Self-flowing densified cement-free refractory castable and its preparation process

Abstract

The application relates to the field of amorphous refractory materials, and particularly discloses a self-flowing densification cement-free refractory castable and a preparation process thereof. The self-flowing densification cement-free refractory castable comprises aggregates, a binder, an additive, a modified water reducing agent and water. The preparation method of the modified water reducing agent comprises the following steps: adding methyl acryloyloxyethyl phosphate aqueous solution, methoxy polyethylene glycol acrylate, acrylic acid, methyl acryloyloxypropyl trimethoxysilane and mercaptoacetic acid into water to obtain A liquid; adding ammonium persulfate and ammonium bisulfite into water and uniformly mixing to obtain B liquid; adding water into a reaction container, heating, simultaneously dropping the A liquid and the B liquid into the reaction container, continuing to react after dropping is completed, cooling, adjusting pH by using triethanolamine to obtain the modified water reducing agent. The refractory castable has excellent self-flowing forming, high-density structure and high-temperature slag erosion resistance.

Description

Technical Field

[0001] This application relates to the field of unshaped refractory materials, and more specifically, to self-flowing, densified, cement-free refractory castables and their preparation process. Background Technology

[0002] Refractory castables are monolithic refractory materials composed of refractory aggregates, powders, binders, and admixtures mixed in specific proportions. After adding water or other liquids and stirring, they form a fluid mixture that can be applied by pouring, vibration, or gravity flow. After curing and baking, they form a monolithic lining with good strength and high-temperature resistance. However, traditional cement-bonded refractory castables suffer from problems such as a high calcium content in the binder system, leading to an excess of low-melting-point phases at high temperatures, insufficient material density, poor fluidity at room temperature, and short service life.

[0003] Therefore, there is an urgent need for a cement-free refractory castable to achieve self-flowing molding, high-density structure, and high-temperature resistance and slag corrosion resistance, so as to meet the application requirements of high-temperature equipment linings in industries such as metallurgy, chemical industry, and power. Summary of the Invention

[0004] In order to improve the self-flowing molding, high-density structure and high-temperature resistance and slag corrosion resistance of refractory castables, this application provides a self-flowing, densified cementless refractory castable and its preparation process.

[0005] Firstly, the self-flowing, densified, cement-free refractory castable provided in this application adopts the following technical solution: Self-flowing, densified, cement-free refractory castable comprises the following raw materials in parts by weight: 70-80 parts aggregate, 5-8 parts binder, 0.5-2 parts admixture, 0.5-1 part modified water-reducing agent, and 5-8 parts water; The preparation method of the modified water-reducing agent includes the following steps: (1) Add aqueous solution of methacryloyloxyethyl phosphate, methoxy polyethylene glycol acrylate, acrylic acid, methacryloyloxypropyltrimethoxysilane and mercaptoacetic acid to water to prepare solution A; (2) Add ammonium persulfate and ammonium bisulfite to water, mix well, and prepare solution B; (3) Add water to the reaction vessel and heat it to 50-55℃. Add solution A and solution B dropwise to the reaction vessel at the same time. After the addition is complete, keep the temperature at 50-55℃ and continue the reaction for 2 hours. Cool down to the standard ambient temperature and adjust the pH to 5.0-5.5 with triethanolamine to obtain the modified water-reducing agent.

[0006] By adopting the above technical solution, at room temperature, the modified water-reducing agent plays a core dispersing role, breaking up agglomeration by reducing interparticle forces and laying the foundation for system fluidity; the binder forms a preliminary bond with the aggregate, preventing the dispersed particles from agglomerating again, balancing fluidity and formability; the admixture further synergistically regulates the system state, optimizing the dispersion effect and the binder curing process; the components work together to give the castable good self-flowability, allowing it to be uniformly filled and densely formed without external vibration, creating a highly dense structure and reducing internal porosity and defects. At high temperatures, the aggregate and binder synergistically construct a high-temperature stable overall framework, densifying the matrix and improving the interfacial bonding strength, preventing interface weakening and spalling; at room temperature, the water-reducing agent forms a highly dense structure, effectively reducing porosity defects at high temperatures to hinder slag corrosion penetration, thereby improving the material's high-temperature resistance and slag corrosion resistance.

[0007] Methacryloxyethyl phosphate introduces a strongly polar anchoring group, forming strong coordination bonds and hydrogen bonds with the surface of inorganic powders, significantly improving adsorption strength. Methoxy polyethylene glycol acrylate provides flexible polyoxyethylene side chains, achieving efficient dispersion of powder particles through steric hindrance and reducing system viscosity. The carboxyl groups of acrylic acid and phosphate groups form a dual anchoring synergy, further enhancing the adsorption stability of the dispersant on the powder surface. The silane groups of methacryloxypropyltrimethoxysilane undergo partial hydrolysis and condensation in the system, forming Si-O covalent bonds with the hydroxyl groups on the powder surface, while simultaneously constructing a cross-linked network structure between dispersant molecules. Under the precise control of molecular weight and distribution by the mercaptoacetic acid chain transfer agent, the above four types of functional monomers form a molecular framework with multi-group synergistic anchoring and efficient dispersion of flexible side chains. The ammonium persulfate-ammonium bisulfite low-temperature initiation system effectively protects the integrity of the functional groups, enabling the dispersant to achieve self-flowing molding and high-density stacking of powder slurry with low dosage. In high-temperature slag-corrosion environments, the phosphorus-containing components in the modified water-reducing agent decompose and transform into a highly active phosphate phase, which is uniformly distributed in the matrix. This phase reacts with metal cations in the slag to form a dense, high-melting-point phosphate protective layer, effectively preventing the slag from penetrating and eroding the substrate. Simultaneously, the nano-silica produced by the decomposition of the silane components fills matrix pores and optimizes interfacial bonding, further enhancing the material's density. The efficient dispersion of the water-reducing agent at room temperature enables the slurry to achieve tight particle packing after molding, significantly reducing the initial porosity of the substrate. This, combined with the slag-corrosion-resistant barrier formed at high temperatures, ultimately achieves a balance between self-flowability, dense molding, and high-temperature slag-corrosion resistance.

[0008] Optionally, the aggregate is composed of fused dense corundum, tabular corundum fine powder and silicon carbide fine powder in a mass ratio of 1:0.5-1:2.

[0009] Optionally, the electrofused dense corundum has a particle size of 1-10 mm, the tabular corundum fine powder has a particle size of 0.074-1 mm, and the silicon carbide fine powder has a particle size of 0-0.074 mm.

[0010] Optionally, the binder is composed of active α-Al2O3 micro powder, active SiO2 micro powder and magnesium aluminum spinel micro powder in a mass ratio of 1:0.5-0.8:0.5-1.5.

[0011] Optionally, the additive consists of sodium citrate and sodium tripolyphosphate in a mass ratio of 1:1-2.

[0012] Secondly, this application provides a method for preparing self-flowing, densified, cement-free refractory castable, using the following technical solution: The preparation method of self-flowing, densified, cement-free refractory castable includes the following steps: Aggregates, binders, and additives are mixed evenly, and modified water-reducing agent and water are added for wet mixing. The mixture is poured into a mold, sealed and cured for 20-24 hours, demolded, dried, and sintered to obtain a self-flowing, dense, cement-free refractory castable.

[0013] Optionally, the drying temperature range is 100-110℃, the holding time is 20-24h, and the heating rate is 0.5-1℃ / min; the sintering temperature range is 1200-1330℃, the holding time is 3-4h, and the heating rate is 2-5℃ / min.

[0014] In summary, this application has the following beneficial effects: 1. This application utilizes a modified water-reducing agent that breaks up agglomeration by reducing interparticle forces, thus establishing a foundation for fluidity. The binder forms a preliminary bond with the aggregate, preventing re-agglomeration and balancing flowability and molding. Admixtures synergistically optimize the dispersion and curing process. The combination of components enables the castable to possess self-flowability, allowing for uniform filling and dense molding without vibration, forming a highly dense structure and reducing internal porosity and defects. At high temperatures, the aggregate and binder synergistically construct a stable overall framework, densifying the matrix and enhancing interfacial bonding strength, preventing interface weakening and spalling. At room temperature, the water-reducing agent disperses to form a highly dense structure, effectively reducing porosity defects at high temperatures to hinder slag corrosion penetration, thereby improving the material's high-temperature resistance and slag corrosion resistance.

[0015] 2. In the preparation of the modified water-reducing agent, this application utilizes four monomers—methacryloyloxyethyl phosphate, methoxy polyethylene glycol acrylate, acrylate carboxyl group, and methacryloyloxypropyltrimethoxysilane—to form a molecular framework with multi-group synergistic anchoring and flexible side chain dispersion under the precise control of a chain transfer agent. The low-temperature initiation system protects the integrity of functional groups, achieving self-flowing molding and high-density packing of the slurry at low dosages. At high temperatures, the phosphorus-containing components are converted into a highly active phosphate phase, which reacts with metal cations in the slag to form a dense, high-melting-point protective layer, preventing slag penetration. The silane components decompose to produce nano-silica, which can improve density. Efficient dispersion at room temperature achieves tight particle packing and reduces initial porosity. In synergy with the high-temperature slag barrier, it achieves a balance between self-flowing properties, dense molding, and high-temperature resistance to slag corrosion. Detailed Implementation

[0016] The following embodiments provide a further detailed description of this application.

[0017] Preparation example of modified water-reducing agent

[0018] Triethanolamine was purchased from Jinan Jinhao Chemical Co., Ltd., with a purity of 85%; mercaptoacetic acid was purchased from Shandong Jinyueyuan New Materials Co., Ltd., with a purity of 99%.

[0019] Preparation Example 1 (1) Add 40g of 50% aqueous solution of methacryloyloxyethyl phosphate, 100g of methoxy polyethylene glycol acrylate, 15g of acrylic acid, 20g of methacryloyloxypropyltrimethoxysilane and 2g of mercaptoacetic acid to 100g of water to prepare solution A. (2) Add 2.5g of ammonium persulfate and 1.5g of ammonium bisulfite to 50g of water, mix well, and prepare solution B; (3) Add 150g of water to the reaction vessel, heat to 50℃, add solution A at a rate of 1.8mL / min and solution B at a rate of 0.31mL / min to the reaction vessel simultaneously. After the addition is complete, keep the temperature at 50℃ and continue the reaction for 2h. Cool down to the standard ambient temperature and adjust the pH to 5.0 with triethanolamine to obtain the modified water-reducing agent.

[0020] Preparation Example 2 (1) Add 40g of 50% aqueous solution of methacryloyloxyethyl phosphate, 100g of methoxy polyethylene glycol acrylate, 15g of acrylic acid, 20g of methacryloyloxypropyltrimethoxysilane and 2g of mercaptoacetic acid to 100g of water to prepare solution A. (2) Add 2.5g of ammonium persulfate and 1.5g of ammonium bisulfite to 50g of water, mix well, and prepare solution B; (3) Add 150g of water to the reaction vessel, heat to 55℃, add solution A at a rate of 1.8mL / min and solution B at a rate of 0.31mL / min to the reaction vessel simultaneously. After the addition is complete, keep the temperature at 55℃ and continue the reaction for 2h. Cool down to the standard ambient temperature and adjust the pH to 5.5 with triethanolamine to obtain the modified water-reducing agent.

[0021] Preparation Example 3 The difference from Preparation Example 1 is that in step (1), no aqueous solution of methacryloyloxyethyl phosphate is added.

[0022] Preparation Example 4 The difference from Preparation Example 1 is that in step (1), methacryloyloxypropyltrimethoxysilane is not added.

[0023] Preparation Example 5 The difference from Preparation Example 1 is that ammonium bisulfite is not added in step (2).

[0024] Example

[0025] In the following embodiments, fused dense corundum was purchased from Zhengzhou Zhenzhong Fused New Materials Co., Ltd.; tabular corundum fine powder was purchased from Zhengzhou Haixu Abrasive Co., Ltd.; silicon carbide fine powder was purchased from Shandong Jinmeng New Materials Co., Ltd.; α-Al2O3 micro powder was purchased from Yangzhou Zhongtianli New Materials Co., Ltd., with the product number ZTL-GCAO-035; active SiO2 micro powder was purchased from Sheng Ansi Technology (Dongguan) Co., Ltd.; and magnesium aluminum spinel micro powder was purchased from Gongyi Jinliang Refractory Materials Co., Ltd.

[0026] Example 1: Self-flowing, densified, cement-free refractory castable. The raw material dosage is shown in Table 1. The modified water-reducing agent is prepared using the method described in Example 1. The particle size of the electrofused dense corundum is 10 mm, the particle size of the tabular corundum fine powder is 1 mm, and the particle size of the silicon carbide fine powder is 0.074 mm.

[0027] The self-flowing, densified, cement-free refractory castable includes the following steps: mixing aggregates, binders, and admixtures evenly, adding modified water-reducing agent and water for wet mixing, pouring into a mold, sealing and curing for 24 hours, demolding, heating to 110℃ at a rate of 1℃ / min, holding for 24 hours, heating to 1330℃ at a rate of 5℃ / min, and holding for 4 hours to obtain the self-flowing, densified, cement-free refractory castable.

[0028] Table 1. Raw material consumption of self-flowing, densified, cementless refractory castables in Examples 1-4

[0029] Example 2: Self-flowing, densified, cementless refractory castable. The difference from Example 1 is that the raw material dosage is as shown in Table 1, the modified water-reducing agent is prepared by the method in Example 2 of modified water-reducing agent preparation, the particle size of fused alumina is 1 mm, the particle size of tabular alumina fine powder is 0.074 mm, and the particle size of silicon carbide fine powder is 0.030 mm.

[0030] The self-flowing, densified, cement-free refractory castable includes the following steps: mixing aggregates, binders, and admixtures evenly, adding modified water-reducing agent and water for wet mixing, pouring into a mold, sealing and curing for 20 hours, demolding, heating to 100℃ at a rate of 0.5℃ / min, holding for 20 hours, heating to 1200℃ at a rate of 2℃ / min, and holding for 3 hours to obtain the self-flowing, densified, cement-free refractory castable.

[0031] Example 3: Self-flowing, densified, cementless refractory castable. The difference from Example 1 is that the raw material dosage is as shown in Table 1, the modified water-reducing agent is prepared by the method in Example 1 of modified water-reducing agent preparation, the particle size of fused alumina is 5 mm, the particle size of tabular alumina fine powder is 0.09 mm, and the particle size of silicon carbide fine powder is 0.074 mm.

[0032] Example 4: Self-flowing, densified, cementless refractory castable. The difference from Example 1 is that the raw material dosage is as shown in Table 1, the modified water-reducing agent is prepared by the method in Example 2 of modified water-reducing agent preparation, the particle size of fused alumina is 5 mm, the particle size of tabular alumina fine powder is 0.09 mm, and the particle size of silicon carbide fine powder is 0.074 mm.

[0033] Comparative Example

[0034] Comparative Example 1: Self-flowing, densified, cement-free refractory castable, differing from Example 1 in that the modified water-reducing agent was prepared using the method described in Modified Water-Reducing Agent Preparation Example 3.

[0035] Comparative Example 2: Self-flowing, densified, cementless refractory castable, which differs from Example 1 in that the modified water-reducing agent is prepared using the method in Modified Water-Reducing Agent Preparation Example 4.

[0036] Comparative Example 3: Self-flowing, densified, cementless refractory castable, which differs from Example 1 in that the modified water-reducing agent is prepared using the method in Modified Water-Reducing Agent Preparation Example 5.

[0037] Comparative Example 4: Self-flowing, densified, cement-free refractory castable. The difference from Example 1 is that the modified water-reducing agent is replaced by an equal amount of polycarboxylate water-reducing agent, which was purchased from Jiangxi Anrui Building Materials Co., Ltd., Shanxi Province, and the model number is 101.

[0038] Performance testing

[0039] Self-flowing, densified, cementless refractory castables were prepared according to the methods in the examples and comparative examples, and their performance was tested according to the following methods. The test results are recorded in Table 2.

[0040] 1. Self-flow value: Tested in accordance with GB / T 4513.4-2017 "Unshaped refractories - Part 4: Determination of flowability of castables"; 2. Apparent porosity and bulk density: Tested according to GB / T 2997-2015 "Test methods for bulk density, apparent porosity and true porosity of dense shaped refractory products"; 3. Room temperature compressive strength: Tested according to GB / T 5072-2023 "Test Method for Room Temperature Compressive Strength of Refractory Materials"; 4. High-temperature compressive strength: Tested according to YB / T 2208-1998 "Test Method for High-Temperature Compressive Strength of Refractory Castables"; 5. Slag resistance: The erosion depth is tested in accordance with GB / T 8931-2007 "Test Method for Slag Resistance of Refractory Materials".

[0041] Table 2. Performance test results of the refractory castables prepared in the examples and comparative examples. Example 1 210.5 15.04 3.19 55.7 91.1 6.2 Example 2 211.9 14.68 3.11 55.8 91.4 6.1 Example 3 213.4 14.27 3.14 56.1 91.3 5.9 Example 4 212.1 14.33 3.06 55.3 90.9 6.0 Comparative Example 1 210.8 16.41 2.87 50.4 88.7 7.7 Comparative Example 2 211.7 16.75 2.12 55.2 90.1 5.8 Comparative Example 3 193.4 17.11 2.13 56.3 90.3 6.4 Comparative Example 4 209.7 15.22 3.17 50.6 86.5 8.9 As shown in Table 2, the refractory castables prepared in Examples 1-4 of this application have good self-flowability, densification, and high-temperature slag corrosion resistance. Comparing Comparative Example 1 with Example 1, the densification and high-temperature slag corrosion resistance are significantly reduced, possibly due to the absence of methacryloyloxyethyl phosphate. Comparative Example 2 shows reduced densification compared to Example 1, mainly due to the absence of silanoxy groups in methacryloyloxypropyltrimethoxysilane, preventing the formation of Si-O covalent bonds with hydroxyl groups on the powder surface, and insufficient construction of a cross-linked network structure between dispersant molecules. Comparative Example 3 shows significantly reduced self-flowability and densification compared to Example 1, possibly due to the absence of ammonium bisulfite, which fails to protect the functional integrity of the functional groups. Comparing Comparative Example 1 with Example 4, the high-temperature slag corrosion resistance is slightly reduced; the polycarboxylate superplasticizer is inferior to the modified superplasticizer in terms of improved properties such as high-temperature slag corrosion resistance.

[0042] 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. Self-flowing densified cement-free refractory castable, characterized in that, The raw materials include the following parts by weight: 70-80 parts aggregate, 5-8 parts binder, 0.5-2 parts admixture, 0.5-1 part modified water-reducing agent, and 5-8 parts water; The preparation method of the modified water-reducing agent includes the following steps: (1) Add aqueous solution of methacryloyloxyethyl phosphate, methoxy polyethylene glycol acrylate, acrylic acid, methacryloyloxypropyltrimethoxysilane and mercaptoacetic acid to water to prepare solution A; (2) Add ammonium persulfate and ammonium bisulfite to water, mix well, and prepare solution B; (3) Add water to the reaction vessel and heat it to 50-55℃. Add solution A and solution B dropwise to the reaction vessel at the same time. After the addition is complete, keep the temperature at 50-55℃ and continue the reaction for 2 hours. Cool down to the standard ambient temperature and adjust the pH to 5.0-5.5 with triethanolamine to obtain the modified water-reducing agent.

2. Self-flowing densifying non-cementitious refractory castable according to claim 1, characterized in that, The aggregate is composed of fused dense corundum, tabular corundum fine powder and silicon carbide fine powder in a mass ratio of 1:0.5-1:

2.

3. Self-flowing densifying non-cementitious refractory castable according to claim 2, characterized in that The electrofused dense corundum has a particle size of 1-10 mm, the tabular corundum fine powder has a particle size of 0.074-1 mm, and the silicon carbide fine powder has a particle size of 0-0.074 mm.

4. The self-flowing densifying non-cementitious refractory castable according to claim 1, characterized in that, The binder is composed of active α-Al2O3 micro powder, active SiO2 micro powder and magnesium aluminum spinel micro powder in a mass ratio of 1:0.5-0.8:0.5-1.

5.

5. The self-flowing, densified, cement-free refractory castable according to claim 1, characterized in that, The additive consists of sodium citrate and sodium tripolyphosphate in a mass ratio of 1:1-2.

6. The method for preparing the self-flowing, densified, cementless refractory castable according to any one of claims 1-5, characterized in that, Includes the following steps: Aggregates, binders, and additives are mixed evenly, and modified water-reducing agent and water are added for wet mixing. The mixture is poured into a mold, sealed and cured for 20-24 hours, demolded, dried, and sintered to obtain a self-flowing, dense, cement-free refractory castable.

7. The method for preparing self-flowing, densified, cementless refractory castable according to claim 6, characterized in that, The drying temperature range is 100-110℃, the holding time is 20-24h, and the heating rate is 0.5-1℃ / min; the sintering temperature range is 1200-1330℃, the holding time is 3-4h, and the heating rate is 2-5℃ / min.

Images