Alkali-free accelerator and preparation process thereof

Abstract

The alkali-free accelerator is prepared from the following raw materials and components in percentage by mass: 60 to 65 percent of aluminum sulfate, 7 to 10 percent of organic dissolution promoter, 1 to 2 percent of stabilizer, 1 to 2 percent of early strength agent, 0.5 to 1 percent of pH (Potential of Hydrogen) regulator and the balance of water, and the sum of the mass percent of the components is 100 percent. The organic dissolution promoter is a solution which is prepared by mixing monoethanolamine, glycerol and diethylenetriamine and has the mass fraction of 7%-10%; the mass ratio of the monoethanolamine to the glycerol to the diethylenetriamine is (2-3): (2-3): 1. According to the alkali-free accelerator and the preparation process thereof, glycerol is used as a cosolvent and citric acid is used as a pH regulator, so that the alkali-free accelerator does not cause harm to the environment and people when being used, the safety of the alkali-free accelerator in use is improved, and the alkali-free accelerator is environment-friendly and environment-friendly by using the easily available diatomite. The preparation cost of the alkali-free accelerator can be reduced.

Description

Technical Field

[0001] The invention relates to the technical field of alkali-free accelerating setting agents, in particular to an alkali-free accelerating setting agent and a preparation process thereof. Background Art

[0002] Accelerators are chemical admixtures that make concrete set and harden quickly. They are essential key materials in shotcrete construction and are widely used in tunnel support, mine reinforcement, road repair, waterproofing and plugging and other engineering construction, playing an important role in national infrastructure construction. Accelerators are divided into two categories: powdered accelerators and liquid accelerators. Powdered accelerators are mainly used for dry shotcrete. Dry shotcrete has the disadvantages of large dust, uneven mixing and high rebound, and has been gradually abandoned in tunnel construction. Liquid accelerators are mainly used for wet shotcrete. Compared with dry shotcrete, wet shotcrete has the advantages of better construction environment, low rebound rate of shotcrete and high construction quality. In addition, due to the improvement of engineering durability indicators and environmental protection requirements, the application of liquid accelerators has become increasingly important. The market share of liquid accelerators has increased from 3.1% in 2013 to 63.3% in 2015, and is gradually replacing powdered accelerators.

[0003] Liquid accelerators can be divided into alkali-containing and alkali-free (low-alkali) liquid accelerators according to the alkali metal content. There are obvious differences between the two liquid accelerators in terms of raw material selection, preparation method, performance characteristics and accelerating coagulation mechanism. Liquid alkali accelerators have played an important role in many years of construction applications, but there are also serious problems such as high probability of concrete alkali-aggregate reaction, insufficient 28-day compressive strength ratio, and damage to the health of construction workers. Alkali-free liquid accelerators solve the problem of high alkali content in traditional accelerators and reduce the possibility of alkali-aggregate reaction in shotcrete. The 28d strength ratio of concrete mixed with alkali-free liquid accelerators can reach more than 90%. In addition, alkali-free liquid accelerators are non-corrosive, friendly to the construction environment, and less harmful to the health of construction workers. Therefore, it is an inevitable trend for alkali-free liquid accelerators to replace alkaline accelerators.

[0004] For example, the publication number CN113603384B discloses an ultra-early-strength fluorine-free and alkali-free liquid accelerator and its preparation method. The accelerator is made of the following raw materials: aluminum sulfate, organic dissolution promoter, stabilizer, early strength agent, pH regulator, and water. The organic dissolution promoter is a mixture of three components A, B, and C. A is monoethanolamine, diethanolamine, and triethanolamine; B is N-methyldiethanolamine, N,N-dimethylethanolamine, and N,N-dimethylformamide; C is diethylenetriamine, triethylenetetramine, and tetrahydroxypropylethylenediamine; the stabilizer is ultrafine sepiolite and pseudo-boehmite; the pH regulator is p-toluenesulfonic acid, oxalic acid, and formic acid; the early strength agent is lithium sulfate, magnesium sulfate, nano-silica sol, and nano-aluminum sol. The invention has good performance, simple preparation process, no fluorine, no alkali, no chlorine, and meets the performance requirements of various accelerating agent standards for alkali-free accelerating agents. The 6-hour compressive strength is much greater than 2.5MPa, the 1-day compressive strength is much greater than 15.0MPa, the 90-day compressive strength retention rate is ≥110%, and the stability exceeds 9 months.

[0005] However, N,N-dimethylformamide in the above-mentioned accelerator is an organic solvent, which is harmful to the environment and has adverse effects on human health. At the same time, although toluenesulfonic acid is a commonly used pH regulator, benzenesulfonic acid compounds may have certain toxicity to the environment, thereby making the use of the accelerator less safe. Therefore, the present application proposes an alkali-free accelerator and its preparation process Summary of the invention

[0006] In view of the deficiencies in the prior art, the present invention provides an alkali-free accelerator and a preparation process thereof, which have the advantages of improving the safety of the use of the alkali-free accelerator and the like, and solves the problem that the existing alkali-free accelerator contains raw materials that are harmful to the environment and human body.

[0007] To achieve the above object, the present invention provides the following technical solution: an alkali-free accelerating setting agent, wherein the raw materials and the mass percentages of the components of the alkali-free accelerating setting agent are:

[0008] Aluminum sulfate 60%-65%, organic solvent 7%-10%, stabilizer 1%-2%, early strength agent 1%-2%, pH regulator 0.5%-1%, the balance is water, the sum of the mass percentages of the above components is 100%;

[0009] The organic dissolving agent is a solution with a mass fraction of 7% to 10% prepared by mixing monoethanolamine, glycerol and diethylenetriamine; the mass ratio of the monoethanolamine, the glycerol and the diethylenetriamine is (2 to 3): (2 to 3): 1.

[0010] Furthermore, the purity of the monoethanolamine, glycerol and diethylenetriamine are 99.5%, 95% and 99% of industrial grade respectively.

[0011] Further, the stabilizer is diatomaceous earth;

[0012] The average particle size of the diatomaceous earth is between 2 and 10 microns;

[0013] The specific surface area of ​​the diatomite is in the range of 30-60 m 2 / g;

[0014] The content of SiO2 in the diatomaceous earth should generally be greater than 70%.

[0015] Further, the early strength agent is lithium sulfate;

[0016] The purity of the lithium sulfate should be greater than 98%, and the lithium content (in terms of Li2O) in the lithium sulfate should be above 18%.

[0017] Furthermore, the pH adjuster is citric acid, and the citric acid can pass through a 100-mesh sieve (150 microns).

[0018] The preparation method of the above-mentioned alkali-free accelerating setting agent comprises the following process steps:

[0019] S1: adding monoethanolamine, glycerol and diethylenetriamine into a reaction container and mixing them in a certain proportion, while adding water into the reaction container and stirring evenly to dissolve the monoethanolamine, glycerol and diethylenetriamine;

[0020] S2: adding water into another reaction container, and dissolving aluminum sulfate in the water in another reaction container according to a certain ratio, and stirring evenly until the aluminum sulfate is completely dissolved;

[0021] S3: slowly adding diatomaceous earth into the reaction vessel containing the aluminum sulfate solution, stirring while adding to ensure that the diatomaceous earth is evenly dispersed, and then dissolving lithium sulfate in an appropriate amount of water and adding the solution into the reaction vessel containing the aluminum sulfate solution;

[0022] S4: adding the mixed monoethanolamine, glycerol and diethylenetriamine to a reaction vessel containing aluminum sulfate solution, lithium sulfate and diatomaceous earth, and adjusting the pH value of the mixed solution to a suitable range with citric acid;

[0023] S5: After all components are evenly mixed, a aging treatment is performed for a certain period of time to ensure that each component is fully reacted and stable.

[0024] Compared with the prior art, the technical solution of this application has the following beneficial effects:

[0025] 1. The alkali-free quick-setting agent uses glycerol as a co-solvent and citric acid as a pH regulator, so that the alkali-free quick-setting agent does not cause harm to the environment and people when in use, thereby improving the safety of the alkali-free quick-setting agent when in use. In addition, in the present application, by using diatomaceous earth which is easily available, the preparation cost of the alkali-free quick-setting agent can be reduced.

[0026] 2. The alkali-free accelerator and its preparation process have a simple overall structure and are easy to operate. Not only can the alkali-free accelerator not cause harm to the environment and people, but it can also improve the safety of the alkali-free accelerator during use by using easily available diatomaceous earth, and can also reduce the preparation cost of the alkali-free accelerator. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 It is a schematic diagram of the preparation process in a preferred embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] An alkali-free accelerating setting agent in this embodiment, such as Figure 1 As shown, the raw materials and mass percentages of each component of the alkali-free accelerator are:

[0030] Aluminum sulfate 60%-65%, organic solvent 7%-10%, stabilizer 1%-2%, early strength agent 1%-2%, pH regulator 0.5%-1%, the balance is water, the sum of the mass percentages of the above components is 100%;

[0031] The organic dissolving agent is a solution with a mass fraction of 7% to 10% prepared by mixing monoethanolamine, glycerol and diethylenetriamine; the mass ratio of the monoethanolamine, the glycerol and the diethylenetriamine is (2 to 3): (2 to 3): 1.

[0032] Furthermore, the purity of the monoethanolamine, glycerol and diethylenetriamine are 99.5%, 95% and 99% of the industrial grade respectively; the purity of the monoethanolamine is 99.5% of the industrial grade, and its impurity content is extremely low, which is very important for ensuring the effect of the accelerating agent. High-purity monoethanolamine can more effectively promote the hydrolysis reaction of aluminum sulfate, thereby accelerating the setting process of concrete. In addition, high-purity monoethanolamine can also reduce impurities that may have an adverse effect on the performance of concrete, and improve the stability and reliability of the accelerating agent; glycerol, as a polyhydroxy alcohol, has a purity of 95%. The role of glycerol with high purity in the accelerator is mainly as a co-solvent, helping other components to dissolve and mix better. Glycerol with higher purity can reduce the impact of impurities on the performance of the accelerator and ensure that it plays the expected role in concrete. The purity of diethylenetriamine is 99%, which is a high-purity industrial-grade product. Diethylenetriamine plays a key role in the accelerator. It can not only promote the hydrolysis of aluminum sulfate, but also form a stable complex with calcium ions in concrete, thereby accelerating coagulation. High-purity diethylenetriamine helps to improve the performance of the accelerator and reduce potential risks caused by impurities.

[0033] Furthermore, the stabilizer is diatomaceous earth; the average particle size of the diatomaceous earth is between 2 and 10 microns; the specific surface area of ​​the diatomaceous earth is between 30 and 60 m 2 / g; the content of SiO2 in the diatomite should usually be greater than 70%; diatomite is a naturally occurring mineral with a wide distribution of resources and easy mining, so its raw material cost is low, and the processing process of diatomite is relatively simple, usually only requiring physical treatments such as drying and screening, without complex chemical treatments or high-precision grinding, which reduces the processing cost, so that the use cost of diatomite is lower than that of ultrafine sepiolite and pseudo-boehmite.

[0034] Furthermore, the early strength agent is lithium sulfate; the purity of the lithium sulfate should be greater than 98%, and the lithium content in the lithium sulfate is above 18%. Lithium sulfate, as an effective early strength agent, can promote the acceleration of cement hydration reaction during the setting process of concrete, thereby accelerating the hardening speed of concrete and improving its early strength.

[0035] Furthermore, the pH regulator is citric acid, and the citric acid can pass through a 100-mesh sieve; citric acid is a common organic acid, widely used in food, medicine and industrial fields. In the alkali-free accelerator, citric acid, as a pH regulator, can effectively reduce the pH value of the solution, create a suitable environment, and promote the rapid hydration of tricalcium silicate and dicalcium silicate in cement, thereby accelerating the coagulation and hardening process of concrete. Moreover, the citric acid can pass through a 100-mesh sieve, which means that the particle size of the citric acid is very fine and can smoothly pass through a 100-mesh sieve with an aperture of 150 microns. This particle size requirement ensures that the citric acid can be quickly dissolved in the accelerator and evenly distributed in the concrete, thereby effectively adjusting the pH value of the entire system.

[0036] The preparation method of the above-mentioned alkali-free accelerating setting agent comprises the following process steps:

[0037] S1: adding monoethanolamine, glycerol and diethylenetriamine into a reaction container and mixing them in a certain proportion, while adding water into the reaction container and stirring evenly to dissolve the monoethanolamine, glycerol and diethylenetriamine;

[0038] S2: adding water into another reaction container, and dissolving aluminum sulfate in the water in another reaction container according to a certain ratio, and stirring evenly until the aluminum sulfate is completely dissolved;

[0039] S3: slowly adding diatomaceous earth into the reaction vessel containing the aluminum sulfate solution, stirring while adding to ensure that the diatomaceous earth is evenly dispersed, and then dissolving lithium sulfate in an appropriate amount of water and adding the solution into the reaction vessel containing the aluminum sulfate solution;

[0040] S4: adding the mixed monoethanolamine, glycerol and diethylenetriamine to a reaction vessel containing aluminum sulfate solution, lithium sulfate and diatomaceous earth, and adjusting the pH value of the mixed solution to a suitable range with citric acid;

[0041] S5: After all components are evenly mixed, a aging treatment is performed for a certain period of time to ensure that each component is fully reacted and stable.

[0042] It should be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the existence of other identical elements in the process, method, article or device including the elements.

[0043] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. An alkali-free accelerating setting agent, characterized in that: The raw materials and mass percentages of the components of the alkali-free accelerator are: Aluminum sulfate 60%-65%, organic solvent 7%-10%, stabilizer 1%-2%, early strength agent 1%-2%, pH regulator 0.5%-1%, the balance is water, the sum of the mass percentages of the above components is 100%; The organic dissolving agent is a solution with a mass fraction of 7% to 10% prepared by mixing monoethanolamine, glycerol and diethylenetriamine; the mass ratio of the monoethanolamine, the glycerol and the diethylenetriamine is (2 to 3): (2 to 3):

1.

2. The alkali-free accelerating setting agent according to claim 1, characterized in that: The purity of the monoethanolamine, glycerol and diethylenetriamine are 99.5%, 95% and 99% of industrial grade respectively.

3. The alkali-free accelerating setting agent according to claim 1, characterized in that: The stabilizer is diatomaceous earth; The average particle size of the diatomaceous earth is between 2 and 10 microns; The specific surface area of ​​the diatomite is in the range of 30-60 m 2 / g; The SiO2 content in the diatomaceous earth should generally be greater than 70%.

4. The alkali-free accelerating setting agent according to claim 1, characterized in that: The early strength agent is lithium sulfate; The purity of the lithium sulfate should be greater than 98%, and the lithium content in the lithium sulfate should be greater than 18%.

5. The alkali-free accelerating setting agent according to claim 1, characterized in that: The pH adjuster is citric acid, and the citric acid can pass through a 100-mesh sieve.

6. The preparation process of the alkali-free accelerating setting agent according to any one of claims 1 to 5, characterized in that: The steps include: S1: adding monoethanolamine, glycerol and diethylenetriamine into a reaction container and mixing them in a certain proportion, while adding water into the reaction container and stirring evenly to dissolve the monoethanolamine, glycerol and diethylenetriamine; S2: adding water into another reaction container, and dissolving aluminum sulfate in the water in another reaction container according to a certain ratio, and stirring evenly until the aluminum sulfate is completely dissolved; S3: slowly adding diatomaceous earth into the reaction vessel containing the aluminum sulfate solution, stirring while adding to ensure that the diatomaceous earth is evenly dispersed, and then dissolving lithium sulfate in an appropriate amount of water and adding the solution into the reaction vessel containing the aluminum sulfate solution; S4: adding the mixed monoethanolamine, glycerol and diethylenetriamine to a reaction vessel containing aluminum sulfate solution, lithium sulfate and diatomaceous earth, and adjusting the pH value of the mixed solution to a suitable range with citric acid; S5: After all components are evenly mixed, a aging treatment is performed for a certain period of time to ensure that each component is fully reacted and stable.

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