Ultra-high performance concrete based on MnSO4-modified white rice husk ash, its preparation method and application

Abstract

The present application relates to the technical field of building materials, in particular to a kind of super high performance concrete based on MnSO4 modified white rice hull ash and its preparation method and application.In the present application, MnSO4 modified white rice hull ash is used to replace quartz powder, and together with cement, silica fume, fine aggregate river sand, coarse aggregate basalt, steel fiber, water and water reducing agent, a kind of super high performance concrete with super high strength, toughness and high anti-shrinkage capacity is formed.The super high performance concrete based on MnSO4 modified white rice hull ash provided by the present application meets the requirements for UC100 strength grade concrete in GB / T45594-2025 "Test Method for Performance of Non-load-bearing Components of Ultra-high Performance Concrete", and in addition, its self-shrinkage performance is less than 0.005% at 7d, less than 0.02% at 28d and less than 0.04% at 91d.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an ultra-high performance concrete based on MnSO4-modified white rice husk ash, its preparation method, and its application. Background Technology

[0002] Concrete has the advantages of readily available raw materials, low production costs, and convenient processing, and is therefore widely used in various fields. In the past two decades, concrete technology has made significant progress in development and application. However, as people's demands for modern construction technology continue to rise, ordinary concrete, as a commonly used building material, can no longer meet these needs.

[0003] The development trend of concrete technology is toward high strength and high durability. However, ultra-high performance concrete, high-strength concrete and high-strength mortar all use low water-cement ratio. Although they have the characteristics of high strength and high durability, the low water-cement ratio also brings problems such as large autogenous shrinkage. This has become the main problem restricting the application of ultra-high performance concrete, high-strength concrete and high-strength mortar.

[0004] Rice husks are considered a source of biomass and are used as fuel in power plants to generate electricity or steam. After rice husks are burned, about 20% of the original weight of the fuel is retained as rice husk ash. Therefore, the proper treatment and utilization of rice husk ash has attracted increasing attention in the industrial sector. Summary of the Invention

[0005] To overcome the above problems, this invention provides an ultra-high performance concrete based on MnSO4-modified white rice husk ash, its preparation method, and its application.

[0006] To achieve the above technical objectives, the present invention adopts the following technical solution:

[0007] In a first aspect, the present invention provides an ultra-high performance concrete based on MnSO4-modified white rice husk ash, wherein the raw materials comprise by weight:

[0008] 400-500 parts cement, 40-50 parts silica fume, 150-200 parts MnSO4-modified white rice husk ash, 600-800 parts fine aggregate, 1000-1200 parts coarse aggregate, 30-50 parts steel fiber, 120-150 parts water, and 5-8 parts water-reducing agent.

[0009] In one or more embodiments, the cement comprises silicate cement with a strength grade of 52.5 or 52.5R.

[0010] In one or more embodiments, the mass fraction of SiO2 in the silica fume is not less than 95%, and the pozzolanic activity index is greater than 95%.

[0011] In one or more embodiments, the specific surface area of ​​the silica fume is greater than 21.0 m². 2 / g, density is 2.10~2.30 g / cm³ 3 The preferred value is 2.20 g / cm³. 3 .

[0012] In one or more embodiments, the MnSO4-modified white rice husk ash is based on SiO2 and doped with Mn, with Mn forming Mn-O-Si coordination bonds with SiO2.

[0013] In one or more embodiments, the method for preparing the MnSO4-modified white rice husk ash includes the following steps:

[0014] Rice husks were heat-treated with MnSO4 to obtain MnSO4-modified white rice husk ash;

[0015] The heat treatment temperature is 650~700℃.

[0016] Preferably, the heat treatment time is 1.5~2.5 h;

[0017] The mass ratio of rice husk to MnSO4 was (99.8~99.85):0.2.

[0018] In one or more embodiments, the average particle size of the MnSO4-modified white rice husk ash is 5-25 μm; the density is 0.3-0.5 g / cm³. 3 .

[0019] In one or more embodiments, the fine aggregate is river sand with a maximum particle size of 4.5 to 5 mm, preferably 4.75 mm.

[0020] In one or more embodiments, the coarse aggregate is basalt with a maximum particle size of 9-11 mm, preferably 10 mm.

[0021] In one or more embodiments, the steel fibers comprise straight brass-galvanized steel fibers.

[0022] Preferably, the straight brass-galvanized steel fiber has a length of 13 mm, a diameter of 0.16 mm, a tensile strength greater than 2500 MPa, an elastic modulus of 200 GPa, and a density of 7.8 g / cm³. 3 .

[0023] In one or more embodiments, the water-reducing agent includes a polycarboxylate-based high-performance water-reducing agent.

[0024] A second aspect of the present invention provides a method for preparing ultra-high performance concrete based on MnSO4-modified white rice husk ash as described in the first aspect, comprising the following steps:

[0025] S1. After mixing cement, silica fume, MnSO4-modified white rice husk ash, fine aggregate and coarse aggregate evenly, add water and water-reducing agent and mix evenly again to obtain a mixed slurry.

[0026] S2. Add steel fibers to the mixed slurry and mix evenly to obtain ultra-high performance concrete based on MnSO4 modified white rice husk ash.

[0027] In one or more embodiments, in S1, cement, silica fume, MnSO4-modified white rice husk ash, fine aggregate and coarse aggregate are mixed evenly by stirring.

[0028] Preferably, the stirring speed is 75~85 rpm and the stirring time is 2~3 min.

[0029] In one or more embodiments, in S1, water and water-reducing agent are added and mixed evenly again by stirring;

[0030] Preferably, the stirring speed is 75~85 rpm and the stirring time is 2~5 min.

[0031] In one or more embodiments, in S2, steel fibers are added to the mixed slurry and mixed evenly by stirring.

[0032] Preferably, the stirring speed is 155~165 rpm and the stirring time is 3~6 min.

[0033] A third aspect of the present invention provides the application of the ultra-high performance concrete based on MnSO4-modified white rice husk ash described in the first aspect or the ultra-high performance concrete based on MnSO4-modified white rice husk ash prepared by the preparation method described in the second aspect in building materials.

[0034] The beneficial effects of this invention are as follows:

[0035] (1) In this invention, MnSO4-modified white rice husk ash is used to replace quartz powder, and together with cement, silica fume, fine aggregate river sand, coarse aggregate basalt, steel fiber, water, and water-reducing agent, it forms an ultra-high performance concrete with extremely high strength, toughness, and high shrinkage resistance. The ultra-high performance concrete based on MnSO4-modified white rice husk ash provided by this invention meets the requirements for UC100 strength grade concrete in GB / T45594-2025 "Test Method for Performance of Non-load-bearing Members of Ultra-high Performance Concrete". In addition, its autogenous shrinkage is less than 0.005% at 7 days, less than 0.02% at 28 days, and less than 0.04% at 91 days.

[0036] (2) Reasons for the improved compressive and flexural strength of ultra-high performance concrete based on MnSO4-modified white rice husk ash: ① White rice husk ash contains nanoscale pores formed by the non-dense arrangement and mutual adhesion of silicon ions in a gel state, which can optimize the microstructure of the ultra-high performance concrete matrix, reduce harmful pores and macropores in the ultra-high performance concrete matrix, increase gel pores, etc., thereby enhancing the density of ultra-high performance concrete and thus improving compressive and flexural strength. ② The main component of white rice husk ash is SiO2, which has good pozzolanic activity and can form dense CSH gel, enhancing the integrity of ultra-high performance concrete (UHPC). ③ MnSO4-modified white rice husk ash contains Mn 2+ It can adsorb onto the surface of tricalcium silicate (C3S), reducing the activation energy of the hydration reaction, thereby increasing the amount of CSH hydration colloids in concrete and strengthening the calcium-silicon skeleton structure, thus improving compressive and flexural strength. ④ Mn forms Mn-O-Si coordination bonds with SiO2, resulting in stronger van der Waals forces between molecules, thereby improving the overall compressive and flexural strength of concrete materials.

[0037] (3) Reasons for reduced autogenous shrinkage in ultra-high performance concrete based on MnSO4-modified white rice husk ash: After cement hydration, a large amount of calcium hydroxide is generated. When external sulfate ions penetrate into the pore solution, they react with calcium hydroxide to form gypsum. The gypsum then reacts with hydrated calcium aluminate in the cement to form ettringite, which causes an expansion effect. Therefore, the expansion effect after adding an appropriate amount of MnSO4 modification will offset part of the autogenous shrinkage, thereby reducing autogenous shrinkage. In addition, the hydration reaction of MnSO4-modified white rice husk ash as an expansion agent occurs almost simultaneously with the hydration reaction of cement. The expansion force generated by MnSO4-modified white rice husk ash offsets the tensile stress generated by capillary shrinkage. If the dosage of MnSO4-modified white rice husk ash is appropriate, the net deformation of the concrete can be close to zero, or only a very small shrinkage will occur. In the process of filling the pores, the expanding crystals not only compensate for shrinkage, but also block the capillary channels, improving the density and impermeability of the concrete.

[0038] (4) The reason why ultra-high performance concrete based on MnSO4-modified white rice husk ash has excellent chloride ion resistance is that the particles of rice husk ash are very fine, which can fill the tiny pores in the cement paste, making the internal structure of the concrete more compact, thereby physically hindering the penetration channels of chloride ions. Rice husk ash can react with calcium hydroxide produced by cement hydration to generate additional hydrated calcium silicate gel. This gel can not only further compact the structure, but also improve the interface transition zone between the paste and aggregate in the concrete. MnSO4, as an admixture, affects the cement hydration process, thereby improving the ion concentration and conductivity of the pore solution. Attached Figure Description

[0039] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0040] Figure 1 A schematic diagram showing the temperature changes over time at each stage of the preparation process of MnSO4-modified white rice husk ash. Detailed Implementation

[0041] It should be noted that the following detailed descriptions are exemplary and intended to provide further illustration of the invention. Unless otherwise specified, all technical and scientific terms used in this invention have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0042] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0043] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0044] The components of cement, silica fume, and quartz powder in the following examples are shown in Table 1.

[0045] Table 1. Composition of cement, silica fume, and quartz powder

[0046]

[0047] The fine aggregate is river sand with a maximum particle size of 4.75 mm;

[0048] The coarse aggregate is basalt with a maximum particle size of 10 mm.

[0049] The steel fibers are straight, galvanized brass fibers, 13 mm in length, 0.16 mm in diameter, with a tensile strength greater than 2500 MPa, an elastic modulus of 200 GPa, and a density of 7.8 g / cm³. 3 .

[0050] The water-reducing agent is a polycarboxylate-based high-performance water-reducing agent.

[0051] Example 1

[0052] Preparation method of MnSO4 modified white rice husk ash:

[0053] The residual moisture in the rice husks was removed using a dryer. The dried rice husks were then heated to 680℃ at a rate of 2℃ / min, and MnSO4 powder was uniformly added. The mass ratio of rice husks to MnSO4 powder was 49.9:0.1. The mixture was heat-treated at 680℃ for 2 hours to ensure sufficient contact and reaction between the rice husk ash and MnSO4, completing the modification. Finally, the mixture was cooled to room temperature at a rate of 2℃ / min. A schematic diagram showing the temperature changes over time at each stage of the heat treatment process is shown below. Figure 1 As shown.

[0054] The calcined sample was ball-milled to obtain MnSO4-modified white rice husk ash with a density of 350 kg / m³. 3 Specific surface area 450 m² 2 / g, with a particle size of 5~25 μm.

[0055] Comparative Example 1

[0056] Compared with Example 1, the dried rice husks were heated to 500°C at a rate of 2°C / min and then MnSO4 powder was added uniformly. Other conditions were the same as in Example 1 to obtain modified white rice husk ash.

[0057] Comparative Example 2

[0058] Compared with Example 1, dried rice husks were heated to 900°C at a rate of 2°C / min and then MnSO4 powder was added uniformly. Other conditions were the same as in Example 1 to obtain modified white rice husk ash.

[0059] Comparative Example 3

[0060] Compared with Example 1, the mass ratio of rice husk to MnSO4 powder was adjusted to 99.7:0.3, and other conditions were the same as in Example 1, to obtain modified white rice husk ash.

[0061] Comparative Example 4

[0062] Compared with Example 1, the mass ratio of rice husk to MnSO4 powder was adjusted to 99.95:0.05, and other conditions were the same as in Example 1, to obtain modified white rice husk ash.

[0063] Comparative Example 5

[0064] Compared with Example 1, no MnSO4 powder was added, and other conditions were the same as in Example 1, resulting in white rice husk ash.

[0065] Example 2

[0066] An ultra-high performance concrete based on MnSO4-modified white rice husk ash comprises the following raw materials by weight: 450 parts of 52.5R grade ordinary Portland cement, 45 parts of silica fume, 180 parts of MnSO4-modified white rice husk ash prepared in Example 1, 700 parts of fine aggregate, 1100 parts of coarse aggregate, 40 parts of steel fiber, 130 parts of water, and 6 parts of water-reducing agent.

[0067] Preparation of ultra-high performance concrete based on MnSO4-modified white rice husk ash:

[0068] S1. Mix cement, silica fume, MnSO4-modified white rice husk ash, fine aggregate and coarse aggregate according to the weight parts, add to a mixer and mix at low speed (80 rpm, 3 min) until uniform; then add water and water-reducing agent and continue mixing at low speed (80 rpm, 5 min) to obtain a mixed slurry.

[0069] S2. Straight brass-galvanized steel fibers are added to the mixed slurry through a square hole sieve and mixed evenly by medium-speed stirring (160 rpm, 3 min) to obtain ultra-high performance concrete based on MnSO4 modified white rice husk ash.

[0070] S3. After the ultra-high performance concrete based on MnSO4 modified white rice husk ash that was mixed evenly in S2 is stirred at high speed (360 rpm, 2 min), it is quickly poured into the mold and vibrated to form the concrete.

[0071] S4. After pouring, cure under standard curing conditions (temperature: 20±2℃, relative humidity: >95%RH) until the specified age.

[0072] Example 3

[0073] An ultra-high performance concrete based on MnSO4-modified white rice husk ash, the raw materials of which include, by weight:

[0074] The ingredients are: 500 parts cement, 40 parts silica fume, 150 parts MnSO4-modified white rice husk ash prepared in Example 1, 800 parts fine aggregate, 1000 parts coarse aggregate, 30 parts steel fiber, 150 parts water, and 5 parts water-reducing agent.

[0075] Ultra-high performance concrete based on MnSO4-modified white rice husk ash is the same as in Example 2.

[0076] Example 4

[0077] An ultra-high performance concrete based on MnSO4-modified white rice husk ash, the raw materials of which include, by weight:

[0078] The ingredients are: 400 parts cement, 50 parts silica fume, 200 parts MnSO4-modified white rice husk ash prepared in Example 1, 600 parts fine aggregate, 1200 parts coarse aggregate, 50 parts steel fiber, 120 parts water, and 8 parts water-reducing agent.

[0079] Ultra-high performance concrete based on MnSO4-modified white rice husk ash is the same as in Example 2.

[0080] Comparative Example 6

[0081] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with the modified white rice husk ash in Comparative Example 1, and the other methods were the same as in Example 2.

[0082] Comparative Example 7

[0083] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with the modified white rice husk ash in Comparative Example 2, and the other methods were the same as in Example 2.

[0084] Comparative Example 8

[0085] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with the modified white rice husk ash in Comparative Example 3, and the other methods were the same as in Example 2.

[0086] Comparative Example 9

[0087] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with the modified white rice husk ash in Comparative Example 4, and the other methods were the same as in Example 2.

[0088] Comparative Example 10

[0089] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with the white rice husk ash in Comparative Example 5, and the other methods were the same as in Example 2.

[0090] Comparative Example 11

[0091] Compared with Example 2, the MnSO4-modified white rice husk ash prepared in Example 1 was replaced with quartz powder.

[0092] Example 5

[0093] The concrete materials in Examples 2-4 and Comparative Examples 6-11 were tested for compressive strength, flexural strength, autogenous shrinkage, and chloride ion resistance.

[0094] The compressive and flexural strength tests were conducted in accordance with GB / T45594-2025 "Test Methods for Performance of Ultra-High Performance Concrete Non-Load-Bearing Components".

[0095] The autogenous shrinkage performance test method shall be conducted in accordance with T / CECS 864-2021 "Standard for Test Methods of Ultra-High Performance Concrete".

[0096] The test method for chloride ion resistance was carried out in accordance with T / CECS 864-2021 "Standard for Test Methods of Ultra-High Performance Concrete".

[0097] The test results of the compressive strength of concrete in Examples 2-4 and Comparative Examples 6-11 are shown in Table 2. As can be seen from Table 2, the compressive strengths of the concrete materials prepared in Examples 2-4 at 7 days, 28 days, and 91 days are greater than 105 MPa, 145 MPa, and 165 MPa, respectively, meeting the requirements for UC100 strength grade concrete in GB / T45594-2025 "Test Methods for Performance of Ultra-High Performance Concrete Non-Load-Bearing Members". In Comparative Example 6, lowering the temperature of MnSO4 modification resulted in a decrease in the final concrete strength. This is due to incomplete combustion of organic matter, leading to a high carbon content and low effective active SiO2 content, resulting in extremely poor pozzolanic activity. In Comparative Example 7, increasing the temperature of MnSO4 modification also reduced the final concrete strength. This is because excessively high temperatures cause SiO2 particles to melt and agglomerate, destroying their nanoscale porous structure and reducing specific surface area. When the temperature exceeds 800°C, amorphous SiO2 begins to transform into a crystalline state (such as cristobalite and tridymite). Crystalline SiO2 has a stable structure and almost no pozzolanic activity. In Comparative Example 8, increasing the proportion of Mn also affected the compressive strength at 28 days and 91 days. This is because excessively high manganese content leads to the formation of excessive ettringite in the hydration reaction, resulting in significant expansion stress. This internal stress destroys the original structure of the cement paste, causing microcracks, increased porosity, and larger pore sizes. The destruction of the pore structure is the direct cause of the decrease in concrete strength, and this deteriorated structure also reduces the durability of the concrete. In Comparative Example 9, reducing the proportion of Mn resulted in a decrease in compressive strength at 28 days and 91 days. This is because MnSO4 reacts with tricalcium aluminate (C3A), a hydration reactant in cement, to form needle-like ettringite crystals. These appropriately generated ettringite crystals can fill the capillaries and microcracks inside the concrete, particularly reducing the number of harmful pores with a diameter less than 0.1 mm, thus making the internal structure of the concrete more compact. If the manganese content in the concrete system is too low, the aforementioned positive effects may not be achieved. In Comparative Examples 10 and 11, the compressive strength decreased without MnSO4 modification or without the addition of MnSO4-modified white rice husk ash, for the same reasons as in Comparative Example 9.

[0098] Table 2. Test results of concrete compressive strength in Examples 2-4 and Comparative Examples 6-11

[0099]

[0100] The flexural strength test results of concrete in Examples 2-4 and Comparative Examples 6-11 are shown in Table 3. As can be seen from Table 3, the 7-day and 28-day flexural strengths of the concrete materials prepared in Examples 2-4 are greater than 9.5 MPa and 14 MPa, respectively, which meet the requirements for flexural strength of ultra-high performance concrete in GB / T 45594-2025 "Test Method for Performance of Ultra-High Performance Concrete Non-Load-Bearing Members". The effect mechanism of MnSO4 on the flexural strength of concrete is similar to that of compressive strength. Both are achieved by filling the pores of concrete with ettringite produced by the reaction, thereby improving the flexural strength.

[0101] Table 3. Test results of flexural strength of concrete in Examples 2-4 and Comparative Examples 6-11

[0102]

[0103] The test results of the autogenous shrinkage performance of concrete in Examples 2-4 and Comparative Examples 6-11 are shown in Table 4. As can be seen from Table 4, the autogenous shrinkage effects of the concrete materials prepared in Examples 2-4 at 7 days, 28 days, and 91 days are all superior to those in the comparative examples. This is because cement hydration produces a large amount of calcium hydroxide. When external sulfate ions penetrate into the pore solution, they react with calcium hydroxide to form gypsum. The gypsum then reacts with hydrated calcium aluminate in the cement to form ettringite, resulting in an expansion effect. Adding an appropriate amount of MnSO4 for modification helps offset some of the autogenous shrinkage, thus reducing it. Comparative Examples 6 and 7 show that the MnSO4 modification temperature can affect the autogenous shrinkage of the final concrete material. This is because low temperatures lead to insufficient molecular kinetic energy, resulting in extremely slow reaction rates, and even an inability to overcome the reaction energy barrier. Rice husk ash mainly relies on its porous structure to react with Mn²⁺. + Physical adsorption or ion exchange makes it difficult to generate compounds such as manganese silicate (MnSiO3), which cannot be converted into the target oxide or silicate, thus affecting its function as an expanding agent. At excessively high temperatures, the amorphous SiO2 in rice husk ash transforms into crystals such as cristobalite and undergoes severe sintering, leading to product caking and loss of its original microporous structure. Carbon excessively reduces manganese oxides to Mn3C (manganese carbide) or metallic manganese, instead of the target MnSiO3 or Mn2SiO4, failing to provide expansion and thus affecting self-shrinkage. Comparative Examples 8 and 9 show that increasing or decreasing the Mn content affects self-shrinkage. This is because manganese, as an admixture, has lower activity than cement; excessive addition may lead to slow early hydration, a loose slurry structure, and increased drying shrinkage; insufficient addition results in less ettringite formation, leading to a less pronounced expansion effect.

[0104] Table 4. Measurement results (%) of autogenous shrinkage of concrete in Examples 2-4.

[0105]

[0106] The test results of the chloride ion resistance of concrete in Examples 2-4 and Comparative Examples 6-11 are shown in Table 5. As can be seen from Table 5, the 24-hour electrical flux values ​​of Examples 2-4 are all below 55 coulombs, which is lower than that of the comparative examples. This is because the rice husk ash particles are very fine, which can fill the tiny pores in the cement paste, making the internal structure of the concrete more compact and thus physically hindering the penetration channels of chloride ions. Rice husk ash can react with the calcium hydroxide produced by cement hydration to generate additional hydrated calcium silicate gel. This gel not only further compacts the structure but also improves the interface transition zone between the paste and aggregate in the concrete. Meanwhile, MnSO4, as an admixture, affects the cement hydration process, thereby improving the ion concentration and conductivity of the pore solution. Therefore, compared to Comparative Examples 10 and 11, the electrical flux is significantly improved when rice husk ash is not used at all or when MnSO4-modified rice husk ash is not used. In Comparative Examples 6 and 7, excessively high or low modification temperatures affected the particle size and uniformity of the rice husk ash, hindering pore filling in the concrete specimens and resulting in excessive electrical flux. In Comparative Examples 8 and 9, excessive MnSO4 addition led to the incorporation of excessive Mn ions. 2+ SO4 2+ The addition of too little Mn will affect the power flux, making it too high; if too little Mn is added, the hydration-promoting effect of Mn will not be fully utilized, ultimately affecting the power flux result.

[0107] Table 5. Test results of chloride ion resistance of concrete in Examples 2-4 and Comparative Examples 6-11

[0108]

[0109] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A high-performance concrete based on MnSO4-modified white rice husk ash, characterized in that, Its raw materials, by weight, include: 400-500 parts cement, 40-50 parts silica fume, 150-200 parts MnSO4 modified white rice husk ash, 600-800 parts fine aggregate, 1000-1200 parts coarse aggregate, 30-50 parts steel fiber, 120-150 parts water, and 5-8 parts water-reducing agent; The MnSO4-modified white rice husk ash is based on SiO2 and doped with Mn; The preparation method of the MnSO4-modified white rice husk ash includes the following steps: Rice husks were heat-treated with MnSO4 to obtain MnSO4-modified white rice husk ash; The heat treatment temperature is 650~700℃; The mass ratio of rice husk to MnSO4 was (99.8~99.85):0.

2.

2. The ultra-high performance concrete based on MnSO4-modified white rice husk ash as described in claim 1, characterized in that, The cement includes silicate cement with a strength grade of 52.5 or 52.5R.

3. The ultra-high performance concrete based on MnSO4-modified white rice husk ash as described in claim 1, characterized in that, The silica fume contains a SiO2 mass fraction of not less than 95% and a pozzolanic activity index greater than 95%. The specific surface area of ​​the silica fume is greater than 21.0 m². 2 / g, density is 2.10~2.30 g / cm³ 3 .

4. The ultra-high performance concrete based on MnSO4-modified white rice husk ash as described in claim 1, characterized in that, The average particle size of the MnSO4-modified white rice husk ash is 5–25 μm; the density is 0.3–0.5 g / cm³. 3 ; The fine aggregate is river sand with a maximum particle size of 4.5~5 mm; The coarse aggregate is basalt, with a maximum particle size of 9-11 mm; The steel fibers include straight brass-galvanized steel fibers.

5. The ultra-high performance concrete based on MnSO4-modified white rice husk ash as described in claim 1, characterized in that, The water-reducing agent includes a polycarboxylate-based high-performance water-reducing agent.

6. The method for preparing ultra-high performance concrete based on MnSO4-modified white rice husk ash according to any one of claims 1 to 5, characterized in that, Includes the following steps: S1. After mixing cement, silica fume, MnSO4-modified white rice husk ash, fine aggregate and coarse aggregate evenly, add water and water-reducing agent and mix evenly again to obtain a mixed slurry. S2. Add steel fibers to the mixed slurry and mix evenly to obtain ultra-high performance concrete based on MnSO4 modified white rice husk ash.

7. The preparation method according to claim 6, characterized in that, In S1, cement, silica fume, MnSO4-modified white rice husk ash, fine aggregate, and coarse aggregate are mixed evenly by stirring; the stirring speed is 75~85 rpm, and the stirring time is 2~3 min. In S1, water and water-reducing agent are added and mixed again by stirring; the stirring speed is 75~85 rpm and the stirring time is 2~5 min. In S2, steel fibers are added to the mixed slurry and mixed evenly by stirring; the stirring speed is 155~165 rpm and the stirring time is 3~6 min.

8. The application of the ultra-high performance concrete based on MnSO4 modified white rice husk ash as described in any one of claims 1 to 5, or the ultra-high performance concrete based on MnSO4 modified white rice husk ash prepared by the preparation method described in claim 6 or 7, in building materials.

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