A concrete admixture and a method for preparing the same

Abstract

The application discloses a kind of concrete admixtures and preparation method thereof, it is related to building material technical field, and admixture is by polycarboxylate water reducing agent, sulphoaluminate cement clinker, sodium silicate, N-methyl ethanolamine, modified nanometer silicon dioxide, retarder and hyaluronic acid according to specific proportion Composition.Its preparation method includes the key steps such as pre-mixing, compounding, adding clinker, adjusting pH and temperature, low-temperature ultrasonic incorporation hyaluronic acid, homogenization, filtration packaging etc.The admixture of the application is synergized by each component, significantly improves the early strength performance of concrete, effectively reduces the rebound rate of jetting, and greatly improves the compressive strength, impermeability grade and frost resistance.The admixture is particularly suitable for recycled aggregate concrete, through the supporting aggregate pretreatment and fly ash compounding, 20-50% recycled aggregate replacement is supported and the strength is significantly improved.The application has excellent temperature adaptability, construction performance and storage stability.

Description

TECHNICAL FIELD

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

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

[0003] However, the traditional shotcrete has the following defects: slow early strength development, difficult to meet the rapid bearing demand; high rebound rate, usually 15%-25%, causing material waste and environmental pollution; insufficient durability, easily eroded by the environment.

[0004] Although the existing admixtures can partially improve the performance, they still have problems such as the contradiction between rapid setting and strength development, poor adaptability to cement, etc. For example, the alkali rapid setting agent can cause strength reduction, and the non-alkali rapid setting agent has high cost and limited adaptability. Therefore, it is of great value to develop a shotcrete admixture with rapid setting, low rebound, and high durability. SUMMARY

[0005] In order to solve the technical problems existing in the prior art, the present application provides a concrete admixture, which realizes rapid setting, low rebound rate, and improvement of compressive strength and impermeability grade of concrete through optimization of component design and synergistic effect between components. The present application also provides a preparation method of the above-mentioned concrete admixture.

[0006] In order to achieve the above-mentioned purposes, the technical scheme adopted by the present application is as follows: a concrete admixture, which is composed of the following raw materials by weight: polycarboxylate superplasticizer 30-40 parts, sulphoaluminate cement clinker 20-25 parts, sodium silicate 15-20 parts, N-methyl ethanolamine 8-12 parts, nano-silicon dioxide 5-8 parts, retarder 2-4 parts, and hyaluronic acid 0.01-0.05 parts.

[0007] The polycarboxylate superplasticizer of the present application is adsorbed on the surface of cement particles through steric hindrance effect, forms electrostatic repulsion, disperses cement agglomerates, releases free water, and reduces water consumption. The water retention effect of the polycarboxylate superplasticizer and hyaluronic acid is combined to inhibit the loss of slump in high temperature environment. Hyaluronic acid adsorbs free water to form a three-dimensional network, reduces the rebound of shotcrete. The hydroxyl or carboxyl group is combined with the hydrogen bond of cement particles to reduce the friction between aggregate and paste and improve the workability. The combination with polycarboxylate superplasticizer inhibits the loss of slump in high temperature. At the same time, it cooperates with nano-silicon dioxide to improve the interface of recycled aggregate and improve the compactness. It realizes the four-in-one performance improvement of water retention, early strength, compactness, and durability, and is especially suitable for high requirement scenes such as shotcrete and recycled aggregate concrete, with significant technical and economic benefits.

[0008] The secondary amine group in the N-methylethanolamine selectively accelerates the nucleation and growth of ettringite in the sulphate clinker, shortens the setting induction period, improves the early strength, delays the excessive reaction of the silicate phase, and reduces the temperature stress; the primary hydroxyl group bonds with the silanol group on the surface of the nano-silicon dioxide, and the steric hindrance effect of the methyl group significantly improves the dispersion stability of the nano-particles, reduces the porosity by 8-12%, increases the 28d strength by 5-8%, and reduces the chloride ion permeability by 35%; the short-chain methyl group has weak hydrophobicity, accurately controls the air content at ≤3.5%, forms fine and uniform bubbles, and improves the freeze-thaw resistance by 30%. The weak alkalinity maintains the ionization balance of the polycarboxylic acid molecules, enhances the adsorption of the polycarboxylic acid molecules on the cement particles, and reduces the time loss of fluidity by 40%. The concrete compactness, durability and volume stability are significantly improved under the premise of ensuring the early strength, and the concrete is suitable for harsh environments such as high frost resistance and marine engineering.

[0009] Optionally, the hyaluronic acid is prepared by a microbial fermentation method, has a purity of ≥95%, and is dissolved in deionized water in advance to form a 1% glue solution. The 1% glue solution formed by dissolving the hyaluronic acid in deionized water in advance has a fully stretched molecular chain, and further enhances the water retention and thickening properties. In the sprayed concrete, the feature can significantly reduce the rebound rate.

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

[0011] After the siloxane group of the KH-550 is hydrolyzed and bonded with the surface of the nano-SiO2, the amino group of the KH-550 is directionally adsorbed on the cement particles to form a "mineral-nano bridge", so that the porosity of the cement slurry is reduced by 12-15%; the [SiO4] 4 ⁻ generated by sodium silicate in an alkaline environment is crosslinked with the siloxane network of the KH-550 to form a rapid ion channel, promotes the diffusion of OH⁻, and increases the hydration degree of the sulphate-silicate composite system by 30%; the hydrophobic alkyl chain (-C3H6-) of the modified nano-SiO2 is entangled with the side chain of the polycarboxylic acid water reducing agent to enhance the steric hindrance effect, and the 2h fluidity loss rate of the slurry is ≤5%.

[0012] The application further provides a preparation method of the concrete admixture, which comprises the following steps:

[0013] S101: premixing: dispersing the polycarboxylic acid water reducing agent and the nano-silicon dioxide at a high speed for 25-30 min at 60-65 DEG C to form a uniform slurry;

[0014] S102: compounding: sequentially adding sodium silicate and N-methylethanolamine into the uniform slurry, and stirring at 80-85 DEG C for 45-60 min;

[0015] S103: adding sulphate cement clinker, and continuing to stir for 15 min;

[0016] S104: Adjusting: cool the mixture to 40-45℃, adjust the pH to 9-10 with 30% sodium hydroxide solution, add a retarder and 0.1-0.2% isothiazolinone bactericide;

[0017] S105: Incorporating hyaluronic acid: slowly inject 1% hyaluronic acid gel into the mixture, and simultaneously ultrasonic treatment;

[0018] S106: Add a retarder and 0.1-0.2% bactericide, and homogenize for 10 min;

[0019] S107: Pass through a 300-mesh sieve and package in a light-proof stainless steel container.

[0020] Slowly inject 1% hyaluronic acid gel and simultaneously ultrasonic treatment; the hyaluronic acid molecular chain is fully stretched to form a three-dimensional water-retaining network, adsorbing free water and wrapping nano-silicon dioxide particles to reduce agglomeration; at the same time, the hydroxyl / carboxyl groups of hyaluronic acid form hydrogen bonds with cement particles, reducing the friction between aggregates and paste and improving workability. Again, adding a retarder to balance the hydration rate to meet construction needs; passing through a 300-mesh sieve to remove undispersed particles to ensure uniformity of the admixture, and finally packaging in a light-proof container to prevent hyaluronic acid from decomposing when exposed to light.

[0021] Optionally, the above-mentioned hyaluronic acid gel needs to be added in an environment below 25°C to avoid high-temperature degradation.

[0022] In the S105 step, after the mixture is cooled to below 25°C, 1% hyaluronic acid gel is injected, and simultaneous ultrasonic treatment is used to promote dispersion. This low-temperature environment effectively avoids the molecular chain rupture and degradation of hyaluronic acid at high temperatures, ensuring the complete formation of its three-dimensional water-retaining network. The carboxyl and hydroxyl groups of hyaluronic acid remain highly active at low temperatures, allowing them to fully adsorb free water and wrap nano-silicon dioxide particles, forming a stable "hyaluronic acid-nano SiO2" composite structure and reducing agglomeration. The rebound rate of sprayed concrete is ≤7.2%, the fluidity meets the self-leveling requirements, the 1d strength is ≥28MPa, and the 28d strength is ≥58.3MPa. The impermeability rating is ≥P14, the damage rate after 300 freeze-thaw cycles is ≤2%, and the resistance to chloride ion penetration is significantly improved. Supports 20-50% replacement of recycled aggregates, with a strength increase of 37%, meeting the requirements of green building materials.

[0023] Optionally, 0.5-1.2 parts of triethanolamine are also selectively added in step S102, and only when the ambient temperature is ≥10°C.

[0024] The early strength effect of the above-mentioned triethanolamine is closely related to temperature. When the ambient temperature is ≥10℃, the molecular activity of triethanolamine is significantly improved, and it plays a role through the following mechanism: the amino group of triethanolamine forms a stable complex with calcium ions and trivalent iron ions in cement, accelerating the hydration reaction of aluminate and silicate. Combined with the ettringite generated by the hydration of sulphoaluminate cement clinker, it quickly forms a skeleton structure, shortens the induction period, and controls the initial setting time within 5 minutes, and increases the 1d compressive strength by 15-20%. When the ambient temperature is <10℃, the molecular motion of triethanolamine slows down, the complexing efficiency decreases, and the workability of concrete may decrease due to excessive early strength, such as decreased fluidity and increased rebound rate. Therefore, it is only added when the temperature is ≥10℃ to balance early strength and construction adaptability.

[0025] Optionally, the setting retarder in step S106 is molasses, and the dosage is adjusted according to the ambient temperature:

[0026] When the temperature is >30℃, the dosage of molasses is reduced to 2-2.5 parts;

[0027] When the temperature is <10℃, the dosage of molasses is increased to 3.5-4 parts.

[0028] The polysaccharides in the above-mentioned molasses are adsorbed on the surface of cement particles through hydroxyl groups, forming a physical barrier to inhibit the dissolution of calcium ions and the hydration reaction of C3A and C3S, thereby delaying the setting time.

[0029] In the high-temperature temperature range where the temperature is >30℃, the hydration reaction is accelerated, and the molecular activity of molasses is improved, but excessive retardation will result in excessively long initial setting time. Therefore, the dosage is reduced to 2-2.5 parts to balance fast hardening and construction requirements. In a 30-35℃ environment, a dosage of 2-2.5 parts of molasses ensures that the initial setting time is ≤10 minutes, the 1d strength is ≥32MPa, and the rebound rate is ≤7.2%, meeting the rapid construction requirements.

[0030] When the temperature is <10℃, the hydration reaction slows down, and the adsorption efficiency of molasses decreases, so the dosage needs to be increased to 3.5-4 parts to maintain sufficient retarding effect and prevent premature hardening of concrete. In a 5-10℃ environment, a dosage of 3.5-4 parts of molasses extends the operable time to 90 minutes, avoiding freezing or uneven hardening of concrete, and the 28d strength of recycled aggregate concrete is increased by 37%.

[0031] Optionally, the above-mentioned finished product is stored in an environment with a humidity of ≤60% and a storage period of ≤6 months.

[0032] The above storage environment humidity ≤60% can effectively inhibit the hygroscopic degradation of hyaluronic acid. The carboxyl and hydroxyl groups in the molecular chain of hyaluronic acid are easy to form hydrogen bonds with water molecules, which will cause the molecular chain to break and the viscosity to decrease, and then lose the water retention capacity. By controlling the humidity, the three-dimensional network structure of hyaluronic acid can be completely preserved. The stainless steel container can prevent the decomposition of hyaluronic acid under light, avoid its degradation into small molecular fragments, and ensure the integrity of the water retention network.

[0033] During storage, the fungicide continuously inhibits the reproduction of microorganisms. Microorganisms can secrete enzymes to decompose the glycosidic bond of hyaluronic acid, resulting in a decrease in molecular weight and loss of function. By controlling humidity and adding 0.1-0.2% fungicide, the biological stability of hyaluronic acid is double guaranteed, and the storage period is extended to 6 months.

[0034] Optionally, the above additive is suitable for recycled aggregate concrete, and the recycled aggregate needs to be pretreated as follows:

[0035] S201: cleaning to remove surface impurities;

[0036] S202: spraying a nano-silicon dioxide water dispersion solution with a mass fraction of 5% on the surface of the aggregate;

[0037] S203: drying the aggregate to a water content ≤5%.

[0038] The pretreated and sprayed nano-SiO2 and the nano-SiO2 in the additive together fill the pores of the aggregate and the paste, forming a "aggregate-paste" double dense structure, improving the early strength and density. The pozzolanic reaction of nano-SiO2 and the fast hardening characteristics of sulphoaluminate cement clinker are synergistic, and the skeleton structure can be quickly formed in high or low temperature environment. Hyaluronic acid forms a three-dimensional gel network in a low humidity environment, adsorbs free water and wraps nano-particles, reducing concrete drying shrinkage and crack generation. The low water absorption of pretreated aggregate combined with the water retention effect of hyaluronic acid maintains the fluidity of concrete, and the rebound rate is controlled at ≤7.2%. The retarder adjusts the dosage according to the environmental temperature, accurately controls the hydration rate, and avoids the rapid hardening of pretreated aggregate due to low water content. N-methyl ethanolamine accelerates the hydration of C3S and C3A by complexing calcium ions, and cooperates with sulphoaluminate cement clinker to achieve "early strength-dense" dual effect.

[0039] Optionally, the above recycled aggregate has a replacement rate of 20-50% in concrete, and is compounded with 10-15% fly ash.

[0040] Firstly, remove surface impurities, reduce fine particle content, and improve aggregate cleanliness. Spray 5% nano-SiO2 water dispersion: nano-particles penetrate aggregate micro-cracks and pores, forming a dense filling layer, strengthening the interface transition zone; at the same time, the pozzolanic activity of nano-SiO2 is activated, reacting with the subsequent cement hydration product Ca(OH)2 to form C-S-H gel, further improving the aggregate-paste bonding strength. Avoid introducing too much free water to ensure that the retarder and N-methyl ethanolamine in the admixture effectively regulate the hydration rate.

[0041] Fly ash particles fill the concrete pores, forming a "nano-micron" dual filling system with nano-SiO2 to improve density. SiO2 and Al2O3 in fly ash react with Ca(OH)2 to form C-S-H gel in an alkaline environment, making up for the strength loss of recycled aggregate. The inert ingredients of fly ash adsorb polycarboxylate superplasticizer, which needs to be accelerated by N-methyl ethanolamine in the admixture to balance the fast hardening and compactness requirements.

[0042] Advantages:

[0043] 1. Through the optimized proportioning and synergistic effect of polycarboxylate superplasticizer, sulphoaluminate cement clinker, sodium silicate, N-methyl ethanolamine, modified nano-silicon dioxide, retarder, and hyaluronic acid, the comprehensive performance of concrete is significantly improved.

[0044] 2. N-methyl ethanolamine and sulphoaluminate cement clinker synergistically promote the rapid hydration of aluminate and silicate phases, forming a ettringite framework, achieving an initial setting time of ≤5 min and a 1d compressive strength of ≥28 MPa.

[0045] 3. The three-dimensional water-retaining network formed by hyaluronic acid effectively adsorbs free water, combined with the dispersion effect of polycarboxylate superplasticizer and the lubricating effect of N-methyl ethanolamine, significantly reduces the rebound rate of shotcrete to ≤7.2%. High density combined with the water-retaining effect of hyaluronic acid gives the concrete excellent impermeability and resistance to chloride ion penetration. DETAILED DESCRIPTION

[0046] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below in combination with the embodiments of the present application. Obviously, the described embodiments are some embodiments of the present application, not all embodiments of the present application.

[0047] Embodiment 1

[0048] The present embodiment provides a concrete admixture, which is composed of the following raw materials by weight: polycarboxylate superplasticizer 35 kg, sulphoaluminate cement clinker 22 kg, sodium silicate 18 kg, N-methyl ethanolamine 10 kg, nano-silicon dioxide 6 kg, retarder 3 kg, and hyaluronic acid 0.03 kg.

[0049] The preparation process is:

[0050] S101: Polycarboxylic acid water reducer and nanosilica are dispersed at 62°C for 28 min to form a uniform slurry.

[0051] S102: Add sodium silicate and N-methyl ethanolamine, and stir at 82°C for 50 min; ambient temperature is 25°C, and no triethanolamine is added.

[0052] S103: Add sulphoaluminate cement clinker and stir for 15 min.

[0053] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg bactericide.

[0054] S105: Inject 1% hyaluronic acid gel at 20°C, and simultaneously perform ultrasonic treatment.

[0055] S106: Add retarder and bactericide, and homogenize for 10 min.

[0056] S107: Pass through a 300-mesh sieve, package in a light-proof stainless steel container, store at a humidity of 50%, and the shelf life is 6 months.

[0057] Example 2

[0058] A concrete admixture is composed of the following raw materials by weight: polycarboxylic acid water reducer 38 kg, sulphoaluminate cement clinker 20 kg, sodium silicate 16 kg, N-methyl ethanolamine 12 kg, nanosilica 7 kg, retarder 2.5 kg, and hyaluronic acid 0.04 kg.

[0059] The preparation process is:

[0060] S101: Polycarboxylic acid water reducer and nanosilica are dispersed at 65°C for 30 min to form a uniform slurry.

[0061] S102: Add sodium silicate and N-methyl ethanolamine, and stir at 85°C for 60 min; ambient temperature is 35°C, and 1.2 kg of triethanolamine is added.

[0062] S103: Add sulphoaluminate cement clinker and stir for 15 min.

[0063] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg bactericide.

[0064] S105: Inject 1% hyaluronic acid gel at 25°C, and simultaneously perform ultrasonic treatment.

[0065] S106: Add retarder and bactericide, homogenize for 10 min.

[0066] S107: Pass through a 300-mesh sieve, package in a light-proof stainless steel container, store at a humidity of 50%, and have a shelf life of 6 months.

[0067] Example 3

[0068] A concrete admixture is composed of the following raw materials by weight: polycarboxylate superplasticizer 32 kg, sulphoaluminate cement clinker 24 kg, sodium silicate 19 kg, N-methyl ethanolamine 9 kg, nano-silicon dioxide 5 kg, retarder 4 kg, and hyaluronic acid 0.02 kg.

[0069] The preparation process is as follows:

[0070] S101: Polycarboxylate superplasticizer and nano-silicon dioxide are dispersed at a high speed for 25 min at 65°C to form a uniform slurry.

[0071] S102: Add sodium silicate and N-methyl ethanolamine, heat to 80°C and stir for 45 min; ambient temperature 8°C, no triethanolamine added.

[0072] S103: Add sulphoaluminate cement clinker and stir for 15 min.

[0073] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, add molasses retarder and 0.15 kg of bactericide.

[0074] S105: Inject 1% hyaluronic acid gel at 18°C, and simultaneously perform ultrasonic treatment.

[0075] S106: Add retarder and bactericide, homogenize for 10 min.

[0076] S107: Pass through a 300-mesh sieve, package in a light-proof stainless steel container, store at a humidity of 50%, and have a shelf life of 6 months.

[0077] Example 4

[0078] A concrete admixture is composed of the following raw materials by weight: polycarboxylate superplasticizer 32 kg, sulphoaluminate cement clinker 24 kg, sodium silicate 19 kg, N-methyl ethanolamine 9 kg, nano-silicon dioxide 5 kg, retarder 4 kg, and hyaluronic acid 0.02 kg.

[0079] The preparation process is as follows:

[0080] S101: Polycarboxylate superplasticizer and nano-silicon dioxide are dispersed at a high speed for 25 min at 65°C to form a uniform slurry.

[0081] S102: Add sodium silicate, N-methyl ethanolamine, and stir at 83°C for 55 min; at ambient temperature 20°C, add 0.8 kg of triethanolamine.

[0082] S103: Add sulfoaluminate cement clinker, and stir for 15 min.

[0083] 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.

[0084] S105: Inject 1% hyaluronic acid gel at 25°C, and simultaneously perform ultrasonic treatment.

[0085] S106: Add retarder and fungicide, and homogenize for 10 min.

[0086] S107: Pass through a 300-mesh sieve, package in a light-proof stainless steel container, store at a humidity of 50%, and have a shelf life of 6 months.

[0087] Example 5

[0088] A concrete admixture consisting of the following ingredients by weight: polycarboxylate superplasticizer 40 kg, sulfoaluminate cement clinker 21 kg, sodium silicate 15 kg, N-methyl ethanolamine 11 kg, nano-silicon dioxide 5 kg, retarder 2.8 kg, and hyaluronic acid 0.01 kg.

[0089] The preparation process is as follows:

[0090] S101: Disperse polycarboxylate superplasticizer and nano-silicon dioxide at 64°C for 29 min to form a uniform slurry.

[0091] S102: Add sodium silicate, N-methyl ethanolamine, and stir at 84°C for 58 min; at ambient temperature 30°C, add 0.5 kg of triethanolamine.

[0092] S103: Add sulfoaluminate cement clinker, and stir for 15 min.

[0093] S104: Cool to 42°C, adjust pH to 9.5 with 30% NaOH, and add molasses retarder and 0.15 kg of fungicide.

[0094] S105: Inject 1% hyaluronic acid gel at 24°C, and simultaneously perform ultrasonic treatment.

[0095] S106: Add retarder and fungicide, and homogenize for 10 min.

[0096] S107: Pass through a 300-mesh sieve, package in a light-proof stainless steel container, store at a humidity of 50%, and have a shelf life of 6 months.

[0097] Comparative Example 1

[0098] The other technical features of the present comparative example are the same as those of Example 1, the nano-silica is not modified by KH-550, and the unmodified nano-SiO2 is directly used in an amount of 6 kg; no nano-SiO2 aqueous dispersion is sprayed in the pretreatment of recycled aggregates.

[0099] Performance comparison:

[0100]

[0101] Conclusion: Unmodified nano-SiO2 has poor dispersibility, cannot effectively fill pores and strengthen the interface, resulting in a significant decrease in strength.

[0102] Comparative Example 2

[0103] The addition of the hyaluronic acid glue solution in step S105 in Example 2 is omitted, and the other steps remain unchanged.

[0104] Performance comparison:

[0105]

[0106] Conclusion: The lack of a hyaluronic acid water-retention network leads to increased concrete drying shrinkage, a significant increase in rebound rate, and a decrease in impermeability.

[0107] Comparative Example 3

[0108] The other technical features remain unchanged from Example 2, and the molasses content is fixed at 3 kg.

[0109] Performance comparison:

[0110]

[0111] Conclusion: Excessive molasses at high temperatures leads to rapid hydration, a short initial setting time, hindered strength development, and increased freeze-thaw damage.

[0112] Comparative Example 4

[0113] The recycled aggregate pretreatment steps S201-S203 are omitted, and the recycled aggregate without washing and nano-SiO2 spraying is directly used; the other steps remain unchanged.

[0114] Performance comparison:

[0115]

[0116] Conclusion: The unpretreated recycled aggregate has many impurities and high porosity, leading to increased strength loss and a significant decrease in durability.

[0117] Comparative Example 5

[0118] Omit the fly ash compounding step, and the replacement rate of the recycled aggregate remains 50%; other steps remain unchanged.

[0119] Performance comparison:

[0120]

[0121] Conclusion: The absence of fly ash leads to insufficient late strength development, increased carbonation depth, and decreased durability.

[0122] To quantify the technical effects of the present application, the following test examples are designed to verify the optimization effects of strength, durability, and workability:

[0123] Test Example 1

[0124] Objective: To verify the "nano-micron" dual filling effect of modified nano-SiO2 and fly ash.

[0125] Method:

[0126] Two groups of concrete are prepared:

[0127] Group A: Example 1 of the present application; modified nano-SiO2 6%, fly ash 12%;

[0128] Group B: Comparative Example 1; unmodified nano-SiO2 5%, no fly ash.

[0129] Test 28d compressive strength, permeability resistance grade, and porosity.

[0130] Results:

[0131]

[0132] Conclusion: Modified nano-SiO2 and fly ash synergistically significantly reduce porosity, improve strength, and improve permeability resistance.

[0133] Test Example 2

[0134] Objective: To verify the effect of hyaluronic acid on the workability and durability of concrete.

[0135] Method:

[0136] Two groups of concrete are prepared:

[0137] Group C: Example 2 of the present application (hyaluronic acid 0.04%);

[0138] Group D: Comparative Example 2 (no hyaluronic acid).

[0139] Test indicators: Test rebound rate, dry shrinkage rate, and 300 freeze-thaw cycle mass loss.

[0140] Results:

[0141]

[0142] Conclusion: The three-dimensional water-retaining 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.

[0143] Test Example 3

[0144] Objective: To verify the dynamic control effect of triethanolamine and molasses retarder.

[0145] Method: Concrete was prepared under high temperature (35℃) and low temperature (8℃) environments, respectively:

[0146] Group E: Example 2 of the present application (add 1.2% triethanolamine under high temperature, and 2.2% molasses);

[0147] Group F: Comparative Example 3 (fixed molasses 3% under high temperature, without triethanolamine).

[0148] Test initial setting time, 1d strength, and freeze-thaw mass loss.

[0149] Results:

[0150]

[0151] Conclusion: Under high temperature, the technology of dynamically adding triethanolamine to accelerate early hydration and appropriately reducing the molasses content effectively balances the fast hardening requirement and the compactness or durability requirement, avoiding the problem of excessive setting and strength or durability reduction caused by fixed high molasses content.

[0152] Test Example 4

[0153] Objective: To verify the comprehensive effect of cleaning, spraying nano-SiO2, and drying of recycled aggregate.

[0154] Method: Two groups of concrete with a recycled aggregate replacement rate of 50% were prepared:

[0155] Group G: The recycled aggregate was pretreated (cleaned, sprayed with 5% nano-SiO2 dispersion, and dried) using the admixture of Example 4 of the present application;

[0156] Group H: The recycled aggregate was not pretreated using the scheme of Comparative Example 4.

[0157] Test index: Strength loss caused by recycled aggregate, increase in flexural strength, and chloride ion penetration depth.

[0158] Results:

[0159]

[0160] Conclusion: The pretreatment process of recycled aggregate significantly strengthens the aggregate-paste interface transition zone, reduces the strength loss caused by recycled aggregate, and improves the flexural strength and chloride ion penetration resistance.

[0161] Test Example 5

[0162] Objective: To verify the contribution of fly ash to later strength and durability.

[0163] Method: Two groups of recycled aggregate replacement rate of 50% concrete were prepared:

[0164] Group I: Using the admixture of Example 4 of the application, compounded with 15% fly ash;

[0165] Group J: Using the scheme of Comparative Example 5.

[0166] Test index: Test 90d strength, carbonation depth.

[0167] Results:

[0168]

[0169] Conclusion: Fly ash compounding significantly improves the later strength and density of concrete through its pozzolanic activity and microaggregate filling effect, effectively inhibiting the development of carbonation depth.

[0170] Through comparative analysis of comparative examples and test examples, the application has the following advantages: nano material modification: modified nano SiO2 and fly ash synergistically improve strength and density; water retention network construction: hyaluronic acid effectively reduces drying shrinkage and improves frost resistance and impermeability; 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 to reduce strength loss; fly ash compounding: improve later strength, inhibit carbonation, and optimize durability.

[0171] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. For those skilled in the art, the present application can have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A concrete admixture characterized in that The polycarboxylic acid water reducing agent 30-40 parts, sulphoaluminate cement clinker 20-25 parts, sodium silicate 15-20 parts, N-methyl ethanolamine 8-12 parts, nano-silicon dioxide 5-8 parts, retarder 2-4 parts, hyaluronic acid 0.01-0.05 parts; The nano-silicon dioxide is modified by KH-550 silane coupling agent, and the silane coupling agent is used in an amount of 1.5-2%.

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 previously dissolved in deionized water to form a 1% glue solution.

3. A method of producing a concrete admixture according to any one of claims 1-2, characterized in that, The method comprises the following steps: S101: Pre-mixing: dispersing the polycarboxylic acid water reducing agent and nano-silicon dioxide at 60-65°C for 25-30 min to form a uniform slurry; S102: Compounding: sequentially adding sodium silicate and organic alcohol amine to the uniform slurry, heating to 80-85°C, and stirring for 45-60 min; S103: Adding sulphoaluminate cement clinker and continuing to stir for 15 min; S104: Adjusting: cooling the mixture to 40-45°C, adjusting the pH to 9-10 with 30% sodium hydroxide solution, adding a retarder and 0.1-0.2% isothiazolinone bactericide; S105: Slowly injecting 1% hyaluronic acid glue solution into the mixture and synchronously performing ultrasonic treatment; S106: Adding a retarder and 0.1-0.2% bactericide and homogenizing for 10 min; S107: Passing through a 300-mesh sieve and packaging in a light-proof stainless steel container.

4. The method of claim 3, wherein the concrete admixture is prepared by adding the compound of formula (I) to the concrete admixture. The hyaluronic acid glue solution needs to be added in an environment below 25°C to avoid high-temperature degradation.

5. The method of claim 3, wherein the concrete admixture is prepared by adding the compound of formula (I) to the concrete mixture. The step S102 further comprises adding 0.5-1.2 parts of triethanolamine, and the addition is only performed when the ambient temperature is ≥10°C.

6. The method of claim 3, wherein the concrete admixture is prepared by adding the compound of formula (I) to the concrete mixture. The retarder in the step S106 is a molasses substance, and the amount of the molasses is adjusted according to the ambient temperature: When the temperature is >30°C, the amount of molasses is reduced to 2-2.5 parts; When the temperature is <10°C, the amount of molasses is increased to 3.5-4 parts.

7. The method of claim 3, wherein the concrete admixture is prepared by adding the compound of formula (I) to the concrete mixture. The finished product is stored in an environment with a humidity of ≤60% and a storage period of ≤6 months.

8. The method of claim 3, wherein the concrete admixture is prepared by adding the compound of formula (I) to the concrete mixture. The method 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% nano-silicon dioxide water dispersion on the surface of the aggregate; S203: Drying the aggregate to a water content of ≤5%.

9. The method of claim 8, wherein the concrete admixture is prepared by adding the compound of formula (I) to a solution of the dispersant and the defoamer. 9 The replacement rate of the recycled aggregate in the concrete is 20-50%, and 10-15% fly ash is compounded.

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