Early-strength viscosity-reducing water reducer for LC3 cement as well as preparation method and application of early-strength viscosity-reducing water reducer

Abstract

The invention relates to an early-strength viscosity-reducing water reducer for LC3 cement and a preparation method and application thereof, and the preparation method comprises the following steps: mixing anion ring-opened cucurbituril containing double bonds, a first solid monomer and deionized water, heating and stirring until complete dissolution to obtain a mixed solution; adding an initiator into the mixed solution, dropwise adding a second monomer aqueous solution and a chain transfer agent aqueous solution at the same time within 3 hours, after dropwise adding is finished, carrying out heat preservation reaction for 0.5-1.5 hours, and terminating the reaction to obtain the early-strength viscosity-reducing water reducer for the LC3 cement. According to the invention, ring-opened cucurbituril containing an anionic solubilizing group is introduced, so that the water solubility is good, a hydrophobic structure is provided, the thickness of a water film layer of LC3 cement particles in slurry can be effectively reduced, more bound water is released for slurry flowing, the water consumption is effectively reduced, and the workability of cement is improved; the early-strength viscosity-reducing water reducer is high in strength and large in size, ineffective adsorption of the early-strength viscosity-reducing water reducer in LC3 cement is avoided, the dosage is reduced, growth of CH crystals is promoted, and the early strength of the cement is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixtures, specifically relating to an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement, its preparation method, and its application. Background Technology

[0002] LC3 cement, short for limestone-calcined clay cement, is a composite cementitious material composed of limestone, calcined clay, gypsum, and clinker. Utilizing the synergistic effect of calcined clay and limestone, it achieves strength development similar to ordinary Portland cement (OPC). In LC3-X, X represents the proportion of clinker to the total cement mass. The most typical example is LC3-50, composed of 50% ordinary Portland cement clinker, 30% calcined clay, 15% limestone, and 5% gypsum. The production of LC3 cement can reduce carbon dioxide emissions by up to 30% and energy consumption by 15%–20%. Currently, greenhouse gas emission controls are becoming increasingly stringent, while global reserves of suitable clay raw materials are considerable. The widespread use of LC3 cement will play a significant role in energy conservation and emission reduction in the global cement industry.

[0003] However, LC3 cement has the following problems during use: LC3 cement typically contains about 30% calcined clay, whose layered structure leads to a significant increase in specific surface area. Therefore, it needs to absorb more water to coat the particle surface, which is the main reason for the increased water demand of LC3 cement. Simultaneously, the layered structure of calcined clay increases interparticle friction, making it difficult for particles to slide and affecting the cohesiveness and fluidity of the cement paste. To achieve the same fluidity, more water needs to be added. Furthermore, its layered structure may also absorb more admixtures, leading to a decrease in the dispersant effect. In addition, LC3 cement has a relatively low proportion of cement clinker and a relatively low amount of minerals such as C3S, which hydrate quickly. The main component of calcined clay is active aluminosilicate, which hydrates slowly, resulting in less cementitious material produced during early hydration and slow early strength development. Currently, the fourth-generation high-performance water-reducing agent—polycarboxylate superplasticizer—is widely used in concrete engineering. As a green and environmentally friendly product, polycarboxylate superplasticizer has the following advantages: high water reduction rate, low dosage, and can significantly improve concrete strength; good initial dispersibility and excellent slump retention; wide adaptability, compatible with various cementitious materials; and good controllability of molecular structure, allowing for the design of products with specific functions by changing the main chain length, side chain type, and functional group types. Summary of the Invention The purpose of this invention is to overcome the above-mentioned technical deficiencies and provide an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement, its preparation method, and its application, thereby solving the technical problems of high water demand, poor workability, high admixture dosage, and low early strength of LC3 cement in the prior art.

[0004] To achieve the above-mentioned technical objectives, the technical solution provided by this invention is as follows: In a first aspect, the present invention provides a method for preparing an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement, comprising the following steps: S1, mixing an anionic ring-opening cucurbita containing double bonds, a first solid monomer, and deionized water, heating and stirring until completely dissolved to obtain a mixture; S2, adding an initiator to the mixture, and then simultaneously adding an aqueous solution of a second monomer and an aqueous solution of a chain transfer agent within 3 hours. After the addition is completed, maintaining the temperature for 0.5 to 1.5 hours, and terminating the reaction to obtain the early-strength, viscosity-reducing, and water-reducing agent for LC3 cement.

[0005] Secondly, the present invention provides an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement prepared by the above-mentioned preparation method.

[0006] Thirdly, the present invention provides an application of the above-mentioned early strength, viscosity-reducing, and water-reducing agent as an admixture for LC3 cement.

[0007] Compared with the prior art, the beneficial effects of the present invention include: This invention uses anionic open-ring cucurbita containing double bonds as raw materials to introduce anionic solubilizing groups into an early-strength, viscosity-reducing, and water-reducing agent. This results in good water solubility and a C-shaped flexible hydrophobic cavity structure. The main chain is polymerized from small monomers containing carboxyl and sulfonic acid groups, which have strong adsorption properties to cement particles. This effectively reduces the thickness of the water film layer of LC3 cement particles in the slurry, releasing more bound water for slurry flow, effectively reducing water consumption, and improving cement workability. Furthermore, the large size of the open-ring cucurbita structure results in a product size larger than the lamellar spacing of calcined clay, avoiding ineffective adsorption of the early-strength, viscosity-reducing, and water-reducing agent in LC3 cement. This effectively reduces the amount of early-strength, viscosity-reducing, and water-reducing agent needed, avoiding the retarding phenomenon caused by excessive admixtures and contributing to early strength growth. Simultaneously, it facilitates the induction of heterogeneous nucleation, promoting CH crystal growth and increasing the number of early-stage CH crystals, significantly improving early strength. Detailed Implementation

[0008] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0009] To address the shortcomings of LC3 cement, such as high water demand, poor workability, high admixture dosage, and low early strength, this invention provides an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement, its preparation method, and its application. This early-strength, viscosity-reducing, and water-reducing agent has a multi-pendant single-chain tandem structure. The pendant structure is an open-ring cucurbita containing anionic solubilizing groups, exhibiting good water solubility and a C-shaped flexible hydrophobic cavity structure. The main chain is polymerized from small monomers containing carboxyl and sulfonic acid groups, which have strong adsorption properties to cement particles. This effectively reduces the thickness of the water film layer of LC3 cement particles in the slurry, releasing more bound water for slurry flow, effectively reducing water consumption, and improving cement workability. Furthermore, the large size of the open-ring cucurbita structure results in a product size larger than the lamellar spacing of calcined clay, avoiding ineffective adsorption in LC3 cement and reducing dosage. Simultaneously, it facilitates the induction of heterogeneous nucleation, promoting CH crystal growth and increasing the number of early-stage CH crystals, significantly improving early strength.

[0010] In a first aspect, the present invention provides a method for preparing an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement, comprising the following steps: S1, mix anionic ring-opening cucurbita containing double bonds, the first solid monomer and deionized water, heat and stir until completely dissolved to obtain a mixture; S2, add an initiator to the mixture, and then simultaneously add the second monomer aqueous solution and the chain transfer agent aqueous solution within 3 hours. After the addition is completed, keep the reaction at a constant temperature for 0.5 to 1.5 hours, and then terminate the reaction to obtain LC3 cement early strength viscosity reducing water-reducing agent.

[0011] Preferably, in step S1, the preparation step of the anionic open-ring cucurbita containing double bonds includes: reacting unsaturated carboxylic acid with halogen-modified asymmetric open-ring cucurbita in a mixed solution of inorganic base and aprotic solvent, the reaction temperature is 20-60℃, the reaction time is 2-4h, and after the reaction is completed, the anionic open-ring cucurbita containing double bonds is obtained through post-treatment.

[0012] More preferably, the unsaturated carboxylic acid includes one or more of methacrylic acid, acrylic acid, 2-butenoic acid, fumaric acid, and pentenoic acid.

[0013] A further preferred embodiment of the halogen-modified asymmetric open-ring cucurbituril is prepared by reacting a tetramer, a first hydroquinone derivative, a second hydroquinone derivative, or a p-naphthol derivative as raw materials in a mixed solution of a strong organic acid and an organic solvent at 60–80°C. The specific preparation method is described in patent CN110724273A, "A Class of Asymmetric Open-Ring Cucurbituril and its Preparation Method".

[0014] More preferably, the first hydroquinone derivative is 1-(2-bromoethoxy)-4-methoxybenzene, with the following structural formula: ; Second hydroquinone derivatives or p-naphthol derivatives include: , or ; R8 is (CH2)3SO3Na or (CH2)2PO(ONa)2.

[0015] More preferably, the molar ratio of unsaturated carboxylic acid to halogen-modified asymmetric open-ring cucurbita is (1.2-1.7):1; and the molar ratio of halogen-modified asymmetric open-ring cucurbita to inorganic base is 1:(15-36).

[0016] More preferably, the inorganic base includes one or more of sodium carbonate, potassium carbonate, sodium hydroxide, and potassium hydroxide; the aprotic solvent includes one or more of dimethylformamide, dimethyl sulfoxide, tetrahydrofuran, and acetone.

[0017] Further preferred post-treatment includes: cooling the reaction system to room temperature, removing the solvent by vacuum distillation, dissolving the obtained solid in an appropriate amount of water, dialyzing it through a dialysis bag for 24-36 hours, filtering the dialysate through a 0.45 μm microporous membrane, and freeze-drying the obtained filtrate to obtain anionic open-ring cucurbita containing double bonds.

[0018] Preferably, the heating temperature in step S1 and the temperature of the heat preservation reaction in step S2 are both 25-45°C.

[0019] Preferably, the molar ratio of the double-bonded anionic ring-opening cucurbitaureide, the first solid monomer, and the second monomer is 1:(2-5):(3-8).

[0020] Preferably, the first solid monomer is one or more of sodium allyl sulfonate, sodium methyl methacrylate sulfonate, fumaric acid, and maleic anhydride.

[0021] Preferably, the initiator is one or more of ammonium persulfate, potassium persulfate, and tert-butyl hydroperoxide.

[0022] Preferably, the second monomer is one or more of methacrylic acid, acrylic acid, 3-methyl-2-butenoic acid, and 2-butenoic acid.

[0023] Preferably, the chain transfer agent is one or more of mercaptoethanol, mercaptoacetic acid, and mercaptopropionic acid.

[0024] Preferably, in step S2, the dropping time of the second monomer aqueous solution is 1 to 2 hours; the dropping time of the chain transfer agent aqueous solution is 1.5 to 2.5 hours.

[0025] Preferably, in step S2, the reaction is terminated by adding deionized water after the heat preservation reaction.

[0026] Preferably, the mass ratio of the double-bonded anionic ring-opening cucurbita, initiator, chain transfer agent, and total deionized water is 100:(1.4–3.6):(0.3–1.7):(175–230). The total deionized water refers to all deionized water added throughout the reaction, including the deionized water in step S1, the deionized water used to prepare the second monomer aqueous solution and the chain transfer agent aqueous solution, and the deionized water added when terminating the reaction.

[0027] Secondly, the present invention provides an early-strength, viscosity-reducing, and water-reducing agent for LC3 cement prepared by the above-mentioned preparation method.

[0028] Preferably, the molecular weight of the early strength reducing and water-reducing agent for LC3 cement is 20,000 to 30,000.

[0029] Thirdly, the present invention provides an application of the above-mentioned early strength, viscosity-reducing, and water-reducing agent as an admixture for LC3 cement.

[0030] The synthetic route for anionic ring-opening cucurbita containing double bonds in this invention mainly includes: (a) Preparation of halogen-modified asymmetric ring-opening cucurbituril (refer to patent CN110724273A):

[0031] The structures of the resulting halogen-modified asymmetric open-ring cucurbituril mainly include: (1) (2) (3) R8 is (CH2)3SO3Na or (CH2)2PO(ONa)2.

[0032] (b) Preparation of anionic open-ring cucurbituril containing double bonds:

[0033] The structures of the resulting anionic ring-opening cucurbituril containing double bonds mainly include: (4) (5) (6) Where n = 0 or 2; R5 is H, CH3 or COOH; R6 is H or CH3; R8 is (CH2)3SO3Na or (CH2)2PO(ONa)2.

[0034] According to the preparation method, the structural formula of the LC3 cement early-strength, viscosity-reducing, and water-reducing agent obtained by this invention is shown in Formula I below: Formula I Where a = 3–7, b = 2–4, c = 1; R0 is H or CH3; R1 is H, CH3, or COOH; R2 is H or CH3; R3 is SO3Na, CH2SO3Na, or COOH; R4 is H or CH3; R5 is H, CH3, or COOH; R6 is H or CH3; R7 is selected from: , , .

[0035] Where n=0 or 2; R8 is (CH2)3SO3Na or (CH2)2PO(ONa)2.

[0036] The main advantages of this invention are: (1) The LC3 cement early-strength, viscosity-reducing, and water-reducing agent has an anionic open-ring cucurbita structure. Anionic open-ring cucurbita is composed of a glycyrrhetinic tetramer as the backbone, two substituted aromatic ring ends, and two to four anionic groups with solubilizing effects. Open-ring cucurbita has a flexible C-shaped cavity, and the cavity size can be appropriately adjusted. The solubilizing groups derived from the two aromatic ring ends give it high solubility and ionic function. The characteristics of hydrophobic outer wall of the cavity, hydrophobic inner cavity, and polar carbonyl modified ports not only give it the function of a host molecule, which can encapsulate organic molecules with suitable structure and size; it can also act as a ligand molecule, coordinating with metal ions and their complexes or clusters to form a unique cucurbita coordination chemistry; all of these provide conditions for open-ring cucurbita to become an excellent carrier. This invention uses anionic open-ring cucurbita containing double bonds as a carrier. In addition to being hydrophilic at the outer wall end, it exhibits strong hydrophobicity in both the inner and outer walls of the cavity. This effectively reduces the thickness of the water film layer of LC3 cement particles in the slurry, releasing more bound water for slurry flow, effectively reducing water consumption and improving concrete strength. At the same time, the open-ring cucurbita structure has a larger size than the lamellar spacing of calcined clay, avoiding ineffective adsorption of early-strength viscosity-reducing water-reducing agents in LC3 cement, reducing the amount of early-strength viscosity-reducing water-reducing agents used, and thus avoiding the retardation phenomenon caused by excessive admixtures, which helps with early strength growth.

[0037] (2) In LC3 cement, the tricalcium silicate (C3S) content in the cement clinker is relatively low, resulting in a slow early hydration rate and fewer generated calcium hydroxide (CH) crystals. This insufficient hydration provides a substrate for the growth of calcium silicate gel (CSH), leading to lower early strength. The anionic groups on the terminal aromatic ring of the open-ring cucurbita and the several carbonyl oxygen groups on both sides can promote Ca2+ hydration through intermolecular interactions. 2+Enrichment at the open-ring cucurbita port induces heterogeneous nucleation, forming CH crystal nuclei. The hydrophobic C-shaped cavities act as crystal growth channels, guiding the CH crystals to grow along a one-dimensional direction, promoting an increase in the number of early-stage CH crystals and significantly improving early strength. Furthermore, during hydration, CH crystals gradually grow and fill some micropores (especially capillaries with a diameter <50nm), while the overlap between crystals also enhances the "skeleton support" of the cement paste, reducing early stress concentration caused by porosity and indirectly improving early compressive strength.

[0038] To better understand the present invention, the following embodiments further illustrate the content of the present invention, but the content of the present invention is not limited to the following embodiments.

[0039] Example 1 An early-strength, viscosity-reducing, and water-reducing agent S1 for LC3 cement has the following structural formula:

[0040] Where a=4, b=2, c=1; R0 is H; R1 is H; R2 is CH3; R3 is CH2SO3Na; R4 is H; R5 is CH3; R6 is H; R7 is:

[0041] Where n=0, R8 is (CH2)3SO3Na.

[0042] A method for preparing an early-strength, viscosity-reducing, and water-reducing agent S1 for LC3 cement includes the following steps: (1) 2-Butenoic acid (51.7 g, 0.60 mol) and halogen-modified asymmetric open-ring cucurbita BS1 (Formula 1, R8 is (CH2)3SO3Na, 654.2 g, 0.50 mol) were weighed and added to a 1000 mL round-bottom flask. Then, a mixed solution of sodium hydroxide and dimethyl sulfoxide was added. The molar ratio of halogen-modified asymmetric open-ring cucurbita BS1 to sodium hydroxide was 1:16. The reaction was stirred at 25 °C for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed by vacuum distillation. The obtained solid was dissolved in an appropriate amount of water and dialyzed through a dialysis bag for 24 h. The dialysate was filtered through a 0.45 μm microporous membrane. The obtained filtrate was freeze-dried to obtain anionic open-ring cucurbita KS1 (Formula 4, n=1, R8 is (CH2)3SO3Na) containing double bonds, with a yield of 62%.

[0043] (2) Weigh out 331.0 g (0.25 mol) of anionic open-ring cucurbita KS1 containing double bonds, 80.1 g (0.50 mol) of sodium methacrylate sulfonate and 300.0 g of deionized water in sequence and add them to a 1000 mL four-necked flask. Then heat and stir at 25 °C until completely dissolved. Keep the temperature and stirring conditions unchanged, add 4.7 g of ammonium persulfate. Then simultaneously start adding solution A, which is a mixture of acrylic acid (72.1 g, 1.0 mol) and 56 g of water, and solution B, which is a mixture of mercaptoacetic acid (2.1 g) and 80.0 g of water. Add solution A for 1.1 h and solution B for 1.5 h. After the addition is completed, keep warm for 0.5 h and then add 161.9 g of water. The product obtained is LC3 cement early strength reducing and water-reducing agent S1. The Mn is 27060, the polydispersity index is 1.42 and the conversion rate is 89% by gel permeation chromatography.

[0044] Example 2 An early-strength, viscosity-reducing, and water-reducing agent S2 for LC3 cement has the following structural formula:

[0045] Where a=5, b=2, c=1; R0 is CH3; R1 is H; R2 is H; R3 is CH2SO3Na; R4 is H; R5 is H; R6 is CH3; R7 is:

[0046] Where n=0, R8 is (CH2)3SO3Na.

[0047] A method for preparing an early-strength, viscosity-reducing, and water-reducing agent S2 for LC3 cement includes the following steps: (1) 50.3 g of methacrylic acid (0.58 mol) and 550.7 g of halogen-modified asymmetric open-ring cucurbita BS2 (Formula 2, R8 is (CH2)3SO3Na, 0.40 mol) were weighed and added to a 1000 mL round-bottom flask. Then a mixed solution of sodium carbonate and dimethylformamide was added. The molar ratio of halogen-modified asymmetric open-ring cucurbita BS2 to sodium carbonate was 1:34. The reaction was stirred at 30 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed by vacuum distillation. The obtained solid was dissolved in an appropriate amount of water and dialyzed through a dialysis bag for 30 h. The dialysate was filtered through a 0.45 μm microporous membrane. The obtained filtrate was freeze-dried to obtain anionic open-ring cucurbita KS2 (Formula 5, n=0, R8 is (CH2)3SO3Na) containing double bonds, with a yield of 60%.

[0048] (2) Weigh out 329.3 g (0.24 mol) of anionic open-ring cucurbita KS2 containing double bonds, 69.2 g (0.48 mol) of sodium allyl sulfonate and 300.0 g of deionized water in sequence and add them to a 1000 mL four-necked flask. Then heat and stir at 30 °C until completely dissolved. Keep the temperature and stirring conditions unchanged, add 6.5 g of potassium persulfate. Then simultaneously start adding solution A, which is a mixture of 103.3 g (1.2 mol) of methacrylic acid and 87.5 g of water, and solution B, which is a mixture of 2.7 g of mercaptopropionic acid and 85.2 g of water. Add solution A for 1.5 h and solution B for 1.8 h. After the addition is completed, keep warm for 1.0 h and add 151.9 g of water. The product obtained is LC3 cement early strength reducing and water-reducing agent S2. The Mn is 24340, the polydispersity index is 1.46 and the conversion rate is 85% by gel permeation chromatography.

[0049] Example 3 An early-strength, viscosity-reducing, and water-reducing agent S3 for LC3 cement has the following structural formula:

[0050] Where a=3, b=4, c=1; R0 is H; R1 is CH3; R2 is H; R3 is COOH; R4 is COOH; R5 is H; R6 is H; R7 is:

[0051] Where n=0, R8 is (CH2)3SO3Na.

[0052] A method for preparing an early-strength, viscosity-reducing, and water-reducing agent S3 for LC3 cement includes the following steps: (1) Acrylic acid (31.1 g, 0.43 mol) and halogen-modified asymmetric open-ring cucurbita BS3 (Formula 3, R8 is (CH2)3SO3Na, 356.7 g, 0.26 mol) were weighed and added to a 1000 mL round-bottom flask. Then, a mixed solution of potassium hydroxide and tetrahydrofuran was added. The molar ratio of halogen-modified asymmetric open-ring cucurbita BS3 to potassium hydroxide was 1:27. The reaction was stirred at 40 °C for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed by vacuum distillation. The obtained solid was dissolved in an appropriate amount of water and dialyzed through a dialysis bag for 36 h. The dialysate was filtered through a 0.45 μm microporous membrane. The obtained filtrate was freeze-dried to obtain anionic open-ring cucurbita KS3 (Formula 6, n=0, R8 is (CH2)3SO3Na) containing double bonds, with a yield of 59%.

[0053] (2) Weigh out 313.6 g (0.23 mol) of anionic open-ring cucurbita KS3 containing double bonds, 90.2 g (0.92 mol) of maleic anhydride, and 290.0 g of deionized water in sequence and add them to a 1000 mL four-necked flask. Then heat and stir at 45 °C until completely dissolved. Keep the temperature and stirring conditions unchanged, add 11.2 g of tert-butyl hydroperoxide, and then simultaneously start adding solution A, which is a mixture of 59.4 g (0.69 mol) of 2-butenoic acid and 80.5 g of water, and solution B, which is a mixture of 5.1 g of mercaptoacetic acid and 85.2 g of water. Add solution A for 2 h and solution B for 2.5 h. After the addition is completed, keep warm for 1.5 h, and then add 130.3 g of water. The product obtained is LC3 cement early strength reducing and water-reducing agent S3. The Mn is 22700, the polydispersity index is 1.47, and the conversion rate is 90% as determined by gel permeation chromatography.

[0054] Example 4 An early-strength, viscosity-reducing, and water-reducing agent S4 for LC3 cement has the following structural formula:

[0055] Where a=4, b=3, c=1; R0 is H; R1 is H; R2 is H; R3 is CH2SO3Na; R4 is H; R5 is H; R6 is H; R7 is:

[0056] Where n=2, R8 is (CH2)2PO(ONa)2.

[0057] A method for preparing an early-strength, viscosity-reducing, and water-reducing agent S4 for LC3 cement includes the following steps: (1) Pentenic acid (41.0 g, 0.41 mol) and halogen-modified asymmetric open-ring cucurbita BS4 (Formula 1, R8 is (CH2)2PO(ONa)2, 319.9 g, 0.24 mol) were weighed and added to a 1000 mL round-bottom flask. Then, a mixed solution of potassium carbonate and dimethyl sulfoxide was added. The molar ratio of halogen-modified asymmetric open-ring cucurbita BS4 to potassium carbonate was 1:36. The reaction was stirred at 50 °C for 4 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed by vacuum distillation. The obtained solid was dissolved in an appropriate amount of water and dialyzed through a dialysis bag for 32 h. The dialysate was filtered through a 0.45 μm microporous membrane. The obtained filtrate was freeze-dried to obtain anionic open-ring cucurbita KS4 (Formula 4, n=2, R8 is (CH2)2PO(ONa)2) containing double bonds, with a yield of 64%.

[0058] (2) Weigh out 297.5 g (0.22 mol) of anionic open-ring cucurbita KS4 containing double bonds, 95.1 g (0.66 mol) of sodium allyl sulfonate and 260.0 g of deionized water in sequence and add them to a 1000 mL four-necked flask. Then heat and stir at 40 °C until completely dissolved. Keep the temperature and stirring conditions unchanged, add 9.5 g of potassium persulfate, and then simultaneously start adding solution A, which is a mixture of acrylic acid (63.4 g, 0.88 mol) and 75.0 g of water, and solution B, which is a mixture of mercaptoethanol (2.0 g) and 80.0 g of water. Add solution A for 1.5 h and solution B for 1.7 h. After the addition is completed, keep warm for 0.8 h, and then add 156.4 g of water. The product obtained is LC3 cement early strength reducing and water-reducing agent S4. The Mn value is 25360, the polydispersity index is 1.41 and the conversion rate is 92% by gel permeation chromatography.

[0059] Example 5 An early-strength, viscosity-reducing, and water-reducing agent S5 for LC3 cement has the following structural formula:

[0060] Where a=3, b=2, c=1; R0 is CH3; R1 is H; R2 is H; R3 is CH2SO3Na; R4 is H; R5 is H; R6 is CH3; R7 is:

[0061] Where n=0, R8 is (CH2)2PO(ONa)2.

[0062] A method for preparing an early-strength, viscosity-reducing, and water-reducing agent S5 for LC3 cement includes the following steps: (1) 40.5 g of methacrylic acid (0.47 mol) and 470.2 g of halogen-modified asymmetric open-ring cucurbita BS5 (Formula 2, R8 is (CH2)2PO(ONa)2, 0.34 mol) were weighed and added to a 1000 mL round-bottom flask. Then a mixed solution of sodium carbonate and dimethylformamide was added. The molar ratio of halogen-modified asymmetric open-ring cucurbita BS5 to sodium carbonate was 1:31. The reaction was stirred at 60 °C for 3.5 h. After the reaction was completed, the mixture was cooled to room temperature and the solvent was removed by vacuum distillation. The obtained solid was dissolved in an appropriate amount of water and dialyzed through a dialysis bag for 30 h. The dialysate was filtered through a 0.45 μm microporous membrane. The obtained filtrate was freeze-dried to obtain anionic open-ring cucurbita KS5 (Formula 5, n=0, R8 is (CH2)2PO(ONa)2) containing double bonds, with a yield of 62%.

[0063] (2) Weigh out 291.5 g (0.21 mol) of anionic open-ring cucurbita KS5 containing double bonds, 60.5 g (0.42 mol) of sodium allyl sulfonate and 260.0 g of deionized water in sequence and add them to a 1000 mL four-necked flask. Then heat and stir at 35 °C until completely dissolved. Keep the temperature and stirring conditions unchanged, add 9.2 g of potassium persulfate. Then simultaneously start adding solution A, which is a mixture of 54.2 g (0.63 mol) of methacrylic acid and 75.0 g of water, and solution B, which is a mixture of 4.0 g of mercaptopropionic acid and 85.0 g of water. Add solution A for 1.5 h and solution B for 1.8 h. After the addition is completed, keep warm for 1.0 h and add 93 g of water. The product obtained is LC3 cement early strength reducing and water-reducing agent S5. The Mn is 20180, the polydispersity index is 1.47 and the conversion rate is 86% by gel permeation chromatography.

[0064] Comparative Example 1: The difference from Example 1 is that the anionic open-ring cucurbita KS1 containing double bonds is not added, while the other steps and conditions are the same as in Example 1; the resulting product is LC3 concrete early strength reducing and water-reducing agent D1, with Mn=12750, polydispersity index of 1.34, and conversion rate of 86% as determined by gel permeation chromatography.

[0065] Comparative Example 2: The difference from Example 1 is that the anionic ring-opening cucurbita KS1 containing double bonds was replaced with vinyl polyoxyethylene ether (molecular weight 6000), and the other steps and conditions were the same as in Example 1. The resulting product is LC3 concrete early strength reducing and water-reducing agent D2. The Mn was 27330, the polydispersity index was 1.43, and the conversion rate was 86% as determined by gel permeation chromatography. Comparative Example 3: The difference from Example 1 is that the anionic ring-opening cucurbita KS1 containing double bonds was replaced with methyl allyl polyoxyethylene ether (molecular weight 2400), and the other steps and conditions were the same as in Example 1. The resulting product is LC3 concrete early strength reducing and water-reducing agent D3. The Mn was 27480, the polydispersity index was 1.44, and the conversion rate was 91% as determined by gel permeation chromatography.

[0066] Comparative Example 4: Commercially available early-strength water-reducing agent, detected by gel permeation chromatography, has an Mn of 22000, a polydispersity index of 1.36, a conversion rate of 85%, and a vinyl polyoxyethylene ether macromonomer molecular weight of 6000.

[0067] Performance testing 1. The test method for the fluidity of cement paste was based on the national standard GB / T8077-2023 "Test Method for Homogeneity of Concrete Admixtures". The initial fluidity and fluidity changes over time of the above samples under different admixture dosages were tested. The adaptability of the examples in LC3 cement and ordinary Portland cement was compared. The composition of LC3 cement was: 50% Huaxin cement clinker, 30% calcined clay, 15% limestone, and 5% gypsum; the ordinary Portland cement was Huaxin cement PO42.5. The water-cement ratio was 0.29. The admixture dosages in all examples and comparative examples were calculated as folded-solids dosages. The results are shown in Table 1.

[0068] Table 1. Results of Cement Paste Flowability Test

[0069] 2. The testing methods for initial slump, slump spread, and loss over time of concrete were in accordance with the national standard GB / T 8076-2008 "Concrete Admixtures". The testing methods for the physical and mechanical properties of concrete were in accordance with the relevant methods for specimen preparation, curing, compressive strength, and flexural strength testing in the national standard GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The specimen size was 100mm×100mm×100mm. The raw materials used for testing were Huaxin dry-process manufactured sand (fineness 3.0, MB value 0.2), crushed stone I (continuous gradation, particle size 5-10mm), crushed stone II (continuous gradation, particle size 10-20mm), and LC3 cement as described in section 1. The admixture dosage was the flexural-to-solid ratio, and the water-cement ratio was 0.45. The raw material dosage was 330 kg / m³ of LC3 cement. 3 780 kg / m³ of manufactured sand 3 Crushed stone I 315 Kg / m 3 Crushed stone II 830 Kg / m 3 150 kg / m³ of water 3 The results are shown in Table 2.

[0070] Table 2 Concrete slump flow and related strength results

[0071] Table 1 shows that, under a water-cement ratio of 0.29 and an admixture dosage of 1‰ (converted to solids), when using ordinary Portland cement PO42.5, the difference in fluidity between the cement paste prepared in the examples and the comparative examples at 0h and 1h is not significant. This indicates that the early-strength, viscosity-reducing, and water-reducing agent prepared in the examples has good adaptability in ordinary cement. The cement paste prepared with only the early-strength, viscosity-reducing, and water-reducing agent of Comparative Example 1 lacks fluidity at 1h. This is because Comparative Example 1 did not add anionic open-ring cucurbita containing double bonds, and the synthesized water-reducing agent has a linear structure without branches. It mainly exerts electrostatic repulsion, lubrication, and ball-bearing effect on cement particles, without steric hindrance, and therefore lacks fluidity retention ability, making it unsuitable for ordinary Portland cement systems.

[0072] When the admixture dosage was 1‰ (converted to solids), and LC3 cement was used, the early-strength viscosity-reducing and water-reducing agent in Comparative Example 1 showed no fluidity at 0h and 1h, indicating that most of the linear early-strength viscosity-reducing and water-reducing agent was intercalated and adsorbed by the calcined clay. In Comparative Example 3, the early-strength viscosity-reducing and water-reducing agent used methyl allyl polyoxyethylene ether (molecular weight 2400) as the viscosity-reducing agent branch, which had a relatively short chain length. This resulted in most of the viscosity-reducing agent being intercalated and adsorbed by the clay, affecting the fluidity of the paste to 151 mm and 120 mm at 0h and 1h, respectively. In Comparative Examples 2 and 4, the admixtures both used polyether macromonomers with a molecular weight of 6000 as the admixture molecular branches. These branches had longer chain lengths and were less affected by the layered structure of the clay. The fluidity at 0h was 173 mm and 184 mm, respectively, and the fluidity at 1h was 142 mm and 157 mm, respectively. The cement paste with the early-strength, viscosity-reducing, and water-reducing agent added in the examples exhibited a flowability of 223–232 mm at 0 hours and 203–219 mm at 1 hour. This indicates that the layered structure of calcined clay in LC3 cement has minimal adsorption of the early-strength, viscosity-reducing, and water-reducing agent. The anionic open-ring cucurbita structure in the early-strength, viscosity-reducing, and water-reducing agent has a larger molecular size, making it less prone to clay intercalation and exhibiting excellent resistance to the layered clay structure. Therefore, the effective dosage for LC3 cement is higher. Furthermore, the anionic open-ring cucurbita structure has a hydrophilic outer wall with only the two ends at the port, while both the outer wall and the cavity have strong hydrophobic properties. The early-strength, viscosity-reducing, and water-reducing agent has a lower HLB value and a thinner water film layer, resulting in more free water for dispersing cement particles. When the admixture dosage increased to 1.3%, the increase in flowability of the early-strength, viscosity-reducing, and water-reducing agent in the examples was more significant than that in the comparative examples at 0 hours and 1 hour, further demonstrating the higher effective utilization rate of the early-strength, viscosity-reducing, and water-reducing agent.

[0073] Table 2 shows that when the water-cement ratio is 0.45 and the admixture dosage is 0.3%, the slump and spread of LC3 concrete in Comparative Examples 1 and 3 show no fluidity, indicating that neither the linear structure nor the short-branched structure of the admixture is suitable for LC3 concrete. Comparative Examples 2 and 4 had initial spreads of 340 and 360 mm respectively, and showed no fluidity after 1 hour, indicating that the long-branched structure of the admixture is also unsuitable for LC3 concrete.

[0074] The 1-day strength of LC3 concrete in Examples 1-5 was 22.8-24.3 MPa, which was 29.5%-38.1% higher than the 1-day compressive strength of 17.6 MPa in Comparative Example 4. The 3-day strength of LC3 concrete in Examples 1-5 was 30.5-32.4 MPa, which was 15.1%-22.3% higher than the 3-day compressive strength of 26.5 MPa in Comparative Example 4. In the early-strength, viscosity-reducing, and water-reducing agent structure, the anionic group on the terminal aromatic ring of the open-ring cucurbita and the eight carbonyl oxygen groups on both sides promote Ca2+ through intermolecular interactions. + Enrichment at the open-ring cucurbitacin port induces heterogeneous nucleation, forming CaH crystal nuclei. This guides the growth of CH crystals along a one-dimensional direction, promoting an increase in the number of early-stage CH crystals and significantly improving the 1-day and 3-day strength of LC3 concrete. As CH crystals gradually grow and fill some micropores, the overlap between their crystals enhances the "skeleton support" of the cement paste, reducing early-stage stress concentration caused by porosity and indirectly improving early-stage compressive strength.

[0075] The specific embodiments of the present invention described above do not constitute a limitation on the scope of protection of the present invention. Any other corresponding changes and modifications made in accordance with the technical concept of the present invention should be included within the scope of protection of the claims of the present invention.

Claims

1. A method for preparing an LC3 early strength viscosity reducing water-reducing agent for cement, characterized by, The method comprises the following steps: S1, mixing the anionic open ring cucurbituril containing double bond, the first solid monomer and deionized water, heating and stirring until completely dissolved to obtain a mixed solution; S2, adding an initiator to the mixed solution, and then simultaneously adding a second monomer aqueous solution and a chain transfer agent aqueous solution dropwise within 3 hours; after the dropwise addition is completed, the reaction is kept for 0.5-1.5 hours, and the reaction is terminated to obtain an LC3 early strength reducing water reducer for cement.

2. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 1, characterized in that, In step S1, the preparation steps of the anionic open ring cucurbituril containing double bond include: The unsaturated carboxylic acid and the halogen-modified asymmetric open ring cucurbituril are reacted in a mixed solution of inorganic base and aprotic solvent, the reaction temperature is 20-60°C, the reaction time is 2-4 hours, and after the reaction is completed, post-treatment is performed to obtain the anionic open ring cucurbituril containing double bond.

3. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 2, characterized in that, The unsaturated carboxylic acid includes one or more of methacrylic acid, acrylic acid, 2-butenoic acid, fumaric acid and pentenoic acid; The halogen-modified asymmetric open ring cucurbituril is prepared from a tetramer, a first hydroquinone derivative, a second hydroquinone derivative or a naphthalene hydroquinone derivative as raw materials in a mixed solution of an organic strong acid and an organic solvent at 60-80°C; The first hydroquinone derivative is 1-(2-bromoethoxy)-4-methoxybenzene, and the structural formula is: ； The second hydroquinone derivative or the naphthalene hydroquinone derivative includes: , or ; wherein R8 is (CH2)3SO3Na or (CH2)2PO(ONa)2.

4. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 2, characterized in that, The molar ratio of the unsaturated carboxylic acid to the halogen-modified asymmetric open ring cucurbituril is (1.2-1.7):1; The molar ratio of the halogen-modified asymmetric open ring cucurbituril to the inorganic base is 1:(15-36); The inorganic base includes one or more of sodium carbonate, potassium carbonate, sodium hydroxide and potassium hydroxide; The aprotic solvent includes one or more of dimethylformamide, dimethyl sulfoxide, tetrahydrofuran and acetone; The post-treatment includes: cooling the reaction system to room temperature, removing the solvent by reduced pressure distillation, dissolving the obtained solid in water, dialyzing with a dialysis bag for 24-36 hours, passing the dialysate through a 0.3-0.6 μm microporous filter membrane, and freeze-drying the obtained filtrate to obtain the anionic open ring cucurbituril containing double bond.

5. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 1, characterized in that, The temperature of the heating in step S1 and the temperature of the incubation reaction in step S2 are both 25-45°C.

6. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 1, characterized in that, The molar ratio of the anionic open ring cucurbituril containing double bond, the first solid monomer and the second monomer is 1:(2-5):(3-8).

7. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 1, characterized in that, The first solid monomer is one or more of allyl sulfonic acid sodium, methacryl sulfonic acid sodium, fumaric acid and maleic anhydride; The initiator is one or more of ammonium persulfate, potassium persulfate and tert-butyl hydroperoxide; The second monomer is one or more of methacrylic acid, acrylic acid, 3-methyl-2-butenoic acid and 2-butenoic acid; The chain transfer agent is one or more of mercaptoethanol, mercaptoacetic acid and mercapto propionic acid.

8. The method for preparing LC3 early strength viscosity reducing water-reducing agent for cement according to claim 1, characterized in that, In step S2, the dropwise addition time of the second monomer aqueous solution is 1-2 hours, and the dropwise addition time of the chain transfer agent aqueous solution is 1.5-2.5 hours; The termination of the reaction is performed by adding deionized water after the incubation reaction. The mass ratio of the double bond-containing anion ring-opening cucurbituril, initiator, chain transfer agent, and total deionized water is 100: (1.4-3.6): (0.3-1.7): (175-230).

9. The LC3 early strength water-reducing agent for cement prepared by the preparation method according to any one of claims 1-8.

10. The use of the early strength water-reducing agent according to claim 9 as an external additive for LC3 cement.

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