Hybrid fiber reinforced cementitious beam-column joint permanent form and method of making

Abstract

The application provides a hybrid fiber reinforced cement-based beam-column joint permanent formwork and a preparation method thereof. The permanent formwork is assembled by a hollow column permanent formwork and a U-shaped beam permanent formwork which are prepared from a hybrid fiber reinforced cement-based material. The hybrid fiber reinforced cement-based material comprises a hybrid cement-based material and a hybrid fiber grid located in the middle. The hybrid fiber grid is a hybrid fiber grid woven by dry fiber bundles and impregnated fiber bundles which are longitudinally and transversely distributed at intervals. The cement-based material contains at least two kinds of short-cut fiber filaments. The hybrid fiber grid at the port of the beam permanent formwork extends out. At the joint between the column permanent formwork and the beam permanent formwork, the hybrid fiber grids extending out from both are connected into one by an adhesive and are encapsulated by a hybrid fiber cement-based material. The permanent formwork of the technical scheme simplifies the construction process, shortens the construction period, increases the mechanical properties of the concrete structure and saves resources.

Description

Technical Field

[0001] This invention belongs to the field of building structure technology, and particularly relates to a permanent template for hybrid fiber-reinforced cement-based beam-column joints and its preparation method. Background Technology

[0002] In today's construction industry, concrete remains the most widely used artificial building material, and formwork is an indispensable part of the concrete shaping process, determining the construction efficiency, quality, and cost of concrete structures. Typically, concrete formwork accounts for 30%–50% of the total cost, 40%–50% of the labor, and about 50% of the construction period. However, most concrete formwork currently used is temporary, made of wood or steel. This formwork is removed once the concrete reaches its design strength during construction and does not participate in the load-bearing process during the service life of the concrete structure, resulting in a significant waste of natural resources. Unlike temporary formwork, permanent formwork, in addition to its supporting and shaping functions during construction, shares the load with the concrete during its service life. Therefore, permanent formwork simplifies construction procedures, shortens the construction cycle, reduces project costs, and conserves resources and protects the environment. Furthermore, due to the relatively low tensile strength, ductility, and damage tolerance of ordinary concrete, the surface of concrete structures is prone to cracking, leading to numerous structural durability problems. Using fiber-reinforced cementitious composite materials with good mechanical and durability properties as permanent formwork, and then pouring concrete into them, this composite structure is expected to overcome the above-mentioned shortcomings of traditional concrete structures. Summary of the Invention

[0003] To address the above technical problems, this invention discloses a hybrid fiber-reinforced cement-based permanent formwork for beam-column joints and its preparation method, which simplifies the construction process, reduces project costs, increases the durability of concrete structures, and alleviates the current shortage of freshwater river sand resources.

[0004] The technical solution adopted by this invention is as follows:

[0005] A hybrid fiber reinforced cement-based permanent formwork for beam-column joints is assembled from hollow permanent column formwork and U-shaped permanent beam formwork. The permanent column formwork and the permanent beam formwork are made of hybrid fiber reinforced cement-based material. The hybrid fiber reinforced cement-based material includes hybrid fiber cement-based material and a hybrid fiber mesh located in the middle. The hybrid fiber mesh is a hybrid fiber mesh woven from dry fiber bundles and impregnated fiber bundles distributed longitudinally and transversely. The cement-based material contains at least two kinds of short chopped fiber filaments.

[0006] The permanent column formwork has openings at the connection points with the permanent beam formwork, through which a hybrid fiber mesh extends. A hybrid fiber mesh also extends from the ends of the permanent beam formwork. At the joint between the permanent column and beam formwork, the extended hybrid fiber meshes are connected as a single unit using adhesive and encapsulated with a hybrid fiber cementitious material. The permanent beam formwork is U-shaped, and the impregnated fiber bundles are dry fiber bundles cured with epoxy resin. Both the permanent column and beam formwork are prepared using existing techniques employing hybrid fiber-reinforced cementitious materials.

[0007] This technical solution utilizes a permanent formwork made of hybrid fiber-reinforced cementitious material. The dry fiber bundles and impregnated fiber bundles in the fiber mesh are distributed alternately in both directions. The dry fiber bundles are soft and have low stiffness, while the impregnated fiber bundles are hard and have high stiffness. The combination of these two types of fibers results in a hybrid fiber mesh with excellent workability. The hybrid fiber cementitious material contains chopped fiber filaments, which increases the tensile and crack resistance of the cementitious material, while avoiding cracking of the permanent formwork due to concrete pouring. Furthermore, under the same performance requirements, the hybrid fiber cementitious material is lighter and stronger. Encapsulation with the hybrid fiber cementitious material prevents the adhesive from being affected by the external environment. At the joints, both types of fiber meshes extend outwards, and the hybrid fiber mesh in the beam and column components is integrated using adhesive, ensuring good load-bearing performance.

[0008] As a further improvement of the present invention, the adhesive is a conductive adhesive, and the fiber material used for the dry fiber bundles and impregnated fiber bundles in the fiber mesh is conductive fiber, so that the auxiliary anode material in the beam and column components can be connected as a whole.

[0009] As a further improvement of the present invention, the inner walls of the permanent formwork for columns and beams are provided with several grooves to increase the interfacial bonding performance between cement-based materials and concrete materials. This technical solution results in better structural compatibility, enabling the structure to jointly withstand externally applied loads.

[0010] As a further improvement of the present invention, the groove array is distributed.

[0011] As a further improvement of the present invention, the depth of the groove is 3-10 mm and the width is 5-15 mm. More preferably, the depth of the groove is 5 mm and the width is 10 mm.

[0012] As a further improvement of the present invention, the dry fiber bundle and the impregnated fiber bundle are made of two of the following fiber materials: carbon fiber bundle, glass fiber bundle, basalt fiber bundle, and aramid fiber bundle. That is, the dry fiber bundle and the impregnated fiber bundle can be made of different fiber materials.

[0013] As a further improvement of the present invention, the chopped fiber filaments include at least two of PP fiber, PVA fiber, PE fiber, steel fiber, and carbon fiber.

[0014] As a further improvement of the present invention, one of the materials of the fiber bundle and the chopped fiber filaments is carbon fiber. Furthermore, both the dry fiber bundle and the chopped fiber filaments are made of carbon fiber. Using this technical solution, the hybrid fiber-reinforced cement-based beam-column joint permanent formwork can serve as an auxiliary anode material in an impressed current cathodic protection system, preventing internal reinforcing steel or steel from being corroded.

[0015] As a further improvement of the present invention, the adhesive is a conductive epoxy resin.

[0016] As a further improvement of the present invention, the permanent column formwork can be square, circular or polygonal, and the permanent column formwork and the permanent beam formwork can be reinforced concrete components, steel-concrete composite components or combinations thereof.

[0017] This invention also discloses a method for preparing permanent formwork for hybrid fiber-reinforced cement-based beam-column joints as described in any of the above claims, comprising the following steps:

[0018] Step S1: Fabricate permanent column formwork and permanent beam formwork respectively; the permanent column formwork has openings with the same cross-sectional dimensions as the permanent beam formwork, and fiber mesh extends out from the openings; the permanent beam formwork has fiber mesh extending out from its ends;

[0019] Step S2: Fix and place the permanent column template and trim the fiber mesh at the opening; splice the permanent beam template and the permanent column template, and use adhesive to bond the fiber mesh extending from the permanent beam template and the permanent column template at the splice, and encapsulate the outside of the splice with a hybrid fiber cement-based material.

[0020] As a further improvement of the present invention, in step S2, the adhesive is a conductive epoxy resin. When using conductive epoxy resin to cure the fiber mesh, small wooden strips are used to surround the curing area to prevent the conductive epoxy resin from flowing out.

[0021] Furthermore, the conductive epoxy resin can be heated during curing to accelerate its curing speed.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The permanent formwork using the technical solution of this invention simplifies construction procedures, shortens the construction cycle, reduces project costs, and conserves resources and protects the environment. As a structural reinforcement material and a dense protective layer on the outside of concrete, it increases the mechanical properties of the concrete structure. Furthermore, by using conductive fibers and conductive adhesives, this permanent formwork can serve as the anode material in an impressed current cathodic protection system, improving the durability of the concrete structure. In addition to its supporting and shaping functions during construction, the permanent formwork shares the load with the concrete during its service life, increasing the structure's load-bearing capacity and stiffness. Furthermore, the application of an impressed current cathodic protection system can significantly extend the service life of the concrete structure and reduce carbon emissions throughout its entire life cycle. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of a permanent formwork structure for a hybrid fiber-reinforced cement-based column according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of the permanent formwork structure for a hybrid fiber-reinforced cement-based beam according to an embodiment of the present invention.

[0026] Figure 3 This is a schematic diagram of the structure of the hybrid fiber mesh according to an embodiment of the present invention.

[0027] Figure 4 This is a schematic diagram of beam and column formwork splicing according to an embodiment of the present invention.

[0028] Figure 5 This is a schematic diagram of a permanent template for a node after the conductive epoxy resin has been bonded and cured, according to an embodiment of the present invention.

[0029] Figure 6 This is a schematic diagram of the permanent template for the node after encapsulation with hybrid fiber cement-based material, according to an embodiment of the present invention.

[0030] Figure 7 This is a schematic diagram of the disassembly of the beam-column joint template according to an embodiment of the present invention.

[0031] The reference numerals in the figures include:

[0032] 1-Permanent formwork for columns, 2-Permanent formwork for beams, 3-Hybrid fiber cement-based material layer, 4-Hybrid fiber mesh, 5-Groove, 6-Conductive epoxy resin, 7-Encapsulation layer, 11-Opening, 41-Dry fiber bundle, 42-Impregnated fiber bundle. Detailed Implementation

[0033] The preferred embodiments of the present invention will be described in further detail below.

[0034] A multifunctional hybrid fiber-reinforced cement-based permanent formwork for beam-column joints can be used not only as a structural reinforcement material and an anode material for impressed current cathodic protection systems, but also as a dense protective layer on the outside of concrete.

[0035] like Figures 1 to 7 As shown, the permanent formwork for the beam-column joint is assembled from a permanent column formwork 1 with side openings and a permanent U-shaped beam formwork 2. Both the permanent column formwork 1 and the permanent U-shaped beam formwork 2 are made of a hybrid fiber-reinforced cementitious composite material. This hybrid fiber-reinforced cementitious composite material includes hybrid fiber cementitious material layers 3 on the inner and outer sides and a hybrid fiber mesh 4 in the middle, located between the inner and outer hybrid fiber cementitious material layers 3.

[0036] The hybrid fiber cementitious material contains chopped fiber filaments to increase its strength and toughness, thereby enhancing the tensile and crack resistance of the cementitious material. It also avoids the problem of permanent formwork cracking caused by concrete pouring, and makes the hybrid fiber cementitious material lighter and stronger while meeting the same performance requirements. The chopped fiber filaments can be at least two of the following: PP fiber, PVA fiber, PE fiber, steel fiber, and carbon fiber.

[0037] like Figure 3 As shown, the hybrid fiber mesh 4 is composed of alternating dry fiber bundles 41 and impregnated fiber bundles 42. The fiber bundle materials used for the dry fiber bundles 41 and impregnated fiber bundles 42 are two of the following: carbon fiber bundles, glass fiber bundles, basalt fiber bundles, and aramid fiber bundles. The dry fiber bundles 41 and impregnated fiber bundles 42 are distributed alternately in both directions. The dry fiber bundles 41 are soft and have low stiffness, while the impregnated fiber bundles 42 are hard and have high stiffness. Based on the mixing ratio of the two types of fibers, a hybrid fiber mesh 4 with good working performance can be designed.

[0038] The inner walls of the permanent formwork 1 for columns and the permanent formwork 2 for beams are provided with grooves 5 mm deep and 10 mm wide to increase the interfacial bonding performance between cement-based materials and concrete materials, thereby improving the structural performance and enabling them to jointly bear the external loads.

[0039] To facilitate the connection of beam-column joints, holes 11 are made in the prefabricated column permanent formwork 1 at the connection between column permanent formwork 1 and beam permanent formwork 2. When making the holes, a section of the mixed fiber mesh 4 is left protruding from the edge of the opening for the next step of splicing. Figure 1 As shown; simultaneously, a portion of the mixed fiber mesh 4 also extends from the ends of the permanent beam formwork 2 to facilitate formwork splicing, as shown. Figure 2 As shown.

[0040] Both the column permanent formwork 1 and the beam permanent formwork 2 have mixed fiber mesh 4 extending out at the joint. During splicing, conductive epoxy resin 6 is used to connect and cure the fiber mesh extending out of the column permanent formwork 1 and the beam permanent formwork 2 at the joint, so that the mixed fiber mesh 4 in the column permanent formwork 1 and the beam permanent formwork 2 become a whole, ensuring that it has good stress performance.

[0041] Furthermore, when carbon fiber is selected as the dry fiber bundle and chopped fiber filament, the auxiliary anode materials in the permanent column formwork 1 and permanent beam formwork 2 can be connected as a whole through the fiber mesh connection. As the auxiliary anode material of the impressed current cathodic protection system, it can prevent the internal reinforcing steel or steel from being corroded. After the conductive epoxy resin 6 is cured, a hybrid fiber cement-based material is used to encapsulate the interface of the permanent column formwork 1 and permanent beam formwork 2 to form an encapsulation layer 7, after which the reinforcing steel can be tied, concrete can be poured, and the structural construction can be completed.

[0042] During construction, the permanent formwork for columns (1) and beams (2) is pre-assembled. The protruding fiber mesh is then bonded and cured with conductive epoxy resin (6), and encapsulated with a hybrid fiber cement-based material. This serves as a substitute for wooden and steel formwork, saving on formwork consumption and improving construction efficiency. The dense outer shell of the permanent formwork also protects the internal concrete and reinforcing steel, enhancing durability. Furthermore, after the beam-column joint is poured, the internal reinforcing steel or steel, along with the carbon fiber bundles and chopped carbon fiber filaments in the permanent formwork, can form an impressed current cathodic protection system. Once the current is applied, the system will begin to improve structural durability from the early stages of use, extending the structure's entire service life.

[0043] The preparation method of the above-mentioned multifunctional hybrid fiber-reinforced cement-based beam-column joint permanent formwork includes the following steps:

[0044] (1) Make permanent beam formwork 2 and permanent column formwork 1 of hybrid fiber reinforced cement-based composite material, and open an opening 11 at a suitable height of the permanent column formwork 1 with the same cross-sectional size as the permanent beam formwork 2, so as to connect the permanent beam formwork 2 and the permanent column formwork 1.

[0045] (2) Fix the permanent column template 1 in place and trim the mixed fiber mesh 4 at the edge of the opening to a suitable length.

[0046] (3) Use temporary supports to install the permanent formwork 1 for the columns, such as Figure 4 As shown, after installation, check whether the installation position of the permanent column formwork 1 is accurate.

[0047] (4) Temporary supports are used to splice the permanent beam formwork 2 and the permanent column formwork 1. During splicing, errors are minimized to ensure no obvious seams at the ends of the formwork. Figure 4 As shown;

[0048] (5) At the joint of the permanent beam formwork 2 and the permanent column formwork 1, conductive epoxy resin 6 is used to bond and cure the protruding mixed fiber mesh 4 of the permanent beam formwork 2 and the permanent column formwork 1. Figure 5 As shown, this makes the internal fiber mesh of the permanent beam formwork 2 and the permanent column formwork 1 a whole, resulting in a more reasonable stress distribution.

[0049] (6) After the conductive epoxy resin 6 has cured, a hybrid fiber cement-based material is used to seal the joints of the permanent beam formwork 2 and the permanent column formwork 1, such as... Figure 6 As shown, its exploded diagram is as follows: Figure 7 As shown, once the cement-based material has cured, steel bars can be tied, concrete can be poured, and the structure can be constructed.

[0050] When using epoxy resin to bond and cure fiber mesh, small wooden strips can be used to enclose the curing area to prevent epoxy resin from flowing out. The temperature can be increased appropriately to accelerate the curing speed.

[0051] The permanent formwork 1 for columns can be square, circular, or polygonal. The permanent formwork 2 for beams and the permanent formwork 1 for columns can be reinforced concrete components, steel-concrete composite components, or combinations thereof. This embodiment only describes the square formwork.

[0052] The above description, in conjunction with specific preferred embodiments, provides a further detailed explanation of the present invention. It should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention.

Claims

1. A permanent formwork for hybrid fiber-reinforced cement-based beam-column joints, characterized in that: It is assembled from hollow column permanent formwork and U-shaped beam permanent formwork. The column permanent formwork and beam permanent formwork are made of hybrid fiber reinforced cementitious material. The hybrid fiber reinforced cementitious material includes hybrid fiber cementitious material and a hybrid fiber mesh in the middle. The hybrid fiber mesh is a hybrid fiber mesh woven with dry fiber bundles and impregnated fiber bundles distributed longitudinally and laterally. The fiber material used for the dry fiber bundles and impregnated fiber bundles in the hybrid fiber mesh is carbon fiber bundles. The impregnated fiber bundles are made of a material that cures the dry fiber bundles with epoxy resin. The hybrid fiber cementitious material contains at least two kinds of chopped fiber filaments, including chopped carbon fiber filaments. The column permanent formwork has openings at the connection with the beam permanent formwork, through which a mixed fiber mesh extends. The mixed fiber mesh also extends from the ends of the beam permanent formwork. At the joint between the column permanent formwork and the beam permanent formwork, the extended mixed fiber meshes are connected as one piece by an adhesive and encapsulated with a mixed fiber cement-based material. The adhesive is a conductive epoxy resin. Concrete is poured inside the permanent formwork, and the steel bars or steel inside the concrete, together with the carbon fiber bundles and chopped carbon fiber filaments in the permanent formwork, form an impressed current cathodic protection system. When the current is turned on, the system will start to improve the durability of the structure from the early stage of its use, and increase the entire service life of the structure. The inner walls of the permanent formwork for columns and beams are provided with several grooves to increase the interfacial bonding performance between the hybrid fiber cementitious material and the concrete material. The grooves are arranged in an array, and the grooves are 5 mm deep and 10 mm wide.

2. The permanent formwork for hybrid fiber-reinforced cement-based beam-column joints according to claim 1, characterized in that: The chopped fiber filaments include at least one of PP fiber, PVA fiber, PE fiber, and steel fiber.

3. The method for preparing permanent formwork for hybrid fiber-reinforced cement-based beam-column joints as described in any one of claims 1 to 2, characterized in that: Includes the following steps: Step S1: Fabricate permanent formwork for columns and permanent formwork for beams respectively; the permanent formwork for columns has openings with the same cross-sectional dimensions as the permanent formwork for beams, and fiber mesh extends out from the openings; Fiber mesh extends from the ends of the permanent formwork for the beam; Step S2: Fix and place the permanent column template and trim the fiber mesh at the opening; splice the permanent beam template and the permanent column template, and use adhesive to bond the fiber mesh extending from the permanent beam template and the permanent column template at the splice, and encapsulate the outside of the splice with a hybrid fiber cement-based material.

4. The method for preparing permanent formwork for hybrid fiber-reinforced cement-based beam-column joints according to claim 3, characterized in that: In step S2, the adhesive is conductive epoxy resin. When using conductive epoxy resin to cure the fiber mesh, small wooden strips are used to surround the curing area to prevent the conductive epoxy resin from flowing out.

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