Prestressed long-span composite slab with prefabricated ecc bottom plate and post-cast grc superimposed layer and construction method thereof

Abstract

The application discloses a prestressed large-span composite slab with a prefabricated ECC bottom plate and a post-cast GRC composite layer and a construction method thereof. The prestressed large-span composite slab with the prefabricated ECC bottom plate and the post-cast GRC composite layer comprises a bottom plate and a post-cast layer, the bottom plate is integrally poured by using an ECC material and a bottom plate twisted wire net composed of a horizontal twisted wire and a longitudinal twisted wire; and a rectangular rib is integrally arranged on the bottom plate, the rectangular rib is integrally poured by using a truss steel bar and the bottom plate; and the truss steel bar is bound with the bottom plate twisted wire net by using a wire. The ECC-high-strength stainless steel twisted wire / SMA twisted wire has good crack control and dispersion capacity, high toughness and ductility, so that the bottom plate can be made thinner, the self weight is reduced, the concrete consumption is reduced, and the span of the prefabricated composite slab is increased; the rectangular rib of the truss steel bar structure improves the rigidity, shearing capacity, bearing capacity and bending resistance of the bottom plate, so that the composite slab can cope with large-span structures and high load requirements.

Description

Technical Field

[0001] This invention relates to a precast composite slab structure and construction method, and more particularly to a precast composite slab with rectangular rib-truss reinforcement, ECC-high-strength stainless steel strand / SMA strand, and post-cast recycled concrete, and construction method thereof. Background Technology

[0002] Precast composite slabs have long been widely used in construction projects due to their efficient construction methods, good mechanical properties, and economic efficiency. However, traditional precast composite slabs often use ordinary steel reinforcement and conventional concrete structures. While these can meet the load-bearing requirements of general buildings, in large-span, high-load structural applications, the load-bearing capacity, crack resistance, and durability of ordinary reinforced concrete are limited, making it difficult to withstand long-term loads and harsh environmental conditions. Furthermore, with increasing resource scarcity and growing environmental protection demands, the sustainability and recycling of building materials are receiving increasing attention.

[0003] In recent years, the use of novel high-strength materials and structural forms has become a research hotspot in order to improve the performance of precast composite slabs. For example, engineering cement-based composites (ECCs) are increasingly being used in high-performance precast components due to their excellent crack resistance, tensile strength, and durability. Meanwhile, the application of stainless steel stranded wire and shape memory alloy (SMA) stranded wire provides new technical pathways for improving the durability, corrosion resistance, and seismic performance of components. The introduction of these high-performance materials, combined with the green and environmentally friendly characteristics of post-cast recycled concrete, provides new solutions for optimizing the performance of precast composite slabs. However, current common precast composite slab designs still have many limitations, such as heavy slab weight, insufficient overall stiffness, and limited bending and shear resistance, especially prone to cracking and excessive deformation under large spans and high loads. Furthermore, traditional reinforcement arrangements sometimes fail to fully utilize the mechanical properties of the materials, leading to uneven structural stress and material waste.

[0004] In current precast composite slabs, problems often arise at the joints. While the joints between precast composite slabs and precast composite beams are relatively easy to manage, the joints between precast composite slabs themselves are prone to issues such as early cracking and leakage at the post-cast strip. Therefore, in practical engineering projects, large-span precast composite slabs should be prioritized. Furthermore, some projects have actual requirements for large spaces, necessitating the use of large-span composite slabs. To achieve large-span design goals, using precast prestressed composite slabs offers significant advantages.

[0005] Utility model patent CN215164532U discloses a corrosion-resistant, closely spaced bridge composite slab based on UHPC (Ultra-High Performance Concrete). The slab includes a precast base slab and a cast-in-place concrete layer. The precast base slab is constructed from UHPC ultra-high performance concrete and a reinforcing mesh. The bottom surface of the precast base slab is coated with an ECC (Engineering Cemented Concrete) cement-based composite material layer; the top surface is sandblasted roughened or has an uneven surface. Multiple closely spaced grooves are provided at both longitudinal ends of the precast base slab, and L-shaped reinforcing bars are placed in the middle grooves. The bottom ends of the L-shaped reinforcing bars are connected to the L-shaped reinforcing bars on the mating precast base slab via grouting sleeves. This utility model not only improves the corrosion resistance and bending strength of the bridge composite slab but also enhances its crack resistance, thereby improving bridge safety and reliability, reducing future maintenance costs, and featuring fast inter-slab connection speed and high connection accuracy.

[0006] Although the aforementioned document proposes using closely spaced grooves for reinforcement, these grooves are only placed at both ends of the precast base slab. Their design purpose is to connect the two precast slabs in conjunction with the L-shaped steel bars used in the design. This does not make any special contribution or significance to the precast composite slab itself and is difficult to meet the requirements of large-span precast composite slab base slabs for stiffness, flexural deformation and construction load.

[0007] Therefore, it is necessary to design a precast composite slab that can not only effectively enhance the overall stiffness and bending and shear resistance of the slab, but also improve the crack resistance, durability and self-healing ability of the structure through the use of high-performance materials, so as to meet the application requirements of large-span and high-load structures, while taking into account resource recycling and environmental protection.

[0008] This will provide new ideas and technical support for the design and application of prefabricated building components. Summary of the Invention

[0009] To address the shortcomings of existing technologies, this invention proposes a precast composite slab structure consisting of ECC-high-strength stainless steel stranded wire / SMA stranded wire with rectangular ribbed truss reinforcement and post-cast recycled concrete. This structure can effectively reduce the flexural deformation of the precast composite slab bottom plate, effectively increase the stiffness of the precast composite slab floor, and meet the requirements of deflection deformation and construction load for large-span precast composite slabs.

[0010] The present invention also proposes a construction method for the precast composite slab.

[0011] The technical solution adopted in this invention is as follows: A precast composite slab with rectangular ribs-truss reinforcement, ECC-high-strength stainless steel strand / SMA strand and post-cast recycled concrete, includes a base slab and a post-cast layer. The base slab includes transverse strands, longitudinal strands, rectangular ribs, truss reinforcement and ECC made of high-strength stainless steel strand / SMA strand. The post-cast layer is recycled concrete. The horizontal and vertical stranded wires of the base plate are fixed to the base plate template by aluminum clips and slip knot bolts to form a stranded wire mesh. The base plate stranded wire mesh is made of high-strength stainless steel stranded wire or partially replaced by SMA stranded wire. The replacement quantity should be adjusted according to the specific design requirements.

[0012] The rectangular ribs are set at the truss reinforcement on the bottom plate; the truss reinforcement is tied to the bottom stranded wire mesh with tie wire.

[0013] The one-way slab has truss reinforcement and rectangular ribs arranged in the longitudinal direction, while the two-way slab has truss reinforcement and rectangular ribs arranged in both the transverse and longitudinal directions; the width of the rectangular ribs is 100-250mm, and the height of the rectangular ribs is 40mm. The truss reinforcement extends 10-20mm above the rectangular ribs.

[0014] The diameter of the high-strength stainless steel stranded wire and SMA stranded wire is not less than 3.6 mm and not more than 6 mm. The diameter of the transverse stranded wire of the unidirectional plate bottom plate is smaller than the diameter of the longitudinal stranded wire of the bottom plate. The diameters of the transverse stranded wire and the longitudinal stranded wire of the bidirectional plate bottom plate are the same.

[0015] The base plate template includes a steel plate, a limiting angle steel, and a fixing angle steel. The limiting angle steel and the fixing angle steel are fixed to the steel plate with bolts. The limiting angle steel has a limiting hole, and the fixing angle steel has a fixing slot. The fixing angle steel is arranged around the periphery of the limiting angle steel, and there is a gap of not less than 80mm between the two.

[0016] A construction method for a precast composite slab of ECC-high-strength stainless steel stranded wire / SMA stranded wire with rectangular ribbed truss reinforcement and post-cast recycled concrete includes the following steps: S1: Fix the limiting angle steel and the fixing angle steel to the steel plate according to the design dimensions. Pass the end of the stranded wire through the limiting hole of the limiting angle steel. Fix the end of the stranded wire to the fixing slot on the fixing angle steel with aluminum buckles and slip bolts. Use this method to alternately fix the transverse stranded wire and the longitudinal stranded wire of the bottom plate to the bottom plate template. Finally, tie the truss reinforcement and the bottom plate stranded wire mesh with tie wire. S2: Place concrete protective layer pads at the bottom of the bottom plate stranded wire mesh. After confirming that everything is correct, pour the mixed ECC to the height of the bottom plate. Fill the remaining positions of the rectangular ribs on the bottom plate with long wooden strips. Finally, pour the mixed ECC to the height of the rectangular ribs in the gaps of the long wooden strips. S3: After the ECC surface has initially set, the surface of the specimen is artificially roughened using a wooden toothed brush to meet the rough surface requirements in the design specifications.

[0017] S4: Use the precast base slab as the bottom formwork, and support the side formwork around it as the formwork for the subsequent concrete pouring. Then tie and fix the structural steel mesh in the subsequent pouring layer, and pour the prepared recycled concrete on the base slab.

[0018] Beneficial effects of the invention: 1. This invention relates to a precast composite slab. The base slab incorporates truss reinforcement and ribs, effectively improving the bending resistance and sectional stiffness of the precast composite slab floor. The truss reinforcement provides structural stiffness and shear resistance, while the ribs enhance load-bearing capacity and bending resistance, enabling the slab to withstand large-span structures and high load requirements. Furthermore, the use of recycled concrete aligns with green environmental protection principles. The use of truss reinforcement makes construction more convenient and efficient.

[0019] 2. The precast composite slab of this invention uses a combination of ECC and SMA stranded wire / steel strand in the base plate, and employs SMA stranded wire / reinforcing steel for prestressing. This combination significantly improves crack control and crack dispersion capabilities, effectively reducing deflection during the construction phase of the precast composite slab. Combined with SMA stranded wire prestressing (SMA stranded wire can replace some high-strength stainless steel stranded wire depending on different working conditions), it effectively reduces deflection during the construction phase of the precast composite slab, making it particularly suitable for large-span precast composite slab floor applications.

[0020] After construction, SMA (shape memory alloy) stranded wires can be prestressed by heating them with AC power. This prestress is then applied to the precast composite slab base plate, which can improve the crack resistance of the precast composite slab floor and, to some extent, cause a "reverse supply effect" in the precast composite slab base plate. This can significantly reduce the deflection deformation of the precast composite slab base plate and meet the deflection deformation requirements of large-span composite slabs after construction.

[0021] 3. The present invention uses rectangular ribs (beams) to penetrate the upper part of the entire precast composite slab bottom plate, and uses them in combination with truss reinforcement to effectively increase the stiffness and performance of the precast composite slab bottom plate, improve the stiffness of the precast composite slab floor, and can well meet the requirements of deflection deformation and construction load of large-span precast composite slabs.

[0022] When the span of the precast composite slab is large or the thickness of the bottom plate of the precast composite slab is small, the stiffness of the bottom plate of the precast composite slab is too small. This will lead to excessive deflection of the bottom plate of the precast composite slab during hoisting construction, or it may not meet the requirements of the upper concrete pouring or construction machinery. Therefore, it is necessary to design rectangular ribs (beams) according to the design calculation to meet the requirements of stiffness, deflection and construction load of the bottom plate of the large-span precast composite slab.

[0023] 4. This invention utilizes the excellent crack control and dispersion capabilities, high toughness and ductility of ECC-high-strength stainless steel stranded wire / SMA stranded wire high-performance composite material, which allows the base plate to be made thinner than traditional base plates, reducing self-weight and concrete usage, and increasing the span of precast composite slabs, effectively achieving the design goal of large span precast composite slabs. Attached Figure Description

[0024] Figure 1 The figure shown is a schematic diagram of the three-dimensional structure of the prefabricated composite plate of the present invention; Figure 2 The figure shown is a three-dimensional structural diagram of the one-way plate base plate of the present invention; Figure 3 The figure shown is a three-dimensional structural diagram of the bidirectional plate bottom plate of the present invention; Figure 4 The diagram shown is a three-dimensional structural diagram of the truss reinforcement of the present invention; Figure 5 The diagram shown is a three-dimensional structural diagram of the base plate template of the present invention; Figure 6 The diagram shown is a top view of the stranded wire fixing method of the present invention.

[0025] In the diagram: 1. Base plate; 101. Transverse stranded wire of base plate; 1011. Transverse steel stranded wire of base plate; 1012. Transverse SMA stranded wire of base plate; 102. Longitudinal stranded wire of base plate; 1021. Longitudinal steel stranded wire of base plate; 1022. Longitudinal SMA stranded wire of base plate; 103. Rectangular rib; 104. Truss reinforcement; 105, ECC; 2. Post-cast layer; 3. Base plate formwork; 301, steel plate; 302, limiting angle steel; 303, limiting hole; 304, fixing angle steel; 305, fixing slot; 401, live bolt; 402, nut; 403, aluminum buckle. Detailed Implementation

[0026] To make the technical concept and advantages of this invention clearer, the technical solution of this invention will be further described in detail below with reference to the accompanying drawings. It should be understood that the following embodiments are merely preferred embodiments for explaining and illustrating this invention, and should not be considered as, nor constitute a limitation on, the scope of patent protection claimed by this invention. Example 1

[0027] See Figure 1 , Figure 2 The present invention relates to a prestressed large-span composite slab with a precast ECC base plate and a post-cast GRC composite layer, comprising a base plate 1 and a post-cast layer 2. The base plate 1 is integrally cast using ECC material and a base plate stranded mesh. The base plate stranded mesh is formed by fixing transverse strands and longitudinal strands to the base plate template using aluminum clips and swivel bolts. The base plate 1 is provided with rectangular ribs 103, which are integrally cast with the base plate by means of truss reinforcement 104; for example Figure 4 As shown, the truss reinforcement 104 is tied to the bottom plate stranded wire mesh with tie wire; The post-cast layer 2 is located above the base slab 1 and is cast using concrete or recycled concrete.

[0028] The base plate stranded wire mesh is made of high-strength stainless steel stranded wire.

[0029] There are currently no research reports on the combination of truss reinforcement and rectangular ribs. Using truss reinforcement can improve the overall performance and load-bearing capacity of prefabricated composite slabs, that is, the prefabricated composite slab and the upper post-cast concrete form a whole and share the load. In addition to the above advantages, using rectangular rib-truss reinforcement can also increase the stiffness of the prefabricated composite slab, achieve the design goal of large span and reduce deflection, and further improve the stiffness and overall performance of the prefabricated composite slab after construction.

[0030] The prestressed large-span composite slab of the present invention, consisting of a precast ECC base slab and a post-cast GRC composite layer, can not only effectively enhance the overall stiffness and bending and shear resistance of the slab, but also improve the crack resistance, durability and self-healing ability of the structure through the use of high-performance materials, thus meeting the application requirements of large-span and high-load structures, while taking into account resource recycling and environmental protection. Example 2

[0031] like Figure 3 As shown, the prestressed large-span composite slab with precast ECC base plate-post-cast GRC composite layer in this embodiment differs from that in Embodiment 1 in that the base plate stranded wire mesh uses a combination of high-strength stainless steel stranded wire and SMA stranded wire at intervals.

[0032] By using a combination of ECC and SMA stranded wire / steel strand, and replacing some of the high-strength stainless steel stranded wire with SMA stranded wire, the prestressing tension strength of the base plate can be increased, significantly improving the crack control and crack dispersion capabilities of the composite slab.

[0033] The number of SMA stranded wires used is adjusted according to specific design requirements.

[0034] The diameter of high-strength stainless steel stranded wire and SMA stranded wire is not less than 3.6 mm and not more than 6 mm. The diameter of the transverse stranded wire in the bottom plate of a one-way slab is smaller than the diameter of the longitudinal stranded wire in the bottom plate. The diameters of the transverse stranded wire and the longitudinal stranded wire in the bottom plate of a two-way slab are the same. The one-way slab has truss reinforcement and rectangular ribs arranged in the longitudinal direction, while the two-way slab has truss reinforcement and rectangular ribs arranged in both the transverse and longitudinal directions.

[0035] SMA stranded wire is composed of shape memory alloy wires. The area design of SMA stranded wire adopts the method of replacing steel strands with equal area or equal strength. When replacing with equal area, SMA stranded wire is preferably selected with the same diameter as steel stranded wire, and the replacement area is not greater than 50%. When replacing steel stranded wire with strength, the diameter of SMA stranded wire should be larger than the diameter of steel stranded wire to ensure that the number of replacement strands is consistent. Example 3

[0036] The prestressed large-span composite slab with precast ECC base slab-post-cast GRC composite layer in this embodiment differs from Embodiments 1 and 2 in that: the width of the rectangular rib 103 is 100-250mm, and the height of the rectangular rib is 40mm; the number of rectangular ribs on the precast composite slab is determined according to the requirements, and the number of rectangular ribs on a one-way slab should not be less than 3, with a spacing of 400mm-700mm between the rectangular ribs; the rectangular ribs in the main stress direction on a two-way slab should be appropriately densified, with a spacing of not more than 500mm between the rectangular ribs on a two-way slab, and a number of not less than 4, and the distance from the outermost rectangular rib of the one-way and two-way slabs to the edge of the composite slab is not more than 200mm.

[0037] The truss reinforcement extends 10-20mm above the rectangular ribs.

[0038] like Figure 5 As shown, the base plate template 3 includes a steel plate, a limiting angle steel and a fixing angle steel. The limiting angle steel and the fixing angle steel are fixed to the steel plate with bolts. The limiting angle steel has a limiting hole, and the fixing angle steel has a fixing slot. The fixing angle steel is arranged around the periphery of the limiting angle steel and the two are spaced apart by a distance of not less than 80mm. Example 4

[0039] This embodiment describes the construction method for prestressed large-span composite slabs as described above, and the process includes: Step S1: Fix the limiting angle steel and the fixing angle steel to the steel plate according to the design dimensions. Pass the end of the stranded wire through the limiting hole of the limiting angle steel. Fix the end of the stranded wire to the fixing slot on the fixing angle steel with aluminum buckles and slip bolts. Use this method to alternately fix the transverse stranded wire and the longitudinal stranded wire of the bottom plate to the bottom plate template. Finally, tie the truss reinforcement and the bottom plate stranded wire mesh with tie wire. Step S2: Place concrete protective layer pads at the bottom of the bottom plate stranded wire mesh. After confirming that everything is correct, pour the mixed ECC to the height of the bottom plate. Fill the remaining positions on the bottom plate where rectangular ribs are set with long wooden strips. Finally, pour the mixed ECC to the height of the rectangular ribs in the empty positions of the long wooden strips. Step S3: After the ECC surface has initially set, the surface of the specimen is artificially roughened using a wooden toothed brush to meet the rough surface requirements in the design specifications. Step S4: Use the precast base slab as the bottom formwork, and set up side formwork around it as the formwork for the subsequent concrete pouring. Then tie and fix the structural steel mesh in the subsequent pouring layer, and pour the prepared recycled concrete on the base slab.

[0040] The base plate 1 uses a combination of ECC and stranded wire mesh. The stranded wire mesh is made of high-strength stainless steel stranded wire or a combination of high-strength stainless steel stranded wire and SMA stranded wire at intervals. The number of SMA stranded wires used is adjusted according to specific design requirements. The area design of SMA stranded wire adopts the method of replacing steel stranded wire with equal area or equal strength. When replacing with equal area, SMA stranded wire is preferably selected with the same diameter as steel stranded wire, and the replacement area is not greater than 50%. When replacing steel stranded wire with strength, the diameter of SMA stranded wire should be larger than the diameter of steel stranded wire to ensure that the number of replacement strands is consistent.

[0041] The method for applying prestress to precast composite slabs using SMA stranded wire is as follows: Before construction, the SMA stranded wire is connected to the conductor, which extends beyond the precast composite slab. After the precast composite slab is completed, once the concrete strength reaches more than 60% of the design strength, the SMA stranded wire is connected to the extended conductor and then to AC power. The SMA stranded wire is heated by electricity, with the temperature controlled within the range of 200-250 degrees Celsius. Driven by its shape memory effect, the SMA stranded wire will generate prestress due to its recovery deformation. The shrinkage prestress amplitude is no more than 200 MPa, thereby applying prestress to the precast composite slab.

[0042] The rectangular ribs (beams) extend through the upper part of the entire base slab. The rectangular ribs are used in combination with the truss reinforcement. The spacing between the rectangular ribs is 400mm-700mm. The number of rectangular ribs on a one-way slab should not be less than 3. The rectangular ribs in the main load-bearing direction of a two-way slab should be appropriately densified. The spacing between the rectangular ribs should not be greater than 500mm, and the number should not be less than 4. The distance between the outermost rectangular rib of the one-way slab and the edge of the composite slab should not be greater than 200mm. Example 5

[0043] like Figure 1 As shown, the present invention relates to a precast composite slab of ECC-high-strength stainless steel stranded wire / SMA stranded wire with rectangular ribs-truss reinforcement and post-cast recycled concrete, comprising a base slab 1 and a post-cast layer 2. The base slab 1 includes a base slab transverse stranded wire 101, a base slab longitudinal stranded wire 102, rectangular ribs 103, truss reinforcement 104, and ECC 105 made of high-strength stainless steel stranded wire / SMA stranded wire. The post-cast layer 2 can be recycled concrete. The rectangular ribs 103 are disposed at the truss reinforcement 104 on the base slab. The base slab transverse stranded wire 101 and base slab longitudinal stranded wire 102 are fixed to the base slab template by aluminum clips and slip bolts to form a stranded wire mesh. The truss reinforcement is as follows: Figure 4 As shown, the truss reinforcement bars are tied to the bottom stranded wire mesh using tie wire.

[0044] like Figures 2-3As shown, the bottom plate stranded wire mesh is made of high-strength stainless steel stranded wire or partially replaced by SMA stranded wire. The replacement quantity should be adjusted according to specific design requirements. Therefore, the bottom horizontal stranded wire includes bottom horizontal steel stranded wire and bottom horizontal SMA stranded wire, and the bottom vertical stranded wire includes bottom vertical steel stranded wire and bottom vertical SMA stranded wire. Figure 2 As shown, some of the longitudinal steel strands in the one-way slab are replaced with SMA stranded wire; as Figure 3 As shown, some of the longitudinal and transverse steel strands of the two-way slab are replaced with SMA strands.

[0045] like Figures 2-3 As shown, the one-way slab is arranged with truss reinforcement and rectangular ribs in the longitudinal direction, and the two-way slab is arranged with truss reinforcement and rectangular ribs in both the transverse and longitudinal directions; the width of the rectangular rib is 100-250mm, and the height of the rectangular rib is 40mm; the truss reinforcement extends 10-20mm above the rectangular rib.

[0046] The diameter of the high-strength stainless steel stranded wire and SMA stranded wire is not less than 3.6 mm and not more than 6 mm. The diameter of the transverse stranded wire of the unidirectional plate bottom plate is smaller than the diameter of the longitudinal stranded wire of the bottom plate. The diameters of the transverse stranded wire and the longitudinal stranded wire of the bidirectional plate bottom plate are the same.

[0047] like Figure 5 As shown, the base plate template includes a steel plate, a limiting angle steel and a fixing angle steel. The limiting angle steel and the fixing angle steel are fixed to the steel plate with bolts. The limiting angle steel has a limiting hole, and the fixing angle steel has a fixing slot. The fixing angle steel is arranged around the periphery of the limiting angle steel and the two are spaced apart by a distance of not less than 80mm.

[0048] like Figure 6 As shown, when fixing the base plate strands, first pass the end of the strand through the limiting hole of the limiting angle steel, fix the slip bolt to the end of the strand with an aluminum buckle, then put the threaded section of the slip bolt into the fixing slot on the fixing angle steel and tighten the nut until the strand is taut. In this way, the horizontal strands and the vertical strands of the base plate are alternately fixed on the base plate template to form a strand mesh. Example 6

[0049] A construction method for a precast composite slab of ECC-high-strength stainless steel stranded wire / SMA stranded wire with rectangular rib-truss reinforcement and post-cast recycled concrete, the construction process of which includes the following steps: Step S1: Fix the limiting angle steel and the fixing angle steel to the steel plate according to the design dimensions. Pass the end of the stranded wire through the limiting hole of the limiting angle steel. Fix the end of the stranded wire to the fixing slot on the fixing angle steel with aluminum buckles and slip bolts. Use this method to alternately fix the transverse stranded wire and the longitudinal stranded wire of the bottom plate to the bottom plate template. Finally, tie the truss reinforcement and the bottom plate stranded wire mesh with tie wire. Step S2: Place concrete protective layer pads at the bottom of the bottom plate stranded wire mesh. After confirming that everything is correct, pour the mixed ECC to the height of the bottom plate. Fill the remaining positions on the bottom plate where rectangular ribs are set with long wooden strips. Finally, pour the mixed ECC to the height of the rectangular ribs in the empty positions of the long wooden strips. Step S3: After the ECC surface has initially set, use a wooden toothed brush to manually roughen the surface of the specimen to meet the rough surface requirements in the design specifications.

[0050] Step S4: Use the precast base slab as the bottom formwork, and set up side formwork around it as the formwork for the subsequent concrete pouring. Then tie and fix the structural steel mesh in the subsequent pouring layer, and pour the prepared recycled concrete on the base slab.

[0051] Compared to existing technologies, this invention utilizes a combination of truss reinforcement and rib strips, which effectively improves the bending resistance and sectional stiffness of the precast composite slab floor. The floor of the precast composite slab is constructed using a combination of SMA strands and steel strands with ECC. ECC possesses excellent crack control and crack dispersion capabilities, and its combination with SMA strand prestressing effectively reduces deflection during the construction phase of the precast composite slab. This prevents early cracking damage at the bottom of large-span precast composite slabs during construction and normal use, thus improving the crack resistance of large-span precast composite slabs. The use of recycled concrete meets the application requirements of large-span, high-load structures while also considering resource recycling and environmental protection.

[0052] Of course, the above description is only a preferred embodiment of the present invention and does not constitute a limitation of the present invention. Those skilled in the art, guided by existing technology, can make other modifications to the implementation of the present invention without creative effort. Any modifications made within the spirit and principles of the present invention, or simple substitutions or equivalent replacements made using conventional techniques in the art, should be included within the protection scope of the present invention.

Claims

1. A prestressed large-span composite slab with a precast ECC base slab and a post-cast GRC composite layer, comprising a base slab (1) and a post-cast layer. (2), characterized in that: The base plate (1) is integrally cast using ECC material and a base plate stranded wire mesh. The base plate stranded wire mesh consists of transverse strands and The longitudinal strands are fixed to the base plate template to form the structure; The base plate stranded wire mesh is made of a combination of high-strength stainless steel stranded wire and SMA stranded wire at intervals. The base plate (1) is provided with rectangular ribs (103), which are integrally cast with the base plate by means of truss steel bars (104); the truss steel bars (104) are tied to the base plate wire mesh by means of tie wire. The post-cast layer (2) is located above the base plate (1) and is cast using concrete or recycled concrete; The SMA stranded wire area design adopts the method of replacing steel strands with equal area or equal strength. When replacing with equal area, the SMA stranded wire is selected with the same diameter as the steel stranded wire, and the replacement area is no more than 50%. When replacing with strength, the diameter of the SMA stranded wire should be larger than that of the steel stranded wire to ensure a consistent number of replacement strands. Before construction, the SMA stranded wire is connected to the conductor, which extends beyond the precast composite slab. After the precast composite slab is completed, once the concrete strength reaches 60% of the design strength, the extended conductor of the SMA stranded wire is connected to AC power. The SMA stranded wire is then heated, with the temperature controlled within the range of 200-250 degrees Celsius. Driven by its shape memory effect, the SMA stranded wire will generate prestress due to its recovery deformation. The prestress amplitude is not greater than 200MPa, and prestress is applied to the precast composite slab; the base plate template (3) includes a steel plate, a limiting angle steel and a fixing angle steel. The limiting angle steel and the fixing angle steel are fixed to the steel plate with bolts. The limiting angle steel has a limiting hole, and the fixing angle steel has a fixing slot. The fixing angle steel is arranged around the periphery of the limiting angle steel and the two are spaced apart by not less than 80mm; when fixing the base plate strands, first pass the end of the base plate strands through the limiting hole of the limiting angle steel, fix the slip bolt to the end of the base plate strands with an aluminum buckle, then put the threaded section of the slip bolt into the fixing slot on the fixing angle steel, and tighten the nut until the base plate strands are taut. In this way, the transverse strands and longitudinal strands of the base plate are alternately fixed on the base plate template to form a base plate strand net.

2. The prestressed large-span composite slab with precast ECC base plate and post-cast GRC composite layer as described in claim 1, characterized in that: The rectangular rib (103) has a width of 100-250mm and a height of 40mm; the number of rectangular ribs on the one-way plate is not less than 3, and the spacing between the rectangular ribs is 400mm-700mm; the number of rectangular ribs on the two-way plate is not less than 4, the spacing between the rectangular ribs is not greater than 500mm, and the distance between the outermost rectangular rib of the one-way plate and the two-way plate and the edge of the composite plate is not greater than 200mm.

3. The prestressed large-span composite slab with precast ECC base plate and post-cast GRC composite layer as described in claim 2, characterized in that: The truss reinforcement extends 10-20mm above the rectangular ribs.

4. The prestressed large-span composite slab with precast ECC base plate and post-cast GRC composite layer according to any one of claims 1-3, characterized in that: The diameter of the high-strength stainless steel stranded wire and SMA stranded wire is not less than 3.6 mm and not more than 6 mm. The diameter of the transverse stranded wire of the unidirectional plate bottom plate is smaller than the diameter of the longitudinal stranded wire of the bottom plate. The diameters of the transverse stranded wire and the longitudinal stranded wire of the bidirectional plate bottom plate are the same.

5. The prestressed large-span composite slab with precast ECC base plate and post-cast GRC composite layer as described in claim 4, characterized in that: The one-way slab has truss reinforcement and rectangular ribs arranged in the longitudinal direction, while the two-way slab has truss reinforcement and rectangular ribs arranged in both the transverse and longitudinal directions.

6. A construction method for a prestressed large-span composite slab with a precast ECC base slab and a post-cast GRC composite layer as described in claim 1, characterized in that, The process includes The following steps are required: Step S1: Fix the limiting angle steel and the fixing angle steel to the steel plate according to the design dimensions. Pass the end of the stranded wire through the limiting hole of the limiting angle steel. Fix the end of the stranded wire to the fixing slot on the fixing angle steel with aluminum buckles and slip bolts. Use this method to alternately fix the transverse stranded wire and the longitudinal stranded wire of the bottom plate to the bottom plate template. Finally, tie the truss reinforcement and the bottom plate stranded wire mesh with tie wire. Step S2: Place concrete protective layer pads at the bottom of the bottom plate stranded wire mesh. After confirming that everything is correct, pour the mixed ECC to the height of the bottom plate. Fill the remaining positions on the bottom plate where rectangular ribs are set with long wooden strips. Finally, pour the mixed ECC to the height of the rectangular ribs in the empty positions of the long wooden strips. Step S3: After the ECC surface has initially set, the surface of the specimen is artificially roughened using a wooden toothed brush to meet the rough surface requirements in the design specifications. Step S4: Use the precast base slab as the bottom formwork, and set up the side formwork around it as the formwork for the subsequent concrete pouring. Then tie and fix the structural steel mesh in the subsequent pouring layer, and pour the mixed recycled concrete on the base slab. After the concrete strength of the composite slab in step S4 reaches 60% of the design strength, the extended conductor of the SMA stranded wire is connected to the AC power supply. The SMA stranded wire is heated by electricity, and the temperature rise range is controlled between 200-250 degrees Celsius. Driven by its shape memory effect, the SMA stranded wire will generate a prestress of no more than 200 MPa due to the recovery deformation, thereby completing the active application of prestress to the precast composite slab.

7. The construction method of the prestressed large-span composite slab with precast ECC base slab and post-cast GRC composite layer according to claim 6, characterized in that: The rectangular ribs extend through the upper part of the entire base plate and are used in combination with the truss reinforcement. The spacing between the rectangular ribs is 400mm-700mm. There are no less than 3 rectangular ribs on a one-way plate. The rectangular ribs in the main load-bearing direction of the two-way plate are appropriately densified. The spacing between the rectangular ribs is no more than 500mm and the number is no less than 4. The outermost rectangular rib of the one-way plate and the two-way plate is no more than 200mm away from the edge of the composite plate.

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