A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent and preparation method thereof

Abstract

The invention belongs to the technical field of accelerators, and specifically relates to a low-corrosive non-toxic, sulfur-free, alkali-free accelerator and a preparation method thereof. The low-corrosive non-toxic, sulfur-free, alkali-free accelerator comprises the following raw materials by weight: 20-30 parts of nano-aluminum sol; 15-20 parts of silica sol; 8-10 parts of bentonite organic copolymer; 10-15 parts of aluminum salt; 6-10 parts of composite early strength agent; 10-15 parts of water; the alkali-free accelerator provided by the invention does not contain sulfate, is non-toxic, and has low corrosiveness, thereby ensuring the safety of storage and use; by adding bentonite organic copolymer, the stability of the alkali-free accelerator is improved; when applied to concrete, it can effectively shorten the setting time and improve the early strength and durability of concrete.

Description

Technical Field

[0001] The invention belongs to the technical field of accelerating setting agents, and in particular relates to a low-corrosive, non-toxic, sulfur-free and alkali-free accelerating setting agent and a preparation method thereof. Background Art

[0002] Shotcrete is a type of concrete that is formed by sending concrete mixture or premixed concrete into the spraying equipment through an air-filled pipe with the help of compressed air or other power, and then spraying it onto the sprayed surface at high speed and then quickly setting and hardening. It has the characteristics of simple and fast construction process, low cost, and high concrete density. It is widely used in surface support and structural reinforcement of large-scale projects such as tunnels, mines, and hydropower. Accelerator is an admixture that can make concrete set and harden quickly. It is an important admixture in the construction process of shotcrete. According to the alkali content in the accelerator (according to the equivalent Na 2 O content), can be divided into alkali accelerator and alkali-free accelerator. The alkali content in the alkali-free accelerator is less than 1%. Too high alkali content in the accelerator is prone to alkali-aggregate reaction, causing concrete cracking and affecting concrete durability. In order to improve the working performance of shotcrete, alkali-free accelerator is gradually replacing alkali accelerator.

[0003] A Chinese patent with application number CN202211209947.4 discloses a powdered alkali-free quick-setting agent and a preparation method and application thereof. The powdered alkali-free quick-setting agent is prepared from the following components by mass: 32-45 parts of phosphorus chemical by-products, 20-30 parts of concentrated sulfuric acid, 15-25 parts of aluminum hydroxide, 1-7 parts of trimagnesium phosphate, 1-7 parts of transparent powder, 0.1-1 parts of stabilizer and 2-15 parts of water; the powdered alkali-free quick-setting agent has excellent water solubility and can be compounded into a 50-60% liquid alkali-free quick-setting agent. Since phosphorus chemical by-products are used as raw materials, it is green, environmentally friendly and low-cost, but the content of concentrated sulfuric acid is high and it is highly corrosive, and there is a risk of corrosion during production and use.

[0004] The Chinese patent application number CN202311504422.8 discloses a high-performance powdered alkali-free quick-setting agent and a preparation method thereof, comprising the following raw materials in mass percentage: 45-55% aluminum sulfate, 1.5-2.5% inorganic salt, 0.5-1.0% stabilizer, 3-5% organic complexing agent, 2-4% inorganic nano component and balance water, wherein the inorganic nano component is nano CSH microcrystals. The high-performance powdered alkali-free quick-setting agent has stable properties and can be stored for a long time; its main component is aluminum sulfate, and a large amount of sulfate ions will induce the formation of secondary calcium sulfonate, forming a huge expansion stress inside the concrete, which will lead to cracking of the concrete and a decrease in mechanical properties.

[0005] The solubility of aluminum sulfate in aluminum sulfate-based alkali-free accelerators is limited. Fluoric acid or fluoride salts are usually added to enhance the aluminum phase concentration in the alkali-free accelerator. However, fluoride ions consume calcium ions to form calcium fluoride, and have a coating and inhibition effect on CSH gel through adsorption and intercalation, thereby significantly delaying the early hydration process of cement, resulting in low early strength of concrete. Fluoric acid or fluoride salts also have the problem of strong corrosiveness, especially fluoride comes into contact with the human body, which seriously endangers health. Therefore, it is urgent to develop a low-corrosive sulfur-free and alkali-free accelerator to meet market demand. Summary of the invention

[0006] The purpose of the present invention is to provide a low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent and a preparation method thereof in view of the deficiencies in the prior art. The alkali-free quick-setting agent does not contain sulfate, is non-toxic, and has low corrosiveness, thereby ensuring the safety of storage and use; the stability of the alkali-free quick-setting agent is improved by adding a bentonite organic copolymer; and when applied to concrete, the setting time can be effectively shortened, and the early strength and durability of the concrete can be improved.

[0007] The technical solution adopted by the present invention to achieve the above-mentioned purpose is:

[0008] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials in parts by weight: 20-30 parts of nano-aluminum sol; 15-20 parts of silica sol; 8-10 parts of bentonite organic copolymer; 10-15 parts of aluminum salt; 6-10 parts of composite early strength agent; and 10-15 parts of water.

[0009] Furthermore, the pH value of the nano aluminum sol is 4-5, the content of nano aluminum oxide in the nano aluminum sol is 15-25%; and the content of silicon dioxide in the silica sol is 30-40%.

[0010] Furthermore, the aluminum salt is one or a mixture of aluminum dihydrogen phosphate, aluminum nitrate, and aluminum tartrate.

[0011] Furthermore, the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:1-2; the early strength agent is one or a mixture of calcium formate, calcium acetate, and calcium propionate; the auxiliary early strength agent is one or a mixture of magnesium hydroxide, magnesium dihydrogen phosphate, and magnesium oxide.

[0012] Furthermore, the preparation method of the bentonite organic copolymer is:

[0013] S1. Add nano bentonite to water and disperse it evenly. Add propylene polyhydroxy quaternary ammonium salt and stir to react at 60-70°C for 5-6h. Cool and centrifuge to remove the supernatant. Dry the lower solid to obtain modified bentonite.

[0014] S2, adding modified bentonite to water, dispersing evenly, adding acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, reacting at 70-80° C. for 4-5 hours under nitrogen protection, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain a bentonite organic copolymer;

[0015] Furthermore, in step S1, the mass ratio of the nano-bentonite to the propylene polyhydroxy quaternary ammonium salt is 1:0.3-0.4.

[0016] Furthermore, in step S2, the mass ratio of the modified bentonite, acrylamide, acryloyl polyhydroxy quaternary ammonium salt, and ammonium persulfate is 1:0.6-0.8:0.2-0.3:0.03-0.04.

[0017] In the technical solution of the present invention, the preparation method of the propylene polyhydroxy quaternary ammonium salt is:

[0018] (1) Add 4-chloroaniline and 2,2-dimethylolpropionic acid to N,N-dimethylformamide, stir evenly, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, maintain the reaction temperature at 60-70°C, react for 5-6 hours, cool, filter out insoluble matter, add water and ethyl acetate to the filtrate for extraction, and concentrate the organic phase under reduced pressure to obtain a polyhydroxy compound; the polyhydroxy compound is:

[0019] ;

[0020] (2) Add polyhydroxy compound, 3-bromopropylene and triethylamine to acetonitrile, stir evenly, maintain the reaction temperature at 70-75° C., react for 3-4 hours, cool, remove acetonitrile, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain acryl polyhydroxy compound; the acryl polyhydroxy compound is:

[0021] ;

[0022] (3) Adding acryl polyhydroxy compound and dodecyl dimethyl tertiary amine to ethanol, stirring evenly, maintaining the reaction temperature at 80° C., reflux reaction for 10-12 hours, cooling, removing ethanol, adding water and ethyl acetate for extraction, and concentrating the aqueous phase under reduced pressure to obtain acryl polyhydroxy quaternary ammonium salt, wherein the acryl polyhydroxy quaternary ammonium salt is:

[0023] .

[0024] Furthermore, in step (1), the molar ratio of 4-chloroaniline, 2,2-dihydroxymethylpropionic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.1-1.2:0.5-0.6.

[0025] Furthermore, in step (2), the molar ratio of the polyhydroxy compound, 3-bromopropylene and triethylamine is 1:1-1.1:1.5-1.7.

[0026] Furthermore, in step (3), the molar ratio of the acryl polyol compound to dodecyl dimethyl tertiary amine is 1:1-1.1.

[0027] The present invention also provides a method for preparing a low-corrosive, non-toxic, sulfur-free and alkali-free accelerating setting agent, comprising the following steps: adding water, nano-aluminum sol, silica sol, bentonite organic copolymer and aluminum salt into a reaction container according to a weight ratio, stirring for 1-2 hours at 40-50° C., then adding a composite early strength agent, and continuing to stir for 1-2 hours to obtain a low-corrosive, non-toxic, sulfur-free and alkali-free accelerating setting agent.

[0028] The present invention has the following beneficial effects:

[0029] The invention uses nano bentonite as a raw material, reacts with propylene polyhydroxy quaternary ammonium salt through a cation exchange reaction to obtain modified bentonite, and then polymerizes the modified bentonite with acrylamide and propylene polyhydroxy quaternary ammonium salt under the action of an initiator ammonium persulfate to form a bentonite organic copolymer; the prepared bentonite organic copolymer contains a polyacrylamide molecular structure and a long-chain quaternary ammonium salt structure, has good suspension stability, is used in an accelerator, can improve the suspension stability of the accelerator, and helps to extend the storage period of the accelerator; the bentonite organic copolymer also contains abundant hydroxyl groups and amino groups, and can form a stable complex with aluminum ions. The compound increases the solubility and stability of aluminum ions, helps promote cement hydration, and thus accelerates the setting process of cement. The hydroxyl groups can also react with the silanol groups in the silica sol to promote its gelation and the formation of a three-dimensional network structure, which helps to improve the compactness of the concrete structure. The quick-setting agent containing the bentonite organic copolymer prepared by the present invention can be stably and fully dispersed in the concrete. The nano-bentonite in the bentonite organic copolymer consumes the calcium hydroxide produced by the concrete hydration reaction and generates a hydrated calcium silicate gel, which reduces the porosity of the concrete and makes its internal structure denser, thereby improving the strength and durability of the concrete.

[0030] The alkali-free quick-setting agent provided by the present invention does not contain sulfate, is non-toxic and has low corrosiveness, thereby ensuring the safety of storage and use; the stability of the alkali-free quick-setting agent is improved by adding bentonite organic copolymer; and when applied to concrete, it can effectively shorten the setting time and improve the early strength and durability of concrete. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present application will be clearly and completely described below in combination with the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments; the technical features designed in different implementation modes of the present invention described below can be combined with each other as long as they do not conflict with each other; based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0032] In the technical scheme of the present invention, the chemical reagents used are all commonly available on the market, among which aluminum dihydrogen phosphate CAS No. 13530-50-2; aluminum nitrate CAS No. 13473-90-0; aluminum tartrate CAS No. 815-78-1; calcium formate CAS No. 544-17-2; calcium acetate CAS No. 62-54-4; calcium propionate CAS No. 4075-81-4; magnesium hydroxide CAS No. 1309-42-8; magnesium dihydrogen phosphate CAS No. 13092-66-5; magnesium oxide CAS No. 1309-48-4; acrylamide CAS No. 79-06-1; ammonium persulfate CAS No. 7 727-54-0; 4-chloroaniline CAS No. 106-47-8; 2,2-dihydroxymethylpropionic acid CAS No. 4767-03-7; 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride CAS No. 25952-53-8; 3-bromopropylene CAS No. 106-95-6; triethylamine CAS No. 121-44-8; dodecyldimethyl tertiary amine CAS No. 112-18-5; N,N-dimethylformamide CAS No. 68-12-2; ethyl acetate CAS No. 141-78-6; acetonitrile CAS No. 75-05-8; ethanol CAS No. 64-17-5.

[0033] In the technical solution of the present invention, the preparation method of the propylene polyhydroxy quaternary ammonium salt is:

[0034] ;

[0035] (1) Add 15.0 g of 4-chloroaniline and 17.3 g of 2,2-dimethylolpropionic acid to 600 mL of N,N-dimethylformamide, stir evenly, add 11.3 g of 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, maintain the reaction temperature at 70°C, react for 6 h, cool, filter out insoluble matter, add water and ethyl acetate to the filtrate for extraction, and concentrate the organic phase under reduced pressure to obtain 22.4 g of a polyhydroxy compound; wherein the molar ratio of 4-chloroaniline, 2,2-dimethylolpropionic acid, and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride is 1:1.1:0.5;

[0036] Polyhydroxy compounds: ESI (m / z): 244.1 [M+H] + , 1 H-NMR (600 MHz, DMSO-d 6 , δppm): 9.29 (s, 1H), 7.59 (d, J=8.2Hz, 2H), 7.36 (d, J=8.2Hz, 2H), 6.34 (s, 2H), 3.79 (s, 4H), 1.29 (s, 3H).

[0037] (2) Add 22.0 g of polyhydroxy compound, 11.5 g of 3-bromopropylene and 13.7 g of triethylamine to 500 mL of acetonitrile, stir evenly, maintain the reaction temperature at 75°C, react for 4 h, cool, remove acetonitrile, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain 21.8 g of propylene polyhydroxy compound; wherein the molar ratio of polyhydroxy compound, 3-bromopropylene and triethylamine is 1:1.05:1.5;

[0038] Propylene polyol: ESI (m / z): 284.1 [M+H] + , 1 H-NMR (600 MHz, DMSO-d 6 , δppm): 7.38 (d, J=8.2Hz, 2H), 7.35 (d, J=8.2Hz, 2H), 6.35 (s, 2H), 5.15-5.42 (m, 3H), 4.65-4.70 (m, 2H), 3.78 (s, 4H), 1.29 (s, 3H).

[0039] (3) Add 21.0 g of acryl polyhydroxy compound and 16.6 g of dodecyl dimethyl tertiary amine to 400 mL of ethanol, stir evenly, maintain the reaction temperature at 80°C, reflux for 12 h, cool, remove ethanol, add water and ethyl acetate for extraction, and concentrate the aqueous phase under reduced pressure to obtain 30.5 g of acryl polyhydroxy quaternary ammonium salt; wherein the molar ratio of acryl polyhydroxy compound to dodecyl dimethyl tertiary amine is 1:1.05;

[0040] Propylene polyhydroxy quaternary ammonium salt: ESI (m / z): 497.3 [M+H] + , 1 H-NMR (600 MHz, DMSO-d 6, δppm): 6.78 (d, J=8.2Hz, 2H), 6.59 (d, J=8.2Hz, 2H), 6.32 (s, 2H), 5.14-5.40 (m, 3H), 4.63-4.68 (m, 2H), 3 .78 (s, 4H), 3.33-3.38 (m, 2H), 2.85 (s, 6H), 1.49-1.54 (m, 2H), 1.24-1.32 (m, 21H), 0.88 (t, J=7.1Hz, 3H).

[0041] Embodiment 1

[0042] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 30 parts of nano-aluminum sol; 18 parts of silica sol; 10 parts of bentonite organic copolymer; 15 parts of aluminum salt; 10 parts of composite early strength agent; and 15 parts of water.

[0043] The pH value of the nano aluminum sol is 5, and the content of nano aluminum oxide in the nano aluminum sol is 20%; the content of silicon dioxide in the silica sol is 40%; the aluminum salt is aluminum dihydrogen phosphate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:2; the early strength agent is calcium formate; and the auxiliary early strength agent is magnesium hydroxide.

[0044] The preparation method of bentonite organic copolymer is:

[0045] S1, adding nano bentonite to water, dispersing evenly, adding propylene polyhydroxy quaternary ammonium salt, stirring and reacting at 70°C for 5h, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain modified bentonite; wherein the mass ratio of nano bentonite to propylene polyhydroxy quaternary ammonium salt is 1:0.4;

[0046] S2. Add modified bentonite to water and disperse evenly, add acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, react at 80°C for 5 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of modified bentonite, acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate is 1:0.8:0.3:0.04.

[0047] A method for preparing a low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agent comprises the following steps: adding water, nano-aluminum sol, silica sol, bentonite organic copolymer and aluminum salt into a reaction container according to a weight ratio, stirring for 1.5 hours at 50°C, adding a composite early strength agent, and continuing to stir for 2 hours to obtain a low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agent.

[0048] Embodiment 2

[0049] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 25 parts of nano-aluminum sol; 20 parts of silica sol; 8 parts of bentonite organic copolymer; 13 parts of aluminum salt; 7 parts of composite early strength agent; and 12 parts of water.

[0050] The pH value of the nano aluminum sol is 4, and the content of nano aluminum oxide in the nano aluminum sol is 25%; the content of silicon dioxide in the silica sol is 35%; the aluminum salt is aluminum nitrate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:1.5; the early strength agent is calcium propionate; and the auxiliary early strength agent is magnesium oxide.

[0051] The preparation method of bentonite organic copolymer is:

[0052] S1, adding nano bentonite to water, dispersing evenly, adding propylene polyhydroxy quaternary ammonium salt, stirring and reacting at 60°C for 5.5h, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain modified bentonite; wherein the mass ratio of nano bentonite to propylene polyhydroxy quaternary ammonium salt is 1:0.35;

[0053] S2. Add modified bentonite to water and disperse evenly, add acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, react at 75°C for 4 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of modified bentonite, acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate is 1:0.6:0.2:0.03.

[0054] A method for preparing a low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent comprises the following steps: adding water, nano-aluminum sol, silica sol, bentonite organic copolymer, and aluminum salt into a reaction container according to a weight ratio, stirring for 2 hours at 40°C, adding a composite early strength agent, and continuing to stir for 1 hour to obtain a low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent.

[0055] Embodiment 3

[0056] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 20 parts of nano-aluminum sol; 15 parts of silica sol; 9 parts of bentonite organic copolymer; 10 parts of aluminum salt; 6 parts of composite early strength agent; and 10 parts of water.

[0057] The pH value of the nano aluminum sol is 4.5, and the content of nano aluminum oxide in the nano aluminum sol is 15%; the content of silicon dioxide in the silica sol is 30%; the aluminum salt is aluminum tartrate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:1; the early strength agent is calcium acetate; and the auxiliary early strength agent is magnesium dihydrogen phosphate.

[0058] The preparation method of bentonite organic copolymer is:

[0059] S1, adding nano bentonite to water, dispersing evenly, adding propylene polyhydroxy quaternary ammonium salt, stirring and reacting at 65°C for 6h, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain modified bentonite; wherein the mass ratio of nano bentonite to propylene polyhydroxy quaternary ammonium salt is 1:0.3;

[0060] S2. Add modified bentonite to water and disperse evenly, add acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, react at 70°C for 4.5 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of modified bentonite, acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate is 1:0.7:0.25:0.035.

[0061] A method for preparing a low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent comprises the following steps: adding water, nano-aluminum sol, silica sol, bentonite organic copolymer, and aluminum salt into a reaction container according to a weight ratio, stirring for 1 hour at 45° C., then adding a composite early strength agent, and continuing to stir for 1.5 hours to obtain a low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent.

[0062] Embodiment 4

[0063] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 28 parts of nano-aluminum sol; 17 parts of silica sol; 10 parts of bentonite organic copolymer; 14 parts of aluminum salt; 8 parts of composite early strength agent; and 14 parts of water.

[0064] The pH value of the nano aluminum sol is 5, and the content of nano aluminum oxide in the nano aluminum sol is 25%; the content of silicon dioxide in the silica sol is 35%; the aluminum salt is aluminum tartrate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:1.5; the early strength agent is calcium formate; and the auxiliary early strength agent is magnesium oxide.

[0065] The preparation method of bentonite organic copolymer is:

[0066] S1, adding nano bentonite to water, dispersing evenly, adding propylene polyhydroxy quaternary ammonium salt, stirring and reacting at 70°C for 6 hours, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain modified bentonite; wherein the mass ratio of nano bentonite to propylene polyhydroxy quaternary ammonium salt is 1:0.35;

[0067] S2. Add modified bentonite to water and disperse evenly, add acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, react at 70°C for 4 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of modified bentonite, acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate is 1:0.8:0.2:0.04.

[0068] A method for preparing a low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agent comprises the following steps: adding water, nano-aluminum sol, silica sol, bentonite organic copolymer and aluminum salt into a reaction container according to a weight ratio, stirring for 2 hours at 50°C, adding a composite early strength agent, and continuing to stir for 1.5 hours to obtain a low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agent.

[0069] Comparative Example 1

[0070] Compared with Example 1, the preparation method of the bentonite organic copolymer in this comparative example is different.

[0071] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 30 parts of nano-aluminum sol; 18 parts of silica sol; 10 parts of bentonite organic copolymer; 15 parts of aluminum salt; 10 parts of composite early strength agent; and 15 parts of water.

[0072] The pH value of the nano aluminum sol is 5, and the content of nano aluminum oxide in the nano aluminum sol is 20%; the content of silicon dioxide in the silica sol is 40%; the aluminum salt is aluminum dihydrogen phosphate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:2; the early strength agent is calcium formate; and the auxiliary early strength agent is magnesium hydroxide.

[0073] The preparation method of bentonite organic copolymer is:

[0074] S1, the same as step S1 in embodiment 1;

[0075] S2. Add modified bentonite to water and disperse evenly, add acrylamide and ammonium persulfate, react at 80°C for 5 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of modified bentonite, acrylamide, and ammonium persulfate is 1:0.8:0.04.

[0076] The preparation method of a low-corrosive non-toxic sulfur-free and alkali-free quick-setting agent is the same as that of Example 1.

[0077] Comparative Example 2

[0078] Compared with Example 1, the preparation method of the bentonite organic copolymer in this comparative example is different.

[0079] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 30 parts of nano-aluminum sol; 18 parts of silica sol; 10 parts of bentonite organic copolymer; 15 parts of aluminum salt; 10 parts of composite early strength agent; and 15 parts of water.

[0080] The pH value of the nano aluminum sol is 5, and the content of nano aluminum oxide in the nano aluminum sol is 20%; the content of silicon dioxide in the silica sol is 40%; the aluminum salt is aluminum dihydrogen phosphate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:2; the early strength agent is calcium formate; and the auxiliary early strength agent is magnesium hydroxide.

[0081] The preparation method of bentonite organic copolymer is:

[0082] S1. Add nano bentonite to water and disperse it evenly, add acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, react at 80°C for 5 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of nano bentonite, acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate is 1:0.8:0.3:0.04.

[0083] The preparation method of a low-corrosive non-toxic sulfur-free and alkali-free quick-setting agent is the same as that of Example 1.

[0084] Comparative Example 3

[0085] Compared with Example 1, the preparation method of the bentonite organic copolymer in this comparative example is different.

[0086] A low-corrosive, non-toxic, sulfur-free, and alkali-free quick-setting agent, comprising the following raw materials by weight: 30 parts of nano-aluminum sol; 18 parts of silica sol; 10 parts of bentonite organic copolymer; 15 parts of aluminum salt; 10 parts of composite early strength agent; and 15 parts of water.

[0087] The pH value of the nano aluminum sol is 5, and the content of nano aluminum oxide in the nano aluminum sol is 20%; the content of silicon dioxide in the silica sol is 40%; the aluminum salt is aluminum dihydrogen phosphate; the composite early strength agent is composed of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:2; the early strength agent is calcium formate; and the auxiliary early strength agent is magnesium hydroxide.

[0088] The preparation method of bentonite organic copolymer is:

[0089] S1. Add nano-bentonite to water and disperse it evenly, add acrylamide ammonium persulfate, react at 80°C for 5 hours under nitrogen protection, cool, centrifuge, remove the supernatant, and dry the lower solid to obtain a bentonite organic copolymer; wherein the mass ratio of nano-bentonite, acrylamide, and ammonium persulfate is 1:0.8:0.04.

[0090] The preparation method of a low-corrosive non-toxic sulfur-free and alkali-free quick-setting agent is the same as that of Example 1.

[0091] Performance Testing

[0092] With reference to GB / T 35159-2017 "Accelerator for Shotcrete" and Q / CR 807-2020 "Liquid Alkali-Free Accelerator for Tunnel Shotcrete" standards, the low-corrosive, non-toxic, sulfur-free, alkali-free accelerators prepared in Examples 1 to 4 and Comparative Examples 1 to 3 were tested for stability (measuring the volume of the supernatant after standing for 9 months at 20°C), setting time, compressive strength and other performance tests. The test cement was the benchmark cement P·I42.5, and the dosage was 6% of the cement dosage; the results are shown in Table 1.

[0093] Table 1 Performance test results

[0094]

[0095] After testing, the alkali content (in terms of equivalent Na 2 O content) are less than 1%, and the sulfate content (based on equivalent SO 4 2- Content meter) were not detected, which meets the requirements of sulfur-free and alkali-free accelerator.

[0096] It can be seen from the results in Table 1 that the initial setting time, final setting time, 6h compressive strength, 1d compressive strength, 28d compressive strength ratio, 90d compressive strength retention rate and stability of the low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agents prepared in Examples 1 to 4 of the present invention all meet the requirements of GB / T 35159-2017 and Q / CR 807-2020; compared with Comparative Examples 1 to 3, the bentonite organic copolymer formed by copolymerization of modified bentonite, acrylamide and acryl polyhydroxy quaternary ammonium salt added in Example 1 of the present invention helps to effectively shorten the setting time and improve the early strength and durability of concrete.

[0097] It should be noted that, in this document, terms such as "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device that includes a series of elements includes not only those elements, but also includes other elements that are not explicitly listed, or also includes elements inherent to such process, method, article or device; although the embodiments of the present application have been shown and described, it can be understood by those of ordinary skill 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 present application, and the scope of the present application is defined by the appended claims and their equivalents.

Claims

1. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent, characterized in that: The raw materials include the following parts by weight: 20-30 parts of nano aluminum sol; 15-20 parts of silica sol; 8-10 parts of bentonite organic copolymer; 10-15 parts of aluminum salt; 6-10 parts of composite early strength agent; 10-15 parts of water; The preparation method of the bentonite organic copolymer is: S1. Add nano bentonite to water and disperse it evenly. Add propylene polyhydroxy quaternary ammonium salt and stir to react at 60-70°C for 5-6h. Cool and centrifuge to remove the supernatant. Dry the lower solid to obtain modified bentonite. S2, adding modified bentonite to water, dispersing evenly, adding acrylamide, propylene polyhydroxy quaternary ammonium salt and ammonium persulfate, reacting at 70-80° C. for 4-5 hours under nitrogen protection, cooling, centrifuging, removing the supernatant, and drying the lower solid to obtain a bentonite organic copolymer; The propylene polyhydroxy quaternary ammonium salt is: 。 2. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The preparation method of the propylene polyhydroxy quaternary ammonium salt is: (1) Add 4-chloroaniline and 2,2-dimethylolpropionic acid to N,N-dimethylformamide, stir evenly, add 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride, maintain the reaction temperature at 60-70°C, react for 5-6 hours, cool, filter out insoluble matter, add water and ethyl acetate to the filtrate for extraction, and concentrate the organic phase under reduced pressure to obtain a polyhydroxy compound; (2) Add polyhydroxy compounds, 3-bromopropylene and triethylamine to acetonitrile, stir evenly, maintain the reaction temperature at 70-75°C, react for 3-4 hours, cool, remove acetonitrile, add water and ethyl acetate for extraction, and concentrate the organic phase under reduced pressure to obtain acryl polyhydroxy compounds; (3) Add propylene polyhydroxy compound and dodecyl dimethyl tertiary amine to ethanol, stir evenly, maintain the reaction temperature at 80°C, reflux for 10-12 hours, cool, remove ethanol, add water and ethyl acetate for extraction, and concentrate the aqueous phase under reduced pressure to obtain propylene polyhydroxy quaternary ammonium salt.

3. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 2, characterized in that: The molar ratio of 4-chloroaniline, 2,2-dihydroxymethylpropionic acid and 1-ethyl-(3-dimethylaminopropyl)carbodiimide hydrochloride in step (1) is 1:1.1-1.2:0.5-0.6; the molar ratio of the polyol, 3-bromopropylene and triethylamine in step (2) is 1:1-1.1:1.5-1.7; the molar ratio of the acryl polyol and dodecyl dimethyl tertiary amine in step (3) is 1:1-1.

1.

4. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The pH value of the nano aluminum sol is 4-5, the content of nano aluminum oxide in the nano aluminum sol is 15-25%, and the content of silicon dioxide in the silica sol is 30-40%.

5. The low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The aluminum salt is one or a mixture of aluminum dihydrogen phosphate, aluminum nitrate, and aluminum tartrate.

6. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The composite early strength agent consists of an early strength agent and an auxiliary early strength agent in a mass ratio of 1:1-2.

7. A low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 6, characterized in that: The early strength agent is one of calcium formate, calcium acetate, and calcium propionate, or a mixture of several of them; the auxiliary early strength agent is one of magnesium hydroxide, magnesium dihydrogen phosphate, and magnesium oxide, or a mixture of several of them.

8. The low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The mass ratio of the nano-bentonite to the propylene polyhydroxy quaternary ammonium salt in step S1 is 1:0.3-0.

4.

9. The low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to claim 1, characterized in that: The mass ratio of the modified bentonite, acrylamide, acryloyl polyhydroxy quaternary ammonium salt and ammonium persulfate in step S2 is 1:0.6-0.8:0.2-0.3:0.03-0.

04.

10. A method for preparing the low-corrosive, non-toxic, sulfur-free, alkali-free quick-setting agent according to any one of claims 1 to 9, characterized in that: The method comprises the following steps: adding water, nano aluminum sol, silica sol, bentonite organic copolymer and aluminum salt into a reaction container according to weight ratio, stirring for 1-2 hours at 40-50 DEG C, adding a composite early strength agent, and continuing stirring for 1-2 hours to obtain a low-corrosive, non-toxic, sulfur-free and alkali-free quick-setting agent.

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