the advantages and features of the present invention will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for conveniently and clearly assisting in explaining the purpose of the embodiments of the present invention.

[0033] Embodiment 1

[0034] As Figure 1 shown, the new-old concrete composite connection structure provided in this embodiment includes an old concrete structure 1, a concrete transition layer 2, and a new concrete structure 3.

[0035] Combined with Figure 1 and Figure 2 shown, there is a concave-convex interface 4 between the old concrete structure 1 and the concrete transition layer 2, and a grid structure 5 is arranged on the concave-convex interface 4. The production method of the concave-convex interface 4 is to use a high-pressure water jet to wash the surface of the old concrete structure 1 until the coarse aggregate is exposed. For example, the water pressure of the high-pressure water jet is greater than or equal to 30 MPa. Of course, the chiseling method can also be used for treatment. The grid structure 5 can adopt a carbon fiber grid. As an example, the carbon fiber diameter is 3 - 5 mm, the grid spacing is 50 mm × 50 mm, the carbon fiber grid is pasted on the concave-convex interface 4, and is covered by pouring the concrete of the concrete transition layer 2. The carbon fiber grid can effectively reduce the additional stress caused by early shrinkage between the old concrete structure 1 and the concrete transition layer 2, and reduce the possibility of the concrete structure generating cracks.

[0036] Combined with Figures 1 to 4 shown, a three-dimensional anchor 6 is also arranged between the old concrete structure 1 and the concrete transition layer 2. The three-dimensional anchor 6 includes a straight pipe 61 and several fork pipes 62 communicated with one end of the straight pipe 61. A part of the straight pipe 61 is implanted into the old concrete structure 1 through drilling, and the other part of the straight pipe 61 and the fork pipes 62 are poured into the concrete transition layer 2. As an example, 4 fork pipes 62 are arranged, which are radially distributed. Each fork is arranged at four azimuths of 0°, 90°, 180°, and 270° in the vertical direction. The length of the fork pipe 62 is 80 mm, the included angle between the fork pipe 62 and the center line of the straight pipe 61 is greater than 10° and less than 50°, and the length of the straight pipe 61 inserted into the old concrete structure 1 is 150 mm.

[0037] Combined with Figure 3 andFigure 4 As shown, an injection hole 63 is provided at the end of the cross pipe 62 in the vertical direction of 0°, which is used for injecting epoxy resin, and an overflow hole 64 is provided at the upper position of the end of the straight pipe 61. After the straight pipe 61 of the three-dimensional anchor 6 is implanted into the hole of the old concrete structure 1, epoxy resin is injected through the injection hole 63. The epoxy resin fills the inner cavities of the straight pipe 61 and the cross pipe 62, and overflows through the overflow hole 64 to fill the gap between the outer wall of the straight pipe 61 and the hole side wall. As an example, the three-dimensional anchor 6 is made of a stainless steel corrugated pipe with an inner diameter of 10 mm, a wall thickness of 1 mm, and a material of SUS304. After the epoxy resin solidifies, its compressive strength is ≥60 MPa. In this embodiment, the three-dimensional anchor 6 adopts a corrugated pipe-epoxy resin composite structure. The stainless steel corrugated pipe provides a physical barrier, and the epoxy resin forms a chemical protection layer, which can effectively isolate the metal from contact with corrosive media, resist corrosion media such as chloride ions, acids and alkalis, prevent the erosion of acids, alkalis, salt solutions, etc. on the metal, and greatly improve the salt spray corrosion resistance, and is suitable for harsh environments such as ocean engineering and chemical plants. Moreover, the combination of the corrugated pipe and the epoxy resin forms a rigid-flexible combination, which disperses stress more evenly, and the fatigue life under dynamic load is increased by 3-5 times. At the same time, after the epoxy resin cures, it acts synergistically with the corrugated pipe, and the local compressive strength can reach 1.8 times that of the pure steel bar structure. The corrugated pipe-epoxy resin composite structure reduces the weight by 30-40% compared with ordinary steel bars under the same load-bearing capacity, and can significantly reduce the structural self-weight.

[0038] Steel fibers and nano-silica are added to the concrete of the concrete transition layer 2. As an example, the mass ratios of the addition of steel fibers and nano-silica are: steel fibers 1.5%, nano-silica 0.2%. Steel fibers can improve the toughness of concrete and its tensile and crack resistance performance, and nano-silica can improve the strength of concrete and its ability to bear loads.

[0039] In a specific embodiment, in combination with Figures 1 to 5As shown, an elastic sealing ring 65 is sleeved on the straight tube 61, and the elastic sealing ring 65 blocks the end of the drilled hole of the old concrete structure 1. An exhaust hole 66 is provided at the top of the elastic sealing ring 65. After the epoxy resin overflows from the overflow hole 64, when it flows to the end of the drilled hole, it will flow out from the bottom of the straight tube 61, affecting the filling degree of the epoxy resin. The elastic sealing ring 65 will block the gap between the straight tube 61 and the side wall of the hole due to elastic deformation, preventing the epoxy resin from flowing out from the gap below the straight tube 61. By providing the exhaust hole 66, the gas in the closed cavity can be discharged, and after the epoxy resin is filled, it will also overflow from the exhaust hole 66, so whether there is epoxy resin in the exhaust hole 66 can be used as a test condition for whether the filling degree of the epoxy resin meets the requirements. Furthermore, a valve 67, such as a magnetic valve 67, can be provided in the exhaust hole 66. Only when the air is compressed to a certain pressure will the valve 67 be opened to discharge the air. After the air is discharged, the air pressure will decrease, and the valve 67 will close again under the action of its own weight and magnetic attraction. Similarly, only when the pressure of the epoxy resin reaches a certain value will the valve 67 be opened, so that the air can be discharged as much as possible and the density of the epoxy resin can be improved.

[0040] Embodiment 2

[0041] This embodiment provides a construction method of the new-old concrete composite connection structure, comprising the following steps:

[0042] Step 1: roughen the surface of the old concrete by high-pressure water jet until the coarse aggregate is exposed to form a concave-convex interface 4, vertically drill holes on the surface of the old concrete, and remove debris and powder on the surface of the old concrete and in the holes;

[0043] Step 2: Lay the grid structure 5 on the old concrete surface, implant one end of the straight tube 61 of the three-dimensional anchor 6 into the drilled hole, inject epoxy resin into the injection hole 63 of the fork tube 62, so that the epoxy resin fills the fork tube 62 and the straight tube 61, and the epoxy resin flows out from the overflow hole 64 at the end of the straight tube 61 and reversely fills the gap between the outer wall of the straight tube 61 and the side wall of the hole;

[0044] Step 3: Apply an interface agent, which may be composed of a cement-based permeable crystallization material and a silane coupling agent, and the interface agent may be applied twice; construct a concrete transition layer 2, which covers a grid structure 5 and a three-dimensional anchor 6; steel fibers and nano-silicon dioxide are added to the concrete of the concrete transition layer 2, which can improve the toughness and strength of the concrete and prevent the concrete from cracking;

[0045] Step 4: construct a new concrete structure 3. The new concrete structure 3 is poured in layers using self-compacting concrete, and during pouring, the distance between the vibrating rod and the interface is greater than or equal to 200 mm.

[0046] In a specific embodiment, the grid structure 5 is made of carbon fiber grid and adhered to the surface of the old concrete by glue.

[0047] In a specific embodiment, an elastic sealing ring 65 is sleeved on the straight pipe 61 of the three-dimensional anchor 6. When the straight pipe 61 of the three-dimensional anchor 6 is implanted into the hole, the elastic sealing ring 65 is stuffed into the end of the drilling hole, so as to form a relatively closed space in the drilling hole and be able to fix the three-dimensional anchor 6. An exhaust hole 66 is arranged at the top of the elastic sealing ring 65. When epoxy resin is injected into the injection hole 63, air is discharged from the exhaust hole 66. When epoxy resin overflows from the exhaust hole 66, the injection of epoxy resin is stopped.

[0048] The technical features of the above-described embodiments can be combined arbitrarily. For the sake of brevity of description, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, it should be considered as the scope recorded in this specification.

[0049] The above-described embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation on the scope of the invention. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the present invention should be subject to the appended claims.

Claims

1. A composite connection structure for new and old concrete, characterized in that It includes an old concrete structure, a concrete transition layer and a new concrete structure; The interface between the old concrete structure and the concrete transition layer is a serrated concave-convex interface, and a grid structure is arranged on the concave-convex interface; Three-dimensional anchor bolts are also arranged between the old concrete structure and the concrete transition layer. The three-dimensional anchor bolts include a straight pipe and several fork pipes communicated with one end of the straight pipe. A part of the straight pipe is implanted into the old concrete structure through drilling, and the other part of the straight pipe and the fork pipes are poured into the concrete transition layer; epoxy resin is filled in the gap between the outer wall of the straight pipe and the hole side wall, and in the straight pipe and the fork pipes; one end of one fork pipe is open and serves as the injection port of the epoxy resin; Steel fibers and nano-silica are added to the concrete of the concrete transition layer.

2. The new-old concrete composite connection structure according to claim 1, characterized in that The grid structure adopts a carbon fiber grid.

3. The new-old concrete composite connection structure according to claim 1, characterized in that An elastic sealing ring is sleeved on the straight pipe. The elastic sealing ring seals the end of the drilling hole of the old concrete structure, and an exhaust hole is arranged at the top of the elastic sealing ring.

4. The new-old concrete composite connection structure according to claim 3, characterized in that A valve is arranged in the exhaust hole and can be opened when the pressure in the drilling hole is greater than a certain value.

5. The new-old concrete composite connection structure according to claim 1, characterized in that The three-dimensional anchor bolts include four radially positioned fork pipes, and the orthographic projection of the fork pipes is in a cross shape.

6. The new-old concrete composite connection structure according to claim 1, characterized in that The mass ratios of the added steel fibers and nano-silica are respectively: 1.5% for steel fibers and 0.2% for nano-silica.

7. A construction method for the new and old concrete composite connection structure as described in claim 1, characterized in that, It includes the following steps: Step 1: Roughly chisel the surface of the old concrete until the coarse aggregate is exposed, vertically drill holes on the surface of the old concrete, and remove the debris and powder on the surface of the old concrete and in the holes; Step 2: Lay the grid structure on the surface of the old concrete, implant the straight pipe of the three-dimensional anchor bolt into the hole, inject epoxy resin into the injection hole of the fork pipe, so that the epoxy resin fills the fork pipe and the straight pipe, and the epoxy resin flows out from the overflow hole at the end of the straight pipe and fills the gap between the outer wall of the straight pipe and the hole side wall in the reverse direction; Step 3: Apply an interface agent and construct the concrete transition layer, and the concrete transition layer covers the grid structure and the three-dimensional anchor bolts; Step 4: Construct the new concrete structure.

8. The construction method of the new-old concrete composite connection structure according to claim 7, characterized in that In step 1, the surface of the old concrete is roughly chiseled until the coarse aggregate is exposed. Specifically, the surface of the old concrete is flushed with high-pressure water jets to form a serrated concave-convex interface.

9. The construction method of the new-old concrete composite connection structure according to claim 7, characterized in that The grid structure adopts a carbon fiber grid and is adhered to the surface of the old concrete through glue.

10. The construction method of the new-old concrete composite connection structure according to claim 7, characterized in that An elastic sealing ring is sleeved on the straight pipe of the three-dimensional anchor bolt. When the straight pipe of the three-dimensional anchor bolt is implanted into the hole, the elastic sealing ring is stuffed into the end of the drilling hole, so that a relatively closed space is formed in the drilling hole and the three-dimensional anchor bolt can be fixed; An exhaust hole is provided at the top of the elastic sealing ring. When epoxy resin is injected through the injection hole, air is discharged from the exhaust hole. When epoxy resin overflows from the exhaust hole, the injection of epoxy resin is stopped.

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