Preparation method of concrete with high crack resistance

Abstract

The invention discloses a preparation method of high-crack-resistance concrete, which comprises the following steps: S1, preparing raw materials; S2, preparing dry concrete powder: adding cement, coarse aggregate, fine aggregate, fly ash, silica fume and steel fiber into a stirring tank, and starting vibration stirring equipment until all the components are fully mixed and uniformly dispersed to prepare the dry concrete powder; s3, preparing concrete slurry, namely uniformly dispersing polyacrylonitrile fibers into the dry concrete powder through dispersion equipment; a water reducing agent and water are added into a stirrer to be mixed, and a water reducing agent solution is prepared; adding the water reducing agent solution into the concrete dry powder in batches, and stirring for 2-3 minutes after adding each time; and continuously stirring until the concrete slurry is uniform and free of bubbles, so as to prepare the concrete slurry with high crack resistance. Through the raw material ratio and the preparation method, the crack resistance, durability and mechanical property of the concrete are remarkably improved.

Description

Technical Field

[0001] The invention belongs to the technical field of building concrete, and in particular relates to a method for preparing concrete with high crack resistance. Background Art

[0002] In the field of concrete engineering, cracks are a common quality problem in concrete structures, which not only affects the structural quality of concrete, but also easily leads to reduced structural durability and increased safety hazards. Traditional concrete preparation methods often fail to meet the high requirements of modern engineering for concrete crack resistance.

[0003] Traditional concrete preparation methods usually have the following problems:

[0004] Improper raw materials: The alkalinity of cement is too high and the C3A content is too high, which can easily lead to alkali-aggregate reaction and concrete cracking; the grading of coarse aggregate and fine aggregate is unreasonable, which affects the compactness and mechanical properties of concrete.

[0005] Insufficient use of admixtures: The lack of effective active admixtures and reinforcing fibers makes it difficult to significantly improve the crack resistance and durability of concrete.

[0006] Backward preparation technology: Problems such as uneven mixing and insufficient vibration lead to defects inside the concrete, reducing the mechanical properties and crack resistance of the concrete.

[0007] Difficulty in cost control: The preparation of high-performance concrete is often accompanied by high costs, making it difficult to achieve a balance between economic and social benefits. Summary of the invention

[0008] The purpose of the present invention is to provide a method for preparing concrete with high crack resistance, so as to solve the technical problems of insufficient crack resistance, poor mechanical properties and difficulty in cost control existing in traditional concrete preparation methods.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for preparing high crack resistance concrete comprises the following steps

[0011] S1. Prepare raw materials: weigh the following components by weight:

[0012] Cement: 400-800 parts, choose cement with low alkalinity, specific surface area of ​​300-350m² / kg, and C3A content less than 3%;

[0013] Coarse aggregate: 900-1200 parts, selected from natural crushed stone or pebbles with a continuous gradation of 6-32mm and a void ratio of less than 40%;

[0014] Fine aggregate: 400-600 parts, medium-coarse sand with a fineness modulus of 2.3-3.0;

[0015] Fly ash: 100-300 parts;

[0016] Silica fume: 100-200 parts, with a specific surface area greater than or equal to 15,000 m² / kg and a mass percentage of SiO2 greater than or equal to 85%;

[0017] Water reducing agent: 4-12 parts, choose polycarboxylic acid water reducing agent with water reducing rate greater than 25%;

[0018] Steel fiber: 120-320 parts, choose steel fiber with diameter greater than or equal to 0.1mm;

[0019] Polyacrylonitrile fiber: 8-15 parts, evenly dispersed into the concrete through a dispersing device;

[0020] Expansive agent: When the fly ash content is less than 30%, add calcium sulphoaluminate-calcium oxide expansive agent;

[0021] Water: 160-190 parts, used for mixing and curing concrete;

[0022] S2. Preparation of concrete dry powder:

[0023] Add cement, coarse aggregate, fine aggregate, fly ash, silica fume and steel fiber into a mixing tank, and start the vibration mixing equipment at the same time, set the frequency to 20-30 Hz, and mix for 10-15 minutes until all components are fully mixed and evenly dispersed to obtain dry concrete powder;

[0024] S3. Preparing concrete slurry:

[0025] The polyacrylonitrile fiber is uniformly dispersed into the concrete dry powder through a dispersing device to avoid fiber agglomeration; then a water reducer and water are added into a stirrer and mixed to prepare a water reducer solution; the water reducer solution is then added into the concrete dry powder in batches, and stirred for 2 to 3 minutes after each addition to ensure that the water reducer solution is fully mixed; stirring is continued until the concrete slurry is uniform and free of bubbles, so as to obtain a concrete slurry with high crack resistance.

[0026] As a preferred embodiment of the present invention, it also includes step S4 of forming and curing: placing the concrete slurry in a mold by pouring, and removing the mold to obtain a test piece after the slurry hardens; curing the test piece, and adding an expansion agent as needed during the curing process.

[0027] As a further solution of the present invention, the curing temperature in step S4 is 20±2° C., the humidity is not less than 95%, and the curing time is 28 days.

[0028] As a further solution of the present invention, step S5 is also included: performing performance tests on the cured specimens, including compressive strength tests, flexural strength tests and crack resistance tests, to ensure that the concrete products meet the design requirements.

[0029] As a further solution of the present invention, the specific solution of performing compressive strength test on the specimen in step S5 is as follows:

[0030] The first step is to place the specimen on the pressure plate of the pressure testing machine to ensure that the specimen is centered and the force is evenly distributed;

[0031] The second step is to start the pressure testing machine and apply load at a continuous and uniform speed. The loading speed is determined according to the estimated compressive strength of the specimen and is between 0.3MPa / s and 1.0MPa / s.

[0032] Step 3: Record the maximum load F when the specimen is destroyed;

[0033] Step 4: Calculate the compressive strength fcc of the specimen based on the pressure-bearing area A and the failure load F of the specimen. The formula is: fcc=F / A;

[0034] The arithmetic mean of the measured values ​​of the three specimens is taken as the compressive strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the compressive strength value of the group of specimens.

[0035] As a further solution of the present invention, the specific solution of performing the flexural strength test on the specimen in step S5 is as follows:

[0036] The first step is to place the size specimen on the two movable supports of the flexural strength testing machine to ensure that the specimen is centered and geometrically aligned;

[0037] The second step is to start the testing machine and apply load at a continuous and uniform speed until the specimen breaks;

[0038] Step 3: Record the maximum failure load when the specimen breaks;

[0039] Step 4: Calculate the flexural strength of the specimen according to the span L, section height h and failure load of the specimen. The formula is: flexural strength = failure load / (L×h×0.5);

[0040] The arithmetic mean of the measured values ​​of the three specimens is taken as the flexural strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the flexural strength value of the group of specimens.

[0041] As a further solution of the present invention, the specific solution of performing crack resistance test on the specimen in step S5 is as follows:

[0042] First, tensile test: Place the specimen on a tensile testing machine, subject the specimen to tensile force by increasing the tensile force, observe whether cracks will appear on the specimen, and record the tensile force value when the specimen is damaged;

[0043] Second, indentation test: Use an indentation machine to perform pressure test on the specimen, observe whether cracks appear on the surface of the specimen, and record the indentation depth and load value;

[0044] Third, the crack resistance of concrete is determined based on whether cracks appear in the specimen during tension or compression, as well as the number, width and depth of the cracks. The crack resistance of concrete is evaluated by comparing the crack conditions of different specimens.

[0045] As a further solution of the present invention, the dimensions of the test pieces in the compressive strength test, the flexural strength test and the crack resistance test are all 40 mm×40 mm×160 mm.

[0046] As a preferred embodiment of the present invention, in step S1, the pH value of the low-alkali cement is less than 10.5 to ensure that the risk of alkali-aggregate reaction of the concrete is reduced.

[0047] As a preferred embodiment of the present invention, the dosage of the expansive agent is adjusted according to the specific dosage of fly ash. When the dosage of fly ash is 10% to 20%, the dosage of the expansive agent is 0.5% to 1% of the weight of cement; when the dosage of fly ash is 20% to 30%, the dosage of the expansive agent is 1% to 1.5% of the weight of cement, so as to accurately control the expansion rate and crack resistance of concrete.

[0048] Compared with the prior art, the method for preparing high crack resistance concrete provided by the present invention has the following beneficial effects:

[0049] The present invention significantly improves the crack resistance, durability and mechanical properties of concrete through raw material ratio and optimized preparation process. The specific technical effects are as follows:

[0050] 1. Significantly improve the crack resistance: By selecting cement with low alkalinity and low C3A content, and adding active admixtures and reinforcing fibers such as fly ash, silica fume, steel fiber and polyacrylonitrile fiber, the shrinkage cracks of concrete during the hardening process are effectively reduced and the crack resistance of concrete is improved.

[0051] 2. Enhanced mechanical properties: The optimized selection of coarse aggregate and fine aggregate, as well as the addition of steel fiber, significantly improve the compressive strength, flexural strength and toughness of concrete, making concrete products more durable.

[0052] 3. Improve durability: The use of low-alkalinity cement and silica fume reduces the risk of alkali-aggregate reaction in concrete, while improving the concrete's resistance to chemical erosion and impermeability, thereby extending the service life of concrete.

[0053] 4. Cost control: By adding active admixtures such as fly ash, not only the crack resistance of concrete is improved, but also the cost of concrete is reduced, achieving a win-win situation of economic and social benefits.

[0054] 5. Easy to construct: The addition of polycarboxylic acid water reducer significantly reduces the water consumption of concrete, improves the fluidity and workability of concrete, and makes concrete easy to use. BRIEF DESCRIPTION OF THE DRAWINGS

[0055] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. Obviously, the drawings described below are only examples of the embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0056] Figure 1 is a flow chart of an embodiment of the present invention. DETAILED DESCRIPTION

[0057] In order to make the purpose, technical solution and advantages of the embodiments of the present invention more clear, the embodiments of the present invention are further described in detail in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0058] In the description of the embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "inside", "outside", etc. indicate directions or positional relationships based on the directions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the embodiments of the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific direction, be constructed and operated in a specific direction, and therefore should not be understood as a limitation on the embodiments of the present invention.

[0059] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense. For example, it can be a fixed connection, an integral connection, or a detachable connection; it can be the internal connection of two components; it can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the embodiments of the present invention will be understood based on the specific circumstances.

[0060] See attached Figure 1As shown, a method for preparing high crack resistance concrete according to an embodiment of the present invention comprises the following steps:

[0061] S1. Prepare raw materials: weigh the following components by weight:

[0062] Cement: 400-800 parts. Choose cement with low alkalinity, specific surface area of ​​300-350m² / kg and C3A content less than 3% to ensure that the risk of alkali-aggregate reaction of concrete is reduced, while improving the durability and crack resistance of concrete;

[0063] Coarse aggregate: 900-1200 parts, select natural crushed stone or pebbles with a continuous gradation of 6-32mm and a void ratio of less than 40% to optimize the compactness and mechanical properties of concrete;

[0064] Fine aggregate: 400-600 parts, medium-coarse sand with a fineness modulus of 2.3-3.0 is selected to provide appropriate particle grading and fluidity to ensure the uniformity and workability of concrete;

[0065] Fly ash: 100-300 parts, as an active admixture to improve the crack resistance of concrete and reduce the cost of concrete;

[0066] Silica fume: 100-200 parts, select silica fume with a specific surface area greater than or equal to 15000m² / kg and a mass percentage of SiO2 greater than or equal to 85%, to further improve the crack resistance and durability of concrete;

[0067] Water reducing agent: 4-12 parts, choose polycarboxylic acid water reducing agent with water reducing rate greater than 25% and small shrinkage ratio, reduce water consumption, and improve the strength and crack resistance of concrete;

[0068] Steel fiber: 120-320 parts, choose steel fiber with a diameter greater than or equal to 0.1mm to enhance the crack resistance of concrete;

[0069] Polyacrylonitrile fiber: 8-15 parts, evenly dispersed into concrete through dispersing equipment to improve the early crack resistance of concrete;

[0070] Expansive agent: When the fly ash content is less than 30%, calcium sulfoaluminate-calcium oxide expansive agent is added to improve the crack resistance of concrete;

[0071] Water: 160-190 parts, used for mixing and curing concrete.

[0072] S2. Preparation of concrete dry powder:

[0073] Add cement, coarse aggregate, fine aggregate, fly ash, silica fume and steel fiber into a mixing tank, and start the vibration mixing equipment at the same time, set the frequency to 20-30 Hz, and mix for 10-15 minutes until all components are fully mixed and evenly dispersed to obtain dry concrete powder.

[0074] S3. Preparing concrete slurry:

[0075] The polyacrylonitrile fiber is uniformly dispersed into the concrete dry powder through a dispersing device to avoid fiber agglomeration; a water reducer and water are added into a stirrer and mixed to prepare a water reducer solution; the water reducer solution is then added into the concrete dry powder in batches, and stirred for 2 to 3 minutes after each addition to ensure that the water reducer solution is fully mixed; stirring is continued until the concrete slurry is uniform and free of bubbles, so as to obtain a concrete slurry with high crack resistance.

[0076] Step S4, molding and curing: placing the concrete slurry in a mold by pouring, and removing the mold to obtain a test piece after the slurry hardens; curing the test piece, adding an expansion agent as needed during the curing process, the curing temperature is 20±2°C, the humidity is not less than 95%, and the curing time is 28 days.

[0077] The addition of expansive agent can improve the crack resistance of concrete and reduce cracks caused by shrinkage during the hardening process of concrete, thereby improving the overall quality and reliability of concrete products. The specific amount and time of adding expansive agent should be determined according to the concrete formula and curing conditions.

[0078] Step S5: Performing performance tests on the cured specimens, including compressive strength test, flexural strength test and crack resistance test, to ensure that the concrete products meet the design requirements.

[0079] The specific scheme for performing compressive strength test on the specimen in step S5 is as follows:

[0080] The first step is to place the specimen on the pressure plate of the pressure testing machine to ensure that the specimen is centered and the force is evenly distributed;

[0081] The second step is to start the pressure testing machine and apply load at a continuous and uniform speed. The loading speed is determined according to the estimated compressive strength of the specimen and is between 0.3MPa / s and 1.0MPa / s.

[0082] Step 3: Record the maximum load F when the specimen is destroyed;

[0083] Step 4: Calculate the compressive strength fcc of the specimen based on the bearing area A and failure load F of the specimen. The formula is: fcc=F / A.

[0084] The arithmetic mean of the measured values ​​of the three specimens is taken as the compressive strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the compressive strength value of the group of specimens.

[0085] The specific scheme for performing the flexural strength test on the specimen in step S5 is as follows:

[0086] The first step is to place the size specimen on the two movable supports of the flexural strength testing machine to ensure that the specimen is centered and geometrically aligned;

[0087] The second step is to start the testing machine and apply load at a continuous and uniform speed until the specimen breaks;

[0088] Step 3: Record the maximum failure load when the specimen breaks;

[0089] Step 4: Calculate the flexural strength of the specimen based on the span L, section height h and failure load of the specimen. The formula is: flexural strength = failure load / (L×h×0.5).

[0090] The arithmetic mean of the measured values ​​of the three specimens is taken as the flexural strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the flexural strength value of the group of specimens.

[0091] The specific scheme for performing crack resistance test on the specimen in step S5 is as follows:

[0092] First, tensile test: Place the specimen on a tensile testing machine, subject the specimen to tensile force by increasing the tensile force, observe whether cracks will appear on the specimen, and record the tensile force value when the specimen is damaged;

[0093] Second, indentation test: Use an indentation machine to perform pressure test on the specimen, observe whether cracks appear on the surface of the specimen, and record the indentation depth and load value;

[0094] Third, the crack resistance of concrete is determined based on whether cracks appear in the specimen during tension or compression, as well as the number, width and depth of the cracks. The crack resistance of concrete is evaluated by comparing the crack conditions of different specimens.

[0095] Among them, the size of the specimens in the compressive strength test, flexural strength test and crack resistance test is 40mm×40mm×160mm.

[0096] In step S1, the pH value of the low-alkali cement is less than 10.5 to ensure that the risk of alkali-aggregate reaction of the concrete is reduced.

[0097] The dosage of expansive agent is adjusted according to the specific dosage of fly ash. When the dosage of fly ash is 10%-20%, the dosage of expansive agent is 0.5%-1% of the weight of cement; when the dosage of fly ash is 20%-30%, the dosage of expansive agent is 1%-1.5% of the weight of cement, so as to accurately control the expansion rate and crack resistance of concrete.

[0098] In summary, the embodiments of the present invention significantly improve the crack resistance, durability and mechanical properties of concrete through raw material ratio and optimized preparation process. The specific technical effects are as follows:

[0099] Significantly improve crack resistance: By selecting cement with low alkalinity and low C3A content, and adding active admixtures and reinforcing fibers such as fly ash, silica fume, steel fiber and polyacrylonitrile fiber, the shrinkage cracks of concrete during the hardening process are effectively reduced and the crack resistance of concrete is improved.

[0100] Enhanced mechanical properties: The optimized selection of coarse and fine aggregates and the addition of steel fibers significantly improve the compressive strength, flexural strength and toughness of concrete, making concrete products more durable.

[0101] Improve durability: The use of low-alkali cement and silica fume reduces the risk of alkali-aggregate reaction in concrete, while improving the concrete's resistance to chemical erosion and impermeability, thereby extending the service life of concrete.

[0102] Cost control: By adding active admixtures such as fly ash, not only the crack resistance of concrete is improved, but also the cost of concrete is reduced, achieving a win-win situation of economic and social benefits.

[0103] Easy to construct: The addition of polycarboxylic acid water reducer significantly reduces the water consumption of concrete, improves the fluidity and workability of concrete, and makes the concrete easy to construct and vibrate.

[0104] The above shows and describes the basic principle of the present invention. The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. The above embodiments and descriptions in the specification only illustrate the principle of the present invention. Without departing from the scope of the present invention, any modifications, equivalent substitutions and improvements made within the scope of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing high crack resistance concrete, characterized in that: The following steps are involved: S1. Prepare raw materials: weigh the following components by weight: Cement: 400-800 parts, choose cement with low alkalinity, specific surface area of ​​300-350m² / kg, and C3A content less than 3%; Coarse aggregate: 900-1200 parts, selected from natural crushed stone or pebbles with a continuous gradation of 6-32mm and a void ratio of less than 40%; Fine aggregate: 400-600 parts, medium-coarse sand with a fineness modulus of 2.3-3.0; Fly ash: 100-300 parts; Silica fume: 100-200 parts, with a specific surface area greater than or equal to 15,000 m² / kg and a mass percentage of SiO2 greater than or equal to 85%; Water reducing agent: 4-12 parts, choose polycarboxylic acid water reducing agent with water reducing rate greater than 25%; Steel fiber: 120-320 parts, choose steel fiber with diameter greater than or equal to 0.1mm; Polyacrylonitrile fiber: 8-15 parts, evenly dispersed into the concrete through a dispersing device; Expansive agent: When the fly ash content is less than 30%, add calcium sulphoaluminate-calcium oxide expansive agent; Water: 160-190 parts; S2. Preparation of dry concrete powder: Add cement, coarse aggregate, fine aggregate, fly ash, silica fume and steel fiber into a mixing tank, and start the vibration mixing equipment at the same time, set the frequency to 20-30 Hz, and mix for 10-15 minutes until all components are fully mixed and evenly dispersed to obtain dry concrete powder; S3. Preparing concrete slurry: The polyacrylonitrile fiber is uniformly dispersed into the concrete dry powder through a dispersing device; the water reducer and water are added into a stirrer to mix to prepare a water reducer solution; the water reducer solution is then added into the concrete dry powder in batches, and stirred for 2 to 3 minutes after each addition; Continue stirring until the concrete slurry is uniform and free of bubbles, thereby obtaining a concrete slurry with high crack resistance.

2. The method for preparing a high crack resistance concrete according to claim 1, characterized in that: The method also includes step S4 of forming and curing: placing the concrete slurry in a mold by pouring, and removing the mold to obtain a test piece after the slurry hardens; curing the test piece, and adding an expansion agent during the curing process.

3. The method for preparing a high crack resistance concrete according to claim 2, characterized in that: The curing temperature in step S4 is 20±2° C., the humidity is not less than 95%, and the curing time is 28 days.

4. The method for preparing a high crack resistance concrete according to claim 3, characterized in that: The method further comprises step S5: performing performance tests on the cured specimens, including compressive strength test, flexural strength test and crack resistance test.

5. The method for preparing a high crack resistance concrete according to claim 4, characterized in that: The specific scheme for performing compressive strength test on the specimen in step S5 is as follows: The first step is to place the specimen on the pressure plate of the pressure testing machine, with the specimen centered and evenly stressed; The second step is to start the pressure testing machine and apply load at a continuous and uniform speed. The loading speed is determined according to the estimated compressive strength of the specimen and is between 0.3MPa / s and 1.0MPa / s. Step 3: Record the maximum load F when the specimen is destroyed; Step 4: Calculate the compressive strength fcc of the specimen based on the pressure-bearing area A and the failure load F of the specimen. The formula is: fcc=F / A; The arithmetic mean of the measured values ​​of the three specimens is taken as the compressive strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the compressive strength value of the group of specimens.

6. The method for preparing a high crack resistance concrete according to claim 5, characterized in that: The specific scheme for performing the flexural strength test on the specimen in step S5 is as follows: The first step is to place the size specimen on the two movable supports of the flexural strength testing machine, with the specimen centered and geometrically aligned; The second step is to start the testing machine and apply load at a continuous and uniform speed until the specimen breaks; Step 3: Record the maximum failure load when the specimen breaks; Step 4: Calculate the flexural strength of the specimen according to the span L, section height h and failure load of the specimen. The formula is: flexural strength = failure load / (L×h×0.5); The arithmetic mean of the measured values ​​of the three specimens is taken as the flexural strength value of the group of specimens. If the difference between the maximum or minimum value of the three measured values ​​and the middle value exceeds 15% of the middle value, the maximum and minimum values ​​are eliminated and the middle value is taken as the flexural strength value of the group of specimens.

7. The method for preparing a high crack resistance concrete according to claim 6, characterized in that: The specific scheme for testing the crack resistance of the specimen in step S5 is as follows: First, tensile test: Place the specimen on a tensile testing machine, increase the tensile force to subject the specimen to tensile force, observe whether cracks will appear on the specimen, and record the tensile force value when the specimen is damaged; Second, indentation test: Use an indentation machine to perform pressure test on the specimen, observe whether cracks appear on the surface of the specimen, and record the indentation depth and load value; Third, the crack resistance of concrete is determined based on whether cracks appear in the specimen during tension or compression, as well as the number, width and depth of the cracks. The crack resistance of concrete is evaluated by comparing the crack conditions of different specimens.

8. The method for preparing a high crack resistance concrete according to claim 7, characterized in that: In the compressive strength test, flexural strength test and crack resistance test, the size of the specimens is 40mm×40mm×160mm.

9. The method for preparing a high crack resistance concrete according to claim 1, characterized in that: In step S1, the pH value of the low-alkali cement is less than 10.

5.

10. The method for preparing high crack resistance concrete according to claim 1, characterized in that: The amount of the expansive agent is adjusted according to the specific amount of fly ash. When the fly ash amount is 10% to 20%, the amount of the expansive agent is 0.5% to 1% of the weight of the cement; when the fly ash amount is 20% to 30%, the amount of the expansive agent is 1% to 1.5% of the weight of the cement.

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