A UHPC-recycled block-aggregate concrete composite floor slab system and its construction method

Abstract

This application discloses a UHPC-recycled block-aggregate concrete composite floor slab system and its construction method, relating to the field of building construction floor slab technology. It includes: a minimal formwork and minimal support system; a UHPC precast base slab laid on the minimal formwork and minimal support system, with the top perimeter of the UHPC precast base slab extending upwards to form a casting groove; and a cast-in-place recycled concrete layer poured into and tightly bonded to the UHPC precast base slab within the casting groove. The cast-in-place recycled concrete layer includes: multiple recycled concrete blocks as fillers; a reinforcing mesh for resisting tensile forces; and recycled aggregate concrete encasing the recycled concrete blocks and the reinforcing mesh. This application eliminates the need for full-span scaffolding and formwork, requiring only formwork at the joints of the slabs, reducing the use of wooden formwork and supports. It breaks away from conventional uses of waste for manufacturing recycled boards and road paving, significantly expanding the application scope of construction waste.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building construction floors, in particular to a UHPC-recycled block-aggregate concrete composite floor system and a construction method thereof. BACKGROUND

[0002] Ultra-high performance concrete (UHPC) is a cement-based composite material characterized by ultra-high strength, high toughness and high durability, which is composed of steel fiber, silica fume, quartz powder, etc., and has the characteristics of low water-binder ratio (0.15-0.25) and no coarse aggregate by optimizing the particle size distribution according to the maximum packing density theory, and the compressive strength can reach more than 400 MPa.

[0003] At present, the construction of building floors mainly adopts two ways of cast-in-place concrete and prefabricated concrete.

[0004] The traditional cast-in-place concrete floor needs to set up full-formwork and support scaffolding on site, which consumes a large amount of wood or steel resources, has a long construction period, and has many wet operations on site, and is prone to quality defects such as honeycomb and pitted surface at the bottom of the floor.

[0005] Although the conventional prefabricated concrete floor improves the production efficiency, the ordinary concrete components are heavy and have poor toughness, and are prone to cracking and damage during transportation and hoisting, resulting in a high scrap rate. In addition, the connection nodes between the prefabricated boards are usually complex, and improper handling will affect the integrity of the structure.

[0006] At the same time, with the acceleration of urbanization, the amount of waste concrete produced by building demolition is huge. The traditional treatment method is mainly to crush it into recycled aggregate for roadbed filling or production of low-grade recycled concrete. This treatment method has high energy consumption and low added value of recycled products. How to efficiently and highly utilize these waste concrete is a technical problem to be solved for realizing the "double carbon" goal and sustainable development of the construction industry. SUMMARY

[0007] In order to reduce the use of wood formwork, support, etc., the application provides a UHPC-recycled block-aggregate concrete composite floor system and a construction method thereof.

[0008] In the first aspect, the application provides a UHPC-recycled block-aggregate concrete composite floor system, which adopts the following technical scheme:

[0009] A UHPC-recycled block-aggregate concrete composite floor system, which comprises the following structure from bottom to top:

[0010] A few-formwork and few-support system;

[0011] The UHPC prefabricated bottom plate is laid on the few-formwork and few-support system and guarantees the level of the plate surface, the top of the UHPC prefabricated bottom plate extends upwards around and forms a pouring groove;

[0012] The cast-in-place recycled mixed concrete layer is poured into the pouring groove of the UHPC prefabricated bottom plate and is tightly combined with the UHPC prefabricated bottom plate;

[0013] The cast-in-place recycled mixed concrete layer comprises:

[0014] A plurality of recycled concrete blocks as fillers;

[0015] A steel mesh for resisting tension;

[0016] Recycled aggregate concrete wrapping the recycled concrete blocks and the steel mesh;

[0017] The few-formwork and few-support system comprises support columns for transmitting loads to a support surface, top supports arranged on the support columns, transverse steel pipes arranged on the top supports, wooden battens arranged on the transverse steel pipes, plate joint formworks arranged on the wooden battens and located at the bottom of the plate joints of the UHPC prefabricated bottom plate, and sealing rubber strips arranged in transverse grooves at the top of the plate joint formworks, the plate joint formworks are arranged along the length direction of the plate joints, the thickness of the sealing rubber strips is greater than the depth of the transverse grooves, and the sealing rubber strips seal the bottom of the plate joints of the UHPC prefabricated bottom plate.

[0018] After the cast-in-place recycled mixed concrete layer is poured into the pouring groove of the UHPC prefabricated bottom plate, the UHPC prefabricated bottom plate itself serves as a formwork and independently bears all loads of the upper part, including the self weight of the upper cast-in-place concrete and construction loads, and the UHPC prefabricated bottom plate transmits the loads to the few-formwork and few-support system. The present application does not need to set up full scaffolding and formworks, only needs to set up plate joint formworks at the intersection of the plate joints (plate beams), and only needs a small amount of supports to form a few-support system, thereby reducing the use of wooden formworks, supports and the like, saving resources and reducing the engineering cost. Moreover, the setting-up time of the formworks and supports is reduced, thereby reducing the construction period; the UHPC prefabricated bottom plate itself serves as a formwork and independently bears all loads of the upper part, including the self weight of the upper cast-in-place concrete and construction loads, and the UHPC prefabricated bottom plate transmits the loads to the plate joint formworks, the wooden battens, the transverse steel pipes, the top supports and the support columns in turn, and finally transmits the loads to the support surface. In the process that the UHPC prefabricated bottom plate itself serves as a formwork and independently bears all loads of the upper part, the UHPC prefabricated bottom plate can extrude the sealing rubber strips downwards, so that the bottom of the UHPC prefabricated bottom plate is tightly combined with the plate joint formworks and the top of the sealing rubber strips is fully in contact with the plate joints.

[0019] Optionally, the top surface of the UHPC prefabricated bottom plate is provided with a rough surface, and the steel bar net comprises web steel bars partially embedded in the UHPC prefabricated bottom plate, lower chord steel bars arranged at the bottom of the web steel bars, upper chord steel bars arranged at the top of the web steel bars, plate lower steel bars arranged at the middle part of the web steel bars, and plate upper steel bars arranged at the top of the web steel bars.

[0020] By adopting the above technical scheme, the web steel bars mainly bear the shear force and local bending moment in the structure, the web steel bars, the upper chord steel bars and the lower chord steel bars jointly form a triangular stable system to enhance the overall rigidity of the structure; the lower chord steel bars mainly bear the axial tension, and can compensate for the defect of insufficient tensile strength of the recycled aggregate concrete; the plate lower steel bars bear the positive bending moment tension generated by the self weight and live load of the floor slab to prevent the recycled aggregate concrete from cracking due to tension, and the plate upper steel bars bear the negative bending moment tension to avoid cracking of the recycled aggregate concrete.

[0021] Optionally, the adjacent UHPC prefabricated bottom plates are spliced through plate joints, the end part of the adjacent UHPC prefabricated bottom plates is provided with a plurality of interval arranged accommodation grooves and placement grooves near the plate joints, the placement grooves are provided with rear concrete placement blocks, the rear concrete placement blocks are connected through hollow steel pipes, the accommodation grooves are for the hollow steel pipes to pass through, and the placement groove walls and the rear concrete placement block side walls are left with gaps.

[0022] By adopting the above technical scheme, after the steel bar net is installed on the UHPC prefabricated bottom plate and before the recycled concrete blocks are placed, the hollow steel pipes are poured with concrete to form a concrete filled steel tube structure, the concrete filled steel tube structure restrains the internal concrete through the hollow steel pipes, so that the concrete is in a three-way compression state, the longitudinal cracking is delayed, and the compressive strength is improved. Moreover, due to the arrangement of the placement grooves, the accommodation grooves, the rear concrete placement blocks and the hollow steel pipes, the subsequent poured recycled aggregate concrete can improve the contact parts between the rear concrete placement blocks, the hollow steel pipes and the UHPC prefabricated bottom plate, so as to not only improve the connection strength between the adjacent UHPC prefabricated bottom plates, but also improve the connection strength between the UHPC prefabricated bottom plate and the recycled aggregate concrete.

[0023] Optionally, the two ends of the hollow steel pipe extend upward and are provided with external threads, the two ends of the hollow steel pipe are respectively connected with an injection pipe and an exhaust pipe through the external threads, a plurality of communication holes are arranged along the radial direction and the circumferential direction of the hollow steel pipe, the diameter of the communication hole gradually decreases from the inner pipe wall to the outer pipe wall of the hollow steel pipe, and a vortex groove in a vortex shape is arranged at the hole wall of the communication hole.

[0024] By adopting the technical scheme, after the UHPC prefabricated bottom plate is installed, the post-concrete placement block is placed in the placement groove, then the injection pipe is connected with the external concrete pouring system, the hollow steel pipe is poured with concrete, the air in the hollow steel pipe is discharged through the communication hole and the exhaust pipe, and the hollow steel pipe, the communication hole and the communication needle pipe are filled with the poured concrete, and then the pouring of the concrete in the hollow steel pipe is stopped. When the recycled aggregate concrete is poured subsequently, since there may be a little air bubble remaining in the placement groove and the accommodation groove, when the recycled aggregate concrete is poured and vibrated, the hollow steel pipe can be continuously injected with the concrete through the external concrete pouring system, so that the concrete in the hollow steel pipe can be discharged through the communication hole, thereby the air bubble in the recycled aggregate concrete can be removed more smoothly under the cooperation of the vibration operation, and the pouring compactness of the recycled aggregate concrete is improved.

[0025] Optionally, the concrete cushion blocks are arranged around the bottom of the post-concrete placement block, spaces are left between the concrete cushion blocks and the side walls of the post-concrete placement block, the hollow steel pipe is provided with a communication needle pipe in communication with the communication hole, and the communication needle pipe is located in the post-concrete placement block and penetrates the outer side of the post-concrete placement block at the end.

[0026] By adopting the technical scheme, since the bottom of the post-concrete placement block is provided with the plurality of concrete cushion blocks, the first layer of poured recycled aggregate concrete can flow smoothly to the bottom position of the post-concrete placement block, so as to reduce the phenomenon that air bubbles are left at the bottom of the post-concrete placement block.

[0027] Optionally, the foot pads are arranged around the bottom of the recycled concrete block, and spaces are left between the foot pads and the side walls of the recycled concrete block.

[0028] By adopting the technical scheme, the distance is left between the bottom surface of the recycled concrete block and the top surface of the UHPC prefabricated bottom plate, so that the recycled aggregate concrete poured subsequently can be better filled to the bottom position of the UHPC prefabricated bottom plate, so as to reduce the air bubbles in the cast-in-place recycled mixed concrete layer.

[0029] In the second aspect, the application provides a construction method of a UHPC-recycled block-aggregate concrete composite floor system, which adopts the following technical scheme, and the construction method comprises the following steps:

[0030] S1. erecting a few-formwork few-support system, and the few-formwork few-support system is provided with supports only below the plate joints of the UHPC prefabricated bottom plate;

[0031] S2. installing the UHPC prefabricated bottom plate on the few-formwork few-support system, so that the adjacent UHPC prefabricated bottom plates are tightly attached to each other;

[0032] S3. binding the steel bar mesh on the UHPC prefabricated bottom plate;

[0033] S4. Placing recycled concrete blocks in the space between the reinforcement mesh, pouring and vibrating the recycled aggregate concrete to form the cast-in-place recycled hybrid concrete layer;

[0034] S5. Curing the completed floor slab.

[0035] Optionally, in step S4, after the UHPC prefabricated bottom plate is installed, the back concrete placement block is placed in the placement groove, the hollow steel pipe passes through the accommodation groove, then the injection pipe and the exhaust pipe are respectively installed at both ends of the hollow steel pipe, the injection pipe is connected with the external concrete pouring system, the concrete is poured into the hollow steel pipe, the air in the hollow steel pipe is discharged through the communication hole and the exhaust pipe, and the hollow steel pipe and the communication hole are filled with the poured concrete, and then the pouring of the concrete in the hollow steel pipe is stopped.

[0036] Optionally, in step S5, when pouring the recycled aggregate concrete, first, pour the first layer of recycled aggregate concrete on all UHPC prefabricated bottom plates so that the first layer of poured recycled aggregate concrete immerses the bottom of the reinforcement mesh, then uniformly place the recycled concrete blocks, and pour the second layer of recycled aggregate concrete before the first layer of recycled aggregate concrete is initially cured; when pouring the second layer of recycled aggregate concrete, the pouring is carried out in a regional manner, the recycled aggregate concrete is first poured on one side of the first layer of recycled aggregate concrete, then the mixture of the recycled concrete blocks and the recycled aggregate concrete is fully vibrated, so that the area of the second layer of recycled aggregate concrete not in contact with the inner side wall of the UHPC prefabricated bottom plate flows to the slope state, then the second area is poured, and the mixture of the recycled concrete blocks and the recycled aggregate concrete in the second area is vibrated in the same manner until the pouring of the entire cast-in-place recycled hybrid concrete layer is completed.

[0037] In summary, the present application includes at least one of the following beneficial technical effects:

[0038] 1. The present application does not need to set up full scaffolding and formwork, only needs to set up slab joint formwork at the intersection of slab joints (slab beams), the support only needs a small amount, forms a small support system, reduces the use of wooden formwork, support and the like, saves resources, and reduces engineering cost. And because the setting time of the formwork and the support is reduced, the construction period can be reduced;

[0039] 2. After the cast-in-place recycled hybrid concrete layer is poured in the pouring groove of the UHPC prefabricated bottom plate, the UHPC prefabricated bottom plate itself serves as a formwork and independently bears all the loads above, including the self-weight of the upper cast-in-place concrete and the construction load, and the UHPC prefabricated bottom plate transmits the load to the small formwork and small support system;

[0040] 3. The recycled aggregate concrete is prepared by cleaning, crushing and screening waste concrete to form recycled blocks and recycled coarse aggregate, and the recycled aggregate concrete comprises recycled coarse aggregate, natural coarse aggregate, recycled sand and natural fine aggregate mixed in a certain proportion; the recycled sand is formed by water washing and drying alluvium or granite weathered residual soil; the energy consumption of the recycled waste treatment is low, only large-size blocks are needed, the recycling rate of the recycled waste is high, the conventional waste is broken for manufacturing recycled boards, filling roads and other purposes, and the application range of the construction waste is greatly expanded. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 is a structural schematic diagram of a UHPC-recycled block-aggregate concrete composite floor system;

[0042] Figure 2 is a structural schematic diagram of a UHPC-recycled block-aggregate concrete composite floor system with a few formworks and a few supports;

[0043] Figure 3 is a sectional view of a cast-in-situ recycled mixed concrete layer of a UHPC-recycled block-aggregate concrete composite floor system;

[0044] Figure 4 is a sectional view of a cast-in-situ recycled mixed concrete layer of a UHPC-recycled block-aggregate concrete composite floor system with a few formworks and a few supports;

[0045] Figure 5 is another angle of a sectional view of a cast-in-situ recycled mixed concrete layer of a UHPC-recycled block-aggregate concrete composite floor system with a few formworks and a few supports;

[0046] Figure 6 is a structural schematic diagram of a web bar of a UHPC-recycled block-aggregate concrete composite floor system;

[0047] Figure 7 is a top view of a UHPC prefabricated bottom plate of a UHPC-recycled block-aggregate concrete composite floor system;

[0048] Figure 8 is a structural schematic diagram of a UHPC prefabricated bottom plate of a UHPC-recycled block-aggregate concrete composite floor system;

[0049] Figure 9 is a structural schematic diagram of a back concrete placement block and a hollow steel pipe of a UHPC-recycled block-aggregate concrete composite floor system;

[0050] Figure 10 is a sectional view of a back concrete placement block of a UHPC-recycled block-aggregate concrete composite floor system;

[0051] Figure 11 is a structural schematic diagram of the first layer of recycled aggregate concrete paving of the UHPC-recycled block-aggregate concrete composite floor system;

[0052] Figure 12 is a structural schematic diagram of the second layer of recycled aggregate concrete paving of the UHPC-recycled block-aggregate concrete composite floor system.

[0053] BRIEF DESCRIPTION OF DRAWINGS: 1, less formwork and less support system; 11, support column; 12, top support; 13, transverse steel pipe; 14, wood block; 15, plate joint formwork; 16, sealing rubber strip; 17, transverse groove; 2, UHPC prefabricated bottom plate; 21, displacement groove; 22, placement groove; 23, back concrete placement block; 231, concrete cushion block; 24, hollow steel pipe; 241, injection pipe; 242, exhaust pipe; 243, communication hole; 2431, vortex groove; 244, communication needle pipe; 3, cast-in-place recycled mixed concrete layer; 31, recycled concrete block; 32, steel mesh; 321, web steel bar; 322, lower chord steel bar; 323, upper chord steel bar; 324, plate lower steel bar; 325, plate upper steel bar; 33, recycled aggregate concrete. DETAILED DESCRIPTION

[0054] The following will be described in detail with reference to the accompanying drawings Figures 1-12 The present application is further described in detail.

[0055] The embodiments of the present application disclose a UHPC-recycled block-aggregate concrete composite floor system. Referring to Figure 1 and Figure 2 , the UHPC-recycled block-aggregate concrete composite floor system comprises a less formwork and less support system 1, a UHPC prefabricated bottom plate 2 and a cast-in-place recycled mixed concrete layer 3 arranged from bottom to top, the UHPC prefabricated bottom plate 2 is paved on the less formwork and less support system 1, the UHPC prefabricated bottom plate 2 is horizontally arranged, the four sides of the top of the UHPC prefabricated bottom plate 2 extend upward and form a cuboid pouring groove, the cast-in-place recycled mixed concrete layer 3 is poured into the pouring groove of the UHPC prefabricated bottom plate 2, and the cast-in-place recycled mixed concrete layer 3 is tightly combined with the pouring groove of the UHPC prefabricated bottom plate 2. It should be noted that the less formwork and less support system 1 is provided with supports only below the plate joints of the UHPC prefabricated bottom plate 2.

[0056] Referring to Figure 3 , the cast-in-place recycled mixed concrete layer 3 comprises recycled concrete blocks 31, a steel mesh 32 and recycled aggregate concrete 33, the recycled aggregate concrete 33 is the main material in the cast-in-place recycled mixed concrete layer 3, and the steel mesh 32 and the recycled concrete blocks 31 are the fillers in the cast-in-place recycled mixed concrete layer 3, and the recycled concrete blocks 31 are used for wrapping the recycled concrete blocks 31 and the steel mesh 32.

[0057] The UHPC prefabricated bottom plate 2 is a finished prefabricated component, and the width of the standard plate is generally 1200mm, and the length can be customized according to the structure plane and is generally less than 3600mm. Compared with the ordinary prefabricated floor, the UHPC prefabricated bottom plate 2 has the characteristics of high strength and high performance, the compressive strength is higher than that of ordinary concrete, and it also has a certain tensile strength, is not easy to be damaged during transportation and hoisting, can independently bear part of the load, and reduces the support at the bottom.

[0058] The UHPC prefabricated bottom plate 2 is a prefabricated product plate, and the construction quality is guaranteed. After construction, it is not necessary to remove it, the visual effect of the floor bottom is good, and the problems of honeycomb and hole at the bottom of the recycled block aggregate concrete floor are avoided.

[0059] Referring to Figure 4 and Figure 5 , preferably, the few-formwork and few-support system 1 comprises a support column 11, a top support 12, a horizontal steel pipe 13, a wood block 14, a plate joint formwork 15 and a sealing rubber strip 16. The support column 11 is vertically arranged, the bottom of the support column 11 is connected with a support surface, the top support 12 is fixed to the top of the support column 11, the cross section of the top support 12 is in the shape of “N”, the length direction of the top support 12 is parallel to the length direction of the plate joint, the horizontal steel pipe 13 is horizontally installed in the top support 12, the number of the horizontal steel pipes 13 in each top support 12 is two, the length direction of the horizontal steel pipe 13 is parallel to the length direction of the top support 12, the wood block 14 is horizontally installed on the top of the plurality of horizontal steel pipes 13, the wood block 14 is linearly arranged in multiple along the length direction of the plate joint, the plate joint formwork 15 is horizontally installed on the top of the plurality of wood blocks 14, a horizontal groove 17 is formed on the top of the plate joint formwork 15 corresponding to the position of the plate joint, the length direction of the horizontal groove 17 is parallel to the extension direction of the plate joint, and the sealing rubber strip 16 is installed in the horizontal groove 17, and the thickness of the sealing rubber strip 16 is slightly greater than the depth of the horizontal groove 17. The sealing rubber strip 16 can seal the bottom of the plate joint of the UHPC prefabricated bottom plate 2.

[0060] It should be noted that since the pouring area of the floor may be large, the UHPC prefabricated bottom plate 2 of the present application needs to be spliced by multiple UHPC prefabricated bottom plates 2, and the number of UHPC prefabricated bottom plates 2 used can be adjusted according to the area of the floor. In this embodiment, the UHPC prefabricated bottom plate 2 is spliced by six plate bodies, and a plate joint is formed between the two adjacent UHPC prefabricated bottom plates 2. In addition, the present application only needs to set up a plate joint formwork 15 at the intersection of the plate joints (plate beams), and the remaining support structure is the existing structure for supporting the column and beam.

[0061] The cast-in-place recycled mixed concrete layer 3 is poured after the pouring groove of the UHPC prefabricated bottom plate 2, the UHPC prefabricated bottom plate 2 itself serves as a formwork and independently bears all the loads of the upper part, including the self-weight of the upper cast-in-place concrete and the construction load, and the UHPC prefabricated bottom plate 2 sequentially transmits the load to the plate joint formwork 15, the wood block 14, the transverse steel pipe 13, the top support 12 and the support column 11. The application makes full use of the characteristics of high strength and high performance of the UHPC prefabricated bottom plate 2, and the UHPC prefabricated bottom plate 2 itself serves as a formwork and independently bears all the loads of the upper part, including the self-weight of the upper cast-in-place concrete and the construction load. The application does not need to set up full scaffolding and formwork, only needs to set up a plate joint formwork 15 at the intersection of the plate joint (plate beam), and the support is only a small amount, forming a small support system, reducing the use of wood formwork, support and the like, saving resources and reducing engineering cost. And because the setting time of the formwork and support is reduced, the construction period can be reduced.

[0062] In the process of the UHPC prefabricated bottom plate 2 itself serving as a formwork and independently bearing all the loads of the upper part, the UHPC prefabricated bottom plate 2 can extrude the sealing strip 16 downward, so that the bottom of the UHPC prefabricated bottom plate 2 is tightly attached to the plate joint formwork 15, and the top of the sealing strip 16 is in full contact with the plate joint, not only enabling the load on the UHPC prefabricated bottom plate 2 to be smoothly transmitted to the plate joint formwork 15, but also enabling the sealing strip 16 to fully seal the bottom of the plate joint of the UHPC prefabricated bottom plate 2.

[0063] Referring to Figure 5 and Figure 6 , preferably, the top surface of the UHPC prefabricated bottom plate 2 is provided with a rough surface, the steel bar mesh 32 includes web steel bars 321, lower chord steel bars 322, upper chord steel bars 323, plate lower steel bars 324 and plate upper steel bars 325, the web steel bars 321 are arranged in a wave shape, and the bottom of the web steel bars 321 is embedded in the UHPC prefabricated bottom plate 2, the lower chord steel bars 322 are bound at the bottom position of the web steel bars 321, the upper chord steel bars 323 are bound at the top position of the web steel bars 321, the lower chord steel bars 322 and the upper chord steel bars 323 are horizontally arranged, and the length direction of the lower chord steel bars 322 is parallel to the length direction of the upper chord steel bars 323, the plate lower steel bars 324 are installed at the middle position of the web steel bars 321, and the plate upper steel bars 325 are installed at the top position of the web steel bars 321. It should be noted that a space is left between the two adjacent groups of web steel bars 321, which is used for subsequent placement of recycled concrete blocks 31.

[0064] Before pouring the recycled aggregate concrete 33, the lower chord steel bars 322, the upper chord steel bars 323, the slab lower steel bars 324 and the slab upper steel bars 325 are bound to form a complete steel bar net 32, after the recycled aggregate concrete 33 is solidified, the web steel bars 321 mainly bear the shear force and local bending moment in the structure, the web steel bars 321 and the upper chord steel bars 323 and the lower chord steel bars 322 together constitute a triangular stable system to enhance the overall rigidity of the structure, the upper chord steel bars 323 mainly bear the axial pressure, the upper chord steel bars 323 and the recycled aggregate concrete 33 together resist the pressure to prevent the crushed recycled aggregate concrete 33 in the compression zone, at the same time, the recycled aggregate concrete 33 is constrained from transverse deformation to improve the local compressive strength; the lower chord steel bars 322 mainly bear the axial tension, the lower chord steel bars 322 can make up for the defects of insufficient tensile strength of the recycled aggregate concrete 33, bear the tension generated when the structure is bent, and avoid the cracking or fracture of the recycled aggregate concrete 33 in the tension zone; the slab lower steel bars 324 bear the positive bending moment tension generated by the self-weight and live load of the slab to prevent the recycled aggregate concrete 33 from cracking due to tension, and the slab upper steel bars 325 can bear the negative bending moment tension to avoid the cracking of the recycled aggregate concrete 33, which acts as a temperature bar or anti-cracking bar to prevent the recycled aggregate concrete 33 from generating surface cracks due to temperature changes and shrinkage.

[0065] With reference to Figure 7 And Figure 8 Further, the end of each adjacent UHPC prefabricated bottom plate 2 near the plate joint is provided with a plurality of accommodation grooves 21 and placement grooves 22, and the plurality of accommodation grooves 21 and placement grooves 22 are arranged at intervals. In this embodiment, the depth of the accommodation groove 21 is one fourth of the thickness of the UHPC prefabricated bottom plate 2, and the depth of the placement groove 22 is one half of the thickness of the UHPC prefabricated bottom plate 2. The placement groove 22 is provided with a plurality of rear concrete placement blocks 23, and the plurality of rear concrete placement blocks 23 are fixed by a hollow steel pipe 24. The hollow steel pipe 24 penetrates through the plurality of rear concrete placement blocks 23, the accommodation groove 21 is used for the hollow steel pipe 24 to pass through, and the gap is left between the groove wall of the placement groove 22 and the side wall of the rear concrete placement block 23.

[0066] After the steel mesh 32 is installed on the UHPC prefabricated bottom plate 2, and before the recycled concrete blocks 31 are placed, the concrete is poured into the hollow steel pipe 24 to form a steel pipe concrete structure. The steel pipe concrete structure is in a three-way compression state due to the constraint of the internal concrete by the hollow steel pipe 24, which can delay longitudinal cracking and improve the compressive strength. In addition, due to the arrangement of the placing groove 22, the accommodation groove 21, the rear concrete placing block 23, and the hollow steel pipe 24, the subsequent poured recycled aggregate concrete 33 can improve the contact between the rear concrete placing block 23, the hollow steel pipe 24, and the UHPC prefabricated bottom plate 2. This not only improves the connection strength between adjacent UHPC prefabricated bottom plates 2, but also improves the connection strength between the UHPC prefabricated bottom plate 2 and the recycled aggregate concrete 33. At the same time, the internal concrete can effectively prevent the hollow steel pipe 24 from local buckling, and the two work together to improve the bearing capacity. Compared with reinforced concrete, the steel pipe concrete structure combines the bending resistance of steel and the compression resistance of concrete, has smaller cross-sectional size, higher bearing capacity, and better seismic performance, construction performance, and other comprehensive indicators than traditional reinforced concrete structures.

[0067] Preferably, the two ends of the hollow steel pipe 24 extend upward and are provided with external threads. The two ends of the hollow steel pipe 24 are both open, and the height of the two ends of the hollow steel pipe 24 is lower than the height of the edge of the UHPC prefabricated bottom plate 2. The two ends of the hollow steel pipe 24 are connected with an injection pipe 241 and an exhaust pipe 242 through external threads, respectively. The injection pipe 241 and the exhaust pipe 242 are both hollow.

[0068] Referring to Figure 9 and Figure 10 , the hollow steel pipe 24 is provided with a plurality of communication holes 243 along the radial and circumferential directions. The diameter of the communication hole 243 gradually decreases from the inner tube wall to the outer tube wall of the hollow steel pipe 24, and the hole wall of the communication hole 243 is provided with a vortex groove 2431. A plurality of concrete pads 231 are installed around the bottom of the rear concrete placing block 23, and a space is left between the concrete pads 231 and the side wall of the rear concrete placing block 23. A communication needle pipe 244 is fixed outside the hollow steel pipe 24, and the communication needle pipe 244 communicates with the communication hole 243. The communication needle pipe 244 is located inside the rear concrete placing block 23 and its end penetrates the outside of the rear concrete placing block 23. It should be noted that the plurality of plate joint connections are arranged to avoid the hollow steel pipes 24, so that the two hollow steel pipes 24 do not interfere with each other.

[0069] After the UHPC prefabricated bottom plate 2 is installed, the back concrete placement block 23 is placed in the placement groove 22, the hollow steel pipe 24 is passed through the accommodation groove 21, then the injection pipe 241 and the exhaust pipe 242 are respectively installed at both ends of the hollow steel pipe 24, the injection pipe 241 is connected with the external concrete pouring system, the concrete is poured in the hollow steel pipe 24, the air in the hollow steel pipe 24 is discharged through the communication hole 243 and the exhaust pipe 242, and the hollow steel pipe 24, the communication hole 243 and the communication needle pipe 244 are filled with the poured concrete, then the pouring of the concrete in the hollow steel pipe 24 is stopped. When the recycled aggregate concrete 33 is poured subsequently, since there may be a little air bubble remaining in the placement groove 22 and the accommodation groove 21, when the recycled aggregate concrete 33 is poured and vibrated, the concrete can be continuously injected into the hollow steel pipe 24 through the external concrete pouring system, so that the air bubble in the recycled aggregate concrete 33 can be removed more smoothly under the cooperation of the vibration operation, and the pouring density of the recycled aggregate concrete 33 is improved.

[0070] In addition, since the diameter of the inner communication hole 243 of the hollow steel pipe 24 is greater than the diameter of the outer communication hole 243, the flow rate of the concrete flowing out of the hollow steel pipe 24 is increased and the flow line is relatively smooth, the local vortex is less, the flow rate of the concrete flowing out of the hollow steel pipe 24 is improved, in addition, when the air bubble outside the hollow steel pipe 24 enters the communication hole 243 which becomes larger, the flow rate is reduced and the boundary layer separation is easy to be caused, more vortex is generated, the local resistance is significantly increased, thereby reducing the phenomenon that the air bubble outside the hollow steel pipe 24 enters the hollow steel pipe 24.

[0071] It should be noted that since the concrete cushion 231 is installed around the bottom of the back concrete placement block 23, and there is a space between the concrete cushion 231 and the side wall of the back concrete placement block 23, there is a gap between the bottom surface of the back concrete placement block 23 and the groove bottom of the placement groove 22, so that the air bubble at the bottom of the back concrete placement block 23 is easily discharged.

[0072] Further, the foot pad is installed around the bottom of the recycled concrete block 31, and there is an accommodation space between the foot pad and the side wall of the recycled concrete block 31. Since the top surface of the UHPC prefabricated bottom plate 2 is provided with a rough surface, and there is a certain distance between the bottom surface of the recycled concrete block 31 and the top surface of the UHPC prefabricated bottom plate 2, the recycled aggregate concrete 33 poured subsequently can be better filled to the bottom position of the UHPC prefabricated bottom plate 2, so as to reduce the air bubble in the cast-in-place recycled mixed concrete layer 3.

[0073] It should be noted that the UHPC floor slabs in this application do not have reinforcing bars at the edges, making on-site installation quick and easy, and improving efficiency. By washing, crushing, and screening waste concrete to form recycled blocks and recycled coarse aggregate, the recycled concrete includes recycled coarse aggregate, natural coarse aggregate, recycled sand, and natural fine aggregate mixed in a certain proportion; the recycled sand is formed from alluvial soil or weathered residual soil of granite after washing and drying; the energy consumption for processing recycled waste is low, requiring only processing into large-sized blocks, and the recycling rate of recycled waste is high, breaking the conventional use of waste for manufacturing recycled panels and road filling, greatly expanding the application scope of construction waste. UHPC (Recycled Block Aggregate Concrete) is a combination of industrialized construction and the recycling of construction waste, reducing on-site construction workload, lowering labor intensity, reducing noise, and reducing pollution. It aligns with national policy development directions and is an important way for the construction industry to achieve "dual carbon" goals.

[0074] This application also discloses a construction method for a UHPC-recycled block-aggregate concrete composite floor slab system, which includes the following steps:

[0075] S1. Reference Figure 1 and Figure 2 A minimal formwork and minimal support system 1 is erected, with support only provided below the joints of the UHPC precast base slab 2.

[0076] Before setting up the minimal formwork and minimal support system 1, the existing structure used to support the columns and beams should be erected first. Specifically, according to the design drawings, horizontal bars, support bars, ground bars, fasteners, steel sections, scissor braces and other components should be erected to support the column and beam formwork.

[0077] Reference Figure 4 and Figure 5 Then, the minimal formwork and minimal support system 1 is erected. According to the design drawings, the locations where supports are needed are determined, along with the installation positions and quantities of each component. Support columns 11 are then erected on the support surface, with multiple support columns 11 arranged along the length of the board joint. Since the top supports 12 are welded to the top of the support columns 11, there is no need to install them separately on-site. Then, two horizontal steel pipes 13 are horizontally erected inside the top supports 12, ensuring that both horizontal steel pipes 13 are in full contact with each top support 12. To ensure balanced stress distribution, two sets of transverse steel pipes 13 are installed at the bottom of each slab joint, with two pipes in each set. Then, multiple wooden joists 14 are erected on the transverse steel pipes 13, ensuring that each wooden joist 14 is in full contact with both sets of transverse steel pipes 13. Next, a slab joint template 15 is horizontally erected on top of the wooden joists 14, ensuring that the length direction of the slab joint template 15 is parallel to the length direction of the slab joint, and ensuring that the position of the sealing strip 16 is aligned with the position of the slab joint, so that the sealing strip 16 seals the bottom of the slab joint of the UHPC precast base slab 2.

[0078] S2. Install the UHPC precast base plate 2 on the minimal template and minimal support system 1, so that the adjacent UHPC precast base plates 2 are tightly fitted together.

[0079] Specifically, the UHPC precast base slab 2 is hoisted onto the floor using construction lifting equipment and laid smoothly on the formwork support system 1 to ensure the slab surface is level. This allows the UHPC precast base slab 2 to press down on the sealing strip 16, ensuring that the bottom of the UHPC precast base slab 2 is tightly fitted with the slab joint formwork 15 and that the top of the sealing strip 16 is in full contact with the slab joint.

[0080] S3. Tie the steel mesh 32 onto the UHPC precast base slab 2.

[0081] Reference Figure 5 and Figure 6 Specifically, the bottom chord reinforcement 322, top chord reinforcement 323, bottom slab reinforcement 324, and top slab reinforcement 325 are tied together to form a complete steel mesh 32. The web reinforcement 321 mainly bears the shear force and local bending moment in the structure. The web reinforcement 321, together with the top chord reinforcement 323 and the bottom chord reinforcement 322, form a triangular stable system. The top chord reinforcement 323 mainly bears the axial pressure and resists the pressure together with the recycled aggregate concrete 33. The bottom chord reinforcement 322 mainly bears the axial tension. The bottom slab reinforcement 324 bears the positive bending moment tension generated by the self-weight of the floor slab and the live load, while the top slab reinforcement 325 can withstand the negative bending moment tension.

[0082] S4. Place recycled concrete blocks 31 in the gaps between the steel mesh 32, pour and vibrate recycled aggregate concrete 33 to form a cast-in-place recycled mixed concrete layer 3.

[0083] Reference Figure 7 and Figure 8 Specifically, after the reinforcing mesh 32 is tied to the UHPC precast base slab 2 and before the recycled concrete blocks 31 are placed, the post-concrete placement block 23 is first placed into the placement groove 22, allowing the hollow steel pipe 24 to pass through the clearance groove 21. Then, an injection pipe 241 and an exhaust pipe 242 are installed at both ends of the hollow steel pipe 24, respectively. The injection pipe 241 is then connected to the external concrete pouring system, and concrete is poured into the hollow steel pipe 24. The air inside the hollow steel pipe 24 is discharged through the connecting hole 243 and the exhaust pipe 242, filling the inside of the hollow steel pipe 24, the connecting hole 243, and the connecting needle tube 244 with poured concrete. Then, the concrete pouring inside the hollow steel pipe 24 is stopped. It should be noted that the maximum particle size of the coarse aggregate in the concrete poured into the hollow steel pipe 24 does not exceed the inner diameter of the connecting needle tube 244, so that the concrete is less likely to clog the connecting needle tube 244.

[0084] Reference Figure 11When pouring recycled aggregate concrete 33, firstly, a first layer of recycled aggregate concrete 33 is poured on all UHPC precast base slabs 2. The thickness of the first layer of recycled aggregate concrete 33 is 40~50mm, so that the first layer of recycled aggregate concrete 33 submerges the bottom of the reinforcing mesh 32, and the first layer of recycled aggregate concrete 33 can flow into and fill the placement groove 22 and the clearance groove 21 as much as possible. Since multiple concrete pads 231 are set at the bottom of the subsequent concrete placement block 23, the first layer of recycled aggregate concrete 33 can flow smoothly into the bottom position of the subsequent concrete placement block 23, so as to reduce the phenomenon of air bubbles remaining at the bottom of the subsequent concrete placement block 23, so that the entire floor is evenly covered with a 40~50mm first layer of recycled aggregate concrete 33.

[0085] Then, the recycled concrete blocks 31 are evenly placed on the surface of the recycled aggregate concrete 33. The recycled concrete blocks 31 should be evenly placed on the entire surface of the slab and should not be scattered and piled up. The surface of the recycled concrete blocks 31 should be hard and clean, and free of mud and loose debris. Before placing the recycled concrete blocks 31, they should be sprayed with water to moisten them. The surface should be moist, but there should be no obvious water accumulation or water stains.

[0086] Reference Figure 12 Before the first layer of recycled aggregate concrete 33 initially sets, the second layer of recycled aggregate concrete 33 is poured. When pouring the second layer of recycled aggregate concrete 33, a segmented pouring method is adopted. First, the recycled concrete is poured on one side of the first layer of recycled aggregate concrete 33. Then, the mixture of recycled concrete blocks 31 and recycled aggregate concrete 33 is fully vibrated so that the area of ​​the second layer of recycled aggregate concrete 33 that is not in contact with the inner wall of the UHPC precast base slab 2 flows to a sloping state. At the same time, an immersion vibrator is used to fully vibrate the mixture of recycled concrete blocks 31 and the second layer of recycled aggregate concrete 33. During vibration, the horizontal distance between adjacent insertion points should not exceed 500mm. The vibrator should be inserted to the bottom of the first layer of recycled aggregate concrete 33 and pry the recycled concrete blocks 31 around to fully integrate the upper and lower layers of recycled aggregate concrete 33 and to fully coat the recycled concrete blocks 31 with the concrete slurry. When the vibrator vibrates the recycled aggregate concrete 33 above and around the slab joint, pressure is applied to the inside of the hollow steel pipe 24 through the external concrete pouring system and the concrete is poured slowly. This allows the concrete inside the hollow steel pipe 24 to be slowly discharged through the connecting hole 243 and the connecting needle tube 244. With the cooperation of the vibrator, the air bubbles in the recycled aggregate concrete 33 are reduced to the greatest extent, thereby increasing the structural strength of the cast-in-place recycled mixed concrete layer 3 and the bonding strength between the UHPC precast base plate 2 and the cast-in-place recycled mixed concrete layer 3.

[0087] Next, the second area is poured, and the mixture of recycled concrete blocks 31 and recycled aggregate concrete 33 in the second area is vibrated in the same way until the entire cast-in-place recycled mixed concrete layer 3 is poured. In addition, after the entire cast-in-place recycled mixed concrete layer 3 is poured, all injection pipes 241 and vent pipes 242 are removed.

[0088] It should be noted that the surface of the recycled concrete block 31 should be firm, clean, and hygienic. It can be cleaned by high-pressure water washing to ensure that there are no loose stones, dirt, dust, or other debris on the surface. The replacement rate of the recycled concrete block is 25% to 35%, that is, the mass of the recycled concrete block 31 accounts for 25% to 35% of the mass of the cast-in-place recycled mixed concrete layer 3.

[0089] The standard range for the cubic compressive strength of waste concrete blocks is C20~C50, please refer to the structural design drawings for specific details. The standard value for the cubic compressive strength of new recycled aggregate concrete 33 is... Estimated cubic compressive strength of recycled old concrete blocks The relationship between them satisfies the following equation:

[0090] ;

[0091] According to the "Technical Standard for Recycled Concrete Composite Structures" (JGJ / T 48-2019), when the difference between the standard value of the cubic compressive strength of new concrete and the estimated value of the cubic compressive strength of old concrete is less than 15 MPa, it should be calculated using the following formula:

[0092] ;

[0093] In the formula: Standard value of compressive strength of composite cube of recycled mixed concrete (N / mm²) 2 ), The standard value of the cubic compressive strength of new concrete is taken according to the provisions of the linear national standard "Code for Design of Concrete Structures" GB 50010 (N / mm²). 2 ), To estimate the cubic compressive strength of concrete (N / mm²) 2 η is the replacement rate of old concrete blocks in recycled mixed concrete.

[0094] According to the formula, if the new concrete adopts the original design strength grade, even if the strength grade of the recycled blocks is higher, the strength grade of the recycled mixed concrete is difficult to meet the requirements of the original design strength grade. Therefore, in order to ensure the strength of the recycled mixed concrete, the strength of the new recycled aggregate concrete 33 should be one grade higher than the original design strength.

[0095] The minimum characteristic dimension of the recycled concrete block 31 is generally greater than 70mm, and the maximum value must be less than the clear distance between the upper reinforcement bars 325 on the slab, and must be less than the slab thickness minus the thickness of the upper and lower protective layers, to ensure that the recycled concrete block 31 does not protrude from the slab surface.

[0096] New concrete should be pumped directly to the intended pouring location using a truck-mounted concrete pump. The pouring height of the concrete should not exceed 2m. If the pouring height exceeds the specified limit, auxiliary devices such as chutes, conveyors, or pipes should be used for pouring.

[0097] The vibrator can be inserted in a row-and-column or staggered manner, but not interchangeably to avoid missed vibrations. The vibration time at each point should be no less than 30 seconds, until the concrete surface no longer settles significantly, no more air bubbles appear, and mortar rises to the surface. During vibration, the vibrator should be inserted quickly and withdrawn slowly, with slight up-and-down movement of the vibrator to ensure uniform vibration.

[0098] For structural embedded parts (pipes), reserved holes, densely reinforced areas, and other special locations, measures must be formulated in advance, and vibration must be strengthened during construction to ensure no areas are missed. To control the elevation and flatness of the slab surface, short steel bars should be used to mark the elevation of the slab surface. After the slab concrete is vibrated and compacted, it should be leveled with a screed. After initial setting, to prevent shrinkage cracks from appearing on the slab surface, the surface should be smoothed with a trowel.

[0099] After concrete is poured, water seepage is likely to occur on the surface. Therefore, it is essential to carefully polish the concrete surface repeatedly with a wooden scrubbing board during the later stages of concrete vibration. This polishing must be done before the concrete initially sets. Use a 2m long scraper to smooth the concrete surface according to the horizontal level control marks. Any uneven areas must be repaired and leveled. Then, polish the surface again with a wooden scrubbing board. Finally, before the concrete surface dries and hardens, polish it thoroughly again with the wooden scrubbing board. Immediately afterward, cover the concrete surface for curing to extend the curing time as much as possible.

[0100] S5. Curing of the completed floor slab.

[0101] Specifically, the curing method for recycled block aggregate concrete components should comply with the provisions of the current national standard "Standard for Quality Control of Concrete" GB 50164. Water curing should begin 4 to 6 hours after pouring, with watering no less than 7 times a day and a curing time of no less than 14 days.

[0102] Within 24 hours of the completion of concrete pouring, it is strictly forbidden for people to walk on it. Within 36 hours of the completion of pouring, except for testing temperature measuring equipment and covering for insulation, it is forbidden for people to walk on it and for construction materials to be piled up.

[0103] For areas where the base slab cannot be continuously covered, such as the wall and column reinforcement sections and steel column corners, these are weak points in thermal insulation and curing. Insulation felt should be cut and filled in to ensure complete coverage as much as possible, avoiding "cold bridging" and preventing excessively rapid localized cooling in these areas. Concrete curing should be handled by designated personnel, divided into two shifts, with proper handover procedures.

[0104] The above are all preferred embodiments of this application and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A UHPC-recycled block-aggregate concrete composite floor system, characterized in that: The structure comprises from bottom to top: a few-formwork and few-support system (1); a UHPC prefabricated bottom plate (2) laid on the few-formwork and few-support system (1) and ensuring the level of the plate surface, the top of the UHPC prefabricated bottom plate (2) extending upward around and forming a pouring groove; a cast-in-place recycled mixed concrete layer (3) poured into the pouring groove of the UHPC prefabricated bottom plate (2) and closely combined therewith; The cast-in-place recycled mixed concrete layer (3) comprises: a plurality of recycled concrete blocks (31) as fillers; a steel mesh (32) for resisting tension; a recycled aggregate concrete (33) wrapping the recycled concrete blocks (31) and the steel mesh (32); The few-formwork and few-support system (1) comprises support columns (11) for transmitting loads to a support surface, top supports (12) arranged on the support columns (11), transverse steel pipes (13) arranged on the top supports (12), wooden battens (14) arranged on the transverse steel pipes (13), plate joint formworks (15) arranged on the wooden battens (14) and located at the bottom of the joints of the UHPC prefabricated bottom plate (2), and sealing rubber strips (16) arranged in transverse grooves (17) at the top of the plate joint formworks (15), the plate joint formworks (15) being arranged along the length direction of the joints, the thickness of the sealing rubber strips (16) being greater than the depth of the transverse grooves (17), and the sealing rubber strips (16) sealing the bottom of the joints of the UHPC prefabricated bottom plate (2); The UHPC prefabricated bottom plates (2) are spliced by joints between adjacent UHPC prefabricated bottom plates (2), the end of each UHPC prefabricated bottom plate (2) is provided with a plurality of interval arranged accommodation grooves (21) and placement grooves (22) near the joint, the placement grooves (22) are provided with back concrete placement blocks (23), the back concrete placement blocks (23) are connected by hollow steel pipes (24), the accommodation grooves (21) are for the hollow steel pipes (24) to pass through, and there is a gap between the wall of the placement groove (22) and the side wall of the back concrete placement block (23); The two ends of the hollow steel pipe (24) extend upward and are provided with external threads, the two ends of the hollow steel pipe (24) are connected with injection pipes (241) and exhaust pipes (242) by the external threads, the hollow steel pipe (24) is provided with a plurality of communication holes (243) along the radial direction and the circumferential direction, the diameter of the communication hole (243) gradually decreases from the inner tube wall to the outer tube wall of the hollow steel pipe (24), and the communication hole (243) is provided with a vortex groove (2431) in the form of a vortex.

2. The UHPC-recycled aggregate-concrete composite floor system according to claim 1, characterized in that: The top surface of the UHPC prefabricated bottom plate (2) is provided with a rough surface, the steel mesh (32) comprises web steel bars (321) partially embedded in the UHPC prefabricated bottom plate (2), lower chord steel bars (322) arranged at the bottom of the web steel bars (321), upper chord steel bars (323) arranged at the top of the web steel bars (321), plate lower part steel bars (324) arranged at the middle part of the web steel bars (321), and plate upper part steel bars (325) arranged at the top of the web steel bars (321).

3. The UHPC-recycled aggregate-concrete composite floor system according to claim 1, wherein: The bottom of the rear concrete placement block (23) is provided with a concrete cushion block (231) around the periphery, and a space is left between the concrete cushion block (231) and the side wall of the rear concrete placement block (23), and the outer side of the hollow steel pipe (24) is provided with a communication needle pipe (244) in communication with the communication hole (243), and the communication needle pipe (244) is located in the rear concrete placement block (23) and its end penetrates the outer side of the rear concrete placement block (23).

4. The UHPC-recycled aggregate-concrete composite floor system according to claim 1, wherein: The bottom of the recycled concrete block (31) is provided with a foot pad around the periphery, and the foot pad is provided with a space for the side wall of the recycled concrete block (31).

5. The construction method of a UHPC-recycled block-aggregate concrete composite floor system according to any one of claims 1 to 4, characterized in that, The construction method comprises the following steps: S1. erecting a few formwork and a few support system (1), and supporting only under the plate joint of the UHPC prefabricated bottom plate (2); S2. installing the UHPC prefabricated bottom plate (2) on the few formwork and a few support system (1), so that the adjacent UHPC prefabricated bottom plates (2) are tightly fitted; S3. binding the steel bar net (32) on the UHPC prefabricated bottom plate (2); S4. placing the recycled concrete block (31) in the space between the steel bar net (32), pouring and vibrating the recycled aggregate concrete (33) to form the cast-in-place recycled mixed concrete layer (3); S5. curing the completed floor slab.

6. The construction method of a UHPC-recycled block-aggregate concrete composite floor system according to claim 5, characterized in that: In step S4, after the UHPC prefabricated bottom plate (2) is installed, the rear concrete placement block (23) is placed into the placement groove (22), the hollow steel pipe (24) penetrates the accommodation groove (21), then the injection pipe (241) and the exhaust pipe (242) are respectively installed at both ends of the hollow steel pipe (24), then the injection pipe (241) is connected with the external concrete pouring system, and the hollow steel pipe (24) is poured with concrete, the air in the hollow steel pipe (24) is exhausted through the communication hole (243) and the exhaust pipe (242), and the hollow steel pipe (24) and the communication hole (243) are filled with the poured concrete, then the pouring of the concrete in the hollow steel pipe (24) is stopped.

7. The construction method of a UHPC-recycled aggregate-concrete composite floor system according to claim 5, characterized in that: In step S5, when pouring the recycled aggregate concrete (33), first, a first layer of recycled aggregate concrete (33) is poured on all the UHPC prefabricated bottom plates (2), so that the first layer of poured recycled aggregate concrete (33) submerges the bottom of the steel mesh (32), then the recycled concrete blocks (31) are uniformly placed, and before the first layer of recycled aggregate concrete (33) is initially cured, a second layer of recycled aggregate concrete (33) is poured; when pouring the second layer of recycled aggregate concrete (33), the pouring is performed in a regional manner, the recycled aggregate concrete (33) is first poured on one side of the first layer of recycled aggregate concrete (33), then the mixture of the recycled concrete blocks (31) and the recycled aggregate concrete (33) is fully vibrated, so that the area of the second layer of recycled aggregate concrete (33) not in contact with the inner side wall of the UHPC prefabricated bottom plate (2) flows to a sloping state, then the second region is poured, and the mixture of the recycled concrete blocks (31) and the recycled aggregate concrete (33) in the second region is vibrated in the same manner, until the pouring of the entire cast-in-place recycled hybrid concrete layer (3) is completed.

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