A high-performance rheology modifier for coal gangue-based concrete, its preparation method and application

Abstract

This invention discloses a high-performance rheology modifier for coal gangue-based concrete, its preparation method, and its application, relating to the fields of mining engineering materials and solid waste resource utilization technology. The rheology modifier, by mass percentage, comprises: 55%–65% rheology modifier and 35%–45% water-reducing agent; wherein the rheology modifier is a polymer copolymerized from monomers such as acrylamide, 2-acryloylamino-2-methyl-1-propanesulfonic acid, and styrene, and the water-reducing agent is a lignin sulfonate water-reducing agent and / or a polycarboxylate water-reducing agent. In its preparation, the above monomers are first mixed with a portion of water to form a precursor solution, then polymerized to form a gel, subsequently dissolved in water to obtain a polymer solution, and finally the water-reducing agent is added and mixed uniformly to obtain the final product. This rheology modifier can significantly improve the fluidity and anti-segregation properties of high-content coal gangue concrete, and lays the foundation for the full development of its later mechanical strength.

Description

Technical Field

[0001] This invention belongs to the field of mining engineering materials and solid waste resource utilization technology, specifically relating to a high-performance rheology modifier for coal gangue-based concrete, its preparation method, and its application. Background Technology

[0002] With the rapid development of my country's coal industry, coal gangue, a solid waste generated during coal mining and washing, has an annual output exceeding 800 million tons, with a cumulative stockpile of over 7 billion tons. Utilizing coal gangue in concrete preparation can not only alleviate the shortage of natural aggregate resources but also effectively reduce environmental pollution, thus possessing significant economic and social importance.

[0003] However, the application of coal gangue in concrete faces significant technical challenges. Coal gangue commonly contains layered silicate minerals such as montmorillonite and illite. These minerals have strong water absorption and expansion characteristics and high specific surface area. During the concrete mixing process, they rapidly absorb mixing water and physically encapsulate cement particles, leading to a sharp decrease in the fluidity of fresh concrete and seriously affecting its workability and later strength development.

[0004] To address the aforementioned issues, existing technologies primarily employ increasing the dosage of water-reducing agents to improve the rheological properties of coal gangue-based concrete. Chinese invention patent CN109232827A discloses a high-performance polycarboxylate superplasticizer with good fluidization, which improves its dispersion performance through optimized molecular structure design. Chinese invention patent CN106146759A discloses a high-performance polycarboxylate superplasticizer that achieves good plasticizing effects using a specific monomer ratio. Chinese invention patent CN104017125B proposes a clay-resistant polycarboxylate superplasticizer, which improves the workability of high-mud-content aggregate concrete by introducing special functional groups. Chinese invention patent CN107445505A discloses a low-sensitivity polycarboxylate superplasticizer, which improves its adaptability through composite modification.

[0005] Although existing technologies have made some progress in optimizing the performance of water-reducing agents, there are still significant shortcomings in their application to coal gangue-based concrete: First, the molecular chains of traditional water-reducing agents are easily deactivated by strong adsorption between montmorillonite layers, making it impossible to effectively break the physical encapsulation effect of montmorillonite on cement particles at the molecular level; second, while simply increasing the dosage of water-reducing agents can improve fluidity to some extent, it often comes at the cost of sacrificing the early strength of concrete, making it difficult to simultaneously meet the comprehensive performance requirements of high fluidity, high stability, and high strength; third, existing water-reducing agent products lack specific designs for the special mineral components in coal gangue, and their adaptability and stability in complex coal gangue-cement systems need to be improved. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the present invention aims to provide a high-performance rheology modifier for coal gangue-based concrete, its preparation method and application, to solve the technical problems of poor fluidity of fresh concrete paste, easy segregation and bleeding, and difficulty in achieving the required strength after hardening when coal gangue is used as concrete aggregate at a high substitution rate due to its clay components such as montmorillonite.

[0007] To achieve the above objectives, the present invention employs the following technical solution: In a first aspect, the present invention provides a high-performance rheology modifier for coal gangue-based concrete, comprising, by mass percentage: 55%~65% rheology modifier and 35%~45% water-reducing agent; wherein the rheology modifier is a polymeric material and the water-reducing agent is a lignin sulfonate water-reducing agent and / or a polycarboxylate water-reducing agent.

[0008] A further improvement of the present invention is that the rheology modifier is copolymerized from raw materials comprising the following components by mass percentage: 1%~5% acrylamide, 0.1%~0.5% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.1%~0.8% styrene, 0.05%~0.2% initiator, and the balance being water.

[0009] A further improvement of the present invention is that the initiator is ammonium persulfate.

[0010] A further improvement of the present invention is that the water-reducing agent is a polycarboxylate water-reducing agent, and the mass ratio of the rheology modifier to the water-reducing agent is (1.2~1.8):1.

[0011] Secondly, the present invention also provides a method for preparing a high-performance rheology modifier for coal gangue-based concrete, comprising the following steps: Step 1: Weigh acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, styrene, initiator and the first portion of water according to the ratio, put them into the reaction vessel, and stir evenly at room temperature to form a precursor solution; Step 2: Heat the precursor liquid to 60°C~80°C and continuously stir under constant temperature conditions to carry out the polymerization reaction until the system forms a uniform gel. Step 3: Add a second portion of water to the homogeneous gel obtained in Step 2, and stir until completely dissolved to form a homogeneous and transparent polymer solution; Step 4: After the polymer solution cools, add the formulated amount of water-reducing agent and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0012] A further improvement of the present invention is that, in step 1, the mass of the first part of water is 40% to 70% of the total water required to prepare the rheology modifier; and in step 3, the mass of the second part of water is the total water required to prepare the rheology modifier minus the mass of the first part of water.

[0013] Thirdly, the present invention also provides a coal gangue-based concrete, comprising the above-mentioned high-performance rheology modifier for coal gangue-based concrete, as well as coal gangue aggregate, natural gravel, cementitious materials, fine aggregate and water.

[0014] A further improvement of the present invention is that the dosage of the high-performance rheology modifier for coal gangue-based concrete is 0.3% to 0.5% of the total mass of the concrete; the cementitious materials include cement and fly ash; and the fine aggregate is aeolian sand.

[0015] A further improvement of the present invention is that the particle size range of the coal gangue aggregate is 2-4 cm; the coal gangue aggregate accounts for 40%-70% of the total mass of the coal gangue aggregate and the natural stones.

[0016] Fourthly, the present invention also provides the application of the high-performance rheology modifier for coal gangue-based concrete as described above in improving the rheological properties of coal gangue-based concrete.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention provides a high-performance rheology modifier for coal gangue-based concrete. By controlling the mass percentage of rheology modifier to water-reducing agent at 55%~65% to 35%~45%, the rheology modifier dominates the system while retaining a sufficient proportion of water-reducing component to provide the necessary dispersing force. Specifically, the rheology modifier, as a polymeric material, can construct a three-dimensional network structure in the concrete paste, increasing the cohesiveness and stability of the paste, effectively encapsulating aggregate particles, and preventing segregation and bleeding. Meanwhile, the 35%~45% lignin sulfonate and / or polycarboxylate water-reducing agent provides significant electrostatic repulsion and steric hindrance effects, efficiently dispersing cement particles and releasing the encapsulated water, thereby significantly reducing the mixing water requirement and improving the initial fluidity of the paste. This combination allows the rheology modifier, when applied to coal gangue-based concrete, to both suppress the damage to the slurry structure and loss of workability caused by factors such as water absorption and irregular shape of coal gangue aggregates through the physical network effect of the rheology modifier, and overcome the additional water demand and fluidity degradation caused by the powdery or clayey components of coal gangue through the dispersing function of the water-reducing agent. This rheology modifier reliably enables high-proportion coal gangue concrete to achieve significantly improved slump, good cohesiveness, and excellent anti-segregation ability while maintaining low water consumption, laying the foundation for the full development of its later mechanical strength.

[0018] This invention also provides a method for preparing a high-performance rheology modifier for coal gangue-based concrete. Acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, styrene, and an initiator are uniformly mixed in water to form a homogeneous and stable precursor solution, providing a reliable foundation for subsequent copolymerization. Subsequently, isothermal polymerization is carried out at a suitable temperature of 60°C to 80°C, promoting the full reaction of each functional monomer to form a homogeneous gel with a three-dimensional network structure. Then, water is added and stirred to completely dissolve the gel into a homogeneous and transparent solution, allowing the polymer molecules to fully expand and expose active sites. This not only facilitates storage and transportation but also provides conditions for subsequent uniform compounding with a water-reducing agent. Finally, after the solution is cooled, the water-reducing agent is added for compounding, avoiding potential degradation of the water-reducing agent molecular chains due to high temperatures. Thorough stirring ensures uniform mixing of the rheology and water-reducing components at the molecular scale, thereby guaranteeing that the final product can stably and synergistically exert its comprehensive performance in adsorption dispersion, spatial stability, and viscosity regulation. The entire process is clear and controllable, with good reproducibility. The prepared regulators have consistent performance and can reliably achieve the design goal of improving the workability and stability of coal gangue concrete.

[0019] Furthermore, the coal gangue-based concrete of this invention, by incorporating a high-performance rheology modifier in a specific ratio, effectively solves the technical problems of viscous concrete paste, poor fluidity, and easy segregation and bleeding caused by the large-scale use of coal gangue aggregate. The functional components in the modifier can act specifically on the surface of the coal gangue, inhibiting its harmful water absorption and releasing the encapsulated cement particles and hydration spaces. This achieves a high substitution rate of 40% to 70% for natural aggregate with coal gangue while ensuring good workability and homogeneity of the concrete. This not only significantly improves the construction performance and later mechanical strength of the concrete but also provides a reliable guarantee for its large-scale application in projects such as coal mine roadway flooring. Detailed Implementation

[0020] To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0021] The theories or mechanisms described and disclosed herein, whether right or wrong, should not in any way limit the scope of the invention, that is, the contents of the invention can be implemented without being limited by any particular theory or mechanism.

[0022] In this document, all features defined by numerical ranges or percentage ranges, such as numerical values, quantities, contents, and concentrations, are for the sake of brevity and convenience only. Accordingly, descriptions of numerical ranges or percentage ranges should be considered as covering and specifically disclosing all possible sub-ranges and individual numerical values ​​(including integers and fractions) within those ranges.

[0023] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0024] For the sake of brevity, not all possible combinations of the technical features in each implementation scheme or embodiment are described herein. Therefore, as long as there is no contradiction in the combination of these technical features, the technical features in each implementation scheme or embodiment can be combined arbitrarily, and all possible combinations should be considered within the scope of this specification.

[0025] This invention provides a high-performance rheology modifier for coal gangue-based concrete, comprising, by mass percentage: 55%~65% rheology modifier and 35%~45% water-reducing agent; wherein the rheology modifier is a polymeric material and the water-reducing agent is a lignin sulfonate water-reducing agent and / or a polycarboxylate water-reducing agent.

[0026] Specifically, the rheology modifier is a polymer copolymerized from the following components by mass percentage: acrylamide 1%~5%, 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) 0.1%~0.5%, styrene 0.1%~0.8%, initiator (ammonium persulfate) 0.05%~0.2%, and the balance being water. Acrylamide provides the polymer backbone and film-forming ability, the strongly polar sulfonic acid groups of AMPS are responsible for competitive adsorption on the montmorillonite surface, and styrene imparts rigidity to the chain segments and regulates the hydrophilicity-hydrophobicity balance. The copolymerization of these three components in this ratio can specifically break the encapsulation of water and cement particles by montmorillonite.

[0027] Preferably, the water-reducing agent is a polycarboxylate water-reducing agent, and the mass ratio of the rheology modifier to the water-reducing agent is (1.2~1.8):1.

[0028] This invention also provides a method for preparing a high-performance rheology modifier for coal gangue-based concrete, comprising the following steps: Step 1: Weigh acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, styrene, initiator, and a first portion of water according to the specified ratio, and add them to a reaction vessel. Stir at room temperature until homogeneous to form a precursor solution. The mass of the first portion of water is 40% to 70% of the total water required to prepare the rheology modifier. Step 2: Heat the precursor liquid to 60°C~80°C and continuously stir under constant temperature conditions to carry out the polymerization reaction until the system forms a uniform gel. Step 3: Add a second part of water to the homogeneous gel obtained in Step 2, and stir until completely dissolved to form a homogeneous and transparent polymer solution; wherein, the mass of the second part of water is the total amount of water required to prepare the rheology modifier minus the mass of the first part of water; Step 4: After the polymer solution cools, add the formulated amount of water-reducing agent and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0029] This invention also provides a coal gangue-based concrete, comprising the aforementioned high-performance rheology modifier for coal gangue-based concrete, as well as coal gangue aggregate, natural gravel, cementitious materials, fine aggregate, and water; wherein the dosage of the high-performance rheology modifier for coal gangue-based concrete is 0.3% to 0.5% of the total mass of the concrete; the cementitious materials include cement and fly ash; and the fine aggregate is aeolian sand. Using aeolian sand as fine aggregate not only achieves solid waste resource utilization but also optimizes the gradation of the concrete and improves its density.

[0030] The particle size range of the coal gangue aggregate is 2~4cm; the coal gangue aggregate accounts for 40%~70% of the total mass of the coal gangue aggregate and the natural stones.

[0031] The preparation method of this coal gangue-based concrete includes the following steps: S1, crush and screen the coal gangue aggregate to make its particle size range of 2~4cm; S2, weigh the following components according to the following mass percentages (based on the total mass of concrete): 18%~34% coal gangue aggregate, 14%~30% natural gravel, 14%~18% cementitious material, 25%~30% fine aggregate, and 7%~8% water, mix them evenly to obtain the initial slurry; preferably, the sum of coal gangue aggregate and natural gravel accounts for 45%~50% of the total mass of concrete, and the coal gangue aggregate accounts for 40%~70% of the sum of the two; S3. Add 0.3% to 0.5% of the total mass of the concrete to the initial slurry obtained in S2. Mechanically stir for 5 to 15 minutes at a temperature of 10°C to 35°C to form a uniform concrete slurry, which is the coal gangue-based concrete.

[0032] As a preferred embodiment, when the rheology modifier dosage is 0.4% and the coal gangue aggregate accounts for 60% of the total mass of coarse aggregate, the mass percentage of each component is as follows: coal gangue aggregate 28.8%, natural stones 19.2%, cementitious materials 16%, fine aggregate 28%, and water 7.6%.

[0033] The present invention also provides the application of the high-performance rheology modifier for coal gangue-based concrete as described above in improving the rheological properties of coal gangue-based concrete.

[0034] The high-performance rheology modifier for coal gangue-based concrete proposed in this invention mainly achieves modification and flowability improvement of coal gangue through the following three common mechanisms: (1) Competitive adsorption and encapsulation release mechanism at the molecular level. Montmorillonite in coal gangue carries a negative charge and easily adsorbs water molecules to cause expansion. The 2-acrylamido-2-methyl-1-propanesulfonic acid monomer in this invention contains a strongly polar sulfonic acid group, which can generate strong charge attraction and preferentially adsorb onto the active sites of montmorillonite before water molecules. At the same time, the polymer chains formed by acrylamide form a flexible protective film on the surface of montmorillonite through hydrogen bonding. This mechanism can effectively inhibit the water absorption and expansion of montmorillonite and forcibly open the physical encapsulation layer of montmorillonite on cement particles and early hydration products such as ettringite. (2) Recovery and promotion mechanism of hydration reaction. In conventional coal gangue slurry, the encapsulation of cement particles by montmorillonite leads to a reduction in the effective hydration area, causing the hydration reaction of tricalcium silicate and dicalcium silicate to stagnate. The cement particles released by the rheology modifier in this invention can re-contact with free water. The polar groups in the rheology modifier can reduce the surface tension of the liquid phase, promote the penetration of water molecules into the cement particles, and restore and accelerate the formation of CSH gel. (3) Synergistic mechanism of steric hindrance and rheological regulation. The introduction of styrene gives the polymer chain a certain rigidity and hydrophobicity, which produces a steric hindrance effect with the long branched structure of polycarboxylic acid water-reducing agent. This effect constructs a stable three-dimensional repulsion network inside the slurry, preventing solid particles from flocculating. By adjusting the yield stress and plastic viscosity inside the slurry, the coal gangue-based concrete has excellent anti-bleeding and anti-segregation ability while having high fluidity. In terms of fluidity, even with a coal gangue replacement rate as high as 70%, the slump of the concrete slurry remains above 200 mm; regarding water bleeding, after standing for two hours, there is no water bleeding, and the coarse aggregate in the concrete does not show any settling phenomenon; in terms of mechanical properties, the compressive strength is significantly improved, fully meeting the requirements for coal mine roadway flooring; ensuring efficient construction and structural durability of coal mine roadway flooring projects, with significant environmental and economic benefits.

[0035] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0036] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" represents weight percentage, "parts" represents parts by weight, and "ratio" represents weight proportion.

[0037] In the following embodiments, unless otherwise stated, all performance tests were conducted under the following conditions and standards: Slump and spread: Tested in accordance with the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T 50080); Bleeding rate: The bleeding rate test method shall be carried out in accordance with the "Standard for Test Methods of Performance of Ordinary Concrete Mixtures" (GB / T 50080); Compressive strength: Tested according to the "Standard for Test Methods of Physical and Mechanical Properties of Concrete" (GB / T 50081). The specimen size is 150 mm × 150 mm × 150 mm. The curing conditions are temperature 20 ± 2°C, relative humidity ≥ 95%, and loading rate 0.5 MPa / s.

[0038] Example 1 This embodiment provides a coal gangue-based concrete slurry with a replacement rate of 40%, which, by mass percentage, includes the following raw materials: 0.4% high-performance rheology modifier for coal gangue-based concrete, 48% coarse aggregate for concrete, 16% cementitious material, 28% fine aggregate, and 7.6% water.

[0039] Of the total mass of concrete, coarse aggregate accounts for 48%, consisting of coal gangue aggregate and natural gravel. The coal gangue aggregate is composed of crushed and screened particles with a particle size range of 3±1 cm; the natural gravel has a particle size of 1.5±0.5 cm. Coal gangue aggregate accounts for 40% of the total mass of coarse aggregate in concrete, i.e., 19.2% coal gangue aggregate and 28.8% natural gravel; the cementitious material consists of cement and fly ash; and the fine aggregate is aeolian sand.

[0040] 1. Preparation of rheology modifiers: (1) Preparation of rheology modifiers: Weigh out 3% acrylamide, 0.3% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.5% styrene, 0.1% ammonium persulfate, and the first part of water (accounting for 60% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 40% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0041] (2) Compound formulation of rheology modifiers: Take 60 parts of the above rheology modifier, add 40 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0042] 2. Preparation of Coal Gangue-Based Concrete (1) Weigh out 48% coarse aggregate, 28% aeolian sand, 16% cementitious material and 7.6% water according to the proportion, and mix them evenly with a mixer to obtain the foundation slurry; (2) Add 0.4% of the rheology modifier prepared in this embodiment to the above-mentioned basic slurry and mechanically stir at 10°C for 15 minutes to obtain a coal gangue-based concrete slurry with a replacement rate of 40%.

[0043] The bleeding rate of the coal gangue-based concrete slurry with a replacement rate of 40% obtained in this embodiment was tested, and the test results are shown in Table 1.

[0044] Table 1. Bleeding rate of coal gangue-based concrete slurry with a 40% replacement rate in this embodiment.

[0045] The compressive strength of the coal gangue-based concrete with a replacement rate of 40% obtained in this embodiment was tested, and the test results are shown in Table 2.

[0046] Table 2. Compressive strength test results of coal gangue-based concrete samples with a 40% replacement rate in this embodiment.

[0047] Example 2 This embodiment provides a coal gangue-based concrete slurry with a replacement rate of 50%, which, by mass percentage, includes the following raw materials: 0.4% high-performance rheology modifier for coal gangue-based concrete, 48% coarse aggregate for concrete, 16% cementitious material, 28% fine aggregate, and 7.6% water.

[0048] Of the total mass of concrete, coarse aggregate accounts for 48%, consisting of coal gangue aggregate and natural gravel. The coal gangue aggregate is composed of crushed and screened particles with a particle size range of 3±1 cm; the natural gravel has a particle size of 1.5±0.5 cm. Coal gangue aggregate accounts for 50% of the total mass of coarse aggregate, i.e., 24% coal gangue aggregate and 24% natural gravel. The cementitious material consists of cement and fly ash; the fine aggregate is aeolian sand.

[0049] 1. Preparation of rheology modifiers: (1) Preparation of rheology modifiers: Weigh out 3% acrylamide, 0.3% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.5% styrene, 0.1% ammonium persulfate, and the first part of water (accounting for 60% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 40% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0050] (2) Compound formulation of rheology modifiers: Take 60 parts of the above rheology modifier, add 40 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0051] 2. Preparation of Coal Gangue-Based Concrete (1) Weigh out 48% coarse aggregate, 28% aeolian sand, 16% cementitious material and 7.6% water according to the proportion, and mix them evenly with a mixer to obtain the foundation slurry; (2) Add 0.4% of the rheology modifier prepared in this embodiment to the above-mentioned basic slurry and mechanically stir at 20°C for 10 minutes to obtain a coal gangue-based concrete slurry with a replacement rate of 50%.

[0052] The bleeding rate of the coal gangue-based concrete slurry with a replacement rate of 50% obtained in this embodiment was tested, and the test results are shown in Table 3.

[0053] Table 3. Bleeding rate of coal gangue-based concrete slurry with a 50% replacement rate in this embodiment.

[0054] The compressive strength of the coal gangue-based concrete with a replacement rate of 50% obtained in this embodiment was tested, and the test results are shown in Table 4.

[0055] Table 4. Compressive strength test results of coal gangue-based concrete samples with a 50% replacement rate in this embodiment.

[0056] Example 3 This embodiment provides a coal gangue-based concrete slurry with a replacement rate of 60%, which, by mass percentage, includes the following raw materials: 0.4% high-performance rheology modifier for coal gangue-based concrete, 48% coarse aggregate for concrete, 16% cementitious material, 28% fine aggregate, and 7.6% water.

[0057] Of the total mass of concrete, coarse aggregate accounts for 48%, consisting of coal gangue aggregate and natural gravel. The coal gangue aggregate is composed of crushed and screened particles with a particle size range of 3±1 cm; the natural gravel has a particle size of 1.5±0.5 cm. Coal gangue aggregate accounts for 60% of the total mass of coarse aggregate, i.e., 28.8% coal gangue aggregate and 19.2% natural gravel. The cementitious material consists of cement and fly ash; the fine aggregate is aeolian sand.

[0058] 1. Preparation of rheology modifiers: (1) Preparation of rheology modifiers: Weigh out 3% acrylamide, 0.3% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.5% styrene, 0.1% ammonium persulfate, and the first part of water (accounting for 60% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 40% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0059] (2) Compound formulation of rheology modifiers: Take 60 parts of the above rheology modifier, add 40 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0060] 2. Preparation of Coal Gangue-Based Concrete (1) Weigh out 48% coarse aggregate, 28% aeolian sand, 16% cementitious material and 7.6% water according to the proportion, and mix them evenly with a mixer to obtain the foundation slurry; (2) Add 0.4% of the rheology modifier prepared in this embodiment to the above-mentioned basic slurry and mechanically stir at 10°C for 15 minutes to obtain a coal gangue-based concrete slurry with a replacement rate of 60%.

[0061] The bleeding rate of the coal gangue-based concrete slurry with a replacement rate of 60% obtained in this embodiment was tested, and the test results are shown in Table 5.

[0062] Table 5. Bleeding rate of coal gangue-based concrete slurry with a 60% replacement rate in this embodiment.

[0063] The compressive strength of the coal gangue-based concrete with a replacement rate of 60% obtained in this embodiment was tested, and the test results are shown in Table 6.

[0064] Table 6. Compressive strength test results of coal gangue-based concrete samples with a 60% replacement rate in this embodiment.

[0065] Example 4 This embodiment provides a coal gangue-based concrete slurry with a replacement rate of 70%, which includes the following raw materials by mass percentage: 0.4% high-performance rheology modifier for coal gangue-based concrete, 48% coarse aggregate for concrete, 16% cementitious material, 28% fine aggregate and 7.6% water.

[0066] Of the total mass of concrete, coarse aggregate accounts for 48%, consisting of coal gangue aggregate and natural gravel. The coal gangue aggregate is composed of crushed and screened particles with a particle size range of 3±1 cm; the natural gravel has a particle size of 1.5±0.5 cm. Coal gangue aggregate accounts for 70% of the total mass of coarse aggregate, i.e., 33.6% coal gangue aggregate and 14.4% natural gravel. The cementitious material consists of cement and fly ash; the fine aggregate is aeolian sand.

[0067] 1. Preparation of rheology modifiers: (1) Preparation of rheology modifiers: Weigh out 3% acrylamide, 0.3% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.5% styrene, 0.1% ammonium persulfate, and the first part of water (accounting for 60% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 40% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0068] (2) Compound formulation of rheology modifiers: Take 60 parts of the above rheology modifier, add 40 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0069] 2. Preparation of Coal Gangue-Based Concrete (1) Weigh out 48% coarse aggregate, 28% aeolian sand, 16% cementitious material and 7.6% water according to the proportion, and mix them evenly with a mixer to obtain the foundation slurry; (2) Add 0.4% of the rheology modifier prepared in this embodiment to the above-mentioned basic slurry and mechanically stir at 30°C for 5 minutes to obtain a coal gangue-based concrete slurry with a replacement rate of 70%.

[0070] The bleeding rate of the coal gangue-based concrete slurry with a replacement rate of 70% obtained in this embodiment was tested, and the test results are shown in Table 7.

[0071] Table 7. Bleeding rate of coal gangue-based concrete slurry with a 70% replacement rate in this embodiment.

[0072] The compressive strength of the coal gangue-based concrete with a replacement rate of 70% obtained in this embodiment was tested, and the test results are shown in Table 8.

[0073] Table 8. Compressive strength test of coal gangue-based concrete samples with a 70% replacement rate in this embodiment.

[0074] Example 5 This embodiment provides a practical application of a coal gangue-based concrete slurry with a substitution rate of 60% in underground roadway engineering. By mass percentage, it includes the following raw materials: 0.4% high-performance rheology modifier for coal gangue-based concrete, 28.8% coal gangue aggregate, 19.2% natural stone, 16% cementitious material, 28% fine aggregate, and 7.6% water.

[0075] Of the total mass of concrete, coarse aggregate accounts for 48%, consisting of coal gangue aggregate and natural gravel. The coal gangue aggregate is composed of crushed and screened particles with a particle size range of 3±1 cm; the natural gravel has a particle size of 1.5±0.5 cm. Coal gangue aggregate accounts for 60% of the total mass of coarse aggregate in concrete. The cementitious material consists of cement and fly ash; the fine aggregate is aeolian sand.

[0076] 1. Preparation of rheology modifiers: (1) Preparation of rheology modifiers: Weigh out 3% acrylamide, 0.3% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.5% styrene, 0.1% ammonium persulfate, and the first part of water (accounting for 60% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 40% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0077] (2) Compound formulation of rheology modifiers: Take 60 parts of the above rheology modifier, add 40 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0078] 2. Preparation of Coal Gangue-Based Concrete (1) Weigh out 28.8% coal gangue aggregate, 19.2% natural gravel, 16% cementitious material, 28% fine aggregate, and 7.6% water according to the proportion to obtain the basic slurry; (2) Add 0.4% of the rheology modifier prepared in this embodiment to the above-mentioned basic slurry and mechanically stir at 10°C for 15 minutes to obtain a coal gangue-based concrete slurry with a high substitution rate. (3) Use concrete mixer trucks to transport concrete to the mine roadway for paving construction. After forming, test the strength at the specified age by core sampling.

[0079] It should be noted that the concrete preparation and curing in this embodiment were carried out under the actual construction conditions of the mine roadway. The molding and curing environment differed from the standard laboratory conditions (temperature 20 ± 2°C, humidity ≥95%). Therefore, the measured compressive strength was slightly different from the test results under laboratory conditions (Example 3), but both met the strength requirements of coal mine roadway floor engineering.

[0080] The compressive strength of the coal gangue-based concrete core with a replacement rate of 60% obtained in this embodiment was tested, and the test results are shown in Table 9.

[0081] Table 9. Compressive strength test of core samples from coal gangue-based concrete with a 60% replacement rate in this embodiment.

[0082] Example 6 This embodiment provides a coal gangue-based concrete with a replacement rate of 60%, and its concrete mix proportion is the same as that of Embodiment 3, except that the composition of the rheology modifier used is different.

[0083] (1) Preparation of rheology modifiers: Weigh out 4.5% acrylamide, 0.4% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.7% styrene, 0.15% ammonium persulfate, and the first part of water (accounting for 45% of the total water in the rheology modifier formulation) by mass percentage, and add them to the reactor. Stir at room temperature to form a precursor solution. Heat the reactor to 60°C and stir at a constant temperature to carry out the polymerization reaction until a uniform gel is formed. Add the second part of water (accounting for 55% of the total water in the rheology modifier formulation) to the gel and stir until completely dissolved to obtain a uniform and transparent polymer solution, which is the rheology modifier.

[0084] (2) Compound formulation of rheology modifiers: Take 65 parts of the above rheology modifier, add 35 parts of polycarboxylate superplasticizer, and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

[0085] The method for preparing the concrete is the same as in Example 3.

[0086] The bleeding rate of the coal gangue-based concrete slurry with a replacement rate of 60% obtained in this embodiment was tested, and the test results are shown in Table 10.

[0087] Table 10. Bleeding rate of coal gangue-based concrete slurry with a 60% replacement rate in this embodiment.

[0088] The compressive strength of the coal gangue-based concrete with a replacement rate of 60% obtained in this embodiment was tested, and the test results are shown in Table 11.

[0089] Table 11 Compressive strength test results of coal gangue-based concrete samples with a 60% replacement rate in this embodiment.

[0090] The results show that even after adjusting the ratio of rheology modifier, the product still maintains excellent flowability, anti-bleeding properties, and mechanical properties, indicating that the product performance is stable and reliable within this ratio range.

[0091] Comparative Example 1 The slurry preparation is the same as in Example 3, except that the high-performance rheology modifier is replaced with an equal mass of water.

[0092] The workability of the coal gangue-based concrete slurry with a replacement rate of 60% obtained in this comparative example was tested. The test results are shown in Table 12. The results show that the concrete is in a plastic state with a slump of only 4.8 cm, the spread cannot be measured, and it has almost no fluidity, which cannot meet the requirements for pumping construction.

[0093] Table 12. Bleeding rate of coal gangue-based concrete slurry with a replacement rate of 60% obtained in this comparative example.

[0094] Comparative Example 2 The slurry preparation was the same as in Example 3, except that the high-performance rheology modifier was replaced with a polycarboxylate superplasticizer. The test results are shown in Tables 13 and 14.

[0095] Table 13. Bleeding rate of coal gangue-based concrete slurry with a replacement rate of 60% obtained in this comparative example.

[0096] Table 14 Compressive strength test results of coal gangue-based concrete samples with a substitution rate of 60% obtained in this comparative example.

[0097] The results showed that although polycarboxylate superplasticizers could provide a certain degree of fluidity, the compressive strength of concrete was significantly reduced, and normal strength growth could not be guaranteed.

[0098] Comparative Example 3 Before preparing the slurry, a portion of the coal gangue was wetted with water. The rest of the slurry preparation process was the same as in Example 3, except that the high-performance rheology modifier was replaced with an equal mass of water. The test results are shown in Table 15.

[0099] Table 15. Flowability of coal gangue-based concrete with a 60% substitution rate obtained in this comparative example.

[0100] The workability of the coal gangue-based concrete slurry with a replacement rate of 60% obtained in this comparative example was tested. The results showed that the concrete was in a plastic state with a slump of only 5.2 cm, the spread could not be measured, and it had virtually no fluidity, which could not meet the requirements for pumping construction.

[0101] In summary, the high-performance rheology modifier provided by this invention can effectively suppress the adverse effects of montmorillonite and other clay components in coal gangue on the workability of concrete, and significantly improve the fluidity and anti-segregation properties of high-volume coal gangue concrete. Experimental results show that within a coal gangue replacement rate of 40%–70%, concrete incorporating this modifier exhibits good slump and spread, shows no bleeding after 2 hours of standing, and achieves a 28-day compressive strength of 28.9–33.7 MPa, meeting engineering application requirements. This modifier provides reliable technical support for achieving a high proportion of resource utilization of coal gangue in concrete, and has good economic and environmental benefits.

[0102] The above content is only for illustrating the technical concept of the present invention and should not be construed as limiting the scope of protection of the present invention. Any modifications made to the technical solution based on the technical concept proposed in this invention shall fall within the scope of protection of the claims of this invention.

Claims

1. A high-performance rheology modifier for coal gangue-based concrete, characterized in that, The components, by mass percentage, include: 55%~65% rheology modifier and 35%~45% water-reducing agent; wherein the rheology modifier is a polymeric material and the water-reducing agent is a lignin sulfonate water-reducing agent and / or a polycarboxylate water-reducing agent; The rheology modifier is copolymerized from raw materials comprising the following components by mass percentage: 1%~5% acrylamide, 0.1%~0.5% 2-acrylamido-2-methyl-1-propanesulfonic acid, 0.1%~0.8% styrene, 0.05%~0.2% initiator, and the balance being water; The initiator is ammonium persulfate; The water-reducing agent is a polycarboxylate water-reducing agent, and the mass ratio of the rheology modifier to the water-reducing agent is (1.2~1.8):

1.

2. A method for preparing the high-performance rheology modifier for coal gangue-based concrete as described in claim 1, characterized in that, Includes the following steps: Step 1: Weigh acrylamide, 2-acrylamido-2-methyl-1-propanesulfonic acid, styrene, initiator, and a first portion of water according to the specified ratio, and add them to a reaction vessel. Stir at room temperature until homogeneous to form a precursor solution. The mass of the first portion of water is 40% to 70% of the total water required to prepare the rheology modifier. Step 2: Heat the precursor liquid to 60°C~80°C and continuously stir under constant temperature conditions to carry out the polymerization reaction until the system forms a uniform gel. Step 3: Add a second part of water to the homogeneous gel obtained in Step 2, and stir until completely dissolved to form a homogeneous and transparent polymer solution; the mass of the second part of water is the total amount of water required to prepare the rheology modifier minus the mass of the first part of water; Step 4: After the polymer solution cools, add the formulated amount of water-reducing agent and stir thoroughly to obtain the high-performance rheology modifier for coal gangue-based concrete.

3. A coal gangue-based concrete, characterized in that, It comprises the high-performance rheology modifier for coal gangue-based concrete as described in claim 1, as well as coal gangue aggregate, natural gravel, cementitious materials, fine aggregate and water.

4. The coal gangue-based concrete according to claim 3, characterized in that, The dosage of the high-performance rheology modifier for coal gangue-based concrete is 0.3% to 0.5% of the total mass of the concrete; the cementitious materials include cement and fly ash; and the fine aggregate is aeolian sand.

5. The coal gangue-based concrete according to claim 3, characterized in that, The particle size range of the coal gangue aggregate is 2~4cm; the coal gangue aggregate accounts for 40%~70% of the total mass of the coal gangue aggregate and the natural stones.

6. The application of the high-performance rheology modifier for coal gangue-based concrete as described in claim 1 in improving the rheological properties of coal gangue-based concrete.

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