High-performance low-carbon concrete composite admixture and preparation method thereof

Abstract

The application relates to the technical field of building construction materials, in particular to a high-performance low-carbon concrete composite admixture and a preparation method thereof.A high-performance low-carbon concrete composite admixture comprises the following preparation raw materials in parts by mass: 150-200 parts of Portland cement, 200-250 parts of blast furnace slag, 400-450 parts of fly ash, 100-120 parts of active wollastonite powder, 20-25 parts of modified fiber, 6-8 parts of an additive, 6-8 parts of a high-efficiency water reducing agent and 200-250 parts of water.The high-performance low-carbon concrete composite admixture provided by the application has the advantages of simple production, low cost, green environmental protection, high strength, good crack resistance, strong durability and the like, can greatly reduce carbon emission, and is suitable for large-scale popularization and application.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of building construction materials, and in particular to a high-performance low-carbon concrete composite admixture and a preparation method thereof. BACKGROUND

[0002] The engineering construction industry accounts for more than 40% of global carbon emissions, and concrete, as the most widely used building material, accounts for 6-10% of global carbon emissions. In the current environment where all countries in the world are actively reducing carbon emissions, it is of great practical significance to develop and utilize low-carbon concrete. Cement is the main source of carbon emissions in concrete, and the emission of CO2 is about 830 kg per ton of portland cement clinker produced.

[0003] With the increasing awareness of environmental protection around the world, low-carbon building materials have gradually become the development trend of the construction industry. Traditional concrete is criticized for producing a large amount of carbon dioxide during the manufacturing process, which prompts researchers to seek alternative raw materials and new preparation processes to reduce its carbon footprint. At present, there have been some research reports on the use of industrial waste (such as fly ash, slag, etc.) to replace cement components, but there are generally problems such as strength reduction, durability deficiency, etc., which limit its large-scale application.

[0004] Therefore, how to reduce carbon emissions while reducing costs and improve the mechanical properties, crack resistance and durability of concrete has become a problem to be solved. SUMMARY

[0005] The application aims at the deficiencies of the prior art, and provides a high-performance low-carbon concrete composite admixture and a preparation method thereof. The high-performance low-carbon concrete composite admixture prepared by the application has the advantages of simple preparation, low cost, green environmental protection, etc., and has high early and long-term strength, crack resistance and durability, greatly reduces carbon emissions, and is suitable for large-scale popularization and application.

[0006] In a first aspect, the application provides a high-performance low-carbon concrete composite admixture, which adopts the following technical scheme: a high-performance low-carbon concrete composite admixture, by mass fraction, comprises the following preparation raw materials: portland cement 150-200 parts, blast furnace slag 200-250 parts, fly ash 400-450 parts, active wollastonite powder 100-120 parts, modified fiber 20-25 parts, additive 6-8 parts, high-efficiency water reducing agent 6-8 parts, and water 200-250 parts.

[0007] By adopting the above technical scheme, the silicate cement: as the main cementing material of concrete, provides the necessary strength and stability. Blast furnace slag and fly ash: these two materials as mineral admixtures, not only can replace part of the silicate cement to reduce carbon emissions, but also can improve the pore structure of concrete and improve its durability. Active wollastonite powder: further improve the strength and durability of concrete. Modified fiber: the compatibility of fiber and concrete matrix is enhanced by modification treatment, which improves the crack resistance and durability of concrete. At the same time, the use of this fiber also helps waste utilization. Admixtures and high efficiency water reducing agent: these additives can improve the workability of concrete, increase the early strength, and at the same time reduce the cement consumption and carbon emissions. The phenolic and alcoholic substances in the admixture can react with the active ingredients in the fly ash, further improving the strength and durability of the concrete. Water: as the solvent and reaction medium of concrete mixture. Mineral admixtures (blast furnace slag and fly ash) interact with silicate cement to improve the overall performance of concrete and reduce carbon emissions. Modified fiber interacts with mineral admixtures and silicate cement to improve the crack resistance and durability of concrete. Admixtures and high efficiency water reducing agent interact with mineral admixtures and silicate cement to improve the workability and early strength of concrete, while reducing the cement consumption and carbon emissions. In summary, the synergistic effect of these components in concrete not only improves the performance of concrete, but also realizes the double promotion of environmental protection and economic benefit.

[0008] Preferably, the preparation method of the modified fiber comprises the following steps:

[0009] S21, according to the mass fraction, 50 parts of chopped glass fiber is first placed in 200 parts of hydrochloric acid solution with a concentration of 80-100 g / L and heated to 50-55 ℃ for 3-4 h, then filtered, washed with water, and then placed in a 70 g / L sodium hydroxide solution for 60 min, then filtered, washed with water, and dried to obtain pretreated chopped glass fiber;

[0010] S22, according to the mass fraction, 100 parts of pretreated chopped glass fiber is dispersed in 300 parts of a solution composed of 100 parts of ethanol and 200 parts of water, then 3 parts of silane coupling agent and 40 parts of silicon crystal waste powder are added, and after stirring and dispersing, water is removed to obtain chopped glass fiber loaded with silicon crystal waste powder;

[0011] S23, according to the mass fraction, the chopped glass fiber loaded with silicon crystal waste powder is calcined at 900-1000 ℃ for 2-3 h under nitrogen protection to obtain modified fiber.

[0012] By adopting the technical scheme, when the modified fiber is prepared, the surface area of the chopped glass fiber particles is first treated with acid and alkali to enable the chopped glass fiber to stably load the silicon crystal waste powder; in addition, the addition of the silane coupling agent further strengthens the connection between the two, so as to finally prepare the stable modified fiber. The modified fiber significantly improves the strength and durability of the low-carbon concrete, is prepared by using chopped glass fiber and silicon crystal waste as raw materials to realize waste utilization; when the modified fiber is prepared, the silicon crystal waste powder is appropriately loaded on the pretreated chopped glass fiber, and the composite is activated by high-temperature calcination to obtain the modified fiber which has excellent compatibility with the low-carbon concrete system, so that the strength, crack resistance and durability of the low-carbon concrete are significantly improved.

[0013] Preferably, the silane coupling agent is one of γ-glycidoxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane; the length of the chopped glass fiber is 4-6 mm, and the diameter is 13-16 μm; the particle size of the silicon crystal waste powder is 20-30 μm.

[0014] Preferably, the high-efficiency water reducing agent is composed of modified polycarboxylic acid water reducing agent and aliphatic high-efficiency water reducing agent in a mass ratio of 3:2.

[0015] By adopting the above technical scheme, the modified polycarboxylic acid water reducing agent improves the pore structure of the concrete through its steric hindrance effect and dispersion performance, improves the compressive strength and crack resistance of the concrete, and improves the workability and early and long-term strength development of the concrete together with components such as Portland cement, blast furnace slag and fly ash. Reducing the cement dosage reduces carbon emissions and improves economic and environmental benefits. The aliphatic high-efficiency water reducing agent can further improve the workability of the concrete when used with the modified polycarboxylic acid water reducing agent. It helps to improve the fluidity and stability of the concrete. It helps to improve the early strength of the concrete. The combination of the two water reducing agents can take advantage of each other while complementing each other. The steric hindrance effect and dispersion performance of the modified polycarboxylic acid water reducing agent can be combined with the water reducing effect of the aliphatic high-efficiency water reducing agent to further improve the workability and strength of the concrete. By adjusting the ratio of the two water reducing agents, the performance of the concrete can be fine-tuned. In summary, the synergistic effect of the high-efficiency water reducing agent can effectively improve the comprehensive performance of the concrete, including workability, strength, crack resistance and durability. At the same time, by reducing the cement dosage and reducing carbon emissions, this combination also has good environmental and economic benefits.

[0016] Preferably, the preparation method of the modified polycarboxylic acid water reducing agent comprises the following steps:

[0017] S51, 18 mol of acrylic acid and 1 mol of vinyl triethoxysilane are added to 6 kg of water, and after stirring uniformly, a mixed solution A is obtained;

[0018] S52, add 0.5 mol of vitamin C and 0.9 mol of 3-mercapto propionic acid to 3 kg of water, stir until uniform to obtain mixed solution B; S53, add 0.8 mol of bisallyl alcohol capped polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether to 24 kg of water and stir, then add 1.2 mol of hydrogen peroxide, stir and heat to 49-53℃, then add mixed solution A and mixed solution B dropwise, 3h dropwise completion, continue to stir for 4-5h, then add NaOH aqueous solution to adjust the pH value to 6.5-7.0, to obtain the modified polycarboxylic acid water reducing agent.

[0019] By adopting the above technical scheme, the modified polycarboxylic acid water reducing agent prepared can effectively disperse cement particles through the steric hindrance effect in its molecular structure, reduce the flocculation phenomenon in the cement paste, and thus improve the workability of the concrete, i.e. the fluidity. By improving the pore structure of the concrete, the modified polycarboxylic acid water reducing agent helps to improve the compressive strength and crack resistance of the concrete. The improvement of the pore structure means that the interior of the concrete is more uniform and compact, reducing the generation and development of micro-cracks. The modified polycarboxylic acid water reducing agent can promote the early strength development of the concrete, while also helping to improve the long-term strength. This is because the water reducing agent can accelerate the speed of the cement hydration reaction, thereby improving the strength of the concrete. By improving the workability and strength of the concrete, the modified polycarboxylic acid water reducing agent helps to reduce the amount of cement used. This not only reduces the cost, but also reduces carbon emissions during the production of cement. The modified polycarboxylic acid water reducing agent, in combination with aliphatic high-efficiency water reducing agents and other components in the concrete (such as Portland cement, blast furnace slag, and fly ash, etc.), can further improve the performance of the concrete. For example, in combination with admixtures and high-efficiency water reducing agents, the doping effect of fly ash and blast furnace slag can be enhanced, improving the early strength of the concrete. By reducing the amount of cement used and improving the performance of the concrete, the modified polycarboxylic acid water reducing agent helps to achieve both economic and environmental benefits. This not only reduces production costs, but also reduces the impact on the environment. In summary, the modified polycarboxylic acid water reducing agent plays a crucial role in the preparation of concrete, not only improving the performance of the concrete, but also helping to achieve green and sustainable development.

[0020] Preferably, the admixture comprises the following preparation raw materials by mass fraction: 100 parts of hydroxyethyl acrylate, 0.2 parts of dicumyl peroxide, 19 parts of methoxy polyoxyethylene ether, 6 parts of methyldiethanolamine, 1 part of cetyltrimethylammonium hydroxide, 5 parts of dopamine, 110 parts of acetone, and 100 parts of water. The preparation method of the admixture is as follows: mix hydroxyethyl acrylate, dicumyl peroxide, methoxy polyoxyethylene ether, methyldiethanolamine, cetyltrimethylammonium hydroxide, dopamine, acetone, and water according to the mass fraction, heat to 45℃, and stir for 50 minutes to obtain the admixture.

[0021] By adopting the above technical solution, the phenolic substances and alcohol substances contained in the admixture can coordinate with the active components (such as iron ions and aluminum ions) in the fly ash and blast furnace slag, thereby destroying the surface glass structure of the fly ash and promoting the release of active SiO2 and active Al2O3. This helps to improve the reactivity of fly ash and blast furnace slag, making them participate in the hydration reaction more quickly, thereby improving the early strength of the concrete. The admixture can accelerate the release of active components of fly ash by dissolving the surface structure of fly ash particles, thereby partially replacing the role of Portland cement. This not only reduces the amount of cement, but also reduces the carbon emissions during the preparation of concrete. The various components in the admixture (such as hydroxyethyl acrylate and methoxy polyoxyethylene ether) help to improve the fluidity and plasticity of the concrete, making it easier to mix, transport and shape. This is of great significance for the large-scale promotion and application of high-performance low-carbon concrete. The components such as dopamine in the admixture can form stable chemical bonds with other components in the concrete, enhancing the microstructure stability of the concrete and improving its crack resistance and long-term durability. The phenolic substances combined with the superplasticizer greatly improve the dispersion ability of cement particles due to steric hindrance. This helps to reduce the agglomeration between cement particles and makes the cement particles more uniformly distributed in the concrete, thereby improving the overall performance of the concrete. The superplasticizer can significantly reduce the water-cement ratio of the concrete, and the admixture further optimizes the pore structure of the concrete, allowing for further reduction in water usage while maintaining the same fluidity. This helps to improve the density and strength of the concrete. The combined action of the admixture and the superplasticizer not only improves the early and long-term strength of the concrete, but also improves its crack resistance and durability. The admixture plays an important role in the preparation of high-performance low-carbon concrete and has a good synergistic effect with the superplasticizer. These effects collectively promote the improvement of the performance of the concrete, achieving the dual goals of economic and environmental benefits.

[0022] Preferably, the particle size of the active wollastonite powder is 325 mesh; and the fly ash is grade II fly ash.

[0023] Preferably, the Portland cement is P·O42.5 cement, and the particle size of the blast furnace slag ranges from 0.04 to 0.06 mm, and its chemical composition includes 35.6% CaO, 33.2% SiO2, 12.7% Al2O3, 9.2% MgO, 2.5% TiO2, 1.3% Fe2O3 and other substances.

[0024] In a second aspect, the application provides a preparation method of a high-performance low-carbon concrete composite admixture, which adopts the following technical solution:

[0025] As a general technical concept, the application also provides a preparation method of the high-performance low-carbon concrete composite admixture, comprising the following steps:

[0026] S101, according to the mass fraction, the portland cement, the blast furnace slag, the fly ash, the active anorthite powder, the modified fiber, the admixture and the superplasticizer are stirred uniformly, then the water is added and stirred for 2-3 minutes, to obtain a high-performance low-carbon concrete composite admixture slurry;

[0027] S102, the high-performance low-carbon concrete composite admixture slurry is molded and demolded, and then cured to obtain the high-performance low-carbon concrete composite admixture.

[0028] In summary, the application has the following beneficial technical effects:

[0029] 1. Low carbon and environmental protection: By using blast furnace slag and fly ash to replace part of the portland cement, the amount of cement and carbon emissions are reduced, achieving the goal of low carbon and environmental protection. At the same time, this substitution not only reduces the production cost, but also reduces the dependence on natural resources.

[0030] 2. Improve strength and durability: The use of modified fiber significantly improves the strength and durability of concrete. Modified fiber can effectively enhance the structural performance of concrete.

[0031] 3. Improve pore structure and crack resistance: The modified polycarboxylate superplasticizer improves the pore structure of concrete through its steric hindrance effect and dispersion performance, improving the compressive strength and crack resistance. At the same time, the use of this superplasticizer also promotes the early and long-term strength development of concrete.

[0032] 4. Improve workability and reduce cement consumption: The use of admixtures and superplasticizers improves the doping effect of fly ash and blast furnace slag, further reducing the amount of cement. At the same time, these additives can also improve the workability of concrete, reducing energy consumption and cost during preparation.

[0033] 5. Economic and environmental benefits: Through the comprehensive application of the above technical measures, the application not only improves the performance of concrete, but also realizes the double improvement of economic and environmental benefits. Specifically, it reduces production costs, reduces carbon emissions, and improves resource utilization efficiency. DETAILED DESCRIPTION

[0034] The embodiments of the application will be described in detail below with reference to the examples, but those skilled in the art will understand that the following examples are only used to illustrate the application and should not be regarded as limiting the scope of the application. If the specific conditions are not specified in the examples, the conventional conditions or the conditions recommended by the manufacturer are used. If the reagents or instruments used are not specified by the manufacturer, they are all conventional products that can be purchased on the market.

[0035] In the following examples, preparation examples, and preparation comparative examples, 1 part represents 1 kg, the fly ash is Grade II fly ash, the active wollastonite powder has a particle size of 325 mesh; the silicate cement is P·O42.5 cement, and the blast furnace slag has a particle size range of 0.04-0.06 mm, and its chemical composition includes 35.6% of CaO, 33.2% of SiO2, 12.7% of Al2O3, 9.2% of MgO, 2.5% of TiO2, 1.3% of Fe2O3, and other substances.

[0036] Preparation of modified fiber in preparation example 1

[0037] The preparation method of the modified fiber comprises the following steps:

[0038] S21, 50 parts of chopped glass fibers with a length of 4-6 mm and a diameter of 13-16 μm are first placed in 200 parts of a hydrochloric acid solution with a concentration of 90 g / L and heated to 53°C for 3.4 h, then filtered, washed with water, and then placed in a sodium hydroxide solution with a concentration of 70 g / L for 60 min, and then filtered, washed with water, and dried to obtain pretreated chopped glass fibers;

[0039] S22, 100 parts of the pretreated chopped glass fibers are dispersed in 300 parts of a solution composed of 100 parts of ethanol and 200 parts of water, then 3 parts of γ-methacryloxypropyltrimethoxysilane and 40 parts of silicon crystal waste powder with a particle size of 20-30 μm are added, and after stirring and dispersing, water is removed to obtain chopped glass fibers loaded with silicon crystal waste powder;

[0040] S23, the chopped glass fibers loaded with silicon crystal waste powder are calcined at 960°C for 2.5 h under nitrogen protection to obtain modified fibers.

[0041] Preparation of modified polycarboxylic acid water reducing agent in preparation example 2

[0042] The preparation method of the modified polycarboxylic acid water reducing agent comprises the following steps:

[0043] S51, 18 mol of acrylic acid and 1 mol of vinyl triethoxysilane are added to 6 kg of water, and after stirring uniformly, a mixed solution A is obtained;

[0044] S52, 0.5 mol of vitamin C and 0.9 mol of 3-mercaptopropionic acid are added to 3 kg of water, and after stirring uniformly, a mixed solution B is obtained;

[0045] S53. Add 0.8 mol of dielyl alcohol-terminated polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether to 24 kg of water and stir. Then add 1.2 mol of hydrogen peroxide, stir and heat to 53°C, and then add mixed solution A and mixed solution B dropwise. After the addition is completed in 3 hours, continue stirring and reacting for 4.5 hours. Then add NaOH aqueous solution to adjust the pH value to 6.6 to obtain the modified polycarboxylate superplasticizer.

[0046] Preparation of admixtures in Example 3

[0047] The additive, by mass parts, comprises the following raw materials: 100 parts hydroxyethyl acrylate, 0.2 parts dicumyl peroxide, 19 parts methoxy polyoxyethylene ether, 6 parts methyl diethanolamine, 1 part hexadecyltrimethylammonium hydroxide, 5 parts dopamine, 110 parts acetone, and 100 parts water. The additive is prepared by mixing hydroxyethyl acrylate, dicumyl peroxide, methoxy polyoxyethylene ether, methyl diethanolamine, hexadecyltrimethylammonium hydroxide, dopamine, acetone, and water according to the mass parts, heating to 45°C, and stirring for 50 minutes to obtain the additive.

[0048] Example 1

[0049] A high-performance low-carbon concrete composite admixture, by weight, comprises the following raw materials: 150 parts silicate cement, 200 parts blast furnace slag, 400 parts fly ash, 100 parts activated wollastonite powder, 20 parts modified fiber, 6 parts admixture, 6 parts high-efficiency water-reducing agent, and 200 parts water. The high-efficiency water-reducing agent is composed of modified polycarboxylate water-reducing agent and aliphatic high-efficiency water-reducing agent in a weight ratio of 3:2.

[0050] The preparation method of the above-mentioned high-performance low-carbon concrete composite admixture includes the following steps:

[0051] S101. According to the mass fractions, mix silicate cement, blast furnace slag, fly ash, active wollastonite powder, modified fiber, admixture and high-efficiency water-reducing agent evenly, then add water and mix for 2 minutes to obtain high-performance low-carbon concrete composite admixture slurry.

[0052] S102. The high-performance low-carbon concrete composite admixture slurry is molded, formed, and demolded, and then cured to obtain the high-performance low-carbon concrete composite admixture.

[0053] Example 2

[0054] A high-performance low-carbon concrete composite admixture comprises the following preparation raw materials in parts by mass: Portland cement 200 parts, blast furnace slag 250 parts, fly ash 450 parts, active wollastonite powder 120 parts, modified fiber 25 parts, additive 8 parts, high-efficiency water reducing agent 8 parts, and water 250 parts, wherein the high-efficiency water reducing agent is composed of modified polycarboxylic acid water reducing agent and aliphatic high-efficiency water reducing agent in a mass ratio of 3:2.

[0055] The preparation method of the high-performance low-carbon concrete composite admixture comprises the following steps:

[0056] S101, the Portland cement, blast furnace slag, fly ash, active wollastonite powder, modified fiber, additive and high-efficiency water reducing agent are uniformly stirred in parts by mass, and then water is added and stirred for 3 minutes to obtain high-performance low-carbon concrete composite admixture slurry;

[0057] S102, the high-performance low-carbon concrete composite admixture slurry is molded, shaped and demolded, and then cured to obtain the high-performance low-carbon concrete composite admixture.

[0058] Example 3

[0059] A high-performance low-carbon concrete composite admixture comprises the following preparation raw materials in parts by mass: Portland cement 180 parts, blast furnace slag 220 parts, fly ash 430 parts, active wollastonite powder 110 parts, modified fiber 23 parts, additive 7 parts, high-efficiency water reducing agent 7 parts, and water 230 parts, wherein the high-efficiency water reducing agent is composed of modified polycarboxylic acid water reducing agent and aliphatic high-efficiency water reducing agent in a mass ratio of 3:2.

[0060] The preparation method of the high-performance low-carbon concrete composite admixture comprises the following steps:

[0061] S101, the Portland cement, blast furnace slag, fly ash, active wollastonite powder, modified fiber, additive and high-efficiency water reducing agent are uniformly stirred in parts by mass, and then water is added and stirred for 3 minutes to obtain high-performance low-carbon concrete composite admixture slurry;

[0062] S102, the high-performance low-carbon concrete composite admixture slurry is molded, shaped and demolded, and then cured to obtain the high-performance low-carbon concrete composite admixture.

[0063] Comparative Example 1

[0064] The same as example 3, except that equal amounts of short-cut glass fibers with a length of 4-6 mm and a diameter of 13-16 μm are used instead of the modified fiber.

[0065] Comparative Example 2

[0066] The same as example 3, except that the high-performance water-reducing agent is a modified polycarboxylic acid water-reducing agent.

[0067] Comparative example 3

[0068] The same as example 3, except that the high-performance water-reducing agent is an aliphatic high-performance water-reducing agent.

[0069] Comparative example 4

[0070] The same as example 3, except that the admixture is 0 parts and the high-performance water-reducing agent is 8 parts.

[0071] Comparative example 5

[0072] The same as example 3, except that the admixture is 8 parts and the high-performance water-reducing agent is 0 parts.

[0073] Performance test

[0074] The high-performance low-carbon concrete composite admixture prepared in examples 1-3 and comparative examples 1-5 was made into test pieces, the test pieces were cubic with a side length of 150 mm, the surface was sealed with a polyethylene film, and after 24 h of room temperature curing, the test pieces were removed from the mold, moved to a standard curing box for curing until the corresponding age, and the following tests were performed, and the test results are shown in Table 1.

[0075] Compressive strength: tested in accordance with the relevant provisions of GB / T 50081-2019 “Standard Test Methods for Physical and Mechanical Properties of Ordinary Concrete”;

[0076] Durability test: the product was tested for durability in accordance with GB / T 50082-2009 “Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete”;

[0077] Shrinkage: the 28d shrinkage value was detected according to the shrinkage test in GBJ82-85 “Standard Test Methods for Long-Term Performance and Durability of Ordinary Concrete”, in addition, the crack condition on the crack surface of the test piece was detected.

[0078] Table 1 Performance test

[0079] Item 7 d compressive strength / MPa 28 d compressive strength / MPa 28 d shrinkage / % Number of cracks / root / m 2 ]] Example 1 82.3 99.4 0.019 0.5 Example 2 83.6 101.3 0.015 0.5 Example 3 85.6 104.8 0.012 0.5 Comparative Example 1 72.4 83.2 0.031 2 0.5 81.2 98.5 0.23 Comparative Example 2 0.5 79.3 94.3 0.26 1 Comparative Example 3 76.7 88.7 0.27 5 0.5 Comparative Example 4 0.5 Comparative Example 5 0.5 78.2 91.2 0.28 3

[0080] Analyzing the data in Table 1, it can be seen that:

[0081] 1) The high-performance low-carbon concrete composite admixture prepared in examples 1-3 has high early and long-term strength, crack resistance and durability, significantly reduces carbon emissions, and is suitable for large-scale popularization and application.

[0082] 2) The performance comparison analysis of the high-performance low-carbon concrete composite admixture prepared by combining Example 3 and Comparative Example 1 shows that the modified fiber prepared in the application significantly improves the strength and durability of the low-carbon concrete, is prepared from short-cut glass fiber and silicon crystal waste as raw materials to realize waste utilization; in the preparation of the modified fiber, the silicon crystal waste powder is appropriately loaded on the modified fiber, and the composite is activated by high-temperature calcination to obtain the modified fiber with excellent compatibility with the low-carbon concrete system, so that the strength, crack resistance and durability of the low-carbon concrete are significantly improved.

[0083] 3) The performance comparison analysis of the high-performance low-carbon concrete composite admixture prepared by combining Example 3 and Comparative Example 2-Comparative Example 3 shows that the high-efficiency water-reducing agent is composed of modified polycarboxylate superplasticizer and aliphatic high-efficiency water-reducing agent in a mass ratio of 3:2. The modified polycarboxylate superplasticizer improves the pore structure of the concrete through its steric hindrance effect and dispersion performance, thereby improving the compressive strength and crack resistance of the concrete. In combination with components such as Portland cement, blast furnace slag and fly ash, the working property and early and long-term strength development of the concrete are improved. The cement dosage is reduced, carbon emissions are reduced, and economic and environmental benefits are improved. The use of aliphatic high-efficiency water-reducing agent in combination with modified polycarboxylate superplasticizer can further improve the workability of the concrete, which is helpful to improve the fluidity and stability of the concrete and to improve the early strength of the concrete. The combination of the two types of water-reducing agents can take advantage of each other while complementing each other's shortcomings. The steric hindrance effect and dispersion performance of the modified polycarboxylate superplasticizer can be combined with the water-reducing effect of the aliphatic high-efficiency water-reducing agent to further improve the workability and strength of the concrete. In summary, the synergistic effect of the high-efficiency water-reducing agent can effectively improve the comprehensive performance of the concrete, including workability, strength, crack resistance and durability. At the same time, by reducing the cement dosage and reducing carbon emissions, this combination also has good environmental and economic benefits.

[0084] 4) The performance comparison analysis of the high-performance low-carbon concrete composite admixture prepared by combining Example 3 and Comparative Example 4-Comparative Example 5 shows that the admixtures and high-efficiency water-reducing agents contained in the application have good cooperation effect, improve the doping effect of fly ash and blast furnace slag, further reduce the dosage of cement, and improve the early strength of the concrete. Specifically, the water-reducing agent can destroy the surface glass body of the fly ash, improve the leaching of valuable elements, and the phenolic substances in the admixture can form coordination with the leached iron ions and aluminum ions, thereby dissolving the surface structure of the fly ash particles, so that the fly ash or blast furnace slag powder releases active SiO2 and active Al2O3 more quickly, thereby activating the fly ash. Compared with alcohol substances, phenolic substances cooperate with water-reducing agents to greatly improve the dispersion capacity of cement particles due to steric hindrance, which can effectively reduce the cement dosage in the preparation of concrete and effectively reduce the carbon emissions of concrete. At the same time, the strength, crack resistance and durability of the low-carbon concrete are improved.

[0085] The above examples are only used to explain the technical solutions of the present application and not to limit them. Although the above examples have been specifically described, relevant technicians should understand that the specific embodiments of the present application can be modified or replaced by equivalents without departing from the spirit and scope of the present application, and any modification and equivalent replacement should be covered in the protection scope of the present application.

Claims

1. A high performance low carbon concrete composite admixture, characterized by, The preparation raw materials include, in terms of mass fraction, 150-200 parts of Portland cement, 200-250 parts of blast furnace slag, 400-450 parts of fly ash, 100-120 parts of active wollastonite powder, 20-25 parts of modified fiber, 6-8 parts of additive, 6-8 parts of high-efficiency water reducing agent, and 200-250 parts of water; the modified fiber is prepared by the method comprising the following steps: S21, 50 parts of chopped glass fiber is first placed in 200 parts of hydrochloric acid solution with a concentration of 80-100 g / L and heated to 50-55℃ for 3-4 hours, then filtered, washed with water, and placed in a sodium hydroxide solution with a concentration of 70 g / L for 60 minutes, and then filtered, washed with water, and dried to obtain pretreated chopped glass fiber; S22, 100 parts of pretreated chopped glass fiber is dispersed in 300 parts of a solution composed of 100 parts of ethanol and 200 parts of water, then 3 parts of silane coupling agent and 40 parts of silicon crystal waste powder are added, and after stirring and dispersing, water is removed to obtain chopped glass fiber loaded with silicon crystal waste powder; S23, the chopped glass fiber loaded with silicon crystal waste powder is calcined at 900-1000℃ for 2-3 hours under nitrogen protection to obtain modified fiber.

2. The high performance low carbon concrete composite admixture according to claim 1, characterized in that, The silane coupling agent is one of γ-glycidyloxypropyltrimethoxysilane and γ-methacryloyloxypropyltrimethoxysilane; the length of the chopped glass fiber is 4-6 mm, and the diameter is 13-16 μm; the particle size of the silicon crystal waste powder is 20-30 μm.

3. The high performance low carbon concrete composite admixture according to claim 1, wherein, The high-efficiency water reducing agent is composed of modified polycarboxylic acid water reducing agent and aliphatic high-efficiency water reducing agent in a mass fraction ratio of 3:

2.

4. The high performance low carbon concrete composite admixture according to claim 3, characterized in that, The preparation method of the modified polycarboxylic acid water reducing agent comprises the following steps: S51, 18 mol of acrylic acid and 1 mol of vinyl triethoxysilane are added to 6 kg of water, and after stirring uniformly, a mixed solution A is obtained; S52, 0.5 mol of vitamin C and 0.9 mol of 3-mercaptopropionic acid are added to 3 kg of water, and after stirring uniformly, a mixed solution B is obtained; S53, 0.8 mol of bisallyl alcohol-terminated polyoxyethylene ether and 6 mol of oleyl alcohol polyoxyethylene (10) ether are added to 24 kg of water and stirred, then 1.2 mol of hydrogen peroxide is added, and after stirring and heating to 49-53℃, the mixed solution A and the mixed solution B are added dropwise, and after 3 hours of dropwise addition, the stirring is continued for 4-5 hours, then a NaOH aqueous solution is added to adjust the pH value to 6.5-7.0, and the modified polycarboxylic acid water reducing agent is obtained.

5. The high performance low carbon concrete composite admixture according to claim 1, wherein, The additive includes, in terms of mass fraction, the following preparation raw materials: 100 parts of hydroxyethyl acrylate, 0.2 parts of dicumyl peroxide, 19 parts of methoxy polyoxyethylene ether, 6 parts of methyldiethanolamine, 1 part of hexadecyltrimethylammonium hydroxide, 5 parts of dopamine, 110 parts of acetone, and 100 parts of water.

6. The high performance low carbon concrete composite admixture according to claim 5, wherein, The preparation method of the additive comprises the following steps: mixing hydroxyethyl acrylate, dicumyl peroxide, methoxy polyoxyethylene ether, methyldiethanolamine, cetyltrimethylammonium hydroxide, dopamine, acetone and water according to mass fractions, heating to 45 DEG C, and stirring for 50 minutes to obtain the additive.

7. The high performance low carbon concrete composite admixture according to claim 1, wherein, The active wollastonite powder has a particle size of 325 mesh; and the fly ash is grade II fly ash.

8. The high performance low carbon concrete composite admixture according to claim 1, wherein, The silicate cement is P.O 42.5 cement, the particle size of the blast furnace slag ranges from 0.04 mm to 0.06 mm, and the chemical composition of the blast furnace slag comprises 35.6% of CaO, 33.2% of SiO2, 12.7% of Al2O3, 9.2% of MgO, 2.5% of TiO2, 1.3% of Fe2O3 and other substances.

9. A method for preparing the high-performance low-carbon concrete composite admixture according to any one of claims 1-8, characterized in that, The method comprises the following steps: S101, mixing silicate cement, blast furnace slag, fly ash, active wollastonite powder, modified fiber, additive and high-efficiency water reducing agent according to mass fractions, and stirring uniformly, then adding water and stirring for 2-3 minutes to obtain high-performance low-carbon concrete composite admixture slurry; S102, molding the high-performance low-carbon concrete composite admixture slurry, demolding and continuing curing to obtain the high-performance low-carbon concrete composite admixture.