High performance fiber reinforced cementitious precast formwork and concrete composite interface reinforcement technology

Abstract

The application discloses a high-performance fiber reinforced cement-based prefabricated formwork and concrete combined interface reinforcing technology, characterized in that: high-performance fiber reinforced cement-based prefabricated formwork (100) and cast-in-place concrete (200) are connected through screws (300) arranged in an array at the joint surface of the high-performance fiber reinforced cement-based prefabricated formwork (100); the screw (300) is embedded in the high-performance fiber reinforced cement-based prefabricated formwork (100) with a nail tip end (1) and protrudes from the joint surface with a nail cap end (2) and is poured into the cast-in-place concrete (200); the arrayed screws (300) are pre-anchored at the joint surface of the high-performance fiber reinforced cement-based prefabricated formwork (100) by a positioning plate (400). Compared with the prior art, the high-performance fiber reinforced cement-based prefabricated formwork and concrete combined interface reinforcing technology can simultaneously significantly improve the shear capacity and normal bonding force of the combined interface, ensures that the prefabricated formwork and the internal cast-in-place concrete form a reliable combined effect, and realizes the 'equivalent cast-in-place' of the demoulding-free formwork component. The application has a good application prospect in the fabricated building.

Description

Technical Field

[0001] This invention relates to the field of prefabricated building structure technology, specifically a structural measure and manufacturing method that enhances the bonding force between high-performance fiber-reinforced cement-based prefabricated templates and post-cast concrete by pre-embedding commercial screws. Background Technology

[0002] Formwork-free components (also known as shell components) are an important type of component in prefabricated concrete structural systems. Their basic form consists of a cement-based formwork set outside a pre-cast steel cage, with concrete poured into the cavity of the formwork. The outer cement-based formwork serves as the formwork for pouring the internal concrete during construction and does not need to be removed after completion; the surface of the formwork becomes the outer surface of the component. Therefore, construction efficiency and appearance quality are effectively improved. Furthermore, because the internal concrete is cast-in-place monolithically and the longitudinal reinforcement is mechanically connected, the structure has good overall integrity, making it an important component type for prefabricated buildings in high-intensity seismic zones (such as Hainan).

[0003] However, existing formwork-free structural members have significant drawbacks. Due to the unreliable bond between the precast formwork and the cast-in-place concrete, the stress at the interface cannot be effectively transferred, making it difficult for the precast formwork to work in concert with the internal concrete to bear the load. Therefore, current designs for formwork-free structural members do not account for the contribution of the outer precast formwork to the structural member's load-bearing capacity, and the formwork cannot be used as a protective layer for the internal reinforcement. This results in larger cross-sectional dimensions for formwork-free structural members compared to cast-in-place members, reducing usable space within the building and becoming a major pain point in their practical application. Existing formwork-free technology urgently needs improvement.

[0004] The key to achieving coordinated stress distribution between precast formwork and internal concrete is improving the bonding strength at the composite interface. Currently, researchers have proposed structural measures to enhance the bond performance between ultra-high performance concrete precast slabs and cast-in-place concrete, mainly including interface agent treatment (such as applying polymer emulsion), roughening and grooving the surface of the precast slab, and creating grooves on the bonding surface of the precast slab. Experiments show that these technical measures can effectively improve the shear strength along the tangential direction of the composite interface, which is very effective in enhancing the coordinated stress distribution effect of formwork-free flexural members. Numerous experiments have shown that for formwork-free compression members, under axial compression loads, there is significant delamination and voiding between the precast formwork and cast-in-place concrete, often leading to premature delamination of the precast formwork. Furthermore, delamination between the formwork and the internal concrete also prevents the precast formwork from effectively participating in the seismic energy dissipation of the member. This is the main factor preventing formwork-free compression members from achieving "equivalent to cast-in-place." However, existing techniques for improving interface bonding strength cannot effectively improve the bonding strength along the normal direction of the composite interface, meaning that these techniques are difficult to effectively improve the stress performance of formwork-free vertical members. It should be noted that the tie rods currently installed in the vertical components of the formwork-free system are intended to prevent problems such as bulging, cracking, and bursting of the outer formwork during the pouring of internal concrete. Therefore, they cannot be used as connectors for the composite interface, nor can they effectively improve the cooperative stress effect between the formwork and the internal concrete. Therefore, there is an urgent need to propose new interface construction measures that can effectively improve the shear resistance of the composite interface while significantly improving the bonding force along the normal direction, thus overcoming the shortcomings of existing formwork-free technology. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the present invention aims to provide a reinforcement technology for the interface between precast templates and cast-in-place concrete. The technical solution is as follows: A high-performance fiber-reinforced cement-based precast template and concrete composite interface reinforcement technology, characterized in that: the high-performance fiber-reinforced cement-based precast template (100) and the cast-in-place concrete (200) are connected by screws (300) arranged in an array at the interface of the high-performance fiber-reinforced cement-based precast template (100); the tip (1) of the screw (300) is pre-embedded in the high-performance fiber-reinforced cement-based precast template (100), and the head end (2) extends outward from the interface and is poured into the cast-in-place concrete (200); the array of screws (300) is pre-anchored at the interface of the high-performance fiber-reinforced cement-based precast template (100) using positioning plates (400), as follows:

[0006] Step 1: Mark the position of the screw (300) on the surface of the positioning plate (400) and drill positioning holes (3). The depth of the positioning holes (3) is less than the extension length of the nail head section (2) at the mating surface.

[0007] Step 2: Insert the head end (2) of the screw (300) into the positioning hole (3) one by one, with the tip (1) of the screw extending out of the surface of the positioning plate (400), and set a washer (4) around the perimeter of the positioning plate (400).

[0008] Step 3: Pour high-performance fiber-reinforced cementitious material into the steel mold (5) and vibrate it to make it level and dense;

[0009] Step 4: Place the positioning plate (400) upside down on the steel mold (5) so that the tip (1) of the screw (300) is inserted into the high-performance fiber-reinforced cementitious material, and the positioning plate (400) does not contact the surface of the high-performance fiber-reinforced cementitious material.

[0010] Step 5: After the high-performance fiber-reinforced cementitious material has hardened, remove the positioning plate (400), and anchor the nail tips (1) of the arrayed screws (300) in the high-performance fiber-reinforced cementitious precast template (100), with the nail head end (2) extending outward from the joint surface.

[0011] The high-performance fiber-reinforced cement-based precast formwork and concrete composite interface enhancement technology is characterized in that: the anchorage length of the nail tip (1) in the high-performance fiber-reinforced cement-based precast formwork (100) is adjusted by changing the thickness of the shim (4). The material of the high-performance fiber-reinforced cement-based precast formwork (100) includes ultra-high performance concrete, high ductility concrete and fiber fabric reinforced cement-based material, with a thickness of 15~25mm. The screw (300) has a diameter of 4~8mm, a length of 15~30mm, and the anchorage length of the nail tip (1) in the high-performance fiber-reinforced cement-based precast formwork (100) is 10~15mm, and the anchorage length of the nail head end (2) in the cast-in-place concrete (200) is 5~15mm.

[0012] Compared to existing technologies, the advantages of this invention are as follows: The precast formwork and concrete interface reinforcement technology of this invention, by pre-embedding an array of screws in a high-performance fiber-reinforced cement-based precast formwork as a connection reinforcement measure for the interface, uses the screws themselves as shear connectors, effectively improving the shear strength of the interface. The screw tips are sunk into the high-performance fiber-reinforced cement-based formwork, and the threads form a reliable mechanical engagement with the cement-based material matrix, while the screw heads are cast into the cast-in-place concrete, forming an effective anchoring effect under the embedding action of the screw heads. This effectively improves the pull-out resistance of the interface along the normal direction, preventing peeling and voids between the precast formwork and the cast-in-place concrete. Therefore, the group of screws at the interface can simultaneously and significantly improve the shear resistance and normal bonding force of the interface, ensuring a reliable combination effect between the precast formwork and the internal cast-in-place concrete, achieving synergistic stress distribution. Precast formwork made of high-performance fiber-reinforced cementitious materials possesses high strength, high crack resistance, and high ductility. It effectively prevents the penetration of corrosive ions from the outside. Precast formwork can be directly used as a protective layer for structural members, providing excellent containment of internal steel reinforcement, and is particularly suitable for corrosive environments. Therefore, precast formwork can be considered equivalent to cast-in-place concrete, serving as part of the structural components without increasing the cross-sectional dimensions of the formed members, thus achieving "cast-in-place equivalent" components without the need for formwork removal.

[0013] Furthermore, the arrayed screws are numerous and evenly distributed, ensuring the uniformity of force transmission at the composite interface. Moreover, the "pinning effect" of the screws is based on the matrix mechanical interlocking force of the high-performance fiber-reinforced cementitious material and the bending resistance effect of the screw itself, which is a ductile connection with reliable performance. The entire composite interface has high connection strength and good ductility, which has significant advantages compared with existing composite interface reinforcement technologies based on concrete bonding force and friction.

[0014] Furthermore, the present invention uses commercial screws as connectors, eliminating the need for customization and resulting in extremely low prices. At the same time, the proposed group screw installation method based on positioning plate flipping is simple, efficient, and does not require changes to the existing prefabricated shell production process. Therefore, the proposed combined interface enhancement technology is economically viable. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the appearance of a high-performance fiber-reinforced cement-based precast formwork.

[0016] Figure 2 This is a schematic diagram of the positioning plate.

[0017] Figure 3 This is a schematic diagram of the processing of high-performance fiber-reinforced cement-based precast templates.

[0018] Figure 4 This is a schematic diagram of the interface connection between high-performance fiber-reinforced cement-based precast formwork and cast-in-place concrete.

[0019] Figure 5 This is a schematic diagram of the construction of columns without the need for formwork removal;

[0020] Figure 6 This is a schematic diagram of the construction of a shear wall without the need for formwork removal.

[0021] In the figure: (1) nail tip; (2) nail head end; (3) positioning hole; (4) gasket; (5) steel mold; (6) steel cage; (7) hoop; (8) temporary support; (100) high-performance fiber reinforced cement-based precast formwork; (200) cast-in-place concrete; (300) screw; (400) positioning plate. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0023] Example 1 (Column without formwork removal):

[0024] Step 1: Mark the position of the screw (300) on the surface of the positioning plate (400) and drill positioning holes (3). The depth of the positioning holes (3) is less than the extension length of the nail head section (2) at the mating surface.

[0025] Step 2: Insert the head end (2) of the screw (300) into the positioning hole (3) one by one, with the tip (1) of the screw extending out of the surface of the positioning plate (400), and set a washer (4) around the periphery of the positioning plate (400).

[0026] Step 3: Pour high-performance fiber-reinforced cementitious material into the steel mold (5) and vibrate it to make it level and dense;

[0027] Step 4: Place the positioning plate (400) upside down on the steel mold (5) so that the tip (1) of the screw (300) is inserted into the high-performance fiber-reinforced cementitious material, and the positioning plate (400) does not contact the surface of the fiber-reinforced high-performance cementitious material.

[0028] Step 5: After the high-performance fiber-reinforced cementitious material has hardened, remove the positioning plate (400), and anchor the nail tips (1) of the arrayed screws (300) in the high-performance fiber-reinforced cementitious precast template (100), with the nail head end (2) extending outward from the joint surface.

[0029] Step 6: Surround multiple high-performance fiber-reinforced cement-based precast formwork (100) around the outside of the steel cage (6) and fix them with hoops (7), temporary supports (8), etc.; then, pour concrete (200) and vibrate it to compact it. After the concrete reaches the preset strength, remove the temporary fixing measures to complete the construction of the formwork column without removing the formwork.

[0030] Example 2 (Shear Wall without Formwork Removal):

[0031] Step 1: Mark the position of the screw (300) on the surface of the positioning plate (400) and drill positioning holes (3). The depth of the positioning holes (3) is less than the extension length of the nail head section (2) at the mating surface.

[0032] Step 2: Insert the head end (2) of the screw (300) into the positioning hole (3) one by one, with the tip (1) of the screw extending out of the surface of the positioning plate (400), and set a washer (4) around the periphery of the positioning plate (400).

[0033] Step 3: Pour high-performance fiber-reinforced cementitious material into the steel mold (5) and vibrate it to make it level and dense;

[0034] Step 4: Place the positioning plate (400) upside down on the steel mold (5) so that the tip (1) of the screw (300) is inserted into the high-performance fiber-reinforced cementitious material, and the positioning plate (400) does not contact the surface of the fiber-reinforced high-performance cementitious material.

[0035] Step 5: After the high-performance fiber-reinforced cementitious material has hardened, remove the positioning plate (400), and anchor the nail tips (1) of the arrayed screws (300) in the high-performance fiber-reinforced cementitious precast template (100), with the nail head end (2) extending outward from the joint surface.

[0036] Step 6: Install multiple high-performance fiber-reinforced cement-based precast formwork (100) on both sides of the shear wall reinforcement cage (6) and use temporary supports (8) and other fixing measures; then, pour concrete (200) and vibrate it to compact it. After the concrete reaches the preset strength, remove the temporary fixing measures to complete the construction of the shear wall without removing the formwork.

[0037] The above embodiments are merely preferred embodiments of the present invention and should not be construed as limiting the scope of protection of the present invention. Any non-substantial changes and substitutions made by those skilled in the art based on the present invention, such as using other types of nails, custom double-ended nails, other types of screws to replace screws, or pre-embedding the head end of the screw in a precast template and casting the tip of the screw into the cast-in-place concrete, can all be simple technical substitutions based on the prompts of the present invention, and therefore all fall within the scope of protection claimed by the present invention.

Claims

1. A high-performance fiber-reinforced cement-based precast formwork and concrete composite interface reinforcement technology, characterized in that: The high-performance fiber-reinforced cement-based precast template (100) and the cast-in-place concrete (200) are connected by screws (300) arranged in an array at the joint surface of the high-performance fiber-reinforced cement-based precast template (100); the tip (1) of the screw (300) is embedded in the high-performance fiber-reinforced cement-based precast template (100), and the head end (2) extends outward from the joint surface and is poured into the cast-in-place concrete (200); the arrayed screws (300) are pre-anchored at the joint surface of the high-performance fiber-reinforced cement-based precast template (100) using positioning plates (400), as follows: Step 1: Mark the position of the screw (300) on the surface of the positioning plate (400) and drill positioning holes (3). The depth of the positioning holes (3) is less than the protrusion length of the nail head end (2) at the mating surface. Step 2: Insert the head end (2) of the screw (300) into the positioning hole (3) one by one, with the tip (1) of the screw extending out of the surface of the positioning plate (400), and set a washer (4) around the perimeter of the positioning plate (400). Step 3: Pour high-performance fiber-reinforced cementitious material into the steel mold (5) and vibrate it to make it level and dense; Step 4: Place the positioning plate (400) upside down on the steel mold (5) so that the tip (1) of the screw (300) is inserted into the high-performance fiber-reinforced cementitious material, and the positioning plate (400) does not contact the surface of the high-performance fiber-reinforced cementitious material. Step 5: After the high-performance fiber-reinforced cementitious material has hardened, remove the positioning plate (400), and anchor the nail tips (1) of the arrayed screws (300) in the high-performance fiber-reinforced cementitious precast template (100), with the nail head end (2) extending outward from the joint surface.

2. The high-performance fiber-reinforced cement-based precast formwork and concrete interface reinforcement technology according to claim 1, characterized in that: The anchorage length of the nail tip (1) in the high-performance fiber-reinforced cement-based precast template (100) is adjusted by changing the thickness of the shim (4).

3. The high-performance fiber-reinforced cement-based precast formwork and concrete interface reinforcement technology according to claim 1, characterized in that: The materials of the high-performance fiber-reinforced cement-based precast formwork (100) include ultra-high performance concrete, high ductility concrete and fiber-reinforced cement-based materials, with a thickness of 15~25mm.

4. The high-performance fiber-reinforced cement-based precast formwork and concrete composite interface reinforcement technology according to claim 1, characterized in that: The screw (300) has a diameter of 4~8mm and a length of 15~30mm. The nail tip (1) has an anchorage length of 10~15mm in the high-performance fiber-reinforced cement-based precast template (100), and the nail head end (2) has an anchorage length of 5~15mm in the cast-in-place concrete (200).

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