Early-strength liquid low-alkali accelerator, preparation method and sprayed concrete

Abstract

The application provides an early-strength liquid low-alkali accelerator, a preparation method and a shotcrete, and the method is as follows: a modified calcium silicate crystal solution is added dropwise into alcoholized alkaline aluminum sol, and early-strength liquid low-alkali accelerator is obtained after 3-4 hours of reaction; the alcoholized alkaline aluminum sol is prepared from sodium hydroxide, aluminum hydroxide, acidic aluminum hydroxide gel and alcohol; and raw materials of the modified calcium silicate crystal include a surface modifier, glycerol, ethylene glycol, hydrated magnesium silicate, sodium silicate nine hydrate, sodium metaaluminate, calcium nitrate and water. The application can improve the early strength of the shotcrete without using external admixtures.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of concrete early strength agent, and particularly relates to an early-strength liquid low-alkali accelerator, a preparation method and sprayed concrete. BACKGROUND

[0002] Sprayed concrete is a construction method of spraying concrete with a pressure spray gun, and is commonly used for thin-walled structure protection layers such as tunnel lining and walls. Sprayed concrete is formed by spraying the pre-prepared cement, sand, gravel, water and a certain amount of additive into a spraying machine, mixing them with the accelerator in the nozzle by using high-pressure air, and then spraying them onto the surface of the rock or concrete. As an initial support layer, sprayed concrete needs to be quickly solidified and cured in a short time and has a certain compressive strength. Although the addition of the accelerator can make the sprayed concrete solidify and cure in a short time, it cannot make the strength of the sprayed concrete continue to increase rapidly in a short time.

[0003] According to the sprayed concrete accelerator standard (GB / T 35159-2017), although liquid accelerators are divided into alkaline and non-alkaline accelerators, the requirements for early strength of both are 24-hour compressive strength ≥ 7 MPa. The Q / CR 807-2020 national railway group technical standard “Liquid non-alkaline accelerator for tunnel sprayed concrete” requires that the non-alkaline accelerator has a 6-hour compressive strength ≥ 1 MPa and a 24-hour compressive strength ≥ 10 MPa. In the actual application process, the strength of the non-alkaline accelerator and the alkaline accelerator of several accelerators was compared. The 6-hour compressive strength of the non-alkaline accelerator was less than 1 MPa, the 8-hour compressive strength was less than 2 MPa, the 6-hour compressive strength of the alkaline accelerator was less than 2 MPa, and the 8-hour compressive strength was less than 3 MPa. Compared with several non-alkaline accelerators of the national railway standard, the 6-hour compressive strength was less than 1.8 MPa, and the 8-hour compressive strength was 2.5 MPa.

[0004] In order to solve the problem of the early strength of the existing sprayed concrete, there are two common methods at present: 1. Adding aluminate fast-hardening cement admixture, such as a silicon-manganese slag-based super-early-strength sprayed concrete admixture (patent CN202211382864.5) of Guizhou Tianwei, which is synthesized by using silicon-manganese slag, silica fume, aluminate cement, sodium nitrite, water reducing agent and other materials. The early-strength admixture can have an 8-hour strength greater than 10 MP without affecting the workability of the sprayed concrete. 2. Adding early-strength crystal glue, which is generally hydrated calcium silicate crystal glue. The application of hydrated calcium silicate suspension as an early-strength agent in cement-based materials can significantly promote the hydration of cement and improve the early strength of cement-based materials. Although these two methods can solve the problem of insufficient early strength of sprayed concrete, they both involve adding admixture materials to the concrete, which has certain negative effects on the workability, mixing method and material cost of the concrete. SUMMARY

[0005] The present application aims to overcome the shortcomings of the prior art, and provides a preparation method of early strength liquid low-alkali accelerator, which improves the early strength of sprayed concrete without using external admixtures, and is specifically implemented by the following technical scheme:

[0006] The present application provides a preparation method of early strength liquid low-alkali accelerator, which comprises the following steps:

[0007] The early strength liquid low-alkali accelerator is obtained by adding a modified calcium silicate crystal solution to alcoholized alkaline aluminum sol and reacting for 3-4 hours;

[0008] The alcoholized alkaline aluminum sol is prepared from sodium hydroxide, aluminum hydroxide, acidic aluminum hydroxide gel and alcohol;

[0009] The raw materials of the modified calcium silicate crystal include a surface modifier, glycerol, ethylene glycol, hydrated magnesium silicate, sodium silicate, sodium metaaluminate, calcium nitrate and water.

[0010] Optionally or preferably, the configuration step of the alcoholized alkaline aluminum sol is as follows: S1, reacting sodium hydroxide and aluminum hydroxide into a 50% concentration sodium metaaluminate solution, and adding alcohol substances to perform preliminary alcoholization in the reaction; S2, alcoholizing aluminum hydroxide and alkaline alcohol with a PH value of 2 to obtain a weak acidic aluminum salt solution with a PH value of 4-6; S3, adding the weak acidic aluminum salt solution obtained in step S2 to a 65 DEG C sodium aluminate solution under a high-speed emulsifier to make the PH value reach 11, so as to obtain a semi-transparent alcoholized alkaline aluminum sol.

[0011] Optionally or preferably, the sodium-aluminum ratio of sodium hydroxide and aluminum hydroxide is 1:1.18.

[0012] Optionally or preferably, the raw materials of the surface modifier include iso-pentenyl polyoxyethylene, polyethylene glycol monomethyl ether esterification macromonomer and water.

[0013] Optionally or preferably, the configuration step of the surface modifier is as follows: S1, adding iso-pentenyl polyoxyethylene, polyethylene glycol monomethyl ether esterification macromonomer and water into a reaction kettle with a stirrer, increasing the temperature in the reaction kettle to 35 DEG C, and stirring the colorless transparent solution in the reaction kettle; S2, simultaneously adding three solutions A, B and C into the reaction kettle, wherein the A solution is a mixed solution of acrylic acid and water, the B solution is a mixed solution of ascorbic acid, mercaptoacetic acid and water, and the C solution is a mixed solution of hydrogen peroxide, sodium gluconate and water; S3, adding solid sodium hydroxide into the reaction kettle and stirring until dissolved, to obtain a colorless transparent surface modifier.

[0014] Optionally or preferably, the surface modifier is prepared by mixing isopentenyl polyoxyethylene 40-50%, polyethylene glycol monomethyl ether esterified macromonomer 0.2-1%, acrylic acid 3-4% g, ascorbic acid 0.01-0.1%, mercaptoacetic acid 0.1-2%, hydrogen peroxide 1-6%, sodium gluconate 1.15-1.20%, solid sodium hydroxide 0.5-0.8% g, and water.

[0015] Optionally or preferably, the configuration step of the modified calcium silicate crystal comprises the following steps: S1, adding water and a surface modifier into a reaction kettle at room temperature; S2, stirring for 15 minutes by using a high-speed emulsifier; S3, simultaneously adding a modified sodium silicate nonahydrate solution and a calcium nitrate solution into the reaction kettle, and the dropping time is 40 minutes; and S4, continuing to stir for 30 minutes after the dropping is completed, to obtain the modified calcium silicate crystal.

[0016] Optionally or preferably, the rotating speed of the high-speed emulsifier is not less than 3000 r / min.

[0017] Optionally or preferably, the configuration step of the modified sodium silicate nonahydrate solution comprises the following steps: S1, adding water, glycerol, ethylene glycol and hydrated magnesium silicate into a reaction kettle with a stirrer, and stirring for 15 minutes; S2, adding sodium silicate nonahydrate, and stirring for 1 hour after the temperature is increased to 55°C; and S3, adding sodium metaaluminate, and reacting for 30 minutes at 55°C, to obtain the modified sodium silicate nonahydrate solution.

[0018] Based on the above technical solution, the early-strength liquid low-alkali accelerator preparation method provided by the application can produce the following technical effects:

[0019] (1) High stability, no precipitation for 90 days in an alkaline environment;

[0020] (2) Good early-strength effect, the 24-hour concrete compressive strength can exceed 20 MPa;

[0021] (3) The early-strength effect is better than the quick-setting effect, and when the shotcrete is prepared, the early-strength agent and the quick-setting agent do not need to be added separately, thereby reducing the process steps. BRIEF DESCRIPTION OF DRAWINGS

[0022] In order to more clearly illustrate the technical solutions in the embodiments of the application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or the prior art description. Obviously, the drawings in the following description only show some embodiments of the application, and other drawings can be obtained by those skilled in the art without any creative effort on the basis of the drawings shown.

[0023] Figure 1 The flowchart of the application. DETAILED DESCRIPTION

[0024] It should be understood that the specific embodiments described herein are merely exemplary and are not intended to limit the present application.

[0025] The technical solutions in the embodiments of the present application will be clearly and completely described with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of protection of the present application.

[0026] In a preferred embodiment,

[0027] As Figure 1 shown, a preparation method of early-strength liquid low-alkali accelerator is provided, comprising the following steps:

[0028] S1, preparing an alcoholized basic aluminum sol, the steps are:

[0029] (1) reacting sodium hydroxide and aluminum hydroxide with a sodium-aluminum ratio of 1:1.18 into a 50% concentration sodium metaaluminate solution, and adding an alcohol substance in the reaction to perform preliminary alcoholization;

[0030] (2) alcoholizing aluminum hydroxide with a PH value of 2 and basic alcohol to obtain a weak acidic aluminum salt solution with a PH value of 4-6;

[0031] (3) under a high-speed emulsifier, dropping the weak acidic aluminum salt solution obtained in step S2 into a 65℃ sodium aluminate liquid to make the PH value reach 11, that is, to obtain a semi-transparent alcoholized basic aluminum sol.

[0032] S2, preparing a surface modifier, the steps are:

[0033] (1) adding isopentenyl polyoxyethylene accounting for 40-50%, polyethylene glycol monomethyl ether esterification macromonomer accounting for 0.2-1%, and water accounting for 20-40% into a reaction kettle with a stirrer, raising the temperature in the reaction kettle to 35℃, and stirring the solution in the reaction kettle until it is colorless and transparent;

[0034] (2) simultaneously dropping A, B, and C solutions into the reaction kettle, wherein A is a mixture of acrylic acid accounting for 3-4% and water accounting for 2-5%, B is a mixture of ascorbic acid accounting for 0.01-0.1%, mercaptoacetic acid accounting for 0.1-2%, and water accounting for 5-8%, and C is a mixture of hydrogen peroxide accounting for 1-6%, sodium gluconate accounting for 1.15-1.20%, and water accounting for 5-8%;

[0035] (3) adding solid sodium hydroxide accounting for 0.5-0.8% into the reaction kettle and stirring until it is dissolved to obtain a colorless and transparent surface modifier.

[0036] S3, preparing modified calcium silicate crystals, the steps are:

[0037] (1) adding water and a surface modifier to a reaction kettle at room temperature;

[0038] (2) stirring for 15 minutes using a high-speed emulsifier;

[0039] (3) simultaneously adding a modified sodium silicate solution and a calcium nitrate solution to the reaction kettle dropwise, with a dropwise addition time of 40 minutes;

[0040] (4) continuing to stir at high speed for 30 minutes after the dropwise addition is complete, to obtain modified calcium silicate crystals.

[0041] S4, under stirring using a high-speed emulsifier, adding a certain amount of modified calcium silicate crystal solution to a heat-insulated alcoholized basic aluminum sol, and obtaining an early-strength liquid low-alkali accelerator after 3-4 hours of reaction.

[0042] The early-strength liquid low-alkali accelerator prepared in this example does not affect the workability of the sprayed concrete, has a small slump, and its stability is as shown in Table 1:

[0043] Table 1

[0044]

[0045] The mix proportion of the sprayed concrete of this example is as shown in Table 2:

[0046] Table 2

[0047] Material Cement Sand Stone (5-10mm) Water Water reducing agent Accelerator Ratio kg / m 3 ]] 450 899 830 171 4.5 36

[0048] The strength of the early-strength liquid low-alkali accelerator prepared in this example compared with existing accelerators is as shown in Table 3:

[0049] Table 3

[0050]

[0051] The performance indicators of the early-strength liquid low-alkali accelerator prepared in this example are as shown in Table 4:

[0052] Table 4

[0053] Performance Index Appearance White translucent liquid Solid content 53％ PH 11 Alkaline content 5.5％ Chloride ion content 0.023％ Fluoride ion content 0.012％ Dosage 8％ 28-day strength retention rate ≥95％

[0054] The foregoing is considered as illustrative only of the principles of the application. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the application to the exact construction and operation described. Accordingly, all such variations are intended to be included within the scope of the present application as defined in the claims below and their equivalents.

Claims

1. A method for preparing an early-strength liquid low-alkali quick-setting agent, characterized in that: Add modified calcium silicate crystal solution dropwise to alcoholized alkaline aluminum sol, and after reacting for 3-4 hours, an early-strength liquid low-alkali rapid-setting agent is obtained. The alcoholized alkaline aluminum sol is formulated from sodium hydroxide, aluminum hydroxide, acidic aluminum hydroxide gel, and alcohols. The raw materials for the modified calcium silicate crystals include surface modifier, glycerol, ethylene glycol, hydrated magnesium silicate, sodium silicate nonahydrate, sodium aluminate, calcium nitrate, and water. The preparation steps of the alcoholized alkaline aluminum sol are as follows: S1, react sodium hydroxide and aluminum hydroxide to form a 50% sodium aluminate solution, and add alcohols to the reaction for preliminary alcoholization; S2, alcoholize the aluminum hydroxide gel with a pH of 2 and the alkaline alcohols to obtain a weakly acidic aluminum salt solution with a pH of 4-6; S3, add the weakly acidic aluminum salt solution obtained in step S2 dropwise to a 65°C sodium aluminate liquid under a high-speed emulsifier to make its pH reach 11, thereby obtaining a translucent alcoholized alkaline aluminum sol; The preparation steps of the modified calcium silicate crystals are as follows: S1, add water and surface modifier to the reaction vessel at room temperature; S2, stir for 15 minutes using a high-speed emulsifier; S3, simultaneously add modified sodium silicate nonahydrate solution and calcium nitrate solution to the reaction vessel for 40 minutes; S4, continue high-speed stirring for 30 minutes after the addition is complete to obtain modified calcium silicate crystals. The raw materials for preparing the modified sodium silicate nonahydrate solution include glycerol, ethylene glycol, hydrated magnesium silicate, sodium silicate nonahydrate, and sodium aluminate.

2. The method for preparing an early-strength liquid low-alkali quick-setting agent according to claim 1, characterized in that: In the preparation of the alcoholized alkaline aluminum sol, in step S1, the sodium-aluminum ratio is 1:1.

18.

3. The method for preparing an early-strength liquid low-alkali quick-setting agent according to claim 1, characterized in that: The raw materials for the surface modifier include isopentenyl polyoxyethylene, polyethylene glycol monomethyl ether esterified macromonomer, and water.

4. A method for preparing an early-strength liquid low-alkali quick-setting agent according to claim 3, characterized in that: The preparation steps of the surface modifier are as follows: S1, add isopentenyl polyoxyethylene, polyethylene glycol monomethyl ether esterified macromonomer and water to a reactor equipped with a stirrer, raise the temperature inside the reactor to 35°C, and stir to make the solution colorless and transparent; S2, simultaneously add three solutions A, B and C to the reactor, wherein solution A is a mixture of acrylic acid and water, solution B is a mixture of ascorbic acid, mercaptoacetic acid and water, and solution C is a mixture of hydrogen peroxide, sodium gluconate and water; S3, add solid sodium hydroxide to the reactor and stir until dissolved to obtain a colorless and transparent surface modifier.

5. The method for preparing an early-strength liquid low-alkali quick-setting agent according to claim 4, characterized in that: The surface modifier comprises the following raw materials in the following proportions: 40-50% isopentenyl polyoxyethylene, 0.2-1% polyethylene glycol monomethyl ether esterified macromonomer, 3-4% acrylic acid, 0.01-0.1% ascorbic acid, 0.1-2% mercaptoacetic acid, 1-6% hydrogen peroxide, 1.15-1.20% sodium gluconate, 0.5-0.8% solid sodium hydroxide, and the balance being water.

6. The method for preparing an early-strength liquid low-alkali quick-setting agent according to claim 1, characterized in that: The preparation steps of the modified sodium silicate nonahydrate solution are as follows: S1, add water, glycerol, ethylene glycol and magnesium silicate hydrate to a reaction vessel equipped with a stirrer and stir for 15 minutes; S2, add sodium silicate nonahydrate, heat to 55°C and stir for 1 hour; S3, add sodium aluminate and react at a constant temperature of 55°C for 30 minutes to obtain the modified sodium silicate nonahydrate solution.

7. An early-strength liquid low-alkali quick-setting agent, characterized in that: It is prepared using any one of the early-strength liquid low-alkali quick-setting agents as described in claims 1-6.

8. A type of shotcrete, characterized in that, Add the early-strength liquid low-alkali quick-setting agent as described in claim 7.

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