A nano-composite super early-strength agent, its preparation method and application

Abstract

The present invention provides a nano-composite super early-strength agent, a preparation method thereof and an application thereof, belonging to the technical field of chemical admixtures. The α' used in the present invention L -dicalcium silicate and sodium aluminate can form aluminum-doped calcium silicate hydrate. During the synthesis of calcium silicate hydrate, a comb-shaped copolymer with an anion charge ratio of 4000-6000 μeq / g is used to carry out intercalation compound modification on calcium silicate hydrate, obtaining a composite super early-strength agent with an intercalated structure, which can provide more sufficient hydration nucleation sites for calcium silicate minerals, promote cement hydration, accelerate heat release during hydration, and the intercalated structure increases the layer spacing of calcium silicate hydrate and increases the number of crystal nuclei (one composite molecule can serve as two crystal nuclei), thereby reducing the dosage of the super early-strength agent. At the same time, the comb-shaped copolymer can make the composite super early-strength agent uniformly dispersed to avoid agglomeration, increase the number of crystal nuclei and reduce the dosage of the super early-strength agent.

Description

Technical Field

[0001] The present invention relates to the technical field of chemical admixtures, and in particular to a nano-composite super-early-strength agent and its preparation method and application. Background Art

[0002] Concrete early-strength agents are widely used in practical engineering, especially for additive manufacturing and precast building components. It can shorten the production cycle and improve the product turnover rate by accelerating the hydration of cement. The unreasonable use of traditional early-strength agents such as chloride-based early-strength agents will cause corrosion to steel bars, and triethanolamine early-strength agents are not suitable for autoclaved concrete, etc. Therefore, new types of super-early-strength agents have emerged. The incorporation of super-early-strength agents will provide additional nucleation sites for the already formed hydrated product calcium silicate hydrate, reduce the nucleation barrier, promote the hydration of tricalcium silicate, and the more nucleation sites provided, the faster the hydration reaction will accelerate.

[0003] At present, the particle size of super-early-strength agents is mainly in the micron range. At the same dosage, the number of nucleation sites provided by them is significantly less than that of the nano-scale, and the early-strength effect is weak. Therefore, the development and utilization of nano-super-early-strength agents meet the market demand and the direction of technological development.

[0004] If the nano-super-early-strength agent is not fully dispersed during use, its performance will be reduced due to agglomeration, resulting in too high a dosage requirement during use. At present, the dosage of the used early-strength agent is mainly 1-5%wt of the cementitious material, which is a very high data in the cement admixture industry.

[0005] Patent CN 112194405 A discloses "a preparation method and application of an early-strength additive for carbide slag", and its preparation method is to take 20-60 parts by mass of carbide slag and 0.5-1 part by mass of dispersant, add 80-160 parts by mass of water and mix and stir, and obtain carbide slag slurry through screening. Add grinding aids with a content of 0.5‰-1.5‰ of the carbide slag solid content in the carbide slag slurry, plasticizers with a content of 5-25‰ of the carbide slag solid content in the carbide slag slurry, and 300-400 parts by mass of grinding media to the carbide slag slurry, grind in a wet mill, screen the grinding media to obtain carbide slag ultra-fine slurry, and add an anti-agglomeration stabilizer to the carbide slag ultra-fine slurry and stir to obtain the carbide slag super-early-strength additive. The prepared carbide slag super-early-strength additive is added to the cementitious material at 3-7%wt, which can significantly enhance the early strength of the cementitious material, but the preparation process is relatively complex and the dosage is high.

[0006] Patent CN 108101406 B discloses "a super early-strength concrete accelerator and its preparation method". The components of the accelerator of this invention include 860 - 880 parts of water, 70 - 75 parts of diethylene glycol monobutyl ether, 40 - 45 parts of polyethylene glycol, 10 - 20 parts of isopropyl alcohol, 1850 - 1950 parts of soluble inorganic salt solution, and 5 - 5.5 parts of alkaline regulator. Using the accelerator provided by this invention, the 8-hour compressive strength of the concrete can reach more than 60% of the design strength under normal temperature and pressure and 95% humidity curing, shortening the demolding time, accelerating the mold turnover speed, and the later strength will not shrink back. However, when incorporated into the concrete at a ratio of 5.0% of the cementitious material, the dosage is too high.

[0007] Patent CN 114956647 A discloses "a shrinkage-reducing composite nano-hydrated calcium silicate accelerator and its preparation method". This accelerator is prepared by reacting a calcium salt component, a silicate component, and a shrinkage-reducing and dispersing component with a mass ratio of (0.2 - 0.6):(0.4 - 0.7):1. Among them, the shrinkage-reducing and dispersing component is an aqueous solution containing 1% - 3% of shrinkage-reducing polycarboxylate superplasticizer and 3% - 9% of polycarboxylate dispersant by mass fraction. When the dosage of this shrinkage-reducing composite nano-hydrated calcium silicate accelerator is 5%, it can effectively improve the early strength of the mortar. However, the influence of the later strength development is not considered, and the dosage is relatively high.

[0008] In summary, the above-mentioned prior arts prepare accelerators by different methods to improve the early strength of cement-based materials, but do not fully consider the influence of the particle size and dispersibility of the accelerators, and the dosage is relatively high when used. Summary of the Invention

[0009] The purpose of the present invention is to provide a nano-composite super early-strength agent, its preparation method and application. The nano-composite super early-strength agent has a nano-scale size, excellent dispersibility, and a low dosage.

[0010] In order to achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0011] The present invention provides a nano-composite super early-strength agent, which includes the following preparation raw materials in parts by mass:

[0012] α’ L - dicalcium silicate 7.5 - 13.5 parts, sodium aluminate 1 - 3.8 parts, comb-shaped copolymer 2 - 2.5 parts, suspension dispersant 2 - 2.5 parts, water 80 - 85 parts;

[0013] The specific anionic charge density of the comb-shaped copolymer is 4000 - 6000 μeq / g.

[0014] Preferably, the specific surface area of the α’ L - dicalcium silicate is 450 - 550 m 2 / kg.

[0015] Preferably, the grafting density of the comb copolymer is 8-10%, the degree of polymerization of the main chain is 15-30, and the degree of polymerization of the side chain is 26-76.

[0016] Preferably, the suspension dispersant is ethylenediaminetetraethanol.

[0017] The present invention provides a preparation method of the nano-composite super-early-strength agent described in the above technical solution, including the following steps:

[0018] Mix water, comb copolymer, suspension dispersant, sodium aluminate and α' L -dicalcium silicate, and carry out a sol-gel reaction under shear stirring conditions to obtain a nano-composite super-early-strength agent.

[0019] Preferably, the temperature of the sol-gel reaction is 90±5°C, and the time is 20-30h.

[0020] The present invention provides the application of the nano-composite super-early-strength agent described in the above technical solution or the nano-composite super-early-strength agent prepared by the preparation method described in the above technical solution in additive manufacturing and prefabrication of building components, low-carbon cement-based materials or low-temperature concrete.

[0021] Preferably, based on the solid mass fraction, the dosage of the nano-composite super-early-strength agent is 0.2-0.5% of the mass of the cementitious material.

[0022] The present invention provides a nano-composite super-early-strength agent. The α' L -dicalcium silicate and sodium aluminate can form aluminum-doped calcium silicate hydrate. During the formation of calcium silicate hydrate, the comb copolymer with an anionic charge ratio of 4000-6000 μeq / g is used to intercalate and modify the calcium silicate hydrate to obtain a composite super-early-strength agent with an intercalated structure, which can provide more sufficient hydration nucleation sites for calcium silicate minerals, promote cement hydration, accelerate heat release during hydration, and the intercalated structure increases the layer spacing of calcium silicate hydrate and increases the number of crystal nuclei (one composite molecule can act as two crystal nuclei), thereby reducing the dosage of the super-early-strength agent (only 0.2%-0.5% of the mass of the cementitious material). At the same time, the comb copolymer can make the composite super-early-strength agent evenly dispersed and avoid agglomeration, increase the number of crystal nuclei, and reduce the dosage of the super-early-strength agent.

[0023] The nano-composite super-early-strength agent provided by the present invention can maintain a nano-dispersed state under the action of suspension dispersion, improve the use efficiency of the nano-super-early-strength agent, reduce its dosage in the cementitious material, which is only 0.2% - 0.5% of the mass of the cementitious material, and shows outstanding super-early-strength effect, effectively promoting the early strength development of low-temperature and negative-temperature concrete, solving the problem that the hydration calcium silicate crystal nucleus type super-early-strength agent is prone to agglomeration and efficiency reduction, endowing additive manufacturing and precast building components with steam-free energy-saving curing, and promoting the early strength development of low-carbon cementitious materials, low-temperature and negative-temperature concrete.

[0024] The nano-composite super-early-strength agent of the present invention is prepared by the sol-gel method, with simple process, and the raw materials used are non-toxic, harmless and easily available. Description of the Drawings

[0025] Figure 1 It is the transmission electron microscope image of the nano-composite super-early-strength agent prepared in Example 4. Detailed Description of the Invention

[0026] The present invention provides a nano-composite super-early-strength agent, which includes the following preparation raw materials in parts by mass:

[0027] α’ L 7.5 - 13.5 parts of dicalcium silicate, 1 - 3.8 parts of sodium aluminate, 2 - 2.5 parts of comb-shaped copolymer, 2 - 2.5 parts of suspension dispersant, 80 - 85 parts of water;

[0028] The specific anion charge density of the comb-shaped copolymer is 4000 - 6000 μeq / g.

[0029] In the present invention, unless otherwise specified, the required preparation raw materials are all commercially available products well-known to those skilled in the art.

[0030] In parts by mass, the preparation raw materials of the nano-composite super-early-strength agent provided by the present invention include α’ L 7.5 - 13.5 parts of dicalcium silicate, more preferably 9 - 11.2 parts. In the present invention, the specific surface area of the α’ L -dicalcium silicate is preferably 450 - 550 m 2 / kg, more preferably 500 m 2 / kg.

[0031] Based on the mass fraction of the α’ L -dicalcium silicate, the preparation raw materials of the nano-composite super-early-strength agent provided by the present invention include 1 - 3.8 parts of sodium aluminate, preferably 1.5 - 2.5 parts.

[0032] Based on the mass fraction of the α’ LBased on the parts by mass of dicalcium silicate, the raw materials for preparing the nano-composite super early-strength agent provided by the present invention include 2 to 2.5 parts of a comb-shaped copolymer, preferably 2.2 to 2.4 parts. In the present invention, the specific anionic charge density of the comb-shaped copolymer is 4000 to 6000 μeq / g, preferably 5000 μeq / g; the grafting density of the comb-shaped copolymer is preferably 8 to 10% (more preferably 9%), the degree of polymerization of the main chain is preferably 15 to 30 (more preferably 20), and the degree of polymerization of the side chain is preferably 26 to 76 (more preferably 46). The present invention has no special requirements for the source of the comb-shaped copolymer, and conventional commercially available products in the art can be used.

[0033] Based on the α’ L Based on the parts by mass of dicalcium silicate, the raw materials for preparing the nano-composite super early-strength agent provided by the present invention include 2 to 2.5 parts of a suspension dispersant, preferably 2 parts. In the present invention, the suspension dispersant is preferably ethylenediamine tetraethanol.

[0034] Based on the α’ L Based on the parts by mass of dicalcium silicate, the raw materials for preparing the nano-composite super early-strength agent provided by the present invention include 80 to 85 parts of water, preferably 81 parts.

[0035] The present invention provides a method for preparing the nano-composite super early-strength agent according to the above technical solution, including the following steps:

[0036] Mix water, a comb-shaped copolymer, a suspension dispersant, sodium aluminate and α’ L -dicalcium silicate, and carry out a sol-gel reaction under shear stirring conditions to obtain a nano-composite super early-strength agent.

[0037] In the present invention, the mixing of water, a comb-shaped copolymer, a suspension dispersant, sodium aluminate and α’ L -dicalcium silicate is preferably to add accurately measured water into a hydrothermal reaction kettle with a high-speed shear stirring device, start stirring, and sequentially add a comb-shaped copolymer, a suspension dispersant, sodium aluminate and α’ L -dicalcium silicate; the present invention has no special limitation on the stirring, and the materials can be mixed evenly according to the process well-known in the art.

[0038] In the present invention, the temperature of the sol-gel reaction is preferably 90 ± 5 °C, and the time is preferably 20 to 30 h. The present invention has no special limitation on the shear stirring conditions, and the materials can be mixed evenly according to the process well-known in the art.

[0039] During the sol-gel reaction, α’ LDicalcium silicate reacts with sodium aluminate to form aluminum-doped calcium silicate hydrate, which is then compounded with a comb-shaped copolymer. The aluminum-doped calcium silicate hydrate is a colloidal material with a CaO / (SiO2+Al2O3) molar ratio of 1.5 to 1.8, and the doping rate of aluminum at the molecular bridge position of calcium silicate hydrate is 0.06 to 0.12.

[0040] After completing the sol-gel reaction, the present invention preferably cools the obtained product to 50°C and turns off the stirring to obtain a nano-composite super-early strength agent. In the present invention, the nano-composite super-early strength agent is in a slurry state.

[0041] The present invention provides the application of the nano-composite super-early strength agent described in the above technical solution or the nano-composite super-early strength agent prepared by the preparation method described in the above technical solution in additive manufacturing, prefabrication of building components, low-carbon cement-based materials or low-temperature concrete. The present invention has no special limitation on the application method, and it can be applied according to the methods well known in the art.

[0042] In the present invention, based on the solid mass fraction, the dosage of the nano-composite super-early strength agent is preferably 0.2 to 0.5% of the mass of the cementitious material.

[0043] Next, the technical solutions in the present invention will be clearly and completely described in conjunction with the examples in the present invention. Obviously, the described examples are only a part of the examples of the present invention, rather than all the examples. All other examples obtained by those of ordinary skill in the art based on the examples in the present invention without creative efforts shall fall within the protection scope of the present invention.

[0044] Example 1

[0045] By mass, the raw materials are: α'-dicalcium silicate with a specific surface area of 450 m 2 / kg 7.5 parts, sodium aluminate 2.5 parts, comb-shaped copolymer 2.5 parts, suspension dispersant (ethylenediaminetetraethanol) 2.5 parts, and water 85 parts. L Among them, the grafting density of the comb-shaped copolymer is 8%, the degree of polymerization of the main chain is 30, the degree of polymerization of the side chain is 76, and the specific anion charge density is 4000 μeq / g.

[0046]

[0047] The preparation steps are as follows:

[0048] Accurately measure the water and add it to a hydrothermal reactor equipped with a high-speed shear stirring device, and start stirring; sequentially add the comb-shaped copolymer, suspension dispersant, sodium aluminate, and α'- L dicalcium silicate; heat to 90°C and continuously carry out a sol-gel reaction for 20 h under high-speed shear stirring; cool to 50°C and turn off the stirring to obtain a nano-composite super-early strength agent. ​

[0049] Example 2

[0050] By mass, the raw materials are: α’ 2 -dicalcium silicate with a specific surface area of 500 m L / kg, 9 parts of sodium aluminate, 2.5 parts of comb copolymer, 2.5 parts of suspension dispersant (ethylenediaminetetraethanol), and 85 parts of water.

[0051] Among them, the grafting density of the comb copolymer is 10%, the main chain polymerization degree is 20, the side chain polymerization degree is 26, and the specific anionic charge density is 6000 μeq / g.

[0052] The preparation steps are as follows:

[0053] Add accurately measured water into a hydrothermal reactor equipped with a high-speed shear stirring device, and start stirring; successively add the comb copolymer, suspension dispersant, sodium aluminate, and α’ L -dicalcium silicate; heat to 90 °C, and continuously carry out a sol-gel reaction under high-speed shear stirring for 30 h; cool down to 50 °C, turn off the stirring, and obtain a nano-composite super-early-strength agent.

[0054] Example 3

[0055] By mass, the raw materials are: α’ 2 -dicalcium silicate with a specific surface area of 550 m L / kg, 11.2 parts of sodium aluminate, 3.8 parts of comb copolymer, 2 parts of suspension dispersant (ethylenediaminetetraethanol), and 81 parts of water.

[0056] Among them, the grafting density of the comb copolymer is 9%, the main chain polymerization degree is 15, the side chain polymerization degree is 46, and the specific anionic charge density is 5000 μeq / g.

[0057] The preparation steps are as follows:

[0058] Add accurately measured water into a hydrothermal reactor equipped with a high-speed shear stirring device, and start stirring; successively add the comb copolymer, suspension dispersant, sodium aluminate, and α’ L -dicalcium silicate; heat to 90 °C, and continuously carry out a sol-gel reaction under high-speed shear stirring for 20 h; cool down to 50 °C, turn off the stirring, and obtain a nano-composite super-early-strength agent.

[0059] Example 4

[0060] By mass, the raw materials are: α’ 2 -dicalcium silicate with a specific surface area of 500 m L / kg, 13.5 parts of sodium aluminate, 2 parts of comb copolymer, 2 parts of suspension dispersant (ethylenediaminetetraethanol), and 81 parts of water.

[0061] Among them, the grafting density of the comb copolymer is 10%, the degree of polymerization of the main chain is 20, the degree of polymerization of the side chain is 76, and the specific anionic charge density is 5000 μeq / g.

[0062] The preparation steps are as follows:

[0063] Add accurately measured water into a hydrothermal reactor equipped with a high-speed shear stirring device, and start stirring; sequentially add the comb copolymer, suspension dispersant, sodium aluminate and α' L -dicalcium silicate; heat to 90 °C, continuously carry out a sol-gel reaction under high-speed shear stirring for 30 h, cool down to 50 °C, and turn off the stirring to obtain a nano-composite super-early strength agent.

[0064] Performance test

[0065] 1) Figure 1 It is the transmission electron microscope image of the nano-composite super-early strength agent prepared in Example 4; from Figure 1 it can be seen that the particle size of the nano-composite super-early strength agent is between 40 and 60 nm, and its intercalated structure can be seen.

[0066] 2) Incorporate the nano-composite super-early strength agents prepared in Examples 1 to 4 into cement at 0.2% and 0.5% of the mass of the gelling material respectively. Comparative Example 1 is without the nano-composite super-early strength agent of the present invention. The water-cement ratio is set to 0.4. Measure the heat of hydration of the cement paste within 24 hours at a temperature of 20 °C. The obtained results are shown in Table 1.

[0067] Table 1 Hydration properties of cement doped with the nano-composite super-early strength agents of Examples 1 to 4

[0068]

[0069] It can be seen from Table 1 that the incorporation of the nano-composite super-early strength agents of Examples 1 to 4 significantly increases the heat release of the cement at 12 h and 24 h. The maximum increase in the heat release at 12 h is 114.55%, and the time of the heat release peak in the hydration acceleration period is advanced, with the maximum advance of 289 min, proving that the nano-composite super-early strength agent of the present invention has a significant promoting effect on cement hydration.

[0070] 3) Incorporate the nano-composite super early-strength agents prepared in Example 1 and Example 2 into the mix proportion of B06 grade autoclaved aerated concrete at 0.2% and 0.5% of the mass of the cementitious materials respectively. Comparative Example 2 is without the nano-composite super early-strength agent of the present invention. Cement: fly ash: quicklime: gypsum dihydrate = 10:20:3:1, water-binder ratio is 0.54, the dosage of the foam stabilizer is 0.02% of the cementitious materials, and the dosage of aluminum powder is 0.11% of the cementitious materials. Mix cement, fly ash, quicklime and gypsum dihydrate and add them to a mixer for low-speed stirring for 2 min, then add the nano-composite super early-strength agent, foam stabilizer of the present invention and 40 °C water for rapid stirring for 2 min. Stir the aluminum powder evenly in the remaining 40 °C water and add it to the mixer for rapid stirring for 2 min. Inject the slurry into a mold of 100 mm×100 mm×100 mm for foaming, place it in a steam box at 60 °C for static setting for 4 h, then cut off the top part and remove the mold. Place the block in a curing box at 60 °C for steam curing for 24 h, and then take out the block after natural curing to the age, place it in an oven and dry it to the specified moisture content (8% - 12%). Then, conduct compressive strength tests according to the requirements in GB / T 11968 - 2008 "Test Methods for Properties of Autoclaved Aerated Concrete". The obtained results are shown in Table 2.

[0071] Table 2 Properties of Concrete Incorporating Nano-Composite Super Early-Strength Agents of Examples 1 - 2

[0072]

[0073] As can be seen from Table 2, the incorporation of the nano-composite super early-strength agents of Example 1 and Example 2 significantly improves the compressive strength of low-temperature concrete at 7d, 14d, and 28d. The highest increase in 7d compressive strength is 49.60%, enabling the B06 grade autoclaved aerated concrete to meet the specified strength grade requirements under the condition of non-autoclaved curing, and realizing the preparation of low-carbon and energy-saving autoclaved aerated concrete without autoclaving.

[0074] 4) Incorporate the nano-composite super early-strength agents of Example 3 and Example 4 into the mix proportion of C50 concrete at 0.2% and 0.5% of the mass of the cementitious materials respectively. Mix the concrete under the temperature condition of 5 - 15 °C. Comparative Example 3 is without the nano-composite super early-strength agent of the present invention. Water-cement ratio is 0.35, sand ratio is 35%, the ratio of cementitious materials to sand and gravel is 1:3.8, and 0.7% of polycarboxylate water reducer is added. The mixed concrete is formed into specimens with dimensions of 150 mm×150 mm×150 mm. After forming, cure the specimens under the temperature condition of 5 - 15 °C for 8h, 16h, 24h, 3d, 7d, and 28d. Refer to GB\T50081 - 2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete" to test the compressive strength of the concrete. The obtained results are shown in Table 3.

[0075] Table 3 Properties of Concrete Incorporating Nano-Composite Super Early-Strength Agents of Examples 3 - 4

[0076]

[0077]

[0078] As can be seen from Table 3, the incorporation of the nano-composite super early-strength agent in Example 3 and Example 4 has little effect on the workability of the concrete, and significantly improves the compressive strength of the low-temperature concrete at 8h, 16h, and 24h. The 8h compressive strength is increased by up to 547.36%, the 16h compressive strength is increased by up to 370.37%, and the 24h compressive strength is increased by up to 191.47%. It also has a certain promoting effect on the later strength development, meets the strength requirements of C50 concrete, and realizes the early strength improvement of low-temperature concrete without steam curing.

[0079] The above are only the preferred embodiments of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can still be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A nano-composite super early strength agent, characterized in that, Comprising the following preparation raw materials in parts by mass: α’ L - 7.5 to 13.5 parts of dicalcium silicate, 1 to 3.8 parts of sodium aluminate, 2 to 2.5 parts of comb copolymer, 2 to 2.5 parts of suspension dispersant, 80 to 85 parts of water; The specific anionic charge density of the comb copolymer is 4000-6000 μeq / g; the grafting density of the comb copolymer is 8-10%, the degree of polymerization of the main chain is 15-30, and the degree of polymerization of the side chain is 26-76; The suspension dispersant is ethylenediamine tetraethanol.

2. The nano-composite super early-strength agent according to claim 1, characterized in that The said α' L - The specific surface area of dicalcium silicate is 450 to 550 m 2 / kg.

3. The preparation method of the nano-composite super early-strength agent according to claim 1 or 2, characterized in that, Comprising the following steps: Mix water, comb copolymer, suspension dispersant, sodium aluminate and α’ L -dicalcium silicate, and carry out a sol-gel reaction under shear stirring conditions to obtain a nano-composite super-early strength agent.

4. The preparation method according to claim 3, characterized in that, The temperature of the sol-gel reaction is 90±5°C and the time is 20-30 h.

5. Application of the nano-composite super early-strength agent described in claim 1 or 2 or the nano-composite super early-strength agent prepared by the preparation method described in any one of claims 3-4 in additive manufacturing and prefabrication of building components, low-carbon cement-based materials or low-temperature concrete.

6. The application according to claim 5, characterized in that Based on the solid mass parts, the dosage of the nano-composite super early-strength agent is 0.2-0.5% of the mass of the cementitious material.

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