Mud-resistant water-retention polycarboxylic acid water reducing agent for coal gangue concrete and preparation method of mud-resistant water-retention polycarboxylic acid water reducing agent

Abstract

The invention belongs to the field of concrete admixtures, and particularly relates to a mud-resistant water-retention polycarboxylic acid water reducing agent for coal gangue concrete and a preparation method of the mud-resistant water-retention polycarboxylic acid water reducing agent. The water reducing agent is prepared from a main monomer isoprenyloxy polyethylene glycol ether, comonomers of hydroxyethyl methylacrylate and maleic anhydride and a crosslinking monomer of trimethylolpropane trimethacrylate as raw materials through a microwave hydrothermal assisted free radical polymerization method under the action of an initiator and a chain transfer agent. The preparation method comprises the following steps: firstly, preparing an initiator solution A, a monomer solution B and a solution C obtained by fully dissolving isoprenyloxy polyethylene glycol ether; dropwise adding the initiator solution A and the monomer solution B into the solution C under a microwave condition; according to the preparation method disclosed by the invention, the mud-resistant and water-retention type polycarboxylic acid water reducing agent is prepared by introducing the isoprenyloxy polyethylene glycol ether, the maleic anhydride, the hydroxyethyl methylacrylate and the trimethylolpropane trimethacrylate, and the water reducing agent is difficult to enter a coal gangue clay lamella, so that mud resistance and water retention are realized.

Description

Technical Field

[0001] This invention belongs to the field of concrete admixture technology, specifically relating to an anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete and its preparation method. Background Technology

[0002] Coal gangue is an industrial solid waste generated during coal mining and washing. Currently, there are methods to use coal gangue as an industrial solid waste to replace natural aggregates in concrete preparation, for reinforcing and filling cavities in coal mine goafs and old workings, thus realizing the resource utilization of coal gangue. Coal gangue is mainly composed of clay minerals (such as montmorillonite and illite), quartz, calcite, and other minerals. It has a high content of clay minerals, which have a layered structure and a large specific surface area. This layered structure strongly adsorbs traditional polycarboxylate superplasticizer molecules, leading to the large consumption of the superplasticizer's effective components. This results in poor concrete fluidity, rapid slump loss, and bleeding segregation, severely restricting its engineering applications. Existing anti-mud properties improvement technologies mainly involve molecular structure modification (such as introducing more anionic groups to enhance electrostatic repulsion) or compounding clay inhibitors (such as sodium gluconate, sodium citrate, etc.). However, the former can lead to excessive anionization of water-reducing agent molecules, resulting in saturation of electrostatic repulsion when interacting with cement particles and a decrease in dispersion efficiency. The latter only alleviates the influence of clay through competitive adsorption, without fundamentally solving the problem of clay preferentially adsorbing water-reducing agents, and its compatibility with cement and aggregates is easily affected by raw material fluctuations.

[0003] Traditional polycarboxylate superplasticizer synthesis processes rely on conventional heating methods (such as water bath heating), which have low reaction efficiency (requiring 2-3 hours), high energy consumption, and difficulty in achieving both anti-mud properties and water retention.

[0004] Therefore, there is a need to provide an improved technical solution that addresses the shortcomings of the existing technology. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of the prior art and provide a mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete and its preparation method.

[0006] To achieve the above objectives, the present invention provides the following technical solution: A mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete is prepared by microwave hydrothermal assisted free radical polymerization using isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA) as raw materials, under the action of an initiator and a chain transfer agent. The isopreneoxy polyethylene glycol ether (IPEG) and hydroxyethyl methacrylate (HEMA) are used as raw materials. A) The mass ratio of maleic anhydride (MAH) and trimethylolpropane trimethacrylate (TMPTA) is 1:(0.10~0.15):(0.03~0.05):(0.003~0.005); the total mass of monomers refers to the total mass of the four substances: the main monomer isopreneoxy polyethylene glycol ether (IPEG), the comonomer hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and the crosslinking monomer trimethylolpropane trimethacrylate (TMPTA).

[0007] Furthermore, the isopreneoxy polyethylene glycol ether (IPEG) has a molecular weight of 2000-4000.

[0008] Furthermore, the amounts of the initiator and chain transfer agent are 0.08% to 0.12% of the total mass of the monomers, respectively.

[0009] This invention also proposes a method for preparing the aforementioned anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete, comprising the following steps: S1. Dissolve the initiator in deionized water according to the specified ratio to prepare initiator solution A; S2. Prepare monomer solution B by dissolving the comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and chain transfer agent in deionized water in a certain proportion; S3. Add isopreneoxy polyethylene glycol ether (IPEG) and deionized water to a microwave reactor in a certain proportion. After heating, stir to fully dissolve the isopreneoxy polyethylene glycol ether (IPEG) to obtain solution C. S4. Under microwave conditions, initiator solution A and monomer solution B are added dropwise to solution C, and trimethylolpropane trimethacrylate (TMPTA) is added rapidly within 4 to 10 minutes after the start of the dropwise addition. S5. After the polymerization reaction in the microwave reactor is completed, cool to room temperature, adjust the pH to 6.5~7.0 with an alkaline solution, stir evenly, and obtain the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete.

[0010] Furthermore, in S1, the initiator is potassium persulfate (KPS), and potassium persulfate (KPS) and deionized water are mixed at a mass ratio of (0.5~1.5):5000 to prepare initiator solution A; in S2, the comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), chain transfer agent and deionized water are mixed at a mass ratio of (0.10~0.15):(0.03~0.05):(0.10~0.15):1 to prepare monomer solution B; in S3, the mass ratio of isopreneoxy polyethylene glycol ether (IPEG) to deionized water is (2.5~3.5):1.

[0011] Furthermore, in S4, the dropping rate of initiator solution A is 0.143 ml / min to 0.2 ml / min, and the dropping rate of monomer solution B is 1.667 ml / min to 2.5 ml / min; and trimethylolpropane trimethacrylate (TMPTA) is rapidly added within the initial 4 to 6 min time range.

[0012] Furthermore, in S4, trimethylolpropane trimethacrylate (TMPTA) accounts for 0.25% to 0.35% of the total monomer mass.

[0013] Furthermore, in S4, the power of the microwave reactor is 450~750W, the microwave hydrothermal reaction temperature is 85℃~95℃, and the reaction time is 30~60min.

[0014] Furthermore, the molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) in the monomer solution B is (2.5~3.5):1.

[0015] Furthermore, the alkaline solution is one or both of sodium hydroxide solution and potassium hydroxide solution, and the concentration of the alkaline solution is 25~35wt%.

[0016] The beneficial effects of this invention are: This invention constructs a three-dimensional cross-linked network by introducing rigid branches of isopreneoxy polyethylene glycol ether (IPEG). Its physical size (approximately 2.5~3.0 nm) is significantly larger than the interlayer spacing of coal gangue clay (approximately 1.2~1.5 nm), thereby directly blocking the embedding of water-reducing agent molecules into clay layers and reducing the ineffective adsorption rate.

[0017] This invention introduces the anhydride group (-CO-O-CO-) of maleic anhydride (MAH) and the clay surface cation (Ca) 2+ 、Al 3+ This forms a strong electrostatic repulsion force, which further inhibits clay adsorption and significantly improves the initial fluidity and slump retention rate of concrete.

[0018] In this invention, the hydroxyl groups (-OH) of hydroxyethyl methacrylate (HEMA) form a "dynamic water film" with water molecules through hydrogen bonds. Combined with the slow-release effect of the cross-linked network pores, this reduces bleeding rate and improves slump retention. Simultaneously, the cross-linked monomer trimethylolpropane trimethacrylate (TMPTA) undergoes controlled hydrolysis (slow release) of its ester bonds in an alkaline environment, gradually releasing polyethylene glycol ether (PEG) segments, dynamically adsorbing free water, and achieving long-term maintenance of slurry consistency.

[0019] In terms of preparation method, a microwave hydrothermal method is adopted, which significantly reduces polymerization energy consumption, greatly improves reaction efficiency, and significantly enhances molecular chain uniformity. Furthermore, dodecyl mercaptan (DDT) is used as a chain transfer agent to precisely control the polymerization process, ensuring a dense cross-linked network structure, significantly improving the uniformity of concrete slurry, and reducing segregation rate. Compared with traditional water bath heating (reaction time 2-3 hours), this invention shortens the reaction time to within 1 hour, reducing both reaction time and energy consumption. Detailed Implementation

[0020] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art are within the scope of protection of the present invention.

[0021] A mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete is prepared by microwave hydrothermal assisted free radical polymerization using isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA) as raw materials, under the action of an initiator and a chain transfer agent. The isopreneoxy polyethylene glycol ether (IPEG) and hydroxyethyl methacrylate (HEMA) are used as raw materials. A) The mass ratio of maleic anhydride (MAH) and trimethylolpropane trimethacrylate (TMPTA) is 1:(0.10~0.15):(0.03~0.05):(0.003~0.005); the total mass of monomers refers to the total mass of the four substances: the main monomer isopreneoxy polyethylene glycol ether (IPEG), the comonomer hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and the crosslinking monomer trimethylolpropane trimethacrylate (TMPTA).

[0022] Furthermore, the isopreneoxy polyethylene glycol ether (IPEG) has a molecular weight of 2000-4000, preferably 2000-2500. Low molecular weight IPEG diffuses quickly and can rapidly adsorb onto the surface of cement particles. High molecular weight IPEG is highly flexible, but its cross-linked network has excessively large pores, allowing moisture to escape easily. Moreover, high molecular weight IPEG is more expensive, which is detrimental to reducing raw material costs.

[0023] Furthermore, the amounts of the initiator and chain transfer agent are 0.08% to 0.12% (e.g., 0.08%, 0.09%, 0.1%, 0.11%, 0.12%) of the total monomer mass. Preferably, the amounts of the initiator and chain transfer agent are 0.1% of the total monomer mass.

[0024] This invention also proposes a method for preparing the aforementioned anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete, comprising the following steps: S1. Prepare initiator solution A by mixing initiator and deionized water at a mass ratio of (0.5~1.5):5000; S2. Mix the comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), chain transfer agent, and deionized water in a mass ratio of (0.10~0.15):(0.03~0.05):(0.10~0.15):1 to prepare monomer solution B; S3. Add isopreneoxy polyethylene glycol ether (IPEG) and deionized water at a mass ratio of (2.5~3.5):1 to a microwave reactor. After heating, stir to fully dissolve the isopreneoxy polyethylene glycol ether (IPEG) to obtain solution C. S4. Under microwave conditions, initiator solution A and monomer solution B are added dropwise to solution C. The dropwise addition rate of initiator solution A is 0.143 ml / min to 0.2 ml / min, and the dropwise addition rate of monomer solution B is 1.667 ml / min to 2.5 ml / min. Trimethylolpropane trimethacrylate (TMPTA) is added rapidly within 4 to 10 minutes after the start of the addition. S5. After the polymerization reaction in the microwave reactor is completed, cool to room temperature, adjust the pH to 6.5~7.0 with an alkaline solution, stir evenly, and obtain a mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete; the alkaline solution is one or both of sodium hydroxide solution and potassium hydroxide solution, and the concentration of the alkaline solution is 25~35wt%. Since the concentration of the alkaline solution is high, only a small amount (a few drops) is needed, and its effect on the solution volume in the microwave reactor can be ignored.

[0025] Preferably, in step S4, trimethylolpropane trimethacrylate (TMPTA) is rapidly added within the initial 4-6 min time range. Note that the addition cannot be completed within 1 min, 2 min, or 3 min; it must be added during the continuous 4-6 min dropwise (e.g., 4 min, 4.5 min, 5 min, 5.5 min, 6 min). This is because the free radical concentration is insufficient at 1-3 minutes, easily forming a loose network and increasing the water exudation rate. Adding TMPTA too early will cause TMPTA to self-crosslink into microgels, destroying water retention and hindering main chain polymerization.

[0026] The mass ratio of isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA) is 1:(0.10~0.15):(0.03~0.05):(0.003~0.005). Calculations show that the mass of TMPTA accounts for 0.249%~0.441% (approximately 0.25%~0.44%) of the total monomer mass. Preferably, in S4, the mass of TMPTA accounts for 0.25%~0.35% of the total monomer mass, resulting in more complete cement hydration and higher 28-day compressive strength.

[0027] Preferably, in S4, the power of the microwave reactor is 450~750W, the microwave hydrothermal reaction temperature is 85℃~95℃, and the reaction time is 30~60min.

[0028] After conversion, the molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) in monomer solution B is (1.51~3.77):1. Preferably, the molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) in monomer solution B is (2.5~3.5):1, which enhances the synergistic effect of electrostatic repulsion and hydrogen bonding water locking, improving initial fluidity and reducing bleeding rate. Preferably, the molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) in monomer solution B is 3:1.

[0029] The following examples and comparative examples illustrate this in detail. In the examples and comparative examples below, the purity of each chemical raw material used is analytical grade or higher, and the molecular weight of isopreneoxy polyethylene glycol ether (IPEG) is 2100.

[0030] Example 1 A type of anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete, the preparation method of which includes the following steps: S1. Dissolve 0.292g KPS in 29.2g deionized water to prepare initiator solution A. Total mass: 29.492g; S2. The comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and dodecyl mercaptan (DDT) were mixed in a certain mass ratio and dissolved in 290.00 g of deionized water to prepare monomer solution B; the mass of hydroxyethyl methacrylate (HEMA) was 31.25 g, the mass of maleic anhydride (MAH) was 10.00 g, the mass of dodecyl mercaptan (DDT) was 0.32 g, and the total mass of monomer solution B was 362.50 g. S3. Add 250g of isopreneoxy polyethylene glycol ether (IPEG) and 83.3g of deionized water to a microwave reactor. Set the microwave power to 600W, heat to 92℃, and stir to dissolve to obtain solution C. The mass of isopreneoxy polyethylene glycol ether (IPEG) is 249.96g (250g can be weighed). S4. Under microwave conditions, add solution A to solution C at a constant rate of 3 h using a peristaltic pump, and simultaneously add solution B to solution C at a constant rate of 2.5 h. Add 1.00 g of trimethylolpropane trimethacrylate (TMPTA) rapidly about 5 min after the initial dropwise addition. Maintain the temperature of the microwave reactor at 92 °C and the reaction time is 45 min. S5. After the polymerization reaction in the microwave reactor is completed, cool to room temperature, adjust the pH to 6.5~7.0 with 30wt% NaOH solution, stir evenly, and obtain the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete.

[0031] In this embodiment, in initiator solution A, the amount of initiator KPS is approximately 0.1% of the total monomer mass; in monomer solution B, the mass ratio of hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), chain transfer agent, and deionized water is 0.11:0.03:0.11:1. The amount of dodecyl mercaptan (DDT) is 0.11% of the total monomer mass. In step S4, the mass ratio of isopreneoxy polyethylene glycol ether (IPEG) to deionized water is 3:1, the dropping rate of initiator solution A is approximately 0.164 ml / min, and the dropping rate of monomer solution B is approximately 2.417 ml / min. In step S4, the mass of trimethylolpropane trimethacrylate (TMPTA) is 0.342% of the total monomer mass. The molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) is 2.35:1.

[0032] Sample preparation: The anti-mud and water-retaining polycarboxylate superplasticizer prepared in Example 1 was applied to the coal gangue concrete, with a superplasticizer dosage of 0.2%; the cement used in the coal gangue concrete was ordinary Portland 42.5 cement (PO42.5), the water-cement ratio was 0.29, and the coal gangue content was 15%.

[0033] The composition of the coal gangue concrete and the dosage of each water-reducing agent used in the other embodiments and comparative examples are the same as in Example 1.

[0034] Examples 2-5 only changed the microwave heating power or reaction time (holding time). Here, we will only explain the differences between them and Example 1: Example 2: Microwave power is set to 450W.

[0035] Example 3: Microwave power is set to 750W.

[0036] Example 4: The reaction time was set to 30 min.

[0037] Example 5: The reaction time was set to 60 min.

[0038] Comparative Example 1 Compared to Example 1, Comparative Example 1 used the same raw material composition, with the only difference in the preparation process being the heating method: Comparative Example 1 uses traditional water bath heating with a water bath power of 600W and a water bath heat preservation time of 3 hours.

[0039] Comparative Examples 2-4 used commercially available water-reducing agents: Comparative Example 2: A traditional water-reducing agent produced by Sichuan Dongrun Baisheng New Material Co., Ltd., product model JS04240520015.

[0040] Comparative Example 3: Anti-mud type water-reducing agent produced by Sichuan Dongrun Baisheng New Material Co., Ltd., product model JS04240520019.

[0041] Comparative Example 4: Water-retaining water-reducing agent produced by Sichuan Dongrun Baisheng New Material Co., Ltd., product model JS07240520022.

[0042] Comparative Examples 5-8 are identical to Example 1 in terms of raw materials and preparation process, except that they lack a certain component. Comparative Example 5: No isopreneoxy polyethylene glycol ether (IPEG) was added to the raw materials.

[0043] Comparative Example 6: Maleic anhydride (MAH) was not added to the raw materials.

[0044] Comparative Example 7: No hydroxyethyl methacrylate (HEMA) was added to the raw materials.

[0045] Comparative Example 8: No trimethylolpropane trimethacrylate (TMPTA) was added to the raw materials.

[0046] The test results of the above embodiments and comparative examples are shown in Tables 1, 2 and 3. Table 1 focuses on the performance comparison between microwave process and traditional process, Table 2 focuses on the comparison of pulp fluidity, slump retention rate and compressive strength, and Table 3 focuses on the verification of component synergistic effect.

[0047] Table 1. Test results of coal gangue concrete in Examples 1-5 and Comparative Example 1.

[0048] When microwaves irradiate an object, the microwave energy can be absorbed by materials with high dielectric constants and then rapidly converted into heat. This accelerates the chemical reaction while simultaneously heating the object itself quickly, significantly reducing pretreatment time. It achieves the same effect with only a fraction of the energy consumed by traditional thermal heating methods. Furthermore, water has a high dielectric constant of 77.0, resulting in strong microwave absorption. Table 1 shows that compared to traditional water bath heating, microwave heating has advantages such as high efficiency and fast heating speed. The segregation rate of coal gangue concrete using the water-reducing agents in Examples 1-5 is less than the 3.5% of Comparative Example 1. Compared to Comparative Example 1, Examples 1-5 show that the microwave process reduces energy consumption by 26.7% to 46.7% and increases reaction efficiency by 2.5 to 6 times. At a microwave power of 600W, energy consumption was lowest (0.40kWh / kg, 0.45kWh / kg). Excessive power (750W) could lead to localized overheating and molecular chain breakage. A lower segregation rate is better, but at too low a power (450W), the polymerization reaction might be incomplete, resulting in poor water-reducing agent synthesis. In both cases, the segregation rate slightly increased, but remained lower than that of the traditional water bath method. The segregation rate was lowest (1.2%) when the microwave heating time was 45min, as microwave heating resulted in more uniform cross-linking of the molecular chains, leading to optimal stability of the concrete slurry. At a microwave heating time of 30min, the polymerization reaction was incomplete, the molecular chains were loose, and the segregation rate increased to 2.0%. At a microwave heating time of 60min, side reactions (such as chain breakage) might occur, and the segregation rate slightly increased back to 1.5%. Meanwhile, energy consumption increased linearly with reaction time, but the total energy consumption of all examples using microwave technology was still significantly lower than that of the traditional process (Comparative Example 1).

[0049] Table 2. Test results of coal gangue concrete in Example 1 and Comparative Examples 2-4

[0050] As shown in Table 2, the 2-hour flow retention rates of the coal gangue concrete in Examples 1, 2, 3, and 4 were 89.3%, 71.4%, 79.2%, and 73.9%, respectively. Compared with the traditional water-reducing agent in Comparative Example 2, the water-reducing agent of this invention improved the initial flowability by 33%, and the 120-minute flowability retention rate reached 89.3% (compared to 71.4% for the traditional agent). The 2-hour slump retention rate was significantly better than that of commercially available products (Comparative Examples 2-4), demonstrating long-term slump retention. The 28-day compressive strength of the water-reducing agent of this invention reached 52.8 MPa, which is 17% higher than that of the traditional product (Comparative Example 2). The improvement in compressive strength is due to the optimized water retention reducing internal porosity, thereby increasing the density of the coal gangue concrete.

[0051] Table 3. Test results of coal gangue concrete in Examples 5-8 and Comparative Examples 5-8

[0052] Table 3 shows that the 2-hour flow retention rates of the coal gangue concrete in Examples 1 and Comparative Examples 5-8 were 89.3%, 85.1%, 84.0%, 83.0%, and 85.2%, respectively. Compared with the water-reducing agent of the present invention, when isopreneoxy polyethylene glycol ether (IPEG) was missing (Comparative Example 5), the initial flowability decreased by 16%, and the anti-mud properties were significantly reduced. When maleic anhydride (MAH) was missing (Comparative Example 6), electrostatic repulsion failed, and the initial flowability decreased by 12%. This may be because the failure of electrostatic repulsion allowed the clay to resume preferential adsorption of the water-reducing agent. When hydroxyethyl methacrylate (HEMA) was missing (Comparative Example 7), a dynamic water film could not be formed, and the bleeding rate increased to 1.2%; when trimethylolpropane trimethacrylate (TMPTA) was missing (Comparative Example 8), the slow-release water retention failed, and the bleeding rate reached 2.5%. The above comparison shows that isopreneoxy polyethylene glycol ether (IPEG), trimethylolpropane trimethacrylate (TMPTA), hydroxyethyl methacrylate (HEMA), and maleic anhydride (MAH) all contribute to the effectiveness of the water-reducing agent in this invention and are indispensable.

[0053] In this invention, isopreneoxy polyethylene glycol ether (IPEG) serves as the main monomer, providing a sterically hindered framework. Its rigid branch length (approximately 2.5~3.0 nm) is significantly greater than the interlayer spacing of coal gangue clay sheets (1.2~1.5 nm). This size directly prevents water-reducing agent molecules from embedding into the clay sheets, reducing ineffective adsorption. Hydroxyethyl methacrylate (HEMA) and maleic anhydride (MAH) are comonomers, introducing hydroxyl and carboxyl groups respectively. The hydroxyl group (-OH) of HEMA forms a dynamic water film with water molecules through hydrogen bonds, covering the surface of cement particles. This water film reduces free water migration through pore-mediated slow release, lowering the bleeding rate to 0.8%. The anhydride group (-CO-O-CO-) of MAH hydrolyzes to carboxylate (-COO⁻) in an alkaline environment, reacting with Ca on the clay surface.2+ 、Al 3+ A strong electrostatic repulsion is formed. Trimethylolpropane trimethacrylate (TMPTA) is a cross-linked monomer that constructs a network structure. In an alkaline environment, its ester bonds gradually hydrolyze, releasing polyethylene glycol ether (PEG) segments, which dynamically adsorb free water. Therefore, the size barrier of IPEG, the electrostatic shielding of MAH, the dynamic water film of HEMA, and the slow-release water retention of TMPTA work synergistically to achieve a dual breakthrough in anti-mud and water retention.

[0054] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention shall be within the scope of protection of the pending claims of the present invention.

Claims

1. A mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete, characterized in that: It is prepared by microwave hydrothermal assisted free radical polymerization using isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA) and maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA) as raw materials, under the action of an initiator and a chain transfer agent. The mass ratio of isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA) is 1:(0.10~0.15):(0.03~0.05):(0.003~0.005). The total mass of monomers refers to the total mass of the four substances: isopreneoxy polyethylene glycol ether (IPEG), hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and trimethylolpropane trimethacrylate (TMPTA).

2. The anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 1, characterized in that: The isopreneoxy polyethylene glycol ether (IPEG) has a molecular weight of 2000~4000.

3. The anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 1, characterized in that: The amounts of the initiator and chain transfer agent are 0.08% to 0.12% of the total mass of the monomers, respectively.

4. A method for preparing a mud-resistant and water-retaining polycarboxylate superplasticizer for coal gangue concrete as described in any one of claims 1 to 3, characterized in that, Includes the following steps: S1. Dissolve the initiator in deionized water according to the specified ratio to prepare initiator solution A; S2. Prepare monomer solution B by dissolving the comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), and chain transfer agent in deionized water in a certain proportion; S3. Add isopreneoxy polyethylene glycol ether (IPEG) and deionized water to a microwave reactor in a certain proportion. After heating, stir to fully dissolve the isopreneoxy polyethylene glycol ether (IPEG) to obtain solution C. S4. Under microwave conditions, initiator solution A and monomer solution B are added dropwise to solution C, and trimethylolpropane trimethacrylate (TMPTA) is added rapidly within 4 to 10 minutes after the start of the dropwise addition. S5. After the polymerization reaction in the microwave reactor is completed, cool to room temperature, adjust the pH to 6.5~7.0 with an alkaline solution, stir evenly, and obtain the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete.

5. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: In S1, the initiator is potassium persulfate (KPS), and initiator solution A is prepared by mixing potassium persulfate (KPS) and deionized water at a mass ratio of (0.5~1.5):5000; in S2, monomer solution B is prepared by mixing comonomers hydroxyethyl methacrylate (HEMA), maleic anhydride (MAH), chain transfer agent and deionized water at a mass ratio of (0.10~0.15):(0.03~0.05):(0.10~0.15):1; in S3, the mass ratio of isopreneoxy polyethylene glycol ether (IPEG) to deionized water is (2.5~3.5):

1.

6. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: In S4, the dropping rate of initiator solution A is 0.143 ml / min to 0.2 ml / min, and the dropping rate of monomer solution B is 1.667 ml / min to 2.5 ml / min; and trimethylolpropane trimethacrylate (TMPTA) is rapidly added within the initial 4 to 6 min time range.

7. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: In S4, trimethylolpropane trimethacrylate (TMPTA) accounts for 0.25% to 0.35% of the total monomer mass.

8. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: In S4, the power of the microwave reactor is 450~750W, the microwave hydrothermal reaction temperature is 85℃~95℃, and the reaction time is 30~60min.

9. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: The molar ratio of hydroxyethyl methacrylate (HEMA) to maleic anhydride (MAH) in monomer solution B is (2.5~3.5):

1.

10. The preparation method of the anti-mud and water-retaining polycarboxylate superplasticizer for coal gangue concrete according to claim 4, characterized in that: The alkaline solution is one or both of sodium hydroxide solution and potassium hydroxide solution, and the concentration of the alkaline solution is 25~35wt%.

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