Seawater and sea sand concrete structure based on SMA fiber reinforced FRP ribs and preparation method

Abstract

The invention discloses a seawater and sea sand concrete structure based on SMA fiber reinforced FRP ribs and a preparation method. The concrete structure comprises a lower SMA fiber reinforced layer, seawater and sea sand concrete and an upper SMA fiber reinforced layer. The seawater and sea sand concrete is positioned on the lower SMA fiber reinforced layer and the upper SMA fiber reinforced layer; the lower SMA fiber reinforced layer and the upper SMA fiber reinforced layer comprise a seawater and sea sand concrete base body, FRP bars and SMA fibers, and seawater and sea sand concrete comprises seawater, sea sand, cement, a proper amount of mineral admixtures and chemical admixtures, according to the preparation method of the FRP bar seawater and sea sand concrete structure based on SMA fiber reinforcement, the FRP bars and the SMA fibers are introduced, so that the seawater and sea sand concrete structure is obtained; by utilizing the corrosion resistance of the FRP and the unique shape memory effect of the SMA, the concrete has pre-compressive stress and self-healing repairing capacity, and the bearing capacity, durability and corrosion resistance of the structure are improved.

Description

Technical Field

[0001] This invention relates to the field of civil engineering, specifically to a seawater sand concrete structure based on SMA fiber-reinforced FRP bars and its preparation method. Background Technology

[0002] The extensive use of concrete in current technologies has led to a severe shortage of traditional building materials such as river sand. While seawater sand concrete, as a new material to replace traditional freshwater river sand concrete, has advantages such as local sourcing and freshwater conservation, the high concentration of chloride ions in seawater severely corrodes the reinforcing steel, resulting in reduced structural safety and increased maintenance costs. FRP-reinforced concrete structures have lower cracking loads, and the bond performance between FRP reinforcement and concrete deteriorates over long-term exposure to seawater. Summary of the Invention

[0003] Purpose of the invention: This invention proposes a seawater sand concrete structure and preparation method based on SMA fiber-reinforced FRP bars. By introducing FRP bars and SMA fibers, and utilizing the corrosion resistance of FRP and the unique shape memory effect of SMA, the concrete is given pre-stress and self-healing repair capabilities, thereby improving the load-bearing capacity, durability and corrosion resistance of the structure.

[0004] Technical solution: The present invention provides a seawater sand concrete structure based on SMA fiber reinforced FRP bars, comprising seawater sand concrete; the seawater sand concrete includes a pure seawater sand concrete layer and SMA fiber reinforced layers located on both sides of the pure seawater sand concrete layer, wherein the SMA fiber reinforced layers are formed by adding FRP bars and SMA fibers into the seawater sand concrete.

[0005] Preferably, the volume fraction of SMA fibers in the SMA fiber reinforcement layer is 0.2%-0.8%.

[0006] Preferably, the FRP reinforcement is made of carbon fiber, glass fiber or aramid fiber reinforced polymer reinforcement.

[0007] Preferably, the seawater and sea sand concrete comprises seawater, sea sand, cement, coarse aggregate, mineral admixtures and chemical admixtures, wherein the component ratio of seawater, sea sand, cement, coarse aggregate, mineral admixtures and chemical admixtures is 37.5:116.25:70:212.5:17.5:1.

[0008] Preferably, the coarse aggregate is gravel, the mineral admixture is fly ash, and the chemical additive is a water-reducing agent.

[0009] A method for preparing a seawater sand concrete structure based on SMA fiber-reinforced FRP bars includes the following steps:

[0010] Step 1: Pretreatment of SMA fibers: SMA fibers are cleaned and dried, then pre-stretched, and then the two ends of the SMA fibers are bent into hook shapes.

[0011] Step 2, reinforcement arrangement: Select appropriate FRP reinforcement according to the structural design requirements, and cut and process it according to the design requirements; tie and fix the FRP reinforcement to the appropriate position of the template according to the design requirements, arrange the first partition and the second partition inside the template, make holes at the corresponding stirrup positions of the first partition and the second partition, and arrange the stirrups that meet the requirements.

[0012] Step 3: Mix cement, sea sand, seawater, coarse aggregate, and appropriate amounts of mineral admixtures and chemical additives to prepare pure seawater sand concrete; add the pure seawater sand concrete to the SMA fibers processed in Step 1 and mix thoroughly to prepare SMA fiber reinforced concrete.

[0013] Step 4, Concrete pouring: First, pour the intermediate pure seawater sand concrete, and after it has solidified, pour the SMA fiber reinforcement layer.

[0014] Preferably, in step three, the cement is silicate cement or sulfoaluminate cement, the mineral admixture is fly ash, and the chemical admixture is a high-efficiency water-reducing agent.

[0015] Preferably, step four specifically includes the following steps: first, remove the side panels of the template; then, pour the intermediate layer of seawater sand concrete between the first and second partitions; after pouring, vibrate and compact it; then, remove the first and second partitions respectively and install the side panels; next, place the template horizontally on the rollers with the opening facing upwards; then, pour the SMA fiber reinforced layer on one side of the seawater sand concrete; after solidification, remove the bottom plate of the template; place the solidified concrete structure on the rollers; then, pour the SMA fiber reinforced layer on the other side of the seawater sand concrete; after solidification.

[0016] Preferably, the specific steps of pouring the SMA fiber reinforced layer in step four include using several parallel chutes to pour the SMA fiber reinforced layer concrete prepared in step three into the chutes, controlling the frequency of the vibration table to orient the SMA fibers in the template, and simultaneously controlling the length of the telescopic rod of the template located below the chutes through an electric air pump, so that the rollers move horizontally and drive the template as a whole to move horizontally.

[0017] Preferably, after the SMA fiber reinforcement layer has solidified in step four, the SMA fiber reinforcement layer is heated by a heat gun.

[0018] Beneficial Effects: This invention discloses a seawater sand concrete structure based on SMA fiber reinforced FRP bars and its preparation method, which has the following beneficial effects: (1) It has a certain pre-compression stress, which significantly improves the bearing capacity. The recovery stress generated by the shape memory effect of SMA fibers actively applies a certain pressure to the surrounding concrete, effectively constrains the concrete, enhances the bond strength, and improves the bonding performance between FRP bars and concrete. (2) Because the ends of SMA fibers are constrained by concrete, there will be a shrinkage trend when the shape memory effect is generated, which reduces the width of cracks. It can be stimulated and recovered multiple times in the later stage, and the concrete has the self-healing repair ability. (3) It enhances durability. The combined use of FRP bars and SMA fibers effectively resists the corrosion of chloride ions in the seawater environment and extends the service life of the structure. (4) It is environmentally friendly and energy-saving. It uses seawater and sea sand as raw materials for concrete, saves freshwater resources, reduces river sand mining, and is environmentally friendly. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the overall structure of the SMA fiber-reinforced FRP bar seawater sand concrete according to the present invention;

[0020] Figure 2 This is a schematic diagram illustrating the fabrication of the SMA fiber reinforcement layer of the present invention;

[0021] Figure 3 This is a schematic diagram of the SMA fiber of the present invention;

[0022] Figure 4 This is a cross-sectional view of the SMA fiber of the present invention in a concrete structure;

[0023] Figure 5 This is a schematic diagram of the construction formwork for the FRP-reinforced seawater sand SMA concrete beam of the present invention. Detailed Implementation

[0024] As attached Figure 1 As shown, a seawater sand concrete structure based on SMA fiber reinforced FRP bars includes seawater sand concrete 2; FRP bars 8 and SMA fibers 7 are added to the upper end of the seawater sand concrete 2 to form an upper SMA fiber reinforced layer 1, and FRP bars 8 and SMA fibers 7 are added to the lower end of the seawater sand concrete 2 to form a lower SMA fiber reinforced layer 11. The SMA fiber reinforced layer includes the lower SMA fiber reinforced layer 11 and the upper SMA fiber reinforced layer 1.

[0025] The volume fraction of SMA fiber 7 in the SMA fiber reinforcement layer is 0.2%-0.8%. The FRP reinforcement is made of carbon fiber, glass fiber, or aramid fiber reinforced polymer. The seawater and sea sand concrete 2 comprises seawater, sea sand, cement, coarse aggregate, mineral admixtures, and chemical admixtures, with a component ratio of 37.5:116.25:70:212.5:17.5:1. The coarse aggregate is gravel, the mineral admixture is fly ash, and the chemical admixture is a water-reducing agent.

[0026] A method for preparing seawater sand concrete structures based on SMA fiber-reinforced FRP bars, and the specific implementation method of this construction technology:

[0027] First, the SMA fibers are pretreated by cleaning and drying to remove surface oil and impurities. Then, they are pre-stretched according to their recovery properties, and finally, both ends are bent into hook shapes. Figure 3 As shown.

[0028] Then, according to the structural design requirements, select appropriate FRP reinforcement material (such as carbon fiber reinforcement, glass fiber reinforcement, etc.) and cut and process it according to the design requirements. Then, install it into the template 5 according to the height of the SMA fiber reinforcement layer. Arrange stirrups 9 at the required spacing in the template 5. The template 5 is provided with a first partition 10 and a second partition 15 in the middle. The stirrups 9 are installed and fixed by passing through the first partition 10 and the second partition 15.

[0029] Next, the seawater sand concrete matrix is ​​prepared. Based on the concrete design requirements, cement (such as silicate cement, sulfoaluminate cement, etc.), sea sand (which needs to be washed to remove impurities and salt adhering to the surface), seawater, and appropriate amounts of mineral admixtures (such as fly ash, slag powder, etc.) and chemical admixtures (such as high-efficiency water-reducing agents, air-entraining agents, etc.) are selected. The above materials are added to a concrete mixer according to the predetermined proportions and thoroughly mixed to prepare seawater sand concrete 2, ensuring that all components are uniformly mixed to form a high-performance concrete mixture. Treated SMA fibers are added to a portion of the seawater sand concrete 2 during mixing.

[0030] like Figure 2 and Figure 4 and Figure 5As shown, the final concrete pouring begins. First, the side panels 51 of formwork 5 are removed. Seawater sand concrete 2 is poured between the first partition 10 and the second partition 15. Following general concrete construction requirements, the concrete is vibrated and compacted after pouring. Next, the first partition 10 and the second partition 15 on both sides are removed, and the side panels 51 are reinstalled in their original positions. Then, formwork 5 is placed horizontally with the opening facing upward on roller 12. The upper SMA fiber reinforced layer 1 is poured on one side of the seawater sand concrete 2. A narrow chute 4 with several parallel arrangements is used to pour the concrete mixture containing SMA fibers onto it. The frequency of the vibrating table 3 is controlled so that the fluid has a certain velocity in the chute. When the SMA fiber orientation has a certain angle with the flow direction, the velocity gradient in the fluid enveloping the fibers will drive the fibers to be parallel to the flow direction, thereby achieving fiber orientation in the cement matrix. Meanwhile, template 5 is a horizontally movable platform. The length of the telescopic rod 13 is controlled by an electric air pump 14, causing the roller 12 to move horizontally. This controls the horizontal movement rate of template 5 to be greater than the flow velocity of the cement matrix in the trough, creating a velocity difference at the interface between the chute 4 and template 5. This is equivalent to applying a tensile force to the cement matrix, causing it to elongate parallel to the flow velocity direction. This deformation reduces the tilt angle of the SAM fibers in the cement matrix, thus improving the effectiveness of fiber orientation. Through the back-and-forth movement of template 5, a certain thickness is poured each time, forming a multi-layered SMA fiber reinforced layer 11. After one day of setting, the concrete has a certain strength. Heating the concrete with a heat gun causes the SMA fibers to exhibit a shape memory effect, tending to shorten. However, because the ends of the concrete are anchored, internal pre-stress is formed. Finally, the base plate 52 of the formwork 5 is removed, and the solidified concrete structure is placed on the rollers 12. The lower SMA fiber reinforced layer 11 is poured on the other side of the seawater sand concrete 2. A narrow chute 4 with several parallel arrangements is used to pour the concrete mixture containing SMA fibers onto it. The frequency of the vibrating table 3 is controlled to ensure the fluid has a certain velocity within the chute. When the SMA fiber orientation is at a certain angle to the flow direction, the velocity gradient in the fluid enveloping the fibers drives the fibers parallel to the flow direction, thus achieving fiber orientation within the cement matrix. Simultaneously, the formwork 5 is a horizontally movable platform. The length of the telescopic rod 13 is controlled by the electric air pump 14, causing the rollers 12 to move horizontally. This controls the horizontal movement rate of the formwork 5 to be greater than the flow velocity of the cement matrix within the chute, creating a velocity difference at the junction of the chute 4 and the formwork 5. This is equivalent to applying a tensile force to the cement matrix, stretching the cement matrix parallel to the flow direction. This deformation reduces the tilt angle of the SMA fibers within the cement matrix, thereby improving the effectiveness of fiber orientation. By moving the template 5 back and forth, a certain thickness is poured each time, forming a multi-layered SMA fiber reinforced layer 11.After a day of setting, the concrete has a certain strength. When the concrete is heated with a heat gun, the SMA fibers produce a shape memory effect and tend to shrink. However, because the concrete is anchored at both ends, internal prestress is formed.

[0031] A method for preparing a seawater sand concrete structure based on SMA fiber-reinforced FRP bars specifically includes the following steps:

[0032] Step 1: Pretreatment of SMA fiber 7: SMA fiber 7 is cleaned and dried, then pre-stretched, and then both ends of SMA fiber 7 are bent into a hook shape.

[0033] Step 2, reinforcement arrangement: Select appropriate FRP reinforcement 8 according to the structural design requirements, and cut and process it according to the design requirements; then tie and fix the FRP reinforcement 8 to the appropriate position of the template 6 according to the design requirements, and make holes at the corresponding stirrup positions of the first partition 10 and the second partition 15, and arrange the stirrups 9 that meet the requirements.

[0034] Step 3, Concrete matrix preparation: Seawater sand concrete 2 is prepared by mixing cement, sea sand, seawater, coarse aggregate, and appropriate amounts of mineral admixtures and chemical additives; SMA fiber reinforced concrete is prepared by adding seawater sand concrete 2 to the SMA fiber 7 processed in step 1 and mixing thoroughly.

[0035] Step 4: Concrete pouring; First, pour the middle seawater sand concrete 2. After it has solidified, pour the upper SMA fiber reinforced layer 1, followed by the lower SMA fiber reinforced layer 11.

[0036] Step four specifically includes the following steps: First, remove the side panel 51 of the template 5. Then, pour the intermediate layer of seawater sand concrete 2 between the first partition 10 and the second partition 15. After pouring, vibrate and compact it. Then, remove the first partition 10 and the second partition 15 respectively and install the side panel 51. Next, place the template 5 horizontally with the opening facing upward on the roller 12. Then, pour the upper SMA fiber reinforced layer 1 on one side of the seawater sand concrete 2. After solidification, remove the bottom plate 52 of the template 5. Place the solidified concrete structure on the roller 12. Then, pour the lower SMA fiber reinforced layer 11 on the other side of the seawater sand concrete 2. After solidification, remove the bottom plate 52 of the template 5. Place the solidified concrete structure on the roller 12. Then, pour the lower SMA fiber reinforced layer 11 on the other side of the seawater sand concrete 2.

[0037] Step four, the specific steps for pouring the SMA fiber-reinforced layer, include using several parallel chutes 4 to pour the SMA fiber-reinforced concrete prepared in step three into the chutes 4; controlling the frequency of the vibrating table 3 to orient the SMA fibers 7 within the template 5; and simultaneously, controlling the length of the telescopic rod 13 of the template 5 located below the chutes 4 via an electric air pump 14, causing the rollers 12 to move horizontally, thus moving the template 5 horizontally as a whole. After the SMA fiber-reinforced layer has solidified in step four, it is heated by a heat gun, which in turn heats the concrete, causing the SMA fibers to produce a shape memory effect and constrain the surrounding concrete. The heating excitation parameters (such as temperature and excitation time) are set according to the characteristics of the SMA fibers and the structural design requirements. Subsequently, the concrete structure is cured according to standard curing procedures to ensure that the concrete reaches the design strength.

[0038] The seawater sand concrete structure based on SMA fiber-reinforced FRP bars proposed in this invention possesses a certain pre-compression stress, significantly improving its load-bearing capacity. The SMA fibers, through the shape memory effect, generate recovery stress, actively applying pressure to the surrounding concrete, effectively constraining it, enhancing bond strength, and improving the adhesion between the FRP bars and concrete. Because the ends of the SMA fibers are constrained by the concrete, there is a tendency for them to shrink back when the shape memory effect occurs, reducing crack width. This allows for repeated excitation and recovery, giving the concrete a self-healing repair capability. The FRP-reinforced seawater sand concrete structure prepared by this invention enhances durability. The combined use of FRP bars and SMA fibers effectively resists the corrosive effects of chloride ions in the seawater environment, extending the structure's service life. It is also environmentally friendly and energy-saving, utilizing seawater and sea sand as concrete raw materials, conserving freshwater resources, reducing river sand mining, and being ecologically friendly.

Claims

1. A seawater sand concrete structure based on SMA fiber-reinforced FRP bars, characterized in that, It includes seawater sand concrete (2); inside the seawater sand concrete (2) is a pure seawater sand concrete layer and an SMA fiber reinforcement layer located on both sides of the pure seawater sand concrete layer. The SMA fiber reinforcement layer is formed by adding FRP bars (8) and SMA fibers (7) inside the seawater sand concrete.

2. The seawater sand concrete structure based on SMA fiber-reinforced FRP bars according to claim 1, characterized in that, The volume fraction of SMA fibers (7) in the SMA fiber reinforcement layer is 0.2%-0.8%.

3. The seawater sand concrete structure based on SMA fiber-reinforced FRP bars according to claim 1, characterized in that, The FRP reinforcement is made of carbon fiber, glass fiber or aramid fiber reinforced polymer.

4. The seawater sand concrete structure based on SMA fiber-reinforced FRP bars according to claim 1, characterized in that, The seawater and sea sand concrete (2) includes seawater, sea sand, cement, coarse aggregate, mineral admixtures and chemical admixtures, and the component ratio of seawater, sea sand, cement, coarse aggregate, mineral admixtures and chemical admixtures is 37.5:116.25:70:212.5:17.5:

1.

5. The seawater sand concrete structure based on SMA fiber-reinforced FRP bars according to claim 4, characterized in that, The coarse aggregate is gravel, the mineral admixture is fly ash, and the chemical additive is a water-reducing agent.

6. A method for preparing a seawater sand concrete structure based on SMA fiber-reinforced FRP bars according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Pretreatment of SMA fiber (7): The SMA fiber (7) is cleaned and dried, then pre-stretched, and then the two ends of the SMA fiber (7) are bent into a hook shape. Step 2, reinforcement arrangement: Select appropriate FRP reinforcement (8) according to the structural design requirements, and cut and process it according to the design requirements; according to the design requirements, tie and fix the FRP reinforcement (8) in the appropriate position of the template (5), arrange the first partition (10) and the second partition (15) inside the template (5), open holes at the corresponding stirrup positions of the first partition (10) and the second partition (15), and arrange the stirrups (9) that meet the requirements; Step 3: Mix cement, sea sand, seawater, coarse aggregate, and appropriate amounts of mineral admixtures and chemical additives to prepare pure seawater sand concrete; add the pure seawater sand concrete to the SMA fiber (7) treated in Step 1 and mix thoroughly to prepare SMA fiber reinforced concrete. Step 4, Concrete pouring: First, pour the intermediate pure seawater sand concrete, and after it has solidified, pour the SMA fiber reinforced layer (1).

7. The method for preparing seawater sand concrete structure based on SMA fiber reinforced FRP bars according to claim 6, characterized in that, In step three, the cement is silicate cement or sulfoaluminate cement, the mineral admixture is fly ash, and the chemical admixture is a high-efficiency water-reducing agent.

8. The method for preparing seawater sand concrete structure based on SMA fiber reinforced FRP bars according to claim 6, characterized in that, Step four specifically includes the following steps: First, remove the side panel (51) of the template (5). Then, pour the intermediate layer of seawater sand concrete (2) between the first partition (10) and the second partition (15). After pouring, vibrate and compact it. Then, remove the first partition (10) and the second partition (15) respectively and install the side panel (51). Next, place the template (5) with the opening facing upwards on the roller (12). Then, pour the SMA fiber reinforcement layer on one side of the seawater sand concrete (2). After solidification, remove the bottom plate (52) of the template (5). Place the solidified concrete structure on the roller (12). Then, pour the SMA fiber reinforcement layer on the other side of the seawater sand concrete (2). After solidification, remove the bottom plate (52) of the template (5).

9. The method for preparing seawater sand concrete structure based on SMA fiber reinforced FRP bars according to claim 6, characterized in that, The specific steps of pouring the SMA fiber reinforced layer in step four include using several parallel chutes (4) to pour the SMA fiber reinforced layer concrete prepared in step three into the chutes (4), controlling the frequency of the vibrating table (3) to orient the SMA fibers (7) in the template (5), and at the same time, the template (5) located below the chutes (4) controls the length of the telescopic rod (13) through the electric air pump (14) so ​​that the roller (12) moves horizontally and drives the template (5) to move horizontally as a whole.

10. The method for preparing seawater sand concrete structure based on SMA fiber reinforced FRP bars according to claim 9, characterized in that, After the SMA fiber reinforcement layer solidifies in step four, it is heated by a heat gun.

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