Composite concrete, preparation method thereof and repair method after cracking

Abstract

The invention discloses composite concrete, a preparation method thereof and a repair method after cracking, and relates to the technical field of concrete structures, the composite concrete comprises concrete and a plurality of fibers embedded in the concrete, and the fibers are made of temperature memory-based shape memory alloy with initial stress introduced through cold drawing treatment. The method for repairing the cracked composite concrete comprises the following steps: heating the crack, so that the fiber in the concrete near the crack recovers the memory shape, and the crack is promoted to heal. According to the concrete provided by the invention, the fibers which are prepared from the temperature memory type shape memory alloy and are subjected to cold drawing treatment to introduce initial stress are embedded into the concrete, so that when a composite concrete structure has cracks, the fibers can generate a trend of recovering to be before cold drawing deformation by heating the fibers at the cracks; and the structures on the two sides of the crack are closed.

Description

Technical Field

[0001] The invention relates to the technical field of concrete structures, and in particular to a composite concrete and a preparation method thereof, and a repair method after cracking. Background Art

[0002] Concrete slabs, beams, columns and nodes are widely used in bridge engineering due to their economical cost and easy forming. However, ordinary concrete materials have poor crack resistance. Under normal use, concrete structures are prone to cracks, causing permanent damage to the structure and affecting the normal service of the concrete structure. Based on this, a new solution is urgently needed to solve the above problems. Summary of the invention

[0003] The purpose of the present invention is to provide a composite concrete and a preparation method thereof, and a repair method after cracking, so as to solve the problems existing in the above-mentioned prior art and solve the shortcomings of the existing concrete structure of low repair efficiency after cracks and large residual deformation after repair.

[0004] To achieve the above object, the present invention provides the following solutions:

[0005] The invention provides a composite concrete, comprising: concrete and a plurality of fibers embedded in the concrete, wherein the fibers are made of a temperature memory type shape memory alloy introduced with initial stress through cold drawing treatment.

[0006] Preferably, the fiber length is 30 mm to 80 mm.

[0007] Preferably, the fiber portions near both ends contain multiple bending structures.

[0008] Preferably, the fiber dosage is 15kg / m 3 Up to 35kg / m 3 .

[0009] Preferably, a plurality of steel bars are embedded in the concrete.

[0010] The present invention also provides a method for making fibers in the composite concrete as described above, wherein the SMA wire is stretched and rolled thin by a roller in a drawing machine at room temperature, cold-drawn to apply initial stress, with the pre-tensioning strain being 0.2 to 1.0 times the elastic limit strain, and then cut to make the fibers.

[0011] The present invention also provides a method for preparing the composite concrete as described above, wherein the first method comprises: step 1, preparing a portion of concrete slurry;

[0012] Step 2: putting the fiber into the part of concrete slurry and stirring;

[0013] Step 3, putting coarse aggregate and fine aggregate into the part of concrete slurry and stirring;

[0014] Step 4: adding the remaining materials for making the concrete slurry into the portion of the concrete slurry and stirring;

[0015] Step 5: placing steel bars and pouring to form the concrete structure;

[0016] Step 6: Cover the concrete structure with sunscreen and sprinkle water for cooling;

[0017] Solution 2 includes: Step 1: Mixing coarse aggregate and fine aggregate

[0018] Step 2: Add fiber and stir;

[0019] Step 3: Add cement and mix;

[0020] Step 4: Mix water and water reducer and add in two batches while stirring.

[0021] Preferably, in step 1 of scheme 1: 50% of water, cement and water reducer are weighed according to the mass and water-cement ratio, mixed, poured into a mixer and stirred for 3 minutes, and cooled in 20° C. water for 20 minutes to form the part of concrete slurry.

[0022] The present invention also provides a method for repairing cracked composite concrete as described above, wherein the crack is heated to restore the memory shape of the fibers in the concrete near the crack, thereby promoting the healing of the crack.

[0023] Preferably, the crack is subjected to high-frequency electromagnetic heating treatment at the crack opening.

[0024] Compared with the prior art, the present invention has achieved the following technical effects:

[0025] The concrete provided by the present invention is embedded with fibers made of temperature memory shape memory alloy that have been subjected to cold drawing treatment to introduce initial stress. Therefore, when cracks appear in the composite concrete structure, the fibers at the cracks can be heated to produce a tendency to recover to the state before cold drawing deformation, thereby promoting structural closure on both sides of the crack, with high repair efficiency and small residual deformation after repair. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 This is a schematic diagram of the cross-sectional structure of composite concrete in an embodiment of the present invention;

[0028] Figure 2 Schematic diagram of fiber pre-drawing process in an embodiment of the present invention;

[0029] Figure 3 This is a schematic diagram of the repair process in an embodiment of the present invention;

[0030] Reference numerals: 1 - concrete; 2 - steel bars; 3 - fiber. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below with reference to the accompanying drawings and specific embodiments.

[0033] First, some technical terms involved in the embodiments of the present application are introduced.

[0034] Shape memory alloy (SMA) refers to a type of alloy material that returns to its original shape when heated or exposed to light after plastic strain is generated by force. It has been applied in the fields of adaptive wings and artificial muscles.

[0035] To facilitate understanding, some concrete crack repair methods in the related art are used as examples.

[0036] In the related technology, there is the cement pressure grouting method, in which the sealing slurry is usually filled into the gap through a pressure delivery device; and the concrete replacement method, in which the damaged concrete at the crack is slotted and removed and then filled with replacement materials. Although the former repairs the surface morphology of the crack, the deformation caused by the crack is still retained and accumulated, and the residual deformation is difficult to completely eliminate. When the vehicle load is applied, a more severe impact effect will be produced, and damage will occur at the same crack position, which is not conducive to the long-term performance of the structure; the latter belongs to local structural reconstruction, and there are problems such as inconvenient construction and long repair time for detailed cracks. At present, there are also methods of adding steel bars to apply compressive stress and externally attaching steel plates, but additional processing steps such as drilling holes, reinforcing bars or gluing steel plates are still required. For large deformation concrete structure cracks that produce cracks, it is inconvenient to apply closing force.

[0037] In another related technology, the development of self-repairing concrete materials mainly includes microbial method and microcapsule method. The microbial method mainly adds glycerol-sealed bacteria and fungal spores to concrete, and activates microorganisms to carry out biological activities to produce repair materials to fill cracks when cracks occur. The microcapsule method mainly mixes the repair agent and catalyst capsules into concrete, and when cracks occur, the capsules are cracked to release the repair agent to undergo polymerization reaction to fill the cracks. The self-repairing performance of the two is related to the activity of the microorganisms and the residual amount of the repair agent. With long-term use, the self-repairing ability decays over time.

[0038] Therefore, the prevention and repair of concrete cracking diseases are still the key problems faced by the operation and maintenance of concrete structures. Traditional solutions are often based on adding external structural measures to fill the cracks, and the development of the self-healing properties of concrete materials is still relatively small. Based on this, the following embodiments of the present application are proposed.

[0039] like Figure 1 As shown, an embodiment of the present invention provides a composite concrete, comprising: concrete 1 and a plurality of fibers 3 embedded in the concrete 1, wherein the fibers 3 are made of a temperature memory type shape memory alloy that has been subjected to a cold drawing process to introduce initial stress.

[0040] The concrete provided by the present invention is embedded with fibers 3 made of temperature memory shape memory alloy that have been subjected to cold drawing treatment to introduce initial stress. Therefore, when cracks appear in the composite concrete structure, the fibers 3 at the cracks can be heated to produce a tendency to recover to the state before cold drawing deformation, thereby promoting structural closure on both sides of the crack, with high repair efficiency and small residual deformation after repair.

[0041] In addition, the fiber 3 itself acts as an admixture to improve the crack toughness of the concrete 1 and increase the cracking load.

[0042] The present invention can complete the fiber 3 processing and composite concrete preparation in a factory, which is conducive to assembly.

[0043] In some embodiments, the fibers 3 in the concrete 1 are randomly distributed, that is, the distribution positions and directions of the fibers 3 are random, so that fibers 3 are present in cracks in any direction, thereby making the method for repairing cracked composite concrete in the following embodiments applicable to cracks in any direction and at any position.

[0044] In some embodiments, the length of the fiber 3 is 30 mm to 80 mm, and can be 30 mm, 50 mm, or 80 mm.

[0045] In some embodiments, the portions of the fiber 3 near both ends contain multiple bending structures. As shown in the figure, there are two bending structures in this embodiment, and the bending structures at both ends of this embodiment are bent toward the same side. Of course, in other embodiments, the bending structures at both ends can be bent toward both sides respectively.

[0046] The present invention can improve the anchoring ability of the fiber 3 inside the concrete 1 structure.

[0047] In some embodiments, the amount of fiber 3 is 15 kg / m 3 Up to 35kg / m 3 , that is, there are 15kg to 35kg of fiber 3 in 1 cubic meter of concrete 1 structure.

[0048] In some embodiments, a plurality of steel bars 2 are embedded in the concrete 1 .

[0049] In this embodiment, the strength of the concrete 1 structure is further improved by providing steel bars 2 .

[0050] like Figure 2 As shown, the present invention also provides a method for making fibers in the composite concrete described in the above embodiment, wherein the SMA wire is stretched and rolled by a roller in a drawing machine at room temperature, cold-drawn to apply initial stress, and the pre-tensioning strain is 0.2 to 1.0 times the elastic limit strain, and then cut into fibers 3.

[0051] Specifically, Figure 2 As shown, an SMA steel wire with a diameter of 0.8 mm is fixed on a processing table and pre-stretched at room temperature with a pre-stretching strain of 0.8 times the elastic limit strain. The wire is bent using a pinch roller and then cut using a rotary tool to produce a fiber 3 with an initial length of 50 mm and a cross-sectional diameter of 0.3 mm. After the shape of the fiber 3 is fixed, the fiber 3 is removed for use.

[0052] The present invention also provides a method for preparing the composite concrete described in the above embodiment, wherein the first method comprises: step 1, preparing a portion of concrete slurry;

[0053] Step 2: putting the fiber into the part of concrete slurry and stirring;

[0054] Step 3, putting coarse aggregate and fine aggregate into the part of concrete slurry and stirring;

[0055] Step 4: adding the remaining materials for making the concrete slurry into the portion of the concrete slurry and stirring;

[0056] Step 5: placing steel bars and pouring to form the concrete structure;

[0057] Step 6: Cover the concrete structure with sunscreen and sprinkle water for cooling;

[0058] Solution 2 includes: Step 1: Mixing coarse aggregate and fine aggregate

[0059] Step 2: Add fiber and stir;

[0060] Step 3: Add cement and mix;

[0061] Step 4: Mix water and water reducer and add in two batches while stirring.

[0062] Specifically, in step 1 of scheme 1: 50% of water, cement and water reducing agent are weighed according to the mass and water-cement ratio, mixed, poured into a mixer and stirred for 3 minutes, and cooled in 20° C. water for 20 minutes to form a portion of concrete slurry.

[0063] like Figure 3 As shown, the present invention also provides a method for repairing cracked composite concrete as described in the above embodiment, wherein the crack is heated to restore the memory shape of the fibers 3 in the concrete 1 near the crack, thereby promoting the healing of the crack.

[0064] In this embodiment, the restoring force of the fiber 3 forms a bending moment in the opposite direction to the cracking load, thereby achieving the application of crack closing stress.

[0065] In some embodiments, the crack is subjected to high-frequency electromagnetic heating treatment at the crack opening. Preferably, the crack is repaired by using a handheld high-frequency electromagnetic induction heater to stimulate the fiber to deform and recover.

[0066] In this embodiment, the restoring force of the fiber 3 along the crack direction generates a closed stress field along the entire length. The temperature of the fiber 3 is high at the crack opening, and the temperature of the fiber 3 near the crack tip is relatively low. The closer to the large deformation position, the greater the closing force, which is conducive to eliminating cracking deformation, reducing residual deformation, and preventing damage accumulation.

[0067] In addition, the equipment required for the repair method provided by the embodiment of the present invention is small in size and portable, and can be inspected and repaired immediately, and is suitable for repairing fine cracks such as chamfers, notches, and joints that are inconvenient to construct.

[0068] The embodiment of the present invention has a fast repair time and high restoring force. The repair performance is only related to the shape memory effect. The fiber 3 completely recovers the deformation and the self-repair does not decay with time, so that the structure can be used repeatedly for a long time.

[0069] The present invention uses specific examples to illustrate the principles and implementation methods of the present invention. The above examples are only used to help understand the method and core ideas of the present invention. At the same time, for those skilled in the art, according to the ideas of the present invention, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the present invention.

Claims

1. A composite concrete, Features: include: Concrete and a plurality of fibers embedded in the concrete, wherein the fibers are made of a temperature memory type shape memory alloy introduced with initial stress through cold drawing.

2. The composite concrete according to claim 1, Features: The fiber length is 30 mm to 80 mm.

3. The composite concrete according to claim 1, Features: The fiber parts near both ends contain multiple bending structures.

4. The composite concrete according to claim 1, Features: The fiber dosage is 15kg / m 3 Up to 35kg / m 3 .

5. The composite concrete according to claim 1, Features: A plurality of steel bars are embedded in the concrete.

6. A method for producing fibers in composite concrete according to any one of claims 1 to 5, Features: The SMA wire is stretched and rolled by rollers in a drawing machine at room temperature, cold-drawn to apply initial stress, with a pre-tension strain of 0.2 to 1.0 times the elastic limit strain, and then cut to form the fiber.

7. A method for preparing the composite concrete according to any one of claims 1 to 5, Features: The first solution comprises: step 1, preparing a portion of concrete slurry; Step 2: putting the fiber into the part of concrete slurry and stirring; Step 3, putting coarse aggregate and fine aggregate into the part of concrete slurry and stirring; Step 4: adding the remaining materials for making the concrete slurry into the portion of the concrete slurry and stirring; Step 5: placing steel bars and pouring to form the concrete structure; Step 6: Cover the concrete structure with sunscreen and sprinkle water for cooling; Solution 2 includes: Step 1: Mixing coarse aggregate and fine aggregate Step 2: Add fiber and stir; Step 3: Add cement and mix; Step 4: Mix water and water reducer and add in two batches while stirring.

8. The method for preparing composite concrete according to claim 7, Features: In step 1 of the scheme 1: 50% of water, cement and water reducing agent are weighed according to the mass and water-cement ratio, mixed, poured into a mixer and stirred for 3 minutes, and cooled in 20° C. water for 20 minutes to form the part of concrete slurry.

9. A method for repairing cracked composite concrete according to any one of claims 1 to 5, Features: The cracks are heated to restore the memory shape of the fibers in the concrete near the cracks, thus promoting the healing of the cracks.

10. The method for repairing cracked composite concrete according to claim 9, Features: The crack is subjected to high-frequency electromagnetic heating treatment at the crack opening.

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