Staged delayed coagulation and viscosity reduction type aluminoferrite cement water reducing agent and preparation method thereof

Abstract

The invention discloses a staged delayed coagulation and viscosity reduction type iron aluminate cement water reducing agent and a preparation method thereof. The iron aluminate cement water reducing agent is obtained by copolymerizing prepared isopentenol polyoxyethylene ether borate, hydroxyethyl methylacrylate glucolactone and methacrylic acid. The boric acid ester is rapidly hydrolyzed in the initial stage of hydration (9 < pH < 12) to obtain boric acid, and first-stage delayed coagulation is performed on the aluminoferrite cement. When delayed coagulation fails, the cement continues to be hydrated to reach the middle stage of hydration (pH > 12), glucolactone is hydrolyzed to generate gluconate for further delayed coagulation of the cement, meanwhile, hydroxyethyl methylacrylate is hydrolyzed to release more adsorption sites, and hydration products are further dispersed to reduce the viscosity of the system. And stage release enables the aluminoferrite cement to be hydrated stage by stage, so that the problem of poor bleeding cohesiveness caused by non-hydration of the cement after one-time doping of the retarder is solved, the problem of slurry tackifying caused by large hydration of the cement in the later stage is also avoided, and engineering application of the aluminoferrite cement is further promoted.

Description

Technical Field

[0001] The present invention relates to the technical field of water reducers, and in particular to a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer and a preparation method thereof. Background Art

[0002] Ferroaluminate cement, with its excellent properties such as early strength, corrosion resistance, and freeze-thaw resistance, has become the preferred cementitious material for harsh environments such as marine engineering and nuclear power facilities. However, its rapid hydration reaction rate results in a short setting time (initial setting time is usually less than 30 minutes) and high viscosity (due to the rapid formation rate of hydration products), which seriously restricts the fluidity and workability of large-scale construction. Current research on ferroaluminate cement admixtures still faces the following problems in terms of retarding setting and concrete workability:

[0003] (1) Insufficient adaptability of retarder

[0004] ① In the process of preparing concrete with ferroaluminate cement, a sufficient amount of retarder is usually added at one time to slow down the setting and achieve workability. Although this operation can prolong the setting time, the addition of a sufficient amount of retarder makes the ferroaluminate cement basically unhydrated in the early stage. This leads to problems such as water seepage and poor cohesion in the concrete during use, and may even destroy the structure of the hydration product of ferroaluminate cement, reducing the corrosion resistance and impermeability of ferroaluminate cement.

[0005] ② Since polycarboxylate water-reducing agents achieve dispersion by adsorbing cement particles, most retarders, especially organic retarders, also achieve retarding effect by adsorbing cement particles. When both are added to cement at the same time, they compete for the adsorption sites on the surface of cement particles, which on the one hand weakens the water-reducing effect and on the other hand may cause fluctuations in the retarding effect.

[0006] (2) Centralized hydration leads to increased slurry viscosity

[0007] When the retarder fails, the anhydrous calcium sulfoaluminate in the ferroaluminate cement begins to hydrate rapidly and centrally, generating a large amount of ettringite hydration products with a large specific surface area. At this time, there are not enough carboxyl groups to adsorb and disperse them, resulting in a significant increase in the viscosity of the slurry and reduced workability.

[0008] Currently, there are many patents for retarding water reducers, but most of them target only Portland cement systems. Many of these patents achieve a certain degree of retarding effect through slow release or increased steric hindrance. For example, Chinese invention patent application CN119859226A discloses a super-retarding ester polycarboxylate water reducer and its preparation method. This super-retarding ester polycarboxylate water reducer incorporates a slow-release group and a large sterically hindered benzene ring into its side chain. By slowly releasing the adsorbed group, it provides a long-lasting slump-retaining effect. However, for ferroaluminate cement, which has a relatively fast hydration rate, this retarding effect is minimal.

[0009] In summary, ferroaluminate cement is favored in many engineering fields due to its excellent properties such as early strength, corrosion resistance, and freeze-thaw resistance. However, compared with ordinary Portland cement concrete, it still has many problems in the process of preparing concrete, such as fast setting time and poor operability. If a multifunctional water reducer can be prepared to better solve these problems, it will definitely promote the development of ferroaluminate cement. Summary of the Invention

[0010] 1. Technical problems to be solved:

[0011] In response to the above technical problems, the present invention provides a staged retarding and viscosity-reducing ferroaluminate cement water reducer and a preparation method thereof. The water reducer prepared thereby mainly solves the problems of water seepage and poor cohesion caused by the first retarding of the setting in the current ferroaluminate cement concrete, as well as the problem of high viscosity caused by the concentrated hydration in the later stage.

[0012] 2. Technical solution:

[0013] A staged slow-setting and viscosity-reducing ferroaluminate cement water reducer, characterized in that the structure of the water reducer is as follows:

[0014]

[0015] In the above formula, a is an integer from 21 to 35; b is an integer from 20 to 34; c is an integer from 6 to 10; and n is 53.

[0016] A method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer comprises the following steps:

[0017] Step 1: Under nitrogen protection, hydroxyethyl methacrylate, gluconolactone, hydroquinone, and anhydrous tetrahydrofuran are added to a round-bottom flask and stirred evenly, followed by addition of p-toluenesulfonic acid and heating for reaction; after the reaction is completed, the mixture is cooled, extracted with ethyl acetate and deionized water, the organic phases are combined, and the solvent is removed by rotary evaporation under reduced pressure at 40°C. The crude product is purified by column chromatography to obtain the target product hydroxyethyl methacrylate gluconolactone of the formula below; the column chromatography purification is performed using an eluent solution having an ethyl acetate / petroleum ether concentration of 10-25% for purification;

[0018]

[0019] Step 2: Under nitrogen protection, boric acid, ethylene glycol, p-toluenesulfonic acid and anhydrous toluene are added to a dry reaction flask, and water is continuously removed through a water separator and heated under reflux for reaction; after the reaction is completed, the mixture is cooled, washed with a small amount of anhydrous ether and filtered, and the resulting solid is dried under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol; under nitrogen protection, cyclic boric acid ethylene glycol, isopentanol polyoxyethylene ether, sodium hydride and anhydrous tetrahydrofuran are added to the dry reaction flask, and the temperature is raised for reaction; after the reaction is completed, the mixture is extracted with ethyl acetate and deionized water, and the organic phase is concentrated under reduced pressure to obtain the product isopentanol polyoxyethylene ether borate of the following formula;

[0020]

[0021] Step 3: Add isopentanol polyoxyethylene ether borate, an oxidant and an appropriate amount of deionized water into a three-necked flask with a stirrer and mix them evenly; at the same time, slowly dropwise add an aqueous solution of a reducing agent and an aqueous solution consisting of methacrylic acid, hydroxyethyl methacrylate gluconolactone and a chain transfer agent. After the reaction is completed, a ferroaluminate cement water reducer is obtained.

[0022] Furthermore, in step 1, the molar ratio of hydroxyethyl methacrylate, gluconolactone, anhydrous tetrahydrofuran and p-toluenesulfonic acid is: 1:1.05:(9.87-12.3):(0.005-0.01); and the content of hydroquinone is 0.1-0.2 wt.% of the hydroxyethyl methacrylate.

[0023] Furthermore, in step 2, the molar ratio of the boric acid, ethylene glycol, p-toluenesulfonic acid and anhydrous toluene is: 1.0:1.05:(0.01-0.02):(9.41-14.12); the reaction molar ratio of the cyclic boric acid ethylene glycol, isopentanol polyoxyethylene ether, sodium hydride and anhydrous tetrahydrofuran is: 1.0:1.0:(1.3-1.5):(9.87-12.35).

[0024] Furthermore, in step three, the oxidant is one of ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one of sodium bisulfite, sodium sulfite, bleaching agent, ascorbic acid, sodium ascorbate, and isoascorbic acid; and the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecanol, and sodium hypophosphite.

[0025] Furthermore, in step three, the molar ratio of prenol polyoxyethylene ether borate, oxidant, reducing agent, methacrylic acid, hydroxyethyl methacrylate gluconolactone, and chain transfer agent is: 1:(0.07-0.12):0.2:(3-4.2):(2.5-3.5):(0.03-0.05).

[0026] Furthermore, in step three, the molecular weight of the ferroaluminate cement water reducer finally obtained is 23000 to 37400 g / mol.

[0027] Furthermore, the reaction temperature in step 1 is 60-70° C., and the reaction time is 4-6 hours.

[0028] Furthermore, in step 2, the reaction temperature of the former reaction is 110° C. to 120° C., and the reaction time is 6 to 8 hours; the reaction temperature of the latter reaction is 60° C. to 70° C., and the reaction time is 8 to 12 hours.

[0029] Furthermore, in step 3, the reaction temperature is 25-35°C, the dropwise addition time is 3 hours, and the heat preservation time is 1 hour. 3. Beneficial effects:

[0030] This method is aimed at ferroaluminate cement, which is a fast-hardening and early-strengthening cement. If it is used in concrete like silicate cement, its retarding problem must be designed. According to existing experience, a sufficient amount of retarder is usually added to concrete at one time to make its setting time meet the actual use requirements. However, the one-time retarding makes the cement basically not hydrated in the early stage, which makes the concrete easy to bleed water and lack cohesion in the early stage. However, when the retarder loses its effectiveness, the cement hydrates rapidly and concentratedly, which in turn leads to an increase in the viscosity of the concrete, a decrease in workability, and a concentrated release of hydration heat, which poses risks such as cracking in the later stage for large-volume concrete.

[0031] The ferroaluminate cement water reducer prepared by the present invention is formed by copolymerizing isopentanol polyoxyethylene ether borate, hydroxyethyl methacrylate gluconolactone and methacrylic acid. When added to cement, the retarder will be released in stages according to the cement hydration process. In the early stage of cement hydration (9<pH<12), the borate first hydrolyzes to release boric acid, which performs the first stage of retarding effect on the ferroaluminate cement. When the first stage of retarding fails, the cement hydration enters the middle and late stages (pH>12), and gluconolactone and hydroxyethyl ester begin to hydrolyze to release gluconate and carboxyl groups, thereby performing the second stage of retarding effect on the cement. The released carboxyl groups better disperse the generated hydration products, thereby achieving the effect of reducing viscosity. Compared with the one-time addition of retarder, this staged retarding allows the ferroaluminate cement to achieve staged hydration, avoiding the problems of water bleeding and poor workability caused by the basic lack of hydration in the early stage. At the same time, during the peak period of the generation of ettringite hydration products in the middle and late stages, sufficient carboxyl groups are released to simultaneously adsorb and disperse them, thereby achieving the purpose of reducing the viscosity of the slurry in the middle and late stages. DETAILED DESCRIPTION

[0032] The present invention will be described in detail below with reference to specific embodiments. The described embodiments are only some embodiments of the present invention, but not all embodiments.

[0033] Unless otherwise specified, the experimental materials and reagents used in the following examples can be obtained from commercial sources. It should be noted that a comparative example is used in this specific example for comparison with the present application. The comparative example is a conventional polycarboxylate water-reducing agent structure. It has been verified that it also has a dispersing effect in ferroaluminate cement, but it does not have a retarding and viscosity-reducing effect. Therefore, it is used for comparison to characterize whether the water-reducing agent designed by us has a retarding and viscosity-reducing effect.

[0034] Example 1

[0035] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.13 g of hydroquinone, and 800 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 0.86 g of p-toluenesulfonic acid was then added, and the temperature was raised to 60°C for 6 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0036] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 1.72 g of p-toluenesulfonic acid and 1000 mL of anhydrous toluene to a dry reaction flask, heat to 110°C and reflux, remove water continuously through a water separator, and react for 8 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and dry the obtained solid under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.3 mol of sodium hydride and 800 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 60°C and stir to react for 12 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0037] Step S03: Add 1 mol of prenol polyoxyethylene ether borate, 0.07 mol of ammonium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add dropwise a 0.2 mol aqueous solution of ascorbic acid and an aqueous solution consisting of 3 mol of methacrylic acid, 2.5 mol of hydroxyethyl methacrylate gluconolactone, and 0.05 mol of thioglycolic acid at 25°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 27,400 g / mol, and the molecular structure is as follows:

[0038]

[0039] Example 2

[0040] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.19 g of hydroquinone, and 900 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 1.29 g of p-toluenesulfonic acid was then added, and the temperature was raised to 65°C for 5 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0041] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 2.58 g of p-toluenesulfonic acid and 1300 mL of anhydrous toluene to a dry reaction flask, heat to 115°C and reflux, remove water continuously through a water separator, and react for 7 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and dry the obtained solid under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.4 mol of sodium hydride and 900 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 65°C and stir to react for 10 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0042] Step S03: Add 1 mol of prenol polyoxyethylene ether borate, 0.09 mol of sodium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add 0.2 mol of an aqueous sodium bisulfite solution and an aqueous solution consisting of 3.6 mol of methacrylic acid, 3.0 mol of hydroxyethyl methacrylate gluconolactone, and 0.05 mol of sodium methyl propylene sulfonate at 25°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 25,400 g / mol, and the molecular structure is as follows:

[0043]

[0044] Example 3

[0045] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.26 g of hydroquinone, and 1000 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 1.72 g of p-toluenesulfonic acid was then added, and the temperature was raised to 70°C for 4 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0046] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 3.44 g of p-toluenesulfonic acid and 1500 mL of anhydrous toluene to a dry reaction flask, heat to 120°C and reflux, remove water continuously through a water separator, and react for 6 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and the resulting solid is dried under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.5 mol of sodium hydride and 1000 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 70°C and stir to react for 8 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0047] Step S03: Add 1 mol of isopentanol polyoxyethylene ether borate, 0.12 mol of potassium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix well. At 25°C, slowly add 0.2 mol of a solution of bleaching powder and an aqueous solution consisting of 4.2 mol of methacrylic acid, 3.5 mol of hydroxyethyl methacrylate gluconolactone, and 0.05 mol of 2-mercaptopropionic acid. The addition time is controlled to be 3 hours. After the addition is completed, the heat is maintained for 1 hour. After the reaction is completed, a ferroaluminate cement water reducer is obtained. The final molecular weight is 23,000 g / mol, and the molecular structure is as follows:

[0048]

[0049] Example 4

[0050] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.13 g of hydroquinone, and 800 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 0.86 g of p-toluenesulfonic acid was then added, and the temperature was raised to 60°C for 6 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0051] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 1.72 g of p-toluenesulfonic acid and 1000 mL of anhydrous toluene to a dry reaction flask, heat to 110°C and reflux, remove water continuously through a water separator, and react for 8 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and dry the obtained solid under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.3 mol of sodium hydride and 800 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 60°C and stir to react for 12 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0052] Step S03: Add 1 mol of prenol polyoxyethylene ether borate, 0.07 mol of ammonium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add dropwise a 0.2 mol aqueous solution of ascorbic acid and an aqueous solution consisting of 3 mol of methacrylic acid, 3.5 mol of hydroxyethyl methacrylate gluconolactone, and 0.05 mol of dodecanethiol at 25°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 26,000 g / mol, and the molecular structure is as follows:

[0053]

[0054] Example 5

[0055] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.19 g of hydroquinone, and 900 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 1.29 g of p-toluenesulfonic acid was then added, and the temperature was raised to 65°C for 5 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0056] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 2.58 g of p-toluenesulfonic acid and 1300 mL of anhydrous toluene to a dry reaction flask, heat to 115°C and reflux, remove water continuously through a water separator, and react for 7 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and dry the obtained solid under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.4 mol of sodium hydride and 900 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 65°C and stir to react for 10 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0057] Step S03: Add 1 mol of prenol polyoxyethylene ether borate, 0.09 mol of potassium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add dropwise 0.2 mol of ascorbic acid aqueous solution and an aqueous solution consisting of 3.6 mol of methacrylic acid, 3.5 mol of hydroxyethyl methacrylate gluconolactone, and 0.05 mol of sodium hypophosphite at 25°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 23,100 g / mol, and the molecular structure is as follows:

[0058]

[0059] Example 6

[0060] Step S01: Under nitrogen, 1 mol of hydroxyethyl methacrylate, 1.05 mol of gluconolactone, 0.26 g of hydroquinone, and 1000 mL of anhydrous tetrahydrofuran were added to a round-bottom flask and stirred uniformly. 1.72 g of p-toluenesulfonic acid was then added, and the temperature was raised to 70°C for 4 hours. After the reaction, the mixture was cooled and extracted with ethyl acetate and deionized water. The organic phases were combined and the solvent was removed by rotary evaporation (40°C under reduced pressure). The crude product was purified by column chromatography to obtain the target product, hydroxyethyl methacrylate gluconolactone. The column chromatography purification was performed using an eluent solution with an ethyl acetate / petroleum ether concentration of 10-25%.

[0061] Step S02: (1) Under nitrogen protection, add 1 mol of boric acid, 1.05 mol of ethylene glycol, 3.44 g of p-toluenesulfonic acid and 1500 mL of anhydrous toluene to a dry reaction flask, heat to 120°C and reflux, remove water continuously through a water separator, and react for 6 hours. After the reaction is completed, cool, wash and filter with a small amount of anhydrous ether, and the resulting solid is dried under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol. (2) Under nitrogen protection, add 1 mol of cyclic boric acid ethylene glycol, 1.0 mol of isopentanol polyoxyethylene ether, 1.5 mol of sodium hydride and 1000 mL of anhydrous tetrahydrofuran to a dry reaction flask, heat to 70°C and stir to react for 8 hours. After the reaction is completed, extract with ethyl acetate and deionized water, and concentrate the organic phase under reduced pressure to obtain the product, isopentanol polyoxyethylene ether borate.

[0062] Step S03: Add 1 mol of prenol polyoxyethylene ether borate, 0.12 mol of sodium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add dropwise 0.2 mol of an aqueous solution of sodium ascorbate and an aqueous solution consisting of 3.6 mol of methacrylic acid, 3.5 mol of hydroxyethyl methacrylate gluconolactone, and 0.03 mol of 3-mercaptopropionic acid at 35°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 37,400 g / mol, and the molecular structure is as follows:

[0063]

[0064] Comparative Example 1

[0065] Step S01: Add 1 mol of prenol polyoxyethylene ether, 0.07 mol of ammonium persulfate, and an appropriate amount of deionized water to a three-necked flask with a stirrer and mix thoroughly. Simultaneously, slowly add 0.2 mol of sodium sulfite aqueous solution and an aqueous solution consisting of 3 mol of methacrylic acid and 0.05 mol of thioglycolic acid dropwise at 25°C for 3 hours. After the addition is complete, continue the reaction at this temperature for 1 hour. Upon completion of the reaction, a ferroaluminate cement water reducer is obtained. The final molecular weight is 34,500 g / mol, and the molecular structure is as follows:

[0066]

[0067] Test Case

[0068] 1. Determination of setting time

[0069] The setting time of the examples and comparative examples was measured with reference to GB / T1346-2011 "Test Methods for Water Consumption, Setting Time, and Soundness of Cement at Standard Consistency." The water-reducing agent dosage was fixed at 0.1% of the cement dosage. The experimental results are shown in Table 1.

[0070] Table 1 Effect of water reducer on setting time of ferroaluminate cement

[0071] sample Initial setting time / min Final setting time / min Example 1 143 178 Example 2 164 185 Example 3 194 229 Example 4 212 241 Example 5 174 198 Example 6 125 154 Comparative Example 1 29 42

[0072] The experimental results show that the water-reducing agent prepared by the present invention has a significant retarding effect compared to conventional water-reducing agents. Increasing the borate and gluconolactone content significantly prolongs the setting time of ferroaluminate cement. Therefore, it can be inferred that these two groups can be smoothly released in cement and exert a retarding effect, which is consistent with the expected results.

[0073] 2. Cement paste test

[0074] With reference to GB / T8077-2012 "Test Method for Homogeneity of Concrete Admixtures," the paste fluidity of the examples and comparative examples was tested, and the results are shown in Table 2. The water-cement ratio was 0.29, the water-reducing agent dosage was 0.1% of the cement dosage, and the initial fluidity, 0.5h fluidity, 1h fluidity, 1.5h fluidity, and 2h fluidity were tested.

[0075] Table 2 Fluidity and time loss of pure pulp

[0076]

[0077] From the above results, it can be seen that the water reducer prepared by the present invention has a better retention effect, and the retention time can be extended by 1-2 hours compared with the ordinary water reducer. It can also be observed that although the ordinary water reducer plus boric acid also has a good retention effect, it has serious water bleeding after 0.5 hours. Except for Example 3 which has a slight water bleeding, all other examples do not have water bleeding.

[0078] 3. Inverted slump cone emptying test

[0079] To compare the effects of the examples and comparative examples on the viscosity of ferroaluminate cement concrete, we prepared C45 strength grade concrete and measured its emptying time using the inverted slump cone emptying test method specified in GB / T 50080-2016, "Standard for Test Methods for Properties of Ordinary Concrete Mixtures." The results are shown in Table 3.

[0080] Table 3 Results of the concrete inverted slump cone emptying test

[0081]

[0082] The above results show that the initial emptying time is similar, but the 1-hour emptying time shows that the comparative example is significantly longer, while the example example's emptying time is significantly reduced. This is mainly because the retarder in the comparative example loses its effectiveness after about 1 hour, and the cement begins to rapidly hydrate. The comparative example does not have sufficient carboxyl groups to effectively disperse the hydration products, while the hydroxyethyl ester in the example begins to hydrolyze and release carboxyl groups at this time, dispersing the hydration products and significantly reducing the viscosity of the slurry.

[0083] Although the present invention has been disclosed above in terms of preferred embodiments, they are not intended to limit the present invention. Anyone skilled in the art can make various changes or modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection defined by the claims of this application.

Claims

1. A staged slow-setting and viscosity-reducing ferroaluminate cement water reducer, characterized by: The structure of the water reducer is as follows: In the above formula, a is an integer from 21 to 35; b is an integer from 20 to 34; c is an integer from 6 to 10; and n is 53.

2. A method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer, for preparing the water reducer according to claim 1, characterized in that: The following steps are involved: Step 1: Under nitrogen protection, hydroxyethyl methacrylate, gluconolactone, hydroquinone, and anhydrous tetrahydrofuran are added to a round-bottom flask and stirred evenly, followed by addition of p-toluenesulfonic acid and heating for reaction; after the reaction is completed, the mixture is cooled, extracted with ethyl acetate and deionized water, the organic phases are combined, and the solvent is removed by rotary evaporation under reduced pressure at 40°C. The crude product is purified by column chromatography to obtain the target product hydroxyethyl methacrylate gluconolactone of the formula below; the column chromatography purification is performed using an eluent solution having an ethyl acetate / petroleum ether concentration of 10-25% for purification; Step 2: Under nitrogen protection, boric acid, ethylene glycol, p-toluenesulfonic acid and anhydrous toluene are added to a dry reaction flask, and water is continuously removed through a water separator and heated under reflux for reaction; after the reaction is completed, the mixture is cooled, washed with a small amount of anhydrous ether and filtered, and the resulting solid is dried under reduced pressure to obtain a white solid product, cyclic boric acid ethylene glycol; under nitrogen protection, cyclic boric acid ethylene glycol, isopentanol polyoxyethylene ether, sodium hydride and anhydrous tetrahydrofuran are added to the dry reaction flask, and the temperature is raised for reaction; after the reaction is completed, the mixture is extracted with ethyl acetate and deionized water, and the organic phase is concentrated under reduced pressure to obtain the product isopentanol polyoxyethylene ether borate of the following formula; Step 3: Add isopentanol polyoxyethylene ether borate, an oxidant and an appropriate amount of deionized water into a three-necked flask with a stirrer and mix them evenly; at the same time, slowly dropwise add an aqueous solution of a reducing agent and an aqueous solution consisting of methacrylic acid, hydroxyethyl methacrylate gluconolactone and a chain transfer agent. After the reaction is completed, a ferroaluminate cement water reducer is obtained.

3. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step 1, the molar ratio of hydroxyethyl methacrylate, gluconolactone, anhydrous tetrahydrofuran and p-toluenesulfonic acid is: 1:1.05:(9.87-12.3):(0.005-0.01); and the content of hydroquinone is 0.1-0.2 wt.% of the hydroxyethyl methacrylate.

4. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, wherein: In step 2, the molar ratio of the boric acid, ethylene glycol, p-toluenesulfonic acid and anhydrous toluene is: 1.0:1.05:(0.01-0.02):(9.41-14.12); the reaction molar ratio of the cyclic boric acid ethylene glycol, isopentanol polyoxyethylene ether, sodium hydride and anhydrous tetrahydrofuran is: 1.0:1.0:(1.3-1.5):(9.87-12.35).

5. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step three, the oxidant is one of ammonium persulfate, sodium persulfate, and potassium persulfate; the reducing agent is one of sodium bisulfite, sodium sulfite, bleaching agent, ascorbic acid, sodium ascorbate, and isoascorbic acid; and the chain transfer agent is one of thioglycolic acid, 2-mercaptopropionic acid, 3-mercaptopropionic acid, sodium methyl propylene sulfonate, dodecyl mercaptan, and sodium hypophosphite.

6. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step 3, the molar ratio of prenol polyoxyethylene ether borate, oxidant, reducing agent, methacrylic acid, hydroxyethyl methacrylate gluconolactone, and chain transfer agent is: 1:(0.07-0.12):0.2:(3-4.2):(2.5-3.5):(0.03-0.05).

7. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step 3, the molecular weight of the ferroaluminate cement water reducer finally obtained is 23000 to 37400 g / mol.

8. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: The reaction temperature in step 1 is 60-70° C., and the reaction time is 4-6 hours.

9. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step 2, the reaction temperature of the former reaction is 110° C. to 120° C., and the reaction time is 6 to 8 hours; the reaction temperature of the latter reaction is 60° C. to 70° C., and the reaction time is 8 to 12 hours.

10. The method for preparing a staged slow-setting and viscosity-reducing ferroaluminate cement water reducer according to claim 2, characterized in that: In step 3, the reaction temperature is 25-35° C., the dropwise addition time is 3 hours, and the insulation time is 1 hour.

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