PRECAST CONCRETE COLUMN WITH EMBEDDED RECYCLED COMPONENT AND CONSTRUCTION METHOD THEREFOR

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of International Application of PCT application serial no. PCT/CN2025/076410 filed on Feb. 8, 2025, which claims the priority benefit of China application serial no. 202410315212.2 filed on Mar. 19, 2024. The entirety of each of the above-mentioned patent applications is hereby incorporated by reference herein and made a part of this specification.

BACKGROUND

Technical Field

The present invention relates to the technical field of waste concrete recycling, and in particular to a precast concrete column with an embedded recycled component and a construction method therefor.

Description of Related Art

With the rapid development of urban construction and the orderly advancement of urban renewal in China, how to implement green and efficient reuse of demolished old concrete components has become an increasingly prominent focus of public attention. A current common practice is to crush old concrete in old concrete components into small-scale recycled aggregate or demolished concrete lumps, and then add cement and other binders to prepare recycled aggregate concrete or mix the demolished concrete lumps with fresh concrete to form recycled lump concrete. However, the crushing process is not only relatively complicated, but also generates a large amount of energy consumption and powder that is not easily utilized, which significantly reduces a recycling rate of the old concrete. In addition, preparing the recycled aggregate concrete consumes a large amount of cement, a proportion of fresh concrete in the recycled lump concrete is as high as approximately 70%, and producing the fresh concrete also consumes a large amount of cement. Because cement production generates a large amount of CO₂, the carbon emission reduction effect of the above existing practice still needs to be further improved. In addition, old steel bars recovered from the old concrete components during the crushing process also need to undergo complicated processes such as smelting before being reused as a resource. These complicated processes also consume a large amount of energy and emit a large amount of CO₂, causing an insignificant carbon emission reduction effect. In summary, a strategy for recycling and reusing the old concrete components still needs to be further improved. Therefore, if the old concrete components can be directly used in the production of new components without being crushed, the above problems will undoubtedly be greatly alleviated. However, there is currently no precedent for simply, efficiently, and directly utilizing the old concrete components in the production of the new components.

Precast concrete components feature a fast construction speed, a high degree of industrialization, and low environmental pollution, which are widely used in engineering construction. Columns are important vertical load-bearing components in building structures. During production of the precast concrete columns, if recycled components obtained by simple treatment of the old concrete components can be directly cast inside new precast concrete columns, this is undoubtedly an effective way to directly utilize the old concrete components.

SUMMARY

At present, the existing technology cannot implement the recycling and reusing of old beam-type components and old column-type components at a component level. The present invention provides a precast concrete column with an embedded recycled component and a construction method therefor, and proposes for the first time an effective solution for recycling and reusing the old beam-type components and old column-type components as a whole within the precast concrete column, which has a significant carbon emission reduction effect.

To achieve the purpose of the present invention, the precast concrete column with an embedded recycled component provided in the present invention includes recycled components, column longitudinal steel bars, spiral stirrups, ordinary or composite stirrups, first connectors, second connectors, fresh concrete, and grouting sleeves.

The recycled component is enclosed within the fresh concrete, and the recycled component includes an old stirrup, an old longitudinal steel bar, and old concrete. The height and cross-sectional width of the recycled component are respectively less than the height and cross-sectional width of the precast concrete column, and the volume of the recycled component is not less than 40% of the volume of the precast concrete column;

• • the column longitudinal steel bar is located within the fresh concrete;
  • the grouting sleeve is located below the recycled component;
  • an arranging range of the ordinary or composite stirrup is an area where the grouting sleeve is located;
  • an arranging range of the spiral stirrup is an area where the grouting sleeve is not located;
  • the first connector is made of a steel bar and is configured to connect the old stirrup and the column longitudinal steel bar, and an arranging range of the first connector is an area where the recycled component is located;
  • the second connector is made of a steel bar and is configured to connect the old longitudinal steel bar and the column longitudinal steel bar; an arranging range of the second connector is an upper longitudinal range of 0-500 mm and a lower longitudinal range of 0-500 mm within an area where the recycled component is located;
  • apart from the interior of the grouting sleeve, the fresh concrete is cast around the grouting sleeve, and above, below, and around the recycled component, and the fresh concrete is natural aggregate concrete with a maximum coarse aggregate particle size not greater than 20 mm or recycled aggregate concrete with a maximum coarse aggregate particle size not greater than 20 mm, or recycled aggregate concrete containing recycled sand from excavated soil from construction sites.

Further, a net distance between a lower surface of the recycled component and the grouting sleeve is 50-100 mm.

Further, a cross-sectional width of the recycled component is at least 150 mm less than a cross-sectional width of the precast concrete column.

Further, the recycled component is obtained by removing a stirrup protective layer from and performing surface roughening treatment on an old concrete component dismantled from an old buildings or other old structures.

Further, the compressive strength of the fresh concrete is not less than the compressive strength of the old concrete in the recycled component.

Further, the first connector clasps the column longitudinal steel bar from an outer side of the column longitudinal steel bar, and the first connector is welded to the old stirrup.

Further, a yield strength of the steel bar of the first connector is not less than a yield strength of the old stirrup.

Further, the second connector is welded to the old longitudinal steel bar and the column longitudinal steel bar separately.

Further, a yield strength of the steel bar for the second connector is not less than a smaller value of a yield strength of the old longitudinal steel bar and a yield strength of the column longitudinal steel bar.

A construction method for the precast concrete column with the embedded recycled component is provided, including the following steps:

• • step (1), processing and fabricating column longitudinal steel bars, spiral stirrups, ordinary or composite stirrups, first connectors, and second connectors;
  • step (2), removing a stirrup protective layer from an old concrete component and performing surface roughening treatment the old concrete component to obtain a recycled component, and locally treating a part on the recycled component where the second connector is to be arranged, such that a welding surface of an old longitudinal steel bar at the part is exposed;
  • step (3), arranging column longitudinal steel bars and grouting sleeves, binding the spiral stirrups to the column longitudinal steel bars, and binding the ordinary or composite stirrups to the grouting sleeves to form a steel bar cage;
  • step (4), adjusting the steel bar cage fabricated in step (3) to a vertical state, and hoisting the recycled components from the top downwardly into an interior of the steel bar cage;
  • step (5), clasping the column longitudinal steel bar by the first connector from an outer side of the column longitudinal steel bar, welding the first connector to an adjacent old stirrup, and welding the second connector to an adjacent column longitudinal steel bar and old longitudinal steel bar;
  • step (6), completing formwork fabrication and horizontal formwork support for the precast concrete column with an embedded recycled component, hoisting the steel bar cage and recycled components constructed in step (4) and step (5) as a whole into a cavity enclosed by a formwork in a horizontal manner, and completing the detailed positioning;
  • step (7), casting sufficient fresh concrete into the cavity enclosed by the formwork, and performing vibration thoroughly and curing.

Compared with the prior art, the present invention has the following advantages and effects:

• • (1) Old beam-type and column-type components are directly utilized in the present invention, rather than being crushed into demolished concrete lumps or aggregates for reuse, which greatly simplifies the processing procedure, significantly improves the recycling rate of old concrete, and markedly reduces the consumption of fresh concrete and corresponding new cement, providing remarkable carbon emission reduction effect.
  • (2) The present invention provides the first connectors to connect the old stirrups in the recycled components with the column longitudinal steel bars in the precast concrete column, enabling the old stirrups to provide additional lateral restraint to the column longitudinal steel bar, ingeniously leveraging a unique confinement function of the old stirrups in the precast concrete column, thereby properly reducing the quantity of spiral stirrups used in the precast concrete column and achieving significant economic benefits.
  • (3) The present invention provides the second connectors to connect the old longitudinal steel bars in the recycled components with the column longitudinal steel bars in the precast concrete column, enabling the old longitudinal steel bars and the column longitudinal steel bars to work together to resist a load. To some extent, this allows the old longitudinal steel bars to play a role in longitudinal tension under seismic action or large eccentric compression, thereby properly reducing the quantity of column longitudinal steel bars in the precast concrete column and achieving significant economic benefits.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of an overall structure of a precast concrete column with an embedded recycled component according to an embodiment of the present invention;

FIG. 2 is a schematic diagram of a local structure of the recycled component in the precast concrete column with an embedded recycled component according to an embodiment of the present invention;

FIG. 3 is a schematic diagram of a positional relationship among the recycled component, a column longitudinal steel bar, and a spiral stirrup in the precast concrete column with an embedded recycled component according to an embodiment of the present invention;

FIG. 4 is a schematic diagram of a specific structure of a first connector and a second connector in the precast concrete column with an embedded recycled component according to an embodiment of the present invention;

FIG. 5 is a schematic diagram of local connection positions of the first connector and the second connector in the precast concrete column with an embedded recycled component according to an embodiment of the present invention.

DESCRIPTION OF THE EMBODIMENTS

The following provides a more detailed description of the present invention in conjunction with embodiments and accompanying drawings. However, the implementation of the present invention is not limited thereto. It should be noted that any process not specifically described in detail below can be implemented by those skilled in the art with reference to the prior art.

As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, and FIG. 5, a precast concrete column with an embedded recycled component provided in the present invention includes recycled components 1, column longitudinal steel bars 2, spiral stirrups 3, ordinary or composite stirrups 4, first connectors 5, second connectors 6, fresh concrete 7, and grouting sleeves 8.

The recycled component 1 includes an old stirrup 9, an old longitudinal steel bar 10, and old concrete 11. The old longitudinal steel bar 10 is located inside the old concrete 11, the old stirrup 9 is located outside the old longitudinal steel bar 10, and an outermost side of the old stirrup 9 is substantially flush with an outer surface of the old concrete 11. The height and cross-sectional width of the recycled component 1 are respectively less than the height and cross-sectional width of the precast concrete column. The volume of the recycled component 1 is not less than 40% of the volume of the precast concrete column.

The grouting sleeve 8 is disposed below the recycled component 1, with a distance reserved between grouting sleeve 8 and the recycled component 1. A net distance between a lower surface of the recycled component 1 and the grouting sleeve 8 is 50-100 mm. An arranging range of the ordinary or composite stirrup 4 is an area where the grouting sleeve 8 is located. An arranging range of the spiral stirrup 3 is an area where the grouting sleeve 8 is not located.

The grouting sleeve 8 is a connector configured to connect the precast concrete column and a frame node or column at a lower end of the precast concrete column. A longitudinal steel bar of the frame node or column at the lower end is inserted into the grouting sleeve during construction, and then grout is poured into the sleeve to achieve the connection.

The recycled component 1 is enclosed within the fresh concrete 7, and the column longitudinal steel bar 2 is disposed longitudinally in the fresh concrete 7. The first connector 5 is made of a steel bar and is configured to connect the old stirrup 9 and the column longitudinal steel bar 2. An arranging range of the first connector 5 is an area where the recycled component 1 is located. Specifically, the first connector 5 is clasps the column longitudinal steel bar 2 from an outer side of the column longitudinal steel bar 2, and the first connector 5 is welded to the old stirrup 9. The second connector 6 is made of a steel bar and is configured to connect the old longitudinal steel bar 10 and the column longitudinal steel bar 2. An arranging range of the second connector 6 is an upper longitudinal range of 0-500 mm and a lower longitudinal range of 0-500 mm within an area where the recycled component 1 is located. When seismic action or large eccentric compression is considered, a bending moment within a range at upper and lower ends of the recycled component 1 is the largest. Therefore, the second connector 6 disposed within a specific range at both ends allows the old longitudinal steel bar 10 and the column longitudinal steel bar 2 to work together to resist a load, thereby enabling the old longitudinal steel bar 10 to play a role in longitudinal tension. Specifically, the second connector 6 is welded to the old longitudinal steel bar 10 and the column longitudinal steel bar 2 separately. In an embodiment, the shape of the first connector 5 is , and the shape of the second connector 6 is .

The fresh concrete 7 is natural aggregate concrete or recycled aggregate concrete with a maximum coarse aggregate particle size not greater than 20 mm, or recycled aggregate concrete containing recycled sand from excavated soil from construction sites. Apart from the interior of the grouting sleeve 8, the fresh concrete 7 is cast above, below, and around the recycled component 1, and fresh concrete is also cast around the grouting sleeve 8.

In some embodiments of the present invention, the recycled component 1 is obtained by removing a stirrup protective layer from and performing surface roughening treatment on an old concrete component dismantled from an old buildings or other old structures.

In some embodiments of the present invention, the height of the precast concrete column is 3,000 mm, the cross-sectional width is 600 mm, and the thickness of a stirrup protective layer is 25 mm.

In some embodiments of the present invention, the compressive strength of the fresh concrete 7 is 60 MPa, and the compressive strength of the old concrete 11 in the recycled component 1 is 50 MPa.

In some embodiments of the present invention, the column longitudinal steel bar 2 is an HRB400 hot-rolled steel bar with a diameter of 20 mm; the spiral stirrup 3 is an HRB400 hot-rolled steel bar with a diameter of 10 mm; the ordinary or composite stirrup 4 is an HRB400 hot-rolled steel bar with a diameter of 10 mm; the old stirrup 9 is an HRB400 hot-rolled steel bar with a diameter of 10 mm; and the old longitudinal steel bar 10 is an HRB400 hot-rolled steel bar with a diameter of 20 mm.

In some embodiments of the present invention, both the first connector 5 and the second connector 6 are HRB400 hot-rolled steel bars with a diameter of 6 mm.

A construction method for the precast concrete column with an embedded recycled component as described above includes the following steps:

• • step (1), processing and fabricating column longitudinal steel bars 2, spiral stirrups 3, ordinary or composite stirrups 4, first connectors 5, and second connectors 6;
  • step (2), removing a stirrup protective layer of an old concrete component and performing surface roughening treatment to obtain a recycled component 1, and locally treating a part on the recycled component 1 where the second connector 6 to be arranged, such that a welding surface of an old longitudinal steel bar 10 at the part is exposed;
  • step (3), arranging column longitudinal steel bars 2 and grouting sleeves 8, binding the spiral stirrups 3 to the column longitudinal steel bars 2, and binding the ordinary or composite stirrups 4 to the grouting sleeves 8 to form a steel bar cage;
  • step (4), adjusting the steel bar cage fabricated in step (3) to a vertical state, and hoisting the recycled components 1 from the top downwardly into an interior of the steel bar cage;
  • step (5), clasping the column longitudinal steel bar 2 by the first connector 5 from the outer side of the column longitudinal steel bar 2, welding the first connector 5 to an adjacent old stirrup 9, and welding the second connector 6 to an adjacent column longitudinal steel bar 2 and old longitudinal steel bar 10;
  • step (6), completing formwork fabrication and horizontal formwork support for the precast concrete column with an embedded recycled component, hoisting the steel bar cage and recycled components 1 constructed in step (4) and step (5) as a whole into a cavity enclosed by a formwork in a horizontal manner, and completing detailed positioning;
  • step (7), casting sufficient fresh concrete 7 into the cavity enclosed by the formwork, and performing vibration thoroughly and curing.

As a conventional practice, the old concrete component is first crushed, a steel bar inside the old concrete component is extracted, and then large crushed concrete blocks are directly utilized as demolished concrete lumps, or the large crushed concrete blocks are crushed for a plurality of times, and the large concrete blocks are refined into recycled aggregate for reuse. When recycled lump concrete are produced using demolished concrete lumps or recycled aggregate concrete is produced using recycled aggregate, a cementitious material such as a large amount of new cement is required, and cement production not only consumes a great deal of energy but also generates a large amount of carbon emission. During crushing for a plurality of times, it is inevitable that a large amount of powder that is not easily utilized is generated, which significantly reduces a recycling rate of old concrete. In addition, the old steel bars extracted during the crushing process of old concrete components also need to undergo complicated processes such as smelting before being reused as a resource. These complicated processes also consume a large amount of energy and emit a large amount of CO₂, causing an insignificant carbon reduction effect.

To solve the above problems, the present invention proposes for the first time a concept of directly recycling old beam-type components and old column-type components at a component level, instead of crushing the concrete into demolished concrete lumps or recycled aggregate. This not only greatly simplifies a treatment procedure and avoids the production of a large amount of powder, but also significantly reduces the consumption of fresh concrete and corresponding new cement, providing a significant energy-saving and carbon-reduction effect. In addition, because the steel bars inside the old concrete component can still provide important support during the service life of new components, which not only avoids a complicated process of extracting the old steel bars and subsequent complicated processes such as smelting, along with the associated energy consumption and CO₂ emission, but also reduces the demand for steel bars matched with the new components, undoubtedly providing greater advantages for the present invention. Prior to this, there have been no reports internationally on direct recycling of the old beam-type components and old column-type components in new components.

According to the practice of the present invention, although the steel bars inside the old concrete components are no longer extracted and sold, which seems to reduce some economic income, this is also a main reason why predecessors have not thought of directly recycling the old beam-type components and old column-type components. However, saving in equipment and labor costs related to crushing the old concrete components and extracting steel bars, the avoidance of substantial expenses for transporting and dumping powder, the reduction in steel bar demands for new components due to a load-bearing role of steel bar inside the old concrete components, and cost saving brought by the significant reduction in the consumption of fresh concrete and corresponding new cement due to the direct recycling of the old concrete components for the new components contribute to the excellent comprehensive economic benefits for the present invention.

In summary, the present invention has good social, economic, and ecological benefits.

According to the method of the present invention, a series of embodiments can also be provided, which does not limit the present invention in any form. Therefore, any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be regarded as equivalent alternatives and are included within the scope of protection of the present invention.