A chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete and its application

Abstract

This application relates to the field of water-reducing agent technology, specifically to a chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete and its application. The preparation method of the polycarboxylate superplasticizer includes: Step 1, preparing a polyether presol, a mixed monomer solution, an initiator solution, and a chain transfer agent solution; Step 2, heating the polyether presol to 65-75℃, simultaneously adding the mixed monomer solution and the initiator solution, and when half of the mixed monomer solution has been added, starting to add the chain transfer agent solution, maintaining a constant temperature for the reaction to obtain a polymerization reaction solution; Step 3, cooling the polymerization reaction solution to 40-50℃, adding a small molecule protective agent, stirring at a constant temperature, adjusting the pH value, maintaining the temperature for 30-40 minutes, and cooling to room temperature to obtain the polycarboxylate superplasticizer. The prepared polycarboxylate superplasticizer exhibits both strong dispersibility and good slump retention, with outstanding antifreeze performance. After 300 freeze-thaw cycles, the relative dynamic elastic modulus of the concrete remains high, and the mass loss rate is low.

Description

Technical Field

[0001] This application relates to the field of water-reducing agent technology, and more specifically, it relates to a chlorine-free high-performance polycarboxylate water-reducing agent for antifreeze concrete and its application. Background Technology

[0002] In concrete construction in cold regions, sub-zero temperatures are common during winter and the transition from winter to spring. High-performance water-reducing agents and antifreeze agents must be used simultaneously to ensure the workability and strength development of the concrete. In the isothermal cold regions of Xinjiang, temperatures drop below zero during the winter and early spring. Traditional methods of adding the two admixtures separately often result in poor compatibility and insufficient adaptability, leading to a decline in concrete performance. Furthermore, the procedures are complex and quality control is challenging.

[0003] While existing polycarboxylate superplasticizers possess excellent water-reducing and dispersing properties, dominating the superplasticizer market, single products struggle to simultaneously achieve both high-efficiency water reduction and freeze-thaw resistance. Some antifreeze admixtures contain chloride ions, which can corrode steel reinforcement in concrete, affecting project durability; chloride-free products, on the other hand, suffer from insufficient water reduction and slow strength development at sub-zero temperatures.

[0004] Currently, there is a lack of integrated polycarboxylate superplasticizers that simultaneously meet the requirements of being chlorine-free, having a high water-reducing rate, and exhibiting freeze-thaw resistance. These limitations make them unsuitable for construction in cold environments, hindering the efficiency and quality stability of concrete projects. Therefore, developing a high-performance polycarboxylate superplasticizer that is chlorine-free, environmentally friendly, and possesses synergistic water-reducing and freeze-thaw resistance properties, suitable for construction in cold regions, is of significant practical importance and market value. This would resolve the compatibility issues of traditional admixtures and improve the freeze-thaw durability and ease of construction of concrete projects. Summary of the Invention

[0005] To address the technical problems mentioned in the background section, this application provides a chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete and its application.

[0006] This application provides a chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete, employing the following technical solution:

[0007] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30-40 parts polyether monomer, 15-25 parts main chain monomer, 5-10 parts early strength functional monomer, 3-8 parts antifreeze synergist, 1-5 parts small molecule protective agent, 0.5-2 parts initiator, 0.1-1 parts chain transfer agent, and 120-180 parts deionized water.

[0008] Preferably, the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10-12:5-8.

[0009] Preferably, the main chain monomer is one or more of acrylic acid, methacrylic acid, and maleic anhydride.

[0010] Preferably, the early-strength functional monomer is one or more of hydroxypropyl methacrylate, acrylamide, and N-hydroxymethylacrylamide.

[0011] Preferably, the method for preparing the antifreeze synergist includes the following preparation steps:

[0012] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel and stirred until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed until homogeneous to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution. After the addition was complete, the reaction was kept at a constant temperature for 1-1.5 hours, then cooled to 35-40℃, the pH was adjusted to 6.0-7.0, and the mixture was allowed to cool naturally to room temperature to obtain an antifreeze synergist.

[0013] Preferably, the mass ratio of hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone and deionized water is 10-12:5-8:3-5:50-80.

[0014] Preferably, the small molecule protective agent is one of acrylate or acrylamide sulfonic acid.

[0015] Preferably, the initiator is ammonium persulfate and / or potassium persulfate; the chain transfer agent is mercaptoacetic acid and / or mercaptopropionic acid.

[0016] This application also provides a method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete, using the following technical solution:

[0017] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0018] Step 1: Stir the polyether monomer and deionized water evenly to obtain a polyether presol; stir the main chain monomer, early strength functional monomer, antifreeze synergist and deionized water evenly to obtain a mixed monomer solution; disperse the initiator evenly with deionized water to obtain an initiator solution; disperse the chain transfer agent evenly with deionized water to obtain a chain transfer agent solution.

[0019] Step 2: Heat the polyether presol to 65-75℃ and start adding the mixed monomer solution and initiator solution dropwise simultaneously. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. After the addition is complete, keep the temperature constant for 2-3 hours to obtain the polymerization reaction solution.

[0020] Step 3: Cool the polymerization reaction solution to 40-50℃, add a small molecule protective agent, stir at a constant temperature, adjust the pH value to 7.5-8.5, keep warm for 30-40 minutes, cool to room temperature, and obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0021] An application of a chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete is described. The specific application method is as follows: the superplasticizer is added to the concrete at 0.1-0.2% of the concrete mass for use in concrete construction of buildings, water conservancy, and transportation projects under negative temperature environments.

[0022] In summary, this application has the following beneficial effects:

[0023] This application utilizes a scientific blend of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether. The complementary structure of these two monomers allows for precise control of the length and branching degree of the water-reducing agent's molecular side chains, enhancing the selective adsorption efficiency of the molecules on the surface of cement particles and strengthening the persistence of the dispersion effect. This effectively avoids problems such as rapid decay of dispersion capacity and unstable slump retention caused by single monomers. This blended system can stabilize the initial spread of concrete at 660-690 mm, with excellent 1-hour spread retention, providing a good foundation for the densification of the concrete's internal structure while ensuring the stability of its workability.

[0024] The antifreeze synergist prepared in this application is a multi-component copolymer of hydroxyethyl acrylate, 2-acrylamido-2-methylpropanesulfonic acid, and vinylmethyloxazolidinone. Its multi-functional groups synergistically enhance its antifreeze effect. This synergist can construct a uniformly sized and rationally distributed closed pore system within concrete. On the one hand, it provides controllable nucleation sites for water freezing, preventing sudden freezing of supercooled liquids; on the other hand, it buffers the internal stress generated by ice crystal expansion during freeze-thaw cycles, significantly improving the freeze-thaw durability of concrete. The synergistic effect of the compounded polyether monomer and the antifreeze synergist achieves a simultaneous leap in dispersion stability and freeze-thaw durability. The efficient dispersion of the compounded polyether monomer ensures the uniform distribution of the antifreeze synergist within the concrete, while the stable pore structure constructed by the antifreeze synergist further optimizes the interfacial properties within the concrete. The combination of these two not only strengthens the core function of the water-reducing agent but also significantly improves the strength development potential and volume stability of concrete. Detailed Implementation

[0025] The present application will be further described in detail below with reference to the embodiments.

[0026] The methyl allyl polyoxyethylene ether used in the embodiments and comparative examples of this application was purchased from Jiangsu Bosite Chemical Technology Co., Ltd.; isopentenyl polyoxyethylene ether was purchased from Shaoxing Yuzhou Chemical Co., Ltd.; hydroxyethyl acrylate was purchased from Shandong Youwang Chemical Products Co., Ltd.; 2-acrylamide-2-methylpropanesulfonic acid was purchased from Jinan Kaichuang Chemical Co., Ltd.; and vinylmethyl oxazolidinone was purchased from Hubei Henghua Technology Co., Ltd.

[0027] Examples 1-3 provide a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete and its application.

[0028] Example 1

[0029] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early-strength functional monomer, 3 parts antifreeze synergist, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10:5, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0030] The preparation method of the antifreeze synergist includes the following preparation steps:

[0031] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel in a mass ratio of 10:5:3:50 and stirred at 200 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed in a mass ratio of 0.3:10 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 10:1, with a dropwise addition time of 2 hours. During the dropwise addition, the reaction temperature was maintained at 75°C. After the dropwise addition was completed, the reaction was kept at 80°C for 1 hour, then cooled to 35°C, and the pH value was adjusted to 6.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0032] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0033] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0034] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0035] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0036] Example 2

[0037] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 35 parts polyether monomer, 20 parts main chain monomer, 8 parts early-strength functional monomer, 5 parts antifreeze synergist, 3 parts small molecule protective agent, 1 part initiator, 0.5 parts chain transfer agent, and 150 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 11:7, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0038] The preparation method of the antifreeze synergist includes the following preparation steps:

[0039] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel in a mass ratio of 11:7:4:65 and stirred at 300 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed in a mass ratio of 0.5:15 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 11:1.5, with a dropwise addition time of 2.5 h. The reaction temperature was maintained at 80 °C during the dropwise addition. After the dropwise addition was completed, the reaction was kept at 81 °C for 1.3 h, cooled to 38 °C, and the pH value was adjusted to 6.5 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0040] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0041] Step 1: Mix the polyether monomer and 65 parts of deionized water at 300 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist, and 70 parts of deionized water at 300 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 12 parts of deionized water at 300 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 3 parts of deionized water at 300 rpm until homogeneous to obtain a chain transfer agent solution.

[0042] Step 2: Heat the polyether presol to 70°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3.5 h. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.75 h. After the dropwise addition is completed, keep the reaction at 70°C for 2.5 h with a stirring speed of 250 rpm to obtain the polymerization reaction solution.

[0043] Step 3: Cool the polymerization reaction solution to 45°C, add a small molecule protective agent, stir at a constant temperature of 300 rpm for 50 min, adjust the pH value to 8.0 with a 25% sodium hydroxide solution, keep warm for 35 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0044] Example 3

[0045] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 40 parts polyether monomer, 25 parts main chain monomer, 10 parts early strength functional monomer, 8 parts antifreeze synergist, 5 parts small molecule protective agent, 2 parts initiator, 1 part chain transfer agent, and 180 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 12:8, the main chain monomer is acrylic acid, the early strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0046] The preparation method of the antifreeze synergist includes the following preparation steps:

[0047] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel in a mass ratio of 12:8:5:80 and stirred at 400 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed in a mass ratio of 0.8:20 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 12:2, and the addition time was 3 hours. During the addition, the reaction temperature was maintained at 85℃. After the addition was completed, the reaction was kept at 82℃ for 1.5 hours, cooled to 40℃, and the pH value was adjusted to 7.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0048] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0049] Step 1: Mix the polyether monomer and 80 parts of deionized water at a stirring speed of 400 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist, and 80 parts of deionized water at a stirring speed of 400 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 15 parts of deionized water at a stirring speed of 400 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 5 parts of deionized water at a stirring speed of 400 rpm until homogeneous to obtain a chain transfer agent solution.

[0050] Step 2: Heat the polyether presol to 75°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 4 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 2 hours. After the dropwise addition is completed, keep the reaction at 75°C for 3 hours with a stirring speed of 300 rpm to obtain the polymerization reaction solution.

[0051] Step 3: Cool the polymerization reaction solution to 50°C, add a small molecule protective agent, stir at a constant temperature of 400 rpm for 60 min, adjust the pH value to 8.5 with a 30% sodium hydroxide solution, keep warm for 40 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0052] Comparative Example 1

[0053] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early-strength functional monomer, 3 parts antifreeze synergist, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is isopentenyl polyoxyethylene ether, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0054] The preparation method of the antifreeze synergist includes the following preparation steps:

[0055] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel in a mass ratio of 10:5:3:50 and stirred at 200 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed in a mass ratio of 0.3:10 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 10:1, with a dropwise addition time of 2 hours. During the dropwise addition, the reaction temperature was maintained at 75°C. After the dropwise addition was completed, the reaction was kept at 80°C for 1 hour, then cooled to 35°C, and the pH value was adjusted to 6.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0056] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0057] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0058] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0059] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0060] Comparative Example 2

[0061] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early strength functional monomer, 3 parts antifreeze synergist, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is methyl allyl polyoxyethylene ether, the main chain monomer is acrylic acid, the early strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0062] The preparation method of the antifreeze synergist includes the following preparation steps:

[0063] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel in a mass ratio of 10:5:3:50 and stirred at 200 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed in a mass ratio of 0.3:10 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 10:1, with a dropwise addition time of 2 hours. During the dropwise addition, the reaction temperature was maintained at 75°C. After the dropwise addition was completed, the reaction was kept at 80°C for 1 hour, then cooled to 35°C, and the pH value was adjusted to 6.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0064] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0065] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0066] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0067] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0068] Comparative Example 3

[0069] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early-strength functional monomer, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10:5, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0070] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0071] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0072] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0073] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0074] Comparative Example 4

[0075] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early-strength functional monomer, 3 parts antifreeze synergist, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10:5, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0076] The preparation method of the antifreeze synergist includes the following preparation steps:

[0077] Hydroxyethyl acrylate, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel at a mass ratio of 10:8:50 and stirred at 200 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed at a mass ratio of 0.3:10 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, controlling the mass ratio of the monomer mixed aqueous solution to the ammonium persulfate aqueous solution to be 10:1, and the addition time was 2 hours. During the addition, the reaction temperature was maintained at 75°C. After the addition was completed, the reaction was kept at 80°C for 1 hour, cooled to 35°C, and the pH value was adjusted to 6.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0078] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0079] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0080] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0081] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0082] Comparative Example 5

[0083] A chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete comprises the following raw materials in parts by weight: 30 parts polyether monomer, 15 parts main chain monomer, 5 parts early-strength functional monomer, 3 parts antifreeze synergist, 1 part small molecule protective agent, 0.5 parts initiator, 0.1 parts chain transfer agent, and 120 parts deionized water; wherein the polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10:5, the main chain monomer is acrylic acid, the early-strength functional monomer is N-hydroxymethylacrylamide, the small molecule protective agent is hydroxyethyl acrylate, the initiator is ammonium persulfate, and the chain transfer agent is mercaptoacetic acid.

[0084] The preparation method of the antifreeze synergist includes the following preparation steps:

[0085] Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, and deionized water were added to a reaction vessel at a mass ratio of 10:8:50 and stirred at 200 rpm until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed at a mass ratio of 0.3:10 to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution, with the mass ratio of monomer mixed aqueous solution to ammonium persulfate aqueous solution controlled at 10:1. The addition time was 2 hours, and the reaction temperature was maintained at 75℃ during the addition. After the addition was completed, the reaction was kept at 80℃ for 1 hour, cooled to 35℃, and the pH value was adjusted to 6.0 with a 30% sodium hydroxide solution. The mixture was then allowed to cool naturally to room temperature to obtain the antifreeze synergist.

[0086] A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete includes the following preparation steps:

[0087] Step 1: Mix the polyether monomer and 50 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a polyether presol; mix the main chain monomer, early strength functional monomer, antifreeze synergist and 60 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a mixed monomer solution; disperse the initiator in 8 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain an initiator solution; disperse the chain transfer agent in 2 parts of deionized water at a stirring speed of 200 rpm until homogeneous to obtain a chain transfer agent solution.

[0088] Step 2: Heat the polyether presol to 65°C and start adding the mixed monomer solution and initiator solution dropwise simultaneously. The dropwise addition time for both the mixed monomer solution and the initiator solution is 3 hours. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. The dropwise addition time for the chain transfer agent solution is 1.5 hours. After the dropwise addition is completed, keep the reaction at 65°C for 2 hours with a stirring speed of 200 rpm to obtain the polymerization reaction solution.

[0089] Step 3: Cool the polymerization reaction solution to 40°C, add a small molecule protective agent, stir at a constant temperature of 200 rpm for 40 min, adjust the pH value to 7.5 with a 20% sodium hydroxide solution, keep warm for 30 min, and cool to room temperature to obtain a chlorine-free high-performance polycarboxylate superplasticizer.

[0090] Performance testing

[0091] The performance of the antifreeze concrete prepared in Examples 1-3 and Comparative Examples 1-5 was tested using a chlorine-free high-performance polycarboxylate superplasticizer.

[0092] Referring to the national standard GB / T 50080-2016 "Standard for Test Methods of Performance of Ordinary Concrete Mixtures", the working parameters (initial spread, 1-hour spread), air content, and setting time of fresh concrete prepared by polycarboxylate superplasticizers in Examples 1-3 and Comparative Examples 1-5 were determined. The C60 low water-cement ratio concrete mix proportions used are shown in Table 1. Referring to the national standard GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", the compressive strength (7-day and 28-day) of the concrete was determined. The working parameters, air content, setting time, and compressive strength test results of the fresh concrete are shown in Table 2.

[0093] Table 1 Concrete mix proportions (unit: kg / m³) 3 )

[0094]

[0095] Concrete shrinkage performance: Referring to the national standard GB / T 50082-2024 "Standard for Test Methods of Long-term Performance and Durability of Concrete", the shrinkage rate of concrete at 3d, 7d, 14d, 28d and 60d was tested, with the initial setting of concrete as the starting point.

[0096] Freeze-thaw resistance: Concrete standard specimens (100 mm × 100 mm × 400 mm) containing water-reducing agents from Examples 1-3 and Comparative Examples 1-5 were cured for 28 days under standard conditions, then immersed in water at 20 ± 2℃ for 4 days. After being removed and dried, the initial mass and initial dynamic modulus of elasticity were measured. The standard specimens were placed in a rapid freezing apparatus and subjected to a freeze-thaw cycle: the core temperature of the specimen was lowered from 5℃ to -18℃ within 2 hours, and then raised to 5℃ within 1 hour to complete one freeze-thaw cycle. After 300 freeze-thaw cycles, the relative dynamic modulus of elasticity and mass loss rate after freeze-thaw were calculated. The test results are shown in Table 3.

[0097] Table 2 Performance parameters of the polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-5

[0098] Table 3. Shrinkage and freeze resistance of the polycarboxylate superplasticizers prepared in Examples 1-3 and Comparative Examples 1-5

[0099] As shown in Tables 2 and 3, the chlorine-free high-performance polycarboxylate superplasticizer prepared in this application has both strong dispersibility and good slump retention. The initial spread and 1-hour spread of the concrete are high, the air content is moderate, and the setting time is reasonable. It can significantly improve the 7-day and 28-day compressive strength of concrete, greatly reduce the shrinkage rate at all ages, and improve the volume stability of concrete. It has outstanding antifreeze performance. After 300 freeze-thaw cycles, the relative dynamic elastic modulus of the concrete remains high, and the mass loss rate is low. Due to the synergistic effect of the compounded polyether monomer and antifreeze synergist, the product prepared in this application has significantly improved all properties and is suitable for low-temperature concrete engineering applications.

[0100] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete, characterized in that, The raw materials include the following parts by weight: 30-40 parts polyether monomer, 15-25 parts main chain monomer, 5-10 parts early strength functional monomer, 3-8 parts antifreeze synergist, 1-5 parts small molecule protectant, 0.5-2 parts initiator, 0.1-1 parts chain transfer agent, and 120-180 parts deionized water.

2. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The polyether monomer is composed of methyl allyl polyoxyethylene ether and isopentenyl polyoxyethylene ether in a mass ratio of 10-12:5-8.

3. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The main chain monomer is one or more of acrylic acid, methacrylic acid, and maleic anhydride.

4. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The early-strength functional monomer is one or more of hydroxypropyl methacrylate, acrylamide, and N-hydroxymethylacrylamide.

5. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The preparation method of the antifreeze synergist includes the following preparation steps: Hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyl oxazolidinone, and deionized water were added to a reaction vessel and stirred until homogeneous to obtain a monomer mixed aqueous solution. Ammonium persulfate and deionized water were mixed until homogeneous to obtain an ammonium persulfate aqueous solution. The ammonium persulfate aqueous solution was added dropwise to the monomer mixed aqueous solution. After the addition was complete, the reaction was kept at a constant temperature for 1-1.5 hours, then cooled to 35-40℃, the pH was adjusted to 6.0-7.0, and the mixture was allowed to cool naturally to room temperature to obtain an antifreeze synergist.

6. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 5, characterized in that, The mass ratio of hydroxyethyl acrylate, 2-acrylamide-2-methylpropanesulfonic acid, vinylmethyloxazolidinone and deionized water is 10-12:5-8:3-5:50-80.

7. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The small molecule protective agent is one of acrylate or acrylamide sulfonic acid.

8. The chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete according to claim 1, characterized in that, The initiator is ammonium persulfate and / or potassium persulfate; the chain transfer agent is mercaptoacetic acid and / or mercaptopropionic acid.

9. A method for preparing a chlorine-free high-performance polycarboxylate superplasticizer for frost-resistant concrete as described in any one of claims 1-8, characterized in that, The preparation steps include the following: Step 1: Stir the polyether monomer and deionized water evenly to obtain a polyether presol; stir the main chain monomer, early strength functional monomer, antifreeze synergist and deionized water evenly to obtain a mixed monomer solution; disperse the initiator evenly with deionized water to obtain an initiator solution; disperse the chain transfer agent evenly with deionized water to obtain a chain transfer agent solution. Step 2: Heat the polyether presol to 65-75℃ and start adding the mixed monomer solution and initiator solution dropwise simultaneously. When half of the mixed monomer solution has been added, start adding the chain transfer agent solution dropwise. After the addition is complete, keep the temperature constant for 2-3 hours to obtain the polymerization reaction solution. Step 3: Cool the polymerization reaction solution to 40-50℃, add the small molecule protective agent, stir at a constant temperature, adjust the pH value to 7.5-8.5, keep warm for 30-40 minutes, cool to room temperature, and obtain the chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete.

10. An application of the chlorine-free high-performance polycarboxylate superplasticizer for antifreeze concrete as described in any one of claims 1-8, characterized in that, The specific application method is as follows: the water-reducing agent is added to the concrete at 0.1-0.2% of the concrete mass for use in concrete construction of buildings, water conservancy, and transportation projects under negative temperature environments.

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