Self-compacting bare concrete and preparation method thereof

Abstract

The invention relates to the technical field of concrete, and particularly discloses self-compacting bare concrete and a preparation method thereof. The fair-faced concrete is mainly prepared from the following raw materials in parts by weight: 470 to 490 parts of Portland cement, 80 to 100 parts of fly ash, 30 to 40 parts of silica fume, 930 to 1000 parts of stone, 1300 to 1400 parts of sand, 14 to 16 parts of modified nano silicon dioxide, 9 to 11 parts of acrylic polymer cement waterproof coating, 7 to 9 parts of expanding agent, 4 to 6 parts of water reducing agent and 160 to 170 parts of water. The modified silicon dioxide is obtained by treating nano silicon dioxide by adopting 3-allyloxy propyl trimethoxy silicon, 3-aminopropyl trimethoxy silane, chitosan and platycodon grandiflorum acid A. The invention further discloses a preparation method of the modified silicon dioxide. Through mutual cooperation of the raw materials, the bare concrete has the characteristics of high compressive strength, high breaking strength and high impermeability, the use stability is enhanced, the service life is prolonged, and the market demand is met.

Description

Technical Field

[0001] This application relates to the technical field of concrete, and more specifically, it relates to a self-compacting fair-faced concrete and a preparation method thereof. Background Art

[0002] Fair-faced concrete is a kind of concrete that uses the natural texture after concrete forming as the finishing effect. It has the characteristics of smooth and flat surface, distinct edges and corners, no obvious color difference, and smooth and natural lines. It has been widely used in building construction such as railways, highways, subways, bridges, high-rise buildings, and water conservancy dams. With the continuous development of the construction industry, the requirements for the performance of fair-faced concrete are also getting higher and higher. For the existing fair-faced concrete, its raw materials generally include cement, fly ash, silica fume, stones, sand, expansion agent, water reducer, and water. However, the fair-faced concrete obtained by using the above raw materials has slightly poor mechanical properties and impermeability, and needs to be further improved. Summary of the Invention

[0003] In order to improve the compressive strength, flexural strength and impermeability of fair-faced concrete, this application provides a self-compacting fair-faced concrete and a preparation method thereof.

[0004] In the first aspect, this application provides a self-compacting fair-faced concrete, adopting the following technical solution: A self-compacting fair-faced concrete is mainly made of the following raw materials in parts by weight: 470 - 490 parts of portland cement, 80 - 100 parts of fly ash, 30 - 40 parts of silica fume, 930 - 1000 parts of stones, 1300 - 1400 parts of sand, 14 - 16 parts of modified nano-silica, 9 - 11 parts of acrylic polymer cement waterproof coating, 7 - 9 parts of expansion agent, 4 - 6 parts of water reducer, and 160 - 170 parts of water; the modified silica is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A.

[0005] The self-compacting fair-faced concrete of this application, through the mutual cooperation of raw materials, has a 28d compressive strength > 57 MPa, a 28d flexural strength > 9 MPa, and a water seepage height < 5 mm. It has the characteristics of high compressive strength, high flexural strength, and high impermeability, improving the overall performance and durability of fair-faced concrete, and meeting the market demand.

[0006] In the raw materials of fair-faced concrete, nano-silica and acrylic polymer cement waterproof coating are added simultaneously, and by utilizing their synergistic effect, not only the voids are filled, the porosity is reduced, but also a lubricating effect is achieved, the fluidity is enhanced, the microstructure is improved, the density is increased, the water penetration is reduced, the structural stability is enhanced, and the mechanical properties and impermeability of fair-faced concrete are improved. Further, the nano-silica is modified, and 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A are grafted onto the surface of the nano-silica, introducing a large number of active groups onto the surface of the nano-silica, improving the activity, dispersibility, and compatibility of the modified nano-silica, enhancing the interaction between the modified nano-silica and the acrylic polymer cement waterproof coating, improving the structural stability and integrity, enabling the fair-faced concrete to exhibit better compressive strength, flexural strength, and impermeability, and extending the service life.

[0007] Optionally, the modified nano-silica is prepared by the following method: S1. Mix water and nano-silica, add 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane, stir for 1 - 3 h, filter to obtain silane-grafted silica; S2. Mix water and silane-grafted silica, add chitosan, add glutaraldehyde, stir for 3 - 5 h, filter and wash to obtain chitosan-grafted silica; S3. Mix dichloromethane and chitosan-grafted silica, add platycodic acid A, add organic peroxide, stir for 3 - 5 h, filter and wash to obtain modified nano-silica.

[0008] Optionally, the weight ratio of the nano-silica, 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A is 20:(4 - 6):(4 - 6):(4 - 6):(1 - 3).

[0009] By adopting the above technical solution, first 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane are grafted onto the surface of the nano-silica, introducing carbon-carbon double bonds and amino groups. Then in the aqueous system, chitosan is grafted onto the surface of the nano-silica by using glutaraldehyde. After that, in the organic system, platycodic acid A is grafted onto the surface of the nano-silica by using organic peroxide, thereby obtaining the modified nano-silica. In the preparation method of the present application, a suitable system is selected, and grafting is carried out step by step on the surface of the nano-silica to ensure the stability of the nano-silica preparation, enhance the activity and use effect of the nano-silica, improve the mechanical properties and impermeability of the fair-faced concrete, and enable the fair-faced concrete to exhibit better overall performance.

[0010] Optionally, the weight ratio of the nano-silica, glutaraldehyde, and organic peroxide is 20:(0.1 - 0.5):(0.1 - 0.5).

[0011] By adopting the above technical solution, the addition amount of glutaraldehyde is optimized to ensure that chitosan is effectively grafted onto the surface of nano-silica, and the addition amount of organic peroxide is also optimized to ensure that platycodin A is effectively grafted onto the surface of nano-silica, ensuring the stability of the preparation of the modified nano-silica and also ensuring that the fair-faced concrete has good mechanical properties and impermeability. In multiple embodiments, the weight ratio of nano-silica, glutaraldehyde, and organic peroxide is 20:0.2:0.2, and it can also be set as 20:0.1:0.1, 20:0.1:0.2, 20:0.1:0.5, 20:0.2:0.1, 20:0.2:0.5, 20:0.5:0.1, 20:0.5:0.2, 20:0.5:0.5 according to needs, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0012] Optionally, the organic peroxide is one or more of di-tert-butyl peroxide, diisopropyl peroxydicarbonate, cyclohexanone peroxide, cumene hydroperoxide, tert-butyl peroxybenzoate, and benzoyl peroxide.

[0013] By adopting the above technical solution, the organic peroxide is optimized to facilitate the selection of the organic peroxide.

[0014] Optionally, the weight ratio of the nano-silica, water in step S1, water in step S2, and dichloromethane is 20:(170 - 230):(170 - 230):(170 - 230).

[0015] By adopting the above technical solution, the addition amounts of water in step S1, water in step S2, and dichloromethane are optimized to facilitate the full mixing of raw materials and the grafting reaction, ensuring the stability of the preparation of the modified nano-silica. In multiple embodiments, the weight ratio of nano-silica, water in step S1, water in step S2, and dichloromethane is 1:10:10:10, and it can also be set as 20:170:170:170, 20:170:170:230, 20:170:230:170, 20:170:230:230, 20:230:170:170, 20:230:170:230, 20:230:230:170, 20:230:230:230 according to needs, but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0016] Optionally, the average particle size of the nano-silica used in the modified nano-silica is 10 - 500 nm. Preferably, the average particle size of the nano-silica used in the modified nano-silica is 100 - 300 nm. More preferably, the average particle size of the nano-silica used in the modified nano-silica is 100 - 200 nm.

[0017] By adopting the above technical solution, the particle size of the nano-silica is defined, which facilitates the selection of the nano-silica, ensures the stability of the nano-silica source, and guarantees the use effect of the nano-silica. In multiple embodiments, the average particle size of the nano-silica is 150 nm. It can also set the average particle size to 10 nm, 50 nm, 100 nm, 200 nm, 250 nm, 300 nm, 350 nm, 400 nm, 450 nm, 500 nm according to needs, but is not limited to the listed values. Other unlisted values within this value range are equally applicable.

[0018] Optionally, the acrylic polymer cement waterproof coating is one or more of LEAC-21A type, LEAC-21B type, LEAC-21HF type, LEAC-22A type, and LEAC-22B type.

[0019] By adopting the above technical solution, the acrylic polymer cement waterproof coating is optimized, which facilitates the selection of the acrylic polymer cement waterproof coating.

[0020] Optionally, the stones are two types: coarse stones and fine stones, and the weight ratio of the coarse stones to the fine stones is (2 - 4):(1 - 3). The particle size of the coarse stones is a continuous grading of 5 - 25 mm, and the particle size of the fine stones is a continuous grading of 5 - 10 mm.

[0021] By adopting the above technical solution, the particle size distribution of the stones is optimized, which increases the fluidity and compactness of the fair-faced concrete, reduces the porosity, and enhances the strength and crack resistance of the fair-faced concrete. In multiple embodiments, the weight ratio of the coarse stones to the fine stones is 3:2. It can also set the weight ratio to 2:1, 1:1, 2:3, 3:1, 4:1, 4:3 according to needs, but is not limited to the listed values. Other unlisted values within this value range are equally applicable.

[0022] Optionally, the sand is three types: coarse sand, medium sand, and fine sand, and the weight ratio of the coarse sand, medium sand, and fine sand is (9 - 11):(4 - 6):(1 - 3). The particle size of the coarse sand is a continuous grading of 0.5 - 2 mm, the particle size of the medium sand is a continuous grading of 0.35 - 0.5 mm, and the particle size of the fine sand is a continuous grading of 0.25 - 0.35 mm.

[0023] By adopting the above technical solutions, the particle size distribution of the sand is optimized, which facilitates the preparation of the sand and can also improve the fluidity and compactness of fair-faced concrete, improve the workability, and enable the fair-faced concrete to exhibit better mechanical properties and structural stability. In multiple embodiments, the weight ratio of coarse sand, medium sand, and fine sand is 10:5:2, and the weight ratio can also be set to 9:4:1, 9:4:3, 9:6:1, 9:6:3, 11:4:1, 11:4:3, 11:6:1, 11:6:3 as needed, but it is not limited to the listed values, and other unlisted values within this numerical range are equally applicable.

[0024] Optionally, the expansive agent is a UEA expansive agent, and the water reducing agent is a polycarboxylate water reducing agent.

[0025] By adopting the above technical solutions, the expansive agent and the water reducing agent are optimized, which facilitates the selection of the expansive agent and the water reducing agent. The expansive agent can effectively compensate for the shrinkage of fair-faced concrete, reduce the cracks generated due to shrinkage, and improve the integrity and durability of the structure. The water reducing agent can reduce the viscosity and fluidity of fair-faced concrete, significantly improve the workability of fair-faced concrete, reduce the water consumption, and increase the strength and durability.

[0026] In a second aspect, the present application provides a method for preparing the self-compacting fair-faced concrete described above, adopting the following technical solutions: A method for preparing the self-compacting fair-faced concrete described above mainly includes the following steps: Mix portland cement, fly ash, silica fume, gravel, sand, modified nano-silica, acrylic polymer cement waterproof coating, expansive agent, water reducing agent, and water to obtain fair-faced concrete.

[0027] By adopting the above technical solutions, it is convenient to prepare fair-faced concrete.

[0028] In summary, the present application has at least the following beneficial effects: In the self-compacting fair-faced concrete of the present application, modified nano-silica and acrylic polymer cement waterproof coating are simultaneously added to the raw materials, and 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A are grafted on the surface of the nano-silica, introducing a large number of active groups, enhancing the activity, dispersibility, and compatibility. And by utilizing the synergistic effect among them, the fluidity is enhanced, the microstructure is improved, the density is increased, the water penetration is reduced, the structural stability and integrity are improved, so that the 28-day compressive strength > 57 MPa, the 28-day flexural strength > 9 MPa, and the water seepage height < 5 mm, showing the characteristics of high compressive strength, high flexural strength, and high impermeability, enhancing the service stability and life, and meeting the market demand. Specific embodiments

[0029] To make this application easier to understand, the following will further elaborate on this application in conjunction with embodiments. These embodiments are only illustrative and are not limited to the application scope of this application. Raw materials or components used in this application can be obtained through commercial channels or conventional methods without special instructions.

[0030] Preparation Example Preparation Example 1 A modified nano-silica is prepared by the following method: S1. At a stirring rate of 300 r / min, 20 g of nano-silica is added to 200 g of water and stirred for 3 min. 5 g of 3-allyloxypropyltrimethoxysilane and 5 g of 3-aminopropyltrimethoxysilane are added and stirred for 2 h. Then filtration is carried out to obtain silane-grafted silica.

[0031] Among them, the nano-silica is sedimentation silica, and the average particle size of the nano-silica is 150 nm, and it is selected from Shijiazhuang Aohe New Materials Co., Ltd.

[0032] S2. At a stirring rate of 300 r / min, the silane-grafted silica obtained in step S1 is added to 200 g of water and stirred for 3 min. 5 g of chitosan is added and stirred for 3 min. 0.2 g of glutaraldehyde is added and stirred for 4 h. Then filtration is carried out, washed once with 50 g of water and once with 50 g of ethanol to obtain chitosan-grafted silica.

[0033] Among them, the chitosan is water-soluble chitosan and is selected from Jiangxi Huayuyuan Biotechnology Co., Ltd.

[0034] S3. At a stirring rate of 300 r / min, the chitosan-grafted silica obtained in step S3 is added to 200 g of dichloromethane and stirred for 3 min. 2 g of platycodin A is added and stirred for 3 min. 0.2 g of organic peroxide is added and stirred for 4 h. Then filtration is carried out, washed once with 50 g of dichloromethane, once with 50 g of ethanol and once with 50 g of water to obtain the modified nano-silica.

[0035] Among them, the organic peroxide is di-tert-butyl peroxide.

[0036] Preparation Example 2 A modified nano-silica, the difference from Preparation Example 1 lies in the addition amounts of 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodin A, and the addition amount of 3-allyloxypropyltrimethoxysilane is 4 g, the addition amount of 3-aminopropyltrimethoxysilane is 6 g, the addition amount of chitosan is 4 g, and the addition amount of platycodin A is 1 g.

[0037] Preparation Example 3 A modified nano-silica, which is different from Preparation Example 1 in that the addition amounts of 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A are different, and the addition amount of 3-allyloxypropyltrimethoxysilane is 6 g, the addition amount of 3-aminopropyltrimethoxysilane is 4 g, the addition amount of chitosan is 6 g, and the addition amount of platycodic acid A is 3 g. Example

[0038] Table 1 Raw material dosages of fair-faced concrete (unit: ×10 g) Example 1 A self-compacting fair-faced concrete, the raw materials and their mixing ratios of which are shown in Table 1.

[0039] Among them, the Portland cement is Portland cement P.O42.5R; the fly ash is Class II fly ash; the content of silicon dioxide in silica fume is 93 wt%; the acrylic polymer cement waterproof coating is LEAC-21 A type and is selected from Shenzhen Zhonghe Beiyan Waterproof and Anticorrosive Material Co., Ltd.; the expansive agent is UEA expansive agent and is selected from Wuhan Jiyesheng Chemical Co., Ltd.; the water reducing agent is AN4000 polycarboxylate water reducing agent and is selected from Beijing Academy of Building Engineering Co., Ltd.; the modified nano-silica is prepared by the method of Preparation Example 1.

[0040] The stones are two types, coarse stones and fine stones, and the weight ratio of the coarse stones to the fine stones is 3:2. The particle size of the coarse stones is a continuous gradation of 5 - 25 mm, and the particle size of the fine stones is a continuous gradation of 5 - 10 mm. The stones are granite crushed stones; the sand is three types, coarse sand, medium sand, and fine sand, and the weight ratio of the coarse sand, medium sand, and fine sand is 10:5:2. The particle size of the coarse sand is a continuous gradation of 0.5 - 2 mm, the particle size of the medium sand is a continuous gradation of 0.35 - 0.5 mm, and the particle size of the fine sand is a continuous gradation of 0.25 - 0.35 mm. The sand is quartz sand.

[0041] A preparation method of a self-compacting fair-faced concrete mainly includes the following steps: Add fly ash, silica fume, stones, sand, and modified nano-silica to the Portland cement and stir for 3 min. Add the expansive agent and the water reducing agent and stir for 3 min. Add the acrylic polymer cement waterproof coating and water and stir for 10 min to obtain fair-faced concrete.

[0042] Example 2 A self-compacting fair-faced concrete, which is different from Example 1 in that the raw material mixing ratio of the fair-faced concrete is different, and its raw material mixing ratio is shown in Table 1.

[0043] Example 3 A self-compacting fair-faced concrete, which is different from that of Example 1 in that the raw material ratio of the fair-faced concrete is different, and the raw material ratio is shown in Table 1.

[0044] Example 4 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the fair-faced concrete, the source of the modified nano-silica is different, and the modified nano-silica is prepared by the method of Preparation Example 2.

[0045] Example 5 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the fair-faced concrete, the source of the modified nano-silica is different, and the modified nano-silica is prepared by the method of Preparation Example 3.

[0046] Comparative Example Comparative Example 1 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the concrete, the modified nano-silica and the acrylic polymer cement waterproof coating are not added.

[0047] Comparative Example 2 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the concrete, the modified nano-silica is replaced with an equal amount of acrylic polymer cement waterproof coating.

[0048] Comparative Example 3 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the concrete, the modified nano-silica and the acrylic polymer cement waterproof coating are replaced with an equal amount of nano-silica.

[0049] Comparative Example 4 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the concrete, the modified nano-silica is replaced with an equal amount of nano-silica.

[0050] Comparative Example 5 A self-compacting fair-faced concrete, which is different from that of Example 1 in that, among the raw materials of the concrete, the source of the modified nano-silica is different.

[0051] The modified nano-silica is prepared by the following method: Under a stirring rate of 300 r / min, 20 g of nano-silica is added to 200 g of water, and stirred for 3 min. 12 g of 3-allyloxypropyltrimethoxysilane and 5 g of 3-aminopropyltrimethoxysilane are added, and stirred for 2 h. Then, filtration is carried out, and it is washed once with 50 g of water, once with 50 g of ethanol, and once with 50 g of water to obtain the modified nano-silica.

[0052] Among them, the nano-silica is sedimentation method silica, and the average particle size of the nano-silica is 150 nm, and it is selected from Shijiazhuang Aohe New Materials Co., Ltd.

[0053] Comparative Example 6 A self-compacting fair-faced concrete, the difference from Example 1 is that in the raw materials of the concrete, the source of the modified nano-silica is different.

[0054] The modified nano-silica is prepared by the following method: Under a stirring rate of 300 r / min, 20 g of nano-silica is added to 200 g of water, and stirred for 3 min. 5 g of 3-allyloxypropyltrimethoxysilane and 12 g of 3-aminopropyltrimethoxysilane are added, and stirred for 2 h. Then, filtration is carried out, and it is washed once with 50 g of water, once with 50 g of ethanol, and once with 50 g of water to obtain the modified nano-silica.

[0055] Among them, the nano-silica is sedimentation method silica, and the average particle size of the nano-silica is 150 nm, and it is selected from Shijiazhuang Aohe New Materials Co., Ltd.

[0056] Comparative Example 7 A self-compacting fair-faced concrete, the difference from Example 1 is that in the preparation method of the modified nano-silica in the raw materials of the concrete, steps S2 and S3 are different.

[0057] Steps S2 and S3 are specifically as follows: Under a stirring rate of 300 r / min, the silane-grafted silica obtained in step S1 is added to 200 g of water, and stirred for 3 min. 7 g of chitosan is added, and stirred for 3 min. 0.2 g of glutaraldehyde is added, and stirred for 4 h. Then, filtration is carried out, and it is washed once with 50 g of water, once with 50 g of ethanol, and once with 50 g of water to obtain the modified nano-silica.

[0058] Among them, the chitosan is water-soluble chitosan, and it is selected from Jiangxi Huayuyuan Biotechnology Co., Ltd.

[0059] Comparative Example 8 A self-compacting fair-faced concrete, which is different from Example 1 in that in the raw materials of the concrete, in the preparation method of the modified nano-silica, Steps S2 and S3 are different.

[0060] Steps S2 and S3 are specifically as follows: At a stirring rate of 300 r / min, add the grafted silica obtained in Step S1 to 200 g of dichloromethane, and stir for 3 min. Add 7 g of platycodic acid A and stir for 3 min. Add 0.2 g of organic peroxide and stir for 4 h. Then filter, wash once with 50 g of dichloromethane, once with 50 g of ethanol, and once with 50 g of water to obtain the modified nano-silica.

[0061] Among them, the organic peroxide is di-tert-butyl peroxide.

[0062] Performance testing Respectively take the fair-faced concretes obtained in Examples 1-5 and Comparative Examples 1-8, and according to GB / T50081-2019 and GB / T50082-2009, detect the 28-day compressive strength, 28-day flexural strength, and water seepage height of the fair-faced concrete. The test results are shown in Table 2.

[0063] Table 2 Test results It can be seen from Table 2 that the fair-faced concrete of the present application has better compressive strength and flexural strength. The 28-day compressive strength is 57.14 - 58.68 MPa, and the 28-day flexural strength is 9.37 - 9.86 MPa, featuring high compressive strength and high flexural strength. Moreover, it also has a lower water seepage height, which is 4.3 - 4.9 mm, featuring high impermeability, enhancing the structural stability, improving the mechanical properties and durability, and meeting the market demand.

[0064] Compare Comparative Examples 1-4. Compared with Comparative Example 1, Comparative Example 2 adds acrylic polymer cement waterproof coating to the raw materials of the fair-faced concrete; compared with Comparative Example 1, Comparative Example 3 adds nano-silica to the raw materials of the fair-faced concrete; compared with Comparative Example 1, Comparative Example 4 adds nano-silica and acrylic polymer cement waterproof coating to the raw materials of the fair-faced concrete. It can be seen that simultaneously adding nano-silica and acrylic polymer cement waterproof coating to the raw materials of the fair-faced concrete and utilizing their synergistic effect can significantly improve the mechanical properties and impermeability of the fair-faced concrete.

[0065] Comparative Examples 4-5 will be compared. In the raw materials of the fair-faced concrete in Comparative Example 4, nano-silica is added; in the raw materials of the fair-faced concrete in Comparative Example 5, modified nano-silica is added, and it is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane. It can be seen that grafting treatment of nano-silica can increase the binding force and dispersibility of nano-silica, improve the compressive strength and flexural strength of fair-faced concrete, reduce the water seepage height, and improve the durability.

[0066] Comparative Examples 6-8 and Example 1 will be compared. The modified nano-silica in the raw materials of the fair-faced concrete in Comparative Example 6 is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane; the modified nano-silica in the raw materials of the fair-faced concrete in Comparative Example 7 is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and chitosan; the modified nano-silica in the raw materials of the fair-faced concrete in Comparative Example 8 is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane and platycodic acid A; the modified nano-silica in the raw materials of the fair-faced concrete in Example 1 is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan and platycodic acid A. It can be seen that the modified nano-silica obtained by different methods has different effects on the use in fair-faced concrete. And on the basis of treating nano-silica with 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane, further grafting chitosan and platycodic acid A, introducing a large number of active groups on the surface of nano-silica, and utilizing their synergistic effect, can further improve the compressive strength and flexural strength, and further reduce the water seepage height, making the fair-faced concrete show better comprehensive performance and enhancing the structural stability and durability.

[0067] It should be noted that the above-described embodiments are only used to explain the present application and do not constitute any limitation to the present application. The present application has been described by referring to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words rather than limiting words. Modifications can be made to the present application within the scope of the claims of the present application, and the present invention can be revised without departing from the scope and spirit of the present application. Although the present application described therein relates to specific methods, materials and embodiments, it does not mean that the present application is limited to the specific examples disclosed therein. On the contrary, the present application can be extended to all other methods and applications with the same function.

Claims

1. A self-compacting fair-faced concrete, characterized in that: Fair-faced concrete is mainly made from the following raw materials in parts by weight: 470 - 490 parts of portland cement, 80 - 100 parts of fly ash, 30 - 40 parts of silica fume, 930 - 1000 parts of stones, 1300 - 1400 parts of sand, 14 - 16 parts of modified nano-silica, 9 - 11 parts of acrylic polymer cement waterproof coating, 7 - 9 parts of expansive agent, 4 - 6 parts of water-reducing agent, and 160 - 170 parts of water; the modified silica is obtained by treating nano-silica with 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A.

2. A self-compacting fair-faced concrete according to claim 1, characterized in that: The modified nano-silica is prepared by the following method: S1. Mix water and nano-silica, add 3-allyloxypropyltrimethoxysilane and 3-aminopropyltrimethoxysilane, stir for 1 - 3 h, and filter to obtain silane-grafted silica. S2. Mix water and silane-grafted silica, add chitosan, add glutaraldehyde, stir for 3 - 5 h, filter, and wash to obtain chitosan-grafted silica. S3. Mix dichloromethane and chitosan-grafted silica, add platycodic acid A, add organic peroxide, stir for 3 - 5 h, filter, and wash to obtain modified nano-silica.

3. A self-compacting fair-faced concrete according to claim 2, characterized in that: The weight ratio of the nano-silica, 3-allyloxypropyltrimethoxysilane, 3-aminopropyltrimethoxysilane, chitosan, and platycodic acid A is 20:(4 - 6):(4 - 6):(4 - 6):(1 - 3).

4. A self-compacting fair-faced concrete according to claim 2, characterized in that: The weight ratio of the nano-silica, glutaraldehyde, and organic peroxide is 20:(0.1 - 0.5):(0.1 - 0.5).

5. The self-compacting fair-faced concrete according to claim 2, wherein: The organic peroxide is one or more of di-tert-butyl peroxide, diisopropyl peroxydicarbonate, cyclohexanone peroxide, cumene hydroperoxide, tert-butyl peroxybenzoate, and benzoyl peroxide.

6. The self-compacting fair-faced concrete according to claim 1, wherein: The average particle size of the nano-silica used in the modified nano-silica is 10 - 500 nm.

7. A self-compacting fair-faced concrete according to claim 1, characterized in that: The acrylic polymer cement waterproof coating is one or more of LEAC-21 A type, LEAC-21 B type, LEAC-21 HF type, LEAC-22 A type, and LEAC-22 B type.

8. A self-compacting fair-faced concrete according to claim 1, characterized in that: The stones are two types, coarse stones and fine stones, and the weight ratio of the coarse stones to the fine stones is (2 - 4):(1 - 3). The particle size of the coarse stones is a continuous gradation of 5 - 25 mm, and the particle size of the fine stones is a continuous gradation of 5 - 10 mm.

9. A self-compacting fair-faced concrete according to claim 1, characterized in that: The sand is three types, coarse sand, medium sand, and fine sand, and the weight ratio of the coarse sand, medium sand, and fine sand is (9 - 11):(4 - 6):(1 - 3). The particle size of the coarse sand is a continuous gradation of 0.5 - 2 mm, the particle size of the medium sand is a continuous gradation of 0.35 - 0.5 mm, and the particle size of the fine sand is a continuous gradation of 0.25 - 0.35 mm.

10. A preparation method of self-compacting fair-faced concrete according to any one of claims 1-9, characterized in that: It mainly includes the following steps: Mix the portland cement, fly ash, silica fume, stones, sand, modified nano-silica, acrylic polymer cement waterproof coating, expansive agent, water-reducing agent, and water to obtain fair-faced concrete.

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