High-performance nano hydrated calcium silicate early strength agent as well as preparation method and application thereof

Abstract

The invention discloses a high-performance nano hydrated calcium silicate early strength agent as well as a preparation method and application thereof, and belongs to the technical field of concrete admixtures. The method comprises the following steps: S1, preparing a calcium source aqueous solution, a silicon source aqueous solution, an aluminum source aqueous solution and a magnesium source aqueous solution; s2, dissolving polyol amine and a polyether monomer in water, adding a catalyst, pre-polymerizing for 2-4 hours under a stirring condition, then adding N-isopropylacrylamide and an initiator, reacting for 3-5 hours, and centrifuging and drying to obtain a polyol amine-temperature-sensitive polyether copolymer; s3, dissolving the polyol amine-temperature-sensitive polyether copolymer, sodium gluconate and a polycarboxylate superplasticizer in water to obtain a composite modifier aqueous solution; and S4, dropwise adding the calcium source aqueous solution, the silicon source aqueous solution, the aluminum source aqueous solution and the magnesium source aqueous solution into the composite modifier aqueous solution at the same time, adjusting the pH value to 11.5-12.8, carrying out a stirring reaction at 20-50 DEG C for 3-8 h, and adding the defoaming agent and the corrosion inhibitor after the reaction is finished, thereby obtaining the composite modifier. The obtained early strength agent is good in long-term stability and excellent in early strength performance.

Description

Technical Field

[0001] This invention relates to the field of concrete admixture technology, and more specifically, to a high-performance nano-hydrated calcium silicate early strength agent, its preparation method, and its application. Background Technology

[0002] With the rapid development of industrialized construction, the application scenarios of prefabricated construction, 3D printed concrete, ultra-early strength rapid repair, and low-temperature construction and emergency rescue are expanding rapidly, making the demand for high early strength of cement-based materials during construction increasingly urgent. Traditional admixture technology mainly relies on chloride salts, sulfates, nitrites, or organic alcohol amines as early strength components. Although they can shorten the setting time and improve early strength to a certain extent, they also bring problems such as steel corrosion, alkali-aggregate reaction risks, later strength reduction, and poor compatibility with polycarboxylate superplasticizers. In addition, they are not adaptable to the environment, cannot meet the requirements for construction in a wide temperature range, and are not suitable for pumping construction and other working conditions, which seriously restricts their promotion and application in high-performance concrete.

[0003] Nano-hydrated calcium silicate (CSH) seed crystals have attracted much attention due to their homogeneity with cement hydration products, ability to lower the nucleation energy barrier, and significant shortening of the induction period. However, nano-CSH has high surface energy, is prone to agglomeration leading to increased particle size, and suffers from poor dispersion stability and short shelf life due to the high ionic strength and highly alkaline pH environment in cement pore liquid. Furthermore, this type of nucleation accelerator generally has low solid content, resulting in high transportation and storage costs, which severely restricts its engineering application. To address these common problems of nucleation accelerators, numerous studies have utilized organic-inorganic hybrid methods to perform single-surface modification of nano-CSH. Chinese patent CN114804709A utilizes polycarboxylate superplasticizers to inhibit the agglomeration of nano-CSH crystal nuclei during synthesis, achieving partial dispersion of the solution through the steric hindrance of long side chains. However, it still cannot solve the problem of long-term sedimentation upon standing. Furthermore, this material is temperature-sensitive; at high temperatures, it causes cement-based materials to lose their water-reducing and slump-preserving properties. Chinese patent CN111253107B introduces alkanolamine molecules to stabilize the dispersibility of nano-CSH, inducing complexation, effectively refining the crystal nucleus size, and significantly improving early strength. Although it can complex with Ca... 2+ While regulating the hydration process, the addition of alcoholic amines as modifiers in solution systems can cause dosage sensitivity, affecting the rheological properties of the slurry. Furthermore, their compatibility with nano-CSH nucleation early strength agent systems is poor. This demonstrates that traditional single-component modification can only achieve local optima in specific dimensions, but it is difficult to simultaneously satisfy the global optima, thus restricting the practical engineering application of nano-CSH. Therefore, a novel nano-CSH nucleation early strength agent system that can simultaneously solve the above problems is needed.

[0004] In addition, impurity ion doping is considered an effective way to improve the performance of CSH. Chinese patent CN109095807A provides a method for introducing Al into the CSH structure. 3+ The novel nucleation early strength agent effectively controls the aggregation effect. However, the above-mentioned single modification methods all have defects such as single function, narrow adaptability and insufficient long-term stability. It is of great significance to develop a new generation of highly dispersed, long-term stable and ultra-early strength nano-CSH nucleation early strength agent so as to further improve the nucleation activity and make it simultaneously meet the multi-objective coupling requirements of "dispersion-stability-early strength-rheology". Summary of the Invention

[0005] To address the shortcomings of existing technologies, one of the objectives of this invention is to provide a method for preparing a high-performance nano-hydrated calcium silicate early strength agent. This method solves the problems of easy agglomeration and poor long-term stability of traditional CSH crystal nuclei through composite modification, and also achieves a leap in the early strength performance of CSH through dual ion doping, making it better suited for concrete construction engineering.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] A method for preparing a high-performance nano-hydrated calcium silicate early strength agent includes the following steps:

[0008] S1. Dissolve the calcium source, silicon source, aluminum source and magnesium source in water respectively to obtain aqueous solutions of calcium source, silicon source, aluminum source and magnesium source;

[0009] S2. Dissolve polyol amine and polyether monomer in water, add catalyst and prepolymerize for 2-4 hours under stirring, then add N-isopropylacrylamide and initiator, react for 3-5 hours, and obtain polyol amine-thermosensitive polyether copolymer after centrifugation and drying.

[0010] S3. Dissolve the polyol amine-thermosensitive polyether copolymer obtained in step S2 with sodium gluconate and polycarboxylate superplasticizer in water, and mix thoroughly to obtain an aqueous solution of composite modifier;

[0011] S4. Simultaneously add the aqueous solutions of calcium source, silicon source, aluminum source, and magnesium source to the aqueous solution of the composite modifier, adjust the pH to 11.5~12.8, stir and react at 20~50℃ for 3~8h, and after the reaction is completed, add the defoamer and corrosion inhibitor to obtain the high-performance nano-hydrated calcium silicate early strength agent.

[0012] This invention involves doping Al into an early strength agent. 3+ and Mg 2+ Mg 2+ It can partially replace calcium ions in CSH and participate in the construction of new CMSH structures. 3+It can partially replace silicon ions in CSH and participate in the construction of new CASH structures; this invention double-doped Al 3+ and Mg 2+ The obtained crystal nuclei are foil-shaped as a whole, and the overlap between nanoparticles is low, which refines the crystal nucleus size. The foil-shaped morphology has higher activity than the spherical morphology, indicating that the incorporation of dual ions promotes the formation of gel network. This network provides a larger specific surface area, promotes crystal nucleation and growth, exhibits a more significant nucleation effect, is more conducive to exerting the seed effect of crystal nuclei, increases more nucleation sites, promotes the generation of hydration products, makes the cement more compact, and further improves its strength.

[0013] Furthermore, a composite modifier composed of polyol amine-thermosensitive polyether copolymer, sodium gluconate, and polycarboxylate superplasticizer was used for surface modification to improve the dispersibility and stability of the nano-CSH early-strength agent. There is a competitive adsorption relationship between sodium gluconate and polycarboxylate superplasticizer; an appropriate amount of sodium gluconate can enhance the steric hindrance effect of polycarboxylate superplasticizer. Sodium gluconate and polycarboxylate enhance the steric hindrance effect by bridging calcium ions, thereby improving the dispersibility and stability of the system. In addition, the polyol amine-thermosensitive polyether copolymer enables the nano-CSH early-strength agent to achieve intelligent regulation of low-temperature accelerated hydration and high-temperature inhibited setting in ordinary silicate cement systems within the temperature range of 5–40℃. This is beneficial for the formation of early-stage structures in cement-based materials, promotes strength development, and significantly improves the rheological properties of the slurry under complex construction conditions.

[0014] Preferably, the molar ratio of calcium to silicon is (0.5~2):1, the molar ratio of aluminum to silicon is (0.02~0.45):1, and the molar ratio of magnesium to silicon is (0.02~0.45):1.

[0015] Preferably, in step S2, the mass ratio of the polyol amine, polyether monomer, and N-isopropylacrylamide is (3~8):1:(2~6);

[0016] Preferably, the catalyst is sodium hydride or potassium naphthalene, and the initiator includes persulfate initiators.

[0017] Preferably, in the aqueous solution of the composite modifier, the concentration of the polyol amine-thermosensitive polyether copolymer is 1wt%~10wt%, the concentration of sodium gluconate is 0.05wt%~5wt%, and the effective concentration of the polycarboxylate superplasticizer is 0.5wt%~8wt%.

[0018] Preferably, the mass ratio of solid content in the polyol amine-thermosensitive polyether copolymer, sodium gluconate and polycarboxylate superplasticizer is (1~5):1:(1~4).

[0019] Preferably, the calcium source includes at least one of calcium nitrate tetrahydrate, calcium chloride dihydrate, calcium carbonate, calcium sulfate, calcium phosphate, calcium formate, calcium fluoride, calcium oxide, calcium citrate, calcium hydrogen phosphate, and calcium bicarbonate.

[0020] Preferably, the silicon source includes at least one of sodium silicate, potassium silicate, lithium silicate, nano-silica powder, tetraethyl orthosilicate, and tetramethyl silicate.

[0021] Preferably, the aluminum source includes at least one of aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum sulfate octadecahydrate, sodium aluminate, potassium aluminate, and lithium aluminate.

[0022] Preferably, the magnesium source includes at least one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, magnesium carbonate, and magnesium oxide.

[0023] Preferably, the polyol amine includes at least one of triethanolamine, diethanolamine, N-methyldiethanolamine, triisopropanolamine, and diethanolmonoisopropanolamine.

[0024] Preferably, the polyether monomer includes at least one of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer.

[0025] Preferably, in the high-performance nano-hydrated calcium silicate early strength agent of the present invention, the molar concentration of the calcium source is 0.1~0.5 mol / L.

[0026] Preferably, in the high-performance nano-hydrated calcium silicate early strength agent of the present invention, the concentration of the polyol amine-thermosensitive polyether copolymer is 0.5wt%~7wt%.

[0027] Preferably, in step S4, during the process of adding the calcium source aqueous solution, silicon source aqueous solution, aluminum source aqueous solution and magnesium source aqueous solution to the composite modifier aqueous solution, the dropping rate of the four is 5.5~15mL / h, and the dropping time is 2~4h.

[0028] Preferably, in the high-performance nano-hydrated calcium silicate early strength agent of the present invention, the concentration of the defoamer is 0.01wt%~0.5wt%, and the concentration of the corrosion inhibitor is 0.01wt%~0.20wt%.

[0029] Preferably, the defoamer includes at least one of silicone defoamers, polyether defoamers, and polyether-modified polysiloxane defoamers; the corrosion inhibitor is an organic corrosion inhibitor.

[0030] Another objective of this invention is to provide a high-performance nano-hydrated calcium silicate early strength agent prepared by the aforementioned preparation method.

[0031] Another object of the present invention is to provide the application of the high-performance nano-hydrated calcium silicate early strength agent prepared by the preparation method in concrete, wherein the dosage of the early strength agent is 0.8% to 2.5% of the mass of the cementitious material.

[0032] Compared with the prior art, the advantages of the present invention are:

[0033] (1) The present invention achieves this by simultaneously doping Al into the early strength agent. 3+ and Mg 2+ This significantly enhances the hydration-promoting effect of early-strength agents on cement, thereby increasing the early strength of concrete. Furthermore, by using a composite modifier composed of polyol amine-thermosensitive polyether copolymer, sodium gluconate, and polycarboxylate superplasticizer to improve the dispersibility and stability of nano-CSH early-strength agents, a dual-ion doped CSH nucleus early-strength agent with excellent dispersibility, high stability, no obvious precipitation phenomenon after 90 days, and a particle size at the nanoscale was successfully prepared.

[0034] (2) When the early strength agent of the present invention is applied to cement-based materials, it exhibits intelligent regulation of accelerating hydration at low temperature and inhibiting coagulation at high temperature, thereby achieving a global performance improvement that synergistically enhances early strength performance and rheological performance, and has a wide range of applicable temperature ranges.

[0035] (3) The early strength agent of the present invention also shows significant advantages in concrete workability, durability and environmental friendliness. It breaks through the problems of easy agglomeration, low early strength efficiency, complex process and short storage period of traditional nano CSH. It does not require high pressure, inert atmosphere or expensive solvents and has the feasibility of industrial production. Attached Figure Description

[0036] Figure 1 This is a photograph of the nano-CSH nucleation early strength agent prepared in Example 3 after standing for 90 days.

[0037] Figure 2 SEM images of the nano-CSH nucleation early strength agents prepared in Example 3 and Comparative Examples 1-2;

[0038] Figure 3 The particle size distribution of the nano-CSH nucleation early strength agents prepared in Example 3 and Comparative Examples 1-2 is shown. Detailed Implementation

[0039] The technical solution of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0040] This invention provides a method for preparing a high-performance nano-hydrated calcium silicate early strength agent, comprising the following steps:

[0041] S1. Dissolve the calcium source, silicon source, aluminum source and magnesium source in water respectively to obtain aqueous solutions of calcium source, silicon source, aluminum source and magnesium source;

[0042] S2. Dissolve polyol amine and polyether monomer in water, add catalyst and prepolymerize for 2-4 hours under stirring, then add N-isopropylacrylamide and initiator, react for 3-5 hours, and obtain polyol amine-thermosensitive polyether copolymer after centrifugation and drying.

[0043] S3. Dissolve the polyol amine-thermosensitive polyether copolymer obtained in step S2 with sodium gluconate and polycarboxylate superplasticizer in water, and mix thoroughly to obtain an aqueous solution of composite modifier;

[0044] S4. Simultaneously add the aqueous solutions of calcium source, silicon source, aluminum source, and magnesium source to the aqueous solution of the composite modifier, adjust the pH to 11.5~12.8, stir and react at 20~50℃ for 3~8h, and after the reaction is completed, add the defoamer and corrosion inhibitor to obtain the high-performance nano-hydrated calcium silicate early strength agent.

[0045] In step S1, the molar ratio of calcium to silicon is (0.5~2):1, the molar ratio of aluminum to silicon is (0.02~0.45):1, and the molar ratio of magnesium to silicon is (0.02~0.45):1.

[0046] The calcium source includes at least one of calcium nitrate tetrahydrate, calcium chloride dihydrate, calcium carbonate, calcium sulfate, calcium phosphate, calcium formate, calcium fluoride, calcium oxide, calcium citrate, calcium hydrogen phosphate, and calcium bicarbonate; the silicon source includes at least one of sodium silicate, potassium silicate, lithium silicate, nano silica powder, tetraethyl orthosilicate, and tetramethyl silicate; the aluminum source includes at least one of aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum sulfate octadecahydrate, sodium aluminate, potassium aluminate, and lithium aluminate; and the magnesium source includes at least one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, magnesium carbonate, and magnesium oxide.

[0047] In step S2, the mass ratio of the polyol amine, polyether monomer, and N-isopropylacrylamide is (3~8):1:(2~6);

[0048] The polyol amines include at least one of triethanolamine, diethanolamine, N-methyldiethanolamine, triisopropanolamine, and diethanolmonoisopropanolamine.

[0049] The polyether monomer includes at least one of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer.

[0050] The catalyst is sodium hydride or potassium naphthalene, and the initiator includes persulfate initiators;

[0051] In step S3, the effective concentration of the polyol amine-thermosensitive polyether copolymer in the aqueous solution of the composite modifier is 1wt%~10wt%, the effective concentration of sodium gluconate is 0.05wt%~5wt%, and the effective concentration of the polycarboxylate superplasticizer is 0.5wt%~8wt%.

[0052] The mass ratio of the solid content of the polyol amine-thermosensitive polyether copolymer, sodium gluconate and polycarboxylate superplasticizer is (1~5):1:(1~4);

[0053] In the high-performance nano-hydrated calcium silicate early strength agent of the present invention, the molar concentration of the calcium source is 0.1~0.5mol / L, and the concentration of the polyol amine-thermosensitive polyether copolymer is 0.5wt%~7wt%.

[0054] The solid content of polycarboxylate superplasticizer is 30%~50%. For illustrative purposes only, the solid content of polycarboxylate superplasticizer used in the following examples and comparative examples is 40%.

[0055] Example 1

[0056] This embodiment provides a method for preparing a high-performance nano-hydrated calcium silicate early strength agent, including the following steps:

[0057] S1. Preparation of reaction precursor solutions: Calcium, silicon, aluminum, and magnesium sources were prepared according to the molar ratio of Ca:Si:Al:Mg = 1:1:0.08:0.06, respectively; 30 mL of 2 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution, 30 mL of 0.16 mol / L Al(NO3)3•9H2O solution, and 30 mL of 0.12 mol / L Mg(NO3)2•6H2O solution were prepared sequentially to obtain the respective reaction precursor solutions;

[0058] S2. Weigh 3g of triethanolamine and 1g of polyethylene oxide and dissolve them in 10g of deionized water. Add 0.01g of sodium hydride and stir for 2h for prepolymerization. Then add 2g of N-isopropylacrylamide and 0.05g of potassium persulfate and continue stirring for 3h. After the reaction is complete, remove unreacted monomers and oligomers by vacuum distillation. Centrifuge the product at 5000 r / min for 15 min. Freeze-dry the obtained solid part (-50℃, 48h) to obtain a white fluffy powder, which is a polyol amine-thermosensitive polyether copolymer.

[0059] S3. Weigh 20g of polycarboxylate superplasticizer, 9g of polyol amine-thermosensitive polyether copolymer and 3g of sodium gluconate and dissolve them in 160g of deionized water. Stir with a magnetic stirrer for 10 minutes until completely dissolved to obtain an aqueous solution of composite modifier.

[0060] S4. Simultaneously add the calcium source aqueous solution, silicon source aqueous solution, aluminum source aqueous solution, and magnesium source aqueous solution from step S1 to the composite modifier aqueous solution at a dropping rate of 10 mL / h. During the dropping, add NaOH to adjust the pH value to 12±0.2. At the same time, use a high-speed shear emulsifier to perform high-speed shear stirring of the reaction solution at a speed of 8000 r / min. After all the precursor solution has been dropped into the reaction vessel, reduce the speed to 5000 r / min until the preparation is completed. Near the end of the reaction, add 0.75 g of organosilicon defoamer and 0.45 g of benzotriazole corrosion inhibitor, and continue stirring for 10 min until completely and uniformly dissolved. Since the reaction vessel is in a closed state and the temperature rises continuously during the stirring process, reaching up to 50℃, a two-stage cooling process is adopted after the reaction: first, cool down to 30℃ at 0.5-1℃ / min, and then cool down to room temperature at 2-3℃ / min to obtain the high-performance nano-hydrated calcium silicate early strength agent.

[0061] Example 2

[0062] The preparation method of the high-performance nano-hydrated calcium silicate early strength agent in this embodiment is basically the same as that in Example 1, except that step S1 is as follows: calcium source, silicon source, aluminum source and magnesium source are prepared according to the molar ratio of Ca:Si:Al:Mg=1:1:0.06:0.08 respectively; 30 mL of 2 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution, 30 mL of 0.12 mol / L Al(NO3)3•9H2O solution and 30 mL of 0.16 mol / L Mg(NO3)2•6H2O solution are prepared in sequence to obtain each reaction precursor solution.

[0063] Example 3

[0064] The preparation method of the high-performance nano-hydrated calcium silicate early strength agent in this embodiment is basically the same as that in Example 1, except that step S1 is as follows: calcium source, silicon source, aluminum source and magnesium source are prepared according to the molar ratio of Ca:Si:Al:Mg=1.2:1:0.08:0.06 respectively; 30 mL of 2.4 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution, 30 mL of 0.16 mol / L Al(NO3)3•9H2O solution and 30 mL of 0.12 mol / L Mg(NO3)2•6H2O solution are prepared in sequence to obtain each reaction precursor solution.

[0065] Example 4

[0066] The preparation method of the high-performance nano-hydrated calcium silicate early strength agent in this embodiment is basically the same as that in Example 1, except that step S1 is as follows: calcium source, silicon source, aluminum source and magnesium source are prepared according to the molar ratio of Ca:Si:Al:Mg=1.2:1:0.06:0.08 respectively; 30 mL of 2.4 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution, 30 mL of 0.12 mol / L Al(NO3)3•9H2O solution and 30 mL of 0.16 mol / L Mg(NO3)2•6H2O solution are prepared in sequence to obtain each reaction precursor solution.

[0067] Example 5

[0068] This embodiment provides a method for preparing a high-performance nano-hydrated calcium silicate early strength agent, including the following steps:

[0069] S1. Preparation of reaction precursor solutions: Calcium, silicon, aluminum, and magnesium sources were prepared according to the molar ratio of Ca:Si:Al:Mg = 1:1:0.02:0.3, respectively; 30 mL of 2 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution, 30 mL of 0.04 mol / L Al(NO3)3•9H2O solution, and 30 mL of 0.6 mol / L Mg(NO3)2•6H2O solution were prepared sequentially to obtain the respective reaction precursor solutions;

[0070] S2. Weigh 8g of triethanolamine and 1g of polyethylene oxide and dissolve them in 20g of deionized water. Add 0.03g of potassium naphthalene and stir for 4h for prepolymerization. Then add 6g of N-isopropylacrylamide and 0.08g of potassium persulfate and continue stirring for 5h. After the reaction is complete, remove unreacted monomers and oligomers by vacuum distillation. Centrifuge the product at 5000 r / min for 15 min. Freeze-dry the obtained solid part (-50℃, 48h) to obtain a white fluffy powder, which is a polyol amine-thermosensitive polyether copolymer.

[0071] S3. Weigh 20g of polycarboxylate superplasticizer, 8g of polyol amine-thermosensitive polyether copolymer and 8g of sodium gluconate and dissolve them in 160g of deionized water. Stir with a magnetic stirrer for 10 minutes until completely dissolved to obtain an aqueous solution of composite modifier.

[0072] S4. Same as in Example 1, and will not be repeated here.

[0073] Comparative Example 1

[0074] The preparation method of the nano-hydrated calcium silicate early strength agent in this comparative example is basically the same as that in Example 3, except that step S1 is as follows: calcium source, silicon source, aluminum source and magnesium source are prepared according to the molar ratio of Ca:Si:Al=1.2:1:0.14; 30 mL of 2.4 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution and 30 mL of 0.28 mol / L Al(NO3)3•9H2O solution are prepared in sequence to obtain the precursor solutions for each reaction;

[0075] Compared to Example 3, this comparative example did not contain Mg. 2+ .

[0076] Comparative Example 2

[0077] The preparation method of the nano-hydrated calcium silicate early strength agent in this comparative example is basically the same as that in Example 3, except that step S1 is as follows: calcium source, silicon source, aluminum source and magnesium source are prepared according to the molar ratio of Ca:Si:Mg=1.2:1:0.14; 30 mL of 2.4 mol / L Ca(NO3)2•4H2O solution, 30 mL of 2 mol / L Na2SiO3•9H2O solution and 30 mL of 0.28 mol / L Mg(NO3)2•6H2O solution are prepared in sequence to obtain the precursor solutions for each reaction;

[0078] Compared to Example 3, this comparative example did not incorporate Al. 3+ .

[0079] Comparative Example 3

[0080] The preparation method of the nano-hydrated calcium silicate early strength agent in this comparative example is basically the same as that in Example 3, except that the preparation of polyol amine-thermosensitive polyether copolymer is omitted and triethanolamine of the same mass is used instead of polyol amine-thermosensitive polyether copolymer.

[0081] Comparative Example 4

[0082] The preparation method of the nano-hydrated calcium silicate early strength agent in this comparative example is basically the same as that in Example 3, except that step S3 is as follows: Weigh 27.5g of polycarboxylate superplasticizer and 9g of polyol amine-thermosensitive polyether copolymer and dissolve them in 160g of deionized water. Stir with a magnetic stirrer for 10min until completely dissolved to obtain an aqueous solution of composite modifier.

[0083] Compared to Example 3, sodium gluconate is omitted from the composite modifier in this comparative example, thus increasing the mass of polycarboxylate superplasticizer.

[0084] The actual image of the nano-CSH nucleation early strength agent prepared in Example 3 after standing for 90 days is shown below. Figure 1 As shown in the figure, the nano-CSH nucleus early strength agent seed suspension prepared by the present invention is a milky white liquid. After standing for 90 days, no layering occurred, indicating high solution stability, which facilitates practical engineering applications and storage.

[0085] SEM images of the nano-CSH nucleation early strength agents prepared in Example 3 and Comparative Examples 1-2 are shown below. Figure 2 As shown in the figure, compared with Comparative Examples 1 and 2 (single-doped Al), 3+ or Mg 2+ In contrast, the CSH crystal nuclei in Example 3 of this invention form a foil-like fiber network structure. This foil-like structure has an extremely high specific surface area, and the abundant hydroxyl groups and active sites on the surface provide a large number of nucleation sites for the cement hydration reaction.

[0086] The particle size distribution of the nano-CSH nucleation early strength agents prepared in Example 3 and Comparative Examples 1-2 is shown in the figure. Figure 3 As shown in the figure, compared with Comparative Examples 1-2 (single-doped Al) 3+ or Mg 2+ Compared to the previous examples, the average particle size of the early-strength agent in the dual-aluminum-magnesium doping method of this invention remained at 131.4 nm, while the average particle sizes of Comparative Examples 1 and 2 reached 185.5 nm and 214.6 nm, respectively. The particle size of the nano-CSH nucleation early-strength agent is one of the important factors affecting its early-strength effect. Compared to Comparative Examples 1 and 2, Example 3 effectively refined the nucleus particle size. The relatively smaller particle size has a larger specific surface area, allowing it to exert a better nucleation effect when incorporated into cement-based materials, thus significantly improving workability. Furthermore, as the size of the nano-CSH seed crystals decreases, the solution is less prone to aggregation, resulting in greater overall stability.

[0087] Test example

[0088] The nano-CSH nucleation accelerators prepared in Examples 1-5 and Comparative Examples 1-4 were used to prepare mortars according to GB / T17671-2021 "Test Method for Strength of Cement Mortar (ISO Method)". The water-cement ratio was 0.4, the mortar-mortar ratio was 1:3, and the dosage of the nano-CSH nucleation accelerator was 1% of the cementitious material. A control group was used, with no accelerator added. Freshly mixed cement mortar was poured into 40mm×40mm×160mm molds. During the molding process, the mortar was thoroughly tamped to ensure homogeneity. The mortars were placed in a standard curing room and cured at 10℃ and 35℃ for the specified curing ages. 20 minutes before the specified curing age, the mortars were demolded for strength testing. The cement used was P•O 42.5 ordinary Portland cement produced by Liaoning Shanshui Gongyuan Cement Co., Ltd. The test results are shown in Table 1.

[0089] Table 1 Compressive strength results of mortar test blocks in each group

[0090]

[0091] As can be seen from the data in Table 1, compared with the blank group and the comparative example, the nano-CSH nucleus early strength agent prepared by the present invention can significantly improve the early strength of mortar.

[0092] By comparing Example 3 and Comparative Examples 1-2, it can be found that, compared with Al-doped Al, 3+ or Mg 2+ In contrast, this invention utilizes aluminum-magnesium dual-ion doping, which can significantly improve the compressive strength of the mortar. This is mainly because aluminum-magnesium dual-ion doping not only accelerates the nucleation process but also significantly improves the size distribution (refining the nucleus particle size) and morphological characteristics (when doped alone, the nucleus morphology is spherical; when doped with both, the nucleus morphology becomes foil-like), thereby significantly improving the compressive strength of the mortar.

[0093] Comparing Example 3 and Comparative Example 3, the strength of the specimens at 10℃ increased by 45.6% and 56.3% after 16 hours and 1 day, respectively. This indicates that the temperature-sensitive segments of the copolymer can accelerate hydration through hydrogen bonding networks at low temperatures, which is beneficial to the formation of early structure in cement-based materials and promotes strength development. At 35℃, the strength of the specimens at 16 hours and 1 day increased by 30.1% and 32.3%, respectively, maintaining excellent early strength performance at higher temperatures compared to traditional alkanolamines. Comparing Example 3 and Comparative Example 4, the strength of the specimens at 10℃ increased by 67.9% and 58.1% after 16 hours and 1 day, respectively, while at 35℃, the strength increased by 39.9% and 41.1%, respectively. This demonstrates that the addition of sodium gluconate-modified nano-CSH nuclei improved nucleus dispersion, prevented early agglomeration, increased the number of effective nucleation sites, generated more hydration products, increased the density of the slurry, and further enhanced early strength at various temperatures.

[0094] The stability of each group of early-strength agent solutions and the rheological properties of cement paste are shown in Table 2. The water-cement ratio of the cement paste was 0.4, and the dosage of early-strength agent was 1% of the cement.

[0095] Table 2. Stability and rheological properties of each group of solutions.

[0096]

[0097] As can be seen from the data in Table 2, compared with the blank group and the comparative example, the nano-CSH nucleus early strength agent prepared in the embodiments of the present invention did not produce any precipitation after 90 days, indicating that the nano-CSH nucleus early strength agent prepared in the present invention has excellent storage stability.

[0098] By comparing Example 3 and Comparative Example 3, it can be seen that the polyol amine-thermosensitive polyether copolymer in the composite modifier can significantly enhance the interfacial bonding force and structural stability of CSH crystal nuclei, thereby improving the stability of the solution.

[0099] By comparing Example 3 and Comparative Example 4, it can be seen that sodium gluconate can significantly improve the dispersibility and stability of the early strength agent solution. This is mainly because calcium ions will complex with sodium gluconate in the solution, which reduces the supersaturation of CSH nucleation during the synthesis of CSH seed crystals, enhances the steric hindrance effect of polycarboxylic acid, and improves the overall dispersibility and stability of the solution.

[0100] Regarding rheological properties, yield stress represents the shear stress required for stable flow of cement paste. Compared to the control group and the comparative example, the yield stress of Examples 1-4 jumped to 128-135 Pa, indicating that the nano-CSH nuclei filled the gaps between cement particles in a highly dispersed state, significantly increasing the total specific surface area of ​​the system and shortening the average spacing between particles. Simultaneously, the reversible physical network constructed from polyol amine-thermosensitive polyether copolymer on the nuclei surface forms multiple hydrogen bonds and electrostatic crosslinking points with the cement particles, thereby strengthening the three-dimensional network structure of the paste. These synergistic effects result in a monotonically increasing dynamic yield stress and plastic viscosity of the cement paste with increasing nuclei content, while maintaining good pumpability and thixotropic recovery.

[0101] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-performance nano-hydrated calcium silicate early strength agent, characterized in that, Includes the following steps: S1. Dissolve the calcium source, silicon source, aluminum source and magnesium source in water respectively to obtain aqueous solutions of calcium source, silicon source, aluminum source and magnesium source; S2. Dissolve polyol amine and polyether monomer in water, add catalyst and prepolymerize for 2-4 hours under stirring, then add N-isopropylacrylamide and initiator, react for 3-5 hours, and obtain polyol amine-thermosensitive polyether copolymer after centrifugation and drying. S3. Dissolve the polyol amine-thermosensitive polyether copolymer obtained in step S2 with sodium gluconate and polycarboxylate superplasticizer in water, and mix thoroughly to obtain an aqueous solution of composite modifier; S4. Simultaneously add the aqueous solutions of calcium source, silicon source, aluminum source, and magnesium source to the aqueous solution of the composite modifier, adjust the pH to 11.5~12.8, stir and react at 20~50℃ for 3~8h, and after the reaction is completed, add the defoamer and corrosion inhibitor to obtain the high-performance nano-hydrated calcium silicate early strength agent.

2. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, The molar ratio of calcium to silicon is (0.5~2):1, the molar ratio of aluminum to silicon is (0.02~0.45):1, and the molar ratio of magnesium to silicon is (0.02~0.45):

1.

3. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, In step S2, the mass ratio of the polyol amine, polyether monomer, and N-isopropylacrylamide is (3~8):1:(2~6); And / or, the catalyst is sodium hydride or potassium naphthalene, and the initiator includes persulfate initiators.

4. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, In the aqueous solution of the composite modifier, the concentration of the polyol amine-thermosensitive polyether copolymer is 1wt%~10wt%, the concentration of sodium gluconate is 0.05wt%~5wt%, and the effective concentration of the polycarboxylate superplasticizer is 0.5wt%~8wt%.

5. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, The mass ratio of solid content in the polyol amine-thermosensitive polyether copolymer, sodium gluconate and polycarboxylate superplasticizer is (1~5):1:(1~4).

6. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, The calcium source includes at least one of calcium nitrate tetrahydrate, calcium chloride dihydrate, calcium carbonate, calcium sulfate, calcium phosphate, calcium formate, calcium fluoride, calcium oxide, calcium citrate, calcium hydrogen phosphate, and calcium bicarbonate. And / or, the silicon source includes at least one of sodium silicate, potassium silicate, lithium silicate, nano-silica powder, tetraethyl orthosilicate, and tetramethyl silicate.

7. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, The aluminum source includes at least one of aluminum nitrate nonahydrate, aluminum chloride hexahydrate, aluminum sulfate octadecahydrate, sodium aluminate, potassium aluminate, and lithium aluminate. And / or, the magnesium source includes at least one of magnesium nitrate hexahydrate, magnesium chloride hexahydrate, magnesium sulfate heptahydrate, magnesium carbonate, and magnesium oxide.

8. The preparation method of a high-performance nano-hydrated calcium silicate early strength agent according to claim 1, characterized in that, The polyol amine includes at least one of triethanolamine, diethanolamine, N-methyldiethanolamine, triisopropanolamine, and diethanolmonoisopropanolamine; And / or, the polyether monomer includes at least one of polyethylene oxide, polypropylene oxide, and ethylene oxide-propylene oxide copolymer.

9. The high-performance nano-hydrated calcium silicate early strength agent prepared by the preparation method according to any one of claims 1 to 8.

10. The application of the high-performance nano-hydrated calcium silicate early-strength agent prepared by the preparation method according to any one of claims 1 to 8 in concrete, characterized in that, The early strength agent is added at a rate of 0.8% to 2.5% of the mass of the cementitious material.

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