Filled steel pipe column using waste concrete crushed recycled aggregate

Abstract

The invention discloses a filled steel pipe column using waste concrete crushed recycled aggregate, and belongs to the field of green building and structural engineering. The steel pipe column comprises an outer steel pipe and an inner steel pipe which are coaxially arranged, an annular cavity is formed between the outer steel pipe and the inner steel pipe, and the cavity is filled with recycled aggregate concrete formed by mixing recycled coarse aggregate obtained by crushing and screening cement, water, natural fine aggregate and waste concrete; positioning assemblies are arranged at the two ends of the inner steel pipe, and accurate coaxial installation with the outer steel pipe is achieved through threaded sleeves, limiting rods and torsion nuts; two ends are sealed by annular end covers with internal and external thread grooves; the inner wall of the outer steel pipe is coated with an epoxy resin interface agent layer subjected to sand blasting or acid etching treatment, and annular protruding ribs are arranged on the outer wall of the inner steel pipe in a staggered mode in the axial direction. The mechanical property and durability of the recycled aggregate concrete are effectively improved, high-value utilization of building waste is achieved, and meanwhile the overall stability, bearing capacity and construction feasibility of the concrete filled steel tubular column are improved.

Description

Technical Field

[0001] This invention belongs to the field of green building and structural engineering, and in particular relates to a filled steel pipe column using recycled aggregate from crushed waste concrete. Background Technology

[0002] Construction waste, with waste concrete accounting for over 70%, is primarily disposed of through landfill or simple stockpiling. This not only occupies valuable land resources but also easily causes environmental pollution and wastes the renewable aggregate resources it contains. Against this backdrop, processing waste concrete into recycled aggregate through crushing, screening, and strengthening processes, and then using it in concrete production, has become an important technological path to achieve green construction. However, recycled aggregates have inherent defects such as adhered old mortar, high porosity, high water absorption, and high crushing index, leading to problems in recycled concrete with lower strength, reduced elastic modulus, and weak interfacial transition zones, thus limiting its widespread application in load-bearing structures.

[0003] To improve the mechanical properties and durability of recycled concrete, researchers have attempted to combine it with steel tubes to form concrete-in-steel tube structures, utilizing the confinement effect of the steel tubes on the core concrete to improve its stress state. However, existing concrete-in-steel tube columns mostly use a single layer of steel tubes filled with ordinary or recycled concrete. Under high axial compression or seismic loading, they are prone to problems such as local buckling of the steel tubes, concrete cracking and spalling, and interface slippage, especially when using recycled aggregates, these defects are more pronounced. In addition, traditional filling methods cannot guarantee the compactness and uniformity of recycled concrete within a narrow annular space, and there is a lack of effective internal tube positioning and interface reinforcement measures, affecting the overall collaborative performance.

[0004] Therefore, there is an urgent need for a novel composite column structure that can efficiently utilize recycled aggregate from waste concrete while significantly improving structural load-bearing capacity and ductility, in order to meet the pressing demands of modern engineering for high-performance, sustainable structural systems. Against this backdrop, this invention addresses the shortcomings of existing technologies by proposing an innovative structure of double-steel-tube sandwiched recycled aggregate concrete, aiming to achieve the dual goals of resource recycling and structural performance enhancement. Summary of the Invention

[0005] The purpose of this invention is to provide a steel pipe column filled with recycled aggregate from crushed waste concrete. By setting up a coaxial double steel pipe structure and filling its annular cavity with recycled aggregate concrete prepared from recycled coarse aggregate obtained from crushed and screened waste concrete, combined with adjustable positioning components, epoxy resin interface reinforcement layer, staggered annular ribs and threaded sealing end caps, etc., this invention solves the problems of low mechanical properties of existing recycled aggregate concrete, easy interface slippage and local buckling of steel pipe concrete columns, limited application of recycled materials in load-bearing structures, and low resource utilization rate of construction waste.

[0006] To solve the above-mentioned technical problems, the present invention is achieved through the following technical solution: This invention relates to a steel pipe column filled with recycled aggregate from crushed waste concrete, comprising an outer steel pipe and an inner steel pipe coaxially arranged, forming an annular cavity between the outer and inner steel pipes, the annular cavity being filled with recycled aggregate concrete; characterized in that: positioning components are installed at both ends of the inner steel pipe, the inner steel pipe is coaxially installed inside the outer steel pipe through the positioning components, and annular end caps are installed at both ends of the inner and outer steel pipes, the annular end caps covering the opening end of the annular cavity; The positioning component includes a threaded sleeve. One end of the threaded sleeve is installed with the outer lug of the inner end cover via a pin. The other end of the threaded sleeve is fitted with a limit rod through an internal thread. A torsion nut is fixed in the middle of the limit rod, and the end of the limit rod matches a limit hole opened on the inner wall of the outer steel pipe end. The recycled aggregate concrete is made by mixing cement, water, natural fine aggregate, and recycled coarse aggregate obtained by crushing and screening waste concrete.

[0007] The present invention is further configured such that both the outer steel pipe and the inner steel pipe are circular cross-section steel pipes, and the outer diameter of the inner steel pipe is smaller than the inner diameter of the outer steel pipe.

[0008] The invention is further configured such that a concrete pouring hole is provided on the end side wall of the outer steel pipe, and the concrete pouring hole communicates with the interior of the annular cavity.

[0009] The present invention is further configured such that the maximum particle size of the recycled coarse aggregate in the recycled aggregate concrete does not exceed 20 mm, and the crushing index is not greater than 25%.

[0010] The present invention is further configured such that the inner wall of the outer steel pipe is coated with an epoxy resin interface agent layer, and the surface of the epoxy resin interface agent layer is formed by sandblasting or acid etching to form a micro-rough surface.

[0011] The present invention is further configured such that the recycled aggregate concrete is injected into the annular cavity through a concrete pouring hole, and after being vibrated and compacted, it fills the entire annular cavity after hardening.

[0012] The present invention is further configured such that both the outer and inner rings of the annular end cap are provided with threaded grooves, and the threaded grooves are respectively connected to the outer ring threads of the outer steel pipe and the inner steel pipe.

[0013] The present invention is further configured such that the inner wall of the outer steel pipe and the outer wall of the inner steel pipe are provided with a plurality of annular ribs at axial intervals, and the plurality of annular ribs arranged in a staggered manner form the flow path of the recycled aggregate concrete.

[0014] The present invention has the following beneficial effects: 1. This invention uses an outer steel pipe and an inner steel pipe arranged coaxially to form a double-layer constraint system. The recycled aggregate concrete is tightly wrapped in an annular cavity and is under triaxial compression under axial load, which improves its compressive strength, ductility and durability, and overcomes the problem of insufficient mechanical properties caused by weak interface and high porosity of traditional recycled concrete.

[0015] 2. This invention ensures precise coaxial positioning of the inner steel pipe throughout the entire process of pouring and use by setting adjustable positioning components and threaded annular end caps at the ends of the inner and outer steel pipes, preventing eccentric stress, achieving reliable sealing of the annular cavity, avoiding grout leakage, and improving construction quality and efficiency.

[0016] 3. The annular ribs arranged axially on the inner and outer steel pipe walls of the present invention not only guide the uniform flow of concrete and facilitate dense pouring, but also form mechanical interlocking "keyways" after hardening, which significantly enhances the shear and slip resistance of the composite interface and improves the overall collaborative performance.

[0017] 4. This invention uses waste concrete from construction waste as recycled coarse aggregate to prepare recycled aggregate concrete in the annular cavity after crushing and screening. This effectively realizes the resource utilization of construction waste, greatly reduces the mining of natural sand and gravel and the land occupied by landfill, and is in line with the concept of environmental protection.

[0018] Of course, any product implementing this invention does not necessarily need to achieve all of the advantages described above at the same time. Attached Figure Description

[0019] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below.

[0020] Figure 1 A schematic diagram of the overall structure of a steel pipe column filled with recycled aggregate from crushed waste concrete.

[0021] Figure 2 This is a schematic diagram of the interior of a steel pipe column filled with recycled aggregate from crushed waste concrete.

[0022] Figure 3 A schematic diagram showing the coaxial arrangement of the outer and inner steel pipes of a steel pipe column filled with recycled aggregate from crushed waste concrete.

[0023] Figure 4 A side view of a steel pipe column filled with recycled aggregate from crushed waste concrete.

[0024] Figure 5 A schematic diagram showing the location of the annular ribs in a steel pipe column filled with recycled aggregate from crushed waste concrete.

[0025] The following is a list of components represented by each label in the attached diagram: 1. Outer steel pipe; 11. Concrete pouring hole; 2. Inner steel pipe; 3. Recycled aggregate concrete; 4. Positioning component; 41. Threaded sleeve; 42. Limiting rod; 43. Torsion nut; 5. Annular end cap; 6. Annular rib. Detailed Implementation

[0026] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention.

[0027] Example Please see Figure 1-5 This invention relates to a steel pipe column filled with recycled aggregate from crushed waste concrete, comprising an outer steel pipe 1 and an inner steel pipe 2 arranged coaxially, forming an annular cavity between the outer steel pipe 1 and the inner steel pipe 2, the annular cavity being filled with recycled aggregate concrete 3; by setting up a constraint system with double-layer steel pipes, the outer steel pipe 1 provides overall bending and compressive bearing capacity, while the inner steel pipe 2 participates in bearing under compression, and a composite force mechanism is achieved through the recycled aggregate concrete 3 in the annular cavity; the recycled aggregate concrete 3 is under triaxial compression under the constraint of the double steel pipes, significantly improving its compressive strength and ductility, while effectively utilizing construction waste; The inner steel pipe 2 is equipped with positioning components 4 at both ends. The inner steel pipe 2 is coaxially installed inside the outer steel pipe 1 through the positioning components 4. The inner steel pipe 2 and the outer steel pipe 1 are equipped with annular end caps 5 at both ends. The annular end caps 5 cover the opening end of the annular cavity. This ensures that the inner steel pipe 2 remains coaxial with the outer steel pipe 1 during the casting and service process, avoiding local instability or stress concentration caused by eccentric force. The annular end caps 5 not only seal the annular cavity to prevent concrete leakage, but also serve as an axial force transmission interface, uniformly transferring the load to the inner and outer steel pipes 1 and the core concrete, thereby improving the overall collaborative performance. The positioning component 4 includes a threaded sleeve 41. One end of the threaded sleeve 41 is installed with an outer lug of the inner end cap via a pin. The other end of the threaded sleeve 41 is internally threaded to install a limiting rod 42. A torsion nut 43 is fixed in the middle of the limiting rod 42, and the end of the limiting rod 42 matches a limiting hole opened on the inner wall of the outer steel pipe 1. By rotating the torsion nut 43, the limiting rod 42 is driven to move axially along the threaded sleeve 41, so that its end is precisely embedded in the limiting hole on the inner wall of the outer steel pipe 1, thereby achieving precise positioning of the inner steel pipe 2 in the radial and circumferential directions. This structure facilitates on-site assembly and disassembly, is suitable for rapid installation of prefabricated components, and ensures that the concentricity is controlled within the allowable error range of the project. The recycled aggregate concrete 3 is made by mixing cement, water, natural fine aggregate and recycled coarse aggregate obtained by crushing and screening waste concrete. Replacing part or all of the natural coarse aggregate with recycled coarse aggregate reduces the dependence on natural sand and gravel resources on the one hand, and ensures the mechanical properties of concrete through reasonable mix proportions on the other hand. The recycled aggregate retains a certain degree of angularity after crushing and screening, which helps to improve the mechanical bonding force with cement paste.

[0028] Specifically, the outer steel pipe 1 has a concrete pouring hole 11 on its end side wall, which is connected to the interior of the annular cavity. The recycled aggregate concrete 3 is injected into the annular cavity through the concrete pouring hole 11, and after being vibrated and compacted, it fills the entire annular cavity after hardening. The maximum particle size of the recycled coarse aggregate in the recycled aggregate concrete 3 does not exceed 20mm, which can ensure that the recycled aggregate can pass smoothly through the narrow annular cavity and avoid blockage. The crushing index is not greater than 25%, which ensures that the recycled aggregate has sufficient strength and durability and prevents premature crushing under load, which would lead to deterioration of concrete performance.

[0029] Furthermore, both the outer steel pipe 1 and the inner steel pipe 2 are circular cross-section steel pipes, with the outer diameter of the inner steel pipe 2 being smaller than the inner diameter of the outer steel pipe 1. The inner wall of the outer steel pipe 1 is coated with an epoxy resin interface agent layer, and the surface of the epoxy resin interface agent layer is sandblasted or acid-etched to form a micro-rough surface. The epoxy resin layer isolates the risk of electrochemical corrosion between the steel pipe and the concrete, while its micro-rough surface significantly enhances the bonding force with the recycled aggregate concrete 3, compensates for the weak interface of the recycled aggregate, and improves the integrity and load transfer efficiency of the composite structure. Both the outer and inner rings of the annular end cap 5 are provided with threaded grooves, which are respectively connected to the outer ring threads of the outer steel pipe 1 and the inner steel pipe 2; to achieve reliable sealing and mechanical locking between the annular end cap 5 and the inner and outer steel pipes 1, to prevent grout leakage during concrete pouring, and at the same time to resist the separation force generated by the expansion of the internal concrete during the service stage, to ensure the continuity of end restraint, and to improve the shear and pull-out resistance of the column end. The inner wall of the outer steel pipe 1 and the outer wall of the inner steel pipe 2 are provided with several annular ribs 6 interlaced along the axial direction. The multiple interlaced annular ribs 6 form the flow path of the recycled aggregate concrete 3. On the one hand, it increases the mechanical interlocking between the steel pipe and the concrete and improves the interface anti-slip ability. On the other hand, the gap between the ribs forms a spiral or zigzag flow channel, which guides the recycled aggregate concrete 3 to be evenly distributed during the pouring process, reduces air bubble retention, and forms a "keyway effect" after hardening, which significantly enhances the synergistic working ability and shear resistance of the composite section.

[0030] The operation process of this embodiment is as follows: First, the outer steel pipe 1 and the inner steel pipe 2 are prefabricated in the factory or at the construction site, ensuring that both are circular cross-sections and their dimensions match. The outer diameter of the inner steel pipe 2 is smaller than the inner diameter of the outer steel pipe 1 to reserve space for forming an annular cavity. Then, the inner wall of the outer steel pipe 1 is sandblasted or acid-etched, and a layer of epoxy resin interface agent is uniformly coated on its surface to form a bonding reinforcement layer with a micro-rough structure to improve the interface performance with the subsequent filling concrete. Next, positioning components 4 are installed at both ends of the inner steel pipe 2. One end of the threaded sleeve 41 is hinged to the lug on the outside of the inner end cap by a pin, and the other end is screwed into the limiting rod 42 with a torsion nut 43. The inner steel pipe 2 with the positioning components 4 assembled is carefully placed into the inner steel pipe 1. The extension length of the limiting rod 42 is adjusted by rotating the torsion nut 43 so that its end is accurately embedded in the limiting hole pre-opened on the inner wall of the end of the outer steel pipe 1, thereby achieving coaxial and precise positioning of the inner and outer steel pipes 1. Subsequently Annular end caps 5 are screwed onto both ends of the outer steel pipe 1 and the inner steel pipe 2. The inner and outer rings of the end caps have matching threaded grooves, which can be tightly connected to the external threads of the outer steel pipe 1 and the inner steel pipe 2 respectively, thus completing the sealing of the annular cavity. Then, the pre-mixed recycled aggregate concrete 3 is pumped or injected into the annular cavity by its own weight through the concrete pouring hole 11 opened on the side wall of the end of the outer steel pipe 1. During this process, the concrete pouring hole 11 also serves as a venting structure. During the pouring process, external vibration or immersion vibration equipment is used to ensure that the recycled aggregate concrete 3 is fully compacted and completely fills the flow path formed by the inner and outer steel pipes 1 and the staggered annular ribs 6, avoiding voids or segregation. After the concrete pouring is completed, the concrete pouring hole 11 is sealed and the component is cured to the design strength. Finally, the hardened filled steel pipe column is transported to the construction site, hoisted, aligned and connected to the nodes according to the structural design requirements, and put into use as a vertical load-bearing component.

[0031] In the description of this specification, references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

Claims

1. A steel pipe column filled with recycled aggregate from crushed waste concrete, comprising an outer steel pipe (1) and an inner steel pipe (2) coaxially arranged, wherein an annular cavity is formed between the outer steel pipe (1) and the inner steel pipe (2), and the annular cavity is filled with recycled aggregate concrete (3); characterized in that: The inner steel pipe (2) is equipped with positioning components (4) at both ends. The inner steel pipe (2) is coaxially installed inside the outer steel pipe (1) through the positioning components (4). The inner steel pipe (2) and the outer steel pipe (1) are equipped with annular end caps (5) at both ends. The annular end caps (5) cover the opening end of the annular cavity. The positioning component (4) includes a threaded sleeve (41). One end of the threaded sleeve (41) is installed with the outer lug of the inner end cover via a pin. The other end of the threaded sleeve (41) is fitted with a limit rod (42) through an internal thread. A torsion nut (43) is fixed in the middle of the limit rod (42), and the end of the limit rod (42) matches the limit hole opened on the inner wall of the outer steel pipe (1). The recycled aggregate concrete (3) is made by mixing cement, water, natural fine aggregate and recycled coarse aggregate obtained by crushing and screening waste concrete.

2. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, Both the outer steel pipe (1) and the inner steel pipe (2) are circular cross-section steel pipes, and the outer diameter of the inner steel pipe (2) is smaller than the inner diameter of the outer steel pipe (1).

3. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, The end side wall of the outer steel pipe (1) is provided with a concrete pouring hole (11), which is connected to the interior of the annular cavity.

4. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, The maximum particle size of the recycled coarse aggregate in the recycled aggregate concrete (3) is no more than 20 mm, and the crushing index is no more than 25%.

5. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, The inner wall of the outer steel pipe (1) is coated with an epoxy resin interface agent layer, and the surface of the epoxy resin interface agent layer is sandblasted or acid-etched to form a micro-rough surface.

6. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 3, characterized in that, The recycled aggregate concrete (3) is injected into the annular cavity through the concrete pouring hole (11), and after being vibrated and compacted, it fills the entire annular cavity after hardening.

7. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, The outer and inner rings of the annular end cap (5) are provided with threaded grooves, which are respectively connected to the outer ring threads of the outer steel pipe (1) and the inner steel pipe (2).

8. The steel pipe column filled with recycled aggregate from crushed waste concrete according to claim 1, characterized in that, The inner wall of the outer steel pipe (1) and the outer wall of the inner steel pipe (2) are provided with several annular ribs (6) at intervals along the axial direction. The multiple annular ribs (6) formed by the multiple interleaved annular ribs (6) form the flow path of the recycled aggregate concrete (3).

Images