Concrete admixture and preparation method thereof

Abstract

The invention discloses a concrete admixture and a preparation method thereof, and relates to the technical field of building materials, and the admixture is composed of a polycarboxylate superplasticizer, sulphoaluminate cement clinker, sodium silicate, N-methylethanolamine, modified nano-silica, a retarder and hyaluronic acid according to a specific proportion. The preparation method comprises the key steps of premixing, compounding, clinker adding, pH and temperature adjusting, low-temperature ultrasonic doping of hyaluronic acid, homogenizing, filtering, packaging and the like. According to the admixture disclosed by the invention, through the synergistic effect of all the components, the quick-setting and early-strength performance of concrete is remarkably improved, the injection rebound rate is effectively reduced, and the compressive strength, the anti-permeability grade and the freezing resistance are greatly improved. The admixture is especially suitable for recycled aggregate concrete, supports replacement of 20-50% of recycled aggregate through matched aggregate pretreatment and fly ash compounding, and has significantly improved strength. The coating has excellent temperature adaptability, construction performance and storage stability.

Description

Technical Field

[0001] The present invention relates to the technical field of building materials, and in particular to a concrete admixture and a preparation method thereof. Background Art

[0002] Shotcrete is widely used in underground engineering and reinforcement projects due to its high construction efficiency and adaptability to complex structural surfaces.

[0003] However, traditional shotcrete has the following defects: slow early strength development, which makes it difficult to meet rapid load-bearing requirements; high rebound rate, usually 15%-25%, resulting in material waste and environmental pollution; insufficient durability and easy to be eroded by the environment.

[0004] While existing admixtures can partially improve performance, they suffer from conflicts between rapid setting and strength development, as well as poor compatibility with cement. For example, while alkali-based accelerators can accelerate setting, they can lead to strength reduction, while alkali-free accelerators are expensive and have limited compatibility. Therefore, developing a shotcrete admixture that combines rapid setting, low rebound, and high durability is of great value. Summary of the Invention

[0005] In order to solve the technical problems existing in the prior art, the present application provides a concrete admixture, which achieves rapid coagulation, low rebound rate, and improvement of compressive strength and impermeability grade of concrete by optimizing component design and synergistic effect between each other. The present invention also provides a preparation method of the above-mentioned concrete admixture.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted in this application is: a concrete admixture composed of the following raw materials in parts by weight: 30-40 parts of polycarboxylate water reducer, 20-25 parts of sulfoaluminate cement clinker, 15-20 parts of sodium silicate, 8-12 parts of N-methylethanolamine, 5-8 parts of nano-silica, 2-4 parts of retarder, and 0.01-0.05 parts of hyaluronic acid.

[0007] The polycarboxylate water-reducing agent of the present invention is adsorbed on the surface of cement particles through the steric effect, forming electrostatic repulsion, dispersing cement agglomerates, releasing the encapsulated free water, and reducing water consumption. The above-mentioned polycarboxylate water-reducing agent is combined with the water-retaining effect of hyaluronic acid to suppress slump loss in a high-temperature environment. Hyaluronic acid adsorbs free water to form a three-dimensional network, reducing the rebound of shotcrete. Hydroxyl or carboxyl groups hydrogen bond with cement particles, reducing the friction between aggregate and slurry and improving workability. Compounded with polycarboxylate water-reducing agent, it suppresses high-temperature slump loss. At the same time, it synergizes with nano-silica to improve the interface of recycled aggregate and improve density. It achieves a four-in-one performance improvement of water retention, early strength, density, and durability, and is particularly suitable for high-demand scenarios such as shotcrete and recycled aggregate concrete, with significant technical and economic benefits.

[0008] The secondary amine groups in the aforementioned N-methylethanolamine selectively accelerate the nucleation and growth of ettringite in sulfoaluminate clinker, shortening the setting induction period and improving early strength. They also retard excessive silicate phase reactions and reduce thermal stress. Primary hydroxyl groups bond to silanol groups on the surface of nanosilica, which, combined with the steric hindrance of methyl groups, significantly enhances the dispersion stability of the nanoparticles, reducing porosity by 8-12%, increasing 28-day strength by 5-8%, and reducing chloride ion permeability by 35%. The short-chain methyl groups exhibit weak hydrophobicity, precisely controlling the air content to ≤3.5%, forming fine, uniform bubbles and improving freeze-thaw resistance by 30%. The weak alkalinity maintains the ionization equilibrium of polycarboxylic acid molecules, enhancing their adsorption to cement particles and reducing fluidity loss over time by up to 40%. This significantly improves concrete density, durability, and volume stability while maintaining early strength, making it suitable for harsh environments such as those requiring high frost resistance and marine engineering.

[0009] Optionally, the hyaluronic acid is produced by microbial fermentation, has a purity of ≥95%, and is pre-dissolved in deionized water to form a 1% gel. This pre-dissolved hyaluronic acid in deionized water forms a 1% gel that fully stretches the molecular chains, further enhancing water retention and thickening properties. In shotcrete, this property significantly reduces rebound.

[0010] Optionally, the nano-silica is modified with a KH-550 silane coupling agent, and the amount of the silane coupling agent is 1.5-2%.

[0011] The siloxane groups of KH-550 are hydrolyzed and bonded to the surface of nano-SiO2. The amino groups of KH-550 adsorb cement particles in a directional manner to form a "mineral-nanobridge", which reduces the porosity of the cement paste by 12~15%. [SiO4] generated by sodium silicate in an alkaline environment 4 ⁻ Cross-linked with KH-550 siloxane network to form fast ion channels, promote OH⁻ diffusion, and increase the hydration degree of sulphoaluminate-silicate composite system by 30%; the hydrophobic alkyl chain (-C3H6-) of modified nano-SiO2 is entangled with the side chain of polycarboxylate water reducer, enhancing the steric hindrance effect, and the fluidity loss rate of the slurry within 2 hours is ≤5%.

[0012] The present invention also provides a method for preparing a concrete admixture, comprising the following steps: S101: Premixing: Disperse the polycarboxylate water reducer and nano-silica at high speed at 60-65°C for 25-30 minutes to form a uniform slurry; S102: Compounding: Sodium silicate and N-methylethanolamine are sequentially added to the homogeneous slurry, and the mixture is heated to 80-85° C. and stirred for 45-60 minutes; S103: Add sulphoaluminate cement clinker and continue stirring for 15 minutes; S104: Adjustment: Cool the mixture to 40-45°C, adjust the pH to 9-10 with 30% sodium hydroxide solution, add a retarder and 0.1-0.2% isothiazolinone fungicide; S105: Incorporation of hyaluronic acid: 1% hyaluronic acid gel was slowly injected into the mixture and simultaneously sonicated; S106: Add retarder and 0.1-0.2% fungicide and homogenize for 10 minutes; S107: Pass through 300 mesh sieve and package in light-proof stainless steel container.

[0013] A 1% hyaluronic acid solution is slowly injected and simultaneously ultrasonically treated. The hyaluronic acid molecular chains fully extend, forming a three-dimensional water-retaining network that absorbs free water and encapsulates the nano-silica particles, reducing agglomeration. Simultaneously, the hydroxyl and carboxyl groups of the hyaluronic acid form hydrogen bonds with the cement particles, reducing friction between the aggregate and the paste and improving workability. A retarder is then added to balance the hydration rate and meet construction requirements. The mixture is then passed through a 300-mesh sieve to remove undispersed particles and ensure uniform admixture consistency. Finally, the mixture is packaged in a light-proof container to prevent the hyaluronic acid from decomposing in the light.

[0014] Optionally, the hyaluronic acid gel solution needs to be added in an environment below 25°C to avoid high temperature degradation.

[0015] In step S105, after the mixture is cooled to below 25°C, a 1% hyaluronic acid gel is injected and simultaneously ultrasonicated to promote dispersion. This low-temperature environment effectively prevents molecular chain breakage and degradation of the hyaluronic acid at high temperatures, ensuring the complete formation of its three-dimensional water-retention network. The carboxyl and hydroxyl groups of hyaluronic acid remain highly active at low temperatures, fully adsorbing free water and encapsulating the nano-silica particles, forming a stable "hyaluronic acid-nano-SiO2" composite structure and reducing agglomeration. The shotcrete has a rebound rate of ≤7.2%, fluidity meets self-leveling requirements, 1-day strength ≥28 MPa, and 28-day strength ≥58.3 MPa. It has an impermeability rating of ≥P14, a damage rate of ≤2% after 300 freeze-thaw cycles, and significantly improved resistance to chloride ion penetration. It supports 20-50% replacement of recycled aggregate, increasing strength by 37%, meeting the requirements of green building materials.

[0016] Optionally, in step S102 , 0.5-1.2 parts of triethanolamine are selectively added, and the addition is only performed when the ambient temperature is ≥10° C.

[0017] The aforementioned early-strength effect of triethanolamine is closely related to temperature. At ambient temperatures ≥10°C, its molecular activity increases significantly, exerting its effects through the following mechanism: triethanolamine's amino groups form stable complexes with ions such as calcium and ferric iron in cement, accelerating the hydration reactions of aluminates and silicates. Combining with ettringite, generated by the hydration of sulfoaluminate cement clinker, it rapidly forms a skeleton structure, shortens the induction period, controls the initial setting time to within 5 minutes, and increases the 1-day compressive strength by 15-20%. When the ambient temperature is <10°C, triethanolamine's molecular motion slows, its complexation efficiency decreases, and excessive early strength may lead to reduced concrete workability, such as decreased fluidity and increased rebound. Therefore, it should only be added at temperatures ≥10°C to balance early strength with workability.

[0018] Optionally, the retarder in step S106 is a molasses-based substance, and its dosage is adjusted according to the ambient temperature: When the temperature is greater than 30°C, the amount of molasses is reduced to 2-2.5 parts; When the temperature is less than 10℃, the amount of molasses is increased to 3.5-4 parts.

[0019] The polysaccharides in the above molasses are adsorbed on the surface of cement particles through hydroxyl groups, forming a physical barrier, inhibiting the dissolution of calcium ions and the hydration reaction of C3A and C3S, thereby delaying the setting time.

[0020] At temperatures above 30°C, hydration reactions accelerate and molasses molecules become more active, but excessive retarding can result in a prolonged initial setting time. Therefore, the dosage is reduced to 2-2.5 parts per molasses to balance rapid hardening with construction requirements. At 30-35°C, a molasses dosage of 2-2.5 parts per molasses ensures an initial setting time of ≤10 minutes, a 1-day strength of ≥32 MPa, and a rebound rate of ≤7.2%, meeting the requirements of rapid construction.

[0021] At temperatures below 10°C, the hydration reaction slows and the molasses adsorption efficiency decreases, requiring the addition to be increased to 3.5-4 parts per liter to maintain sufficient retarding effect and prevent premature hardening of the concrete. At 5-10°C, a molasses addition of 3.5-4 parts per liter extends the working time to 90 minutes, preventing freezing and uneven hardening of the concrete. The 28-day strength of recycled aggregate concrete increased by 37%.

[0022] Optionally, the finished product is stored in an ambient humidity controlled at ≤60%, and the storage period is ≤6 months.

[0023] A storage humidity of 60% or less effectively inhibits hyaluronic acid's hygroscopic degradation. The carboxyl and hydroxyl groups in the hyaluronic acid molecular chain readily form hydrogen bonds with water molecules. High humidity can lead to chain breakage, decreased viscosity, and consequent loss of water-retention capacity. By controlling humidity, the integrity of hyaluronic acid's three-dimensional network structure is preserved. Storing hyaluronic acid in a dark, stainless steel container prevents light-induced decomposition of hyaluronic acid into small molecular fragments, thus ensuring the integrity of the water-retention network.

[0024] During storage, the fungicide continuously inhibits microbial growth. Microorganisms may secrete enzymes that break down the glycosidic bonds of hyaluronic acid, reducing its molecular weight and rendering it ineffective. By controlling humidity and adding 0.1-0.2% fungicide, the biological stability of hyaluronic acid is doubled, extending its shelf life to 6 months.

[0025] Optionally, the above admixture is suitable for recycled aggregate concrete, and the recycled aggregate needs to be pretreated as follows: S201: Cleaning to remove surface impurities; S202: spraying a 5% by mass nano-silicon dioxide aqueous dispersion on the aggregate surface; S203: Dry the aggregate to a moisture content of ≤5%.

[0026] Nano-SiO2 sprayed during pretreatment and in the admixtures work together to fill the pores in the aggregate and paste, creating a dense "aggregate-paste" structure that improves early strength and density. The pozzolanic reaction of nano-SiO2 synergizes with the rapid hardening properties of sulfoaluminate cement clinker, rapidly forming a skeletal structure in both high and low temperatures. Hyaluronic acid forms a three-dimensional gel network in low humidity, adsorbing free water and encapsulating nanoparticles, reducing concrete drying shrinkage and cracking. The low water absorption of the pretreated aggregate combined with the water-retention properties of hyaluronic acid maintains concrete fluidity, keeping rebound at ≤7.2%. The retarder dosage is adjusted according to ambient temperature to precisely control the hydration rate and prevent premature hardening of the pretreated aggregate due to low moisture content. N-methylethanolamine accelerates the hydration of C3S and C3A by complexing calcium ions, synergizing with the sulfoaluminate cement clinker to achieve the dual benefits of "early strength and density."

[0027] Optionally, the replacement rate of the above-mentioned recycled aggregate in concrete is 20-50%, and 10-15% fly ash is compounded.

[0028] First, remove surface impurities, reduce fine particle content, and improve aggregate cleanliness. Then, spray a 5% nano-SiO2 aqueous dispersion: The nanoparticles penetrate the microcracks and pores of the aggregate, forming a dense filling layer and strengthening the interface transition zone. Simultaneously, the pozzolanic activity of the nano-SiO2 is activated, reacting with the subsequent cement hydration product, Ca(OH)2, to form CSH gel, further enhancing the aggregate-paste bond strength. Avoid introducing excessive free water to ensure that the retarder and N-methylethanolamine in the admixture effectively regulate the hydration rate.

[0029] Fly ash particles fill concrete pores, forming a "nano-micron" dual-stage filling system with nano-SiO2, improving density. SiO2 and Al2O3 in fly ash react with Ca(OH)2 in an alkaline environment to form CSH gel, which compensates for the strength loss of recycled aggregate. The inert components of fly ash absorb polycarboxylate superplasticizers, requiring N-methylethanolamine in the admixture to accelerate the hydration of C3S and C3A, balancing rapid hardening and density requirements.

[0030] Beneficial effects: 1. The comprehensive performance of concrete is significantly improved through the optimized ratio and synergistic effect of components such as polycarboxylate water reducer, sulphoaluminate cement clinker, sodium silicate, N-methylethanolamine, modified nano-silica, retarder and hyaluronic acid.

[0031] 2. N-methylethanolamine works synergistically with sulfoaluminate cement clinker to promote the rapid hydration of aluminate and silicate phases, forming an ettringite skeleton, achieving an initial setting time of ≤5min and a 1d compressive strength of ≥28MPa.

[0032] 3. The three-dimensional water-retention network formed by hyaluronic acid effectively absorbs free water. Combined with the dispersing effect of the polycarboxylate superplasticizer and the lubricating effect of N-methylethanolamine, it significantly reduces the rebound rate of shotcrete to ≤ 7.2%. The high density combined with the water-retention effect of hyaluronic acid imparts excellent impermeability and resistance to chloride ion penetration to the concrete. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments.

[0034] Example 1 This embodiment provides a concrete admixture, which is composed of the following raw materials in parts by weight: 35 kg of polycarboxylate water reducer, 22 kg of sulfoaluminate cement clinker, 18 kg of sodium silicate, 10 kg of N-methylethanolamine, 6 kg of nano-silica, 3 kg of retarder, and 0.03 kg of hyaluronic acid.

[0035] The preparation process is: S101: Polycarboxylate water reducer and nano-silica were dispersed at high speed at 62°C for 28 minutes to form a uniform slurry.

[0036] S102: Sodium silicate and N-methylethanolamine were added, and the temperature was raised to 82°C and stirred for 50 minutes; the ambient temperature was 25°C, and triethanolamine was not added.

[0037] S103: Add sulphoaluminate cement clinker and stir for 15 minutes.

[0038] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg fungicide.

[0039] S105: Inject 1% hyaluronic acid glue at 20°C and perform ultrasonic treatment simultaneously.

[0040] S106: Add retarder and fungicide and homogenize for 10 minutes.

[0041] S107: Pass through 300 mesh sieve, package in light-proof stainless steel container, store at 50% humidity, shelf life 6 months.

[0042] Example 2 A concrete admixture is composed of the following raw materials in parts by weight: 38 kg of polycarboxylate water reducer, 20 kg of sulphoaluminate cement clinker, 16 kg of sodium silicate, 12 kg of N-methylethanolamine, 7 kg of nano-silica, 2.5 kg of retarder, and 0.04 kg of hyaluronic acid.

[0043] The preparation process is: S101: Polycarboxylate water reducer and nano-silica were dispersed at high speed at 65°C for 30 minutes to form a uniform slurry.

[0044] S102: Add sodium silicate and N-methylethanolamine, raise the temperature to 85°C and stir for 60 minutes; when the ambient temperature is 35°C, add 1.2 kg of triethanolamine.

[0045] S103: Add sulphoaluminate cement clinker and stir for 15 minutes.

[0046] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg fungicide.

[0047] S105: Inject 1% hyaluronic acid glue at 25°C and perform ultrasonic treatment simultaneously.

[0048] S106: Add retarder and fungicide and homogenize for 10 minutes.

[0049] S107: Pass through 300 mesh sieve, package in light-proof stainless steel container, store at 50% humidity, shelf life 6 months.

[0050] Example 3 A concrete admixture is composed of the following raw materials in parts by weight: 32 kg of polycarboxylate water reducer, 24 kg of sulphoaluminate cement clinker, 19 kg of sodium silicate, 9 kg of N-methylethanolamine, 5 kg of nano-silica, 4 kg of retarder, and 0.02 kg of hyaluronic acid.

[0051] The preparation process is: S101: Polycarboxylate water reducer and nano-silica were dispersed at high speed at 65°C for 25 minutes to form a uniform slurry.

[0052] S102: Sodium silicate and N-methylethanolamine were added, and the temperature was raised to 80°C and stirred for 45 minutes; the ambient temperature was 8°C, and no triethanolamine was added.

[0053] S103: Add sulphoaluminate cement clinker and stir for 15 minutes.

[0054] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg fungicide.

[0055] S105: Inject 1% hyaluronic acid glue at 18°C ​​and perform ultrasonic treatment simultaneously.

[0056] S106: Add retarder and fungicide and homogenize for 10 minutes.

[0057] S107: Pass through 300 mesh sieve, package in light-proof stainless steel container, store at 50% humidity, shelf life 6 months.

[0058] Example 4 A concrete admixture is composed of the following raw materials in parts by weight: 30 kg of polycarboxylate water reducer, 25 kg of sulphoaluminate cement clinker, 20 kg of sodium silicate, 8 kg of N-methylethanolamine, 8 kg of nano-silica, 3.5 kg of retarder, and 0.05 kg of hyaluronic acid.

[0059] The preparation process is: S101: Polycarboxylate water reducer and nano-silica were dispersed at high speed at 63°C for 27 minutes to form a uniform slurry.

[0060] S102: Add sodium silicate and N-methylethanolamine, raise the temperature to 83°C and stir for 55 minutes; when the ambient temperature is 20°C, add 0.8 kg of triethanolamine.

[0061] S103: Add sulphoaluminate cement clinker and stir for 15 minutes.

[0062] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, and add 3.5 kg of molasses retarder and 0.15 kg of fungicide when cooled to 20°C.

[0063] S105: Inject 1% hyaluronic acid glue at 25°C and perform ultrasonic treatment simultaneously.

[0064] S106: Add retarder and fungicide and homogenize for 10 minutes.

[0065] S107: Pass through 300 mesh sieve, package in light-proof stainless steel container, store at 50% humidity, shelf life 6 months.

[0066] Example 5 A concrete admixture is composed of the following raw materials in parts by weight: 40 kg of polycarboxylate water reducer, 21 kg of sulphoaluminate cement clinker, 15 kg of sodium silicate, 11 kg of N-methylethanolamine, 5 kg of nano-silica, 2.8 kg of retarder, and 0.01 kg of hyaluronic acid.

[0067] The preparation process is: S101: Polycarboxylate water reducer and nano-silica were dispersed at high speed at 64°C for 29 minutes to form a uniform slurry.

[0068] S102: Sodium silicate and N-methylethanolamine were added, and the temperature was raised to 84°C and stirred for 58 minutes; at an ambient temperature of 30°C, 0.5 kg of triethanolamine was added.

[0069] S103: Add sulphoaluminate cement clinker and stir for 15 minutes.

[0070] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg fungicide.

[0071] S105: Inject 1% hyaluronic acid glue at 24°C and perform ultrasonic treatment simultaneously.

[0072] S106: Add retarder and fungicide and homogenize for 10 minutes.

[0073] S107: Pass through 300 mesh sieve, package in light-proof stainless steel container, store at 50% humidity, shelf life 6 months.

[0074] Comparative Example 1 The other technical features of this comparative example are the same as those of Example 1. Nano-silica is not modified with KH-550, and unmodified nano-SiO2 is directly used in an amount of 6 kg; nano-SiO2 aqueous dispersion is not sprayed during the pretreatment of recycled aggregate.

[0075] Performance comparison: Conclusion: Unmodified nano-SiO2 has poor dispersion and cannot effectively fill pores and strengthen interfaces, resulting in a significant decrease in strength.

[0076] Comparative Example 2 The addition of hyaluronic acid gel in step S105 of Example 2 was omitted, and the other steps remained unchanged.

[0077] Performance comparison: Conclusion: The loss of hyaluronic acid water retention network leads to increased drying shrinkage of concrete, significantly increased rebound rate and decreased anti-permeability.

[0078] Comparative Example 3 Other technical features remain unchanged from Example 2, and the molasses dosage is fixed at 3 kg.

[0079] Performance comparison: Conclusion: Excessive molasses at high temperature leads to rapid hydration, short initial setting time, hindered strength development, and aggravated freeze-thaw damage.

[0080] Comparative Example 4 The recycled aggregate pretreatment steps S201-S203 are omitted, and the recycled aggregate that has not been cleaned and not sprayed with nano-SiO2 is directly used; the other steps remain unchanged.

[0081] Performance comparison: Conclusion: Unpretreated recycled aggregate has more impurities and higher porosity, which leads to increased strength loss and significantly reduced durability.

[0082] Comparative Example 5 The fly ash compounding step is omitted, and the recycled aggregate replacement rate remains at 50%; other steps remain unchanged.

[0083] Performance comparison: Conclusion: The lack of fly ash leads to insufficient strength development in the later stage, increased carbonization depth and decreased durability.

[0084] In order to quantify the technical effects of the present invention, the following test examples were designed to focus on verifying the optimization effects of strength, durability, and workability: Test Example 1 Objective: To verify the "nano-micron" dual-level filling effect of modified nano-SiO2 and fly ash.

[0085] method: Prepare two batches of concrete: Group A: Example 1 of the present invention; modified nano-SiO2 6%, fly ash 12%; Group B: Comparative Example 1; unmodified nano-SiO2 5%, no fly ash.

[0086] Test 28d compressive strength, impermeability grade and porosity.

[0087] result: Conclusion: Modified nano-SiO2 and fly ash synergistically reduce porosity and improve strength and impermeability.

[0088] Test Example 2 Objective: To verify the effect of hyaluronic acid on the workability and durability of concrete.

[0089] method: Prepare two batches of concrete: Group C: oil recovery admixture of Example 2 of the present invention (hyaluronic acid 0.04%); Group D: Comparative Example 2 (without hyaluronic acid).

[0090] Test indicators: test rebound rate, drying shrinkage rate, and mass loss after 300 freeze-thaw cycles.

[0091] result: Conclusion: The three-dimensional water-retention network formed by hyaluronic acid effectively reduces water evaporation and drying shrinkage, improves the frost resistance of concrete, and significantly reduces the rebound rate of spraying.

[0092] Test Example 3 Objective: To verify the dynamic control effect of triethanolamine and molasses retarder.

[0093] Method: Concrete was prepared under high temperature (35°C) and low temperature (8°C) conditions respectively: Group E: Example 2 of the present invention (1.2% triethanolamine and 2.2% molasses were added at high temperature); Group F: Comparative Example 3 (3% molasses fixed at high temperature, without triethanolamine).

[0094] Test initial setting time, 1d strength, and freeze-thaw mass loss.

[0095] result: Conclusion: Under high temperature, the technology of dynamically adding triethanolamine to accelerate early hydration and appropriately reducing the molasses dosage effectively balances the demand for rapid hardening with the requirements for density or durability, and avoids the problems of excessive coagulation and decreased strength or durability caused by a fixed high dosage of molasses.

[0096] Test Example 4 Purpose: To verify the comprehensive effect of recycled aggregate cleaning, nano-SiO2 spraying and drying.

[0097] Methods: Two groups of concrete with a recycled aggregate replacement rate of 50% were prepared: Group G: The admixture of Example 4 of the present invention was used, and the recycled aggregate was pretreated (cleaned, sprayed with 5% nano-SiO2 dispersion, and dried); Group H: Comparative Example 4 (recycled aggregate not pretreated) was adopted.

[0098] Test indicators: strength loss caused by recycled aggregate, flexural strength improvement, and chloride ion penetration depth.

[0099] result: Conclusion: The pretreatment process of recycled aggregate significantly strengthened the aggregate-paste interface transition zone, reduced the strength loss caused by recycled aggregate, and improved the flexural strength and resistance to chloride ion penetration.

[0100] Test Example 5 Purpose: To verify the contribution of fly ash to later strength and durability.

[0101] Methods: Two groups of concrete with a recycled aggregate replacement rate of 50% were prepared: Group I: The admixture of Example 4 of the present invention was used and mixed with 15% fly ash; Group J: Comparative Example 5 was used.

[0102] Test indicators: Test 90d strength and carbonization depth.

[0103] result: Conclusion: Fly ash compounding significantly improves the later strength and density of concrete through its pozzolanic activity and micro-aggregate filling effect, and effectively inhibits the development of carbonization depth.

[0104] Through comparative analysis of the comparative examples and test examples, the present invention has significant advantages in the following aspects: nanomaterial modification: modified nano-SiO2 and fly ash synergistically improve strength and density; water retention network construction: hyaluronic acid effectively reduces drying shrinkage, improves antifreeze and anti-seepage properties; temperature adaptability regulation: dynamically adjusts the hydration rate to adapt to wide temperature range construction; recycled aggregate pretreatment: cleaning, spraying nano-SiO2, and drying process reduce strength loss; fly ash compounding: improves later strength, inhibits carbonization, and optimizes durability.

[0105] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A concrete admixture, characterized in that The invention is composed of the following raw materials in parts by weight: 30-40 parts of polycarboxylate water reducer, 20-25 parts of sulphoaluminate cement clinker, 15-20 parts of sodium silicate, 8-12 parts of N-methylethanolamine, 5-8 parts of nano silicon dioxide, 2-4 parts of retarder and 0.01-0.05 parts of hyaluronic acid.

2. The concrete admixture according to claim 1, characterized in that The hyaluronic acid is prepared by microbial fermentation, has a purity of ≥95%, and is pre-dissolved in deionized water to form a 1% gel solution.

3. A concrete admixture according to claim 1, characterized in that, The nano-silica is modified by KH-550 silane coupling agent, and the amount of the silane coupling agent is 1.5-2%.

4. The method for preparing the concrete admixture according to any one of claims 1 to 3, wherein: The following steps are involved: S101: Premixing: Disperse the polycarboxylate water reducer and nano-silica at high speed at 60-65°C for 25-30 minutes to form a uniform slurry; S102: Compounding: Sodium silicate and N-methylethanolamine are sequentially added to the homogeneous slurry, and the mixture is heated to 80-85° C. and stirred for 45-60 minutes; S103: Add sulphoaluminate cement clinker and continue stirring for 15 minutes; S104: Adjustment: Cool the mixture to 40-45°C, adjust the pH to 9-10 with 30% sodium hydroxide solution, add a retarder and 0.1-0.2% isothiazolinone fungicide; S105: Slowly inject 1% hyaluronic acid gel into the mixture and perform ultrasonic treatment simultaneously; S106: Add retarder and 0.1-0.2% fungicide and homogenize for 10 minutes; S107: Pass through 300 mesh sieve and package in light-proof stainless steel container.

5. The method for preparing a concrete admixture according to claim 4, wherein: The hyaluronic acid glue needs to be added in an environment below 25°C to avoid high temperature degradation.

6. The method for preparing a concrete admixture according to claim 4, wherein: In step S102, 0.5-1.2 parts of triethanolamine are optionally added, and the addition is only performed when the ambient temperature is ≥10°C.

7. The method for preparing a concrete admixture according to claim 4, wherein: The retarder in step S106 is a molasses-based substance, and its dosage is adjusted according to the ambient temperature: When the temperature is greater than 30°C, the amount of molasses is reduced to 2-2.5 parts; When the temperature is less than 10℃, the amount of molasses is increased to 3.5-4 parts.

8. The method for preparing a concrete admixture according to claim 4, wherein: The finished product is stored in an environment where the humidity is controlled to be ≤60%, and the storage period is ≤6 months.

9. The method for preparing a concrete admixture according to claim 4, wherein: Applicable to recycled aggregate concrete, and the recycled aggregate needs to be pre-treated as follows: S201: Cleaning to remove surface impurities; S202: spraying 5% by mass of nano-silicon dioxide aqueous dispersion on the aggregate surface; S203: Dry the aggregate to a moisture content of ≤5%.

10. The method for preparing a concrete admixture according to claim 9, wherein: The replacement rate of the recycled aggregate in concrete is 20-50%, and 10-15% fly ash is compounded.

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