A slow-release high-alkali cement reinforcing agent, a preparation method and application thereof

Abstract

The application discloses a slow-release high-alkali cement reinforcing agent and a preparation method and application thereof, wherein thiocyano benzoic acid and polyol amine are mixed in a reaction kettle, stirring is carried out under nitrogen protection, and temperature is raised to 160-180 DEG C; a catalyst and a water-carrying agent are added, stirring is carried out, and temperature is raised to 180-200 DEG C; esterification reaction is carried out for 5-10 h; water generated in the reaction is separated during the reaction; the reaction is ended until no water is generated any more; unreacted materials are removed through purification treatment; and the slow-release high-alkali cement reinforcing agent is obtained. According to the hydration characteristics of high-alkali cement, the organic molecular structure designability is utilized, the high-alkali cement reinforcing agent which can efficiently promote the hydration of iron aluminate tetra calcium and simultaneously release and enhance is synthesized, the obtained product has low mixing amount, does not need to be compounded and can be directly used, and the strength of high-alkali cement, especially the later strength, is remarkably improved.

Description

Technical Field

[0001] This invention belongs to the field of materials technology, specifically relating to a high-alkali cement reinforcing agent, its preparation method, and its application. Background Technology

[0002] As the most widely used building material in the world today, the performance of silicate cement directly affects the quality and safety of engineering projects. Due to my country's vast territory, the composition of cement raw materials varies significantly across different regions, leading to the diversity and complexity of cement products. Cement clinker, the main raw material for cement, directly influences cement performance. The main mineral components of silicate cement clinker are tricalcium silicate, dicalcium silicate, tricalcium aluminate, and tetracalcium aluminoferrite, also containing small amounts of free calcium oxide, free magnesium oxide, alkaline oxides, and vitreous matter. Alkali (K₂O and Na₂O) content, as a quality indicator of cement products, is often expressed in the form of sodium equivalent (Na₂Oeq = Na₂O + 0.658K₂O). Its source is cement production raw materials and fuels, so alkali in cement products is unavoidable. Early hydration of silicate cement mainly involves the hydration of C₃S and C₃A, while the hydration activity of C₂S and C₄AF is lower, occurring later and contributing less to cement strength. The influence of alkali content on silicate cement hydration is mainly manifested in its impact on the hydration of C₃S and C₃A. Domestic and international scholars have conducted extensive research on the impact of alkali content in cement on its performance. They believe that alkali in any form—including alkali dissolved in clinker and alkali existing in a free state—significantly accelerates the hydration of C3S and C3A. This phenomenon is more pronounced when the alkali content in cement exceeds 0.8%, leading to high early-stage strength but insufficient later-stage strength development. Promoting the hydration of C4AF in high-alkali cement has become one way to improve its strength. Furthermore, improving the later-stage strength of high-alkali cement is also an urgent problem to be solved.

[0003] Currently, commonly used reinforcing materials in cement include alkanolamine organic compounds and inorganic salts containing chloride or thiocyanate. Alkanolamine organic compounds mainly work by complexing with Ca produced during cement hydration. 2+ Fe 3+ Al 3+ Plasma accelerates the dissolution rate of mineral phases in water, thereby promoting cement hydration and increasing cement strength. Inorganic salts containing chloride or thiocyanate primarily increase calcium content through electrolyte action. 2+ Fe 3+ Al 3+ Plasma solubility promotes cement hydration and increases cement strength. However, high-alkali cement itself has a faster early hydration rate, and the further promotion of hydration by ordinary cement reinforcing agents actually increases the harmful pores in cement hydration products, leading to a further decrease in the later strength of high-alkali cement.

[0004] Organic compounds possess significant advantages due to the designability of their molecular structures. Synthesizing high-alkali cement reinforcing agents through molecular structure design can address the aforementioned issues, enabling the diversification of reinforcing agent molecular structures and optimizing their performance. This would help overcome the current bottlenecks in high-alkali cement reinforcing technology; however, there are currently few reports on such technologies.

[0005] CN115448625 discloses a grinding aid for improving the performance of high-alkali cement. The components, by mass percentage, are as follows: 20%–40% nano-hydrated calcium silicate, 1%–3% organic phosphonic acid compound, 0.5%–2.5% tetracalcium aluminoferrite hydration accelerator, 9%–30% polyol amine ester, 0.1%–0.5% defoamer, and the remainder is water. Its preparation method is simple, and it exhibits excellent grinding aid effects. It can reduce the water requirement for the standard consistency of high-alkali cement, prolong the setting time, improve the fluidity of cement paste, reduce early hydration heat, reduce 28-day drying shrinkage, and significantly improve 28-day compressive strength, thus significantly improving the performance of high-alkali cement. It uses a poly-organic carboxylic acid compound as the tetracalcium aluminoferrite hydration accelerator, increasing the dissolution of iron ions, thereby promoting the hydration of tetracalcium aluminoferrite and improving the later-stage strength of high-alkali cement. The selected polyol amine ester is an esterification product of polyol amines with formic acid or acetic acid. The ester group protects the polyol amine, reducing its consumption in the early stages of high-alkali cement hydration. The polyol amine ester undergoes hydrolysis in the alkaline environment provided by cement hydration, generating polyol amines, which significantly enhance cement strength and can further improve the later-stage strength of high-alkali cement. While polycarboxylic acid compounds can effectively complex iron ions, their complexing effect is limited. The esterification product of polyol amines with formic acid or acetic acid has limited protective effect on the polyol amine through the ester group due to the relatively small steric hindrance of formic acid and acetic acid; furthermore, this technology only achieves its effect when both are combined.

[0006] CN109455289 discloses a high-alkali cement activator and its preparation method. The activator is composed of the following raw materials in weight percentages: sodium p-aminobenzenesulfonate 15%-25%, molasses 10%-15%, sodium bisulfite 5%-10%, sodium acetate 3%-8%, polyether polyol 5%-10%, and the balance being water. This high-alkali cement activator can significantly increase the early and late strength of high-alkali cement. At a dosage of 0.1% in cement, it can increase the 3-day compressive strength by 2.2-4.2 MPa and the 28-day compressive strength by 6.3-9.9 MPa. Simultaneously, it can delay the setting time of high-alkali cement and reduce the early hydration heat release, thereby reducing the risk of early shrinkage cracking when using high-alkali cement. However, it mainly uses commonly used grinding aids such as alkanolamines, polyols, and inorganic salts as raw material systems, compounded with some functional components, which has a limited strengthening effect on high-alkali cement.

[0007] CN104829152 discloses a high-alkali cement grinding aid and its preparation method. The high-alkali cement grinding aid comprises a grinding aid component, a gel crystal seeding agent, and additives; by weight percentage: 80%-95% grinding aid component, 1%-10% gel crystal seeding agent, and 0.5%-10% additives; wherein the grinding aid component is an alkanolamine grinding aid, and the gel crystal seeding agent is a CSH gel crystal seeding agent. It can increase the specific surface area of ​​cement by 11-25 m² within the same grinding time. 2 The grinding aid reduces cement specific surface area by 3-6% and sieve residue by 45μm, extends setting time by 20-30 min, and reduces drying shrinkage by less than 0.006%. It also increases cement mortar strength by 10%-15% after 28 days. The grinding aid components are diethanol monoisopropanolamine or ethanol diisopropanolamine, the CSH gel seed improver is sodium glycolate, and the additives are ethylene glycol and sodium dodecyl sulfate. While its grinding aid effect increases cement specific surface area and reduces sieve residue by 45μm, it may further promote early cement hydration, which is detrimental to the later strength improvement of high-alkali cement. Furthermore, the reinforcing materials used are primarily common diethanolamines.

[0008] CN105366977 discloses a cement reinforcing agent, its preparation method, and its application. This cement slurry reinforcing agent is synthesized by modifying wet-process precipitated silica through a chemical coupling reaction using an aminosilane coupling agent. Specifically, relative to 100 parts by weight of wet-process precipitated silica, the chemical modification process requires 500-1300 parts of deionized water, 1-15 parts of silane coupling modifier, 1-2 parts of anionic surfactant, and 10-30 parts of organic solvent. Using the national standard GB / T17671-1999, this product only needs to be added at 1.0-2.0 parts by weight of cement, and its strength can be increased by approximately 30 times compared to the 7-day strength of blank cement. It mainly achieves cement reinforcement by grafting an aminosilane coupling agent onto the hydroxyl groups on the surface of wet-process precipitated silica, but its dosage is very high, only 1.0-2.0 parts by weight of cement. Summary of the Invention

[0009] The purpose of this invention is to provide a slow-release high-alkali cement reinforcing agent, its preparation method, and its application. Targeting the hydration characteristics of high-alkali cement, this invention utilizes the designability of organic molecular structures to synthesize a high-alkali cement reinforcing agent that can efficiently promote the hydration of tetracalcium aluminoferrite and simultaneously provide slow-release reinforcement. The resulting product requires low dosage, can be used directly without compounding, and significantly improves the strength of high-alkali cement, especially its later-stage strength.

[0010] To achieve the above objectives, the following technical solution is adopted:

[0011] A slow-release high-alkali cement reinforcing agent has one of the following structures:

[0012]

[0013] R1, R2, and R3 are either H or methyl groups.

[0014] The preparation method of the above-mentioned slow-release high-alkali cement reinforcing agent includes the following steps:

[0015] Thiocyanobenzoic acid and polyol amines were mixed in a reaction vessel and stirred and heated to 160-180°C under nitrogen protection.

[0016] Add catalyst and dehydrating agent, stir and heat to 180-200℃, esterify for 5-10 hours, and separate the water generated during the reaction until no more water is produced to end the reaction.

[0017] Unreacted materials were removed through purification to obtain a slow-release high-alkali cement reinforcing agent.

[0018] According to the above scheme, the molar ratio of thiocyanobenzoic acid to polyol amine is (3-5):1; the amount of catalyst is 2-4% of the mass of thiocyanobenzoic acid; and the amount of dehydrating agent is 15-20% of the mass of thiocyanobenzoic acid.

[0019] According to the above scheme, the thiocyanobenzoic acid is one or any mixture of 3-isothiocyanobenzoic acid, 4-isothiocyanobenzoic acid, 2-amino-5-thiocyanobenzoic acid, and 3-isothiocyano-4-methoxybenzoic acid.

[0020] According to the above scheme, the polyol amine is one or any mixture of triethanolamine, diethanol monoisopropanolamine, hydroxyethyl diisopropanolamine, and triisopropanolamine.

[0021] According to the above scheme, the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid.

[0022] According to the above scheme, the water-removing agent is one of benzene and toluene.

[0023] The above-mentioned slow-release high-alkali cement reinforcing agent is used in the grinding or application process of high-alkali cement.

[0024] According to the above scheme, the alkali content of the high-alkali cement is greater than 0.8 wt%.

[0025] According to the above scheme, the dosage of the slow-release high-alkali cement reinforcing agent is 0.02 to 0.10 wt% of the cement.

[0026] A slow-release high-alkali cement reinforcing agent was prepared by esterification of the carboxyl group in a thiocyanobenzoic acid compound with the hydroxyl group in a polyol amine compound. Excess thiocyanobenzoic acid was used to esterify all the hydroxyl groups in the polyol amine compound. Concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid were used as catalysts to increase the esterification rate. Benzene or toluene was added as a dehydrating agent to continuously separate the water generated during the esterification reaction, thus promoting the esterification process. This synthetic route is reliable and has a high yield of the target product.

[0027] The slow-release high-alkali cement reinforcing agent prepared in this invention uses the lone pair electrons of S and N as electron donors to coordinate with iron ions and form a stable complex structure. The S=C=N- or N≡C-S- structure in the slow-release high-alkali cement reinforcing agent prepared in this invention is a ternary "forked" structure, with each characteristic unit working synergistically. Compared to single-structure thiocyanates, this further enhances its ability to complex iron ions; compared to multi-component organic carboxylic acid compounds with "forked" structures, S=C=N- or N≡C-S- has a stronger ability to complex iron ions. When cement is not reinforced, the iron ions in the cement mineral tetracalcium aluminoferrite dissolve slowly and in small amounts, and their contribution to the strength of cement stone through hydration generally occurs at 28 days or even later and is relatively small. The ternary "forked" structure of the slow-release high-alkali cement reinforcing agent prepared in this invention, consisting of S=C=N- or N≡C-S-, can efficiently promote the dissolution of iron ions in tetracalcium aluminoferrite, increase the dissolution rate and the total amount of dissolution, promote the hydration of tetracalcium aluminoferrite, and generate more hydration products that are beneficial to cement strength, thereby improving the strength of cement at all ages.

[0028] Polyol amine compounds have been extensively shown to be able to complex Ca produced during cement hydration. 2+ Fe 3+ Al 3+Plasma promotes the hydration of cement minerals, especially tricalcium silicate and tricalcium aluminate, thereby increasing cement strength. However, in high-alkali cement, any form of alkali, including alkali dissolved in clinker and alkali existing in a free state, greatly accelerates the hydration of C3S and C3A. Excessive hydration of C3S and C3A leads to an increase in harmful pores in the cement, which is why high-alkali cement has high early-stage strength but limited later-stage strength improvement. Adding polyol amine compounds to high-alkali cement exacerbates this phenomenon, further reducing the later-stage strength. Furthermore, the excessively rapid early hydration of C3S and C3A adsorbs large amounts of polyol amine compounds, "burying" and solidifying them within the hydration products, preventing sustained strength enhancement. This invention employs a thiocyanobenzoic acid compound to completely esterify the hydroxyl groups in the structure of a polyolamine compound. On the one hand, this reduces early hydration adsorption, preventing the early rapid hydration of C3S and C3A in high-alkali cement from adversely affecting later strength. On the other hand, the ester groups continuously undergo hydrolysis under the alkaline conditions generated during cement hydration, thus slowly releasing the polyolamine compound and achieving a slow-release strengthening effect, effectively improving the strength of high-alkali cement, especially its later strength.

[0029] Compared to the esterification products of small-molecule acids such as formic acid and acetic acid with polyol amines, the steric hindrance of the benzene in the esterification product structure of thiocyanobenzoic acid and polyol amines enhances the stability of the esterification product structure. On one hand, the greater steric hindrance makes it difficult for them to be adsorbed by C3S and C3A hydration products, effectively preventing them from being "buried" and solidified by early C3S and C3A hydration. On the other hand, the structural stability makes ester hydration more slow, resulting in a more significant sustained-release effect.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] 1. The slow-release high-alkali cement reinforcing agent provided by the present invention can efficiently and significantly promote the hydration of tetracalcium aluminoferrite in high-alkali cement minerals, effectively increasing the strength of cement at all ages.

[0032] 2. The slow-release high-alkali cement reinforcing agent provided by the present invention can effectively reduce the adsorption of reinforcing agent by early hydration products of high-alkali cement, and fully utilize the characteristics of cement hydration to provide an alkaline environment to continuously release substances with reinforcing effects, thereby achieving the effect of slow-release reinforcement and effectively improving the strength of high-alkali cement, especially the later strength.

[0033] 3. The slow-release high-alkali cement reinforcing agent provided by this invention makes full use of the role of each functional group in the structure, with a low dosage and obvious reinforcing effect, and has a higher cost performance.

[0034] 4. The method for preparing slow-release high-alkali cement reinforcing agent provided by the present invention is mature, safe, and has good controllability, and can be industrialized.

[0035] 5. The slow-release high-alkali cement reinforcing agent prepared by the method of preparing slow-release high-alkali cement reinforcing agent provided by the present invention can be used directly without further compounding, reducing production steps and lowering the product quality risk caused by multiple production steps. Detailed Implementation

[0036] The following embodiments further illustrate the technical solutions of the present invention, but are not intended to limit the scope of protection of the present invention. The following specific embodiments are only some preferred embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, modifications, substitutions, and improvements made by those skilled in the art without creative effort are all within the scope of protection of the present invention.

[0037] A specific embodiment provides a method for preparing a slow-release high-alkali cement reinforcing agent:

[0038] Thiocyanobenzoic acid compound and polyol amine compound were added to a reaction vessel in a specific ratio. Under nitrogen protection, the mixture was stirred and heated to 160–180°C. A catalyst and a dehydrating agent were added, and the mixture was stirred and heated to 180–200°C for esterification for 5–10 hours. During the reaction, the water generated was separated. The reaction was terminated when all the hydroxyl groups in the polyol amine compound were esterified and no more water was separated. The dehydrating agent and unreacted thiocyanobenzoic acid compound were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0039] The specific implementation details the sources of the test materials, which, unless otherwise specified, can be obtained commercially.

[0040] The specific embodiments provide that the thiocyanobenzoic acid compound is obtained commercially from Shanghai Dingmiao Chemical Technology Co., Ltd., Wuhan Livik Technology Co., Ltd., American Custom Chemicals Corporation, and Jinjinle (Hunan) Chemical Co., Ltd.

[0041] As a preferred embodiment, the molar ratio of the thiocyanobenzoic acid compound to the polyol amine compound is (3-5):1; the amount of catalyst is 2-4% of the mass of the thiocyanobenzoic acid compound; and the amount of dehydrating agent is 15-20% of the mass of the thiocyanobenzoic acid compound.

[0042] As a preferred embodiment, the thiocyanobenzoic acid compound is one or any mixture of 3-isothiocyanobenzoic acid, 4-isothiocyanobenzoic acid, 2-amino-5-thiocyanobenzoic acid, and 3-isothiocyano-4-methoxybenzoic acid.

[0043] As a preferred embodiment, the polyol amine is one or any mixture of the compounds triethanolamine, diethanol monoisopropanolamine, hydroxyethyl diisopropanolamine, and triisopropanolamine.

[0044] As a preferred embodiment, the catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, and concentrated phosphoric acid.

[0045] As a preferred embodiment, the water-removing agent is one of benzene and toluene.

[0046] The specific implementation also provides the application of the obtained slow-release high-alkali cement reinforcing agent in the grinding or use process of high-alkali cement.

[0047] Specifically, the alkali content of the high-alkali cement is greater than 0.8 wt%.

[0048] As a preferred embodiment, the dosage of the slow-release high-alkali cement reinforcing agent is 0.02 to 0.10 wt% of the cement.

[0049] Example 1

[0050] 3.0 mol of 3-isothiocyanobenzoic acid and 1 mol of triethanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 160°C. Then, 10.75 g of concentrated sulfuric acid and 80.64 g of benzene were added, and the mixture was stirred and heated to 180°C. The esterification reaction was carried out for 5.0 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the triethanolamine structure were esterified and no more water was separated, the benzene and unreacted 3-isothiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0051] Example 2

[0052] 3.2 mol of 4-isothiocyanobenzoic acid and 1 mol of diethanol monoisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 172°C. Then, 12.04 g of p-toluenesulfonic acid and 87.73 g of toluene were added, and the mixture was stirred and heated to 183°C. The esterification reaction was carried out for 5.5 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structure of diethanol monoisopropanolamine were esterified and no more water was separated, the toluene and unreacted 4-isothiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0053] Example 3

[0054] 4.3 mol of 2-amino-5-thiocyanobenzoic acid and 1 mol of hydroxyethyl diisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 165°C. Then, 23.38 g of concentrated phosphoric acid and 135.29 g of benzene were added, and the mixture was stirred and heated to 189°C. The esterification reaction was carried out for 5.3 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the hydroxyethyl diisopropanolamine structure were esterified and no more water was separated, the benzene and unreacted 2-amino-5-thiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0055] Example 4

[0056] 4.8 mol of 3-isothiocyano-4-methoxybenzoic acid and 1 mol of triisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 180°C. Then, 30.13 g of concentrated sulfuric acid and 175.75 g of toluene were added, and the mixture was stirred and heated to 192°C. The esterification reaction was carried out for 6.1 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structure of triisopropanolamine were esterified and no more water was separated, the toluene and unreacted 3-isothiocyano-4-methoxybenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0057] Example 5

[0058] 5.0 mol of 3-isothiocyanobenzoic acid and 1 mol of triisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 161°C. Then, 29.57 g of p-toluenesulfonic acid and 166.65 g of benzene were added, and the mixture was stirred and heated to 195°C. The esterification reaction was carried out for 7.4 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structure of triisopropanolamine were esterified and no more water was separated, benzene and unreacted 3-isothiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0059] Example 6

[0060] 1.5 mol of 3-isothiocyanobenzoic acid, 1.6 mol of 4-isothiocyanobenzoic acid, and 1 mol of triethanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 169°C. Then, 21.66 g of concentrated phosphoric acid and 106.10 g of toluene were added, and the mixture was stirred and heated to 194°C. The esterification reaction was carried out for 8.3 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the triethanolamine structure were esterified and no more water was separated, the toluene and unreacted 3-isothiocyanobenzoic acid and 4-isothiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0061] Example 7

[0062] 2.4 mol of 2-amino-5-thiocyanobenzoic acid, 2.5 mol of 3-isothiocyano-4-methoxybenzoic acid, 0.2 mol of triethanolamine, and 0.8 mol of hydroxyethyl diisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 173°C. Then, 34.62 g of concentrated sulfuric acid and 194.86 g of benzene were added, and the mixture was stirred and heated to 193°C. The esterification reaction was carried out for 9.5 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structures of triethanolamine and hydroxyethyl diisopropanolamine were esterified and no more water was separated, benzene and unreacted 2-amino-5-thiocyanobenzoic acid and 3-isothiocyano-4-methoxybenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0063] Example 8

[0064] 1.5 mol of 3-isothiocyanobenzoic acid, 1.5 mol of 4-isothiocyanobenzoic acid, 1.5 mol of 2-amino-5-thiocyanobenzoic acid, and 0.1 mol of triethanolamine, 0.5 mol of hydroxyethyl diisopropanolamine, and 0.4 mol of triisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 175°C. Then, 31.50 g of p-toluenesulfonic acid and 165.78 g of toluene were added, and the mixture was stirred and heated to 200°C. The esterification reaction was carried out for 10.0 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structures of triethanolamine, hydroxyethyl diisopropanolamine, and triisopropanolamine were esterified and no more water was separated, the toluene and unreacted 3-isothiocyanobenzoic acid, 4-isothiocyanobenzoic acid, and 2-amino-5-thiocyanobenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0065] Example 9

[0066] 0.2 mol of 4-isothiocyanobenzoic acid, 2.5 mol of 2-amino-5-thiocyanobenzoic acid, 1.0 mol of 3-isothiocyano-4-methoxybenzoic acid, and 0.2 mol of triethanolamine, 0.5 mol of diethanol monoisopropanolamine, 0.1 mol of hydroxyethyl diisopropanolamine, and 0.2 mol of triisopropanolamine were added sequentially to a reaction vessel in a specific ratio. Under nitrogen protection, the mixture was stirred and heated to 179°C. Then, 29.22 g of concentrated phosphoric acid and 126.39 g of benzene were added, and stirring continued. The mixture was heated to 183℃ and esterified for 7.8 hours. During the reaction, the water generated was separated. After all the hydroxyl groups in the structures of triethanolamine, diethanol monoisopropanolamine, hydroxyethyl diisopropanolamine, and triisopropanolamine were esterified and no more water was separated, benzene and unreacted 4-isothiocyanobenzoic acid, 2-amino-5-thiocyanobenzoic acid, and 3-isothiocyano-4-methoxybenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0067] Example 10

[0068] 1.0 mol of 3-isothiocyanobenzoic acid, 1.0 mol of 4-isothiocyanobenzoic acid, 1.0 mol of 2-amino-5-thiocyanobenzoic acid, and 1.0 mol of... 3-Isothiocyano-4-methoxybenzoic acid and 1 mol of diethanol monoisopropanolamine were added sequentially to a reaction vessel in a certain proportion. Under nitrogen protection, the mixture was stirred and heated to 170°C. Then, 19.05 g of concentrated sulfuric acid and 140.18 g of toluene were added, and the mixture was stirred and heated to 190°C. The esterification reaction was carried out for 9.1 h. During the reaction, the water generated was separated. After all the hydroxyl groups in the structure of diethanol monoisopropanolamine were esterified and no more water was separated, the toluene and unreacted 3-isothiocyanobenzoic acid, 4-isothiocyanobenzoic acid, 2-amino-5-thiocyanobenzoic acid, and 3-isothiocyano-4-methoxybenzoic acid were removed to obtain a slow-release high-alkali cement reinforcing agent.

[0069] Comparative Example 1

[0070] Repeat Example 1, replacing 3-isothiocyanobenzoic acid with formic acid in equal amounts, while keeping other conditions unchanged, to obtain triethanolamine formate.

[0071] Comparative Example 2

[0072] Sodium thiocyanate was selected as a reinforcing material for high-alkali cement for comparison.

[0073] Comparative Example 3

[0074] Monodiethanolamine, a polyol amine compound, was selected as a reinforcing material for high-alkali cement for comparison.

[0075] Comparative Example 4

[0076] Mono-nitrotriacetic acid, a "forked" polycarboxylic acid compound centered on nitrogen, was selected as a reinforcing material for high-alkali cement for comparison.

[0077] The performance of the slow-release high-alkali cement reinforcing agents prepared in Examples 1 to 10 and the substances described in Comparative Examples 1 to 4 were tested and evaluated.

[0078] 1. Measurement of iron ion concentration in the liquid phase of cement slurry during cement hydration.

[0079] High-alkali cement with an alkali content of 0.93% was mixed with water to prepare a slurry with a water-cement ratio of 0.6. The prepared slurry was placed in a sealed container and stirred with a magnetic stirrer for 60 min. Then, it was centrifuged in a centrifuge at a speed of 3000 r / min for 10 min. The supernatant was filtered through a 0.22 μm filter membrane. Nitric acid was then added to adjust the pH of the solution to 5-6. The iron ion concentration in the solution was measured using a Thermo Fisher|iCAP PRO X inductively coupled plasma atomic emission spectrometer. The iron ion concentration in the liquid phase of the slurry during cement hydration was measured for the blank group without reinforcing agent and the slow-release high-alkali cement reinforcing agent prepared in Examples 1 to 10 with 0.03 wt% cement admixture, as well as the substances described in Comparative Examples 1 to 4. The results are shown in Table 1.

[0080] Table 1

[0081]

[0082]

[0083] As shown in Table 1, the slow-release high-alkali cement reinforcing agent prepared in this invention significantly increased the iron ion concentration in the liquid phase of the cement slurry during cement hydration compared to the blank group, and was significantly superior to triethanolamine formate, sodium thiocyanate, monoisopropanolamine diethanolamine, and monotriacetic acid. The increased iron ion concentration in the liquid phase of the slurry during cement hydration indicates that the slow-release high-alkali cement reinforcing agent prepared in this invention effectively promotes the dissolution and hydration of tetracalcium aluminoferrite in the cement mineral phase.

[0084] 2. Evaluation of the reinforcing effect of high-alkali PO 42.5 cement

[0085] Take 5 kg of various cement raw materials and add them to the test mill according to the PO 42.5 cement mix ratio: clinker 85%, slag 10%, gypsum 5%, and fix the grinding time to 25 min. The alkali content of the clinker is 1.28%, and the alkali content of the prepared high alkali PO 42.5 cement is 1.16%.

[0086] Referring to GB / T 17671-1999 Cement Mortar Strength Test Method (ISO Method), 450g of cement, 1350g of standard sand, and 225g of water were mixed and molded. The 3-day and 28-day cement strength tests were conducted on the blank group without reinforcing agent and the slow-release high-alkali cement reinforcing agent prepared in Examples 1 to 10 with 0.03wt% cement admixture, as well as the substances described in Comparative Examples 1 to 4. The results are shown in Table 2.

[0087] Table 2

[0088] serial number 3d flexural strength / MPa 3d compressive strength / MPa 28-day flexural strength / MPa 28-day compressive strength / MPa Blank group 7.0 33.3 8.5 46.5 Comparative Example 1 6.9 32.9 8.7 48.3 Comparative Example 2 7.2 34.3 8.0 45.3 Comparative Example 3 7.3 34.7 8.1 45.8 Comparative Example 4 7.2 34.0 8.3 46.8 Example 1 7.5 35.9 9.5 52.8 Example 2 7.6 36.7 9.3 53.2 Example 3 7.7 36.5 9.4 53.7 Example 4 7.5 37.2 9.4 53.4 Example 5 7.8 36.1 9.6 53.8 Example 6 7.7 37.0 9.0 53.2 Example 7 7.5 37.2 9.2 52.9 Example 8 7.6 36.9 9.1 54.0 Example 9 7.8 36.1 9.3 52.9 Example 10 7.6 36.7 9.3 53.3

[0089] As can be seen from Table 2, the slow-release high-alkali cement reinforcing agent prepared in this invention significantly increased the 3-day and 28-day flexural and compressive strengths of high-alkali cement compared with the blank group and triethanolamine formate, sodium thiocyanate, diethanolamine monoisopropanolamine, and monotriacetic acid. This indicates that the slow-release high-alkali cement reinforcing agent prepared in this invention not only significantly improves the early 3-day strength of cement but also further enhances the later 28-day strength of cement through slow-release action, demonstrating excellent reinforcing effect.

Claims

1. A slow-release high-alkali cement reinforcing agent, characterized in that... It has one or any combination of the following structures: ； ； ； ； R1, R2, and R3 are either H or methyl groups.

2. The preparation method of the slow-release high-alkali cement reinforcing agent according to claim 1, characterized in that... Includes the following steps: Thiocyanobenzoic acid and polyol amine are mixed in a reaction vessel and stirred and heated to 160-180°C under nitrogen protection; wherein the thiocyanobenzoic acid is one or any mixture of 3-isothiocyanobenzoic acid, 4-isothiocyanobenzoic acid, 2-amino-5-thiocyanobenzoic acid, and 3-isothiocyano-4-methoxybenzoic acid. Add catalyst and dehydrating agent, stir and heat to 180~200℃, esterify for 5-10 hours, and separate the water generated during the reaction until no more water is produced to end the reaction. Unreacted materials were removed through purification to obtain a slow-release high-alkali cement reinforcing agent.

3. The preparation method of the slow-release high-alkali cement reinforcing agent as described in claim 2, characterized in that... The molar ratio of thiocyanobenzoic acid to polyol amine is (3~5):1; the amount of catalyst is 2~4% of the mass of thiocyanobenzoic acid; and the amount of dehydrating agent is 15~20% of the mass of thiocyanobenzoic acid.

4. The preparation method of the slow-release high-alkali cement reinforcing agent as described in claim 2, characterized in that... The polyol amine is one or any mixture of triethanolamine, diethanol monoisopropanolamine, hydroxyethyl diisopropanolamine, and triisopropanolamine.

5. The preparation method of the slow-release high-alkali cement reinforcing agent as described in claim 2, characterized in that... The catalyst is one of concentrated sulfuric acid, p-toluenesulfonic acid, or concentrated phosphoric acid.

6. The preparation method of the slow-release high-alkali cement reinforcing agent as described in claim 2, characterized in that... The water-removing agent is either benzene or toluene.

7. The application of the slow-release high-alkali cement reinforcing agent according to claim 1 in the grinding or use process of high-alkali cement.

8. The application of the slow-release high-alkali cement reinforcing agent as described in claim 7 in the grinding or use process of high-alkali cement, characterized in that... The high-alkali cement has an alkali content greater than 0.8 wt%.

9. The application of the slow-release high-alkali cement reinforcing agent as described in claim 7 in the grinding or use process of high-alkali cement, characterized in that... The dosage of the slow-release high-alkali cement reinforcing agent is 0.02~0.10 wt% of the cement.

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