Calcium ion complexing type early-strength polycarboxylate superplasticizer and preparation method thereof

Abstract

The invention discloses an early-strength polycarboxylate superplasticizer and a preparation method thereof, and belongs to the technical field of concrete admixtures. Aiming at the problem of insufficient early strength performance of the existing polycarboxylate superplasticizer, through molecular structure optimization and early strength component collaborative design, isopentenyl polyglycol ether, unsaturated acid and unsaturated small monomers are used as polymerization main bodies, and calcium salt is introduced as an early strength component, so that the early strength performance of the polycarboxylate superplasticizer is improved. A product is prepared through segmented dropwise addition polymerization reaction in a specific initiation-reduction system; the main chain carboxyl of the water reducing agent ensures high water reducing rate, the side chain and the acylamino cooperate with the calcium salt to accelerate cement hydration, and through the dual mechanisms of carboxyl-calcium ion complexation and rapid dissolution and crystallization of calcium silicate, the final setting time of concrete is remarkably shortened, and the early strength of 1d, 3d and 7d is improved.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to a calcium ion complexing type early-strength polycarboxylate superplasticizer and its preparation method. Background Technology

[0002] As the most widely used building material globally, concrete's performance directly determines the construction efficiency and service life of infrastructure. Water-reducing agents, as key admixtures for concrete, can reduce water consumption without sacrificing slump. They improve the fluidity of concrete mixtures and enhance the density and mechanical properties of hardened concrete, making them a core component in modern concrete preparation systems.

[0003] While mainstream polycarboxylate superplasticizers on the market currently achieve high water reduction rates (typically exceeding 25%) thanks to their flexible molecular design, they exhibit significant shortcomings in specific engineering scenarios: conventional polycarboxylate superplasticizers contain only dispersed functional groups such as carboxyl groups and ether bonds in their molecular structure, lacking active sites that can accelerate cement hydration. This prevents them from promoting the rapid dissolution of calcium silicate in cement and the efficient generation of hydration products (such as ettringite). Consequently, the early strength development of concrete is slow in low-temperature environments, leading to extended construction cycles. In emergency repair projects, they cannot quickly reach the required load-bearing strength, affecting emergency project needs. Furthermore, the long demolding time in precast component production restricts production efficiency.

[0004] In existing technologies, there are two main approaches to improving the early strength of concrete: one is to add an early-strength agent (such as chloride-based, sulfate-based, or organic-based early-strength agents) to the concrete. However, these agents can easily lead to a decline in the strength of concrete in the later stages, and chloride ions in chloride-based agents can cause steel corrosion. The other approach is to modify the polycarboxylate superplasticizer molecule, such as by introducing amide or sulfonic acid groups. Introducing cationic groups can improve the adsorption performance of the polycarboxylate superplasticizer on cement minerals and accelerate the early hydration of cement. However, the introduction of functional monomers can weaken the water-reducing performance and reduce the dispersion performance of the superplasticizer, thus affecting construction efficiency. Therefore, developing a polycarboxylate superplasticizer that combines high water reduction rate, good dispersion performance, and excellent early-strength performance, and is suitable for low-temperature construction and rapid demolding of precast components, has become a key technological breakthrough for solving special engineering needs. Summary of the Invention

[0005] The purpose of this invention is to provide a calcium ion complexing early-strength polycarboxylate superplasticizer and its preparation method. By rationally designing the ratio of main chain carboxyl groups, side chain long ether segments and small monomer functional groups, a polycarboxylate superplasticizer that still has high water reduction rate and early strength performance at room temperature or low temperature is achieved, overcoming the problems of strong dependence on early strength agents, high cost and later strength decay in the prior art.

[0006] This invention provides a method for preparing a calcium ion complexing type early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0007] 1) Prepare a monomer solution by mixing isopentenyl polyoxyethylene ether (TPEG), initiator and water; prepare solution A by mixing unsaturated acid monomer and water; prepare solution B by mixing unsaturated small monomer, chain transfer agent and water; prepare solution C by mixing reducing agent, calcium salt and water.

[0008] 2) Add solutions A, B, and C dropwise simultaneously to the monomer solution to carry out a free radical reaction. After the reaction is complete, the mother liquor is obtained.

[0009] 3) After neutralizing and adding water to the mother liquor, a calcium ion complexing type early strength polycarboxylate superplasticizer is obtained.

[0010] In step 1 of the above preparation method, the epoxy addition number of the isopentenyl polyoxyethylene ether is 1 to 110.

[0011] In step 1 of the above preparation method, the unsaturated acid monomer is one or more of methacrylic acid, acrylic acid, itaconic acid, or maleic anhydride.

[0012] In step 1 of the above preparation method, the unsaturated monomer is one or more of acrylamide, 2-acrylamido-2-methylpropanesulfonic acid, or N-hydroxymethylacrylamide.

[0013] In step 1 of the above preparation method, the calcium salt is one or more of calcium carbonate, calcium nitrate, or calcium sulfate.

[0014] In step 1 of the above preparation method, the initiator is one or more of ammonium persulfate, hydrogen peroxide, potassium persulfate, sodium sulfite, or ammonium thiosulfate.

[0015] In step 1 of the above preparation method, the reducing agent is one or more of sodium formaldehyde sulfoxylate, L-ascorbic acid, or ferrous sulfate.

[0016] In step 1 of the above preparation method, the chain transfer agent is one or more of mercaptoethanol, sodium methylpropenesulfonate, or mercaptopropionic acid.

[0017] In step 1 of the above preparation method, the mass ratio of the isopentenyl polyoxyethylene ether, unsaturated acid monomer, unsaturated small monomer, calcium salt, chain transfer agent, initiator, reducing agent and water is 350~400:10~40:10~40:25~35:0.5~3:0.1~10:0.3~1.2:300~600.

[0018] In step 2 of the above preparation method, the free radical reaction temperature is 15℃~50℃ and the reaction pressure is atmospheric pressure.

[0019] In step 2 of the above preparation method, the free radical reaction includes a dropping reaction stage and a heat preservation reaction stage. In the dropping reaction stage, the dropping time of solution A is 180~300 min, the dropping time of solution B is 190~330 min, and the dropping time of solution C is 190~330 min. Solution A is dropped 10~30 min before solutions B and C are dropped. After all solutions A, B and C are dropped, the heat preservation reaction stage begins. The reaction time of the heat preservation reaction stage is 60~180 min.

[0020] In step 3 of the above preparation method, neutralization refers to adding liquid alkali until the pH of the mother liquor is 6-8. The liquid alkali is a 30%-50wt% NaOH aqueous solution, and the dropping rate is 1-2 drops / second.

[0021] In step 3 of the above preparation method, the water replenishment refers to adding water to the mother liquor until the reaction solid content is 40%.

[0022] This invention provides a calcium ion complexed early-strength polycarboxylate superplasticizer prepared by the above-described method, wherein the calcium ion complexed early-strength polycarboxylate superplasticizer contains carboxyl groups and Ca... 2+ and functional groups, wherein the functional groups are one or more of amide groups or sulfonic acid groups.

[0023] The calcium ion complexing early-strength polycarboxylate superplasticizer has a solid content of 40% and a PDI ≤ 1.4.

[0024] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0025] 1. During the free radical polymerization reaction of polycarboxylic acid mother liquor, the oxygen atom in the carboxyl group can provide lone pair electrons to coordinate with calcium ions in the calcium salt to form a stable and soluble complex. The complex structure allows the calcium ions to be stably locked in the complex and not easily destroyed or released by other substances.

[0026] 2. The high-density carboxyl groups on the main chain of the calcium ion complexing early-strength polycarboxylate superplasticizer provide continuous electrorepulsion, and the long ether side chains form a stable steric hindrance and lubrication layer, thereby rapidly depolymerizing cement flocs. High water reduction rate can be achieved with low dosage, and the yield stress is significantly reduced and the fluidity decays slowly. Thus, it can still maintain uniform workability under pumping and complex formwork conditions.

[0027] 3. Carboxyl complexation causes Ca... 2+Uniform application avoids surface enrichment and re-agglomeration; amide groups promote C3S / C2S dissolution and trigger rapid crystallization of the same ion, while ettringite (Aft) and initial CSH proliferate synchronously to form an intercalated framework, thereby significantly shortening the setting time and improving 1-day strength. The entire process achieves a synergistic effect of high water reduction and early strength without sacrificing fluidity. Attached Figure Description

[0028] Figure 1 The image shows the GPC spectrum of the calcium ion complexed early-strength polycarboxylate superplasticizer prepared in Example 5. Detailed Implementation

[0029] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0030] Unless otherwise specified, all test materials and reagents used in the following examples are commercially available.

[0031] Example 1

[0032] A method for preparing a calcium ion complexed early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0033] 1) By mass, mix 35 parts acrylic acid and 30 parts water to prepare solution A; mix 20 parts acrylamide, 1 part mercaptoethanol and 30 parts water to prepare solution B; mix 0.7 parts L-ascorbic acid, 25 parts calcium nitrate and 50 parts water to prepare solution C; add 350 parts TPEG monomer with an epoxy addition number of 50 and 450 parts water to a four-necked flask equipped with a stirrer and a thermometer. After monomer A is completely dissolved in the flask, add 0.5 parts H2O2 and stir for 30 min to obtain the monomer solution.

[0034] 2) The reaction conditions are atmospheric pressure and the initial reaction temperature is 15℃. Solution A, solution B and solution C are added dropwise to the monomer solution at the same time. Solution A is added dropwise over a period of 180 min, solution B over a period of 210 min and solution C over a period of 210 min. After all solutions A, B and C have been added, the reaction is kept at the temperature for 120 min to obtain the mother liquor. The minimum temperature during the reaction is not lower than 15℃ and the maximum temperature is not higher than 30℃.

[0035] 3) After the reaction is complete, add 30%wt% NaOH aqueous solution at a dropping rate of 1 drop / second until the pH of the mother liquor is 7. After the pH value is 7, add water until the solid content of the mother liquor is 40%. Continue stirring for 20 minutes to obtain calcium ion complexing early strength polycarboxylate superplasticizer.

[0036] Example 2

[0037] A method for preparing a calcium ion complexed early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0038] 1) By weight, mix 20 parts acrylic acid, 15 parts itaconic acid and 30 parts water to prepare solution A; mix 10 parts acrylamide, 1 part mercaptoethanol and 30 parts water to prepare solution B; mix 0.7 parts L-ascorbic acid, 25 parts calcium nitrate and 50 parts water to prepare solution C; add 350 parts TPEG monomer with an epoxy addition number of 50 and 450 parts water to a four-necked flask equipped with a stirrer and a thermometer. After the TPEG monomer is completely dissolved, add 0.5 parts H2O2 and stir for 30 min to obtain the monomer solution.

[0039] 2) The reaction conditions are atmospheric pressure and the initial reaction temperature is 15℃. Solution A, solution B and solution C are added dropwise to the monomer solution at the same time. Solution A is added dropwise over a period of 180 min, solution B over a period of 210 min and solution C over a period of 210 min. After all solutions A, B and C have been added, the reaction is kept at the temperature for 120 min to obtain the mother liquor. The minimum temperature during the reaction is not lower than 15℃ and the maximum temperature is not higher than 30℃.

[0040] 3) After the reaction is complete, add 30%wt%NaOH aqueous solution at a dropping rate of 1 drop / second until the pH of the mother liquor is 7. After the pH value is 7, add water until the solid content of the mother liquor is 40%. Continue stirring for 20 minutes to obtain calcium ion complexed early strength polycarboxylate superplasticizer.

[0041] Example 3

[0042] A method for preparing a calcium ion complexed early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0043] 1) By mass, mix 30 parts maleic anhydride and 50 parts water to prepare solution A; mix 10 parts acrylamide, 1 part mercaptoethanol and 30 parts water to prepare solution B; mix 25 parts calcium nitrate, 0.7 parts L-ascorbic acid and 30 parts water to prepare solution C; add 360 parts TPEG monomer with an epoxy addition number of 50 and 450 parts water to a four-necked flask equipped with a stirrer and a thermometer. After the TPEG monomer is completely dissolved, add 4 parts potassium persulfate, heat to 45°C, and stir for 30 min to obtain the monomer solution.

[0044] 2) The reaction conditions are atmospheric pressure and the reaction temperature is 45℃. Solution A, solution B and solution C are added dropwise to the monomer solution at the same time. Solution A is added dropwise for 180 min, solution B for 210 min and solution C for 210 min. After all solutions A, B and C are added, the reaction is kept at the temperature for 120 min to obtain the mother liquor. The minimum temperature during the reaction is not lower than 15℃ and the maximum temperature is not higher than 30℃.

[0045] 3) After the reaction is complete, add 30%wt%NaOH aqueous solution at a dropping rate of 1 drop / second until the pH of the mother liquor is 7. After the pH value is 7, add water until the solid content of the mother liquor is 40%, and obtain calcium ion complexed early strength polycarboxylate superplasticizer.

[0046] Example 4

[0047] A method for preparing a calcium ion complexed early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0048] 1) By weight, mix 25 parts acrylic acid, 5 parts methacrylic acid and 30 parts water to prepare solution A; mix 10 parts 2-acrylamide-2-methylpropanesulfonic acid, 1 part mercaptopropionic acid and 30 parts water to prepare solution B; mix 0.5 parts sodium formaldehyde sulfoxylate, 30 parts calcium nitrate and 30 parts water to prepare solution C; add 360 parts TPEG monomer with an epoxy addition number of 50 and 450 parts water to a four-necked flask equipped with a stirrer and a thermometer. After the TPEG monomer is completely dissolved, add 0.5 parts H2O2 and stir for 30 minutes to obtain the monomer solution.

[0049] 2) The reaction conditions are atmospheric pressure and the initial reaction temperature is 15℃. Solution A, solution B and solution C are added dropwise to the monomer solution at the same time. Solution A is added dropwise for 180 min, solution B for 210 min and solution C for 210 min. After all solutions A, B and C are added, the reaction is kept at the temperature for 120 min to obtain the mother liquor. The minimum temperature is not lower than 15℃ and the maximum temperature is not higher than 30℃.

[0050] 3) After the reaction is complete, add 30%wt%NaOH aqueous solution at a dropping rate of 1 drop / second until the pH of the mother liquor is 7. After the pH value is 7, add water until the solid content of the mother liquor is 40%. Continue stirring for 20 minutes to obtain calcium ion complexed early strength polycarboxylate superplasticizer.

[0051] Example 5

[0052] A method for preparing a calcium ion complexed early-strength polycarboxylate superplasticizer, the method comprising the following steps:

[0053] 1) By weight, mix 35 parts acrylic acid and 30 parts water to prepare solution A; mix 10 parts 2-acrylamide-2-methylpropanesulfonic acid, 1 part mercaptoethanol and 30 parts water to prepare solution B; mix 0.7 parts L-ascorbic acid, 25 parts calcium nitrate and 50 parts water to prepare solution C; add 360 parts TPEG monomer with an epoxy addition number of 50 and 450 parts water to a four-necked flask equipped with a stirrer and a thermometer. After the TPEG monomer is completely dissolved, add 0.5 parts H2O2 and stir for 30 min to obtain the monomer solution.

[0054] 2) The reaction conditions are atmospheric pressure and the initial reaction temperature is 15℃. Solution A, solution B and solution C are added dropwise to the monomer solution at the same time. Solution A is added dropwise for 180 min, solution B for 210 min and solution C for 210 min. After all solutions A, B and C are added, the reaction is kept at the temperature for 120 min to obtain the mother liquor. The minimum temperature is not lower than 15℃ and the maximum temperature is not higher than 30℃.

[0055] 3) After the reaction is complete, add 30%wt%NaOH aqueous solution at a dropping rate of 1 drop / second until the pH of the mother liquor is 7. After the pH value is 7, add water until the solid content of the mother liquor is 40%. Continue stirring for 20 minutes to obtain calcium ion complexed early strength polycarboxylate superplasticizer.

[0056] Comparative Example 1

[0057] A method for preparing a polycarboxylate superplasticizer, the method comprising the following steps:

[0058] The preparation method of this comparative example is the same as that of Example 5, except that calcium nitrate was not added to the comparative example, and the C solution in step 1 of Example 5 was replaced with 75 parts of water.

[0059] Comparative Example 2

[0060] This comparative example is an early-strength polycarboxylate superplasticizer prepared by diluting commercially available water-reducing agent ME540 (early-strength polycarboxylate mother liquor) from Tongling Conch New Material Technology Co., Ltd. with water to a concentration of 10% of the original mother liquor.

[0061] Test Example 1

[0062] Performance testing of calcium ion complexed early-strength polycarboxylate superplasticizer:

[0063] To verify the effectiveness of the calcium ion complexing early-strength polycarboxylate superplasticizer prepared by the method of this invention, the following are the application test results of Examples 1-5 and each comparative example in cement paste. The test method is based on GB / T 8077-2012 "Test Method for Homogeneity of Concrete Admixtures". Under the condition of water-cement ratio of 0.28, Conch brand PO 42.5 ordinary Portland cement is used as the base material, and the polycarboxylate superplasticizers of each example and each comparative example are added respectively. The specific data are shown in Table 1:

[0064] Table 1. Dispersion performance of calcium ion complexing early-strength polycarboxylate superplasticizer on cement paste

[0065] sample Dosage (%) Initial paste fluidity (mm) Flowability of the paste (mm) after 30 minutes Comparative Example 1 1.00 236 155 Comparative Example 2 1.00 243 165 Example 1 1.00 244 135 Example 2 1.00 234 139 Example 3 1.00 238 132 Example 4 1.00 239 133 Example 5 1.00 243 130

[0066] The initial flowability of each embodiment and comparative example was significantly reduced compared to the flowability after 30 min, reflecting early strength orientation. Flowability loss characterizes the early structure formation rate; the flowability loss range for each embodiment was 79–123 mm, while for comparative examples 1 and 2 it was 58 mm and 74 mm, respectively. The overall flowability loss of the embodiments was higher than that of the comparative examples, indicating that the embodiments have better early strength. Example 1, compared to comparative example 1, showed a difference in early strength performance despite not adding calcium salt, indicating that under the premise of consistent formulation and other process conditions, the flowability is enhanced by the interaction of the main chain / straight chain groups with Ca. 2+ The synergistic effect of these components significantly improves the structure establishment rate within 30 minutes without reducing the initial dispersion, thus demonstrating stronger early strength.

[0067] To verify the effectiveness of the calcium ion complexing early-strength polycarboxylate superplasticizer prepared by the method of this invention, the following are the application test results of Examples 1-5 and each comparative example in cement paste. The concrete mixture performance was tested according to GB / T8076-2008 "Concrete Admixtures". Under the condition of water-cement ratio of 0.28, Conch brand PO 42.5 ordinary Portland cement was used as the base material, with medium sand of fineness modulus of 2.6 and crushed stone of 5-20mm continuous gradation. The concrete mix ratio was C:S:G = 380:820:1050, and the superplasticizer dosage was 0.3%. Without the addition of retarder, the setting time of each example was compared with that of commercially available superplasticizer. Conch PO42.5 cement with a final setting time of 3h20min was used, and the standard curing room temperature was 20℃. The differences in concrete setting time are shown in Table 2 below:

[0068] Table 2 Final setting time of concrete with calcium ion complexing early-strength polycarboxylate superplasticizer

[0069] Water-reducing agent number Dosage (%) Concrete slump / spread (mm) Final setting time (h:min) Comparative Example 1 0.3 235 / 580 12:10 Comparative Example 2 0.3 240 / 560 12:45 Example 1 0.3 231 / 590 10:30 Example 2 0.3 227 / 585 10:00 Example 3 0.3 225 / 590 10:15 Example 4 0.3 227 / 590 10:30 Example 5 0.3 230 / 590 9:30

[0070] Slump / spread characterizes initial workability and flow spread capacity; similar values ​​indicate that initial dispersion and construction window are consistent. Final setting time characterizes early hydration and structure establishment rate; shorter time means stronger early strength orientation but narrower workable time; longer time means weaker early strength effect and wider open time.

[0071] All samples were within the same construction range in terms of slump / spread. None of the embodiments improved early strength at the expense of initial workability. The final setting time showed that the early strength of each embodiment was superior to Comparative Example 1 and Comparative Example 2, indicating that the calcium ion complexing early-strength polycarboxylate superplasticizer prepared in this invention has a good early-strength effect, shortening the setting time of concrete. The shortened setting time is beneficial to improving the early strength of concrete. The main reason is that the adsorption of the polycarboxylate superplasticizer is formed through the complexation reaction between calcium ions and carboxylate ions. The carboxylate ions and calcium ions adsorb and form a soluble complex, while providing a large number of uniform and effective nucleation sites for the formation of ettringite, accelerating the crystallization process and shortening the setting time of the cement paste. The product of this invention can significantly shorten the final setting time of concrete to as short as 9 hours and 30 minutes.

[0072] To test the compressive strength of concrete test blocks prepared from the products (early-strength polycarboxylate high-performance water-reducing agents) obtained in the above comparative examples and embodiments at different ages, the compressive strength of concrete was tested according to the relevant provisions of GB / T50081-2002 "Standard for Test Methods of Mechanical Properties of Ordinary Concrete". The test cement was Conch P.O42.5 cement, the fineness modulus was medium sand of 2.6, and the aggregate was 5-20mm continuously graded crushed stone. The concrete mix proportion was C:S:G = 380:820:1050, and the water-reducing agent dosage was 0.3% of the cement weight. The test results are shown in Table 3.

[0073] Table 3 Concrete strength of calcium ion complexing early-strength polycarboxylate superplasticizer

[0074] Water-reducing agent number Dosage (%) 1-day concrete strength / MPa 3d concrete strength / MPa 7-day concrete strength / MPa Comparative Example 1 0.3 7.0 18.5 23.6 Comparative Example 2 0.3 6.3 17.3 22.8 Example 1 0.3 6.9 20.3 26.5 Example 2 0.3 7.7 21.1 26.7 Example 3 0.3 7.3 22.2 27.4 Example 4 0.3 7.5 22.6 27.9 Example 5 0.3 8.2 23.5 28.6

[0075] The calcium ion complex-type early-strength polycarboxylate superplasticizer prepared in this invention exhibited better early-strength performance compared to Comparative Examples 1 and 2, with concrete specimens showing superior strength at 1, 3, and 7 days compared to Comparative Examples 1 and 2. Furthermore, Examples 5 and 1 verified the formation of calcium ion complexes, further enhancing the early-strength performance of the superplasticizer and further demonstrating the effectiveness of the "molecular design + early-strength component synergy" mechanism.

[0076] In summary, the calcium ion complexing early-strength polycarboxylate superplasticizer prepared in this invention forms a complex by reacting calcium ions with carboxylate groups, providing numerous, uniform, and effective nucleation sites for the formation of ettringite, thus accelerating the crystallization process and shortening the concrete setting time. The amide groups in the main chain of the synthesized polycarboxylate mother liquor superplasticizer synergistically interact with the early-strength component, accelerating the dissolution rate of calcium silicate. Under the influence of the common ion effect, this accelerates the crystallization rate, increases the solid phase ratio in the mortar, and is beneficial to the formation of the cement stone structure. In conclusion, this calcium ion complexing polycarboxylate superplasticizer improves the water-reducing effect while accelerating the hydration of calcium silicate, thereby accelerating the precipitation of Ca(OH)₂ crystals and enhancing the early strength of concrete.

[0077] Test Example 2

[0078] Gel permeation chromatography characterization:

[0079] The molecular weight and distribution of the product were determined by gel permeation chromatography (GPC). The mobile phase was 0.1 mol / L NaNO3 solution, the flow rate was 1.0 mL / min, and the column temperature was 35 °C. The GPC chromatogram obtained in Example 5 is shown below. Figure 1 As shown in Table 4 below:

[0080] Table 4 GPC Results Table for Example 5

[0081] Retention time (min) Mn Mw MP PDI %area 32.900 39071 54451 71818 1.393646 98.72 39.267 4559 4617 4781 1.024354 1.28

[0082] Example 5: The GPC spectrum shows that the retention time of the early-strength polycarboxylate high-performance water-reducing agent peak is 32.900 min, and the retention time of the unreacted TPEG monomer peak is 39.267 min. The peak shape of the early-strength polycarboxylate high-performance water-reducing agent peak is symmetrical, with no obvious impurity peaks. The molecular weight distribution coefficient is 1.3936, and the peak area accounts for 98.72%, indicating that the product has high purity and stable performance, which is an important reason why it has both high water reduction rate and early strength.

[0083] It should be noted that the above embodiments are merely some preferred embodiments of the present invention, and not all embodiments. Obviously, based on the above embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort should fall within the scope of protection of the present invention.

[0084] The above description of the embodiments is intended to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the disclosure of the present invention without departing from the scope of the invention should be within the protection scope of the present invention.

Claims

1. A method for preparing a calcium ion complexing type early strength polycarboxylate water reducing agent, characterized by, The preparation method comprises the following steps: 1) configuring isoprenyl polyoxyethylene ether, initiator and water into a monomer solution; configuring unsaturated acid monomer and water into A liquid; configuring unsaturated small monomer, chain transfer agent and water into B liquid; configuring reducing agent, calcium salt and water into C liquid; 2) adding A liquid, B liquid and C liquid into the monomer solution simultaneously for free radical reaction, and obtaining mother liquor after the reaction; 3) obtaining calcium ion complex type early strength polycarboxylic acid water reducer after neutralization and water supplement of the mother liquor.

2. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1, characterized in that, The isoprenyl polyoxyethylene ether has 1-110 epoxy addition numbers.

3. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1, characterized in that, The unsaturated acid monomer is one or more of methacrylic acid, acrylic acid, itaconic acid or maleic anhydride.

4. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1, characterized in that, The unsaturated small monomer is one or more of acrylamide, 2-acrylamide-2-methylpropane sulfonic acid or N-hydroxymethyl acrylamide.

5. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1, characterized in that, The calcium salt is one or more of calcium carbonate, calcium nitrate or calcium sulfate.

6. The method for preparing the early-strength polycarboxylate superplasticizer of calcium ion complex type according to any one of claims 1 to 5, characterized in that, The mass ratio of the isoprenyl polyoxyethylene ether, unsaturated acid monomer, unsaturated small monomer, calcium salt, chain transfer agent, initiator, reducing agent and water is 350-400:10-40:10-40:25-35:0.5-3:0.1-10:0.3-1.2:300-600.

7. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1, characterized in that, The reaction temperature of the free radical reaction is 15-50 DEG C, and the reaction pressure is normal pressure.

8. The method for preparing the calcium ion complexing type early strength polycarboxylate water reducer according to claim 1 or 7, characterized in that, The free radical reaction comprises a dropwise reaction stage and a heat preservation reaction stage, the dropwise reaction stage has a dropwise adding time of A liquid of 180-300 min, a dropwise adding time of B liquid of 190-330 min, a dropwise adding time of C liquid of 190-330 min, and A liquid is dropped completely 10-30 min before B liquid and C liquid are dropped completely, and the heat preservation reaction stage has a reaction time of 60-180 min.

9. The calcium ion complexing type early strength polycarboxylate water reducer prepared by the preparation method according to any one of claims 1-8, characterized in that, The calcium ion complexing type early strength type polycarboxylate water reducer contains carboxyl, Ca 2+ and a functional group which is one or more of an amide group or a sulfonic acid group.

10. The calcium ion complexing type early strength type polycarboxylate water reducer according to claim 9, characterized by, The calcium ion complex type early strength polycarboxylic acid water reducer has a solid content of 40%, and PDI≤1.4.

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