A quick-setting agent for spraying ultra-high performance concrete in high altitude areas and its preparation

Abstract

The present invention relates to the technical field of concrete accelerating agents, and specifically discloses an accelerating agent for sprayable ultra-high performance concrete in high altitude areas. The raw materials thereof by mass parts include: 30-60 parts of aluminum sulfate, 1-5 parts of magnesium sulfate, 1-2 parts of 3-hydroxy-3-carboxypentanedioic acid, 1-3 parts of N,N-diethylethanolamine, 1-2 parts of disodium ethylenediaminetetraacetate, 1-3 parts of oxidized chitosan, 5-10 parts of microcrystalline cellulose, 1-2 parts of terminal amino polyamide amine, 0.1-1 part of dibutyl phthalate, and 0.1-1 part of hydroxyethyl cellulose. The present invention also discloses a preparation method of the above accelerating agent for sprayable ultra-high performance concrete in high altitude areas. The present invention has a short setting time and high strength. The 1-day strength can reach more than 14 MPa, and the 28-day compressive strength ratio can be as high as 119%; it has little irritation to the human body, is safe and reliable, optimizes the construction environment, and can still play an accelerating role when the environmental temperature is relatively low (the lowest is 0°C).

Description

Technical Field

[0001] The present invention relates to the technical field of concrete accelerating agents, and particularly relates to an accelerating agent for sprayable ultra-high performance concrete in high altitude areas and a preparation method thereof. Background Art

[0002] A concrete accelerating agent refers to an admixture that can cause concrete to quickly set and harden. The mechanism of its early strength is to turn the gypsum in cement into sodium sulfate, losing the retarding effect, thereby promoting the rapid hydration of C3A (tricalcium aluminate) and precipitating its hydration product crystals in the solution, resulting in the rapid solidification of the cement paste.

[0003] At present, the development speed of liquid accelerating agents is rapid. The commonly used accelerating agents for shotcrete generally contain a large amount of alkaline substances. Although they can meet the requirements of rapid hardening, they have a greater impact on the later strength of shotcrete. At the same time, a large amount of alkaline substances increase the later alkali-aggregate reaction of concrete, damaging the durability of concrete.

[0004] The existing alkali-free liquid accelerating agents have a rapid development speed, but there are generally some problems with the accelerating effect of liquid accelerating agents at lower temperatures. For example, the setting time is relatively long, the strength development of concrete is slow, and the rebound of shotcrete is relatively large. Especially in high altitude mountainous areas, the temperature is relatively low, and the existing liquid accelerating agents have poor use effects. They will solidify and crystallize at relatively low temperatures, resulting in poor accelerating effects on concrete, the setting time not meeting the requirements, low production efficiency, and increased overall costs. Summary of the Invention

[0005] The purpose of the present invention is to solve the disadvantages existing in the prior art, and to propose an accelerating agent for sprayable ultra-high performance concrete in high altitude areas and a preparation method thereof.

[0006] An accelerating agent for sprayable ultra-high performance concrete in high altitude areas, the raw materials of which include by mass: 30-60 parts of aluminum sulfate, 1-5 parts of magnesium sulfate, 1-2 parts of 3-hydroxy-3-carboxypentanedioic acid, 1-3 parts of N,N-diethylethanolamine, 1-2 parts of disodium ethylenediaminetetraacetate, 1-3 parts of oxidized chitosan, 5-10 parts of microcrystalline cellulose, 1-2 parts of terminal amino polyamidoamine, 0.1-1 part of dibutyl phthalate, and 0.1-1 part of hydroxyethyl cellulose.

[0007] Preferably, the viscosity-average molecular weight of the oxidized chitosan is 100,000-120,000, and the degree of deacetylation is 92.4-95.3%.

[0008] Preferably, the C6-carboxyl group content of the oxidized chitosan is 35-40.2 wt%.

[0009] Preferably, the oxidized chitosan is 6-carboxy chitosan.

[0010] Preferably, the oxidized chitosan is obtained by selectively oxidizing the C-6 primary hydroxyl group of chitosan using NO2 or a laccase / 2,2,6,6-tetramethylpiperidine-1-oxyl radical system.

[0011] See:

[0012] [1] Yang Yuedong, Yu Jiugao, Zhou Yongguo, et al. Preparation and blood compatibility study of 6-carboxy chitosan [J]. Chinese Journal of Biomedical Engineering, 2007, 26(4): 5. DOI: 10.3969 / j.issn.0258-8021.2007.04.024.

[0013] [2] Ji Lei, Liu Tianhong, Wang Ying, et al. Preparation and antibacterial properties of silver-loaded oxidized chitosan [J]. Journal of Agricultural Science and Technology in China, 2024(003): 026.

[0014] Preferably, the generation number of the amino-terminated polyamidoamine is 4.0 - 6.0.

[0015] The preparation method of the superplasticizer for shotcrete of ultra-high performance concrete in high altitude areas as described above includes the following steps:

[0016] S1. Add oxidized chitosan to an aqueous acetic acid solution and stir evenly. Add microcrystalline cellulose, stir at 60 - 80 °C for 1 - 2 h, cool to 40 - 45 °C, add amino-terminated polyamidoamine and stir for 10 - 20 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0017] S2. Add aluminum sulfate and activated cellulose to water and stir evenly. Then add magnesium sulfate, 3-hydroxy-3-carboxypentanedioic acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence, and stir at 50 - 70 °C until the system becomes clear to obtain a prefabricated material;

[0018] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material and stir evenly, then cool to room temperature.

[0019] Preferably, in S1, the concentration of the aqueous acetic acid solution is 0.1 - 1 mol / L.

[0020] Preferably, in S2, during the process of stirring at 50 - 70 °C until the system becomes clear, the stirring speed is 100 - 400 r / min.

[0021] Beneficial effects:

[0022] 1. The present invention combines oxidized chitosan with microcrystalline cellulose to enhance the chemical activity of microcrystalline cellulose, which can further combine with the active groups on the molecular chain of terminal amino polyamidoamine; while the stable branched structure of terminal amino polyamidoamine is compounded with aluminum sulfate, and stable macromolecular groups are formed through coordination, which not only improves the stability of the accelerator, but also increases the addition amount of aluminum sulfate, enhances the early strength performance of concrete, and ensures the stability of the accelerator system.

[0023] 2. The present invention further adds dibutyl phthalate, which has strong gelation ability. Cooperating with hydroxyethyl cellulose, it can not only greatly improve the adaptability of the accelerator, but also rapidly reduce the freezing point of the accelerator, effectively inhibiting the recrystallization of ice, which can not only maintain the continuous progress of the hydration reaction of concrete, but also greatly improve the durability of concrete.

[0024] 3. The present invention uses activated cellulose in combination with hydroxyethyl cellulose. The two have strong affinity and cooperate with each other to form macromolecular groups with high stability. The solution has good stability, the concrete spraying effect is good, the spraying slurry has good cohesiveness, the accelerating effect is good, and it has excellent early and late strength.

[0025] The setting time of the present invention is short. The initial setting can be controlled at about 2 min 39 s, and the final setting can be controlled at about 6 min 26 s. Moreover, it has high strength. The 1-day strength can reach more than 14 MPa, the 28-day compressive strength ratio can be as high as 119%, and the 90-day compressive strength retention rate reaches 117%; it has little irritation to the human body, is safe and reliable, optimizes the construction environment, and can still play an accelerating role at a relatively low ambient temperature (the lowest is 0 °C). Description of the Drawings

[0026] Figure 1 It is a comparison chart of the neat paste setting time of the accelerators obtained in Example 5 and Comparative Examples 1-2.

[0027] Figure 2 It is a comparison chart of the 1-day compressive strength and 28-day compressive strength ratio of the accelerators obtained in Example 5 and Comparative Examples 1-2.

[0028] Figure 3 It is a comparison chart of the 90-day compressive strength retention rate and the stable period of the accelerators obtained in Example 5 and Comparative Examples 1-2.

[0029] Figure 4 It is a state photo of the accelerator obtained in Example 5 after low-temperature stability test.

[0030] Figure 5 It is a state photo of the accelerator obtained in Comparative Example 2 after low-temperature stability test.

[0031] Figure 6 It is a spraying effect photo in the tunnel using the accelerator obtained in Example 5.

[0032] Figure 7 The photo shows the spraying effect of the quick-setting agent obtained in Example 5 on the slope.

[0033] Figure 8 The photo shows the spraying effect of a commercially available quick-setting agent on the slope. Detailed implementation manners

[0034] The present invention will be further explained below in conjunction with specific embodiments.

[0035] The applicant prepared 6-carboxyl chitosan according to the literature [2] (Ji Lei, Liu Tianhong, Wang Ying, etc. Preparation and antibacterial properties of silver-loaded chitosan oxide [J]. Journal of Agricultural Science and Technology in China, 2024(003):026.).

[0036] The viscosity-average molecular weight of the 6-carboxyl chitosan used below is 110,000, the degree of deacetylation is 93.3%, and the content of C6 carboxyl group is 36.75 wt%.

[0037] Example 1

[0038] A quick-setting agent for sprayable ultra-high performance concrete in high altitude areas, the raw materials of which include: 30 kg of aluminum sulfate, 1 kg of magnesium sulfate, 1 kg of 3-hydroxy-3-carboxyl glutaric acid, 1 kg of N,N-diethyl ethanolamine, 1 kg of disodium ethylenediaminetetraacetate, 1 kg of 6-carboxyl chitosan, 5 kg of microcrystalline cellulose, 1 kg of 4.0-generation terminal amino polyamidoamine, 0.1 kg of dibutyl phthalate, and 0.1 kg of hydroxyethyl cellulose.

[0039] The preparation method of the above quick-setting agent for sprayable ultra-high performance concrete in high altitude areas includes the following steps:

[0040] S1. Add 6-carboxyl chitosan to 20 kg of acetic acid aqueous solution with a concentration of 0.1 mol / L, stir evenly, add microcrystalline cellulose, stir at a temperature of 60 °C for 1 h, cool down to 40 °C, add terminal amino polyamidoamine and stir for 10 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0041] S2. Add aluminum sulfate and activated cellulose to 40 kg of water, stir evenly, and then add magnesium sulfate, 3-hydroxy-3-carboxyl glutaric acid, N,N-diethyl ethanolamine, and disodium ethylenediaminetetraacetate in sequence, stir at a temperature of 50 °C until the system becomes clear, and the stirring speed is 100 r / min to obtain a prefabricated material;

[0042] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0043] Example 2

[0044] A quick-setting agent for shotcrete ultra-high performance concrete in high altitude areas, the raw materials of which include: 60 kg of aluminum sulfate, 5 kg of magnesium sulfate, 2 kg of 3-hydroxy-3-carboxypentanedioic acid, 3 kg of N,N-diethylethanolamine, 2 kg of disodium ethylenediaminetetraacetate, 3 kg of 6-carboxychitosan, 10 kg of microcrystalline cellulose, 2 kg of 6.0-generation amino-terminated polyamidoamine, 1 kg of dibutyl phthalate, and 1 kg of hydroxyethyl cellulose.

[0045] The preparation method of the above quick-setting agent for shotcrete ultra-high performance concrete in high altitude areas includes the following steps:

[0046] S1. Add 6-carboxychitosan to 30 kg of acetic acid aqueous solution with a concentration of 1 mol / L, stir evenly, add microcrystalline cellulose, stir at 80 °C for 2 h, cool down to 45 °C, add amino-terminated polyamidoamine and stir for 20 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0047] S2. Add aluminum sulfate and activated cellulose to 50 kg of water, stir evenly, and then add magnesium sulfate, 3-hydroxy-3-carboxypentanedioic acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence. Stir at 70 °C until the system becomes clear, and the stirring speed is 400 r / min to obtain a prefabricated material;

[0048] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0049] Example 3

[0050] A quick-setting agent for shotcrete ultra-high performance concrete in high altitude areas, the raw materials of which include: 40 kg of aluminum sulfate, 4 kg of magnesium sulfate, 1.3 kg of 3-hydroxy-3-carboxypentanedioic acid, 2.5 kg of N,N-diethylethanolamine, 1.3 kg of disodium ethylenediaminetetraacetate, 2.5 kg of 6-carboxychitosan, 7 kg of microcrystalline cellulose, 1.8 kg of 5.5-generation amino-terminated polyamidoamine, 0.3 kg of dibutyl phthalate, and 0.8 kg of hydroxyethyl cellulose.

[0051] The preparation method of the above quick-setting agent for shotcrete ultra-high performance concrete in high altitude areas includes the following steps:

[0052] S1. Add 6-carboxychitosan to 22 kg of acetic acid aqueous solution with a concentration of 0.7 mol / L, stir evenly, add microcrystalline cellulose, stir at 65 °C for 100 min, cool down to 41 °C, add amino-terminated polyamidoamine and stir for 18 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0053] S2. Add aluminum sulfate and activated cellulose to 42 kg of water, stir evenly, and then add magnesium sulfate, 3-hydroxy-3-carboxypentanedioic acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence. Stir at 65 °C until the system becomes clear, with a stirring speed of 200 r / min to obtain a prefabricated material;

[0054] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0055] Example 4

[0056] A quick-setting agent for sprayable ultra-high performance concrete in high altitude areas, the raw materials of which include: 50 kg of aluminum sulfate, 2 kg of magnesium sulfate, 1.7 kg of 3-hydroxy-3-carboxypentanedioic acid, 1.5 kg of N,N-diethylethanolamine, 1.7 kg of disodium ethylenediaminetetraacetate, 1.5 kg of 6-carboxy chitosan, 9 kg of microcrystalline cellulose, 1.2 kg of 4.5-generation amino-terminated polyamidoamine, 0.7 kg of dibutyl phthalate, and 0.2 kg of hydroxyethyl cellulose.

[0057] The preparation method of the above-mentioned quick-setting agent for sprayable ultra-high performance concrete in high altitude areas includes the following steps:

[0058] S1. Add 6-carboxy chitosan to 28 kg of acetic acid aqueous solution with a concentration of 0.3 mol / L, stir evenly, add microcrystalline cellulose, stir at 75 °C for 80 min, cool down to 43 °C, add amino-terminated polyamidoamine and stir for 12 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0059] S2. Add aluminum sulfate and activated cellulose to 48 kg of water, stir evenly, and then add magnesium sulfate, 3-hydroxy-3-carboxypentanedioic acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence. Stir at 55 °C until the system becomes clear, with a stirring speed of 300 r / min to obtain a prefabricated material;

[0060] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0061] Example 5

[0062] A quick-setting agent for sprayable ultra-high performance concrete in high altitude areas, the raw materials of which include: 45 kg of aluminum sulfate, 3 kg of magnesium sulfate, 1.5 kg of 3-hydroxy-3-carboxypentanedioic acid, 2 kg of N,N-diethylethanolamine, 1.5 kg of disodium ethylenediaminetetraacetate, 2 kg of 6-carboxy chitosan, 8 kg of microcrystalline cellulose, 1.5 kg of 5.0-generation amino-terminated polyamidoamine, 0.5 kg of dibutyl phthalate, and 0.5 kg of hydroxyethyl cellulose.

[0063] The preparation method of the quick-setting agent for sprayable ultra-high performance concrete in the above-mentioned high altitude areas comprises the following steps:

[0064] S1. Add 6-carboxyl chitosan to 25 kg of acetic acid aqueous solution with a concentration of 0.5 mol / L, stir evenly, add microcrystalline cellulose, stir at 70 °C for 90 min, cool down to 42 °C, add terminal amino polyamide amine, stir for 15 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0065] S2. Add aluminum sulfate and activated cellulose to 45 kg of water, stir evenly, and successively add magnesium sulfate, 3-hydroxy-3-carboxyl glutaric acid, N,N-diethyl ethanolamine, and disodium ethylenediaminetetraacetate, stir at 60 °C until the system becomes clear, and the stirring speed is 250 r / min to obtain a prefabricated material;

[0066] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0067] Comparative Example 1

[0068] A quick-setting agent, whose raw materials include: 45 kg of aluminum sulfate, 3 kg of magnesium sulfate, 1.5 kg of 3-hydroxy-3-carboxyl glutaric acid, 2 kg of N,N-diethyl ethanolamine, 1.5 kg of disodium ethylenediaminetetraacetate, 2 kg of 6-carboxyl chitosan, 8 kg of microcrystalline cellulose, 0.5 kg of dibutyl phthalate, and 0.5 kg of hydroxyethyl cellulose.

[0069] The preparation method of the above-mentioned quick-setting agent comprises the following steps:

[0070] S1. Add 6-carboxyl chitosan to 25 kg of acetic acid aqueous solution with a concentration of 0.5 mol / L, stir evenly, add microcrystalline cellulose, stir at 70 °C for 90 min, cool down, filter, wash, and vacuum dry to obtain activated cellulose;

[0071] S2. Add aluminum sulfate and activated cellulose to 45 kg of water, stir evenly, and successively add magnesium sulfate, 3-hydroxy-3-carboxyl glutaric acid, N,N-diethyl ethanolamine, and disodium ethylenediaminetetraacetate, stir at 60 °C until the system becomes clear, and the stirring speed is 250 r / min to obtain a prefabricated material;

[0072] S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

[0073] Comparative Example 2

[0074] A quick-setting agent, the raw materials of which include: 45 kg of aluminum sulfate, 3 kg of magnesium sulfate, 1.5 kg of 3-hydroxy-3-carboxypentanedioic acid, 2 kg of N,N-diethylethanolamine, 1.5 kg of disodium ethylenediaminetetraacetate, 2 kg of 6-carboxychitosan, 8 kg of microcrystalline cellulose, 1.5 kg of 5.0-generation amino-terminated polyamidoamine, and 0.5 kg of dibutyl phthalate.

[0075] The preparation method of the above quick-setting agent includes the following steps:

[0076] S1. Add 6-carboxychitosan to 25 kg of acetic acid aqueous solution with a concentration of 0.5 mol / L, stir evenly, add microcrystalline cellulose, stir at 70 °C for 90 min, cool down to 42 °C, add amino-terminated polyamidoamine and stir for 15 min, filter, wash, and vacuum dry to obtain activated cellulose;

[0077] S2. Add aluminum sulfate and activated cellulose to 45 kg of water, stir evenly, and successively add magnesium sulfate, 3-hydroxy-3-carboxypentanedioic acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate, stir at 60 °C until the system becomes clear, and the stirring speed is 250 r / min to obtain a prefabricated material;

[0078] S3. Add dibutyl phthalate to the prefabricated material, stir evenly, and cool to room temperature.

[0079] Refer to GB / T 35159-2017 "Quick-setting Agent for Shotcrete" to detect the setting time of neat cement, mortar strength, and stability of the quick-setting agents obtained in Example 5 and Comparative Examples 1-2. Among them, the dosage of the quick-setting agent is 7% of the mass of cement, and the stability is observed every day according to the method in Appendix C until the volume of the bottom precipitate exceeds 5 mL, and the number of days is recorded.

[0080] As Figures 1-3 shown, the setting time of the neat cement of the quick-setting agent obtained in Example 5 is shorter than that of Comparative Examples 1-2 (P < 0.05), the mortar strength is better than that of Comparative Examples 1-2 (P < 0.05), and the stability is also far better than that of Comparative Examples 1-2 (P < 0.05).

[0081] Refer to GB / T 35159-2017 "Quick-setting Agent for Shotcrete" to detect the low-temperature stability of the quick-setting agents obtained in Example 5 and Comparative Example 2. The ambient temperature is maintained at 0 ± 1 °C, and the volume of the bottom precipitate is measured after 28 d. Among them, the state of the quick-setting agent obtained in Example 5 is as Figure 4 shown, while the state of the quick-setting agent obtained in Comparative Example 2 is as Figure 5 shown.

[0082] The applicant believes that: on the one hand, in the present invention, oxidized chitosan is combined with microcrystalline cellulose to enhance the chemical activity of microcrystalline cellulose, which can further combine with the active groups on the molecular chain of terminal amino polyamidoamine; and the stable branched structure of terminal amino polyamidoamine is compounded with aluminum sulfate to form stable macromolecular groups through coordination, which not only improves the stability of the accelerator, but also can increase the addition amount of aluminum sulfate, enhance the early strength performance of concrete while ensuring the stability of the accelerator system; on the other hand, in the present invention, dibutyl phthalate is further added, which has strong gelation ability and cooperates with hydroxyethyl cellulose, not only can greatly improve the adaptability of the accelerator, but also can quickly lower the freezing point of the accelerator, effectively inhibit the recrystallization of ice, which can not only maintain the continuous progress of the hydration reaction of concrete, but also greatly improve the durability of concrete; and the activated cellulose cooperates with hydroxyethyl cellulose, and the two have strong affinity and cooperate with each other to form macromolecular groups with high stability, with good solution stability, good concrete spraying effect, good cohesion of spraying slurry, good accelerating effect, and excellent early and late strength.

[0083] The accelerator obtained in Example 5 was added to shotcrete at a construction site in Xinjiang for actual operation, as Figure 6 and Figure 7 shown. While the shotcrete at this construction site was actually operated with the original accelerator as Figure 8 shown. Through Figure 7 and Figure 8 comparison, it can be found that when the accelerator obtained by the present invention is used for spraying, the dust is extremely small, which is better than the existing commercially available accelerators.

[0084] The above is only the preferred specific implementation mode of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention, according to the technical solution and inventive concept of the present invention, makes equivalent substitutions or changes, and should be covered by the protection scope of the present invention.

Claims

1. A quick-setting agent for ultra-high performance concrete that can be sprayed in high altitude areas, characterized in that: The raw materials include, by mass: 30-60 parts of aluminum sulfate, 1-5 parts of magnesium sulfate, 1-2 parts of 3-hydroxy-3-carboxyglutaric acid, 1-3 parts of N,N-diethylethanolamine, 1-2 parts of disodium ethylenediaminetetraacetate, 1-3 parts of oxidized chitosan, 5-10 parts of microcrystalline cellulose, 1-2 parts of amino-terminated polyamidoamine, 0.1-1 parts of dibutyl phthalate, and 0.1-1 parts of hydroxyethyl cellulose; Prepared by the following steps: S1. Add oxidized chitosan to acetic acid aqueous solution and stir evenly, add microcrystalline cellulose, stir at 60-80°C for 1-2h, cool to 40-45°C, add amino-terminated polyamidoamine and stir for 10-20min, filter, wash, and vacuum dry to obtain activated cellulose; S2, adding aluminum sulfate and activated cellulose to water and stirring evenly, adding magnesium sulfate, 3-hydroxy-3-carboxyglutaric acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence, stirring at 50-70° C. until the system becomes clear, to obtain a prefabricated material; S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

2. The quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 1, characterized in that: The viscosity-average molecular weight of oxidized chitosan is 100,000-120,000, and the degree of deacetylation is 92.4-95.3%.

3. The quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 1, characterized in that: The C6 carboxyl content of oxidized chitosan is 35-40.2wt%.

4. The quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 1, characterized in that: Oxidized chitosan is 6-carboxychitosan.

5. The quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 1, characterized in that: The oxidized chitosan is obtained by selectively oxidizing the C-6 primary hydroxyl group of chitosan using NO2 or laccase / 2,2,6,6-tetramethylpiperidin-1-oxyl free radical system.

6. The quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 1, characterized in that: The generation number of the amino-terminated polyamidoamine is 4.0-6.

0.

7. A method for preparing the quick-setting agent for ultra-high performance concrete sprayable in high altitude areas according to any one of claims 1 to 6, characterized in that: The steps include: S1. Add oxidized chitosan to acetic acid aqueous solution and stir evenly, add microcrystalline cellulose, stir at 60-80°C for 1-2h, cool to 40-45°C, add amino-terminated polyamidoamine and stir for 10-20min, filter, wash, and vacuum dry to obtain activated cellulose; S2, adding aluminum sulfate and activated cellulose to water and stirring evenly, adding magnesium sulfate, 3-hydroxy-3-carboxyglutaric acid, N,N-diethylethanolamine, and disodium ethylenediaminetetraacetate in sequence, stirring at 50-70° C. until the system becomes clear, to obtain a prefabricated material; S3. Add dibutyl phthalate and hydroxyethyl cellulose to the prefabricated material, stir evenly, and cool to room temperature.

8. The method for preparing an accelerated setting agent for sprayable ultra-high performance concrete in high altitude areas according to claim 7, characterized in that: In S1, the concentration of the acetic acid aqueous solution is 0.1-1 mol / L.

9. The method for preparing an accelerated setting agent for ultra-high performance concrete sprayable in high altitude areas according to claim 7, characterized in that: In S2, the system is stirred at 50-70°C until the system becomes clear, and the stirring speed is 100-400 r / min.

Images