Self-compacting concrete and preparation method thereof

Abstract

The present invention relates to the field of concrete, and specifically discloses a self-compacting concrete and a preparation method thereof. A self-compacting concrete comprises the following raw materials in parts by weight: 320-370 parts of cement; 800-840 parts of coarse aggregate; 750-780 parts of fine aggregate; 12-19 parts of fiber composition; 55-70 parts of fly ash; 20-35 parts of steel slag powder; 1-3 parts of water reducer; 140-175 parts of water; 8-14 parts of expansion agent; the fiber composition is a mixed fiber of steel fiber and sisal fiber, wherein the weight ratio of the steel fiber to the sisal fiber is (9-13): (3-6). The present application has the effect of suppressing the autogenous shrinkage and plastic shrinkage of self-compacting concrete, reducing the generation of harmful cracks, and improving the strength and impermeability of self-compacting concrete.

Description

Technical Field

[0001] The present invention relates to the technical field of concrete, in particular to self-compacting concrete and a preparation method thereof. Background Art

[0002] Self-compacting concrete (SCC) is a concrete that flows and compacts under its own gravity, completely filling the formwork even with dense rebar, achieving excellent homogeneity and requiring no additional vibration. Due to its high fluidity, excellent filling properties, stability without segregation, simple construction, and rapid pouring, SCC is widely used in large-scale structural concrete and complex-shaped reinforcement projects, such as high-rise buildings, ports, undersea tunnels, and cross-sea bridges.

[0003] When preparing self-compacting concrete, the mix ratio of admixtures, binders and coarse and fine aggregates is designed so that the yield stress of the concrete is reduced to a level sufficient to be overcome by the shear stress generated by its own weight, thereby increasing the fluidity of the concrete and having sufficient plastic viscosity to allow the aggregate to be suspended in the cement slurry without segregation and bleeding problems, forming a dense and uniform cementitious structure.

[0004] Existing self-compacting concrete has a large shrinkage, which mainly includes autogenous shrinkage and plastic shrinkage of concrete. Shrinkage causes harmful cracks in self-compacting concrete, which reduces the strength and impermeability of concrete and affects its durability. Summary of the Invention

[0005] In order to suppress the autogenous shrinkage and plastic shrinkage of self-compacting concrete, reduce the occurrence of harmful cracks, and improve the strength and anti-permeability performance of self-compacting concrete, the present application provides a self-compacting concrete and a preparation method thereof.

[0006] The present application provides a self-compacting concrete and a preparation method thereof using the following technical solutions:

[0007] In a first aspect, the present application discloses a self-compacting concrete comprising the following raw materials in parts by weight:

[0008] 320-370 parts of cement;

[0009] 800-840 parts of coarse aggregate;

[0010] 750-780 parts of fine aggregate;

[0011] 12-19 parts of fiber composition;

[0012] 55-70 parts of fly ash;

[0013] 20-35 parts of steel slag powder;

[0014] 1-3 parts of water reducer;

[0015] 140-175 parts water;

[0016] 8-14 parts of expansion agent;

[0017] The fiber composition is a mixed fiber of steel fiber and sisal fiber, wherein the weight ratio of the steel fiber to the sisal fiber is (9-13):(3-6).

[0018] The above technical solution uses a mixture of steel fiber and sisal fiber to modify concrete. The steel fiber provides reinforcement and toughness, while the sisal fiber has excellent fracture resistance. The synergistic effect of the two helps improve the mechanical strength and crack initiation toughness of concrete, inhibiting the generation and growth of cracks. The use of an expansive agent helps compensate for concrete shrinkage and improve impermeability. The use of fly ash and steel slag powder as admixtures helps to reduce shrinkage and enhance volume stability of self-compacting concrete. The synergistic effect of the fiber mixture, fly ash, and steel slag powder can reduce the generation and growth of harmful cracks and improve the strength and impermeability of self-compacting concrete.

[0019] Optionally, the sisal fiber is modified sisal fiber, and the modified sisal fiber is made of the following raw materials in parts by weight:

[0020] 3-5 parts of sisal fiber;

[0021] 25-35 parts of 15% NaOH solution;

[0022] 4-7 parts of methyl methacrylate;

[0023] 0.2-0.5 parts of cerium ammonium nitrate.

[0024] The above technical scheme is adopted, and alkali + methyl methacrylate are used to modify the sisal fiber to remove impurities such as hemicellulose and lignin in the sisal fiber, enhance the bonding strength between the sisal fiber and the cement matrix and the reinforcement effect on the concrete, which is beneficial to the role of sisal fiber in improving the fracture toughness. The hydrophobicity of the modified sisal fiber is improved by grafting methyl methacrylate, the water exudation phenomenon is weakened, and the anti-seepage performance is improved.

[0025] Optionally, the steel slag powder is modified steel slag powder, which is produced by mixing steel slag and a modifier, pressing and molding, and then calcining at high temperature and magnetic separation. The modifier is composed of silicon dioxide and coal gangue, and the mass ratio of steel slag, silicon dioxide and coal gangue is (7-8):1:(1.8-2.2).

[0026] By adopting the above technical solution, the free calcium oxide in the steel slag will cause the steel slag cement to crack, resulting in poor activity of the steel slag and poor volume stability. By adjusting the chemical composition of the steel slag through the modifier, the content of free calcium oxide can be reduced, and the activity and wear resistance of the modified steel slag powder can be improved, thereby compensating for the shrinkage of concrete and improving the mechanical properties.

[0027] Optionally, the cement is P.O42.5 grade ordinary Portland cement, and the fly ash is selected from one of Grade I fly ash and Grade II fly ash.

[0028] By adopting the above technical solution, the addition of fly ash can better reduce the amount of cement added, thereby further controlling the hydration reaction, reducing the hydration heat, and enhancing the crack resistance of concrete.

[0029] Optionally, the coarse aggregate is continuous grade crushed stone with a particle size of 7-18 mm, and the fine aggregate is river sand with a fineness modulus between 2.2 and 2.5.

[0030] By adopting the above technical solution, the crushed stone has a larger particle size and a larger surface area, thereby increasing the volume of the concrete and stabilizing it; the river sand plays a filling role, reducing the porosity of the concrete and increasing the strength of the concrete.

[0031] Optionally, the water reducer is selected from one of a polycarboxylic acid water reducer and an aliphatic hydroxysulfonate high-efficiency water reducer.

[0032] By adopting the above technical solution, the water reducing agent can reduce the addition of water, lower the water-cement ratio of concrete, and improve the slump of concrete.

[0033] Optionally, the expansion agent is one or more of calcium sulfoaluminate, calcium oxide, and calcium sulfate.

[0034] By adopting the above technical solution, the expansive agent can expand during the hardening process of concrete, compensate for shrinkage, reduce the occurrence of cracks, and improve the anti-seepage performance.

[0035] Optionally, the steel fiber has a fiber diameter of 200-400 μm and a length of 30-40 mm, and the sisal fiber has a fiber diameter of 50-80 μm and a length of 20-25 mm.

[0036] By adopting the above technical solution, the steel fibers and sisal fibers with the above diameters and lengths are selected, which have good dispersion in concrete and better comprehensive performance.

[0037] In a second aspect, the present application discloses a method for preparing self-compacting concrete, comprising the following steps:

[0038] Coarse aggregate, fine aggregate, fiber composition, fly ash, steel slag powder and expansion agent are stirred to form a mixture; cement is added to the mixture and stirred, and then a water reducer and water are added and further stirred to obtain self-compacting concrete.

[0039] By adopting the above technical solution, the preparation method of the self-compacting concrete of the present application is simple and controllable, has strong operability, and the produced concrete has good fluidity and self-compacting properties.

[0040] When the sisal fiber is modified sisal fiber, the modified sisal fiber is prepared by the following steps:

[0041] The sisal fibers were soaked in a 15% by mass NaOH solution for 1-1.5 hours, washed with deionized water until neutral, and then dried in an oven at 90-100° C. for 9-10 hours to obtain alkali-treated sisal fibers.

[0042] Under a nitrogen atmosphere, alkali-treated sisal fiber and methyl methacrylate are placed in an acetone-water mixed solvent with an acetone mass fraction of 20%, and ammonium cerium nitrate is added as an initiator. The reaction is carried out at 45-50°C for 3-4 hours, and the fibers are taken out, washed with deionized water, and dispersed in an oven at 90-100°C for 9-10 hours to obtain modified sisal fibers.

[0043] By adopting the above technical solution, the sisal fiber is first treated with alkali to remove low-molecular impurities, and then methyl methacrylate is used to react with the hydroxyl group of the sisal fiber to achieve the modification of the sisal fiber and improve the interaction between the sisal fiber and the cement substrate.

[0044] In summary, this application has the following beneficial effects:

[0045] 1. Concrete is modified by mixing steel fiber and sisal fiber. Steel fiber strengthens and toughens the concrete, while sisal fiber exhibits excellent fracture resistance. The synergistic effect of these two fibers improves the mechanical strength and crack initiation toughness of concrete, inhibiting the generation and growth of cracks. The use of an expansive agent helps compensate for concrete shrinkage and improve its impermeability. Fly ash and steel slag powder are used as admixtures. The addition of steel slag powder improves shrinkage and volume stability of self-compacting concrete. The synergistic effect of the fiber mixture, fly ash, and steel slag powder reduces the generation and growth of harmful cracks and enhances the strength and impermeability of self-compacting concrete.

[0046] 2. Use alkali + methyl methacrylate to modify the sisal fiber, remove impurities such as hemicellulose and lignin in the sisal fiber, enhance the bonding strength between the sisal fiber and the cement matrix and the reinforcement effect on the concrete, and help the sisal fiber to improve the fracture toughness. By grafting methyl methacrylate, the hydrophobicity of the modified sisal fiber is improved, the water exudation phenomenon is reduced, and the anti-seepage performance is improved. DETAILED DESCRIPTION

[0047] The present application is further described in detail below with reference to the following embodiments and comparative examples.

[0048] The cement used is P.O42.5 grade ordinary Portland cement from Wuhan Yadong Cement;

[0049] The fly ash is grade I fly ash or grade II fly ash, which comes from Hunan Sanlin New Materials Co., Ltd.

[0050] Fine aggregate: river sand, fineness modulus: 2.3;

[0051] Coarse aggregate: Yangxin crushed stone, nominal particle size: 7-18mm;

[0052] Polycarboxylate water reducer was purchased from Wuhan Huaxuan High-tech Co., Ltd., model HX-YZJ01;

[0053] Aliphatic hydroxysulfonate high-efficiency water reducer was purchased from Jiangsu Lianxiong Fine Chemical Technology Co., Ltd.

[0054] The expansion agent was purchased from Wuhan Chenlong New Material Technology Co., Ltd.

[0055] Steel slag powder was purchased from Hebei Angyun Mineral Products Co., Ltd.

[0056] Steel fibers were purchased from a materials company in Hengshui City, Hebei Province, with an average length of 30 mm and an average fiber diameter of 300 μm.

[0057] Sisal fiber was purchased from Hengwei Hemp Products Factory in Changge City, Henan Province, with an average length of 20 mm and an average fiber diameter of 60 μm.

[0058] Preparation Example

[0059] Preparation Example 1

[0060] Modified sisal fiber, composed of the following raw materials:

[0061] 3kg sisal fiber;

[0062] 25 kg of 15% NaOH solution;

[0063] 4 kg of methyl methacrylate;

[0064] 0.2kg of ceric ammonium nitrate.

[0065] Modified sisal fiber is prepared by the following steps:

[0066] The sisal fibers were immersed in a 15% by mass NaOH solution for 1 hour, washed with deionized water 3-4 times until neutral, and then dried in an oven at 90° C. for 9 hours to obtain alkali-treated sisal fibers.

[0067] Under a nitrogen atmosphere, alkali-treated sisal fiber and methyl methacrylate were placed in 30 kg of acetone-water mixed solvent with a mass fraction of 20% acetone, and ammonium cerium nitrate was added as an initiator. The reaction was carried out at 45 ° C for 3 h, and the fiber was taken out and washed with deionized water. The fiber was dispersed and dried in an oven at 90 ° C for 9 h to obtain modified sisal fiber.

[0068] Preparation Example 2

[0069] Modified sisal fiber, composed of the following raw materials:

[0070] 5kg sisal fiber;

[0071] 35 kg of 15% NaOH solution;

[0072] 7 kg of methyl methacrylate;

[0073] 0.5kg of ceric ammonium nitrate.

[0074] Modified sisal fiber is prepared by the following steps:

[0075] The sisal fibers were soaked in a 15% by mass NaOH solution for 1.5 hours, washed with deionized water for 3-4 times until neutral, and then dried in an oven at 100° C. for 10 hours to obtain alkali-treated sisal fibers.

[0076] Under a nitrogen atmosphere, alkali-treated sisal fiber and methyl methacrylate were placed in 40 kg of acetone-water mixed solvent with a mass fraction of 20% acetone, and ammonium cerium nitrate was added as an initiator. The reaction was carried out at 50°C for 4 hours, and the fibers were taken out, washed with deionized water, and dispersed in an oven at 100°C for 10 hours to obtain modified sisal fiber.

[0077] Preparation Example 3

[0078] Modified steel slag powder is composed of the following raw materials:

[0079] 7kg steel slag;

[0080] Modifier: 1kg of silicon dioxide; 1.8kg of coal gangue.

[0081] Modified steel slag powder is prepared by the following steps:

[0082] Add steel slag and modifier into the reactor, heat to 1300℃, and calcine for 20min; then cool to 1100℃ and keep warm for 1.5h. After the end of the heat preservation, take out the steel slag and put it into water for rapid cooling, so that the steel slag is quickly cooled from 1100℃ to room temperature;

[0083] The taken-out steel slag is ground and magnetically separated, and the iron-containing minerals are magnetically separated using a magnetic separation tube to obtain the iron-containing minerals, and the steel slag tailings obtained after magnetic separation are modified steel slag powder.

[0084] Preparation Example 4

[0085] Modified steel slag powder is composed of the following raw materials:

[0086] 8kg steel slag;

[0087] Modifier: 1kg of silicon dioxide; 2.2kg of coal gangue.

[0088] Modified steel slag powder is prepared by the following steps:

[0089] Add steel slag and modifier into the reactor, heat to 1600℃, and calcine for 30min; then cool to 1300℃ and keep warm for 2.5h. After the end of the heat preservation, take out the steel slag and put it into water for rapid cooling, so that the steel slag is quickly cooled from 1300℃ to room temperature;

[0090] The taken-out steel slag is ground and magnetically separated, and the iron-containing minerals are magnetically separated using a magnetic separation tube to obtain the iron-containing minerals, and the steel slag tailings obtained after magnetic separation are modified steel slag powder.

[0091] Example

[0092] Example 1

[0093] 800 kg of crushed stone, 750 kg of river sand, 12 kg of fiber composition, 55 kg of fly ash, 20 kg of steel slag powder and 8 kg of calcium sulfoaluminate expansion agent were added into a concrete mixer for first stirring for 6 minutes. The fiber composition was selected from 9 kg of steel fiber and 3 kg of sisal fiber to obtain a mixture.

[0094] 320 kg of cement was added to the above mixture and stirred for a second time for 3 minutes. Then 1 kg of polycarboxylate water reducer and 140 kg of water were added and stirred for a third time for 1 minute to obtain self-compacting concrete.

[0095] Examples 2-4

[0096] The differences between Examples 2 to 4 and Example 1 are the raw materials, raw material parameters and stirring time, as shown in Table 1.

[0097] In Example 2, 19 kg of the fiber composition is specifically selected from 13 kg of steel fiber and 6 kg of sisal fiber, the expansion agent is selected from calcium oxide expansion agent, and the water reducer is selected from polycarboxylate water reducer;

[0098] In Example 3, 15 kg of the fiber composition is specifically selected from 10 kg of steel fiber and 5 kg of sisal fiber, the expansion agent is a calcium sulfate expansion agent, and the water reducer is an aliphatic hydroxysulfonate high-efficiency water reducer;

[0099] In Example 4, 9 kg of steel fiber and 6 kg of sisal fiber are specifically selected for the 15 kg fiber composition, calcium sulfoaluminate is selected as the expansion agent, and 1 kg of polycarboxylate water reducer and 1 kg of aliphatic hydroxysulfonate high-efficiency water reducer are specifically selected for the 2 kg water reducer.

[0100] Table 1

[0101]

[0102]

[0103] Example 5

[0104] The difference between this embodiment and embodiment 1 is that in the raw materials of the self-compacting concrete, 3 kg of the modified sisal fiber prepared in preparation example 1 is used to replace an equal mass of sisal fiber.

[0105] Example 6

[0106] The difference between this embodiment and embodiment 1 is that in the raw materials of the self-compacting concrete, 3 kg of the modified sisal fiber prepared in preparation example 2 is used instead of an equal mass of sisal fiber.

[0107] Example 7

[0108] The difference between this embodiment and embodiment 1 is that in the raw materials of the self-compacting concrete, 20 kg of the modified steel slag powder prepared in preparation example 3 is used to replace an equal mass of steel slag powder.

[0109] Example 8

[0110] The difference between this embodiment and embodiment 1 is that among the raw materials of the self-compacting concrete, 20 kg of the modified steel slag powder prepared in preparation example 4 is used to replace an equal mass of steel slag powder.

[0111] Example 9

[0112] The difference between this embodiment and embodiment 1 is that in the raw materials of the self-compacting concrete, 3 kg of modified sisal fiber prepared in Preparation Example 2 is used instead of an equal mass of sisal fiber, and 20 kg of modified steel slag powder prepared in Preparation Example 3 is used instead of an equal mass of steel slag powder.

[0113] Example 10

[0114] The difference between this embodiment and embodiment 1 is that in the raw materials of the self-compacting concrete, 3 kg of modified sisal fiber prepared in Preparation Example 1 is used instead of an equal mass of sisal fiber, and 20 kg of modified steel slag powder prepared in Preparation Example 4 is used instead of an equal mass of steel slag powder.

[0115] Comparative Example

[0116] Comparative Example 1

[0117] The difference between this comparative example and Example 1 is that 3 kg of steel fiber is selected to replace the same mass of sisal fiber in the raw materials of the self-compacting concrete.

[0118] Comparative Example 2

[0119] The difference between this comparative example and Example 1 is that 9 kg of sisal fiber is used to replace the same mass of steel fiber in the raw materials of the self-compacting concrete.

[0120] Comparative Example 3

[0121] The difference between this comparative example and Example 1 is that 20 kg of steel slag powder is not added to the raw materials of the self-compacting concrete.

[0122] Performance testing experiments

[0123] The compressive strength, autogenous shrinkage, crack resistance and impermeability of the self-compacting concretes prepared in Examples 1-10 and Comparative Examples 1-3 were tested.

[0124] Compressive strength: According to GB / T 50081-2002, concrete obtained from various embodiments of the present invention and comparative examples was made into test specimens. Each specimen was subjected to a compressive strength test. The compressive strength of the concrete after 28 days of curing was measured. The test results are shown in Table 2.

[0125] Autogenous shrinkage performance: Concrete specimens with a size of 100 mm * 100 mm * 515 mm were sealed with plastic wrap and tested for their autogenous shrinkage using a CABR-NES non-contact shrinkage deformation instrument at (20 ± 2) °C. The test results are shown in Table 2.

[0126] Anti-permeability performance: The water seepage height of concrete was tested according to the step-by-step pressurization method specified in GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete". The sample size penetration pressure was 3.5 MPa and the pressurization time was 48 h. The test results are shown in Table 2.

[0127] Table 2

[0128] Sample Compressive strength (MPa) <![CDATA[Shrinkage ratio (10 -6 m / m)]]> Water seepage height (mm) Example 1 46.7 242 0.28 Example 2 47.3 240 0.28 Example 3 48.1 243 0.27 Example 4 47.6 238 0.26 Example 5 51.9 228 0.20 Example 6 52.2 229 0.21 Example 7 56.3 208 0.24 Example 8 55.8 206 0.22 Example 9 60.4 170 0.17 Example 10 60.8 173 0.16 Comparative Example 1 41.5 562 1.67 Comparative Example 2 35.9 268 0.85 Comparative Example 3 38.6 292 0.54

[0129] As shown in Table 2, the self-compacting concrete of Examples 1-4 uses a mixture of steel fiber and sisal fiber to modify the self-compacting concrete. The mixed fiber can fill the voids inside the concrete, forming an effective bridge effect to limit the expansion of cracks, and improve the fracture toughness and crack initiation toughness of the concrete. The incorporation of steel slag can reduce the porosity of the concrete, improve the adhesion between the aggregate and the paste, and improve the mechanical properties of the concrete. At the same time, the hydrate on the surface of the steel fiber can enhance the adhesion between the matrix and the fiber. The internal fineness of the steel slag is rationally planned to improve the overall dispersibility and compatibility. Therefore, through the synergistic effect of the steel fiber, sisal fiber and steel slag, the self-compacting concrete has excellent compressive strength, while the crack resistance and impermeability are enhanced.

[0130] Compared with Example 1, Example 5-6 uses modified sisal fiber. After alkali treatment and methyl methacrylate grafting, the water resistance of the sisal fiber is improved, small molecular impurities are removed, and the uniform dispersion and adhesion in the cement matrix are improved, which is beneficial for the sisal fiber to exert its crack resistance and impermeability properties.

[0131] Compared with Example 1, Examples 7-8 use modified steel slag powder. The steel slag is modified by silica and coal gangue, which reduces the content of free calcium oxide in the steel slag, increases the activity of the steel slag, reduces the cracking of concrete, and improves the mechanical properties and shrinkage resistance of the concrete.

[0132] Compared to Example 1, Comparative Examples 1 and 2 used steel fiber and sisal fiber, respectively, as raw materials for the self-compacting concrete. The steel fiber was evenly distributed within the concrete matrix, reinforcing it and significantly impacting its compressive strength. The sisal fiber, with its excellent tensile strength, effectively improved the toughness and flexural resistance of the concrete, inhibiting the initiation and development of cracks. The synergistic positive hybrid effect of the steel and sisal fibers resulted in superior overall performance compared to either fiber alone.

[0133] Compared with Example 1, in Comparative Example 3, no steel slag powder was added to the raw materials of the self-compacting concrete. The addition of steel slag powder can enhance the compressive strength, impermeability and flexural strength of the concrete, so the overall performance of Comparative Example 3 is reduced.

[0134] This specific implementation manner is merely an explanation of the present application and is not a limitation of the present application. After reading this specification, those skilled in the art may make non-creative modifications to the specific implementation manner as needed, but as long as they are within the scope of the claims of the present application, they are protected by the patent law.

Claims

1. A self-compacting concrete, characterized in that: The invention comprises the following raw materials in parts by weight: 320-370 parts of cement; 800-840 parts of coarse aggregate; 750-780 parts of fine aggregate; 12-19 parts of fiber composition; 55-70 parts of fly ash; 20-35 parts of steel slag powder; 1-3 parts of water reducer; 140-175 parts water; 8-14 parts of expansion agent; The fiber composition is a mixed fiber of steel fiber and sisal fiber, wherein the weight ratio of the steel fiber to the sisal fiber is (9-13):(3-6); The sisal fiber is modified sisal fiber, and the modified sisal fiber is made of the following raw materials in parts by weight: 3-5 parts of sisal fiber; 25-35 parts of 15% NaOH solution; 4-7 parts of methyl methacrylate; 0.2-0.5 parts of cerium ammonium nitrate; The steel slag powder is modified steel slag powder, which is produced by mixing steel slag and a modifier, pressing and molding, and then calcining at high temperature and magnetic separation. The modifier is composed of silicon dioxide and coal gangue, and the mass ratio of steel slag, silicon dioxide and coal gangue is (7-8):1:(1.8-2.2).

2. The self-compacting concrete according to claim 1, characterized in that: The cement is P.O42.5 grade ordinary Portland cement, and the fly ash is selected from one of grade I fly ash and grade II fly ash.

3. The self-compacting concrete according to claim 1, characterized in that: The coarse aggregate is continuous grade crushed stone with a particle size of 7-18 mm, and the fine aggregate is river sand with a fineness modulus between 2.2 and 2.

5.

4. The self-compacting concrete according to claim 1, characterized in that: The water reducer is selected from one of a polycarboxylic acid water reducer and an aliphatic hydroxysulfonate high-efficiency water reducer.

5. The self-compacting concrete according to claim 1, characterized in that: The expansion agent is selected from one or more of calcium sulfoaluminate, calcium oxide, and calcium sulfate.

6. The self-compacting concrete according to claim 1, characterized in that: The steel fiber has a fiber diameter of 200-400 μm and a length of 30-40 mm, and the sisal fiber has a fiber diameter of 50-80 μm and a length of 20-25 mm.

7. A method for preparing a self-compacting concrete according to any one of claims 1 to 6, characterized in that: The following steps are involved: The coarse aggregate, the fine aggregate, the fiber composition, the fly ash, the steel slag powder and the expansion agent are stirred to form a mixed material; Cement is added to the mixture and stirred, and then a water reducer and water are added and further stirred to obtain self-compacting concrete.

8. The method for preparing self-compacting concrete according to claim 7, characterized in that: When the sisal fiber is modified sisal fiber, the modified sisal fiber is prepared by the following steps: The sisal fibers were soaked in a 15% by mass NaOH solution for 1-1.5 hours, washed with deionized water until neutral, and then dried in an oven at 90-100° C. for 9-10 hours to obtain alkali-treated sisal fibers. Under a nitrogen atmosphere, alkali-treated sisal fiber and methyl methacrylate were placed in an acetone-water mixed solvent with an acetone mass fraction of 20%, and ammonium cerium nitrate was added as an initiator. The reaction was carried out at 45-50°C for 3-4 hours, and the fibers were taken out, washed with deionized water, and dispersed in an oven at 90-100°C for 9-10 hours to obtain modified sisal fiber.

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