A shape memory alloy fiber-based concrete material and a method for manufacturing the same

Abstract

This invention relates to a concrete material based on shape memory alloy fibers and its preparation method, belonging to the field of novel wall material technology. It comprises a concrete matrix and modified SMA fibers dispersed therein. The modified SMA fibers are made by loading a surface treatment agent onto the surface of bent SMA fibers. The surface treatment agent is synthesized from an intermediate through a mercapto-olefin click addition reaction of ethylene dithiol and allyl glycidyl ether, followed by a ring-opening reaction with N-(3-aminopropyl)diethanolamine. After loading the surface treatment agent onto the bent fibers, they are straightened at low temperature. The heat of concrete hydration triggers the fibers to recover their bent shape. The treatment agent selectively accumulates at the fiber bends and promotes in-situ nucleation and growth of C-S-H gel, forming a spatial network reinforcement structure of fiber-hydration products. This invention solves the contradiction between poor workability and insufficient interfacial bonding of bent fibers in existing technologies, significantly improving fiber pull-out work, flexural strength, and crack self-healing ability.

Description

Technical Field

[0001] This invention belongs to the field of novel wall material technology, specifically relating to a concrete material based on shape memory alloy fibers and its preparation method. Background Technology

[0002] Shape memory alloys (SMAs) are smart materials with unique memory properties, capable of recovering their original shape after undergoing significant deformation through heating or unloading. Introducing SMA fibers into concrete matrices can endow traditional concrete structures with intelligent characteristics such as active crack control, self-healing capabilities, and post-earthquake functional recovery, showing broad application prospects in earthquake-resistant structures, bridge engineering, and protective engineering.

[0003] However, existing technologies still face key technical bottlenecks in practical applications, the most critical of which lies in the insufficient interfacial bonding performance between SMA fibers and the concrete matrix. Due to the smooth surface of SMA fibers and the inherent differences in physicochemical properties between metallic and cement-based materials, the stress transfer efficiency between the fibers and the matrix is ​​low, making it difficult to fully utilize the high strength and intelligent response capabilities of SMA materials. Weak areas at the interface often become the starting point for composite material failure.

[0004] To address the aforementioned issues, researchers explored two approaches: physical anchoring and chemical modification. At the physical level, irregularly shaped SMA fibers, such as hooked, crimped, or dog-bone shaped fibers, were used to enhance anchoring force through mechanical interlocking. Studies showed that bent fibers generated higher recovery stress and pull-out resistance than straight fibers. However, irregularly shaped fibers present serious technical drawbacks during concrete mixing: bent fibers are prone to entanglement, leading to uneven fiber distribution, significantly reducing the workability of fresh concrete, and even causing internal defects due to localized fiber clusters. At the chemical modification level, attempts were made to use silane coupling agents for surface treatment to enhance bonding with the concrete matrix, but the effects were limited and far from achieving the designed performance of fiber reinforcement.

[0005] In summary, in existing shape memory alloy fiber reinforced concrete technology, how to retain the excellent anchoring performance of bent fibers while overcoming their poor construction adaptability, and how to achieve active synergy between chemical modifiers and cement hydration process to maximize the interface reinforcement effect, has become a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In order to solve the technical problems mentioned in the background art, the purpose of this invention is to provide a concrete material based on shape memory alloy fiber and a method for preparing the same.

[0007] The objective of this invention can be achieved through the following technical solutions: A concrete material based on shape memory alloy fiber is proposed. Based on the existing concrete system, modified SMA fiber is introduced into the concrete matrix for blending. The preparation process is simple and compatible with traditional construction methods. The modified SMA fiber is made by loading a surface treatment agent onto SMA fiber. The specific preparation method is as follows: Step A1: Under a nitrogen atmosphere, ethylenedithiol, allyl glycidyl ether and acetone are mixed, cooled to below 5°C in an ice-water bath, a photoinitiator is added and mixed well, and then a click addition reaction is carried out by ultraviolet irradiation. After the reaction is completed, the acetone is recovered by rotary evaporation under reduced pressure to obtain the intermediate. Step A2: N-(3-aminopropyl)diethanolamine, boron trifluoride methanol and anhydrous ethanol are mixed and the intermediate is slowly added at room temperature to carry out the ring-opening reaction. After the reaction is completed, the ethanol is recovered by rotary evaporation to obtain the surface treatment agent. Step A3: Mix the surface treatment agent and the ethanol aqueous solution to prepare a bath solution, add the bent SMA fiber, soak it in the surface treatment agent, straighten and cut it at room temperature to obtain the modified SMA fiber.

[0008] Furthermore, the molar ratio of ethylenedithiol to allyl glycidyl ether is 1:2; the ultraviolet irradiation intensity is 20-30 mW / cm². 2 The terminal alkenyl group of allyl glycidyl ether undergoes efficient mercapto-alkene click addition with the dithiol group of ethylene dithiol, introducing a terminal epoxy structure.

[0009] Furthermore, the molar ratio of the intermediate to N-(3-aminopropyl)diethanolamine is 1:2.05-2.1, and the amount of boron trifluoride is 0.2-0.4 wt% of the reaction system; under this reaction system, the active primary amine of N-(3-aminopropyl)diethanolamine undergoes a ring-opening reaction with the terminal epoxy group of the intermediate.

[0010] Furthermore, the concentration of the surface treatment agent in the bath liquid is 1.5-2.2 wt%, and the solid-liquid mass ratio of the bent SMA fiber to the bath liquid is 1:8-12. The disulfide and ether structures in the surface treatment agent molecules form a chelating effect. The bent SMA fiber undergoes plastic deformation at the bending point, resulting in dislocations and distortions in the crystal lattice, and a significant increase in surface energy. Compared with straight fiber filaments, it exposes a large number of active chelating sites at the bending point, thereby enabling the surface treatment agent to chelate and accumulate at the bending point.

[0011] Furthermore, the austenitic completion temperature of the bent SMA fibers is 30-40℃, and they can be restored to the bent state during the hydration and curing process of concrete, thereby restoring the strengthening effect of the bent shape, while maintaining good mixability and workability.

[0012] Furthermore, the modified SMA fiber has a length of 25-40mm and a bending angle of 110-150°; the fiber with this specification has a better overall strengthening effect on strength and toughness in concrete.

[0013] Preferably, the concrete matrix comprises the following components by weight: 400-420 parts cement, 650-680 parts fine aggregate, 1020-1080 parts coarse aggregate, 4.2-5 parts water-reducing agent, and 160-172 parts water, with a volumetric content of 0.55-0.82% modified SMA fiber.

[0014] The method for preparing the concrete material based on shape memory alloy fiber is as follows: the components of the concrete matrix are mixed together, and then modified SMA fibers are added and mixed to obtain the concrete material.

[0015] The beneficial effects of this invention are: The core innovation of this invention lies in: utilizing the physical strengthening characteristics of bent fibers, developing a surface treatment agent to synergistically strengthen them, and constructing a strengthening method of "bent fiber - intelligent surface treatment - temporary straightening - in-situ strengthening". This method not only resolves the inherent contradiction between insufficient interfacial adhesion and deteriorated workability in existing technologies, but also achieves a significant improvement in interfacial enhancement effect, as detailed below: The surface treatment agent is a double-ended epoxy intermediate synthesized from ethylene dithiol and allyl glycidyl ether through a mercapto-olefin click chemical reaction. The thioether bonds in its molecular backbone endow the molecular chain with good flexibility and rotational freedom, enabling it to adaptively spread on the surface of SMA fibers, especially penetrating the micro-grooves and cracks at the bends to form a tight molecular-scale fit. Subsequently introduced N-(3-aminopropyl)diethanolamine is grafted to both ends of the molecular chain through an epoxy ring-opening reaction, forming a unique double-ended diethanolamine structure. After the SMA fibers are mechanically bent, dislocations and distortions are generated in the lattice at the bend, and the surface energy is significantly increased, exposing more active metal atoms. When the bent fibers are immersed in the surface treatment agent solution, the thioether and nitrogen-containing structures in the surface treatment agent molecules form a chelating effect, preferentially binding to the bend areas with higher surface energy, forming a selective distribution pattern of "rich at bends and sparse at straight sections". Subsequently, taking advantage of the SMA material's easy deformation in the martensitic state at low temperature, the surface-treated bent fibers were mechanically straightened at low temperature, temporarily transforming them into a straight shape. During the concrete mixing process, they were less likely to entangle with each other, enabling uniform dispersion in fresh concrete. This avoided the clumping and bridging phenomena common in traditional bent fibers. Furthermore, by utilizing the exothermic characteristics of the hydration reaction, the fibers were automatically triggered to return to their original bent shape. This process requires no additional heating or energy input, and the bending strengthening effect can be restored in the concrete. Modified SMA fibers accumulate surface treatment agents at bends, and the bis(diethanolamine) structure at the molecular ends promotes the formation of CSH gel, thereby constructing a three-dimensional interlocking reinforcement network composed of bent SMA fibers and CSH gel. Unlike existing fiber surface uniform modification technologies, the toughness characteristics of this spatial network reinforcement structure are reflected in its unique energy dissipation mechanism. When the composite material is subjected to load and the fibers tend to be pulled out of the matrix, the network structure at the bend triggers multiple energy dissipation processes: First, the breaking of chemical bonds, including the coordination bonds between the treatment agent and the fiber, and the hydrogen bond network between the treatment agent and CSH; second, the initiation and propagation of microcracks in the CSH gel layer. Due to the presence of the network structure, the crack propagation path is tortuous, and the fracture energy is significantly increased; third, the unlocking of geometric interlocks, as the bending protrusions of the fibers need to "pry open" the hydration product layer covering them in order to be released from the matrix; and finally, the energy dissipation from the elastic or plastic deformation of the fibers themselves. The superposition effect of the three energy dissipation mechanisms significantly improves the pull-out work of the fibers of this invention compared with existing technologies, thereby fully leveraging the reinforcing effect of the fibers.

[0016] Furthermore, this spatial network reinforcement structure transforms the fiber-matrix bond from a simple interfacial adhesion to a three-in-one composite structure of "fiber-network-matrix." This structure exhibits unique response characteristics when subjected to external forces: at low load levels, the network transmits stress through elastic deformation; as the load increases, local microcracks initiate but are confined by undamaged areas within the network, preventing unstable crack propagation; under appropriate conditions, SMA fibers can effectively recover through memory deformation; under ultimate loads, the network delays failure through multiple energy dissipation mechanisms, exhibiting typical "pseudo-ductility" behavior. This toughness characteristic allows the material to absorb a large amount of energy through gradual damage to the internal network when subjected to dynamic loads such as impacts and earthquakes, preventing sudden brittle failure, which is of great value to the safety and durability of engineering structures.

[0017] In summary, this invention induces a locally high-density hydration gel network structure at the fiber bending point by matching the morphological design of the bent fiber with the molecular structure of the surface treatment agent. This network is deeply coupled with the fiber geometry, constructing a spatial toughness-enhancing network, endowing the composite material with a unique energy dissipation mechanism and excellent mechanical properties. Moreover, the process is simple, compatible with traditional concrete construction methods, and has good prospects for engineering applications. Detailed Implementation

[0018] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0019] Example 1: Preparation of a concrete material based on shape memory alloy fibers. The specific implementation process is as follows: 1. Synthesis of surface treatment agents Step A1: Nitrogen gas is introduced into the reactor for protection. 0.1 mol ethylenedithiol, 0.2 mol allyl glycidyl ether, and 150 mL acetone are added and stirred. The mixture is cooled to 3°C using an ice-water bath. Then, 0.4 g of photoinitiator 1173 is added and stirred until homogeneous. A 365 nm ultraviolet light source is then turned on, and the irradiance is adjusted to 30 mW / cm². 2 The reaction was carried out under continuous stirring and nitrogen protection for 1.5 h; after the reaction was completed, the pressure was reduced and the acetone was recovered by rotary evaporation at 40 °C to obtain the intermediate.

[0020] Step A2: Take 0.21 mol N-(3-aminopropyl)diethanolamine, boron trifluoride methanol (boron trifluoride content 45 wt%, measured according to the concentration in the system of 0.4 wt%), 220 mL anhydrous ethanol, add the materials and stir to mix, slowly add 0.1 mol intermediate at room temperature (23±2℃) and control the addition time to 1 h, then continue the reaction for 6 h, and after the reaction is completed, rotary evaporate to recover the ethanol to obtain the surface treatment agent.

[0021] 2. Preparation of modified SMA fibers Step A3: Using Φ0.5mm nickel-titanium alloy wire (model: TNCC, austenitic finishing temperature: 30-40℃) as fiber raw material, a bending machine is used to control the bending angle at 120° and the bending spacing at 5mm. The bent state is then treated at 400℃ for 30 minutes to fix it, thus producing bent SMA fibers. A bath solution is prepared by mixing the surface treatment agent with a 60% volume fraction ethanol aqueous solution, and the concentration of the surface treatment agent in the bath solution is controlled at 2.2wt%. The bent SMA fibers are added to the bath solution, and the solid-liquid mass ratio is controlled at 1:8. After soaking for 6 hours, the fibers are removed and dried. They are then straightened at room temperature using a stretching straightener and cut to a length of 25mm to obtain modified SMA fibers.

[0022] 3. Preparation of concrete materials Ingredients: Concrete base material is prepared according to weight parts, specifically: 410 parts cement (PO 42.5 type), 665 parts fine aggregate (natural river sand, fineness modulus of about 2.6), 1050 parts coarse aggregate (5-16mm continuously graded crushed stone), 4.5 parts water-reducing agent (R-707 type polycarboxylate water-reducing agent) and 166 parts water; modified SMA fiber prepared above is prepared according to a volume dosage of 0.55%.

[0023] Mixing: Cement, fine aggregate, coarse aggregate and water-reducing agent are mixed evenly in a mixer. After adding water, the mixture is stirred for 3 minutes. Then, modified SMA fibers are added and mixed for 5 minutes before being discharged to obtain concrete material.

[0024] Example 2: A concrete material based on shape memory alloy fibers was prepared. The specific implementation process is as follows: 1. Synthesis of surface treatment agents Step A1: Nitrogen gas is introduced into the reactor for protection. 0.1 mol ethylenedithiol, 0.2 mol allyl glycidyl ether, and 200 mL acetone are added and stirred. The mixture is cooled to 3°C using an ice-water bath. 0.6 g of photoinitiator 1173 is then added and stirred until homogeneous. A 365 nm ultraviolet light source is then turned on, and the irradiance is adjusted to 20 mW / cm². 2 The reaction was carried out under continuous stirring and nitrogen protection for 2.5 h; after the reaction was completed, the pressure was reduced and the acetone was recovered by rotary evaporation at 40 °C to obtain the intermediate.

[0025] Step A2: Take 0.205 mol N-(3-aminopropyl)diethanolamine, boron trifluoride methanol (boron trifluoride content 45 wt%, measured according to the concentration in the system as 0.2 wt%), 300 mL anhydrous ethanol, add the materials and stir to mix. Slowly add 0.1 mol intermediate at room temperature (23±2℃) and control the addition time to 1.5 h. Then continue the reaction for 8 h. After the reaction is completed, rotary evaporate to recover the ethanol to obtain the surface treatment agent.

[0026] 2. Preparation of modified SMA fibers Step A3: Using Φ0.5mm nickel-titanium alloy wire (model: TNCC, austenitic finishing temperature: 30-40℃) as fiber raw material, a bending machine is used to control the bending angle at 150° and the bending spacing at 8mm. The bent state is then treated at 400℃ for 30 minutes to fix it, thus producing bent SMA fibers. A bath solution is prepared by mixing the surface treatment agent with a 60% volume fraction ethanol aqueous solution, and the concentration of the surface treatment agent in the bath solution is controlled at 1.5wt%. The bent SMA fibers are added to the bath solution, and the solid-liquid mass ratio is controlled at 1:12. After soaking for 6 hours, the fibers are removed and dried. They are then straightened at room temperature using a stretching straightener and cut into 40mm lengths to obtain modified SMA fibers.

[0027] 3. Preparation of concrete materials Ingredients: Concrete base material is prepared according to weight parts, specifically: 400 parts cement (PO 42.5 type), 650 parts fine aggregate (natural river sand, fineness modulus of about 2.6), 1020 parts coarse aggregate (5-16mm continuously graded crushed stone), 4.2 parts water-reducing agent (R-707 type polycarboxylate water-reducing agent) and 160 parts water; modified SMA fiber prepared above is prepared according to a volume dosage of 0.65%.

[0028] Mixing: Cement, fine aggregate, coarse aggregate and water-reducing agent are mixed evenly in a mixer. After adding water, the mixture is stirred for 3 minutes. Then, modified SMA fibers are added and mixed for 5 minutes before being discharged to obtain concrete material.

[0029] Example 3: A concrete material based on shape memory alloy fibers was prepared. The specific implementation process is as follows: 1. Synthesis of surface treatment agents Step A1: Nitrogen gas is introduced into the reactor for protection. 0.1 mol ethylenedithiol, 0.2 mol allyl glycidyl ether, and 180 mL acetone are added and stirred. The mixture is cooled to 3°C using an ice-water bath. 0.5 g of photoinitiator 1173 is then added and stirred until homogeneous. A 365 nm ultraviolet light source is then turned on, and the irradiance is adjusted to 25 mW / cm². 2 The reaction was carried out under continuous stirring and nitrogen protection for 2 hours; after the reaction was completed, the pressure was reduced and the acetone was recovered by rotary evaporation at 40°C to obtain the intermediate.

[0030] Step A2: Take 0.21 mol N-(3-aminopropyl)diethanolamine, boron trifluoride methanol (boron trifluoride content 45 wt%, measured according to the concentration in the system of 0.3 wt%), 250 mL anhydrous ethanol, add the materials and stir to mix, slowly add 0.1 mol intermediate at room temperature (23±2℃) and control the addition time to 1 h, then continue the reaction for 7 h. After the reaction is completed, rotary evaporate to recover the ethanol to obtain the surface treatment agent.

[0031] 2. Preparation of modified SMA fibers Step A3: Using Φ0.5mm nickel-titanium alloy wire (model: TNCC, austenitic finishing temperature: 30-40℃) as fiber raw material, a bending machine is used to control the bending angle at 130° and the bending spacing at 7mm. The bent state is then treated at 400℃ for 30 minutes to fix it, thus producing bent SMA fibers. A bath solution is prepared by mixing the surface treatment agent with a 60% volume fraction ethanol aqueous solution, and the concentration of the surface treatment agent in the bath solution is controlled at 1.8wt%. The bent SMA fibers are added to the bath solution, and the solid-liquid mass ratio is controlled at 1:10. After soaking for 6 hours, the fibers are removed and dried. They are then straightened at room temperature using a stretching straightener and cut into 30mm lengths to obtain modified SMA fibers.

[0032] 3. Preparation of concrete materials Ingredients: Concrete base material is prepared according to weight parts, specifically: 420 parts cement (PO 42.5 type), 680 parts fine aggregate (natural river sand, fineness modulus of about 2.6), 1080 parts coarse aggregate (5-16mm continuously graded crushed stone), 5 parts water-reducing agent (R-707 type polycarboxylate water-reducing agent) and 172 parts water; modified SMA fiber prepared above is prepared according to a volume dosage of 0.82%.

[0033] Mixing: Cement, fine aggregate, coarse aggregate and water-reducing agent are mixed evenly in a mixer. After adding water, the mixture is stirred for 3 minutes. Then, modified SMA fibers are added and mixed for 5 minutes before being discharged to obtain concrete material.

[0034] Example 4: A concrete material based on shape memory alloy fibers was prepared. The specific implementation process is as follows: 1. Synthesis of surface treatment agents Step A1: Nitrogen gas is introduced into the reactor for protection. 0.1 mol ethylenedithiol, 0.2 mol allyl glycidyl ether, and 150 mL acetone are added and stirred. The mixture is cooled to 3°C using an ice-water bath. 0.5 g of photoinitiator 1173 is then added and stirred until homogeneous. A 365 nm ultraviolet light source is then turned on, and the irradiance is adjusted to 25 mW / cm². 2 The reaction was carried out under continuous stirring and nitrogen protection for 2.2 h; after the reaction was completed, the pressure was reduced and the acetone was recovered by rotary evaporation at 40 °C to obtain the intermediate.

[0035] Step A2: Take 0.21 mol N-(3-aminopropyl)diethanolamine, boron trifluoride methanol (boron trifluoride content 45 wt%, measured according to the concentration in the system of 0.3 wt%), 270 mL anhydrous ethanol, add the materials and stir to mix, slowly add 0.1 mol intermediate at room temperature (23±2℃) and control the addition time to 1.5 h, then continue the reaction for 7 h, and after the reaction is completed, rotary evaporate to recover the ethanol to obtain the surface treatment agent.

[0036] 2. Preparation of modified SMA fibers Step A3: Using Φ0.5mm nickel-titanium alloy wire (model: TNCC, austenitic finishing temperature: 30-40℃) as fiber raw material, a bending machine is used to control the bending angle at 120° and the bending spacing at 8mm. The bent state is then treated at 400℃ for 30 minutes to fix it, thus producing bent SMA fibers. A bath solution is prepared by mixing the surface treatment agent with a 60% volume fraction ethanol aqueous solution, and the concentration of the surface treatment agent in the bath solution is controlled at 2wt%. The bent SMA fibers are added to the bath solution, and the solid-liquid mass ratio is controlled at 1:10. After soaking for 6 hours, the fibers are removed and dried. They are then straightened at room temperature using a stretching straightener and cut to a length of 35mm to obtain modified SMA fibers.

[0037] 3. Preparation of concrete materials Ingredients: Concrete base material is prepared according to weight parts, specifically: 410 parts cement (PO 42.5 type), 670 parts fine aggregate (natural river sand, fineness modulus of about 2.6), 1030 parts coarse aggregate (5-16mm continuously graded crushed stone), 4.5 parts water-reducing agent (R-707 type polycarboxylate water-reducing agent) and 170 parts water; modified SMA fiber prepared above is prepared according to a volume dosage of 0.77%.

[0038] Mixing: Cement, fine aggregate, coarse aggregate and water-reducing agent are mixed evenly in a mixer. After adding water, the mixture is stirred for 3 minutes. Then, modified SMA fibers are added and mixed for 5 minutes before being discharged to obtain concrete material.

[0039] Comparative Example 1 follows the same implementation process as in Example 3, but the bent SMA fibers are used directly without surface treatment agent, and the rest of the implementation process is the same.

[0040] Comparative Example 2: The bent SMA fibers were treated with silane coupling agent KH-550. The specific method was as follows: the silane coupling agent KH-550 and the 30% volume fraction of the ethanol aqueous solution were mixed to prepare a bath solution with a mass fraction of 3wt%. The pH value was adjusted to 5 with hydrochloric acid, and the solid-liquid ratio was controlled to be 1:10. The remaining implementation process was the same as in Example 3.

[0041] The concrete materials prepared above were tested for their workability in accordance with GB / T 50080-2016 standard, as shown in Table 1. Table 1 As can be seen from the test results in Table 1, the fluidity and workability of concrete decreased with the increase of fiber content, but both remained within a suitable range and met the requirements of conventional construction.

[0042] The above concrete material was poured into the mold and compacted. After curing for 24 hours, the concrete was demolded and cured under standard conditions until 28 days of age to prepare specimens. Compressive and flexural strength tests were conducted according to GB / T 50081-2019 standard. A single fiber pull-out test was used, with a fiber embedment length of 15 mm and a loading rate of 0.5 mm / min. The peak pull-out load and pull-out work were detected using a miniature electronic universal testing machine. Details are shown in Table 2. Table 2 As can be seen from the test data in Table 2, the embodiment is significantly better than the comparative example in terms of compressive and flexural mechanical properties. The pull-out test of the single fiber shows that the SMA fiber of the embodiment has a stronger bonding ability with the matrix concrete, indicating that the fiber in the embodiment plays a more effective reinforcing role.

[0043] The above samples were subjected to three-point bending loading until a crack of 0.4 ± 0.05 mm was formed. The samples were then kept at 40℃ for 6 hours and allowed to stand naturally for 28 days. The crack width was measured and the crack closure rate was calculated. Details are shown in Table 3. Table 3 As can be seen from the test data in Table 3, the concrete in the embodiment showed a significantly higher crack closure rate after heat repair than the comparative example, demonstrating excellent crack repair capabilities.

[0044] In the description of this specification, the references to terms such as "an embodiment," "example," "specific example," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0045] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A concrete material based on shape memory alloy fibers, characterized in that, Includes a concrete matrix and modified SMA fibers dispersed in the concrete matrix; The method for preparing the modified SMA fiber is as follows: Step A1: Under a nitrogen atmosphere, ethylenedithiol, allyl glycidyl ether and acetone are mixed, cooled to below 5°C in an ice-water bath, a photoinitiator is added and mixed well, and then a click addition reaction is carried out by ultraviolet irradiation to obtain an intermediate. Step A2: N-(3-aminopropyl)diethanolamine, boron trifluoride methanol and anhydrous ethanol are mixed and slowly added to the intermediate at room temperature to carry out the ring-opening reaction. The surface treatment agent is obtained after treatment. Step A3: Mix the surface treatment agent and the ethanol aqueous solution to prepare a bath solution, add the bent SMA fiber, soak it in the surface treatment agent, straighten and cut it at room temperature to obtain the modified SMA fiber.

2. The concrete material based on shape memory alloy fiber according to claim 1, characterized in that, The molar ratio of ethylenedithiol to allyl glycidyl ether is 1:2; the ultraviolet irradiation intensity is 20-30 mW / cm². 2 .

3. A concrete material based on shape memory alloy fibers according to claim 2, characterized in that, The molar ratio of the intermediate to N-(3-aminopropyl)diethanolamine is 1:2.05-2.1, and the amount of boron trifluoride is 0.2-0.4 wt% of the reaction system.

4. A concrete material based on shape memory alloy fibers according to claim 3, characterized in that, The concentration of the surface treatment agent in the bath solution is 1.5-2.2 wt%, and the solid-liquid mass ratio of the bent SMA fibers to the bath solution is 1:8-12.

5. A concrete material based on shape memory alloy fibers according to claim 1, characterized in that, The austenitic finishing temperature of bent SMA fibers is 30-40℃.

6. A concrete material based on shape memory alloy fibers according to claim 1, characterized in that, The modified SMA fiber has a length of 25-40mm and a bending angle of 110-150°.

7. A concrete material based on shape memory alloy fibers according to claim 1, characterized in that, The weight composition of the concrete matrix is ​​as follows: 400-420 parts cement, 650-680 parts fine aggregate, 1020-1080 parts coarse aggregate, 4.2-5 parts water-reducing agent, and 160-172 parts water; the volume content of modified SMA fiber in the concrete matrix is ​​0.55-0.82%.

8. A method for preparing a concrete material based on shape memory alloy fibers according to any one of claims 1-7, characterized in that, Specifically, the concrete matrix is ​​mixed with its various components, and then modified SMA fibers are added and mixed to obtain the concrete material.

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