Green cement substitute material and preparation method thereof
By combining modified fly ash and modified slag with metakaolin, a green cement substitute material was prepared, which solved the problem of efflorescence of cement-based materials in underwater environments, and achieved early activity enhancement and performance improvement, which meets the development needs of green and low-carbon transformation.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- XIAN UNIV OF TECH
- Filing Date
- 2026-05-25
- Publication Date
- 2026-06-19
AI Technical Summary
Existing cement-based materials are prone to efflorescence in underwater environments, which leads to a decrease in structural durability. Furthermore, existing mineral admixtures have problems such as early activity mismatch, increased water demand, and shrinkage cracking risk when used in combination.
By combining modified fly ash and modified slag with metakaolin, the early activity and stability of the material are improved through modification treatment, and a green cement substitute material is prepared. The positive and negative charge interaction between fly ash and modified slag is utilized to achieve more efficient performance improvement.
It significantly reduces cement consumption, improves the early strength of concrete, reduces efflorescence, and enhances the performance and durability of concrete, which aligns with the development direction of green and low-carbon transformation.
Smart Images
Figure CN122233730A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of cement material preparation technology, specifically a green cement substitute material and its preparation method. Background Technology
[0002] Concrete is the most widely used building material in global infrastructure construction, with an annual global production exceeding 30 billion tons in 2025. Hydropower projects are one of the core application scenarios for concrete materials. Hydraulic concrete structures such as dams, aqueducts, underwater culverts, and canal linings are subjected to extreme service environments involving underwater immersion, alternating wet and dry conditions, and high water pressure corrosion. Their durability and long-term service safety directly affect the stability of river basin flood control, water resource allocation, and energy production. Among the many durability defects in hydraulic concrete, efflorescence has become a key factor restricting the long service life of structures, and the engineering problems it causes are prevalent in global water conservancy projects.
[0003] Efflorescence in concrete refers to the physicochemical process in which soluble calcium and hydroxide ions from within the cement paste migrate with moisture to the material surface, reacting with atmospheric CO2 to form a white calcium carbonate precipitate. Traditionally, efflorescence was considered merely an superficial defect affecting the structural appearance. However, recent research and engineering practice have confirmed that efflorescence is essentially an irreversible process involving the decomposition of hydration products within cement-based materials, continuous dissolution of calcium ions, and deterioration of the pore structure. For hydraulic concrete operating in a saturated environment for extended periods, continuous capillary action provides a constant driving force for ion migration, accelerating the efflorescence process. This leads to gel phase decomposition, deterioration of the interfacial transition zone, and the propagation of microcracks, ultimately resulting in a decline in the mechanical properties and impermeability of the concrete. It can even induce serious engineering defects such as steel corrosion, structural joint leakage, and concrete surface spalling.
[0004] In the field of efflorescence suppression technology, replacing cement clinker with mineral admixtures is currently recognized as a fundamental solution. These admixtures consume Ca(OH)2 produced during cement hydration through pozzolanic reaction, generating stable hydrated calcium silicate (CSH) and hydrated calcium aluminosilicate (CASH) gels, thus reducing the material basis for efflorescence at its source. Existing research has confirmed that single-use admixtures such as fly ash (FA), metakaolin (MK), and blast furnace slag (SL) all have certain efflorescence suppression effects. Moreover, from the perspective of solid waste resource utilization, FA and SL are the main industrial solid wastes emitted by my country's power and steel industries. In 2024, my country's annual fly ash emissions exceeded 600 million tons, and blast furnace slag emissions exceeded 350 million tons, while the comprehensive utilization rate of solid waste still has considerable room for improvement. MK, prepared from low-temperature calcined kaolin, is a commonly used auxiliary cementitious material in high-performance concrete. Replacing cement clinker with a mixture of three types of materials not only enables large-scale, high-value utilization of industrial solid waste, but also significantly reduces carbon emissions and energy consumption during cement production. This aligns with the green and low-carbon transformation of my country's building materials industry and has significant environmental benefits.
[0005] However, single admixtures have significant performance shortcomings: although MK has high early-age activity, excessive addition will significantly increase the water demand of concrete and the risk of shrinkage cracking; FA has good micro-aggregate filling effect and later-age activity, but its early-age hydration is slow and cannot effectively inhibit early efflorescence of concrete; SL can promote gel phase formation, but high dosage will lead to an increase in the calcium-silicon ratio of the gel phase and a decrease in stability; in addition, even when they are mixed, there are some defects, such as SL participating too early in the early hydration process, which leads to further aggravation of efflorescence, and MK having high early-age activity and consuming too much alkali, which leads to slower later-age hydration of FA.
[0006] Therefore, in response to the pain points of these materials, those skilled in the art have proposed a method to combine the properties of various materials such as MK, FA, and SL to prepare a green cement substitute with superior performance. Summary of the Invention
[0007] The purpose of this invention is to provide a green cement substitute material and its preparation method to solve the problems mentioned in the background art.
[0008] To achieve the above objectives, the present invention provides the following technical solution: A green cement substitute material, comprising the following components by weight: 210-470 parts cement, 96-160 parts modified fly ash, 71-82 parts metakaolin, 710-730 parts fine aggregate, 1100-1150 parts coarse aggregate, and 190-210 parts water. The modified fly ash is obtained by combining fly ash and modified slag. The specific steps for combining fly ash and modified slag are as follows: S101. The modified slag is placed in hydrogen peroxide and heated to 60-80℃ for 1-3 hours. After filtration, the filtered product is washed with deionized water and then vacuum dried at 50-60℃ to constant weight. S102. Disperse fly ash in anhydrous ethanol, then add a deionized aqueous solution of γ-aminopropyltriethoxysilane, heat and react at 60-80℃ for 2-3 hours, then filter, wash the filtered product with deionized water and dry it under vacuum at 50-60℃ to constant weight. S103. Add the modified slag treated in step S101 and the fly ash treated in step S102 to deionized water, then add sodium carboxymethyl cellulose, stir continuously for 0.5-1 h, and then rotary evaporate to constant weight to obtain modified fly ash.
[0009] Furthermore, in step S101, the concentration of hydrogen peroxide is 25 wt%, and the mass ratio between modified slag and hydrogen peroxide is 1:15.
[0010] Furthermore, in step S102, the mass ratio between fly ash, anhydrous ethanol, and the deionized aqueous solution of γ-aminopropyltriethoxysilane is 1:(10-20):(2-6), and the concentration of γ-aminopropyltriethoxysilane in the deionized aqueous solution of γ-aminopropyltriethoxysilane is 2wt%.
[0011] Furthermore, in step S103, the mass ratio of modified slag, fly ash, deionized water and carboxymethyl cellulose is 1:(2-4):(10-15):(0.05-0.1).
[0012] Furthermore, the preparation method of the modified slag includes the following steps: S201. Add the slag to the container and spray a sodium silicate solution containing acidic silica sol onto the surface of the slag while stirring. S202. While stirring, raise the temperature to 40-50℃ and continue to spray acetic acid solution onto the slag surface that has been sprayed with sodium silicate solution. After spraying is complete, continue stirring for 40-80 minutes. S203. The slag treated in step S202 is dried at 110-150℃ for 3-4 hours. After washing the product with deionized water, it is dried at 110-150℃ to constant weight to obtain modified slag.
[0013] Furthermore, in step S201, the mass ratio between the slag and the sodium silicate solution containing acidic silica sol is (2-4):1.
[0014] Furthermore, in step S201, the sodium silicate solution containing acidic silica sol is obtained by mixing sodium silicate solution and acidic silica sol. The concentration of sodium silicate in the sodium silicate solution containing acidic silica sol is 2-6 wt%, the concentration of acidic silica sol in the sodium silicate solution containing acidic silica sol is 5-10 wt%, and the concentration of silica in the acidic silica sol is 30 wt%.
[0015] Furthermore, in step S202, the concentration of acetic acid in the acetic acid solution is 5 wt%, and the mass ratio between the acetic acid solution in step S202 and the sodium silicate solution containing acidic silica sol in step S201 is 1:(4-6).
[0016] A method for preparing a green cement substitute material, the method comprising the following steps: S1. Add modified fly ash and cement to water according to the mass ratio, stir evenly to obtain slurry; S2. Add metakaolin, fine aggregate and coarse aggregate to the slurry obtained in step S1 according to the mass proportions, and stir and mix evenly to obtain green cement substitute material.
[0017] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention uses fly ash, slag and metakaolin, which saves cement consumption and is a development direction for green and low-carbon transformation, with significant environmental benefits; 2. In this invention, fly ash, slag, and metakaolin are incorporated. Metakaolin has high early activity, which consumes ions in cement, thus improving the early strength of concrete and reducing efflorescence. The slag is modified by coating its surface with a material, which delays the time for the slag to participate in the cement reaction. This not only reduces early efflorescence in concrete, but also provides sufficient active material for the relatively inert fly ash, thereby improving the performance of concrete. 3. In this invention, fly ash and modified slag are compounded before being impregnated into cement-based materials. The slag and fly ash can be precisely matched to achieve more efficient performance improvement. The modified slag is treated with hydrogen peroxide, and the fly ash is treated with silane coupling agent. The two are combined and matched through the interaction of positive and negative charges. Attached Figure Description
[0018] Figure 1 This is a process flow diagram for preparing modified fly ash in this invention; Figure 2 This is a process flow diagram for preparing modified slag in this invention; Figure 3 This is a process flow diagram for preparing green cement substitute materials in this invention; Figure 4This is a photograph of the green cement substitute material efflorescence prepared in Example 1 of this invention. Figure 5 This is a photograph of the green cement substitute material efflorescence prepared in Comparative Example 1 of this invention. Figure 6 This is a photograph of the green cement substitute material efflorescence prepared in Comparative Example 2 of this invention. Figure 7 This is a physical image of the green cement substitute material efflorescence prepared in Comparative Example 3 of this invention. Detailed Implementation
[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0020] Please see Figures 1 to 7 The present invention provides: Example 1 A green cement substitute material, comprising the following components by weight: 3.6 kg cement, 1.2 kg modified fly ash, 0.78 kg metakaolin, 7.2 kg fine aggregate, 11.2 kg coarse aggregate, 2.0 kg water; The modified fly ash mentioned above is obtained by combining fly ash and modified slag. The specific steps for combining fly ash and modified slag are as follows: S101. Place 0.8 kg of modified slag in 12 kg of 25 wt% hydrogen peroxide and heat to 75°C for 2 hours. Then filter. Wash the filtered product with deionized water and vacuum dry it to constant weight at 55°C. S102. Disperse 1.5 kg of fly ash into 22.5 kg of anhydrous ethanol, then add 6 kg of 2 wt% deionized aqueous solution of γ-aminopropyltriethoxysilane, heat and react at 75 °C for 2.4 h, then filter, wash the filtered product with deionized water and dry it under vacuum at 55 °C to constant weight. S103. Add 0.45 kg of modified slag treated in step S101 and 1.4 kg of fly ash treated in step S102 to 5.4 kg of deionized water, then add 0.03 kg of sodium carboxymethyl cellulose, stir continuously for 0.6 h, and then rotary evaporate to constant weight to obtain modified fly ash.
[0021] The preparation method of the above-mentioned modified slag includes the following steps: S201. Add 0.8 kg of slag to a container and spray 0.26 kg of sodium silicate solution containing acidic silica sol onto the surface of the slag while stirring. In step S201 above, the sodium silicate solution containing acidic silica sol is obtained by mixing a sodium silicate solution and acidic silica sol. The concentration of sodium silicate in the sodium silicate solution containing acidic silica sol is 4 wt%, the concentration of acidic silica sol in the sodium silicate solution containing acidic silica sol is 8 wt%, and the concentration of silica in the acidic silica sol is 30 wt%. S202. While maintaining stirring, raise the temperature to 45°C and continue to spray 0.05 kg of 5 wt% acetic acid solution onto the slag surface that has been sprayed with sodium silicate solution. After spraying is complete, continue stirring for 50 min. S203. The slag treated in step S202 is dried at 120°C for 3.5 hours. After washing the product with deionized water, it is dried at 130°C to constant weight to obtain modified slag.
[0022] Example 2 A green cement substitute material, comprising the following components by weight: 2.1 kg cement, 0.96 kg modified fly ash, 0.71 kg metakaolin, 7.1 kg fine aggregate, 11 kg coarse aggregate, 1.9 kg water; The modified fly ash mentioned above is obtained by combining fly ash and modified slag. The specific steps for combining fly ash and modified slag are as follows: S101. Place 0.8 kg of modified slag in 12 kg of 25 wt% hydrogen peroxide and heat to 60°C for 1 hour. Then filter. Wash the filtered product with deionized water and vacuum dry to constant weight at 50°C. S102. Disperse 1.5 kg of fly ash into 15 kg of anhydrous ethanol, then add 3 kg of 2 wt% deionized aqueous solution of γ-aminopropyltriethoxysilane, heat and react at 60 °C for 2 h, then filter, wash the filtered product with deionized water and dry it under vacuum at 50 °C to constant weight. S103. Add 0.6 kg of modified slag treated in step S101 and 1.2 kg of fly ash treated in step S102 to 6 kg of deionized water, then add 0.03 kg of sodium carboxymethyl cellulose, stir continuously for 0.5 h, and then rotary evaporate to constant weight to obtain modified fly ash.
[0023] The preparation method of the above-mentioned modified slag includes the following steps: S201. Add 0.8 kg of slag to a container and spray 0.4 kg of sodium silicate solution containing acidic silica sol onto the surface of the slag while stirring. In step S201 above, the sodium silicate solution containing acidic silica sol is obtained by mixing a sodium silicate solution and acidic silica sol. The concentration of sodium silicate in the sodium silicate solution containing acidic silica sol is 2 wt%, the concentration of acidic silica sol in the sodium silicate solution containing acidic silica sol is 5 wt%, and the concentration of silica in the acidic silica sol is 30 wt%. S202. While maintaining stirring, raise the temperature to 40°C and continue to spray 0.1 kg of 5 wt% acetic acid solution onto the slag surface that has been sprayed with sodium silicate solution. After spraying is complete, continue stirring for 40 min. S203. The slag treated in step S202 is dried at 110°C for 3 hours. After washing the product with deionized water, it is dried at 110°C to constant weight to obtain modified slag.
[0024] Example 3 A green cement substitute material, comprising the following components by weight: 4.7 kg cement, 1.6 kg modified fly ash, 0.82 kg metakaolin, 7.3 kg fine aggregate, 11.5 kg coarse aggregate, 2.1 kg water; The modified fly ash mentioned above is obtained by combining fly ash and modified slag. The specific steps for combining fly ash and modified slag are as follows: S101. Place 0.8 kg of modified slag in 12 kg of 25 wt% hydrogen peroxide and heat to 80°C for 3 hours. Then filter. Wash the filtered product with deionized water and vacuum dry it to constant weight at 60°C. S102. Disperse 2.2 kg of fly ash into 44 kg of anhydrous ethanol, then add 13.2 kg of 2 wt% deionized aqueous solution of γ-aminopropyltriethoxysilane, heat and react at 80 °C for 3 h, then filter, wash the filtered product with deionized water and dry it under vacuum at 60 °C to constant weight. S103. Add 0.5 kg of modified slag treated in step S101 and 2.0 kg of fly ash treated in step S102 to 7.5 kg of deionized water, then add 0.05 kg of sodium carboxymethyl cellulose, stir continuously for 1 h, and then rotary evaporate to constant weight to obtain modified fly ash.
[0025] The preparation method of the above-mentioned modified slag includes the following steps: S201. Add 0.8 kg of slag to a container and spray 0.2 kg of sodium silicate solution containing acidic silica sol onto the surface of the slag while stirring. In step S201 above, the sodium silicate solution containing acidic silica sol is obtained by mixing a sodium silicate solution and acidic silica sol. The concentration of sodium silicate in the sodium silicate solution containing acidic silica sol is 6 wt%, the concentration of acidic silica sol in the sodium silicate solution containing acidic silica sol is 10 wt%, and the concentration of silica in the acidic silica sol is 30 wt%. S202. While maintaining stirring, raise the temperature to 50°C and continue to spray 0.033 kg of 5 wt% acetic acid solution onto the slag surface that has been sprayed with sodium silicate solution. After spraying is complete, continue stirring for 80 min. S203. The slag treated in step S202 is dried at 150°C for 4 hours. After washing the product with deionized water, it is dried at 150°C to constant weight to obtain modified slag.
[0026] The raw materials obtained in the above embodiments are used to prepare green cement substitutes through the following steps: S1. Add modified fly ash and cement to water, stir evenly to obtain slurry; S2. Add metakaolin, fine aggregate and coarse aggregate to the slurry obtained in step S1, and stir and mix evenly to obtain green cement substitute material.
[0027] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that the addition of modified fly ash was omitted from the components, that is, steps S101-S103 were completely omitted. The addition of modified fly ash in step S1 was also omitted, and instead, fly ash and modified slag were added. The total mass of modified slag and fly ash was 1.2 kg, and the mass ratio between modified slag and fly ash was 1:3.1. The remaining steps were exactly the same as those in Comparative Example 1.
[0028] Comparative Example 2 The difference between Comparative Example 2 and Comparative Example 1 is that fly ash and slag are added in step S1. The mass of slag and fly ash is exactly the same as that of modified slag and fly ash in Comparative Example 1. The remaining steps are exactly the same as those in Comparative Example 1.
[0029] Comparative Example 3 The difference between Comparative Example 3 and Example 1 is that the addition of metakaolin was completely eliminated in step S2, while the remaining steps are exactly the same as in Example 1.
[0030] The cement used in this invention is produced by Shaanxi Tongchuan Phoenix Building Materials Co., Ltd., with a specific surface area of 358 m². 2 / kg of PO 42.5 ordinary Portland cement; The fine aggregate used was natural river sand. The results of the sand sieve test are shown in Table 1. The fineness modulus was calculated to be 2.87, which is classified as medium sand. The apparent density was 2666 kg / m3, the loose bulk density was 1480 kg / m3, and the mud content was 2.4%. Table 1: Screening Table for Fine Aggregates The coarse aggregate used in this invention is natural crushed stone purchased from Xi'an, Shaanxi Province, China. The results of the crushed stone sieve analysis are shown in Table 2. The apparent density of the crushed stone, as tested, is 2750 kg / m³. 3 The loose bulk density is 1578 kg / m³, the porosity is 42%, and the mud content is 0.6%. Table 2: Screening Table for Coarse Aggregate The fly ash is Grade II fly ash produced by Henan Borun Foundry Materials Co., Ltd., with a sieve residue rate of 16% on a 45μm square mesh sieve. Its physical properties are as follows: density 2.23 g / cm³. 3 Loss on ignition 2.62%, moisture content 0.40%.
[0031] The metakaolin was purchased from a company in Gongyi City, Henan Province, China, with a fineness of 1250 mesh. The slag is an S105 grade product manufactured by Gongyi Longze Water Purification Materials Co., Ltd., with a density of 2.10 g / cm³. 3 The average particle size is 7.264 μm; The chemical compositions of fly ash, slag, and metakaolin are shown in Table 3 below: Table 3: Chemical Composition of Fly Ash, Slag, and Metakaolin The cement-based materials prepared in Examples 1-3 and Comparative Examples 1-3 were injected into molds. The specimens were cured under standard curing conditions (temperature 20℃±3℃, relative humidity ≥95%) for 3d, 7d and 28d respectively, and compressive strength tests were conducted. The TAW-2000 rock triaxial testing machine was used to carry out the concrete compressive strength test. The test process was carried out in accordance with the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081-2019)
[35] . The compressive strength test was carried out on 100mm×100mm×100mm cubic specimens. Each group of tests was conducted in parallel for 3 times, and the final compressive strength result was the arithmetic mean of the test values of the 3 specimens.
[0032] The experimental results are shown in Table 4 below: Table 4: Compressive strength test results of concrete prepared in Examples 1-3 and Comparative Examples 1-3 As can be seen from the data in Table 4 above, the early strength of Comparative Example 3 is significantly lower than that of Example 1. This is due to the lack of metakaolin and the resulting decrease in early activity. Comparative Example 1 lacks the operation of combining slag and fly ash, and the concrete also shows a significant decrease in strength. Comparative Example 2 further lacks the improvement of slag, which is prone to participating in the reaction too early. This not only leads to more severe efflorescence, but the fly ash may also have alkali deficiency in the later activation stage, further reducing the strength of the resulting concrete.
[0033] in addition, Figure 4-7 The figures show the whitening of the concrete surfaces prepared in Examples 1 and 1-3, respectively. It is clear from the figures that the efflorescence on the surfaces of Comparative Examples 2 and 3 is much more pronounced than that in Example 1. In Comparative Example 2, the lack of slag coating on the surface led to a faster reaction of the slag, providing more alkali to the concrete and causing severe efflorescence. In Comparative Example 3, the lack of kaolin added resulted in a lack of early-stage active materials to consume the alkali in the cement, also causing severe efflorescence. The degree of efflorescence in Comparative Example 1 was not much more severe than that in Example 1. This is because Comparative Example 1 also modified the surface of the slag to prevent premature reaction of the slag in the cement, thereby reducing efflorescence.
[0034] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.
Claims
1. A green cement substitute material, characterized in that, Materials comprising the following components by weight: 210-470 parts cement, 96-160 parts modified fly ash, 71-82 parts metakaolin, 710-730 parts fine aggregate, 1100-1150 parts coarse aggregate, and 190-210 parts water. The modified fly ash is obtained by combining fly ash and modified slag. The specific steps for combining fly ash and modified slag are as follows: S101. The modified slag is placed in hydrogen peroxide and heated to 60-80℃ for 1-3 hours. After filtration, the filtered product is washed with deionized water and then vacuum dried at 50-60℃ to constant weight. S102. Disperse fly ash in anhydrous ethanol, then add a deionized aqueous solution of γ-aminopropyltriethoxysilane, heat and react at 60-80℃ for 2-3 hours, then filter, wash the filtered product with deionized water and dry it under vacuum at 50-60℃ to constant weight. S103. Add the modified slag treated in step S101 and the fly ash treated in step S102 to deionized water, then add sodium carboxymethyl cellulose, stir continuously for 0.5-1 h, and then rotary evaporate to constant weight to obtain modified fly ash.
2. The green cement substitute material according to claim 1, characterized in that, In step S101, the concentration of hydrogen peroxide is 25 wt%, and the mass ratio between modified slag and hydrogen peroxide is 1:
15.
3. The green cement substitute material according to claim 1, characterized in that, In step S102, the mass ratio between fly ash, anhydrous ethanol and the deionized aqueous solution of γ-aminopropyltriethoxysilane is 1:(10-20):(2-6), and the concentration of γ-aminopropyltriethoxysilane in the deionized aqueous solution of γ-aminopropyltriethoxysilane is 2wt%.
4. The green cement substitute material according to claim 1, characterized in that, In step S103, the mass ratio of modified slag, fly ash, deionized water and carboxymethyl cellulose is 1:(2-4):(10-15):(0.05-0.1).
5. The green cement substitute material according to claim 1, characterized in that, The method for preparing the modified slag includes the following steps: S201. Add the slag to the container and spray a sodium silicate solution containing acidic silica sol onto the surface of the slag while stirring. S202. While stirring, raise the temperature to 40-50℃ and continue to spray acetic acid solution onto the slag surface that has been sprayed with sodium silicate solution. After spraying is complete, continue stirring for 40-80 minutes. S203. The slag treated in step S202 is dried at 110-150℃ for 3-4 hours. After washing the product with deionized water, it is dried at 110-150℃ to constant weight to obtain modified slag.
6. The green cement substitute material according to claim 5, characterized in that, In step S201, the mass ratio between the slag and the sodium silicate solution containing acidic silica sol is (2-4):
1.
7. The green cement substitute material according to claim 5, characterized in that, In step S201, the sodium silicate solution containing acidic silica sol is obtained by mixing sodium silicate solution and acidic silica sol. The concentration of sodium silicate in the sodium silicate solution containing acidic silica sol is 2-6 wt%, the concentration of acidic silica sol in the sodium silicate solution containing acidic silica sol is 5-10 wt%, and the concentration of silica in the acidic silica sol is 30 wt%.
8. The green cement substitute material according to claim 5, characterized in that, The concentration of acetic acid in the acetic acid solution in step S202 is 5 wt%, and the mass ratio between the acetic acid solution in step S202 and the sodium silicate solution containing acidic silica sol in step S201 is 1:(4-6).
9. A method for preparing a green cement substitute material as described in any one of claims 1-8, characterized in that, The preparation method includes the following steps: S1. Add modified fly ash and cement to water according to the mass ratio, stir evenly to obtain slurry; S2. Add metakaolin, fine aggregate and coarse aggregate to the slurry obtained in step S1 according to the mass proportions, and stir and mix evenly to obtain green cement substitute material.