MXenes low-doped alkali-free liquid accelerator as well as preparation method and application thereof

Abstract

This invention discloses a low-doped, alkali-free liquid accelerator of MXenes, its preparation method, and its application. By weight percentage, the low-doped, alkali-free liquid accelerator of MXenes comprises 0.5%-1.5% MXenes, 47%-62% accelerator, 1.8%-3.8% stabilizer, 1.5%-3% pH adjuster, and the balance being water. The accelerator includes aluminum sulfate compounds, magnesium salts, and dodecacalcium heptaaluminate. The stabilizer is a water-soluble organic compound containing hydroxyl groups. In this invention, the added nano-sized MXenes, due to their unique layered structure, prevent the hydration inhibition of gypsum in the initial stage of cement hydration. Simultaneously, utilizing their small size effect, they increase the cement's viscosity and synergistically promote the cement setting rate with dodecacalcium heptaaluminate, providing a feasible solution for reducing the dosage of accelerators.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of building materials, in particular to a MXenes low-doped alkali-free liquid accelerator and a preparation method thereof. BACKGROUND

[0002] In recent years, tunnel engineering projects have increased, especially the Sichuan-Tibet railway project, which has a total tunnel length of 80% of the total length, and the demand for shotcrete is huge. Accelerator is an indispensable additive for shotcrete, and with the continuous development of shotcrete technology, new requirements are put forward for accelerators.

[0003] With the advancement of wet spraying technology, liquid accelerators currently dominate the market, and commercially available liquid accelerators are mainly divided into two categories: alkaline liquid accelerators and alkali-free liquid accelerators. With the increasing attention to environmental protection and post-performance in construction, alkali-free liquid accelerators have become the mainstream direction of industry development.

[0004] However, the existing alkali-free liquid accelerators generally have a high dosage problem, with a dosage of at least 7%, resulting in high costs and easy occurrence of high rebound rate of shotcrete; in addition, the current production process of alkali-free liquid accelerators is generally at 60-80℃, which has high energy consumption.

[0005] Therefore, there is an urgent need for an alkali-free liquid accelerator that can reduce the doping amount and production energy consumption. SUMMARY

[0006] To solve the problems of high dosage of existing alkali-free liquid accelerators in shotcrete and high cost of alkali-free liquid accelerators, one of the purposes of the present application is to provide a MXenes low-doped alkali-free liquid accelerator.

[0007] The technical solution of the present application to solve the above technical problems is as follows:

[0008] A MXenes low-doped alkali-free liquid accelerator, by weight percentage, includes MXenes 0.5%-1.5%, coagulant 47%-62%, stabilizer 1.8%-3.8%, pH adjuster 1.5%-3%, and the balance water;

[0009] The coagulant includes aluminum sulfate compound, magnesium salt, and dodeca calcium heptanium;

[0010] The stabilizer is an organic substance dissolved in water and containing hydroxyl groups;

[0011] The pH adjuster is an inorganic acid.

[0012] The beneficial effects of the present application are: in the present application, the accelerator introduces the key component MXenes (abbreviated as MXe), which can promote the hydration of cement, especially accelerate the hydration of tricalcium silicate and dicalcium silicate, so that the hydration of cement is more sufficient; secondly, when the accelerator contacts with the cement, the unique lamellar structure of MXe will separate the hydration products of cement from the tricalcium aluminate in the cement, release the retardation effect of gypsum, and accelerate the rapid hydration of tricalcium aluminate in the cement; at the same time, the accelerating component in the present application provides a large amount of Al 3+ , Ca 2+ and SO4 2- , Al 3+ combines with OH - and consumes Ca 2+ to generate calcium aluminate hydrate in the alkaline environment, and SO4 2- reacts with Ca 2+ to generate secondary gypsum with high activity, which reacts with calcium aluminate hydrate to generate a large amount of ettringite, further accelerating the hydration of the original tricalcium aluminate mineral in the cement, so that only a small amount of alkali-free liquid accelerator in the present application is needed to achieve the accelerating effect. Due to the size effect of MXe, a large amount of ettringite, gel and MXe are used to fill and improve the compactness of the concrete, so that the concrete has the characteristics of good mechanical properties. In addition, the stabilizer in the present application can avoid the formation of precipitate when SO4 2- is dissolved, reduce stratification, and improve the stability of the accelerator as a whole; the pH regulator can avoid the precipitation of aluminum sulfate in the alkaline environment, and further improve the stability of the accelerator to a certain extent.

[0013] On the basis of the above technical scheme, the present application can also be improved as follows:

[0014] Further, the accelerating agent includes aluminum sulfate compound 40-50%, magnesium salt 6%-10% and dodeca calcium heptatitanate 1%-2% by weight percentage; preferably, the aluminum sulfate compound is 45%, 50% or 40% by weight percentage, the magnesium salt is 8% or 6% by weight percentage, and the dodeca calcium heptatitanate is 2%, 1% or 1.5% by weight percentage.

[0015] Further, the aluminum sulfate compound is aluminum sulfate octadecahydrate or polyaluminum sulfate, and the magnesium salt is magnesium sulfate heptahydrate.

[0016] Further, the stabilizer includes at least one of diethanolamine, triethanolamine and glycerol.

[0017] Further, the stabilizer includes diethanolamine 1.5%-3% and glycerol 0.3%-0.8% by weight percentage; preferably, the diethanolamine is 1.5%, 3% or 2% by weight percentage, and the glycerol is 0.5%, 0.8% or 0.6% by weight percentage.

[0018] Further, the pH regulator is phosphoric acid or oxalic acid dihydrate; preferably, the pH regulator is 2%, 3% or 1.8% by weight percentage, and further preferably, the pH regulator is preferably phosphoric acid.

[0019] Further, the MXenes are single-layered, and the MXenes are nanoscale; preferably, the size of the MXenes is 800-1000 nm.

[0020] The beneficial effects of the above further technical solutions are that, since the MXe is a nanoscale material and has a unique sheet structure, only a small amount of MXe needs to be added to prevent the hydration inhibition effect of gypsum, which is conducive to the full hydration of cement to achieve rapid setting.

[0021] The second object of the present application is to provide a preparation method of MXenes low-doped alkali-free liquid accelerator, comprising the following steps:

[0022] Step 1, adding a stabilizer and a pH regulator to the remaining water and stirring for 10-20 min;

[0023] Step 2, continue to add aluminum sulfate compound to the remaining water until completely dissolved, then add magnesium salt and dodecacaesium heptanium aluminate, stir and stand for 70-90 min;

[0024] Step 3, add MXenes and stir for 30 min, and obtain MXenes low-doped alkali-free liquid accelerator after standing.

[0025] The third object of the present application is to provide an application of MXenes low-doped alkali-free liquid accelerator in shotcrete.

[0026] Further, the MXenes low-doped alkali-free liquid accelerator in shotcrete has a dosage of 3-55 wt.%; preferably, the MXenes low-doped alkali-free liquid accelerator in shotcrete has a dosage of 45 wt.%; the dosage in the present application is based on the gel material in the concrete.

[0027] The present application has the following beneficial effects:

[0028] 1. In the present application, nanoscale MXe is introduced into the alkali-free accelerator, due to its unique sheet structure, it prevents the hydration inhibition effect of gypsum in the initial stage of cement hydration, and at the same time, it increases the adhesion of cement by using its small size effect, and greatly promotes the setting speed of cement together with dodecacaesium heptanium aluminate, thereby reducing the dosage of the accelerator in the present application in the concrete.

[0029] 2. In the present application, due to the addition of MXe, the problem of insufficient cement rapid setting and hydration is solved, and at the same time, it can refine the pore structure of cement, significantly increase the late strength of cement mortar, and enhance the durability of shotcrete.

[0030] 3. The MXe olefin low-doped alkali-free liquid accelerator in this invention can be prepared at room temperature to obtain a stable MXe olefin low-doped alkali-free liquid accelerator. This accelerator is an environmentally friendly alkali-free accelerator. Detailed Implementation

[0031] The principles and features of the present invention are described below with reference to embodiments. These embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Unless otherwise specified, specific conditions or manufacturer-recommended conditions should be followed in the embodiments. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0032] Example 1

[0033] A method for preparing a low-doped, alkali-free liquid rapid-setting agent for MXe olefins includes the following steps:

[0034] Step 1: Add 1.5% diethanolamine, 0.5% glycerol, and 2% phosphoric acid to the weighed deionized water in sequence according to the measured amount. Turn on the stirrer and stir at 100 r / min for 10 min to obtain a mixture.

[0035] Step 2: Add 45% aluminum sulfate octadecahydrate to the mixture and stir until it is completely dissolved. Then add 8% magnesium sulfate heptahydrate and 2% dodecacalceate heptahydrate and stir at 100 r / min for 70 min.

[0036] Step 3: Add 1% MXe ene, and then stir at a stirring speed of 350 r / min for 30 min. After standing, the low-doped alkali-free liquid quick-setting agent of MXe ene is obtained. MXe ene is usually added after being ultrasonically dispersed in deionized water to form a suspension. MXe ene is a monolayer with a particle size of 900 nm. MXe ene is MXenes-Ti3C2Tx.

[0037] This embodiment also includes the MXe olefin low-doped alkali-free liquid rapid-setting agent prepared by the above method.

[0038] Example 2

[0039] A method for preparing a low-doped, alkali-free liquid rapid-setting agent for MXe olefins includes the following steps:

[0040] Step 1: Add 3% diethanolamine, 0.8% glycerol, and 3% phosphoric acid sequentially to the weighed deionized water according to the measured amount. Turn on the stirrer and stir at a speed of 100 r / min for 15 min to obtain a mixture.

[0041] Step 2: Add 50% aluminum sulfate octadecahydrate to the mixture and stir until it is completely dissolved. Then add 6% magnesium sulfate heptahydrate and 1% dodecacalceate heptahydrate and stir at 100 r / min for 80 min.

[0042] Step 3: Add 0.5% MXe ene, and then stir at a stirring speed of 350 r / min for 30 min. After standing, the low-doped alkali-free liquid quick-setting agent of MXe ene is obtained. MXe ene is usually added after being ultrasonically dispersed in deionized water to form a suspension. MXe ene is a monolayer with a particle size of 800 nm. MXe ene is MXenes-Ti3C2Tx.

[0043] This embodiment also includes the MXe olefin low-doped alkali-free liquid rapid-setting agent prepared by the above method.

[0044] Example 3

[0045] A method for preparing a low-doped, alkali-free liquid rapid-setting agent for MXe olefins includes the following steps:

[0046] Step 1: Add 2% diethanolamine, 0.6% glycerol, and 1.8% phosphoric acid to the weighed deionized water in sequence according to the measured amount. Turn on the stirrer and stir at 100 r / min for 20 min to obtain a mixture.

[0047] Step 2: Add 40% aluminum sulfate octadecahydrate to the mixture and stir until it is completely dissolved. Then add 6% magnesium sulfate heptahydrate and 1.5% dodecacalceate heptahydrate and stir at 100 r / min for 90 min.

[0048] Step 3: Add 1.5% MXe ene, and then stir at a stirring speed of 350 r / min for 30 min. After standing, the low-doped alkali-free liquid quick-setting agent of MXe ene is obtained. MXe ene is usually added after being ultrasonically dispersed in deionized water to form a suspension. MXe ene is a monolayer with a particle size of 1000 nm. MXe ene is MXenes-Ti3C2Tx.

[0049] This embodiment also includes the MXe olefin low-doped alkali-free liquid rapid-setting agent prepared by the above method.

[0050] Comparative Example 1

[0051] A commercially available alkali-free liquid quick-setting agent, fluorine-free and chlorine-free, such as YQ-3 model alkali-free liquid quick-setting agent.

[0052] Comparative Example 2

[0053] A commercially available alkali-free liquid accelerator, fluorosilicic acid system, for example, FT-A type alkali-free liquid accelerator.

[0054] Comparative Example 3

[0055] A commercially available alkali-free liquid accelerator, hydrofluoric acid system, for example, YS-300 alkali-free liquid accelerator.

[0056] Comparative Example 4

[0057] The preparation method of the alkali-free liquid quick-setting agent in this comparative example is the same as that in Example 1, except that MXenes-Ti3C2Tx is not added in step 3.

[0058] This comparative example also includes an alkali-free liquid accelerator prepared by the above method. The difference between this alkali-free liquid accelerator and the low-doped MXeene alkali-free liquid accelerator in Example 1 is that the alkali-free liquid accelerator in this comparative example does not contain MXenes-Ti3C2Tx.

[0059] Comparative Example 5

[0060] The preparation method of the alkali-free liquid quick-setting agent in this comparative example is the same as that in Example 1, except that in step 3, MXenes-Ti3C2Tx is replaced with bentonite with a lamellar structure.

[0061] This comparative example also includes an alkali-free liquid accelerator prepared by the above method. The difference between this alkali-free liquid accelerator and the low-doped MXeene alkali-free liquid accelerator in Example 1 is that MXenes-Ti3C2Tx is replaced with bentonite in the alkali-free liquid accelerator of this comparative example.

[0062] Performance test analysis:

[0063] The MXe olefin low-doped alkali-free liquid accelerators from Examples 1, 2, and 3 were used at 4% and 3% dosages, respectively. The alkali-free liquid accelerators obtained in Comparative Examples 1-5 were used at 7% dosage. Reference cement was used for testing. In this invention, the initial setting and final setting properties, as well as the strength, of the prepared accelerators were evaluated according to the evaluation standards in the national standard GB / T 35159-2017 "Accelerators for Shotcrete". The test results are shown in Table 1.

[0064] Table 1. Performance Tests of Accelerators

[0065]

[0066]

[0067] As can be seen from Example 1 and Comparative Example 4 in Table 1, Example 1 contains 1.5% MXe ene, while the comparative example does not contain MXe ene. The setting time of Example 1 at low dosages of 4% and 3% is better than that of Comparative Example 4 at a dosage of 7%. This indicates that MXe ene is a key component for reducing the dosage of accelerators and accelerating cement setting.

[0068] As can be seen from Examples 1 and 2-3 in Table 1, the MXe ene content in Example 1 is 1.5%, which is higher than that in Examples 2-3. The setting time of Example 1 with a low accelerator dosage of 4% and 3% is shorter than that in Examples 2-3. This indicates that a higher MXe ene content in the accelerator results in better cement setting effect. The present invention recommends an MXe ene content of 0.5%-1.5%.

[0069] Furthermore, as can be seen from Example 1 and Comparative Example 4, when the accelerator without MXeene has a higher doping amount than the accelerator in this invention, its initial setting time and final setting time are both extended, and its 1-day compressive strength and 28-day compressive strength are both reduced. This shows that MXeene is beneficial for shortening the initial setting time and final setting time, which is beneficial for the full hydration of cement and thus improves the strength of cement.

[0070] Furthermore, it can be seen from Example 1 and Comparative Example 5 that when other materials with a sheet-like structure are selected, the initial setting time and final setting time are prolonged when the doping amount is greater than that of the accelerator in this invention, and the 1-day compressive strength and 28-day compressive strength do not change significantly compared to the accelerator in this invention.

[0071] In summary, the MXe olefin low-doped alkali-free liquid accelerator provided by this invention has the advantages of low dosage, good setting effect, high early strength, high strength retention rate in the later stage, simple production process, and green and environmentally friendly.

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A low-doped, alkali-free liquid quick-setting agent for MXenes, characterized in that, By weight percentage, it includes 0.5%-1.5% MXenes, 47%-62% coagulant, 1.8%-3.8% stabilizer, 1.5%-3% pH adjuster, and the balance water; The coagulant includes aluminum sulfate compounds, magnesium salts, and dodecacalcium heptaaluminate. The stabilizer is a water-soluble organic compound containing hydroxyl groups; The pH adjuster is an inorganic acid; The coagulant comprises 40-50% aluminum sulfate compound, 6%-10% magnesium salt, and 1%-2% dodecacalcium heptaaluminate; the aluminum sulfate compound is aluminum sulfate octadecahydrate or polyaluminum sulfate, and the magnesium salt is magnesium sulfate heptahydrate; the MXenes are monolayer and nanoscale.

2. The MXenes low-doped alkali-free liquid quick-setting agent according to claim 1, characterized in that, The stabilizer includes at least one of diethanolamine, triethanolamine, and glycerol.

3. The MXenes low-doped alkali-free liquid quick-setting agent according to claim 2, characterized in that, The stabilizer comprises, by weight percentage, 1.5%-3% diethanolamine and 0.3%-0.8% glycerol.

4. The MXenes low-doped alkali-free liquid quick-setting agent according to claim 1, characterized in that, The pH adjuster is phosphoric acid or oxalic acid dihydrate.

5. The method for preparing the MXenes low-doped alkali-free liquid rapid-setting agent according to any one of claims 1 to 4, characterized in that, Includes the following steps: Step 1: Add the stabilizer and pH adjuster to the remaining water and stir for 10-20 minutes; Step 2: Continue adding aluminum sulfate compound to the remaining water until it is completely dissolved, then add magnesium salt and dodecacalcein heptaaluminate and stir for 70-90 minutes. Step 3: Add MXenes and stir for 30 minutes. After standing, obtain MXenes low-doped alkali-free liquid quick-setting agent.

6. The application of the MXenes low-doped alkali-free liquid quick-setting agent according to any one of claims 1 to 4 in the preparation of shotcrete.

7. The application according to claim 6, characterized in that, The amount of MXenes low-doped alkali-free liquid accelerator in the sprayed concrete is 3~5 wt.%.

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