CN113293930A

CN113293930A - UHPC pipe restraint recycled concrete post externally pasted with FRP cloth

Info

Publication number: CN113293930A
Application number: CN202110553000.4A
Authority: CN
Inventors: 杨贞军; 李雅祺; 彭程明
Original assignee: Wuhan University WHU
Current assignee: Wuhan University WHU
Priority date: 2021-05-20
Filing date: 2021-05-20
Publication date: 2021-08-24

Abstract

The invention discloses a UHPC pipe constraining recycled concrete column with FRP cloth on the outside, comprising a FRP layer, a UHPFRC pipe and recycled concrete; the FRP layer is externally affixed with a UHPFRC pipe as an external circumferential constraint of a composite column; the recycled concrete It is poured and filled in UHPFRC pipe, which acts as a permanent formwork and is connected to the concrete inside. The recycled concrete is concrete containing recycled concrete blocks or recycled concrete aggregates. The FRP cloth acts as a circumferential restraint for the ultra-high performance steel fiber reinforced concrete-recycled concrete composite column, and the UHPFRC pipe not only acts as a partial circumferential restraint for the recycled concrete, but also bears part of the vertical load. Compared with traditional steel tube concrete, UHPFRC has better interface mechanical properties and fresh concrete, and has better structural integrity. FRP cloth restraint can further improve the bearing capacity of composite columns, and has better durability and fire resistance. Good resistance to earthquakes, shocks, explosions and other disasters. In addition, the use of recycled concrete to partially replace conventional concrete has high economic benefits, good environmental protection and sustainable development value.

Description

UHPC pipe restraint recycled concrete post externally pasted with FRP cloth

Technical Field

The invention relates to the field of building materials and structural engineering, in particular to a UHPC (ultra high performance polycarbonate) pipe confined recycled concrete column externally attached with FRP (fiber reinforced plastic) cloth.

Background

The annual consumption of concrete as the most widespread building material at present has reached 175 hundred million tons throughout the world. To manufacture these concretes, approximately 130 million tons of sand, 27 million tons of cement, 18 million tons of fresh water resources, and 50 million of various raw materials for manufacturing cement are consumed each year. The concrete industry not only causes a huge consumption of earth resources, but also has a severe impact on the environment, releasing over 16 million tons of carbon dioxide each year, accounting for 7% of the worldwide human-active carbon dioxide emissions each year. On the other hand, during the concrete construction and demolition, a large amount of construction waste is generated, and the landfill of the construction waste consumes a large amount of money, land resources and has a harmful effect on the environment.

When new concrete is poured, the waste concrete is crushed and screened into recycled aggregate, and when the new concrete is poured, part of natural aggregate is replaced, so that the exploitation of the natural aggregate and the consumption of cement can be effectively reduced, the problem of treatment of construction waste can be solved, and the building material is an advanced green sustainable development building material. But as the recycled aggregate has a plurality of defects such as more edges and corners of particles, rough surface, microcracks, high porosity and the like, the properties of the recycled concrete are reduced compared with those of the common concrete material, and the strength difference is obvious.

The strength of the steel tube-recycled concrete can be effectively improved by restraining the recycled concrete with the steel tube, but the steel tube-recycled concrete still has the problems of poor interface performance of steel and concrete and poor structural integrity. And the steel has poor durability, and an additional anticorrosive coating is often needed, so that the cost of the component is greatly increased.

Disclosure of Invention

In order to overcome the problems, the invention provides an ultra-high performance steel fiber concrete-recycled concrete composite column bound by sticking FRP cloth, which adopts the FRP cloth and ultra-high performance fiber concrete (UHPFRC) to jointly bind recycled concrete. The composite column has excellent strength, ductility, durability and sustainability.

The Fiber Reinforced Plastic (FRP) has the advantages of light weight, high strength, good corrosion resistance and wear resistance, convenience in installation and the like, and is used for applying transverse restraint to the ultra-high performance steel fiber concrete-recycled concrete composite column, so that the composite column can not only improve considerable compressive strength under the action of three-dimensional stress, but also greatly improve the durability under the protection of external FRP cloth. UHPFRC is a relatively new fiber reinforced cement-based material that randomly embeds high-strength steel/polymer fibers into dense, high-strength mortar, typically with compressive strengths in excess of 150MPa, and tensile and flexural strengths up to 12MPa and 40MPa, respectively. The UHPFRC and the recycled concrete work together, so that the bearing capacity and the toughness of the column can be obviously improved, and disasters such as earthquake, impact, explosion and the like can be well resisted. In addition, concrete whose density, modulus and coefficient of thermal expansion are very close to ordinary strength; this will greatly improve the deformation coordination between the UHPFRC pipe and the confined concrete. In addition, the recycled aggregate or the recycled block body is used for partially replacing the coarse aggregate in the concrete, so that the method has the significance of sustainable development.

The invention adopts the following specific technical scheme:

a UHPC pipe constraint recycled concrete column externally pasted with FRP cloth comprises an FRP layer, an UHPFRC pipe and recycled concrete; the FRP layer is externally attached to the UHPFRC pipe to serve as external circumferential constraint of the composite column; the recycled concrete is poured and filled in the UHPFRC pipe, and the UHPFRC pipe is used as a permanent formwork to be connected with the concrete inside into a whole. The recycled concrete is concrete containing recycled concrete blocks or recycled concrete aggregate.

Further, the FRP layer is preferably woven cloth of carbon fibers, glass fibers, aramid fibers or basalt fibers; the number of the outer layers is 2-5, and the lap length of each layer is 80-120 mm and is uniformly distributed in the circumferential direction.

Furthermore, reinforcing steel bars are arranged in concrete in the UHPFRC pipe, and the axial compression ratio of the concrete column is not more than 0.65.

Furthermore, when the recycled concrete is concrete containing recycled concrete blocks, the mass ratio of the recycled concrete blocks is 25-35%; the recycled concrete blocks are waste concrete blocks except old buildings and protective layers and reinforcing steel bars, and the characteristic size of the recycled concrete blocks is 40-300 mm.

Furthermore, when the recycled concrete is concrete containing recycled concrete aggregate, the recycled concrete comprises the following components in parts by mass: 800 portions of cement, 1000 portions of coarse aggregate, 1000 portions of fine aggregate and 400 portions of water; wherein the recycled aggregate content of the coarse aggregate is not more than 40 wt%; the recycled aggregate is particles with the particle size of 4.75-31.5mm, which are obtained by crushing and processing waste concrete blocks obtained after demolishing old buildings and removing protective layers and reinforcing steel bars.

Further, the UHPFRC pipe comprises the following components in parts by mass: 1300 parts of cement, 100 parts of mineral admixture, 650 parts of fine sand, 1200 parts of quartz powder, 30-60 parts of water reducing agent, 400 parts of water and 150 parts of steel fiber; the mineral admixture is silica fume or a mixture of the silica fume, fly ash and blast furnace slag; the steel fiber is provided with a profiled cross section fiber, and the profiled cross section fiber comprises one or more of an end hook fiber, a wave-shaped fiber or a spiral steel fiber.

Further, the cross-sectional shape of the UHPFRC pipe is circular, and the thickness is 20mm-120 mm.

Furthermore, the UHPFRC pipe is connected with the node through a high-strength friction type bolt, and is externally coated with FRP constraint to the node.

Furthermore, a lining used for preventing the pipe body from being damaged in the pouring process is arranged in the UHPFRC pipe of the concrete column, and the lining adopts a thin steel pipe or a woven fiber net.

Still further, the woven fiber web is selected from steel fibers, carbon fibers, basalt fibers, polyvinyl alcohol fibers, or polyethylene fibers; the thickness of the thin steel pipe is 0.8mm-10 mm.

According to GB50010-2010 concrete structure design standard and related documents, the normal section compressive bearing capacity of the bonded FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column provided by the invention is as follows:

wherein N is an axial pressure design value;

is the stability factor of the reinforced concrete member; f. of_cc1For the designed axial compressive strength of FRP constraint common concrete,

f_c1for the designed axial compressive strength of the unconstrained concrete, f_fIs the tensile strength, t, of the FRP composite material_fThe thickness of the FRP composite material is d, and the outer diameter of the FRP composite material is d; f. of_cc2For the FRP constraint UHPFRC axial compression strength design value,

f_c2the designed value of the axial compressive strength of the unconstrained UHPFRC; a. the₁Is the area of the section of common concrete; a. the₂Is the cross-sectional area of the UHPFRC tube; f. of_y' is a designed value of the compressive yield strength of longitudinal common reinforcing steel bars; a. the_s' is the cross-sectional area of the entire longitudinal plain rebar.

The FRP cloth constraint ultra-high performance steel fiber concrete-recycled concrete composite column has the advantage that the normal section bearing capacity is obviously improved compared with that of a common concrete column under the condition of the same section area. Table 1 lists the normal section bearing capacity of a round column, with no reinforcement, with an ultra high performance steel fiber concrete pipe restraining a normal concrete column. Wherein the standard value of the compressive strength of the common concrete cube is 30Mpa, the standard value of the compressive strength of the UHPFRC cube is 170Mpa, and the calculation length of the column is 3 m.

According to the design Specification for concrete Structure GB50010-2010, the design value of the axial compressive strength of the common concrete is f_c114.3 MPa; standard value of UHPFRC compressive strength is expressed as f_ck＝0.88α_c1α_c2f_cu,kIs subjected to reduction, f_ck2106.7MPa, according to the design specification NFP18-710, f, of UHPFRC, issued in France_c＝α_ccf_ck/γ_cFor UHPFRC materials, γ_cTaking 1.3, alpha_ccWhen 0.85 is used, the designed axial compressive strength is f_c269.8 MPa; for CFRP cloth, f_f＝4300MPa，t_f＝0.168mm。

In the table, d is the diameter of the section of the circular concrete;

t is the UHPFRC tube thickness;

is the stability factor of the reinforced concrete member;

a is the total cross-sectional area of the column, A ═ A₁+A₂Wherein, in the step (A),

A₂＝π(dt+t²)；

N₁the normal section of the FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column can bear load value,

N₂the normal section of the common concrete column can bear the load value,

N₃is an ultra-high performance steel fiber concrete-recycled concrete composite column (N) without FRP constraint₁Comparative example (C)

Bearable load value of normal section

η₁Is N₁And N₂Is N₁/N₂；

η₂Is N₁And N₃Is N₁/N₃；

TABLE 1 circular column with right section capable of bearing load

The calculation parameters of the table show that when the composite column has the same cross-sectional area, the FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column has a larger bearing capacity advantage compared with a common concrete column, and the larger the thickness of the UHPFRC is, the smaller the size of a common concrete part in the composite column is, the more obvious the advantage is. And compared with a UHPFRC concrete column (without an FRP layer), the FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column has the bearable load promotion of 167 percent at most. When the same load design value is adopted, compared with a UHPFRC concrete column, the FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column can adopt smaller sectional area size.

The invention discloses an FRP cloth restrained ultra-high performance steel fiber concrete-recycled concrete composite column, which adopts FRP cloth and ultra-high performance fiber concrete (UHPFRC) to restrain recycled concrete together. Compared with the traditional steel pipe concrete, the UHPFRC has better interface mechanical property and good structural integrity with fresh concrete, and the composite column has better durability and fire resistance and can well resist disasters such as earthquake, impact, explosion and the like. In addition, the recycled concrete is adopted to replace part of conventional concrete, so that the economic benefit is high, the environmental protection performance is good, and the sustainable development value is achieved. The composite column has the advantages of convenient construction, simple process and low cost.

Drawings

FIG. 1 is a schematic diagram of an FRP cloth-constrained ultra-high performance steel fiber concrete-recycled block concrete composite column, wherein a is a horizontal section view and b is a vertical section view;

FIG. 2 is a schematic diagram of an FRP cloth-constrained ultra-high performance steel fiber concrete-recycled block concrete reinforced composite column, wherein a is a horizontal section view and b is a vertical section view;

FIG. 3 is a schematic diagram of an FRP cloth-constrained ultra-high performance steel fiber concrete-recycled aggregate concrete composite column, wherein a is a horizontal section view and b is a vertical section view;

FIG. 4 is a schematic diagram of an FRP cloth-constrained ultrahigh-performance steel fiber concrete-recycled aggregate concrete reinforced composite column, wherein a is a horizontal section view and b is a vertical section view.

Detailed Description

The present invention will be described in further detail with reference to specific examples, but the present invention is not limited thereto.

In the following embodiments, unless otherwise specified, the reagents and materials are well known and commercially available. In the following examples, the raw materials used are as follows:

the FRP is carbon fiber woven cloth with the thickness of 0.168mm, the elastic modulus of 250GPa and the tensile strength of 4300N/mm²The elongation at break was 1.7%.

In the UHPFRC tube, the adopted steel fiber has the diameter of 0.2mm, the length of 12mm, the length-diameter ratio of 60 and the tensile strength of 2700 Mpa. The adopted cement is ordinary portland cement. The specific surface area of the silica fume is 22m²Per g, wherein SiO₂The content is more than or equal to 90 percent, the grain size range of the fine sand is 0.1mm-0.5mm, the grain size of the quartz powder is 5 mu m-50 mu m, and SiO is₂The content is more than or equal to 95 percent. The high-efficiency water reducing agent is a polycarboxylic acid high-efficiency powder water reducing agent, and the water reducing efficiency is more than or equal to 30 percent. The water is industrial water.

The recycled concrete blocks in the recycled concrete are waste concrete blocks obtained by removing a protective layer and reinforcing steel bars from an old building, and the characteristic size of the waste concrete blocks is 60-120 mm.

The recycled aggregate in the recycled concrete is particles with the particle size of 4.75-40mm, which are obtained by crushing and processing waste concrete blocks obtained by dismantling old buildings and removing protective layers and reinforcing steel bars.

Example 1

In this example, the FRP cloth-constrained ultra-high performance steel fiber concrete-recycled block concrete composite column is shown in fig. 1. The concrete column is a composite column and consists of UHPFRC pipes and regenerated block concrete. The UHPFRC pipe is used as the external circumferential restraint of the concrete column, the recycled block and fresh concrete are poured and filled in the UHPFRC pipe, the UHPFRC pipe is used as a permanent template and is connected with the internal concrete into a whole, and then FRP cloth is coated outside to form the FRP restraint composite column.

In this example, the specific raw materials used are as follows:

the constraint FRP cloth is carbon fiber woven cloth, the thickness is 0.168mm, the elastic modulus is 250GPa, and the tensile strength is 4300N/mm²The elongation at break was 1.7%.

The fresh concrete is obtained by mixing and stirring portland cement, coarse aggregate, fine aggregate and water, wherein: the cement is silicate cement; the coarse aggregate is pebbles with the particle size of 5mm-15 mm; the fine aggregate is river sand which is medium sand with good gradation; the water is industrial water.

The mixing ratio (mass ratio) of the fresh concrete is shown in the following table 3.

TABLE 3 common concrete mix proportions

The ultra-high performance steel fiber concrete pipe (UHPFRC pipe) of this embodiment adopts the pipe, and the cross section diameter is 300mm, and the height is 1200mm, and UHPFRC pipe wall thickness is 30mm, and old concrete block particle size is 60mm-120mm, and the substitution rate to the column body is 25 wt%. In the UHPFRC pipe in this embodiment, the UHPFRC concrete raw material components include cement, silica fume, fine sand, water, quartz powder, high efficiency water reducing agent, and steel fiber. In the adoption of the UHPFRC pipe, the adopted steel fiber is linear steel fiber, the diameter is 0.2mm, the length is 12mm, the length-diameter ratio is 60, and the tensile strength is 2700 MPa. The adopted cement is ordinary portland cement. The specific surface area of the silica fume is 22m²Per g, wherein SiO₂The content is more than or equal to 90 percent, the grain size range of the fine sand is 0.1mm-0.5mm, the grain size of the quartz powder is 5 mu m-50 mu m, and SiO is₂The content is more than or equal to 95 percent. The high-efficiency water reducing agent is a polycarboxylic acid high-efficiency powder water reducing agent, and the water reducing efficiency is more than or equal to 30 percent. The water is industrial water.

The mass ratios of the components in UHPFRC are shown in Table 4 below.

TABLE 4 UHPFRC mix ratio

The FRP cloth constraint ultra-high performance steel fiber concrete-recycled block concrete composite column of the embodiment has the following specific manufacturing process: and mixing the UHPFRC according to the components in the table 4 in advance, pouring the UHPFRC pipe, and curing for 28 days under standard conditions. The UHPFRC pipe was then used as a casting side form and the bottom side was sealed with a wooden form. And a hoop thin steel sheet with the thickness of 0.8mm is placed in the UHPFRC, and the hoop thin steel sheet is tightly attached to the inner side surface of the UHPFRC pipe in a thin steel pipe mode with the outer diameter slightly smaller than the inner diameter of the UHPFRC pipe to be used as a lining so as to prevent the UHPFRC pipe from being damaged during pouring. And (3) placing the old concrete block into the UHPFRC, and pouring the newly mixed common concrete into the UHPFRC, wherein the two kinds of concrete need to be accurately measured, so that the mass ratio of the old concrete block to the mixed concrete is 25%. After the concrete is poured into the column, the concrete is fully vibrated by using a vibrating rod, so that the old concrete block and the newly-mixed common concrete are uniformly mixed, distributed and filled in the column. And (5) curing for 28d under standard conditions, and then coating FRP cloth.

As shown in the calculations of tables 1 and 2, the ultra-high performance steel fiber concrete pipe-confined concrete column of the present embodiment has a greater load bearing advantage compared to the UHPFRC concrete column when having the same cross-sectional area. Compared with the UHPFRC concrete column, the FRP cloth restrained composite column has better durability. In addition, the use of the recycled concrete blocks also enables the concrete column to have economic benefits and environmental benefits.

Example 2

This example differs from example 1 only in that a reinforcement cage is placed inside the UHPFRC tube, and the other operations are the same.

The concrete column structure is shown in figure 2. Specifically, the cross-sectional diameter of the UHPFRC pipe of the present example is 300mm, the height is 1200mm, the wall thickness of the UHPFRC pipe is 30mm, the particle size of the old concrete block is 60mm to 120mm, and the substitution rate for the column is 25%. HRB 335-grade steel bars are selected as longitudinal steel bars in the column, the diameter of the steel bars is 14mm, the total number of the steel bars is 12, the HRB 335-grade steel bars are adopted as stirrups, the diameter of the stirrups is 10mm, and the distance between the stirrups is 100 mm. In this example, the blend ratio of the FRP material, the UHPFRC pipe and the recycled block concrete was the same as in example 1.

The FRP cloth constraint ultra-high performance steel fiber concrete-recycled block concrete composite column of the embodiment has the following specific manufacturing process: and pouring a UHPFRC pipe according to the components in the table 4 in advance, and curing for 28 days under standard conditions. The UHPFRC pipe was then used as a casting side form and the bottom side was sealed with a wooden form. And a hoop thin steel sheet with the thickness of 0.8mm is placed in the UHPFRC, and the hoop thin steel sheet is tightly attached to the inner side surface of the UHPFRC pipe to be used as a lining in the form of a thin steel pipe with the outer diameter slightly smaller than the inner diameter of the UHPFRC pipe so as to prevent the UHPFRC pipe from being damaged during pouring. And then, placing the bound reinforcement cage in a UHPFRC pipe body. And (3) placing the old concrete block into the UHPFRC, and pouring the newly mixed common concrete into the UHPFRC, wherein the two kinds of concrete need to be accurately measured, so that the mass ratio of the old concrete block to the mixed concrete is 25%. After the concrete is poured into the column, the concrete is fully vibrated by using a vibrating rod, so that the old concrete block and the newly-mixed common concrete are uniformly mixed, distributed and filled in the column. Curing for 28d, and then coating FRP cloth.

Compared with embodiment 1, the embodiment has the advantage that the strength of concrete is further enhanced due to the fact that the reinforcement cage is placed inside.

Example 3

In this example, the FRP cloth-constrained ultra-high performance steel fiber concrete-recycled aggregate concrete composite column is shown in fig. 3. The concrete column is a composite column and consists of a UHPFRC pipe and recycled aggregate concrete. The UHPFRC pipe is used as the external circumferential restraint of the concrete column, the recycled aggregate concrete is poured and filled in the UHPFRC pipe, the UHPFRC pipe is used as a permanent template and is connected with the internal concrete into a whole, and then FRP cloth is coated outside to form the FRP restraint composite column.

In this example, the specific raw materials used are as follows:

The recycled aggregate concrete is obtained by mixing and stirring portland cement, coarse aggregate, fine aggregate and water, wherein: the cement is silicate cement; 25% of the coarse aggregate adopts recycled aggregate, and the other adopts pebbles with the particle size of 5mm-15 mm; the fine aggregate is river sand which is medium sand with good gradation; the water is industrial water.

The mixing ratio (mass ratio) of the recycled aggregate concrete is shown in table 3 below.

TABLE 3 recycled aggregate concrete mixing ratio

The ultra-high performance steel fiber reinforced concrete pipe (UHPFRC pipe) of this example is a round pipe, the diameter of the cross section is 300mm, the height is 1200mm, and the wall thickness of the UHPFRC pipe is 30 mm. The substitution rate of recycled aggregate in the recycled concrete is 25 percent. In the UHPFRC pipe in this embodiment, the UHPFRC concrete raw material components include cement, silica fume, fine sand, water, quartz powder, high efficiency water reducing agent, and steel fiber. In the adoption of the UHPFRC pipe, the adopted steel fiber is linear steel fiber, the diameter is 0.2mm, the length is 12mm, the length-diameter ratio is 60, and the tensile strength is 2700 MPa. The adopted cement is ordinary portland cement. The specific surface area of the silica fume is 22m²Per g, wherein SiO₂The content is more than or equal to 90 percent, the grain size range of the fine sand is 0.1mm-0.5mm, the grain size of the quartz powder is 5 mu m-50 mu m, and SiO is₂The content is more than or equal to 95 percent. The high-efficiency water reducing agent is a polycarboxylic acid high-efficiency powder water reducing agent, and the water reducing efficiency is more than or equal to 30 percent. The water is industrial water.

The mass ratios of the components in UHPFRC are shown in Table 4 below.

TABLE 4 UHPFRC mix ratio

The FRP cloth restrained ultra-high performance steel fiber concrete-recycled aggregate concrete composite column of the embodiment has the following specific manufacturing process: and mixing the UHPFRC according to the components in the table 4 in advance, pouring the UHPFRC pipe, and curing for 28 days under standard conditions. The UHPFRC pipe was then used as a casting side form and the bottom side was sealed with a wooden form. And a hoop thin steel sheet with the thickness of 0.8mm is placed in the UHPFRC, and the hoop thin steel sheet is tightly attached to the inner side surface of the UHPFRC pipe in a thin steel pipe mode with the outer diameter slightly smaller than the inner diameter of the UHPFRC pipe to be used as a lining so as to prevent the UHPFRC pipe from being damaged during pouring. And pouring the freshly mixed recycled aggregate concrete into the UHPFRC pipe, wherein the replacement rate of the recycled aggregate is 25%. And after the concrete is injected, fully vibrating by using a vibrating rod. And (5) curing for 28d under standard conditions, and then coating FRP cloth.

As shown in the calculations of tables 1 and 2, the ultra-high performance steel fiber concrete pipe-confined concrete column of the present embodiment has a greater load bearing advantage compared to the UHPFRC concrete column when having the same cross-sectional area. Compared with the UHPFRC concrete column, the FRP cloth restrained composite column has better durability. In addition, the use of the recycled aggregate enables the concrete column to have economic benefits and environmental benefits.

Example 4

This example differs from example 3 only in that a reinforcement cage is placed inside the UHPFRC tube, and the other things are the same.

The concrete column structure is shown in fig. 4. Specifically, the cross-sectional diameter of the UHPFRC tube of this example is 300mm, the height is 1200mm, and the wall thickness of the UHPFRC tube is 30 mm. The substitution rate of recycled aggregate in the recycled concrete is 25 percent. HRB 335-grade steel bars are selected as longitudinal steel bars in the column, the diameter of the steel bars is 14mm, the total number of the steel bars is 12, the HRB 335-grade steel bars are adopted as stirrups, the diameter of the stirrups is 10mm, and the distance between the stirrups is 100 mm. In this example, the blending ratio of the FRP material, the UHPFRC pipe and the recycled aggregate concrete was the same as in example 1.

The FRP cloth restrained ultra-high performance steel fiber concrete-recycled aggregate concrete composite column of the embodiment has the following specific manufacturing process: and pouring a UHPFRC pipe according to the components in the table 4 in advance, and curing for 28 days under standard conditions. The UHPFRC pipe was then used as a casting side form and the bottom side was sealed with a wooden form. And a hoop thin steel sheet with the thickness of 0.8mm is placed in the UHPFRC, and the hoop thin steel sheet is tightly attached to the inner side surface of the UHPFRC pipe to be used as a lining in the form of a thin steel pipe with the outer diameter slightly smaller than the inner diameter of the UHPFRC pipe so as to prevent the UHPFRC pipe from being damaged during pouring. And then, placing the bound reinforcement cage in a UHPFRC pipe body. And pouring the freshly mixed recycled aggregate concrete into the UHPFRC pipe, wherein the replacement rate of the recycled aggregate is 25%. And after the concrete is injected, fully vibrating by using a vibrating rod. Curing for 28d, and then coating FRP cloth.

The above description is only for the preferred embodiment of the present invention, but the scope of the present invention is not limited thereto, and any modification, equivalent replacement, and improvement made by those skilled in the art within the technical scope of the present invention should be included in the scope of the present invention.

Claims

1. a UHPC pipe constraining recycled concrete column with FRP cloth is attached, it is characterized in that, comprise FRP layer, UHPFRC pipe, recycled concrete; Described FRP layer is attached to UHPFRC pipe outside as the outer circumferential constraint of composite column; Described The recycled concrete is poured and filled in the UHPFRC pipe, and the UHPFRC pipe is used as a permanent formwork to be connected with the inner recycled concrete into a whole; the recycled concrete is concrete containing recycled concrete blocks or recycled concrete aggregates.

2. The UHPC pipe-restrained recycled concrete column of the externally attached FRP cloth according to claim 1, is characterized in that: the FRP layer is preferably carbon fiber, glass fiber, aramid fiber or basalt fiber woven cloth; 2 to 5 layers, each layer has a lap length of 80 to 120 mm and is evenly distributed in the ring direction.

3 . The UHPC pipe restrained recycled concrete column with FRP cloth attached to the outside according to claim 1 , wherein the concrete in the UHPFRC pipe is provided with steel bars, and the axial compression ratio of the concrete column does not exceed 0.65. 4 .

4 . The UHPC pipe-bound recycled concrete column with FRP cloth attached to the outside according to claim 1 , wherein, when the recycled concrete is concrete containing recycled concrete blocks, the mass ratio of the recycled concrete blocks is 25% to 35%. 5 . %; the recycled concrete block is a waste concrete block after removing the old building and removing the protective layer and steel bars, and its characteristic size is 40mm-300mm.

5. the UHPC pipe restraint regenerated aggregate concrete column of FRP cloth outside according to claim 1, is characterized in that, when described regenerated concrete is the concrete that contains regenerated concrete aggregate, its mass parts are composed: cement 400-800 1000-1300 parts of coarse aggregate, 500-1000 parts of fine aggregate, and 200-400 parts of water; the content of recycled aggregate in the coarse aggregate shall not exceed 40wt%; The waste concrete blocks after the protective layer and the reinforcement are crushed and processed to obtain particles with a particle size of 4.75-31.5mm.

6. the UHPC pipe restraint regeneration concrete column of the external sticking FRP cloth according to claim 1, it is characterised in that the mass components of the UHPFRC pipe are: 1000-1300 parts of cement, 100-650 parts of mineral admixtures, 900-1200 parts of fine sand, 100-300 parts of quartz powder, 30-60 parts of water reducing agent, 150-400 parts of water, 50-300 parts of steel fiber; the mineral admixture is silica fume, or silica fume and The mixture of fly ash and blast furnace slag; the steel fibers have special-shaped cross-section fibers, and the special-shaped cross-section fibers include one or more of end hook fibers, corrugated fibers or spiral steel fibers.

7 . The UHPC pipe restrained recycled concrete column with FRP cloth attached to the outside according to claim 1 , wherein the cross-sectional shape of the UHPFRC pipe is circular, and the thickness is 20mm-120mm. 8 .

8 . The UHPC pipe constraining recycled concrete column with FRP cloth attached to the outside according to claim 1 , wherein the UHPFRC pipe is connected to the node through high-strength friction bolts, and the outer FRP is constrained to the node. 9 .

9. The UHPC pipe constraining recycled concrete column of any one of claims 1-8, wherein the UHPFRC pipe of the concrete column has a built-in lining for preventing damage to the pipe body during pouring, and the The lining is made of thin steel pipe or woven fiber mesh.