CN113698124A - Alkali-free liquid accelerator and preparation method thereof - Google Patents
Alkali-free liquid accelerator and preparation method thereof Download PDFInfo
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- CN113698124A CN113698124A CN202111077341.5A CN202111077341A CN113698124A CN 113698124 A CN113698124 A CN 113698124A CN 202111077341 A CN202111077341 A CN 202111077341A CN 113698124 A CN113698124 A CN 113698124A
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B40/00—Processes, in general, for influencing or modifying the properties of mortars, concrete or artificial stone compositions, e.g. their setting or hardening ability
- C04B40/0028—Aspects relating to the mixing step of the mortar preparation
- C04B40/0039—Premixtures of ingredients
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- C—CHEMISTRY; METALLURGY
- C04—CEMENTS; CONCRETE; ARTIFICIAL STONE; CERAMICS; REFRACTORIES
- C04B—LIME, MAGNESIA; SLAG; CEMENTS; COMPOSITIONS THEREOF, e.g. MORTARS, CONCRETE OR LIKE BUILDING MATERIALS; ARTIFICIAL STONE; CERAMICS; REFRACTORIES; TREATMENT OF NATURAL STONE
- C04B2103/00—Function or property of ingredients for mortars, concrete or artificial stone
- C04B2103/10—Accelerators; Activators
- C04B2103/12—Set accelerators
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- Organic Chemistry (AREA)
- Curing Cements, Concrete, And Artificial Stone (AREA)
- Compounds Of Alkaline-Earth Elements, Aluminum Or Rare-Earth Metals (AREA)
Abstract
The invention discloses an alkali-free liquid accelerator and a preparation method thereof, and relates to the technical field of concrete additives. The alkali-free liquid accelerator comprises the following raw material components in parts by mass: 440-460 parts of aluminum sulfate, 110-130 parts of magnesium sulfate, 10-13 parts of sodium metaaluminate, 1-4 parts of sodium fluoride, 10-15 parts of nano silicon dioxide, 50-70 parts of diethanolamine oxalate, 8-13 parts of triethanolamine and 300-350 parts of water. Through the design of the raw materials and the proportion thereof, the prepared alkali-free setting accelerator has the advantages of low fluoride ion concentration, safety, environmental protection, stable storage quality, good setting accelerating effect, and high early strength and middle and later strength of concrete.
Description
Technical Field
The invention relates to the technical field of concrete additives, in particular to an alkali-free liquid accelerator and a preparation method thereof.
Background
The concrete accelerator is an additive capable of enabling concrete to be rapidly solidified and hardened, and after the concrete accelerator is doped into concrete, the concrete can be initially set within 2-5 min and finally set within 5-10 min. With the acceleration of the large-scale highway network and railway network engineering construction in China and the increasing of the projects of mining and submarine tunnel excavation, the demand of the accelerator for sprayed concrete is increased. Because the environmental conditions of underground engineering are complex, the development trend of the construction and application of modern concrete is that the sprayed concrete has high performance, and therefore, higher requirements are provided for the performance quality of the accelerating agent.
The accelerator for sprayed concrete is generally an alkali accelerator and an alkali-free accelerator, and the fluoride ion concentration in the alkali-free accelerator is generally higher, so that the accelerating effect is ensured, but the chloride ion source in the conventional alkali-free liquid accelerator is hydrofluoric acid or fluorosilicic acid which is a carcinogenic substance extremely harmful to human bodies, so that the potential safety hazard seriously affecting the health of construction personnel exists in the production and use process when the accelerator is used in a large amount, the hydration of cement is blocked, and the early 1-day strength of concrete is low. At present, alkali-free liquid setting accelerators capable of reducing the content of fluoride ions exist, but the setting accelerating effect is poor, so that the setting time of concrete is long, the standard is not met, and the 28-day strength of the concrete is reduced.
In addition, the alkali-free liquid accelerator has high aluminum sulfate content and limited solubility of aluminum sulfate, and when the sulfate radical content is too high, aluminum ions can be hydrolyzed and aggregated in an aqueous solution, so that the phenomena of crystallization and precipitation and unstable storage quality are easily caused, and the normal use of the accelerator is influenced.
Disclosure of Invention
The invention mainly aims to provide an alkali-free liquid accelerator and a preparation method thereof, and aims to provide an alkali-free liquid accelerator which is safe, environment-friendly, good in accelerating effect, high in early and later strength and stable in storage.
In order to achieve the purpose, the invention provides an alkali-free liquid accelerator which comprises the following raw material components in parts by mass:
440-460 parts of aluminum sulfate, 110-130 parts of magnesium sulfate, 10-13 parts of sodium metaaluminate, 1-4 parts of sodium fluoride, 10-15 parts of nano silicon dioxide, 50-70 parts of diethanolamine oxalate, 8-13 parts of triethanolamine and 300-350 parts of water.
Optionally, in the alkali-free liquid accelerator, the weight parts of the raw materials are as follows:
450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 65 parts of diethanolamine oxalate, 10 parts of triethanolamine and 328.75 parts of water.
Further, the invention also provides a preparation method of the alkali-free liquid accelerator, which comprises the following steps:
s10, dissolving magnesium sulfate in water to obtain a mixed solution;
s20, dissolving sodium fluoride, sodium metaaluminate, aluminum sulfate, triethanolamine and nano silicon dioxide in the mixed solution to obtain a first solution;
and S30, adding diethanolamine oxalate into the first solution for a complexing reaction to obtain the alkali-free liquid accelerator.
Optionally, in step S10, the dissolution temperature of the dissolution is 60 to 80 ℃.
Optionally, step S20 includes:
adding nano silicon dioxide into triethanolamine at the temperature of 60-80 ℃, and stirring for 0.5-1 h to obtain a milky mixture;
and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 20-40 min to obtain a first solution.
Optionally, before step S30, the method further includes the following steps:
under the stirring state, dripping oxalic acid into diethanol amine to obtain an intermediate solution;
and adding concentrated sulfuric acid into the intermediate solution, and reacting at 80-90 ℃ for 1-2 h to obtain diethanolamine oxalate.
Optionally, the mass ratio of the oxalic acid to the diethanolamine to the concentrated sulfuric acid is 40-50: 10-15: 1 to 4.
Optionally, in step S30, the time of the complexation reaction is 20-40 min.
In the technical scheme provided by the invention, the alkali-free liquid accelerator is prepared by taking 440-460 parts of aluminum sulfate, 110-130 parts of magnesium sulfate, 10-13 parts of sodium metaaluminate, 1-4 parts of sodium fluoride, 10-15 parts of nano silicon dioxide, 50-70 parts of diethanolamine oxalate, 8-13 parts of triethanolamine and 300-350 parts of water as raw materials, and can form a stable complex with active aluminum ions in a solution by adding a stabilizer diethanolamine oxalate, so that the content of the active aluminum ions in the solution is improved, the coagulation promoting effect is better, and aluminum hydroxide precipitation caused by instability can be prevented, thereby improving the storage stability of the alkali-free accelerator; the addition of sodium fluoride can play a role in auxiliary complexation, so that the coagulation promoting effect and the storage stability are further improved; by adopting the nano silicon dioxide to replace part of sodium fluoride, the early strength is improved on the premise of ensuring the strength in the middle and later periods. Namely, the alkali-free setting accelerator disclosed by the invention has the advantages that through the design of raw materials and the proportion thereof, the prepared alkali-free setting accelerator is low in fluoride ion concentration, safe and environment-friendly, stable in storage quality, good in setting accelerating effect, and high in early strength and middle and later strength of concrete.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
It should be noted that those whose specific conditions are not specified in the examples were performed according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially. In addition, the meaning of "and/or" appearing throughout includes three juxtapositions, exemplified by "A and/or B" including either A or B or both A and B. In addition, technical solutions between various embodiments may be combined with each other, but must be realized by a person skilled in the art, and when the technical solutions are contradictory or cannot be realized, such a combination should not be considered to exist, and is not within the protection scope of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The invention provides an alkali-free liquid accelerator, and aims to provide a liquid accelerator with excellent comprehensive performance. In one embodiment, the alkali-free liquid accelerator comprises the following raw material components in parts by mass: 440-460 parts of aluminum sulfate, 110-130 parts of magnesium sulfate, 10-13 parts of sodium metaaluminate, 1-4 parts of sodium fluoride, 10-15 parts of nano silicon dioxide, 50-70 parts of diethanolamine oxalate, 8-13 parts of triethanolamine and 300-350 parts of water. Wherein all raw materials are analytical purity, water level distilled water.
The introduction of sulfate ions has great benefits on the workability of fresh concrete and the mechanical properties, durability and the like of hardened concrete, but the introduction of excessive sulfate ions can cause secondary ettringite to be generated in the concrete, so that the concrete cracks. In this example, the addition of suitable aluminum sulfate resulted in the formation of an alkali-free accelerator having good mechanical properties and durability without the formation of secondary ettringite.
Further, the solubility of aluminum sulfate is limited, and due to the relatively high content of sulfate radicals, aluminum ions can be hydrolyzed and coagulated in an aqueous solution, so that the phenomena of crystallization and precipitation and unstable storage quality are easily caused, and the normal use of the accelerator is influenced. In the embodiment, the stabilizer diethanolamine oxalate is added to form a stable complex with active aluminum ions in the solution, so that the instability is prevented from generating aluminum hydroxide precipitation, and the storage stability of the alkali-free accelerator is improved.
Fluoride is a main accelerating component in the alkali-free liquid accelerator, influences the accelerating effect of the accelerator, and the higher the content of fluoride ions is, the shorter the setting time is. However, the fluoride ion is generally from hydrofluoric acid or fluorosilicic acid, which is a carcinogenic substance extremely harmful to the body, so that the use of a large amount of fluoride ion can cause the potential safety hazard of seriously affecting the health of construction personnel in the production and use process, and the pollution to the construction environment is easily caused; in addition, a large amount of fluoride ions may hinder the hydration of cement, resulting in low early 1-day strength of concrete. Therefore, the existing alkali-free liquid accelerator has high content of fluoride ions, so that potential safety hazards exist and the early strength is poor; or low fluoride ion content, resulting in long coagulation times that do not meet standards. In the embodiment, a stable complex can be further formed with active aluminum ions in the solution by adding a stabilizer diethanolamine oxalate and the auxiliary complexation of sodium fluoride, so that the content of the active aluminum ions in the solution is increased, and the coagulation promoting effect is good; by adopting the nano silicon dioxide to replace part of sodium fluoride, the early strength is improved on the premise of ensuring the strength in the middle and later periods. Therefore, the alkali-free liquid accelerator prepared by the invention has low content of fluorinion, good accelerating effect, short setting time, and high early strength and middle and later strength of concrete.
In the technical scheme provided by the invention, a stable complex can be formed with active aluminum ions in the solution by adding the stabilizer diethanolamine oxalate, so that the content of the active aluminum ions in the solution is improved, the coagulation accelerating effect is better, and aluminum hydroxide precipitation caused by instability can be prevented, thereby improving the storage stability of the alkali-free accelerator; the addition of sodium fluoride can play a role in auxiliary complexation, so that the coagulation promoting effect and the storage stability are further improved; by adopting the nano silicon dioxide to replace part of sodium fluoride, the early strength is improved on the premise of ensuring the strength in the middle and later periods. Namely, by designing the raw materials and the proportion thereof, the alkali-free accelerator has the advantages of low fluoride ion concentration, safety, environmental protection, stable storage quality, good accelerating effect, high early strength and middle and later strength of concrete, and meets the standard of alkali-free liquid accelerator for tunnel shotcrete published in 2021.
Further, in a preferred embodiment, in the alkali-free liquid accelerator, the mass parts of the raw materials are as follows: 450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 65 parts of diethanolamine oxalate, 10 parts of triethanolamine and 328.75 parts of water. The alkali-free liquid accelerator prepared according to the proportion has the best comprehensive performance.
In view of the above object, the present invention further provides a method for preparing the alkali-free liquid accelerator, which in one embodiment comprises the following steps:
step S10, dissolving magnesium sulfate in water to obtain a mixed solution;
in this embodiment, magnesium sulfate is dissolved in water to obtain a mixed solution, so that all the raw materials are dissolved conveniently and the dissolution rate is high.
The dissolution temperature is not limited, as long as the magnesium sulfate can be dissolved in water, generally, the higher the temperature is, the faster the dissolution rate is, but the higher the temperature is, the higher the requirement on production equipment is, in this embodiment, the dissolution temperature is 60-80 ℃, so that the dissolution rate is higher, the requirement on production equipment is lower, the energy consumption is less, and the cost is saved.
Step S20, dissolving sodium fluoride, sodium metaaluminate, aluminum sulfate, triethanolamine and nano silicon dioxide in the mixed solution to obtain a first solution;
in order to make the dissolution rate of the raw materials faster and to make the raw materials not easily react with each other to cause foaming and splashing of the solution, in the present embodiment, the step S20 includes:
step S21, adding nano silicon dioxide into triethanolamine at the temperature of 60-80 ℃, and stirring for 0.5-1 h to obtain a milky mixture;
it is understood that the above operation is carried out at 60-80 deg.C, also for the purpose of cost and dissolution rate. The nanometer silicon dioxide is difficult to dissolve and disperse, in the embodiment, the nanometer silicon dioxide is added into triethanolamine and stirred for 0.5-1 h, so that the nanometer silicon dioxide is dispersed in the triethanolamine, and the nanometer silicon dioxide is convenient to dissolve and disperse with other raw materials subsequently.
And step S22, sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, then adding aluminum sulfate, stirring until the solution becomes transparent, then adding the milky mixture, and stirring for 20-40 min to obtain a first solution.
Wherein, the solution can be transparent after adding aluminum sulfate and stirring for 15-25 min.
And step S30, adding diethanolamine oxalate into the first solution for complex reaction to obtain the alkali-free liquid accelerator.
In the embodiment, after the complexing reaction is carried out for 25-40 min, the reaction is completed to obtain the alkali-free liquid accelerator.
The invention is not limited to the specific source of the diethanol oxalate, and in this example, the diethanol oxalate was prepared by the following steps:
step A1, dripping oxalic acid into diethanol amine under the stirring state to obtain an intermediate solution;
and A2, adding concentrated sulfuric acid into the intermediate solution, and reacting at 80-90 ℃ for 1-2 h to obtain diethanolamine oxalate.
Wherein the mass ratio of the oxalic acid to the diethanolamine to the concentrated sulfuric acid is 40-50: 10-15: 1 to 4.
It is understood that steps a1, a2 precede step S30. It should be noted that the present invention does not limit the relationship between steps a1 and a2 and steps S10 and S20, and may be before step S10, between step S10 and step S20, or after step S20.
The technical solutions of the present invention are further described in detail with reference to the following specific examples, which should be understood as merely illustrative and not limitative.
Example 1
The liquid alkali-free accelerator comprises the following raw material components in parts by mass: 450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 65 parts of diethanolamine oxalate, 10 parts of triethanolamine and 328.75 parts of water.
Example 2
The alkali-free liquid accelerator comprises the following raw material components in parts by mass: 450 parts of aluminum sulfate, 110 parts of magnesium sulfate, 13 parts of sodium metaaluminate, 1 part of sodium fluoride, 15 parts of nano silicon dioxide, 60 parts of diethanolamine oxalate, 8 parts of triethanolamine and 335 parts of water.
Example 3
The alkali-free liquid accelerator comprises the following raw material components in parts by mass: 440 parts of aluminum sulfate, 130 parts of magnesium sulfate, 10 parts of sodium metaaluminate, 4 parts of sodium fluoride, 10 parts of nano silicon dioxide, 50 parts of diethanolamine oxalate, 13 parts of triethanolamine and 300 parts of water.
Example 4
The alkali-free liquid accelerator comprises the following raw material components in parts by mass: 460 parts of aluminum sulfate, 115 parts of magnesium sulfate, 12 parts of sodium metaaluminate, 2 parts of sodium fluoride, 13 parts of nano silicon dioxide, 70 parts of diethanolamine oxalate, 10 parts of triethanolamine and 350 parts of water.
Example 5
(1) The formulation of the alkali-free liquid accelerator was the same as in example 1;
(2) adding water and magnesium sulfate into a reaction kettle at 70 ℃, and stirring to dissolve the magnesium sulfate in the water to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 70 ℃, and stirring for 0.7h to obtain a milky mixture; and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 30min to obtain a first solution.
(4) Adding diethanolamine into a four-neck flask with a temperature control and magnetic stirrer, slowly dripping oxalic acid by a dropping funnel at normal temperature while stirring to obtain an intermediate solution, adding concentrated sulfuric acid into the intermediate solution, and reacting at 85 ℃ for 1.5 hours to obtain diethanolamine oxalate; wherein, the mass ratio of oxalic acid, diethanolamine and concentrated sulfuric acid is 50: 15: 2;
(5) and adding diethanolamine oxalate into the first solution to perform a complex reaction for 30min to obtain the alkali-free liquid accelerator.
Example 6
(1) The formulation of the alkali-free liquid accelerator was the same as in example 2;
(2) adding water and magnesium sulfate into a reaction kettle at 60 ℃, and stirring to dissolve the magnesium sulfate in the water to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 60 ℃, and stirring for 0.5h to obtain a milky mixture; and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 20min to obtain a first solution.
(4) Adding diethanolamine into a four-neck flask with a temperature control and magnetic stirrer, slowly dripping oxalic acid by a dropping funnel at normal temperature while stirring to obtain an intermediate solution, adding concentrated sulfuric acid into the intermediate solution, and reacting at 90 ℃ for 1h to obtain diethanolamine oxalate; wherein, the mass ratio of oxalic acid, diethanolamine and concentrated sulfuric acid is 40: 10: 1;
(5) and adding diethanolamine oxalate into the first solution for a complexing reaction to obtain the alkali-free liquid accelerator.
Example 7
(1) The formulation of the alkali-free liquid accelerator was the same as in example 3;
(2) adding water and magnesium sulfate into a reaction kettle at 80 ℃, and stirring to dissolve the magnesium sulfate in the water to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 80 ℃, and stirring for 1h to obtain a milky mixture; and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 40min to obtain a first solution.
(4) Adding diethanolamine into a four-neck flask with a temperature control and magnetic stirrer, slowly dripping oxalic acid by a dropping funnel at normal temperature while stirring to obtain an intermediate solution, adding concentrated sulfuric acid into the intermediate solution, and reacting at 80 ℃ for 2 hours to obtain diethanolamine oxalate; wherein, the mass ratio of oxalic acid, diethanolamine and concentrated sulfuric acid is 45: 12: 4;
(5) and adding diethanolamine oxalate into the first solution to perform a complex reaction for 25min to obtain the alkali-free liquid accelerator.
Example 8
(1) The formulation of the alkali-free liquid accelerator was the same as in example 4;
(2) adding water and magnesium sulfate into a reaction kettle at 75 ℃, and stirring to dissolve the magnesium sulfate in the water to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 75 ℃, and stirring for 0.6h to obtain a milky mixture; and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 35min to obtain a first solution.
(4) Adding diethanolamine into a four-neck flask with a temperature control and magnetic stirrer, slowly dripping oxalic acid by a dropping funnel at normal temperature while stirring to obtain an intermediate solution, adding concentrated sulfuric acid into the intermediate solution, and reacting at 82 ℃ for 1.6 hours to obtain diethanolamine oxalate; wherein, the mass ratio of oxalic acid, diethanolamine and concentrated sulfuric acid is 45: 10: 3;
(5) and adding diethanolamine oxalate into the first solution to perform a complexing reaction for 40min to obtain the alkali-free liquid accelerator.
Comparative example 1
The alkali-free liquid accelerator comprises the following raw material components in parts by mass: 400 parts of aluminum sulfate, 54 parts of magnesium sulfate, 9.75 parts of sodium metaaluminate, 30 parts of magnesium fluosilicate, 11.5 parts of nano silicon dioxide, 50 parts of diethanolamine, 10 parts of triethanolamine and 434.75 parts of water.
Comparative example 2
The liquid alkali-free accelerator comprises the following raw material components in parts by mass: 450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 50 parts of diethanolamine, 10 parts of triethanolamine and 343.75 parts of water.
Comparative example 3
The liquid alkali-free accelerator comprises the following raw material components in parts by mass: 450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 65 parts of diethanolamine, 10 parts of triethanolamine, 15 parts of oxalic acid and 328.75 parts of water.
Comparative example 4
(1) The formula of the alkali-free liquid accelerator is the same as that of comparative example 1;
(2) adding water and magnesium fluosilicate into a reaction kettle at 70 ℃, stirring to dissolve the magnesium fluosilicate into the water, keeping the temperature of 70 ℃ after the magnesium fluosilicate is completely dissolved, sequentially adding aluminum sulfate and magnesium sulfate into the reaction kettle, and uniformly mixing to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 70 ℃, and stirring for 0.6h to obtain a milky mixture;
(4) and adding the milky mixture into the mixed solution, stirring for 0.5h to completely dissolve the milky mixture, and then adding a stabilizing agent diethanolamine to perform a complexing reaction for 30min to obtain the alkali-free liquid accelerator.
Comparative example 5
(1) The formula of the alkali-free liquid accelerator is the same as that of comparative example 2;
(2) adding water and magnesium sulfate into a reaction kettle at 70 ℃, stirring to dissolve the magnesium sulfate in the water, keeping the temperature of 70 ℃ after the magnesium sulfate is completely dissolved, sequentially adding sodium fluoride and sodium metaaluminate into the reaction kettle, uniformly mixing, then adding aluminum sulfate into the reaction kettle, and stirring for 20min to dissolve the aluminum sulfate to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 70 ℃, and stirring for 0.5h to obtain a milky mixture;
(4) and adding the milky mixture into the mixed solution, stirring for 0.5h to completely dissolve the milky mixture, and then adding a stabilizing agent diethanolamine to perform a complexing reaction for 30min to obtain the alkali-free liquid accelerator.
Comparative example 6
(1) The formula of the alkali-free liquid accelerator is the same as that of comparative example 3;
(2) adding water and magnesium sulfate into a reaction kettle at 70 ℃, stirring to dissolve the magnesium sulfate in the water, keeping the temperature of 70 ℃ after the magnesium sulfate is completely dissolved, sequentially adding sodium fluoride, sodium metaaluminate and oxalic acid into the reaction kettle, uniformly mixing, then adding aluminum sulfate into the reaction kettle, and stirring for 20min to dissolve the aluminum sulfate to obtain a mixed solution;
(3) adding nano silicon dioxide into triethanolamine at 70 ℃, and stirring for 0.5h to obtain a milky mixture;
(4) and adding the milky mixture into the mixed solution, stirring for 0.5h to completely dissolve the milky mixture, and then adding a stabilizing agent diethanolamine to perform a complexing reaction for 30min to obtain the alkali-free liquid accelerator.
The alkali-free liquid accelerators obtained in examples 5 to 8 and comparative examples 4 to 6 were subjected to a performance test by the following method: the experimental sample is used for preparing a cement paste sample by using an NJ-160 type cement paste stirrer; measuring the initial setting time and the final setting time of the material by using a cement consistency setting time measuring instrument; preparing a mortar sample with the size of 40mm multiplied by 160mm by adopting a JJ-5 type mortar stirrer and a ZS-15 type mortar vibrating table, and putting the mortar sample into a YH-40B cement constant-temperature constant-humidity standard curing box for curing; the compressive strength of the material is measured by utilizing a DYW-300S type computer full-automatic cement bending and compression resistant integrated machine. The measurement is carried out according to the GB/T35159-2017 accelerator for sprayed concrete and the new national iron standard QCR807-2020 accelerator for alkali-free liquid for tunnel sprayed concrete, and the results are shown in the following table 1; the results of the performance tests of the examples (the average values of examples 5 to 8) and the results of the performance test of the alkali-free liquid accelerator commercially available on the market were compared with the standard "alkali-free liquid accelerator for tunnel shotcrete" issued by the national railroad group in china in 2021, and the results are shown in Table 2 below.
Table 1 results of performance testing
TABLE 2 comparison of Performance
It can be seen from the combination of table 1 and table 2 that the alkali-free liquid accelerator prepared by the embodiment of the invention meets the standard of alkali-free liquid accelerator for tunnel shotcrete published by the national railway group of China in 2021, and compared with the similar alkali-free liquid accelerator on the market, the alkali-free liquid accelerator has the advantages of shorter initial setting time and final setting time, large compressive strength after 6 hours and 1 day, higher compressive strength retention rate after 28 days and 98 days, and better stability.
It can be understood that the basic liquid-free setting accelerator prepared by the method of examples 6 to 8 has almost the same performance as that of example 5, meets the standard of basic liquid-free setting accelerator for tunnel shotcrete, and has better comprehensive performance than similar products in the market.
The setting time and the compressive strength of the alkali-free liquid accelerator prepared in the comparative example 4 do not reach the standards; comparative example 5 on the basis of comparative example 4, the addition amounts of aluminum sulfate and nano-silica are increased, and sodium fluoride is used for replacing magnesium fluosilicate, so that the setting time and the early compressive strength are promoted to a certain extent, the setting time of the prepared alkali-free liquid accelerator meets the standard, but the compressive strength of 6h is less than 1 MPa, the alkali-free liquid accelerator does not meet the standard requirement, and the alkali-free liquid accelerator is unstable in storage; comparative example 6 the use of oxalic acid and diethanolamine is increased on the basis of comparative example 5, the early strength is promoted, the setting time and compressive strength of the prepared alkali-free accelerator both meet the standard, but the supersaturated aluminum sulfate solution is easy to destabilize to generate aluminum hydroxide precipitate, so that the accelerator is unstable to store and is easy to separate out.
In conclusion, by designing the formula of the alkali-free liquid accelerator, the prepared alkali-free liquid accelerator has low fluoride ion and alkali ion concentration, good accelerating effect, high early strength, high middle and later strength and stable storage quality, thereby meeting the standard of alkali-free liquid accelerator for tunnel sprayed concrete, having better comprehensive performance than similar products on the market at present and having obvious competitive advantage.
The above is only a preferred embodiment of the present invention, and it is not intended to limit the scope of the invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention shall be included in the scope of the present invention.
Claims (8)
1. The alkali-free liquid accelerator is characterized by comprising the following raw material components in parts by mass:
440-460 parts of aluminum sulfate, 110-130 parts of magnesium sulfate, 10-13 parts of sodium metaaluminate, 1-4 parts of sodium fluoride, 10-15 parts of nano silicon dioxide, 50-70 parts of diethanolamine oxalate, 8-13 parts of triethanolamine and 300-350 parts of water.
2. The alkali-free liquid accelerator according to claim 1, wherein the alkali-free liquid accelerator comprises the following raw materials in parts by mass:
450 parts of aluminum sulfate, 120 parts of magnesium sulfate, 11.25 parts of sodium metaaluminate, 2.25 parts of sodium fluoride, 12.75 parts of nano silicon dioxide, 65 parts of diethanolamine oxalate, 10 parts of triethanolamine and 328.75 parts of water.
3. A method for producing the alkali-free liquid accelerator according to claim 1 or 2, comprising the steps of:
s10, dissolving magnesium sulfate in water to obtain a mixed solution;
s20, dissolving sodium fluoride, sodium metaaluminate, aluminum sulfate, triethanolamine and nano silicon dioxide in the mixed solution to obtain a first solution;
and S30, adding diethanolamine oxalate into the first solution for a complexing reaction to obtain the alkali-free liquid accelerator.
4. The method for producing the alkali-free liquid accelerator according to claim 3, wherein in step S10, the dissolution temperature for the dissolution is 60 to 80 ℃.
5. The method for preparing an alkali-free liquid accelerator as claimed in claim 3, wherein the step S20 comprises:
adding nano silicon dioxide into triethanolamine at the temperature of 60-80 ℃, and stirring for 0.5-1 h to obtain a milky mixture;
and sequentially adding sodium fluoride and sodium metaaluminate into the mixed solution, uniformly mixing, adding aluminum sulfate, stirring until the solution becomes transparent, adding the milky mixture, and stirring for 20-40 min to obtain a first solution.
6. The method for preparing an alkali-free liquid accelerator as claimed in claim 3, further comprising, before step S30, the steps of:
under the stirring state, dripping oxalic acid into diethanol amine to obtain an intermediate solution;
and adding concentrated sulfuric acid into the intermediate solution, and reacting at 80-90 ℃ for 1-2 h to obtain diethanolamine oxalate.
7. The preparation method of the alkali-free liquid accelerator according to claim 6, wherein the mass ratio of the oxalic acid to the diethanolamine to the concentrated sulfuric acid is 40-50: 10-15: 1 to 4.
8. The method for preparing the alkali-free liquid accelerator according to claim 3, wherein in step S30, the time of the complexation reaction is 20-40 min.
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| CN115572099A (en) * | 2022-10-25 | 2023-01-06 | 中铁十一局集团有限公司 | Normal-temperature preparation method of alkali-free liquid accelerator for quick-hardening early-strength sprayed concrete |
| CN115872662A (en) * | 2022-06-16 | 2023-03-31 | 桂林理工大学 | Liquid alkali-free accelerator for sprayed concrete and preparation method thereof |
| CN117361927A (en) * | 2023-10-30 | 2024-01-09 | 石家庄市长安育才建材有限公司 | Dry and wet spray concrete dual-purpose alkali-free accelerator and preparation method and application thereof |
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| CN117361927A (en) * | 2023-10-30 | 2024-01-09 | 石家庄市长安育才建材有限公司 | Dry and wet spray concrete dual-purpose alkali-free accelerator and preparation method and application thereof |
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