Self-compacting bare concrete as well as preparation method and application thereof

Abstract

The invention relates to self-compacting bare concrete as well as a preparation method and application thereof. The concrete is prepared from the following components in parts by mass: 300-400 parts of white cement, 100-200 parts of slag, 0-50 parts of lithium slag, 0-50 parts of fly ash, 0-50 parts of silica fume, 0-6 parts of titanium dioxide, 800-1000 parts of coarse aggregate, 700-900 parts of fine aggregate, 7-8 parts of a water reducing agent, 1-2 parts of a defoaming agent, 0-30 parts of pigment and 0-1 part of a dispersing agent, the doping amount of plant fibers accounts for 0-1% of the volume of a cementing material, and the concrete is prepared by mixing and stirring the plant fibers and water. According to the present invention, the ratio is reasonable, the obtained self-compacting bare concrete can achieve the effect of no bubble in the molding appearance only under the self-gravity effect, and has characteristics of uniform color and uniform color, the plant fiber can improve the concrete toughness, the crack resistance, the impact resistance and the anti-permeability, and the plant fiber is cheap, easily available, low-carbon and environmentally friendly.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, and particularly relates to a self-compacting fair-faced concrete and a preparation method and application thereof. BACKGROUND

[0002] With the progress of modern society and the improvement of public taste, people's requirements for buildings have not only been limited to practicality, but also paid more attention to the pursuit of aesthetic properties. For this reason, people introduce many color elements to strengthen the visual effect of buildings. Different pigments have obvious influence on the working performance, mechanical properties and durability of concrete, and there are certain contradictions and problems in the technical combination of fair-faced concrete and self-compacting concrete.

[0003] Fair-faced concrete needs to expel air bubbles in the concrete by manual vibration during pouring. If the reinforcement is dense and the structure is complex, the construction difficulty will be increased, so it is hoped to improve it with the high working performance of self-compacting concrete, but many difficulties will be encountered in practical application. Since self-compacting concrete requires good working performance in design, the amount of cementitious material is large and the air content is high to increase the fluidity; at the same time, the high anti-segregation performance requirement increases the slurry viscosity by increasing the sand ratio, but this increases the difficulty of air bubble expulsion in the concrete, which is undoubtedly contrary to the requirements of fair-faced concrete. At the same time, for wall materials, good toughness is usually required, and the addition of pigments usually reduces the strength of concrete. In order to match special colors, multiple pigments are usually used together, which further reduces the strength and durability of colored fair-faced concrete. Therefore, a self-compacting fair-faced concrete and a preparation method and application thereof are urgently needed to solve the above problems. SUMMARY

[0004] In order to solve the above problems, on the one hand, the present application provides a self-compacting fair-faced concrete, which comprises cementitious material, coarse aggregate, fine aggregate, water reducing agent, defoaming agent, pigment, dispersing agent and plant fiber, the cementitious material comprises white cement, slag, lithium slag, fly ash, silica fume and titanium white powder; the mass ratio of each component is as follows: white cement 300-400 parts, slag 100-200 parts, lithium slag 0-50 parts, fly ash 0-50 parts, silica fume 0-50 parts, titanium white powder 0-6 parts, coarse aggregate 800-1000 parts, fine aggregate 700-900 parts, water reducing agent 7-8 parts, defoaming agent 1-2 parts, pigment 0-30 parts, dispersing agent 0-1 parts, and water, and the plant fiber content accounts for 0-1% of the volume of cementitious material.

[0005] Further, the plant fiber comprises at least one of sisal fiber and ramie fiber, and is subjected to surface modification treatment with a modifier.

[0006] Further, the modifier is hydrochloric acid, sulfuric acid, sodium hydroxide or sodium carbonate.

[0007] Further, the length of the single fiber in the plant fiber is 5-10mm, and the diameter is 60-70um.

[0008] Further, the lithium residue is made by acid roasting, and the specific surface area is greater than 400m 2 / kg. The lithium residue is off-white.

[0009] Further, the coarse aggregate includes 5-10mm gravel and 10-16mm gravel, and the mass ratio of 5-10mm gravel and 10-16mm gravel is 3:7.

[0010] Further, the fine aggregate includes quartz sand and river sand, and the quartz sand accounts for 32%-80% of the total amount of fine aggregate.

[0011] Further, the dispersant is a lignin sulfonate dispersant.

[0012] In another aspect, the application also provides a preparation method of the self-compacting concrete as described above, comprising the following steps:

[0013] Dry mixing the coarse aggregate, the fine aggregate, the white cement, the slag, the lithium residue, the fly ash, the silica ash and the titanium white powder;

[0014] Adding part of the water under mixing;

[0015] Adding the water reducing agent, the defoaming agent, the pigment, the dispersant and the remaining part of the water, and continuing mixing;

[0016] Adding the plant fiber, and continuing stirring to obtain the self-compacting concrete.

[0017] In another aspect, the application also provides a structural reinforcement application of the self-compacting concrete as described above, comprising the following steps:

[0018] S1, removing the original wall plaster layer;

[0019] S2, drilling the tie bar hole, the template pull rod hole and washing the wall surface with high pressure water;

[0020] S3, installing the tie bar and laying the steel mesh, supporting the template, and wetting the wall surface;

[0021] S4, pouring the concrete on the wall surface, and after the concrete solidifies, removing the template and curing.

[0022] The application has the following beneficial effects compared with the prior art due to the use of the above technical scheme:

[0023] The self-compacting concrete provided by the application has reasonable proportioning, and the obtained self-compacting concrete can achieve the effect of forming an appearance without air bubbles under the action of gravity, and has uniform color and luster, and the plant fiber can increase the toughness, enhance the crack resistance, improve the impact resistance and improve the impermeability of the concrete, and the plant fiber is cheap and easy to obtain, and is low-carbon and environmentally friendly. BRIEF DESCRIPTION OF DRAWINGS

[0024] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor on the basis of these drawings.

[0025] Figure 1 Appearance effect diagram of the white self-compacting concrete of Example 1;

[0026] Figure 2 Appearance effect diagram of the white self-compacting concrete of Example 1;

[0027] Figure 3 Appearance effect diagram of the red self-compacting concrete of Example 3;

[0028] Figure 4 Appearance effect diagram of the light purple self-compacting concrete of Example 4;

[0029] Figure 5 Compressive strength test results of the light purple self-compacting concrete of Example 4 and Comparative Examples 1-3. DETAILED DESCRIPTION

[0030] The technical solutions in the embodiments of the present application will be described clearly and completely in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only some of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the protection scope of the present application.

[0031] The application provides a self-compacting concrete, which comprises cementitious material, coarse aggregate, fine aggregate, water reducing agent, defoaming agent, pigment, dispersant and plant fiber, wherein the cementitious material comprises white cement, slag, lithium slag, fly ash, silica fume and titanium white powder; the mass ratio of each component is as follows: 300-400 parts of white cement, 100-200 parts of slag, 0-50 parts of lithium slag, 0-50 parts of fly ash, 0-50 parts of silica fume, 0-6 parts of titanium white powder, 800-1000 parts of coarse aggregate, 700-900 parts of fine aggregate, 7-8 parts of water reducing agent, 1-2 parts of defoaming agent, 0-30 parts of pigment, 0-1 part of dispersant, and a certain amount of water, and the plant fiber accounts for 0-1% of the volume of the cementitious material.

[0032] Specifically, the color of the self-compacting concrete can be configured according to requirements, if white concrete is required, no pigment is added, and if colored concrete is required, pigment is added as required.

[0033] In an optimal embodiment, the white cement is P.W42.5 white portland cement with whiteness ≥ 89%.

[0034] In an optimal embodiment, the dispersant is a lignosulfonate dispersant.

[0035] In an optimal embodiment, the defoaming agent is an organic silicon liquid defoaming agent.

[0036] In an optimal embodiment, the pigment is iron oxide red pigment or nano iron oxide red pigment.

[0037] In an optimal embodiment, the plant fiber comprises at least one of sisal fiber and ramie fiber, the length of a single fiber is 5-10 mm, and the diameter is 60-70 microns, and the plant fiber is modified on the surface by a modifier before use.

[0038] As one of the specific embodiments, the modification treatment of the ramie fibers is the key prerequisite to ensure their uniform dispersion in the concrete and play a toughening role. The treatment process contains two stages of physical pretreatment and chemical treatment in turn. The physical pretreatment performed first adopts the ultrasonic cleaning method, the core purpose of which is to effectively remove the dust, grease and various impurities attached to the fiber surface, providing a clean and activated interface for the subsequent chemical reaction; the specific operation is to place the original ramie fibers in clean water, continuously vibrate for 30 minutes at room temperature using an ultrasonic container, and realize deep cleaning through cavitation effect. The chemical treatment performed next is alkali immersion, which aims to selectively corrode the pectin, hemicellulose and other non-cellulose components on the surface of the fibers by using alkaline solution, so as to increase the surface roughness and significantly improve the mechanical engagement ability with the cement matrix; in the specific implementation, the cleaned ramie fibers are completely immersed in a sodium hydroxide solution with a concentration of 1 mol / L, continuously soaked for 72 hours at room temperature to ensure sufficient reaction, then taken out and washed with a large amount of deionized water to neutralize, so as to completely remove the residual alkali, and finally placed in an oven at 70°C to dry to constant weight for use.

[0039] As one of the specific embodiments, the sisal fibers, due to their excellent toughness but high lignin content, the focus of their treatment is to clean the surface more thoroughly and activate the interface properties. The physical pretreatment stage also adopts ultrasonic cleaning, the core goal of which is to efficiently remove the residual pulp, sand and other pollutants between the fiber bundles, creating ideal conditions for chemical modification; the specific operation is to place the original sisal fibers in clean water, continuously vibrate for 40 minutes at room temperature using an ultrasonic container, and ensure the cleaning effect of the thick and strong fibers by extending the action time. The chemical treatment is achieved by alkali immersion, focusing on dissolving the high lignin content in the fibers and moderately etching their surface to expose more cellulose microfibers, thereby greatly enhancing the interfacial bond strength with the cement paste; the specific operation is to completely immerse the cleaned sisal fibers in a sodium hydroxide solution with a concentration of 1.2 mol / L, continuously soak for 48 hours in a mild heating environment at 60°C to promote reaction efficiency, wash with a large amount of deionized water to neutralize after treatment, and finally place in an oven at 75°C to dry to constant weight.

[0040] The preparation method of the self-compacting concrete is as follows:

[0041] Dry mix the coarse aggregate, fine aggregate, white cement, slag, lithium slag, fly ash, silica fume, and titanium white powder;

[0042] Add part of the water under mixing;

[0043] Add the water reducing agent, defoaming agent, pigment, dispersant, and the remaining part of the water, and continue to mix;

[0044] Add the plant fibers, continue to stir, and obtain the self-compacting concrete.

[0045] The performance of the self-compacting concrete of the present application is described below through specific examples:

[0046] Example 1

[0047] The present example provides a white self-compacting concrete, which comprises the following components in terms of mass ratio: 373 parts of white cement, 128 parts of slag, 32 parts of lithium slag, 886 parts of coarse aggregate, 820 parts of fine aggregate, 7.5 parts of water reducing agent, 0.5 parts of dispersing agent, 1.6 parts of defoaming agent, 5.3 parts of titanium white powder, 0.5% of sisal fiber based on the volume of cementitious materials, and a certain amount of water mixed and stirred.

[0048] The fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total mass of the fine aggregate, and the fineness modulus is 2.65.

[0049] The plant fiber is sisal fiber, with a fiber length of 5-10 mm and a diameter of 60-70 μm. The sisal fiber is modified before use: first ultrasonic cleaning for 40 minutes, then soaked in a 1.2 mol / L sodium hydroxide solution at 60°C for 48 hours to effectively remove lignin and enhance the interfacial adhesion between the fiber and the cement matrix. This treatment aims to maximize the use of the high toughness advantage of sisal fiber, thereby significantly enhancing the compressive strength and impact resistance of the concrete.

[0050] Example 2

[0051] The present example provides a white self-compacting concrete, which comprises the following components in terms of mass ratio: 364 parts of white cement, 125 parts of slag, 31 parts of lithium slag, 890 parts of coarse aggregate, 800 parts of fine aggregate, 0.5 parts of dispersing agent, 7.3 parts of water reducing agent, 1.0 parts of defoaming agent, 5.2 parts of titanium white powder, 0.5% of ramie fiber based on the volume of cementitious materials, and a certain amount of water mixed and stirred.

[0052] The fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total mass of the fine aggregate, and the fineness modulus is 2.65.

[0053] The plant fiber is ramie fiber, with a fiber length of 5-10 mm and a diameter of 60-70 μm. The ramie fiber is specially modified before use: first ultrasonic cleaning for 30 minutes, then soaked in a 1 mol / L sodium hydroxide solution at room temperature for 72 hours to effectively remove pectin and hemicellulose, increase the surface roughness, and thus improve its dispersibility in the slurry, optimize the fluidity and uniformity of the concrete.

[0054] Example 3

[0055] The embodiment provides a red self-compacting concrete, which comprises the following components in percentage by mass: 364 parts of white cement, 125 parts of slag, 31 parts of lithium slag, 890 parts of coarse aggregate, 800 parts of fine aggregate, 0.5 parts of dispersant, 7.3 parts of water reducing agent, 1.0 part of defoaming agent, 20.8 parts of pigment, 0.5% of sisal fiber in volume of cementing material, and a certain amount of water.

[0056] The pigment is a nano iron oxide red pigment.

[0057] The fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total fine aggregate in mass, and the fineness modulus is 2.65.

[0058] The modification treatment of the sisal fiber is shown in Embodiment 1, which is not described herein again.

[0059] Embodiment 4

[0060] The embodiment provides a light purple self-compacting concrete, which is successfully prepared in a white cement-slag-fly ash specific cementing system through the synergistic effect of a nano iron oxide red pigment and a lignin sulfonate dispersant, and the light purple color is uniform, and the early strength of the concrete is significantly improved. The concrete comprises the following components in percentage by mass: 364 parts of white cement, 125 parts of slag, 31 parts of fly ash, 890 parts of coarse aggregate, 800 parts of fine aggregate, 0.5 parts of dispersant, 7.3 parts of water reducing agent, 1.0 part of defoaming agent, 20.8 parts of pigment, 0.5% of sisal fiber in volume of cementing material, and a certain amount of water.

[0061] The pigment is a nano iron oxide red pigment.

[0062] The fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total fine aggregate in mass, and the fineness modulus is 2.65.

[0063] The modification treatment of the sisal fiber is shown in Embodiment 1, which is not described herein again.

[0064] Embodiment 5

[0065] The embodiment provides a bright white self-compacting concrete, which comprises the following components in percentage by mass: 364 parts of white cement, 125 parts of slag, 15 parts of lithium slag, 16 parts of silica fume, 890 parts of coarse aggregate, 800 parts of fine aggregate, 0.5 parts of dispersant, 7.3 parts of water reducing agent, 1.0 part of defoaming agent, 5.2 parts of titanium white, 0.5% of sisal fiber in volume of cementing material, and a certain amount of water.

[0066] The fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total fine aggregate in mass, and the fineness modulus is 2.65.

[0067] The modification treatment of the sisal fibers is shown in Example 1, which is not repeated here.

[0068] In each of the above examples, the coarse aggregate comprises 5-10 mm gravel and 10-16 mm gravel, and the mass ratio of the 5-10 mm gravel to the 10-16 mm gravel is 3:7.

[0069] In each of the above examples, the lithium slag is obtained by acid roasting and is off-white, with a specific surface area greater than 400 m 2 / kg.

[0070] In each of the above examples, the dispersant is a lignin sulfonate dispersant.

[0071] In each of the above examples, the defoaming agent is an organic silicon liquid defoaming agent.

[0072] In each of the above examples, the water reducing agent is a polycarboxylic acid type water reducing agent.

[0073] To clearly verify the synergistic effect of the self-compacting concrete formulation of the present application, especially the key technical effect of the nano iron oxide red pigment and the dispersant in achieving special color and improving early strength, the following comparative experiments are set. Example 4 shows the optimal formulation of the present application, while Comparative Examples 1-3 form a group of gradually deep comparisons by changing the key components.

[0074] Comparative Example 1

[0075] This comparative example provides a benchmark concrete without adding pigment, and the only difference between its formulation and that of Example 4 is that no pigment is added, which is intended to verify that the light purple color does not come from the cementitious material itself and to quantitatively evaluate the independent contribution of the nano pigment to the strength. The components include the following mass ratios: 364 parts of white cement, 125 parts of slag, 31 parts of fly ash, 890 parts of coarse aggregate, 800 parts of fine aggregate, 0.5 parts of dispersant, 7.3 parts of water reducing agent, 1.0 parts of defoaming agent, 0.5% of sisal fibers based on the volume of cementitious materials, and a certain amount of water mixed and stirred.

[0076] The test results show that the 3d compressive strength is 28.1 MPa, which is lower than that of Example 4, which is 29.9 MPa. This comparison clearly proves that the nano iron oxide red pigment added in the present application has a positive strengthening effect on the early strength of the concrete.

[0077] Comparative Example 2

[0078] The comparative example 4 provides a light purple self-compacting fair-faced concrete, which comprises the following components in terms of mass ratio: white cement 364 parts, slag 125 parts, fly ash 31 parts, coarse aggregate 890 parts, fine aggregate 800 parts, dispersant 0.5 parts, water reducing agent 7.3 parts, defoaming agent 1.0 part, nano-iron oxide red pigment 10.4 parts, and 0.5% of the volume of cementitious materials of sisal fiber, which are mixed and stirred with a certain amount of water.

[0079] The concrete prepared has uneven surface color and color difference, and its 7d compressive strength is 40.3 MPa, which is lower than 42.5 MPa of the example 4. This shows that if there is a lack of sufficient dispersant, the nano pigment cannot be effectively dispersed, which not only affects the apparent effect, but also leads to strength reduction due to agglomeration effect.

[0080] Comparative example 3

[0081] The comparative example 4 provides a light purple self-compacting fair-faced concrete, which comprises the following components in terms of mass ratio: white cement 364 parts, slag 125 parts, fly ash 31 parts, coarse aggregate 890 parts, fine aggregate 800 parts, dispersant 0.5 parts, water reducing agent 7.3 parts, defoaming agent 1.0 part, nano-iron oxide red pigment 10.4 parts, and 0.5% of the volume of cementitious materials of sisal fiber, which are mixed and stirred with a certain amount of water.

[0082] Although its 3d early strength is the highest, which is 31.3 MPa, its 7d strength growth curve slows down, and the 60d late strength development potential is not as good as that of the example 4. More importantly, the actual mixture workability is poor, the color is too deep and uneven. This comparison proves that blindly increasing the pigment content without matching the corresponding dispersion technology is an undesirable solution. It highlights the scientificity and superiority of the precise ratio of “pigment-dispersant-cementitious material” in the example 4 of the present application.

[0083] In the above comparative examples, the coarse aggregate comprises 5-10 mm gravel and 10-16 mm gravel, and the mass ratio of 5-10 mm gravel and 10-16 mm gravel is 3:7.

[0084] In the above comparative examples, the fine aggregate comprises quartz sand and river sand, and the quartz sand accounts for 32% of the total fine aggregate mass, and the fineness modulus is 2.65.

[0085] In the above comparative examples, the dispersant is a lignin sulfonate dispersant.

[0086] In the above comparative examples, the defoaming agent is an organic silicon liquid defoaming agent.

[0087] In the above comparative examples, the pigment is a nano-iron oxide red pigment.

[0088] In the above comparative examples, the water reducing agent is a polycarboxylic acid type water reducing agent.

[0089] The white self-compacting fair-faced concrete obtained through Examples 1 and 2 was compared with the white self-compacting fair-faced concrete of Examples 1 and 2. The concrete slump, slump spread, and spread time T of the white self-compacting fair-faced concrete of Examples 1 and 2 were compared. 500 Testing was conducted using methods consistent with the standard "Technical Specification for Application of Self-Compacting Concrete" (T / CECS 203-2021). The 28-day compressive strength of white self-compacting fair-faced concrete was tested, and the results are as follows:

[0090] Table 1. Test results of workability and compressive strength of white self-compacting fair-faced concrete mixture.

[0091]

[0092] Based on the performance test results of Examples 1 and 2, both Examples 1 and 2 meet the performance indicators of self-compacting concrete mixtures in the "Technical Specification for Application of Self-Compacting Concrete" (T / CECS 203-2021). Example 1 meets the requirements of SF2 grade in the performance indicators, and Example 2 meets the requirements of SF3 grade in the performance indicators.

[0093] Based on the compressive strength test results of Examples 1 and 2, the compressive strength of both white self-compacting fair-faced concrete reached over 42.5 MPa, meeting the design requirements.

[0094] As per the instruction manual Figure 1 As shown, the white self-compacting fair-faced concrete of Examples 1-2 has an appearance effect. The white self-compacting fair-faced concrete specimens achieve the effect of no air bubbles in the molded appearance only under their own gravity. Under the action of dispersant and polycarboxylate superplasticizer, lithium slag and other powders and fibers can be effectively dispersed. The grayish-white color of lithium slag can have a good white effect with other components, so that the concrete surface after mixing is smooth and presents a uniform white color, with excellent appearance performance.

[0095] As per the instruction manual Figure 2 The image shown is a rendering of a white self-compacting fair-faced concrete surface. The surface of the white self-compacting fair-faced concrete surface is smooth, free of air bubbles, and exhibits a uniform white color. At the same time, the plant fibers increase the toughness of the concrete, prevent shrinkage and cracking of the concrete wall, and extend its service life. It can be used for excellent functional design and renovation of old urban areas.

[0096] This embodiment also provides a structural reinforcement application of the above-mentioned self-compacting fair-faced concrete in the renovation of old urban areas. The specific steps are as follows:

[0097] S1, the original wall plaster layer is eradicated, when the original wall has loose parts, the loose parts should be cleared first to avoid the problem of poor adhesion after the concrete is applied to the wall later;

[0098] S2, drill tie bar holes, template tie rod holes and wash the wall with high pressure water to ensure that the wall with removed plaster layer is cleaned;

[0099] S3, install tie bars and lay steel mesh, set up formwork, and wet the wall;

[0100] S4, the self-compacting concrete prepared by the application is used to cast the wall, which can be cast by pressure injection from top to bottom or by pouring from bottom to top, and after the concrete is solidified, the formwork is removed and maintained.

[0101] The self-compacting concrete prepared by the application is used for wall reinforcement, and the self-compacting concrete can complete the construction under its own gravity, achieving excellent construction effect and simplifying the difficulty of old city reconstruction. Of course, the self-compacting concrete is also suitable for wall or ground construction of newly built buildings.

[0102] In Example 5, silica fume is used instead of part of lithium slag as a cementitious material for self-compacting concrete, and the appearance of the self-compacting concrete test piece presents a bright white color, and the appearance after forming has fewer bubbles. This is because, compared with lithium slag, silica fume has a white color with a slight gray color, a glass luster, and a pearl luster on the cleavage surface, and the surface is smoother. At the same time, it has a larger specific surface area, and its small spherical body can play a lubricating role, which is beneficial to the stirring of self-compacting concrete, making the color more uniform and beautiful.

[0103] As shown in the accompanying drawings of the specification, Figure 3 the appearance effect diagram of the red self-compacting concrete of Example 3, the red self-compacting concrete test piece can achieve a molded appearance without bubbles under its own gravity, and under the action of the dispersing agent, the concrete surface is smooth and presents a uniform red color, and the depth of the red color of the self-compacting concrete can be changed according to the amount of pigment, and the self-compacting concrete has excellent appearance performance.

[0104] As shown in the accompanying drawings of the specification, Figure 4 the appearance effect diagram of the light purple self-compacting concrete of Example 4, the light purple self-compacting concrete test piece can achieve a molded appearance without bubbles under its own gravity, and under the action of the dispersing agent, the concrete surface is smooth and presents a uniform light purple color, and the depth of the light purple color of the self-compacting concrete can be changed according to the amount of pigment, and the self-compacting concrete has excellent appearance performance.

[0105] Nanomaterials have small particle size and can be filled in the pores of the hydration products of concrete as excellent cementitious materials. However, nanomaterials are more likely to agglomerate and are difficult to disperse. In this system, the dispersant provides strong steric repulsion between the nanometer iron oxide particles, and in combination with the polycarboxylate superplasticizer, the dispersion of nanometer iron oxide red and plant fibers is more uniform. Mixing nanometer iron oxide red pigment with cement, slag, fly ash and other active minerals can produce a light purple color without showing the red color of the nanometer iron oxide red pigment itself. This is because the nanometer iron oxide red pigment has a small particle size and can be filled in the pores of various active minerals, so that the red color is weakened, and a light purple color is produced under the combined action of cement, slag, fly ash and other active minerals. The use of a variety of pigments for blending and mixing can be reduced, the controllability is stronger, the color stability is better, the color change is less likely to occur, the color can be kept stable for a long time, and the color purity is higher, which can maximize the brightness and saturation of the color.

[0106] Generally, the agglomeration of pigments will adversely affect the strength development and durability of fair-faced concrete, and will significantly reduce the strength of fair-faced concrete. As shown in the Figure 5 The compressive strength test results of the light purple self-compacting fair-faced concrete are shown in the table. It can be seen from the test results that the nanometer iron oxide red pigment and the fibers are uniformly dispersed under the action of the dispersant, and the nanometer iron oxide red pigment can improve the early compressive strength of the self-compacting fair-faced concrete. The compressive strengths of Example 4 and Comparative Examples 1-3 are 29.9 MPa, 28.1 MPa, 29.8 MPa and 31.3 MPa, respectively, at an age of 3 d. The compressive strength of Comparative Example 3 increased by 11.4% compared with Comparative Example 1. The compressive strengths of Example 4 and Comparative Examples 1-3 are 42.5 MPa, 43.1 MPa, 40.3 MPa and 45.1 MPa, respectively, at an age of 7 d. The nanometer iron oxide red pigment is different from general pigments and does not reduce the early compressive strength of fair-faced concrete, which is beneficial to the early construction maintenance and form removal. The compressive strengths of Example 4 and Comparative Example 1 are 75 MPa and 77.9 MPa, respectively, at an age of 60 d, indicating that the nanometer iron oxide red pigment does not damage the later strength of fair-faced concrete and is beneficial to the strength development of fair-faced concrete.

[0107] In summary, the Figure 5The anti-compressive strength test results of the self-leveling concrete and the apparent effect of each example and comparative example show that: Example 4 (the present application) exhibits the best performance, i.e. the color is uniform light purple, the workability is good, and the early and late strength is balanced. Comparative Example 1 proves that the addition of the nano iron oxide red pigment is a necessary condition for forming light purple and improving the early strength. Comparative Example 2 and Comparative Example 3 prove from the negative side that the sufficient use of the dispersant and the accurate ratio of the pigment and the dispersant are the key guarantee for exerting the positive effect of the nano pigment and avoiding the negative effect. Any change of a single component is difficult to achieve the same technical effect without the overall technical solution of the present application. Therefore, the formula provided by Example 4 of the present application is an organic whole with mutual support and synergistic effect, rather than a simple superposition of components, and the comprehensive improvement of the color, strength and workability brought by the formula embodies outstanding substantial features and significant progress.

[0108] Compared with general pigments, the nano iron oxide red pigment in the system of the present application can jointly act with different active minerals to prepare special light purple self-compacting concrete, and the nano iron oxide red pigment can improve the early anti-compressive strength of the self-compacting concrete, is beneficial to the early construction maintenance and form removal, and does not cause damage to the late strength of the self-compacting concrete, and has excellent effect. The Fe2O3 nanoparticles can reduce the number of Ca(OH)2 crystals and optimize the size of the Ca(OH)2 crystals, fill in the gap of the ettringite and C-S-H gel structure, and make the structure of the hydration product of the self-compacting concrete more dense.

[0109] It should be understood by those skilled in the art that the present application can be implemented in many other specific forms without departing from the spirit and scope of the present application. Although the embodiments of the present application have been described, it should be understood that the present application should not be limited to this embodiment, and those skilled in the art can make changes and modifications within the spirit and scope of the present application as defined in the appended claims.

Claims

1. A self-compacting fair-faced concrete, characterized in that, The product comprises cementitious materials, coarse aggregate, fine aggregate, water-reducing agent, defoamer, pigment, dispersant, and plant fiber. The cementitious materials include white cement, slag, lithium slag, fly ash, silica fume, and titanium dioxide. The mass proportions of each component are as follows: white cement 300-400 parts, slag 100-200 parts, lithium slag 0-50 parts, fly ash 0-50 parts, silica fume 0-50 parts, titanium dioxide 0-6 parts, coarse aggregate 800-1000 parts, fine aggregate 700-900 parts, water-reducing agent 7-8 parts, defoamer 1-2 parts, pigment 0-30 parts, dispersant 0-1 part, and water as needed. The plant fiber content accounts for 0-1% of the volume of the cementitious materials.

2. The self-compacting fair-faced concrete according to claim 1, characterized in that, The plant fiber includes at least one of sisal fiber and ramie fiber, and is surface modified using a modifier.

3. The self-compacting fair-faced concrete according to claim 2, characterized in that, The modifier is hydrochloric acid, sulfuric acid, sodium hydroxide, or sodium carbonate.

4. The self-compacting fair-faced concrete according to claim 1, characterized in that, The plant fiber has a length of 5-10 mm and a diameter of 60-70 μm.

5. The self-compacting fair-faced concrete according to claim 1, characterized in that, The lithium slag was prepared by acid roasting and has a specific surface area greater than 400 m². 2 / kg.

6. The self-compacting fair-faced concrete according to claim 1, characterized in that, The coarse aggregate includes 5-10mm crushed stone and 10-16mm crushed stone, with a mass ratio of 3:7 between the two.

7. The self-compacting fair-faced concrete according to claim 1, characterized in that, The fine aggregate includes quartz sand and river sand, with the quartz sand accounting for 32% to 80% of the total fine aggregate.

8. The self-compacting fair-faced concrete according to claim 1, characterized in that, The dispersant is a lignin sulfonate dispersant.

9. A method for preparing self-compacting fair-faced concrete as described in any one of claims 1-8, characterized in that, Includes the following steps: The coarse aggregate, fine aggregate, white cement, slag, lithium slag, fly ash, silica fume, and titanium dioxide are dry-mixed. Add some water while mixing; Add water-reducing agent, defoamer, pigment, dispersant, and the remaining water, and continue mixing; Plant fiber was added and stirring continued to obtain the self-compacting fair-faced concrete.

10. A structural reinforcement application of self-compacting fair-faced concrete as described in any one of claims 1-8, characterized in that, Includes the following steps: S1, Remove the original plaster layer on the wall; S2, Drill holes for tie bars and formwork tie rods and wash the wall surface with high-pressure water; S3, Install tie bars and lay steel mesh, set up formwork, and wet the wall surface with water; S4 uses concrete to pour the wall surface. After the concrete has solidified, the formwork is removed and the wall is cured.

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