A set-accelerating early-strength agent for shotcrete and a method for preparing the same

Abstract

The application discloses a kind of early strength agent for shotcrete and its preparation method, early strength agent prepared by silicon phase and calcium phase is used as internal phase oil phase with urea-based dispersant, water and polycarboxylic acid water reducing agent are mixed as external phase water phase, after sufficient reaction, early strength agent for shotcrete is obtained by centrifugal separation;Preparation method is specifically as follows: (1) urea-based superdispersant is prepared by free radical copolymerization reaction. (2) microfluidic chip is prepared by etching. (3) water phase and oil phase are pumped into chip respectively, and early strength agent is prepared after centrifugation. The application uses microfluidic technology, the preparation condition is mild, the production cost can be reduced, and the production is stable.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to an accelerator for shotcrete and its preparation method. Background Technology

[0002] In the construction of modern tunnels and other underground engineering projects, a crucial step is the rapid implementation of support measures after excavation. In this stage, the early strength development of shotcrete is vital for ensuring the effectiveness of the support and directly impacts the overall project schedule. Therefore, early strength is more important than its final strength. In my country, one of the biggest challenges facing shotcrete construction is the slow development of early strength. This problem severely affects the technical support effectiveness of tunnels and other underground excavation projects. Although various accelerator products are available on the market that can meet the requirements for rapid setting and hardening to some extent, their early strength within 6 and 12 hours is still relatively low, far from meeting the rapid support needs of some urgent projects, thus affecting the progress of tunnel construction.

[0003] In the current scientific research field, research on accelerators for setting and early strength is still relatively limited, and their application is mainly concentrated in oil well cement. A Chinese patent (patent number CN113583642A) discloses the formulation, preparation technology, and application examples of a modified nano-silica accelerator for setting and early strength in oil well cement. The formulation includes the following components: anhydrous sodium metasilicate, calcium nitrate tetrahydrate, a 40% sodium hydroxide solution, a 36%-37% formaldehyde aqueous solution, vilan gum, nano-titanium dioxide, and softened water. Another Chinese patent (patent number CN112592091A) introduces an accelerator for setting and early strength suitable for 3D printing cement-based materials, characterized by containing a random copolymer polymerized from specific monomers. Specifically, these monomers include 60-70 parts by weight of unsaturated polyether, 15-25 parts by weight of unsaturated carboxylic acid or unsaturated carboxylates, and 3-20 parts by weight of polar unsaturated monomers. In addition, this accelerator also contains 10-20 parts of chitosan-coated calcium fluoroaluminate. Another Chinese patent (CN116119968A) also discloses a formulation for an accelerator used in shotcrete. It utilizes a novel dispersant obtained by copolymerizing pentaerythritol, methacrylic acid, and polyether macromonomers, and applying this dispersant to the accelerator system yields excellent performance.

[0004] The aforementioned patents all involve accelerators for early strength and coagulation prepared under normal macroscopic turbulent stirring conditions. While these methods offer some improvement in early strength, issues such as unstable properties and tendency to solidify and precipitate over long-term storage persist, affecting their effectiveness. Compared to macroscopic flow, the microscopic motion of fluids exhibits superior properties, leading to the development of a new synthetic technique—microfluidics. Microfluidics enables precise control of microdroplets, rapidly and efficiently generating uniformly sized and controllable microdroplets. This facilitates the preparation of highly efficient and stable accelerators for early strength and coagulation, meeting construction requirements and improving the construction environment. Summary of the Invention

[0005] 1. The technical problem to be solved:

[0006] To address the aforementioned technical problems, this invention provides an accelerator for shotcrete and its preparation method, which solves the problems of unstable properties and easy precipitation during long-term storage of existing accelerators. At the same time, it can improve the early strength of shotcrete, enhance the support effect, reduce rebound, and improve the construction environment of shotcrete.

[0007] 2. Technical Solution:

[0008] An accelerator for shotcrete, employing a centrifugal microcontroller chip, uses an accelerator prepared from silicon and calcium phases and a urea-based dispersant as the internal oil phase, and water and a polycarboxylate superplasticizer as the external aqueous phase. After sufficient reaction, the mixture is centrifuged to obtain the accelerator for shotcrete. Specifically, it is made from the following components and raw materials in the following mass fractions: 500-5000 parts of the accelerator precursor prepared from silicon and calcium phases, 1-10 parts of the oil phase, 1-5 parts of the urea-based dispersant, and 2500-10000 parts of the aqueous phase. The raw materials for preparing the urea-based dispersant include, by weight, 1-5 parts of urea-based olefin, 2-20 parts of unsaturated polyether macromonomer or unsaturated ester macromonomer, and 5-30 parts of allylsilane.

[0009] A method for preparing an accelerator for shotcrete, comprising the following steps:

[0010] Step 1: Preparation of urea-based superdispersant; An unsaturated primary amine compound and a first solvent are stirred in a reaction flask, and 4-nitrobenzene chloroformate is added dropwise at 0–10°C. The mixture is stirred at room temperature for 0.5–1 h, and after washing and purification, a nitrobenzenoxycarbonyl compound is obtained. The nitrobenzenoxycarbonyl compound is mixed with a second solvent, and an amine compound is added at room temperature. After stirring for 0.5–1 h, the mixture is washed and purified to obtain a urea-based olefin. The urea-based olefin, unsaturated polyether macromonomer or unsaturated ester macromonomer, and allylsilane are subjected to a redox free radical polymerization reaction at 5–50°C under the combined action of an initiator, a reducing agent, and a chain transfer agent for 3–5 hours to obtain the urea-based superdispersant. The molecular structure of the urea-based superdispersant is as follows:

[0011]

[0012] In the above formula, the degree of polymerization m is 1 to 100; the degree of polymerization n is 1 to 100; the degree of polymerization p is 20 to 100; r and d are each independently 0 to 200; R3 is one of H, alkali metal ions, and alkyl groups containing 1 to 6 carbon atoms; R5 is one of alkyl groups containing 1 to 10 carbon atoms and carbonyl groups containing 1 to 10 carbon atoms; R1, R2, R4, R6 to R11 are any one or more combinations of alkyl groups containing 1 to 4 carbon atoms, hydroxyalkyl groups containing 1 to 4 carbon atoms, or alkoxy groups containing 1 to 4 carbon atoms.

[0013] Step 2: Fabrication of the microfluidic chip: The microchannel structure of the microfluidic chip includes a substrate and an inner phase channel, an outer phase channel, and an S-shaped channel disposed inside the substrate; the inner phase channel is sleeved in the inner cavity of the outer phase channel, and the sample outlet of the inner phase channel is located in the outer phase channel; the inner phase liquid of the inner phase channel mixes with the outer phase liquid of the outer phase channel and then enters the S-shaped channel and flows out from the sample outlet of the microfluidic chip;

[0014] Step 3: Preparation of the coagulation accelerator and early strength agent: First, the silica salt and calcium salt are fully homogenized in a high-speed homogenizer to obtain the early strength agent precursor; then, the urea-based superdispersant, oil and early strength agent precursor are mixed to prepare the inner phase oil phase; water and polycarboxylate superplasticizer are mixed to prepare the outer phase aqueous phase; the outer phase and inner phase are pumped into the microfluidic chip respectively, and after flowing out from the S-shaped channel, they are first collected in a container, and then the materials in the container are separated to obtain the coagulation accelerator and early strength agent.

[0015] Further, in step one, the unsaturated primary amine compound is any one or a combination of two or more of allylamine, allylamine, methyl allylamine, methyl allylamine, dimethyl allylamine, and dimethyl allylamine.

[0016] Further, in step one, the first solvent is any one or a combination of two or more of acetonitrile, methanol, ethanol, acetone, dichloromethane (DCM), chloroform, benzene, dimethyl sulfoxide (DMSO), N,N-dimethylformamide (DMF), and 1,2-dichloroethane; the second solvent is any one or a combination of two or more of 1,6-aminohexanol, pyridine, dimethylpyridine, and p-dimethylaminopyridine; and the amine compound is any one or a combination of two or more of methylamine, ethylamine, dimethylamine, triethylamine, and ammonium monohydrate.

[0017] Further, in step one, the unsaturated polyether macromonomer or unsaturated ester macromonomer is any one or a combination of two or more of allyl polyethylene glycol, polyethylene glycol methacrylate, methallyl polyoxyethylene ether, isopentenyl polyoxyethylene ether, polyethylene glycol monomethacrylate, and methoxy polyethylene glycol acrylate.

[0018] Further, in step one, the allylsilane is any one or a combination of two or more of allyltrimethoxysilane, methylallyltrimethoxysilane, allyltriethoxysilane, and methylallyltriethoxysilane.

[0019] Further, in step one, the initiator is any one or a combination of two or more of ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, sodium persulfate, potassium persulfate, and azobisisoheptanenitrile; the reducing agent is any one or a combination of two or more of sodium sulfite, sodium bisulfite, sodium metabisulfite, sodium hypophosphite, and L-ascorbic acid; and the chain transfer agent is any one or a combination of two or more of mercaptoethanol, sodium methacrylate sulfonate, 3-mercaptopropionic acid, mercaptoacetic acid, 2-mercaptopropionic acid, and dodecanethiol.

[0020] Furthermore, in step one, the molar ratio of ureoolefin, unsaturated polyether macromonomer or unsaturated ester macromonomer, and allylsilane is (1-5):(2-20):(5-30).

[0021] Further, in step three, the silicate is any one or a combination of two or more of alkaline silica sol, sodium silicate, potassium silicate, sodium metasilicate, methyl orthosilicate, ethyl orthosilicate, and lithium silicate; the calcium salt is any one or a combination of two or more of calcium acetate, calcium nitrate, calcium chloride, calcium sulfate, calcium gluconate, calcium hydrogen phosphate, and calcium lactate; the molar ratio of silicate to calcium salt is 1:1 to 3; the homogenization conditions are: homogenization speed of 7000 to 15000 rpm; homogenization time of 1200 to 1800 s; the oil is any one or a combination of two or more of silicone oil, lubricating oil, corn oil, and palm oil; the molar ratio of urea-based superdispersant, oil, and early strength agent precursor is (1 to 5):(1 to 10):(500 to 5000).

[0022] Furthermore, in step three, the internal phase flow rate through the microfluidic chip is 200–700 μL / h, and the external phase flow rate is 3000–4000 μL / h; the internal phase diameter of the microfluidic chip is 0.05–50 μm, and the external phase diameter is 0.5–150 μm; the centrifugation conditions for the microfluidic chip are: centrifugation speed of 2000–4000 rpm; and centrifugation time of 1–5 min.

[0023] 3. Beneficial effects:

[0024] (1) The preparation method of the sprayed concrete accelerator for early setting and strength disclosed in this invention has mild preparation conditions, which can reduce production costs and stabilize production.

[0025] (2) In the preparation method of the accelerator for shotcrete disclosed in this invention, the aqueous phase and the oil phase are pumped into the microfluidic chip respectively. The particle size of the product is small and uniform. The urea-based dispersant used can effectively disperse the accelerator precursor uniformly and stably in the aqueous phase, avoid the internal aggregation of the precursor molecules and reduce the accelerator effect, and the system has good stability.

[0026] (3) Experimental data clearly show that the accelerator and quick-setting agent system prepared by the present invention have very good compatibility. It has a good accelerator and quick-setting effect at a low dosage, which can effectively reduce the rebound rate, greatly improve the construction environment, and prevent the strength from shrinking in the later stage. Attached Figure Description

[0027] Figure 1 This is a schematic diagram of the microfluidic chip in this invention;

[0028] Figure 2 This is a schematic diagram of the internal and external phase mixing principle in this invention. Detailed Implementation

[0029] The present invention will now be described in detail with reference to the accompanying drawings.

[0030] The microfluidic chip designed in this invention is shown in the attached figure. Figure 1 , 2 As shown, the fabrication steps of the microfluidic chip in this method are as follows: First, the microchannel structure of the microfluidic chip is drawn and then fabricated as a mask. The design pattern is shown in the attached figure. Figure 1 As shown. Then, a photoresist is coated onto the silicon wafer surface using a spin coater at a temperature of 60–90°C for 2–10 minutes. Next, a positive film is fabricated using UV exposure and then heat-treated. Then, a mixture of polydimethylsiloxane and a curing agent is poured onto the positive pattern, and the wafer is cured at 50–100°C under vacuum. Finally, a cover plate is placed on top, and the microfluidic chip is obtained using plasma sealing. The volume ratio of the polydimethylsiloxane to the curing agent mixture is (20–8):1.

[0031] Example 1

[0032] 1 mol of allylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, allyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of methylamine was slowly added at room temperature. After stirring for 1 h, washing and purification yielded allyl methylurea. 1 mol of allyl methylurea, 5 mol of allyl polyethylene glycol, and 10 mol of allyl trimethoxysilane were subjected to a redox free radical polymerization reaction at 30 °C for 3 h in the presence of 0.07 mol ammonium persulfate, 0.1 mol sodium sulfite, and 0.05 mol mercaptoethanol to prepare a urea-based superdispersant. The molecular structure is as follows:

[0033]

[0034] The degree of polymerization n is 35; the degree of polymerization m is 40; the degree of polymerization p is 28; and the degree of polymerization r is 12.

[0035] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0036] 1.2 mol potassium silicate and 2 mol calcium chloride were simply mixed and homogenized in a high-speed homogenizer at 7000 rpm for 1500 s to obtain a precursor for the coagulation-accelerating agent. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 5 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 500 μL / h, and the outer phase at a flow rate of 3500 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 3000 rpm for 3 min to finally obtain the coagulation-accelerating agent.

[0037] Example 2

[0038] 1 mol of allylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, allyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of ammonia monohydrate was slowly added at room temperature. After stirring for 1 h, washing and purification yielded allyl urea. 1 mol of allyl urea, 5 mol of methyl allyl polyoxyethylene ether, and 10 mol of allyl trimethoxysilane were subjected to a redox free radical polymerization reaction at 30 °C for 3 h in the presence of 0.07 mol of ammonium persulfate, 0.08 mol of sodium sulfite, and 0.04 mol of mercaptoethanol to prepare a urea-based superdispersant. The molecular structure is as follows:

[0039]

[0040] The degree of polymerization n is 37; the degree of polymerization m is 40; the degree of polymerization p is 28; and the degree of polymerization r is 12.

[0041] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0042] 1.2 mol sodium silicate and 2 mol calcium chloride were simply mixed and homogenized in a high-speed homogenizer at 15000 rpm for 1800 s to obtain a precursor for the coagulation-accelerating agent. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 10 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 500 μL / h, and the outer phase at a flow rate of 3500 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 2000 rpm for 2 min to finally obtain the coagulation-accelerating agent.

[0043] Example 3

[0044] 1 mol of methylallylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, methylallyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of ammonia monohydrate was slowly added at room temperature. After stirring for 1 h, washing and purification yielded allyl methylurea. 1 mol of allyl methylurea, 5 mol of polyethylene glycol monoacrylate, and 10 mol of methylallyltrimethoxysilane were subjected to a redox free radical polymerization reaction at 30 °C for 3 h in the presence of 0.07 mol ammonium persulfate, 0.1 mol sodium sulfite, and 0.05 mol mercaptoethanol to obtain a urea-based superdispersant. The molecular structure is as follows:

[0045]

[0046] The degree of polymerization n is 36; the degree of polymerization m is 38; the degree of polymerization p is 25; and the degree of polymerization r is 11.

[0047] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0048] 1.2 mol sodium silicate and 2 mol calcium nitrate were simply mixed and homogenized in a high-speed homogenizer at 12000 rpm for 1600 s to obtain a coagulation-accelerating agent precursor. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 10 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 600 μL / h, and the outer phase at a flow rate of 3600 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 4000 rpm for 3 min to finally obtain the coagulation-accelerating agent.

[0049] Example 4

[0050] 1 mol of allylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, allyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of methylamine was slowly added at room temperature. After stirring for 1 h, washing and purification yielded allyl methylurea. 1 mol of allyl methylurea, 5 mol of allyl polyethylene glycol, and 10 mol of allyl trimethoxysilane were subjected to a redox free radical polymerization reaction at 30 °C for 3 h in the presence of 0.07 mol ammonium persulfate, 0.1 mol sodium sulfite, and 0.05 mol mercaptoethanol to prepare a urea-based superdispersant. The molecular structure is as follows:

[0051]

[0052] The degree of polymerization n is 35; the degree of polymerization m is 40; the degree of polymerization p is 28; and the degree of polymerization r is 12.

[0053] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0054] 1.2 mol potassium silicate and 2 mol calcium chloride were simply mixed and homogenized in a high-speed homogenizer at 10,000 rpm for 1500 s to obtain a precursor for the coagulation-accelerating agent. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 10 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 500 μL / h, and the outer phase at a flow rate of 3500 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 3000 rpm for 3 min to finally obtain the coagulation-accelerating agent.

[0055] Example 5

[0056] 1 mol of methylallylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, methylallyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of ammonia monohydrate was slowly added at room temperature. After stirring for 1 h, washing and purification yielded methylallylurea. 1 mol of methylallylurea, 5 mol of polyethylene glycol monoacrylate, and 10 mol of methylallyltriethoxysilane were subjected to a redox radical polymerization reaction at 30 °C for 3 h in the presence of 0.07 mol ammonium persulfate, 0.1 mol sodium sulfite, and 0.05 mol mercaptoethanol to obtain a urea-based superdispersant. The molecular structure is as follows:

[0057]

[0058] The degree of polymerization n is 35; the degree of polymerization m is 40; the degree of polymerization p is 28; and the degree of polymerization d is 12.

[0059] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0060] 1.2 mol potassium silicate and 2 mol calcium chloride were simply mixed and homogenized in a high-speed homogenizer at 10,000 rpm for 1500 s to obtain a precursor for the coagulation-accelerating agent. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 10 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 500 μL / h, and the outer phase at a flow rate of 3500 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 3000 rpm for 3 min to finally obtain the coagulation-accelerating agent.

[0061] Example 6

[0062] 1 mol of allylamine was stirred with 70 mL of dichloromethane in a reaction flask. 1.1 mol of 4-nitrobenzene chloroformate was added dropwise at 0–10 °C, and stirring continued at room temperature for 0.5 h. After washing and purification, allyl carbamate was obtained. 1 mol of this compound was mixed with 40 mL of a pyridine / 1,6-aminohexanol solution (v / v = 1:2), and 1.1 mol of ammonia monohydrate was slowly added at room temperature. After stirring for 1 h, washing and purification yielded allyl methylurea. 1 mol of allylurea, 5 mol of allyl polyethylene glycol, and 10 mol of allyltriethoxysilane were subjected to a redox free radical polymerization reaction at 30 °C for 3 h in the presence of 0.06 mol of ammonium persulfate, 0.09 mol of sodium sulfite, and 0.05 mol of mercaptoethanol to prepare a urea-based superdispersant. The molecular structure is as follows:

[0063]

[0064] The degree of polymerization n is 38; the degree of polymerization m is 41; the degree of polymerization p is 28; and the degree of polymerization r is 12.

[0065] Fabrication of microfluidic chips (see attached) Figure 1 , 2 ).

[0066] 1.2 mol potassium silicate and 2 mol calcium chloride were simply mixed and homogenized in a high-speed homogenizer at 11000 rpm for 1500 s to obtain a precursor for the coagulation-accelerating agent. 1 mol urea-based superdispersant, 0.5 mol lubricating oil, and 1500 mol of the coagulation-accelerating agent precursor were directly mixed as the inner phase of the microfluidic chip; 1000 ml of water and 10 g of polycarboxylate superplasticizer were directly mixed as the outer phase of the microfluidic chip. The inner phase was pumped into the microfluidic chip at a flow rate of 500 μL / h, and the outer phase at a flow rate of 3500 μL / h. The inner and outer phases reacted fully in the microfluidic chip to obtain the sample. The sample was collected and centrifuged at 3000 rpm for 3 min to finally obtain the coagulation-accelerating agent.

[0067] Test case

[0068] 1. Stability Test

[0069] Control group 1 used a commercially available accelerator from a certain manufacturer. The stability of the accelerator was tested according to the Q / CR 807-2020 standard. The experiment involved storing the accelerator at different temperatures for a period of time. The stability evaluation criteria were: if the volume of the supernatant or bottom sediment in 100 ml of accelerator did not exceed 5 ml, the stability was considered acceptable; otherwise, it was unacceptable. After 3 months of storage, the viscosity of the accelerator was tested. According to the test results in Table 1, acceptable stability was indicated by "√", and unacceptable stability was indicated by "×".

[0070] Table 1. Stability and viscosity tests

[0071]

[0072]

[0073] As can be seen from Table 1, the coagulation and early strength accelerator prepared in this invention has good stability.

[0074] 2. Shotcrete performance test

[0075] Control group 1 used a commercially available early-strength agent from a certain manufacturer, while control group 2 was a blank group. The dosage of the accelerator was 2% of the cement mass, and the dosage of the quick-setting agent was 6% of the cement mass. The concrete strength was tested according to GB8076-2012 "Concrete Admixtures". The test results are shown in Table 2.

[0076] Table 2 Performance Tests of Shotcrete

[0077]

[0078] As shown in Table 2, the accelerator for setting and early strength prepared in this invention can improve the performance of shotcrete, has excellent early strength effect, significantly improves early strength, and also has a certain improvement on 28-day strength.

[0079] 3. Shotcrete rebound rate test

[0080] Control group 1 used a commercially available early-strength agent from a certain manufacturer. Rebound rate tests were conducted on each example according to the methods mentioned in Appendix G of JGJ / T372-2016 "Technical Specification for Application of Shotcrete". The test results are shown in Table 3.

[0081] Table 3 Rebound Rate Test

[0082]

[0083] As shown in Table 3, the accelerator for setting and early strength prepared in this invention can reduce the rebound rate of shotcrete and improve the construction site environment.

[0084] Although the present invention has been disclosed above with reference to preferred embodiments, these are not intended to limit the invention. Any person skilled in the art can make various changes or modifications without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention should be defined by the scope of the claims of this application.

Claims

1. A method for preparing a set accelerating early strength agent for sprayed concrete, characterized by: The method comprises the following steps: Step one: preparing urea-based hyperdispersant; stirring unsaturated primary amine compound with first solvent in a reaction bottle, adding chloroformic acid-4-nitrophenyl ester dropwise at 0-10 DEG C, stirring at room temperature for 0.5-1h, and obtaining nitrophenyloxycarbonyl compound after washing and purification; mixing nitrophenyloxycarbonyl compound with second solvent, adding amine compound at room temperature, stirring for 0.5-1h, and obtaining urea-based olefin after washing and purification; and preparing urea-based hyperdispersant by carrying out oxidation-reduction radical polymerization of urea-based olefin, unsaturated polyether macromonomer or unsaturated ester macromonomer and allyl silane under the action of initiator, reducing agent and chain transfer agent at 5-50 DEG C for 3-5 hours; the molecular structure of urea-based hyperdispersant is as follows: ； In the formula, the polymerization degree m is 1-100; the polymerization degree n is 1-100; the polymerization degree p is 20-100; r and d are each independently 0-200; R3 is H, alkali metal ion, one of alkyl containing 1-6 carbon atoms; R5 is one of alkyl containing 1-10 carbon atoms, carbonyl containing 1-10 carbon atoms; R1, R2, R4, R6-R11 are any one or combination of alkyl containing 1-4 carbon atoms, hydroxyalkyl containing 1-4 carbon atoms or alkoxy containing 1-4 carbon atoms; Step two: preparing microfluidic chip; the microchannel structure of the microfluidic chip comprises a substrate and internal phase channels, external phase channels and S-shaped channels arranged inside the substrate; the internal phase channels are sleeved in the internal cavities of the external phase channels, and the sample outlets of the internal phase channels are located in the external phase channels; The internal phase liquid of the internal phase channels and the external phase liquid of the external phase channels are mixed and then enter the S-shaped channels to flow out of the sample outlets of the microfluidic chip; Step three: preparing early strength accelerator; first, homogenize the silicon salt and calcium salt in a high-speed homogenizer to obtain early strength accelerator precursor; then, mix the urea-based hyperdispersant, oil and early strength accelerator precursor to prepare internal phase oil phase; mix water and polycarboxylic acid water reducing agent to prepare external phase water phase; pump the external phase and the internal phase into the microfluidic chip, and then collect them in a container; and finally, separate the materials in the container to obtain the early strength accelerator.

2. The method of claim 1, wherein the method is characterized by: In step one, the unsaturated primary amine compound is any one or combination of two or more of allyl amine, alkenyl amine, methyl allyl amine, methyl alkenyl amine, dimethyl allyl amine and dimethyl alkenyl amine.

3. The method of claim 1, wherein the method is characterized by: In step one, the first solvent is any one or combination of two or more of acetonitrile, methanol, ethanol, acetone, dichloromethane, chloroform, benzene, dimethyl sulfoxide, N,N-dimethylformamide and 1,2-dichloroethane; the second solvent is any one or combination of two or more of 1,6-amino hexanol, pyridine, dimethylpyridine and p-dimethylaminopyridine; and the amine compound is any one or combination of two or more of methylamine, ethylamine, dimethylamine and triethylamine.

4. The method of claim 1, wherein the method is characterized by: In step one, the unsaturated polyether macromonomer or unsaturated ester macromonomer is any one of allyl polyethylene glycol, polyethylene glycol methacrylate, methallyl polyoxyethylene ether, prenol polyoxyethylene ether, polyethylene glycol mono-methacrylate, methoxy polyethylene glycol acrylate or a combination of two or more thereof.

5. The method of claim 1, wherein the method is characterized by: In step one, the allyl silane is any one of allyl trimethoxysilane, methallyl trimethoxysilane, allyl triethoxysilane, methallyl triethoxysilane or a combination of two or more thereof.

6. The method of claim 1, wherein the method is characterized by: In step one, the initiator is any one of ammonium persulfate, hydrogen peroxide, azobisisobutyronitrile, sodium persulfate, potassium persulfate, azobisisoheptyl nitrile or a combination of two or more thereof; the reducing agent is any one of sodium sulfite, sodium bisulfite, sodium metabisulfite, sodium hypophosphite, L-ascorbic acid or a combination of two or more thereof; the chain transfer agent is any one of mercaptoethanol, sodium methallyl sulfonate, 3-mercaptopropionic acid, mercaptoacetic acid, 2-mercaptopropionic acid, dodecanethiol or a combination of two or more thereof.

7. The method of claim 1, wherein the method is characterized by: In step one, the molar ratio of urea-based olefin, unsaturated polyether macromonomer or unsaturated ester macromonomer, and allyl silane is (1-5):(2-20):(5-30).

8. The method of claim 1, wherein the method is characterized by: In step three, the silicon salt is any one of basic silica sol, sodium silicate, potassium silicate, sodium metasilicate, methyl orthosilicate, ethyl orthosilicate, lithium silicate or a combination of two or more thereof; the calcium salt is any one of calcium acetate, calcium nitrate, calcium chloride, calcium sulfate, calcium gluconate, calcium hydrogen phosphate, calcium lactate or a combination of two or more thereof; the molar ratio of silicon salt to calcium salt is 1:1-3; the homogenization condition is that the homogenization speed is 7000-15000 rpm and the homogenization time is 1200-1800 s; the oil is any one of silicone oil, lubricating oil, corn oil, palm oil or a combination of two or more thereof; the molar ratio of urea-based hyperdispersant, oil, and early strength agent precursor is (1-5):(1-10):(500-5000).

9. The method of claim 1, wherein the method is characterized by: In step three, the inner phase flow rate of the microfluidic chip is 200-700 μL / h and the outer phase flow rate is 3000-4000 μL / h; the inner phase diameter of the microfluidic chip is 0.05-50 μm and the outer phase diameter is 0.5-150 μm; the centrifugation condition of the microfluidic chip is that the centrifugation speed is 2000-4000 rpm and the centrifugation time is 1-5 min.

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