Low-carbon concrete nano C-A-S-H seed crystal enhancer and preparation method thereof

Abstract

The invention discloses a low-carbon concrete nano C-A-S-H seed crystal enhancer as well as a preparation method and application thereof. The reinforcing agent comprises the following raw materials in parts by weight: 150-200 parts of water, 20-25 parts of sodium silicate nonahydrate, 15-20 parts of calcium nitrate tetrahydrate, 5-8 parts of aluminum nitrate nonahydrate, 1-4 parts of a polycarboxylate superplasticizer, 1-4 parts of sodium hydroxide, 0.5-2 parts of a silane coupling agent and 0.5-2 parts of a sodium polyacrylate dispersing agent. The preparation method comprises the steps of dissolution, precipitation reaction, dispersion modification and pH adjustment. According to the invention, by optimizing the molar ratio of silicon to aluminum and constructing a composite dispersion system, the technical problems of easy agglomeration, poor stability and poor compatibility with a water reducing agent of the nano seed crystal are solved. When 0.5-2% of the additive is applied to concrete, the early strength can be remarkably improved, the workability maintenance can be improved, the activity of solid wastes such as fly ash and the like can be effectively excited, and a key technical support is provided for preparing high-performance low-carbon concrete.

Description

Technical Field

[0001] This invention belongs to the field of building materials technology, specifically relating to a nano-CASH seed crystal reinforcing agent for improving the early strength of cement-based materials and promoting the utilization of industrial solid waste, its preparation method, and its application in low-carbon concrete. Background Technology

[0002] Nano-CASH seed crystal reinforcement, as a novel early-strength technology for cement-based materials, has attracted widespread attention due to its ability to effectively promote cement hydration and significantly improve the early strength of concrete. Improving early strength is crucial for accelerating formwork turnover, shortening construction periods, and especially for ensuring project progress in low-temperature environments, aligning with the modern trend towards high efficiency and energy conservation in construction engineering.

[0003] However, the preparation and application of nano-CASH seeds in existing technologies still face many challenges. First, traditional synthesis methods often focus on the calcium-silicon (CSH) system, with insufficient introduction of aluminum and control over its role in the seed structure. This results in limited nucleation effects, poor adaptability to low-carbon cementitious systems rich in aluminum phases (such as fly ash and mineral powder), and unsatisfactory reinforcing effects. Second, nano-seeds synthesized under existing formulations and processes exhibit poor dispersion stability, easily agglomerating and settling. This not only reduces the effective utilization rate of the seeds but also leads to uneven distribution in concrete, even clogging pump pipes, severely affecting construction performance and the stability of reinforcing effects.

[0004] Current mainstream seed crystal preparation technologies have significant limitations: First, the order of addition of each component, pH environment, and stirring conditions during the synthesis process are poorly controlled, making it difficult to precisely regulate the nanoscale structure and surface properties of the seed crystals, resulting in poor product uniformity. Second, excessive dispersants or regulators are often introduced to maintain stability, which may delay the main process of cement hydration or introduce harmful ions, potentially negatively impacting the long-term durability of concrete. Third, the compatibility of existing seed crystals with modern high-performance water-reducing agents (such as polycarboxylate superplasticizers PCE) is not well studied, and the synergistic mechanism between the two is unclear, which can easily lead to excessively rapid loss of concrete workability over time.

[0005] Furthermore, existing technologies often focus on the single indicator of strength improvement, while neglecting the systematic consideration of the low-carbon effects brought about by seed technology (such as increasing the amount of industrial solid waste incorporated). Conventional reinforcement methods often achieve this by increasing the amount of cement with a high carbon footprint, which runs counter to the urgent need for green and low-carbon development in the global construction industry. Therefore, the industry urgently needs to develop a highly efficient nanocrystalline seed reinforcement agent and its preparation method that has a stable synthesis process, good dispersibility, excellent compatibility with modern chemical raw materials, and can effectively serve low-carbon cementitious systems, in order to achieve a synergistic improvement in the early strength and long-term durability, as well as high performance and greening of concrete. Summary of the Invention

[0006] The core technical problem to be solved by this invention is to overcome the defects of existing technologies, such as easy agglomeration and sedimentation of nano-CASH seeds, poor dispersibility in concrete, poor compatibility with modern water-reducing agents, and unstable early strength improvement effect on low-carbon cementitious systems.

[0007] To address the aforementioned issues, this invention provides a nano-CASH seed crystal reinforcing agent with innovative composition and process. This reinforcing agent, by introducing an aluminum source and optimizing the silicon-aluminum molar ratio, constructs a more efficient crystal nucleus structure. Simultaneously, through the synergistic effect of specific dispersants and surface modifiers, it significantly improves the dispersion stability of nanoparticles, enabling them to be uniformly and stably distributed in cement paste. This not only serves as a template for hydration crystallization, greatly accelerating early hydration, but also demonstrates good compatibility with polycarboxylate superplasticizers, achieving the dual effect of improving early strength and maintaining workability.

[0008] Another objective of this invention is to provide a method for preparing the aforementioned nano-CASH seed crystal enhancer. This method ensures the synthesis of nano-seed crystals with uniform size and high stability by precisely controlling the order of reactant addition, pH environment, and dispersion process. Furthermore, the process conditions are mild and easily scaled up for industrial production.

[0009] Another objective of this invention is to provide the application of the aforementioned nano-CASH seed crystal reinforcing agent in low-carbon concrete. By adding a small amount of this reinforcing agent (e.g., 0.5%-2% of the cement mass), the early strength of concrete within one day can be significantly improved, thereby allowing for a reduction in cement usage or an increase in the amount of industrial solid waste such as fly ash and mineral powder. This provides key technical support for the formulation of high-performance low-carbon concrete, ultimately serving the energy conservation, emission reduction, and green sustainable development of the construction industry.

[0010] The present invention includes the following technical solutions.

[0011] A low-carbon concrete nano-CASH seed crystal reinforcing agent, the raw materials comprising, by weight:

[0012]

[0013] Sodium polyacrylate dispersant 0.5-2 parts.

[0014] Furthermore, in the aforementioned low-carbon concrete nano-CASH seed crystal reinforcing agent, the molar ratio of sodium silicate nonahydrate to aluminum nitrate nonahydrate, calculated as silicon and aluminum, is 4.5:1 to 5.5:1.

[0015] Furthermore, in the aforementioned low-carbon concrete nano-CASH seed crystal reinforcing agent, the polycarboxylate superplasticizer is an ester-based polycarboxylate superplasticizer with a number-average molecular weight of 5000-20000 g / mol and a water reduction rate of ≥25%.

[0016] Furthermore, in the aforementioned low-carbon concrete nano-CASH seed crystal reinforcing agent, the silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

[0017] This invention also discloses a method for preparing the above-mentioned low-carbon concrete nano-CASH seed crystal reinforcement, comprising the following steps:

[0018] (1) Dissolution: Mix water, sodium hydroxide, sodium silicate nonahydrate and aluminum nitrate nonahydrate, and stir at 40-60℃ for 10-20 minutes to obtain mixture A;

[0019] (2) Precipitation reaction: Add calcium nitrate tetrahydrate to mixture A and stir at 500-800 r / min for 30-60 minutes to generate CASH precipitate;

[0020] (3) Dispersion modification: Add polycarboxylate superplasticizer, silane coupling agent and sodium polyacrylate dispersant, and disperse at high speed at 1000-1500 r / min for 1-2 hours;

[0021] (4) pH adjustment: The pH of the system was adjusted to 12.5-13.5 with sodium hydroxide solution to obtain nano CASH seed enhancer.

[0022] Furthermore, in the above preparation method, the high-speed dispersion in step (3) adopts a disc-type sawtooth dispersion disc, the ratio of the dispersion disc diameter to the container diameter is 1:3-1:5, and the temperature is controlled to be ≤50℃.

[0023] This invention also discloses the application of the above-mentioned low-carbon concrete nano-CASH seed crystal reinforcement agent, which is used in ordinary silicate cement or low-carbon concrete, with a dosage of 0.5-2% of the cement mass.

[0024] Furthermore, in the above application, the nano-CASH seed reinforcer is added simultaneously with cement during concrete mixing, with a dry mixing time of ≥30 seconds and a water-cement ratio of 0.35-0.50.

[0025] Furthermore, in the above applications, after being mixed with cement paste, the compressive strength after 1 day is ≥18MPa, the strength improvement rate is ≥30%, and the test standard is GB / T 17671.

[0026] Furthermore, in the above application, the carbonation depth of the reinforcing agent in concrete is ≤5mm (28 days), according to the test standard GB / T 50082, and the chloride ion diffusion coefficient is reduced by ≥20%.

[0027] Compared with the prior art, the present invention has the following outstanding advantages:

[0028] 1. High efficiency and early strength: The nano-CASH seed crystals synthesized in this invention have a crystal structure similar to cement hydration products, which can serve as a preferred growth template, significantly accelerating the cement hydration process, thereby greatly improving the early compressive strength of concrete and helping to shorten the construction period.

[0029] 2. Good dispersion stability: Through the synergistic effect of silane coupling agent and sodium polyacrylate dispersant, the surface of nanocrystals is modified, which effectively prevents agglomeration and sedimentation during storage and use, and ensures the homogeneity of the product and the stability of the reinforcing effect.

[0030] 3. Good compatibility: The selected polycarboxylate superplasticizer is not only one of the synthetic components, but also ensures good compatibility between the seed crystals and the high-efficiency superplasticizers commonly used in modern concrete, effectively improving the initial workability of concrete and reducing slump loss over time.

[0031] 4. Significant low-carbon effect: This seed crystal has a highly efficient activating effect on the early activity of industrial solid wastes such as fly ash and slag, making it possible to significantly increase the amount of solid waste and reduce the amount of cement while ensuring the mechanical properties of concrete, which is in line with the development direction of green building materials.

[0032] 5. Controllable process and easy to promote: The preparation method has a clear process flow, mild reaction conditions, and easy-to-control parameters. It does not require special and expensive equipment, is suitable for large-scale industrial production, and has good market application prospects. Attached Figure Description

[0033] Figure 1 Comparison of static stability of nanocrystal seed suspensions (suspension rate, average value);

[0034] Figure 2 Development of compressive strength of cement paste (MPa, average value);

[0035] Figure 3 Strength development of paste with high fly ash content (MPa, average value). Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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.

[0037] Table 1 Raw Material List

[0038]

[0039]

[0040] Example 1

[0041] A low-carbon concrete nano-CASH seed crystal reinforcing agent, made from the following raw materials in parts by weight:

[0042] 150 parts water, 20 parts sodium silicate nonahydrate, 15 parts calcium nitrate tetrahydrate, 5 parts aluminum nitrate nonahydrate, 1 part polycarboxylate superplasticizer (PCE), 1 part sodium hydroxide, 0.5 parts γ-aminopropyltriethoxysilane, and 0.5 parts sodium polyacrylate dispersant;

[0043] The polycarboxylate superplasticizer is an ester PCE with a number average molecular weight of 5000 g / mol.

[0044] The preparation method of the above-mentioned nano-CASH seed crystal enhancer includes:

[0045] (a) Dissolution: Mix water, sodium hydroxide, sodium silicate nonahydrate and aluminum nitrate nonahydrate, and stir at 40°C for 20 minutes to obtain mixture A;

[0046] (b) Precipitation reaction: Add calcium nitrate tetrahydrate to mixture A and stir at 500 r / min for 60 minutes;

[0047] (c) Dispersion modification: Polycarboxylate superplasticizer, γ-aminopropyltriethoxysilane and sodium polyacrylate dispersant were added and dispersed at 1000 r / min for 2 hours.

[0048] (d) pH adjustment: The pH of the system was adjusted to 12.5 with a 10wt% sodium hydroxide solution to obtain nano-CASH seed crystal enhancer.

[0049] Example 2

[0050] A low-carbon concrete nano-CASH seed crystal reinforcing agent, made from the following raw materials in parts by weight:

[0051] 180 parts water, 22.72 parts sodium silicate nonahydrate, 18.88 parts calcium nitrate tetrahydrate, 6.5 parts aluminum nitrate nonahydrate, 2.5 parts polycarboxylate superplasticizer (PCE), 2.5 parts sodium hydroxide, 1.2 parts γ-glycidyl etheroxypropyltrimethoxysilane, and 1.2 parts sodium polyacrylate dispersant;

[0052] The polycarboxylate superplasticizer is an ester PCE with a number average molecular weight of 12000 g / mol.

[0053] The preparation method of the above-mentioned nano-CASH seed crystal enhancer includes:

[0054] (a) Dissolution: Mix water, sodium hydroxide, sodium silicate nonahydrate and aluminum nitrate nonahydrate, and stir at 50°C for 15 minutes to obtain mixture A;

[0055] (b) Precipitation reaction: Add calcium nitrate tetrahydrate to mixture A and stir at 650 r / min for 45 minutes;

[0056] (c) Dispersion modification: Polycarboxylate superplasticizer, γ-glycidyl etheroxypropyltrimethoxysilane and sodium polyacrylate dispersant were added and dispersed at high speed at 1250 r / min for 1.5 hours;

[0057] (d) pH adjustment: The pH of the system was adjusted to 13.0 with a 10wt% sodium hydroxide solution to obtain nano-CASH seed crystal enhancer.

[0058] Example 3

[0059] A low-carbon concrete nano-CASH seed crystal reinforcing agent, made from the following raw materials in parts by weight:

[0060] 200 parts water, 25 parts sodium silicate nonahydrate, 20 parts calcium nitrate tetrahydrate, 8 parts aluminum nitrate nonahydrate, 4 parts polycarboxylate superplasticizer (PCE), 4 parts sodium hydroxide, 2 parts γ-aminopropyltriethoxysilane, and 2 parts sodium polyacrylate dispersant.

[0061] The polycarboxylate superplasticizer is an ester PCE with a number average molecular weight of 20,000 g / mol.

[0062] The preparation method of the above-mentioned nano-CASH seed crystal enhancer includes:

[0063] (a) Dissolution: Mix water, sodium hydroxide, sodium silicate nonahydrate and aluminum nitrate nonahydrate, and stir at 60°C for 10 minutes to obtain mixture A;

[0064] (b) Precipitation reaction: Add calcium nitrate tetrahydrate to mixture A and stir at 800 r / min for 30 minutes;

[0065] (c) Dispersion modification: Polycarboxylate superplasticizer, γ-aminopropyltriethoxysilane and sodium polyacrylate dispersant were added and dispersed at high speed at 1500 r / min for 1 hour;

[0066] (d) pH adjustment: The pH of the system was adjusted to 13.5 with a 10wt% sodium hydroxide solution to obtain nano-CASH seed enhancer.

[0067] Comparative Example 1

[0068] An enhancing agent, made from the following raw materials in parts by weight:

[0069] 180 parts water, 22.72 parts sodium silicate nonahydrate, 18.88 parts calcium nitrate tetrahydrate, 2.5 parts polycarboxylate superplasticizer (PCE), 2.5 parts sodium hydroxide, 1.2 parts γ-glycidyl etheroxypropyltrimethoxysilane, and 1.2 parts sodium polyacrylate dispersant; (excluding aluminum nitrate nonahydrate).

[0070] The rest is the same as in Example 2.

[0071] Comparative Example 2

[0072] An enhancing agent, made from the following raw materials in parts by weight:

[0073] 180 parts water, 22.72 parts sodium silicate nonahydrate, 18.88 parts calcium nitrate tetrahydrate, 6.5 parts aluminum nitrate nonahydrate, 2.5 parts sodium hydroxide, 1.2 parts γ-glycidyl etheroxypropyltrimethoxysilane, and 1.2 parts sodium polyacrylate dispersant; (excluding polycarboxylate superplasticizer PCE).

[0074] The rest is the same as in Example 2.

[0075] Comparative Example 3

[0076] An enhancing agent, made from the following raw materials in parts by weight:

[0077] 180 parts water, 22.72 parts sodium silicate nonahydrate, 18.88 parts calcium nitrate tetrahydrate, 6.5 parts aluminum nitrate nonahydrate, 2.5 parts polycarboxylate superplasticizer (PCE), and 2.5 parts sodium hydroxide; (excluding γ-glycidoxypropyltrimethoxysilane and sodium polyacrylate dispersant).

[0078] The rest is the same as in Example 2.

[0079] Comparative Example 4

[0080] An enhancing agent, the preparation method of which is as follows:

[0081] Water, sodium hydroxide, sodium silicate nonahydrate, aluminum nitrate nonahydrate, and calcium nitrate tetrahydrate were mixed simultaneously and stirred at 50°C and 650 rpm for 45 minutes. Then, polycarboxylate superplasticizer (PCE), γ-glycidyl etheroxypropyltrimethoxysilane, and sodium polyacrylate dispersant were added and dispersed at 1250 rpm for 1.5 hours. (The order of feeding was changed, and all solid raw materials were added at once.)

[0082] The raw material composition is the same as in Example 2.

[0083] Comparative Example 5

[0084] An enhancing agent, made from the following raw materials in parts by weight:

[0085] The ingredients are: 180 parts water, 22.72 parts sodium silicate nonahydrate, 18.88 parts calcium nitrate tetrahydrate, 6.5 parts aluminum nitrate nonahydrate, 2.5 parts polycarboxylate superplasticizer (PCE), and 2.5 parts sodium hydroxide (excluding γ-glycidyl etheroxypropyltrimethoxysilane and sodium polyacrylate dispersant), and the high-speed dispersion time in step (c) of the preparation process is shortened to 0.5 hours.

[0086] The rest is the same as in Example 2.

[0087] Test Example 1

[0088] Nanocrystal seed dispersion stability test

[0089] Objective: To verify the synergistic effect of surface modifiers and dispersants on the stability of seed crystal suspensions.

[0090] method:

[0091] 200 mL of each of the fresh samples of the nanocrystal seed enhancers obtained in Example 2 and Comparative Examples 3-5 were placed in a 250 mL stoppered graduated cylinder.

[0092] The sample was left to stand at room temperature (25±2℃), and the height of the settlement layer was observed and recorded at time points of 0.5h, 1h, 2h, 4h, 8h, and 24h.

[0093] Stability is expressed as suspension rate: Suspension rate (%) = (200 - Settlement layer volume) / 200 × 100%.

[0094] The results are shown in Table 2 and Figure 1 .

[0095] Table 2 Comparison of static stability of nanocrystal seed suspensions (suspension rate, average value).

[0096] Group 0.5h 2h 8h 24h Example 2 100 99.5 98.2 95.7 Comparative Example 3 100 92.3 85.1 68.4 Comparative Example 4 100 88.7 76.5 55.9 Comparative Example 5 100 83.5 65.2 42.8

[0097] Conclusion: After 24 hours, the suspension rate of Example 2 (containing a complete dispersion system) remained above 95%, significantly better than the comparative examples lacking dispersion components or with improper processes (P<0.01). The synergistic effect of the silane coupling agent and sodium polyacrylate dispersant, along with sufficient high-speed dispersion time, effectively reduced the surface energy of nanoparticles and formed steric hindrance, which is key to maintaining the long-term stability of the system.

[0098] Test Example 2

[0099] Early compressive strength test of cement paste

[0100] Objective: To evaluate the effect of nanocrystalline seeds on enhancing the early strength of cement.

[0101] method:

[0102] Standard cement paste: 100wt% P·II 52.5 grade Portland cement, water-cement ratio 0.35.

[0103] Experimental group: Based on the standard neat cement paste, 1 wt% (percentage of cement mass) of the seed crystal reinforcing agent obtained in Examples 1-3 and Comparative Examples 1-2 were added respectively.

[0104] 40mm×40mm×160mm specimens were formed according to GB / T 17671-2021 Cement Mortar Strength Test Method (ISO Method) and cured for 1 day and 3 days under standard curing conditions (20±1℃, RH≥95%).

[0105] The compressive strength was determined using a pressure testing machine (model: YES-300, range: 300kN), and the average value of 3 specimens in each group was taken.

[0106] The results are shown in Table 3 and Figure 2 .

[0107] Table 3 Development of compressive strength of cement paste (MPa, average value).

[0108] Group 1d compressive strength Improved from the benchmark 3D compressive strength Improved from the benchmark Standard Clean Pulp 14.6 - 32.1 - Example 1 19.8 35.6％ 39.5 23.1％ Example 2 20.5 40.4％ 40.8 27.1％ Example 3 18.9 29.5％ 38.2 19.0％ Comparative Example 1 16.2 11.0％ 34.8 8.4％ Comparative Example 2 15.1 3.4％ 33.5 4.4％

[0109] Conclusion: The addition of the nanocrystalline seeds of this invention can significantly improve the early strength of cement paste, with Example 2 (optimized mix ratio) showing the best effect, increasing the 1-day strength by over 40%. Comparative Example 1 (without aluminum source) and Comparative Example 2 (without PCE) showed limited strengthening effects, demonstrating that the CASH structure and good compatibility with water-reducing agents are crucial for exerting the seed effect.

[0110] Test Example 3

[0111] Compatibility test with polycarboxylate superplasticizer and concrete workability test

[0112] Objective: To investigate the effect of seed crystals on the slump and slump loss of concrete over time.

[0113] method:

[0114] Concrete mix proportion: Cement (P·O 42.5) 300kg / m³ 3 Fly ash (Grade II) 100kg / m³ 3 780kg / m³ of sand 3 1020 kg / m³ of gravel 3 Water 160kg / m 3 (Water-to-binder ratio 0.40), polycarboxylate superplasticizer (solid content 20%) dosage 1.0%.

[0115] Experimental group: The seed crystal reinforcing agent obtained in Example 2 (dosage of 1% of the total mass of cementitious materials) was added to the concrete mixing water in advance.

[0116] Control group: No seed crystals added.

[0117] The initial slump and the slump retention value after standing for 60 minutes were tested according to the "GB / T 50080-2016 Standard for Test Methods of Performance of Ordinary Concrete Mixture".

[0118] The results are shown in Table 4.

[0119] Table 4 Comparison of Concrete Workability Retention Capacity

[0120]

[0121] Conclusion: The concrete with the seed crystals from Example 2 exhibited a significantly lower slump loss rate at 60 minutes compared to the control group (P<0.05). This indicates that the seed crystals of this invention have good compatibility with the polycarboxylate superplasticizer, effectively improving the workability retention of concrete and facilitating construction.

[0122] Test Example 4

[0123] Strength contribution test in low-carbon cementitious systems (high fly ash content)

[0124] Objective: To verify the effect of seed crystals on the early strength activation of industrial solid waste systems with high doping levels.

[0125] method:

[0126] Cementitious materials: Fly ash (FA) content is 50wt% (i.e., cement: fly ash = 1:1), total cementitious materials are 100%.

[0127] Experimental group: 1 wt% of the seed crystal enhancer from Example 2 was added. Water-to-binder ratio: 0.45.

[0128] The compressive strength of the cement paste specimens was tested at 3 days, 7 days, and 28 days, and compared with the blank group (high fly ash, no seed crystals) and the pure cement benchmark group.

[0129] The results are shown in Table 5 and Figure 3 .

[0130] Table 5 Development of paste strength with high fly ash content (MPa, average value).

[0131] Group 3D compressive strength 7d compressive strength 28-day compressive strength Pure cement benchmark group 24.8 38.6 52.3 High-fly ash blank group 5.2 12.7 35.4 High-efficiency fly ash + Example 2 10.5 22.9 46.8

[0132] Conclusion: In a low-carbon system with high fly ash (50%) content, the seed crystals of Example 2 significantly improved early strength, with a 3-day strength reaching 202% of the high fly ash blank group and a 7-day strength increase of 80%. This indicates that the seed crystals can effectively promote the early pozzolanic reaction of fly ash, providing an effective technical approach for reducing cement usage and achieving low-carbon concrete.

[0133] Test Case Summary:

[0134] The above series of tests verified the technical effects of the present invention: 1. Dispersion stability: After standing for 24 hours, the suspension rate of the product obtained in Example 2 reached 95.7%, significantly better than the comparative examples (42.8%-68.4%) lacking dispersion components or with improper processes. 2. Strengthening effect: Cement paste with 1% of the seed crystals from Example 2 achieved compressive strengths of 20.5 MPa at 1 day and 40.8 MPa at 3 days, respectively, representing increases of 40.4% and 27.1% compared to the baseline paste (14.6 MPa, 32.1 MPa); while the comparative examples without aluminum source or PCE showed limited improvement (1-day strength increase of only 3.4%-11.0%). 3. Workability retention: In concrete, the seed crystals from Example 2 significantly reduced the slump loss rate at 60 minutes from 25.0% in the control group to 9.3%. 4. Low-carbon application: In a cementitious system with 50% fly ash content, after adding 1% of the seed crystals from Example 2, the 3-day and 7-day compressive strengths reached 10.5 MPa and 22.9 MPa, respectively, representing increases of 102% and 80% compared to the untreated high-fly ash blank group (5.2 MPa, 12.7 MPa). The 28-day strength reached 46.8 MPa, approaching the pure cement benchmark level (52.3 MPa). Quantitative data fully demonstrate that the product of this invention exhibits excellent performance in terms of dispersibility, early strength, compatibility, and promotion of solid waste utilization.

[0135] The above are merely a few preferred embodiments of the present invention, described in a relatively specific and detailed manner, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention.

Claims

1. A low-carbon concrete nano-CASH seed crystal reinforcing agent, characterized in that, Raw materials, by weight, include:

2. The low-carbon concrete nano-CASH seed crystal reinforcing agent according to claim 1, characterized in that: The molar ratio of sodium silicate nonahydrate to aluminum nitrate nonahydrate, calculated as silicon and aluminum, is 4.5:1 to 5.5:

1.

3. The low-carbon concrete nano-CASH seed crystal reinforcing agent according to claim 1, characterized in that: The polycarboxylate superplasticizer is an ester-based polycarboxylate superplasticizer with a number-average molecular weight of 5000-20000 g / mol and a water reduction rate of ≥25%.

4. The low-carbon concrete nano-CASH seed crystal reinforcing agent according to claim 1, characterized in that: The silane coupling agent is γ-aminopropyltriethoxysilane or γ-glycidoxypropyltrimethoxysilane.

5. The method for preparing the low-carbon concrete nano-CASH seed crystal reinforcement as described in any one of claims 1-4, characterized in that, Includes the following steps: (1) Dissolution: Mix water, sodium hydroxide, sodium silicate nonahydrate and aluminum nitrate nonahydrate, and stir at 40-60℃ for 10-20 minutes to obtain mixture A; (2) Precipitation reaction: Add calcium nitrate tetrahydrate to mixture A and stir at 500-800 r / min for 30-60 minutes to generate CASH precipitate; (3) Dispersion modification: Add polycarboxylate superplasticizer, silane coupling agent and sodium polyacrylate dispersant, and disperse at high speed at 1000-1500 r / min for 1-2 hours; (4) pH adjustment: The pH of the system was adjusted to 12.5-13.5 with sodium hydroxide solution to obtain nano CASH seed enhancer.

6. The preparation method according to claim 5, characterized in that: The high-speed dispersion in step (3) uses a disc-type sawtooth dispersion disc with a diameter ratio of 1:3 to 1:5 to the container diameter, and the temperature is controlled to be ≤50℃.

7. The application of the low-carbon concrete nano-CASH seed crystal reinforcement as described in any one of claims 1-4, characterized in that: When used in ordinary silicate cement or low-carbon concrete, the dosage is 0.5-2% of the cement mass.

8. The application according to claim 7, characterized in that: The nano-CASH seed crystal reinforcing agent is added simultaneously with cement during concrete mixing, with a dry mixing time of ≥30 seconds and a water-cement ratio of 0.35-0.

50.

9. The application according to claim 7, characterized in that: After being mixed with cement paste, the compressive strength after 1 day is ≥18MPa, and the strength improvement rate is ≥30%.

10. The application according to claim 7, characterized in that: The reinforcing agent has a carbonation depth of ≤5mm in concrete and a chloride ion diffusion coefficient reduced by ≥20%.

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