A geopolymer concrete and a method of making the same

Abstract

The application discloses a geopolymer concrete and a preparation method thereof, and relates to the technical field of concrete, which is prepared from the following raw materials in parts by weight: 45-65 parts of a composite active cementitious base material, 28-38 parts of continuous gradation coarse aggregate, 12-22 parts of fine aggregate, 9-15 parts of a composite alkali activator solution, 3-8 parts of in-situ self-toughening modified minerals, 0.6-2.5 parts of a functional additive, 3-6 parts of other functional components, and 5-14 parts of water; the functional additive is prepared by compounding a polycarboxylic acid high-performance water reducing agent, sodium saccharin and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid at a mass ratio of 2: (0.8-1.2) :1. The geopolymer concrete has excellent mechanical properties, outstanding durability, simple preparation process and environmental protection and energy saving.

Description

Technical Field

[0001] This invention relates to the field of concrete technology, and in particular to a geopolymer concrete and its preparation method. Background Technology

[0002] Geopolymer concrete, as a new type of low-carbon building material, uses industrial solid waste such as fly ash, slag, and metakaolin as its main raw materials. It forms a three-dimensional network gel structure through an alkali-activated reaction, eliminating the need for high-temperature calcination. Its energy consumption is significantly lower than that of traditional cement, and its carbon emissions can be significantly reduced. It has become an ideal material to replace traditional silicate cement concrete and has broad application prospects in infrastructure construction such as buildings, transportation, and water conservancy.

[0003] Existing geopolymer concrete exhibits a dense but inflexible internal gel network structure, resulting in inherently high brittleness and significantly lower tensile strength and fracture toughness compared to ordinary concrete. In dry or fluctuating temperature and humidity environments, geopolymers are highly susceptible to microcrack formation and rapid propagation, severely impacting the long-term durability of the structure. Insufficient optimization of raw material proportions makes it difficult to achieve a balance between workability and mechanical properties in geopolymer concrete. Most research focuses on the utilization of single industrial solid wastes, with insufficient in-depth study of the synergistic effects of multiple solid wastes. Furthermore, the alkali-activated reaction rate is significantly affected by ambient temperature and activator modulus, leading to unstable early strength development and limiting its large-scale application in prefabricated buildings and emergency repair projects.

[0004] To address these issues, existing technologies often employ toughening methods such as incorporating steel fibers, polypropylene fibers, or rubber particles. However, traditional fibers are prone to agglomeration in strongly alkaline polymer slurries, resulting in weak interfacial adhesion and difficulty in effectively transferring stress. While some nano-reinforcing materials can refine pores, they are costly and have complex dispersion processes, hindering industrial-scale production. Furthermore, existing activator formulations largely rely on trial and error, lacking systematic and synergistic optimization of the silicon-to-aluminum ratio, alkali dosage, and fiber surface activity.

[0005] For example, patent application CN113998929A discloses a high-performance geopolymer concrete and its preparation method. The geopolymer concrete comprises the following raw materials in parts by weight: 1550-1600 parts mineral powder, 155-165 parts silica fume, 250-270 parts fly ash, 500-1200 parts fine aggregate, 200-800 parts ceramic ball aggregate, 867-892 parts activator, 78-234 parts fiber, 20-24 parts water-reducing agent, and 0-109 parts water. This invention incorporates ceramic balls and steel fibers into the geopolymer concrete. The fibers effectively inhibit the formation of microcracks within the concrete, significantly improving its tensile, flexural, and impact resistance. The ceramic ball aggregate suppresses the autogenous shrinkage of the geopolymer concrete, promoting good volume stability, durability, high hardness, and low density. Combined with other concrete raw materials, it effectively improves the defects of existing geopolymer concrete, such as autogenous shrinkage and high brittleness. However, it still relies on the compounding of conventional industrial solid waste and ordinary fibers, and does not fundamentally regulate the activity of silicon-aluminum minerals and the cross-linking structure of gel. As a result, it still suffers from problems such as easy fiber agglomeration, insufficient toughening synergy, and large fluctuations in early strength due to temperature and humidity. Summary of the Invention

[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a geopolymer concrete and its preparation method. This concrete has excellent mechanical properties, outstanding durability, a simple preparation process, and is environmentally friendly and energy-saving.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a geopolymer concrete, prepared by weight from the following raw materials: 45-65 parts of composite active cementitious substrate, 28-38 parts of continuously graded coarse aggregate, 12-22 parts of fine aggregate, 9-15 parts of composite alkali activator solution, 3-8 parts of in-situ self-toughening modified minerals, 0.6-2.5 parts of functional admixture, 3-6 parts of other functional components, and 5-14 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:(0.8-1.2):1.

[0008] Preferably, the composite active cementitious substrate is a mixture of natural soil powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of (6-7):(4-3):(1-2).

[0009] Preferably, the natural soil powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained by impurity removal, coarse crushing, ball milling and sieving, and constant-temperature drying; the residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 65%~75%, alumina content 12%~18%, and total alkali metal content not exceeding 2.5%; the mineral processing tailings powder is silicate-type tailings discharged from feldspar quartz sand mineral processing, obtained by impurity removal, ball milling and drying, with a residue on a 45μm square-hole sieve ≤8%, loss on ignition ≤3.0%, silica content not less than 72%, alumina content not less than 14%, and moisture content controlled below 0.5%; the palm oil fuel ash is primary dust collected from palm empty fruit bunches, palm shells and palm fibers burned in palm oil biomass boilers, without acid washing and modification treatment, with a residue on a 45μm square-hole sieve ≤5% and loss on ignition ≤4.5%.

[0010] Preferably, the continuously graded coarse aggregate is 5-25mm continuously graded crushed stone with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand or river sand with a fineness modulus of 2.4-2.9 and a mud content ≤3.0%, conforming to GB / T 14684 standard.

[0011] Preferably, the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.1-3.3, a solid content of 34-36%, and an admixture amount of 70-80% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 6-12% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 0.4-1.0% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0012] Preferably, the in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature.

[0013] Preferably, the preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite ore respectively, and mixing them at a mass ratio of (2-3):1 to obtain a flaky composite mineral powder with an average particle size of 20-60 μm; spraying the powder with a 0.5-1.2 mol / L sodium bicarbonate solution at room temperature while stirring for 5-8 minutes, and continuing to stir for 10-15 minutes after spraying; air-drying naturally, and then drying at 60-80℃ for 2-3 hours; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0014] Preferably, the polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100.

[0015] Preferably, the other functional components are compounded from wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium cinnamate in a mass ratio of (0.5-1.5):(1-3):(1.2-1.5).

[0016] Preferably, the wollastonite mineral fibers have an average diameter of 5-8 μm and an aspect ratio of (20-30):1; the hydrated calcium silicate is graded NP-CSH-10; and the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 1-3 nm and a sheet diameter of 50-200 nm.

[0017] Another objective of this invention is to provide a method for preparing the geopolymer concrete, comprising the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; loading the mixture into a standard test mold and vibrating it on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 20-24 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete.

[0018] Preferably, the segmented gradient temperature and humidity curing is divided into three stages: the first stage is the early moisturizing and quiet curing stage, where the temperature is controlled at 25±3℃ and the relative humidity is ≥90%, and the curing lasts for 3-4 days; the second stage is the mid-term temperature-increasing curing stage, where the temperature is increased to 45±5℃ at a rate of 3-5℃ / h, and the relative humidity is maintained at 85%~90%, and the curing lasts for 4-5 days; the third stage is the late standard curing stage, where the temperature is decreased to 20±2℃ at a rate of 1-3℃ / h, and the relative humidity is maintained at ≥80%, and the curing continues until the specified age of 28 days.

[0019] Due to the application of the above technical solution, the present invention has the following beneficial effects: (1) The geopolymer concrete and its preparation method disclosed in this invention use natural soil powder, mineral tailings powder and other industrial solid wastes and palm oil fuel ash as composite active cementitious substrate, combined with in-situ self-toughening modified minerals and functional admixtures. This not only greatly reduces the use of high-energy-consuming raw materials such as cement and realizes the resource utilization of solid waste, but also simplifies the preparation process and significantly improves the compressive and flexural strength of concrete compared with conventional geopolymers, solving the pain points of traditional geopolymers being prone to cracking and lacking toughness.

[0020] (2) The geopolymer concrete and its preparation method disclosed in this invention not only play a retarding role, effectively delaying the setting rate of the geopolymer and avoiding defects such as internal pores and cracks caused by excessively rapid setting, but also improve the interfacial bonding performance of the concrete, making the bond between the cementitious substrate and the aggregate more compact; 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid, with the lone pair electrons provided by the nitrogen atom of the cyclohexylamino secondary amine in its molecular structure, can coordinate and complex with alkali metal ions and aluminum ions in the system, and then form a multidentate chelate effect with the ortho-hydroxyl group and sulfonate group, firmly locking free alkali ions and inhibiting the surface efflorescence and alkali return caused by the migration and precipitation of alkali ions, while itself It possesses pH buffering, interfacial coupling, and dispersion stabilization functions, which can smoothly regulate the reaction rate of geopolymers, avoid early bursting and temperature rise and cracking of the slurry, optimize the interfacial bonding state of powder and fiber, and improve the density and toughness of the matrix. When combined with sodium saccharin, it forms a highly efficient functional synergistic system. Sodium saccharin focuses on surface-active dispersion and wetting, and moderately retarding to broaden the construction window, while this propanesulfonic acid derivative mainly focuses on chelating and solidifying alkali, alkalinity buffering, and interfacial toughening. The two complement each other and enhance each other's effects, which not only further improves the workability of the slurry and reduces bleeding and segregation, but also precisely balances the reaction process, ensuring stable strength growth in the early and late stages of the material, and significantly improving the anti-efflorescence, anti-drying shrinkage, and long-term durability stability of geopolymer concrete.

[0021] (3) The geopolymer concrete and its preparation method disclosed in this invention, wherein the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of (0.5-1.5):(1-3):(1.2-1.5); and form a synergistic effect with other raw materials. Among them, wollastonite mineral fibers, with their suitable aspect ratio, can be uniformly dispersed in the concrete, playing a role in physical reinforcement and crack resistance, and effectively inhibiting the generation and expansion of microcracks; hydrated calcium silicate can complement the geopolymer hydration products, optimize the microstructure of the cementitious system, and improve the density and strength stability of the concrete; layered nano-magnesium lithium silicate can fill the pores inside the concrete, improve the performance of the interface transition zone, and at the same time enhance the impermeability and chemical erosion resistance of the concrete. The combination of these three ingredients not only further enhances the mechanical properties and durability of concrete, but also improves the workability of the mixture, solving the problems of easy bleeding and segregation in the high-activity cementitious system mixture. In synergy with sodium saccharin, 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid and in-situ self-toughening modified minerals, the concrete achieves a breakthrough improvement in comprehensive performance compared with existing technologies, and has significant technical advantages and application value. Detailed Implementation

[0022] The following description is intended to disclose the invention and enable those skilled in the art to implement it. The preferred embodiments described below are merely examples, and other obvious variations will occur to those skilled in the art.

[0023] Example 1

[0024] A geopolymer concrete, by weight, is prepared from the following raw materials: 45 parts of composite active cementitious substrate, 28 parts of continuously graded coarse aggregate, 12 parts of fine aggregate, 9 parts of composite alkali activator solution, 3 parts of in-situ self-toughening modified mineral, 0.6 parts of functional admixture, 3 parts of other functional components, and 5 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:0.8:1.

[0025] The composite active cementitious substrate is composed of natural clay powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of 6:4:1. The natural clay powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling, sieving, and constant-temperature drying. The residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 65%, alumina content 12%, and total alkali metal content not exceeding 2.5%. The mineral processing tailings powder is... The silicate-type tailings discharged from the beneficiation of quartz sand are obtained by removing impurities, ball milling, and drying. The tailings have a sieve residue of ≤8% on a 45μm square hole sieve, a loss on ignition of ≤3.0%, a silica content of not less than 72%, an alumina content of not less than 14%, and a moisture content controlled below 0.5%. The palm oil fuel ash is the original dust collected from palm empty fruit bunches, palm shells, and palm fibers in palm oil biomass boilers. It is not subjected to acid washing or modification treatment. The tailings have a sieve residue of ≤5% on a 45μm square hole sieve and a loss on ignition of ≤4.5%.

[0026] The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone, with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand, with a fineness modulus of 2.4 and a mud content ≤3.0%, conforming to GB / T 14684 standard; the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.1, a solid content of 34%, and an admixture amount of 70% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 6% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 0.4% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0027] The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature. The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, mixing them at a mass ratio of 2:1 to obtain platy composite mineral powder with an average particle size of 20 μm; spraying the powder with 0.5 mol / L sodium bicarbonate solution at room temperature while stirring for 5 min, and continuing to stir for 10 min after spraying; air-drying naturally, then drying at 60℃ for 2 h; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0028] The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of 0.5:1:1.2; the average diameter of the wollastonite mineral fibers is 5 μm, and the aspect ratio is 20:1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 1 nm and a sheet diameter of 50 nm.

[0029] A method for preparing the aforementioned geopolymer concrete includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; compacting the mixture in a standard mold on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 20 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete. The segmented gradient temperature and humidity curing is divided into three stages: the first stage is an early moist curing stage, with the temperature controlled at 22℃ and the relative humidity ≥90%, and curing for 3 days; the second stage is a mid-term temperature-increasing curing stage, with the temperature increased to 40℃ at a rate of 3℃ / h, and the relative humidity maintained at 85%, and curing for 4 days; the third stage is a late-term standard curing stage, with the temperature decreased to 18℃ at a rate of 1℃ / h, and the relative humidity maintained at ≥80%, and curing continued until the specified age of 28 days.

[0030] Example 2

[0031] A geopolymer concrete, by weight, is prepared from the following raw materials: 50 parts of composite active cementitious substrate, 30 parts of continuously graded coarse aggregate, 15 parts of fine aggregate, 11 parts of composite alkali activator solution, 4 parts of in-situ self-toughening modified mineral, 1 part of functional admixture, 4 parts of other functional components, and 7 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:0.9:1.

[0032] The composite active cementitious substrate is composed of natural clay powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of 6.3:3.8:1.3. The natural clay powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling, sieving, and constant-temperature drying. The residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 68%, alumina content 15%, and total alkali metal content not exceeding 2.5%. The mineral processing tailings powder... The powder is silicate-type tailings discharged from feldspar quartz sand beneficiation, which is obtained by impurity removal, ball milling and drying. The residue on a 45μm square hole sieve is ≤8%, the loss on ignition is ≤3.0%, the silica content is not less than 72%, the alumina content is not less than 14%, and the moisture content is controlled below 0.5%. The palm oil fuel ash is the original dust collected from palm empty fruit bunches, palm shells and palm fibers in palm oil biomass boilers. It is not acid washed or modified. The residue on a 45μm square hole sieve is ≤5%, and the loss on ignition is ≤4.5%.

[0033] The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone, with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm river sand, with a fineness modulus of 2.5 and a mud content ≤3.0%, conforming to GB / T 14684 standard; the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.2, a solid content of 35%, and an admixture amount of 73% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 7% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 0.5% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0034] The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature. The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, and mixing them at a mass ratio of 2.3:1 to obtain platy composite mineral powder with an average particle size of 30 μm; spraying the powder with 0.7 mol / L sodium bicarbonate solution at room temperature while stirring for 6 min, and continuing to stir for 12 min after spraying; air-drying naturally, and then drying at 65℃ for 2.3 h; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0035] The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of 0.8:1.5:1.3; the average diameter of the wollastonite mineral fibers is 6 μm, and the aspect ratio is 23:1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 1.5 nm and a sheet diameter of 100 nm.

[0036] A method for preparing the aforementioned geopolymer concrete includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; compacting the mixture in a standard mold on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 21 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete. The segmented gradient temperature and humidity curing is divided into three stages: the first stage is an early moist curing stage, with the temperature controlled at 24℃ and the relative humidity ≥90%, for 3.3 days; the second stage is a mid-term temperature-increasing curing stage, with the temperature increased to 43℃ at a rate of 3.5℃ / h, maintaining a relative humidity of 86%, for 4.2 days; and the third stage is a late-term standard curing stage, with the temperature decreased to 19℃ at a rate of 1.5℃ / h, maintaining a relative humidity ≥80%, and continuing curing to the specified age of 28 days.

[0037] Example 3

[0038] A geopolymer concrete, by weight, is prepared from the following raw materials: 55 parts of composite active cementitious substrate, 33 parts of continuously graded coarse aggregate, 18 parts of fine aggregate, 12 parts of composite alkali activator solution, 5 parts of in-situ self-toughening modified mineral, 1.5 parts of functional admixture, 4.5 parts of other functional components, and 9 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:1:1.

[0039] The composite active cementitious substrate is composed of natural clay powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of 6.5:3.5:1.5. The natural clay powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling, sieving, and constant-temperature drying. The residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 70%, alumina content 15%, and total alkali metal content not exceeding 2.5%. The mineral processing tailings powder... The powder is silicate-type tailings discharged from feldspar quartz sand beneficiation, which is obtained by impurity removal, ball milling and drying. The residue on a 45μm square hole sieve is ≤8%, the loss on ignition is ≤3.0%, the silica content is not less than 72%, the alumina content is not less than 14%, and the moisture content is controlled below 0.5%. The palm oil fuel ash is the original dust collected from palm empty fruit bunches, palm shells and palm fibers in palm oil biomass boilers. It is not acid washed or modified. The residue on a 45μm square hole sieve is ≤5%, and the loss on ignition is ≤4.5%.

[0040] The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone, with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand or river sand, with a fineness modulus of 2.6 and a mud content ≤3.0%, conforming to GB / T 14684 standard; the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.2, a solid content of 35%, and an admixture amount of 75% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 9% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 0.8% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0041] The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature. The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, and mixing them at a mass ratio of 2.5:1 to obtain platy composite mineral powder with an average particle size of 40 μm; spraying the powder with 0.8 mol / L sodium bicarbonate solution at room temperature while stirring for 6.5 min, and continuing to stir for 13 min after spraying; air-drying naturally, and then drying at 70℃ for 2.5 h; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0042] The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of 1:2:1.4; the average diameter of the wollastonite mineral fibers is 6.5 μm and the aspect ratio is 25:1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 2 nm and a sheet diameter of 130 nm.

[0043] A method for preparing the aforementioned geopolymer concrete includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; compacting the mixture in a standard mold on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 22 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete. The segmented gradient temperature and humidity curing is divided into three stages: the first stage is an early moist curing stage, with the temperature controlled at 25℃ and the relative humidity ≥90%, for 3.5 days; the second stage is a mid-term temperature-increasing curing stage, with the temperature increased to 45℃ at a rate of 4℃ / h, maintaining a relative humidity of 88%, for 4.5 days; and the third stage is a late-term standard curing stage, with the temperature decreased to 20℃ at a rate of 2℃ / h, maintaining a relative humidity ≥80%, and continuing curing to the specified age of 28 days.

[0044] Example 4

[0045] A geopolymer concrete, by weight, is prepared from the following raw materials: 60 parts of composite active cementitious substrate, 36 parts of continuously graded coarse aggregate, 20 parts of fine aggregate, 13 parts of composite alkali activator solution, 7 parts of in-situ self-toughening modified minerals, 2.3 parts of functional admixture, 5.5 parts of other functional components, and 13 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:1.1:1.

[0046] The composite active cementitious substrate is composed of natural clay powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of 6.8:3.3:1.8. The natural clay powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling, sieving, and constant-temperature drying. The residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 73%, alumina content 16%, and total alkali metal content not exceeding 2.5%. The mineral processing tailings powder... The powder is silicate-type tailings discharged from feldspar quartz sand beneficiation, which is obtained by impurity removal, ball milling and drying. The residue on a 45μm square hole sieve is ≤8%, the loss on ignition is ≤3.0%, the silica content is not less than 72%, the alumina content is not less than 14%, and the moisture content is controlled below 0.5%. The palm oil fuel ash is the original dust collected from palm empty fruit bunches, palm shells and palm fibers in palm oil biomass boilers. It is not acid washed or modified. The residue on a 45μm square hole sieve is ≤5%, and the loss on ignition is ≤4.5%.

[0047] The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone, with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand or river sand, with a fineness modulus of 2.7 and a mud content ≤3.0%, conforming to GB / T 14684 standard; the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.3, a solid content of 36%, and an admixture amount of 78% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 11% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 0.9% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0048] The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature. The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, and mixing them at a mass ratio of 2.8:1 to obtain platy composite mineral powder with an average particle size of 55 μm; spraying the powder with a 1 mol / L sodium bicarbonate solution at room temperature while stirring for 7.5 min, and continuing to stir for 14 min after spraying; air-drying naturally, and then drying at 75℃ for 2.8 h; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0049] The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of 1.3:2.5:1.4; the average diameter of the wollastonite mineral fibers is 7.5 μm, and the aspect ratio is 28:1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 2.5 nm and a sheet diameter of 180 nm.

[0050] A method for preparing the aforementioned geopolymer concrete includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; compacting the mixture in a standard mold on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 23 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete. The segmented gradient temperature and humidity curing is divided into three stages: the first stage is an early moist curing stage, with the temperature controlled at 27℃ and the relative humidity ≥90%, for 3.8 days; the second stage is a mid-term temperature-increasing curing stage, with the temperature increased to 48℃ at a rate of 4.5℃ / h, maintaining a relative humidity of 89%, for 4.8 days; and the third stage is a late-term standard curing stage, with the temperature decreased to 21℃ at a rate of 2.5℃ / h, maintaining a relative humidity ≥80%, and continuing curing to the specified age of 28 days.

[0051] Example 5

[0052] A geopolymer concrete, by weight, is prepared from the following raw materials: 65 parts of composite active cementitious substrate, 38 parts of continuously graded coarse aggregate, 22 parts of fine aggregate, 15 parts of composite alkali activator solution, 8 parts of in-situ self-toughening modified minerals, 2.5 parts of functional admixture, 6 parts of other functional components, and 14 parts of water; wherein the functional admixture is a polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:1.2:1.

[0053] The composite active cementitious substrate is composed of natural clay powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of 7:3:2. The natural clay powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling, sieving, and constant-temperature drying. The residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 75%, alumina content 18%, and total alkali metal content not exceeding 2.5%. The mineral processing tailings powder is... The silicate-type tailings discharged from the beneficiation of quartz sand are obtained by removing impurities, ball milling, and drying. The tailings have a sieve residue of ≤8% on a 45μm square hole sieve, a loss on ignition of ≤3.0%, a silica content of not less than 72%, an alumina content of not less than 14%, and a moisture content controlled below 0.5%. The palm oil fuel ash is the original dust collected from palm empty fruit bunches, palm shells, and palm fibers in palm oil biomass boilers. It is not subjected to acid washing or modification treatment. The tailings have a sieve residue of ≤5% on a 45μm square hole sieve and a loss on ignition of ≤4.5%.

[0054] The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone, with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand or river sand, with a fineness modulus of 2.9 and a mud content ≤3.0%, conforming to GB / T 14684 standard; the composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water, wherein the industrial sodium silicate water glass has a modulus of 3.3, a solid content of 36%, and an admixture amount of 80% of the total mass of the composite alkali activator solution; the flake sodium hydroxide admixture amount is 12% of the total mass of the composite alkali activator solution; the pentahydrate borax admixture amount is 1.0% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

[0055] The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature. The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, and mixing them at a mass ratio of 3:1 to obtain platy composite mineral powder with an average particle size of 60 μm; spraying the powder with a 1.2 mol / L sodium bicarbonate solution at room temperature while stirring for 8 min, and continuing to stir for 15 min after spraying; air-drying naturally, and then drying at 80℃ for 3 h; cooling and sealing to obtain the in-situ self-toughening modified mineral.

[0056] The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of 1.5:3:1.5; the average diameter of the wollastonite mineral fibers is 8 μm, and the aspect ratio is 30:1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 3 nm and a sheet diameter of 200 nm.

[0057] A method for preparing the aforementioned geopolymer concrete includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; compacting the mixture in a standard mold on a vibrating table, smoothing the surface, and allowing it to stand at room temperature for 24 hours before demolding; and using segmented gradient temperature and humidity curing to obtain the finished geopolymer concrete. The segmented gradient temperature and humidity curing is divided into three stages: the first stage is an early moist curing stage, where the temperature is controlled at 28℃ and the relative humidity is ≥90%, and the curing time is 4 days; the second stage is a mid-term temperature-increasing curing stage, where the temperature is increased to 50℃ at a rate of 5℃ / h, and the relative humidity is maintained at 90%, and the curing time is 5 days; the third stage is a late-term standard curing stage, where the temperature is decreased to 22℃ at a rate of 3℃ / h, and the relative humidity is maintained at ≥80%, and the curing time is continued until the specified age of 28 days.

[0058] Comparative Example 1 A geopolymer concrete and its preparation method are basically the same as those in Example 5, except that an equal amount of sodium saccharin is used instead of 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid.

[0059] Comparative Example 2 A geopolymer concrete and its preparation method are basically the same as those in Example 5, except that an equal amount of 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid is used instead of sodium saccharin.

[0060] Comparative Example 3 A geopolymer concrete and its preparation method are basically the same as in Example 5, except that no other functional components are added.

[0061] To further illustrate the unexpected positive technical effects achieved by the present invention, the relevant properties of the geopolymer concrete in Example 5 and Comparative Examples 1-3 were tested. The test results are shown in Table 1, and the test methods are as follows: (1) Compressive strength: The test was conducted in accordance with GB / T 50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete". The test was conducted on a 150mm×150mm×150mm cube specimen after curing for 28 days, with a loading rate of 1.0MPa / s.

[0062] (2) Impermeability: The test was conducted in accordance with GB / T 50082-2009 "Standard for Test Methods of Long-term Performance and Durability of Ordinary Concrete", using the water penetration height method, with specimen size of 175mm×185mm×150mm; (3) Freeze resistance: Refer to GB / T 50082-2009, rapid freezing method, freeze-thaw cycle 300 times, test the mass loss rate; (4) Drying shrinkage rate: Refer to GB / T 50082-2009, contact method, test the drying shrinkage rate after 28 days.

[0063] Table 1 As shown in Table 1, the geopolymer concrete in Example 5 achieved a compressive strength of 62.1 MPa, representing increases of approximately 21.1%, 22.5%, and 31.6% compared to Comparative Examples 1-3, respectively. It also achieved a permeability grade of P12, a mass loss rate of only 1.25% after 300 freeze-thaw cycles, and a 28-day drying shrinkage rate as low as 220 × 10⁻⁶. -6 The performance of the composite admixture system is significantly better than that of the comparative sample containing 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid, sodium saccharin or other functional components, which fully demonstrates the synergistic effect of the composite admixture system and functional components of the present invention, and greatly improves the mechanical properties, impermeability, freeze-thaw resistance and volume stability of geopolymer concrete.

[0064] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be used to limit the scope of protection of the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A geopolymer concrete, characterized in that, The product is prepared from the following raw materials in parts by weight: 45-65 parts of composite active cementitious substrate, 28-38 parts of continuously graded coarse aggregate, 12-22 parts of fine aggregate, 9-15 parts of composite alkali activator solution, 3-8 parts of in-situ self-toughening modified mineral, 0.6-2.5 parts of functional additives, 3-6 parts of other functional components, and 5-14 parts of water; the functional additives are polycarboxylate-based high-performance water-reducing agent, sodium saccharin, and 3-(cyclohexylamine)-2-hydroxy-1-propanesulfonic acid compounded in a mass ratio of 2:(0.8-1.2):

1.

2. The geopolymer concrete according to claim 1, characterized in that, The composite active cementitious substrate is a mixture of natural soil powder, mineral processing tailings powder, and palm oil fuel ash in a mass ratio of (6-7):(4-3):(1-2).

3. The geopolymer concrete according to claim 2, characterized in that, The natural soil powder is deep-seated primary low-alkali silica-alumina weathered clay, obtained through impurity removal, coarse crushing, ball milling and sieving, and constant-temperature drying; the residue on a 45μm square-hole sieve is controlled to be ≤6%, loss on ignition ≤2.8%, moisture content ≤0.4%, silica content 65%~75%, alumina content 12%~18%, and total alkali metal content not exceeding 2.5%; the mineral processing tailings powder is silicate-type tailings discharged from feldspar quartz sand beneficiation, obtained through impurity removal, ball milling and drying, with a residue on a 45μm square-hole sieve ≤8%, loss on ignition ≤3.0%, silica content not less than 72%, alumina content not less than 14%, and moisture content controlled below 0.5%; the palm oil fuel ash is primary dust collected from palm empty fruit bunches, palm shells and palm fibers burned in palm oil biomass boilers, without acid washing and modification treatment, with a residue on a 45μm square-hole sieve ≤5% and loss on ignition ≤4.5%.

4. The geopolymer concrete according to claim 1, characterized in that, The continuously graded coarse aggregate is 5-25mm continuously graded crushed stone with a mud content ≤1.0% and a needle-like / flaky content ≤15%, conforming to GB / T 14685 standard; the fine aggregate is 0.15-4.75mm manufactured sand or river sand with a fineness modulus of 2.4-2.9 and a mud content ≤3.0%, conforming to GB / T 14684 standard.

5. The geopolymer concrete according to claim 1, characterized in that, The composite alkali activator solution is prepared by compounding industrial sodium silicate water glass, flake sodium hydroxide, pentahydrate borax, and solvent water. The industrial sodium silicate water glass has a modulus of 3.1-3.3, a solid content of 34-36%, and is added at a dosage of 70-80% of the total mass of the composite alkali activator solution; the flake sodium hydroxide is added at a dosage of 6-12% of the total mass of the composite alkali activator solution; the pentahydrate borax is added at a dosage of 0.4-1.0% of the total mass of the composite alkali activator solution; and the solvent water is deionized water.

6. The geopolymer concrete according to claim 1, characterized in that, The in-situ self-toughening modified mineral is a micron-sized illite-montmorillonite platy composite mineral modified by a weak alkali surface at room temperature.

7. The geopolymer concrete according to claim 6, characterized in that, The preparation method of the in-situ self-toughening modified mineral includes the following steps: crushing, ball milling, and sieving illite and montmorillonite raw ore respectively, and mixing them at a mass ratio of (2-3):1 to obtain a flaky composite mineral powder with an average particle size of 20-60 μm; spraying the powder with a 0.5-1.2 mol / L sodium bicarbonate solution at room temperature while stirring for 5-8 minutes, and continuing to stir for 10-15 minutes after spraying; air-drying naturally, and then drying at 60-80℃ for 2-3 hours; cooling and sealing to obtain the in-situ self-toughening modified mineral.

8. The geopolymer concrete according to claim 1, characterized in that, The polycarboxylate-based high-performance water-reducing agent is polycarboxylate-based high-performance water-reducing agent XCA-100; the other functional components are wollastonite mineral fibers, hydrated calcium silicate, and layered nano-magnesium lithium silicate compounded in a mass ratio of (0.5-1.5):(1-3):(1.2-1.5); the average diameter of the wollastonite mineral fibers is 5-8 μm, and the aspect ratio is (20-30):1; the grade of the hydrated calcium silicate is NP-CSH-10; the layered nano-magnesium lithium silicate is a synthetic soapstone-type layered silicate nanopowder with a single layer thickness of 1-3 nm and a sheet diameter of 50-200 nm.

9. A method for preparing geopolymer concrete according to any one of claims 1-8, characterized in that, The process includes the following steps: mixing the raw materials evenly according to their weight proportions to obtain a mixture; loading the mixture into a standard test mold and vibrating it on a vibrating table; smoothing the surface; allowing it to stand at room temperature for 20-24 hours before demolding; and using segmented gradient temperature and humidity curing to obtain finished geopolymer concrete.

10. The method for preparing geopolymer concrete according to claim 9, characterized in that, The segmented gradient temperature and humidity curing is divided into three stages. The first stage is the early moisturizing and quiet curing stage, where the temperature is controlled at 25±3℃ and the relative humidity is ≥90%, and the curing period is 3-4 days. The second stage is the mid-term temperature-increasing curing stage, where the temperature is increased to 45±5℃ at a rate of 3-5℃ / h, and the relative humidity is maintained at 85%~90%, and the curing period is 4-5 days. The third stage is the late standard curing stage, where the temperature is decreased to 20±2℃ at a rate of 1-3℃ / h, and the relative humidity is maintained at ≥80%, and the curing continues until the specified age of 28 days.

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