A method for surface modification treatment of steel fibers

Abstract

The application belongs to the technical field of building, and discloses a method for modifying the surface of steel fibers, and the specific steps are as follows: step one: dopamine (DA) is dissolved in a tris buffer solution and fully stirred to obtain a DA solution with a specific concentration for standby; step two: a certain mass of steel fibers is soaked in the DA solution for a specific time; step three: the steel fibers after the soaking treatment are taken out and cleaned with clean water; and step four: the cleaned steel fibers are dried to a constant weight and cooled to room temperature for standby. Through the treatment method, DA can be effectively self-polymerized to form polydopamine (PDA), the PDA is attached to the surface of the steel fibers to change the surface properties of the material, the surface roughness of the modified steel fibers is improved, the hydrophilicity is improved, the strength and durability of the concrete are significantly enhanced, the service life of the concrete is prolonged, and the service life cycle maintenance cost of the concrete structure is reduced.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of building technology, in particular to a method for surface modification treatment of steel fiber. BACKGROUND

[0002] The use of concrete has many advantages, but also has some disadvantages, such as poor tensile strength, small fracture strain, etc. Based on the shortcomings of concrete, adding fibers to concrete will overcome the related defects and improve the mechanical properties of concrete. Due to the improved characteristics, steel fiber reinforced concrete (SFRC) is widely used in pavement, bridge, bridge deck. The main purpose of incorporating steel fibers into concrete is to improve performance by increasing the ability to withstand strain. The addition of steel fibers will increase the ductility of concrete after cracking. The stiffness modulus, elastic modulus, tensile strength and other characteristics of steel fibers provide better internal mechanical interlocking. Therefore, SFRC shows better performance under fatigue, impact and pulse load.

[0003] However, adding a large amount of steel fiber to concrete can have some potential drawbacks, making the workability of concrete poor and the cost higher, and the high stiffness of steel fiber can cause voids and honeycombs in the concrete during pouring. In addition, the steel fiber is heavy, and it is easy to sink to the bottom during concrete vibration, resulting in uneven distribution of steel fiber in the concrete, which cannot effectively play its excellent performance. At the same time, the steel fiber lacks reactive groups and hydrophilic groups, and the interface between the steel fiber and the cement matrix is poor. Therefore, extensive research is being conducted around the world to modify the surface physicochemical properties of steel fiber to further improve the interfacial bonding ability between the fiber and the matrix. Make it use the right amount of steel fiber to achieve higher mechanical properties and improve the strength of the structure to prevent structural damage.

[0004] In order to improve the bonding performance between steel fiber and cement matrix and better play the ability of steel fiber, the present application envisages using DA to treat steel fiber, using its self-polymerization to deposit polyphenol functional groups on the surface of steel fiber, improving the hydrophilicity and calcium ion adsorption capacity of steel fiber, thereby improving the bonding force between steel fiber and cement matrix interface and further enhancing the mechanical properties of steel fiber reinforced concrete. SUMMARY

[0005] The present application aims to provide a method for surface modification treatment of steel fiber.

[0006] In order to achieve the above-mentioned purpose, the present application adopts the following technical scheme:

[0007] A kind of steel fiber surface modification treatment method, comprising the following steps: step one: a certain mass DA is dissolved in a certain mass Tris buffer Tris, and is fully stirred, to obtain the DA solution of specific concentration for standby;Step two: a certain mass steel fiber is placed in DA solution and soaks for a specific time;Step three: the steel fiber that the soaking treatment is completed is taken out, and is cleaned using clean water;Step four: after cleaning, the steel fiber is dried to constant weight, and after cooling to room temperature, it is used for standby.

[0008] Preferably, the DA and Tris buffer solution mass ratio in the step one is 1:1000-10:1000.

[0009] Preferably, the purity of DA and Tris in the step one is analytical pure.

[0010] Preferably, the mass ratio of steel fiber and DA solution in the step two is 1:2.

[0011] Preferably, the soaking specific time in the step two is 1-24h.

[0012] Preferably, the drying temperature in the step four is controlled at 60-80 DEG C, and the processing time is 12-24h.

[0013] Preferably, the constant weight judging method in the step five is: the mass of modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01 gram, that is, the steel fiber has been dried to constant weight.

[0014] Preferably, the steel fiber in the step one, two, three and four of the steel fiber surface modification treatment method is flat, end hook and wavy, the length is 8-30mm, the diameter is 0.1-0.4mm, the length-diameter ratio is 50-120, and the tensile strength is greater than or equal to 2800MPa.

[0015] Through the above technical solution, compared with the prior art, the beneficial effects of the present application are as follows:

[0016] The application relates to a method for modifying the surface of steel fibers, DA is an endogenous nitrogen-containing organic compound, can be easily self-polymerized in a weak alkaline aqueous solution, and can generate a highly adhesive polydopamine layer (PDA) on the surface of most substrates; after the steel fibers are modified by the DA solution with a specific concentration, the polydopamine layer can be uniformly deposited on the surface of the steel fibers through a surface coating method, and the interfacial bonding strength between the steel fibers and concrete can be effectively enhanced. Meanwhile, the surface coating process can be carried out at normal temperature and pressure and in a weak alkaline environment, the modification cost of the steel fibers is reduced, the content of the steel fibers in the concrete is reduced under the requirement of target performance, and therefore the production cost of the steel fiber reinforced concrete is reduced, which has important theoretical significance for the development of the steel fiber reinforced concrete. The coating plays a role in improving the bonding performance between the steel fibers and the cement matrix during the formation of the interface microstructure, and the capacity of the steel fibers is better exerted.

[0017] According to GB / T 50081-2002 'Standard for Testing Methods of Mechanical Properties of Ordinary Concrete', the mechanical properties of the benchmark group and the examples are tested under standard test conditions, and the test results show that when the concentration and time jointly act, the compressive strength increases most rapidly in the range of 3.0 parts / L-5.0 parts / L, and the flexural strength increases most in the range of 1.0 parts / L-3.0 parts / L when the modification time of the steel fibers is 6h. The pull-out test is optimal at 5.0 parts / L, and the average bonding strength and pull-out energy are 120.0% and 133.27% higher than those of the unmodified steel fibers. BRIEF DESCRIPTION OF DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description are only embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of the provided drawings.

[0019] Figure 1 is a concrete mix proportion table;

[0020] Figure 2 is a concrete mechanical property table;

[0021] Figure 3 is a pull-out test result table;

[0022] Figure 4 is a pull-out mold schematic diagram;

[0023] Figure 5 is a pull-out loading force-displacement curve diagram of the benchmark group and examples 7-9;

[0024] Figure 6 is a pull-out loading force-displacement curve diagram of the benchmark group, example 8 and example 11.

[0025] Figure 7 This is a schematic diagram of the steel fiber modification process. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] Example 1

[0028] A method for surface modification treatment of steel fibers includes the following steps: Step 1: Weigh 1 part of DA and dissolve it in 1000 parts of Tris buffer solution, and stir thoroughly to obtain a DA solution for later use; Step 2: Immerse 500 parts of steel fibers in the 1000 parts of DA solution for 1 hour; Step 3: Remove the soaked steel fibers and wash them with clean water; Step 4: After washing, dry the steel fibers in an oven at 60°C until constant weight, and cool them to room temperature for later use. Then proceed according to... Figure 1 According to the mixing ratio, the required materials are added to the cement mortar mixing pot in sequence and dry-mixed for 3 minutes. Then, the well-mixed water-reducing agent solution is added and mixing is continued for 3 minutes. The freshly mixed steel fiber mortar is then poured into standard flexural molds (40mm×40mm×160mm) and standard compressive molds (50mm×50mm×50mm), and placed in a constant temperature chamber (95% humidity, 20℃) for curing. The mechanical properties of steel fiber reinforced concrete are shown in [reference needed]. Figure 2 .

[0029] Furthermore, the purity of DA and Tris in step one is analytical grade.

[0030] Furthermore, in step two, the mass ratio of steel fiber to DA solution is 1:2.

[0031] Furthermore, the soaking time in step two is 1 hour.

[0032] Furthermore, in step four, the drying temperature is controlled at 60°C, and the processing time is 24 hours.

[0033] Furthermore, the method for determining constant weight in step four is as follows: the modified steel fiber is weighed every 2 hours until the difference between the last two weights does not exceed 0.01 grams, at which point it can be determined that the steel fiber has been dried to constant weight.

[0034] Further, the steel fiber in the steps one, two, three and four is flat and straight without end hook, the length is 13mm, the diameter is 0.2mm, the length-diameter ratio is 65, and the tensile strength is 2800MPa.

[0035] Example 2

[0036] A method for surface modification treatment of steel fiber, comprising the following steps: step one: 1 part of DA is dissolved in 1000 parts of Tris buffer solution, and is fully stirred to obtain a DA solution for standby; step two: 500 parts of steel fiber is immersed in 1000 parts of the DA solution for 6h; step three: the steel fiber after the soaking treatment is taken out and is cleaned with clean water; step four: the steel fiber after the cleaning is dried to constant weight in an oven at 60℃, and is cooled to room temperature for standby. Subsequently, according to the mixing ratio in the table, the required materials are sequentially added into a cement mortar stirring pot, and are stirred for 3 minutes, then a water reducing agent solution which is uniformly stirred is added and is continuously stirred for 3 minutes, and further the freshly mixed steel fiber mortar is poured into a standard 40mm×40mm×160mm bending mold and a standard 50mm×50mm×50mm compressive mold, and is placed in a constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in the table. Figure 1 Figure 2 .

[0037] Further, the purity of the DA and Tris in the step one is analytical pure.

[0038] Further, the mass ratio of the steel fiber to the DA solution in the step two is 1:2.

[0039] Further, the soaking time in the step two is 6h.

[0040] Further, the drying temperature in the step four is controlled at 60℃, and the treatment time is 24h.

[0041] Further, the judgment method of the constant weight in the step four is that the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01g, and then it is determined that the steel fiber has been dried to constant weight.

[0042] Further, the steel fiber in the steps one, two, three and four is flat and straight without end hook, the length is 13mm, the diameter is 0.2mm, the length-diameter ratio is 65, and the tensile strength is 2800MPa.

[0043] Example 3

[0044] ​A method for surface modification treatment of steel fibers includes the following steps: Step 1: Weigh 1 part of DA and dissolve it in 1000 parts of Tris buffer solution, and stir thoroughly to obtain a DA solution for later use; Step 2: Immerse 500 parts of steel fibers in the 1000 parts of DA solution for 24 hours; Step 3: Remove the soaked steel fibers and wash them with clean water; Step 4: After washing, dry the steel fibers in an oven at 60°C until constant weight, and cool them to room temperature for later use. Then proceed according to... Figure 1 According to the mixing ratio, the required materials are added to the cement mortar mixing pot in sequence and dry-mixed for 3 minutes. Then, the well-mixed water-reducing agent solution is added and mixing is continued for 3 minutes. The freshly mixed steel fiber mortar is then poured into standard flexural molds (40mm×40mm×160mm) and standard compressive molds (50mm×50mm×50mm), and placed in a constant temperature chamber (95% humidity, 20℃) for curing. The mechanical properties of steel fiber reinforced concrete are shown in [reference needed]. Figure 2 .

[0045] Furthermore, the purity of DA and Tris in step one is analytical grade.

[0046] Furthermore, in step two, the mass ratio of steel fiber to DA solution is 1:2.

[0047] Furthermore, the soaking time in step two is 24 hours.

[0048] Furthermore, in step four, the drying temperature is controlled at 60°C, and the processing time is 24 hours.

[0049] Furthermore, the method for determining constant weight in step four is as follows: the modified steel fiber is weighed every 2 hours until the difference between the last two weights does not exceed 0.01 grams, at which point it can be determined that the steel fiber has been dried to constant weight.

[0050] Furthermore, the steel fibers mentioned in steps one, two, three, and four are straight without end hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65, and a tensile strength of 2800MPa.

[0051] Example 4

[0052] A method for surface modification treatment of steel fibers includes the following steps: Step 1: Weigh 3 parts of DA and dissolve it in 1000 parts of Tris buffer solution, and stir thoroughly to obtain a DA solution for later use; Step 2: Immerse 500 parts of steel fibers in the 1000 parts of DA solution for 1 hour; Step 3: Remove the soaked steel fibers and wash them with clean water; Step 4: After washing, dry the steel fibers in an oven at 60°C until constant weight, and cool them to room temperature for later use. Then proceed according to... Figure 1The materials are added into the cement mortar mixer in turn according to the mixing ratio, and stirred for 3 minutes, then the water reducing agent solution is added and stirred for 3 minutes, and the freshly mixed steel fiber mortar is poured into the standard 40mm*40mm*160mm bending mold and the standard 50mm*50mm*50mm compression mold, and placed in the constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in Table 1. Figure 2 .

[0053] Further, the purity of DA and Tris in step one is analytical pure.

[0054] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0055] Further, the soaking time in step two is 1h.

[0056] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24h.

[0057] Further, the method for judging the constant weight in step four is that the weight of the modified steel fiber is measured every 2 hours until the difference between the last two weights is less than 0.01g, and then it is determined that the steel fiber has been dried to a constant weight.

[0058] Further, the steel fiber in steps one, two, three and four is flat and has no hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65, and a tensile strength of 2800MPa.

[0059] Example 5

[0060] A method for surface modification of steel fiber, comprising the following steps: step one: 3 parts of DA are dissolved in 1000 parts of Tris buffer solution and stirred thoroughly to obtain a DA solution for standby; step two: 500 parts of steel fiber are immersed in 1000 parts of DA solution for 6h; step three: the immersed steel fiber is washed with clean water; step four: the washed steel fiber is dried to a constant weight in an oven at 60℃, and cooled to room temperature for standby. Then the steel fiber is mixed with cement, sand, water and other materials according to the mixing ratio to obtain a steel fiber mortar, and the steel fiber mortar is poured into a standard bending mold and a standard compression mold for curing. Figure 1 The materials are added into the cement mortar mixer in turn according to the mixing ratio, and stirred for 3 minutes, then the water reducing agent solution is added and stirred for 3 minutes, and the freshly mixed steel fiber mortar is poured into the standard 40mm*40mm*160mm bending mold and the standard 50mm*50mm*50mm compression mold, and placed in the constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in Table 1. Figure 2 .

[0061] Further, the purity of DA and Tris in step one is analytical pure.

[0062] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0063] Further, the soaking time in step two is 6h.

[0064] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24h.

[0065] Further, the method for determining the constant weight in step four is that the weight of modified steel fiber is measured every 2 hours until the difference between the last two weights is less than 0.01g, which means that the steel fiber has been dried to constant weight.

[0066] Further, the steel fiber in steps one, two, three and four is straight and has no hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65, and a tensile strength of 2800MPa.

[0067] Example 6

[0068] A method for surface modification of steel fiber, comprising the following steps: step one: weigh 3 parts of DA and dissolve in 1000 parts of Tris buffer, and stir thoroughly to obtain a DA solution for standby; step two: immerse 500 parts of steel fiber in 1000 parts of DA solution for 24h; step three: take out the soaked steel fiber and wash with clean water; step four: dry the washed steel fiber in an oven at 60℃ to constant weight, and cool to room temperature for standby. Then, according to the mixing ratio in Figure 1 , the required materials are sequentially added into a cement mortar stirring pot, stirred for 3 minutes, then the water reducing agent solution is added and stirred for another 3 minutes, and the freshly mixed steel fiber mortar is poured into 40mm×40mm×160mm standard bending mold and 50mm×50mm×50mm standard compression mold, and placed in a constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of steel fiber concrete are shown in Figure 2 .

[0069] Further, the purity of DA and Tris in step one is analytical pure.

[0070] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0071] Further, the soaking time in step two is 24h.

[0072] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24h.

[0073] Further, the constant weight judgment method in step four is that the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01 grams, which can determine that the steel fiber has been dried to constant weight.

[0074] Further, the steel fiber in steps one, two, three and four is flat and has no end hook, the length is 13 mm, the diameter is 0.2 mm, the aspect ratio is 65, and the tensile strength is 2800 MPa.

[0075] Example 7

[0076] A method for surface modification treatment of steel fiber, comprising the following steps: step one: weigh 5 parts of DA dissolved in 1000 parts of Tris buffer solution, and stir well to obtain a DA solution for standby; step two: immerse 500 parts of steel fiber in 1000 parts of DA solution for 1 h; step three: take out the steel fiber after soaking treatment, and wash with clean water; step four: dry the steel fiber after washing in an oven at 60℃ to constant weight, and cool to room temperature for standby. Then, according to Figure 1 The required materials are sequentially added into a cement mortar stirring pot, stirred for 3 minutes, then the water reducing agent solution is added and stirred for 3 minutes, and the freshly mixed steel fiber mortar is further injected into 40mm×40mm×160mm standard flexural mold, 50mm×50mm×50mm standard compressive mold and specific pullout mold (as shown in Figure 4 ), and placed in a constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of steel fiber reinforced concrete are shown in Figure 2 、 Figure 3 and Figure 5 .

[0077] Further, the purity of DA and Tris in step one is analytical pure.

[0078] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0079] Further, the soaking time in step two is 1 h.

[0080] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24 h.

[0081] Further, the constant weight judgment method in step four is that the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01 grams, which can determine that the steel fiber has been dried to constant weight.

[0082] Further, the steel fiber in the steps one, two, three and four is flat and straight without end hook, the length is 13mm, the diameter is 0.2mm, the length-diameter ratio is 65, and the tensile strength is 2800Mpa.

[0083] Example 8

[0084] A method for surface modification treatment of steel fiber, comprising the following steps: step one: weighing 5 parts of DA and dissolving in 1000 parts of Tris buffer, and stirring thoroughly to obtain a DA solution for standby; step two: immersing 500 parts of steel fiber in 1000 parts of the DA solution for 6h; step three: taking out the steel fiber after soaking treatment, and washing with clean water; step four: drying the steel fiber after washing in an oven at 60℃ to constant weight, and cooling to room temperature for standby. Subsequently, according to the mixing ratio in the table, the required materials are sequentially added into a cement mortar stirring pot, stirring for 3 minutes, then adding the water reducing agent solution stirred uniformly and continuing to stir for 3 minutes, further pouring the freshly mixed steel fiber mortar into 40mm×40mm×160mm standard flexural mold, 50mm×50mm×50mm standard compressive mold and specific uplift mold (as shown in the table), and placing in a thermostat with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in the table. Figure 1 Figure 4 Figure 2 Figure 3 Figure 5 Figure 6

[0085] Further, the purity of the DA and Tris in the step one is analytical pure.

[0086] Further, the mass ratio of the steel fiber to the DA solution in the step two is 1:2.

[0087] Further, the soaking time in the step two is 6h.

[0088] Further, the drying temperature in the step four is controlled at 60℃, and the treatment time is 24h.

[0089] Further, the judgment method of the constant weight in the step four is that the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01g, that is, the steel fiber has been dried to constant weight.

[0090] Further, the steel fiber in the steps one, two, three and four is flat and straight without end hook, the length is 13mm, the diameter is 0.2mm, the length-diameter ratio is 65, and the tensile strength is 2800Mpa.

[0091] Example 9

[0092] ​​​​​​A method for surface modification treatment of steel fiber, comprising the following steps: step one: weigh 5 parts of DA dissolved in 1000 parts of Tris buffer solution, and stir thoroughly to obtain a DA solution for standby; step two: immerse 500 parts of steel fiber in 1000 parts of the DA solution for 24 hours; step three: take out the steel fiber after soaking treatment, and wash with clean water; step four: dry the washed steel fiber in an oven at 60℃ until constant weight, and cool to room temperature for standby. Then, according to the mixing ratio in Figure 1 , add the required materials into a cement mortar stirring pot in sequence, stir for 3 minutes, then add the uniformly stirred water reducing agent solution and continue to stir for 3 minutes, further pour the freshly mixed steel fiber mortar into 40mm×40mm×160mm standard flexural mold, 50mm×50mm×50mm standard compressive mold and specific uplift mold (as shown in Figure 4 ), and place in a thermostat with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of steel fiber concrete are shown in Figure 2 , Figure 3 and Figure 5 .

[0093] Further, the purity of DA and Tris in step one is analytical pure.

[0094] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0095] Further, the soaking time in step two is 24 hours.

[0096] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24 hours.

[0097] Further, the method for judging constant weight in step four is that the weight of the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01g, which indicates that the steel fiber has been dried to constant weight.

[0098] Further, the steel fiber in steps one, two, three and four is flat and straight without hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65 and a tensile strength of 2800Mpa.

[0099] Example 10

[0100] A method for surface modification treatment of steel fiber, comprising the following steps: step one: 10 parts of DA are dissolved in 1000 parts of Tris buffer solution, and fully stirred to obtain a DA solution for standby; step two: 500 parts of steel fiber are immersed in 1000 parts of the DA solution for 1h; step three: the steel fiber after the immersion treatment is taken out and washed with clean water; step four: the steel fiber after the washing is dried to constant weight in an oven at 60℃, and cooled to room temperature for standby. Subsequently, according to the mixing ratio, the required materials are sequentially added into a cement mortar stirring pot, stirred for 3 minutes, then a water reducing agent solution uniformly stirred is added and continues to be stirred for 3 minutes, and further the freshly mixed steel fiber mortar is injected into a standard 40mm*40mm*160mm bending mold and a standard 50mm*50mm*50mm compression mold, and placed in a constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in Table 1. Figure 1 Table 1 Figure 2 .

[0101] Further, the purity of the DA and Tris in the step one is analytical pure.

[0102] Further, the mass ratio of the steel fiber to the DA solution in the step two is 1:2.

[0103] Further, the specific time for the immersion in the step two is 1h.

[0104] Further, the drying temperature in the step four is controlled at 60℃, and the treatment time is 24h.

[0105] Further, the judgment method for the constant weight in the step four is that the weight of the modified steel fiber is weighed every 2 hours until the difference between the last two weights is not more than 0.01g, and it is determined that the steel fiber has been dried to constant weight.

[0106] Further, the steel fiber in the steps one, two, three and four is flat and straight without hooks, with a length of 13mm, a diameter of 0.2mm, a length-diameter ratio of 65, and a tensile strength of 2800Mpa.

[0107] Example 11

[0108] A method for surface modification treatment of steel fiber, comprising the following steps: step one: 10 parts of DA are dissolved in 1000 parts of Tris buffer solution, and fully stirred to obtain a DA solution for standby; step two: 500 parts of steel fiber are immersed in 1000 parts of the DA solution for 6h; step three: the steel fiber after the immersion treatment is taken out and washed with clean water; step four: the steel fiber after the washing is dried to constant weight in an oven at 60℃, and cooled to room temperature for standby. Subsequently, according to the mixing ratio, the required materials are sequentially added into a cement mortar stirring pot, stirred for 3 minutes, then a water reducing agent solution uniformly stirred is added and continues to be stirred for 3 minutes, and further the freshly mixed steel fiber mortar is injected into a standard 40mm*40mm*160mm bending mold and a standard 50mm*50mm*50mm compression mold, and placed in a constant temperature box with humidity of 95% and temperature of 20℃ for curing. The mechanical properties of the steel fiber concrete are shown in Table 1. Figure 1The materials are added into the cement mortar mixer in the mixing ratio, stirred for 3 minutes, then the water reducing agent solution is added and stirred for another 3 minutes. The freshly mixed steel fiber mortar is poured into the standard 40mm*40mm*160mm flexural mold, 50mm*50mm*50mm compressive mold and specific uplift mold (as shown in Figure 4 The mechanical properties of the steel fiber concrete are shown in Figure 2 、 Figure 3 and Figure 6 .

[0109] Further, the purity of DA and Tris in step one is analytical pure.

[0110] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0111] Further, the soaking time in step two is 6h.

[0112] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24h.

[0113] Further, the method for determining the constant weight in step four is that the weight of the modified steel fiber is measured every 2 hours until the difference between the last two weights is less than 0.01g, which means that the steel fiber has been dried to a constant weight.

[0114] Further, the steel fiber in steps one, two, three and four is flat and has no hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65 and a tensile strength of 2800Mpa.

[0115] Example 12

[0116] A method for surface modification of steel fiber, comprising the following steps: step one: 10 parts of DA are dissolved in 1000 parts of Tris buffer solution and stirred thoroughly to obtain a DA solution for standby; step two: 500 parts of steel fiber are soaked in 1000 parts of DA solution for 24h; step three: the soaked steel fiber is washed with clean water; step four: the washed steel fiber is dried to a constant weight in an oven at 60℃, and then cooled to room temperature for standby. Then, the materials are added into the cement mortar mixer in the mixing ratio, stirred for 3 minutes, then the water reducing agent solution is added and stirred for another 3 minutes. The freshly mixed steel fiber mortar is poured into the standard 40mm*40mm*160mm flexural mold, 50mm*50mm*50mm compressive mold and specific uplift mold (as shown in Figure 1 The mechanical properties of the steel fiber concrete are shown inFigure 2 .

[0117] Further, the purity of DA and Tris in step one is analytical pure.

[0118] Further, the mass ratio of steel fiber to DA solution in step two is 1:2.

[0119] Further, the specific time of soaking in step two is 24h.

[0120] Further, the drying temperature in step four is controlled at 60℃, and the treatment time is 24h.

[0121] Further, the method for determining the constant weight in step four is that the weight of the modified steel fiber is measured every 2 hours until the difference between the last two weights is less than 0.01g, which means that the steel fiber has been dried to a constant weight.

[0122] Further, the steel fiber in steps one, two, three and four is flat and straight without hooks, with a length of 13mm, a diameter of 0.2mm, an aspect ratio of 65, and a tensile strength of 2800Mpa.

[0123] Reference group

[0124] Using untreated steel fiber, the required materials are added into the cement mortar stirring pot according to the mixing ratio in Figure 1 , dry stirring for 3 minutes, then adding the uniformly stirred water reducing agent solution and continuing to stir for 3 minutes, further pouring the freshly mixed steel fiber mortar into the 40mm×40mm×160mm standard flexural mold, 50mm×50mm×50mm standard compressive mold and specific uplift mold (as shown in Figure 4 ), and placing them in a constant temperature oven with a humidity of 95% and a temperature of 20℃ for curing. The mechanical properties of steel fiber reinforced concrete are shown in Figure 2 、 Figure 3 、 Figure 5 and Figure 6 .

[0125] Control group

[0126] According to the mixing ratio in Figure 1 , the required materials are added into the cement mortar stirring pot, dry stirring for 3 minutes, then adding the uniformly stirred water reducing agent solution and continuing to stir for 3 minutes, further pouring the freshly mixed steel fiber mortar into the 40mm×40mm×160mm standard flexural mold and 50mm×50mm×50mm standard compressive mold, and placing them in a constant temperature oven with a humidity of 95% and a temperature of 20℃ for curing. The mechanical properties of steel fiber reinforced concrete are shown in Figure 2 .

[0127] Through the method, the surface of the steel fiber is modified, and according to the Cement Mortar Strength Test Method (ISO Method) (GB / T 17671-2021), a 300KN universal testing machine is used to analyze the compressive strength, pull-out strength and bending strength of a standard size mortar test piece, and the results show that the compressive strength of the embodiment can be up to 55.22Mpa, which is 21.95% higher than that of the comparison group; the pull-out strength can be up to 210.81N·mm, which is 133.27% higher than that of the comparison group; and the bending strength can be up to 19.55Mpa, which is 33.36% higher than that of the comparison group. The results show that the method can effectively improve the roughness of the interface between the steel fiber and the cement, and significantly improve the bonding strength of the interface between the steel fiber and the cement.

[0128] The method can effectively generate PDA from DA self-polymerization, and further deposit PDA on the surface of the steel fiber, improve the hydrophilicity of the steel fiber, improve the secondary hydration reaction degree of the interface between the steel fiber and the cement, improve the interface bonding strength, significantly enhance the strength and durability of the concrete, and has a very positive effect on prolonging the service life of the concrete and reducing the life cycle maintenance cost of the concrete structure.

[0129] In the description of the present specification, the description referring to the terms "one embodiment", "an example", "a specific example" and the like means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the illustrative description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0130] The basic principles, main features and advantages of the present application are shown and described above. It should be understood by those skilled in the art that the present application is not limited by the above embodiments, and the above embodiments and descriptions in the specification are only illustrative of the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application.

Claims

1. A method for surface modification treatment of steel fibers, characterized by, The method comprises the following steps: Step 1: a certain mass of DA is dissolved in a Tris buffer solution and fully stirred to obtain a DA solution with a specific concentration for standby; Step 2: a certain mass of steel fibers is soaked in the DA solution for a specific time; Step 3: the steel fibers after the soaking treatment are taken out and cleaned with clean water; Step 4: the cleaned steel fibers are dried to a constant weight and cooled to room temperature for standby; The mass ratio of DA to the Tris buffer solution in the step 1 is 1:1000-10:1000; The mass ratio of the steel fibers to the DA solution in the step 2 is 1:

2.

2. A method of surface modification treatment of steel fibres according to claim 1, characterised in that, The specific time for the soaking in the step 2 is 1-24h.

3. A method of surface modification of steel fibers according to claim 1, characterized in that, The drying temperature in the step 4 is 60-80℃, and the treatment time is 12-24h.

4. A method of surface modification of steel fibers according to claim 1, characterized in that, The judgment method for the constant weight in the step 4 is that the modified steel fibers are weighed every 2 hours until the difference between the last two weights is not more than 0.01g, and then it is determined that the steel fibers have been dried to a constant weight.

5. The method of surface modification of steel fibers according to claim 1, characterized in that, The steel fibers in the steps 2, 3 and 4 are flat, end-hooked or wavy, with a length of 8-30mm, a diameter of 0.1-0.4mm, a length-diameter ratio of 50-120 and a tensile strength of ≥2800MPa.

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