Coal-based solid waste-based cementitious material, derived high-performance concrete and preparation method

Abstract

The present application relates to a kind of coal-based solid waste-based cementitious material, derived high-performance concrete and preparation method, belong to environmental protection building material field.The present application first provides a kind of coal gangue, fly ash, slag, coal gasification ash four coal-based solid waste and the mixture of mineral powder as precursor, with modified sodium silicate solution, sunflower stalk ash and corn stalk ash compound as composite alkali activator, with water-reducing agent and water as the mixing aqueous solution of preparation of coal-based solid waste-based cementitious material.The modified material is all solid waste system, meets the green environmental protection requirement of new era building material.Further, the present application also provides the derived high-performance concrete based on above-mentioned cementitious material, help economic benefit and ecological benefit synergic development.

Description

Technical Field

[0001] This invention belongs to the field of environmentally friendly building materials technology, specifically relating to a coal-based solid waste-based cementitious material, derived high-performance concrete, preparation method, and its application in the construction field. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] my country faces immense pressure in the disposal and treatment of multi-source solid waste. Statistics show that the total accumulated solid waste in my country has exceeded 70 billion tons, with over 4 billion tons of new bulk solid waste added annually, including 1.5 billion tons of coal-based solid waste. After its generation, coal-based solid waste is mostly disposed of through landfill or stockpiling, or used to produce low-value products, resulting in extremely low utilization rates and added value. Therefore, given the significant demand for coal-based solid waste treatment and the difficulty in high-value utilization, it is urgent to overcome the challenges of coal-based solid waste utilization and promote resource recovery and high-value utilization to support resource utilization and environmental protection.

[0004] Cement is the most commonly used cementitious material, and cement and its derivatives are widely used around the world. It is estimated that global cement production reached approximately 4.4 billion tons in 2022. The high carbon footprint of cement production has gradually drawn attention, and the construction industry is placing higher green requirements on countries worldwide. Existing building materials are undergoing a new round of structural adjustments, with a faster diversification of raw materials and a shift in development focus towards the utilization of industrial solid waste. Green and low-carbon development has become a trend, and utilizing bulk solid waste to prepare high-performance cementitious materials to replace cement has become an important research topic. Summary of the Invention

[0005] The main objective of this invention is to address the shortcomings of the aforementioned background technology, further improve the utilization rate and added value of coal-based solid waste, and provide a coal-based solid waste-based cementitious material, derived high-performance concrete, and its preparation method, so as to realize the resource utilization of coal-based solid wastes such as coal gangue, fly ash, slag, and coal gasification ash, and promote the development of a circular economy.

[0006] In a first aspect, this invention provides a coal-based solid waste-based cementitious material, formed by mixing a precursor with a composite alkali activator and water. The optimized cementitious material of this invention exhibits properties close to cement under normal temperature and standard curing conditions, and can, to a certain extent, replace silicate cement, achieving good results. The main silicon-aluminum source in this cementitious material is coal gangue. The coal gangue selected in this invention is unprocessed coal gangue, whose main chemical components are SiO2 and Al2O3, with a total mass fraction of SiO2 and Al2O3 > 80% and a silicon-aluminum ratio of 3.39. The coal gangue is crushed and ground to a specific surface area > 300 m². 2 / kg, calcined at a constant temperature in a high-temperature furnace, and after calcination at 650℃ for 2 hours, it was mixed with other solid wastes to form a precursor material.

[0007] The main mineral composition of coal gangue consists of clay minerals such as montmorillonite and kaolinite, as well as quartz. It exhibits almost no hydration activity at room temperature, requiring mechanical activation and high-temperature calcination to compensate for its insufficient activity. By blending it with solid wastes such as fly ash, slag, and coal gasification ash, the synergistic and complementary effects of multiple solid waste sources are utilized, improving the utilization efficiency of coal gangue. Furthermore, by combining it with various alkaline activators, the activation efficiency of coal gangue is further enhanced, promoting the formation of more hydration products. In addition, by blending it with high-calcium mineral admixtures, the formation of hydration products such as CSH and C-(A)-SH can be promoted, thus ensuring that the prepared coal-based solid waste-based cementitious material has a dense structure and excellent workability.

[0008] Fly ash is a widely used industrial by-product with good potential hydration activity. It contains abundant isometallic oxides, with a total mass fraction of SiO2 and Al2O3 >75% and a silicon-to-aluminum ratio of 1.76. Under the action of a composite alkali activator, the silica-alumina glassy phase gradually dissolves and repolymerizes to form a network structure, generating strength. Furthermore, the spherical particles of fly ash have a filling and lubricating effect in the material system, thus benefiting the workability and performance of cementitious materials. Slag contains a large amount of active aluminosilicates, with a total mass fraction of SiO2 and Al2O3 >85% and a silicon-to-aluminum ratio of 2.05. Under the action of a composite alkali activator, it can enhance the reactivity and later-stage strength of the system. The main components of coal gasification ash are SiO2, Al2O3, and CaO, with a total mass fraction of these three chemical components >60%. Therefore, it can provide necessary reaction products for the material system, promoting the formation of hydration products such as CSH and C-(A)-SH. The common characteristic of the aforementioned coal-based solid wastes is that they are rich in aluminosilicate minerals but lack calcium, an important element for alkali-activated materials. Mineral powder, being the solid waste with the highest glass content, has extremely high comprehensive utilization value. It contains a large amount of active CaO, SiO2, and Al2O3, with the mass fraction of CaO typically exceeding 40%, thus serving as a good calcium source for this invention. By rationally combining the above-mentioned solid wastes, a dense cementitious material with excellent mechanical properties can be prepared.

[0009] This invention, based on the mechanical activation and calcination of coal gangue, formulates an economical, readily available, environmentally friendly, and high-performance composite alkaline activator according to the combined effect of different ions. Under the combined action of commercial alkaline reagents, alkali metal oxides, and calcium-silicon-aluminum oxides, it can rapidly break down and dissolve the Si-O and Al-O bonds on the surface of precursor particles, thereby promoting the dissolution of more Si. 4+ And Al 4+ These substances participate in the hydration reaction earlier, improving early strength and ensuring high strength in later stages.

[0010] Based on the above technical effects, the specific solution of the coal-based solid waste-based cementitious material of the first aspect of the present invention is as follows: The coal-based solid waste-based cementitious material is composed of a precursor, a composite alkali activator, and a mixing aqueous solution, wherein the precursor is composed of the following raw materials in corresponding mass fractions:

[0011] Calcined coal gangue powder: 30%

[0012] Fly ash and slag: 30%-40%

[0013] Coal gasification ash residue: 20%

[0014] Mineral powder: 10%-20%

[0015] The composite alkali activator comprises modified sodium silicate solution, sunflower stalk ash, and corn stalk ash, and its dosage as a percentage of the precursor's mass is:

[0016] Modified sodium silicate solution: 4%-12%

[0017] Sunflower stalk ash: 8%-16%

[0018] Corn stalk ash: 5%-11%

[0019] The mixing aqueous solution comprises water and a shrinkage-reducing agent, the amount of which, as a percentage of the mass of the precursor, is:

[0020] Water: 60%

[0021] Shrinkage reducing agent: 0.05%-0.2%.

[0022] Regarding the precursor material in the above-mentioned solution, the present invention also has the following preferred solutions:

[0023] The calcined coal gangue powder in the precursor is formed by crushing and grinding raw coal gangue followed by high-temperature calcination. This mechanically activated calcined coal gangue powder has a specific surface area >300 m². 2 / kg, total mass fraction of SiO2 and Al2O3 > 80%.

[0024] The fly ash is secondary fly ash, with a residue of no more than 25% on a 45μm square mesh sieve, and a total mass fraction of SiO2 and Al2O3 > 75%.

[0025] The slag, after grinding, has a particle size of 42–48 μm and a total mass fraction of SiO2 and Al2O3 > 85%.

[0026] The coal gasification ash residue, after grinding, has a particle size of 32-40 μm and a total mass fraction of SiO2, Al2O3 and CaO > 60%.

[0027] The mineral powder has an activity level of S105, an average particle size of 10-16 μm, a CaO mass fraction of >40%, and a total SiO2 and Al2O3 mass fraction of >35%.

[0028] The composite alkali activator described in the above scheme, the present invention also has the following preferred embodiments:

[0029] The modified sodium silicate solution was prepared by mixing NaOH and sodium silicate solution. The NaOH was commercially available granular NaOH with a purity ≥99%, and the sodium silicate solution was commercially available industrial-grade liquid water glass with a modulus (ratio of molar silica to sodium oxide) of 3.3, a solid content of 34.9%, and a Baumé degree of 39.5. The purpose of preparing the modified sodium silicate solution was to obtain sodium silicate solutions with different moduli. Too high or too low a modulus of sodium silicate solution would have a very adverse effect on the gelation process of the alkali-activated reaction. When preparing the composite alkali activator, an appropriate amount of NaOH was added to the sodium silicate solution to obtain a modified sodium silicate solution with a modulus range of 1.0-2.0. The solution was then sealed and left to stand for 24 hours before use to further improve the activation effect of the composite alkali activator.

[0030] The sunflower stalk ash, after being ground, has a particle size of 5-8 μm, a K2O mass fraction >30%, and a total CaO and SiO2 mass fraction >30%.

[0031] The corn stalk ash, after being ground, has a particle size of 17–20 μm, a K2O mass fraction >10%, and a total mass fraction of CaO, SiO2, and Al2O3 >50%.

[0032] In the above scheme, the shrinkage reducing agent used in the mixing aqueous solution is a commercially available industrial-grade white powder with an effective ingredient content of ≥99%.

[0033] In a second aspect, the present invention provides a method for preparing the above-mentioned coal-based solid waste-based cementitious material, comprising the following steps:

[0034] The precursor, composite alkali activator, and mixing aqueous solution were prepared separately. The precursor was stirred at 30-60 rpm / min until homogeneous. Then, the composite alkali activator and mixing aqueous solution were added and stirred at 30-60 rpm / min for 50-70 seconds. The mixture was then stirred at 100-200 rpm / min for at least 3 minutes until homogeneous to obtain the sample. The prepared sample was poured into the corresponding mold and placed in a constant temperature and humidity standard curing chamber for 3 to 28 days to obtain the final product.

[0035] The precursor is prepared as follows:

[0036] (1) The raw coal gangue is crushed, screened, ground, and mechanically activated to a specific surface area > 300 m². 2 / kg, calcined at 640-660℃ for 1-3 hours to obtain calcined coal gangue powder for later use;

[0037] (2) The calcined coal gangue powder, fly ash and slag, coal gasification ash and mineral powder are mixed according to the mass percentage to prepare a precursor of coal-based solid waste cementitious material for later use.

[0038] The compound alkali activator is prepared as follows:

[0039] (1) Prepare the modified sodium silicate solution with a modulus range of 1.0-2.0, seal it and let it stand for 20-26 hours before use;

[0040] (2) The modified sodium silicate solution, sunflower stalk ash and corn stalk ash are mixed according to the mass percentage to prepare a composite alkali activator for coal-based solid waste cementitious materials for later use.

[0041] Furthermore, in step (1), the modified sodium silicate solution in the composite alkali activator is left to stand for 24 hours, which can further improve the activation effect of the composite alkali activator.

[0042] The mixing aqueous solution is prepared as follows: the shrinkage reducing agent is stirred evenly with water to obtain a mixing aqueous solution for later use;

[0043] Preferably, the liquid-to-solid ratio of the material system composed of the precursor, the composite alkali activator, and the mixing aqueous solution is 0.6.

[0044] In addition, the curing parameters in the above-mentioned constant temperature and humidity standard curing chamber adopt conventional methods in this field, such as 20℃±0.5℃, RH≥95%.

[0045] The above-mentioned coal-based solid waste-based cementitious materials were measured to have a flowability >215mm, a shrinkage rate of 0.04%-0.15%, an initial setting time of 85min-215min, a final setting time of 165min-345min, a 3-day compressive strength of 7.09MPa-16.18MPa, a 28-day compressive strength of 12.75MPa-25.33MPa, a flexural-compression ratio range of 0.24-0.31, and a porosity range of 23.6%-27.4%.

[0046] The precursor of this invention's coal-based solid waste-based cementitious material is a complete solid waste system, composed entirely of solid waste such as coal gangue and fly ash, without the addition of cement. The composite alkali activator uses sunflower stalk ash and corn stalk ash to provide partial alkalinity, while simultaneously increasing the calcium, silicon, and aluminum content and later-stage strength of the material system, thus reducing the amount of commercial alkaline reagents used. The cost and environmental impact of coal-based solid waste-based cementitious materials mainly depend on the cement content and the amount of commercial alkaline reagents. This invention reduces the cost, energy consumption, and carbon emissions of coal-based solid waste-based cementitious materials by addressing both the precursor and alkali activator aspects. Calculations show that the cost of this invention's coal-based solid waste-based cementitious material is approximately 40%-60% of that of ordinary Portland cement. If it can partially replace Portland cement in the preparation of grouting materials with low strength requirements, it is expected to generate significant economic and social benefits.

[0047] Thirdly, a derivative high-performance concrete is provided, composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in the first aspect, with the following mass fractions of each raw material:

[0048] Coal-based solid waste-based cementitious materials: 25%-35%

[0049] Aggregate: 63%-74%

[0050] Admixture: 1%-2%

[0051] The aggregate includes fine aggregate and coarse aggregate. The fine aggregate is manufactured sand, and the coarse aggregate is coarse coal gangue aggregate and fine stone coarse aggregate. The proportion of the coarse aggregate to the total mass of the aggregate is as follows:

[0052] Manufactured sand: 30%

[0053] Gangue coarse aggregate: 30%

[0054] Fine stone and coarse aggregate: 40%

[0055] The admixtures include polycarboxylate superplasticizers and early-strength agents. The early-strength agents include calcium chloride, sodium sulfate, and CSH gel-type early-strength agents, and their dosage as a percentage of the mass of the aggregate is:

[0056] Polycarboxylate superplasticizer: 20%-40%

[0057] Calcium chloride and sodium sulfate: 40%-60%

[0058] Calcium formate: 20%.

[0059] The aggregate described in the above scheme, the present invention also has the following preferred technical solutions:

[0060] The manufactured sand is sand processed by a sand making machine, with a particle size range of 0.15mm-2.36mm.

[0061] The coarse aggregate of coal gangue is the aggregate obtained after coal gangue has been crushed, screened and impurities removed, with a particle size range of 4.75-16mm.

[0062] The particle size range of the fine stone coarse aggregate is 5mm-15mm.

[0063] Regarding the admixtures described in the above scheme, the present invention also has the following preferred technical solutions:

[0064] The polycarboxylate superplasticizer is a commercially available industrial-grade white powder with a solid content ≥98% and a water reduction rate of 36.2%.

[0065] The calcium chloride and sodium sulfate are commercially available industrial-grade white powders with an effective content of not less than 99%.

[0066] The calcium formate is a commercially available industrial-grade white crystalline powder with an effective content of ≥99.8%.

[0067] Weigh each component according to the above proportions and set aside. Mix all components to obtain a derivative high-performance concrete. Attached Figure Description

[0068] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0069] Figure 1 This is a flowchart illustrating the preparation process of coal-based solid waste-based cementitious materials according to the present invention.

[0070] Figure 2 This is a scanning electron microscope image of the coal-based solid waste-based cementitious material of Embodiment 1 of the present invention;

[0071] The left image is a microscopic electron microscope scan of the aforementioned cementitious material, and the right image is a microscopic electron microscope scan of another part of the same material. Detailed Implementation

[0072] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0073] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0074] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0075] In the following embodiments, the relevant parameter testing criteria for the coal-based solid waste-based cementitious material or derived high-performance concrete are as follows:

[0076] Flowability test: GB / T2410-2016 "Method for Determination of Flowability of Cement Mortar";

[0077] Shrinkage rate testing: JGJ / T70-2009 "Standard for Test Methods of Basic Performance of Building Mortar";

[0078] Initial and final setting time testing: GB / T 1346-2011 "Standard water requirement, setting time and soundness test methods for cement";

[0079] Compressive and flexural strength testing: GB / T 17671-2020 "Test Method for Strength of Cement Mortar (ISO Method)" was used to form specimens, and then the flexural and compressive strength of the slurry aggregate of the material was tested using an integrated flexural and compressive strength testing machine;

[0080] Porosity testing: The specimens were molded according to GB / T 17671-2020 "Test Method for Strength of Cement Mortar (ISO Method)" and then the porosity of the material slurry aggregate was tested using a low-field nuclear magnetic resonance spectrometer.

[0081] The raw materials and their properties used in Examples 1-6 are as follows:

[0082] In Examples 1-6, the main silicon and aluminum source mixtures are calcined coal gangue powder, coal gasification ash, fly ash and slag, and the main calcium source is mineral powder. The coal gasification ash also provides a certain amount of CaO.

[0083] Calcined coal gangue powder is obtained from raw coal gangue through mechanical activation and high-temperature calcination. The main chemical components of raw coal gangue are SiO2 and Al2O3, with a total mass fraction of SiO2 and Al2O3 > 80%, a silicon-to-aluminum ratio of 3.39, and a specific surface area of ​​calcined coal gangue powder > 300 m². 2 / kg.

[0084] The average particle size of the coal gasification ash after grinding is 37.62 μm, and its main components are SiO2, Al2O3 and CaO, with a total mass fraction of the three chemical components >60%. The fly ash is secondary fly ash, with a residue of no more than 25% on a 45 μm square hole sieve, of which the total mass fraction of SiO2 and Al2O3 is >75%, and its silicon-aluminum ratio is 1.76. The average particle size of the slag after grinding is 45.33 μm, the total mass fraction of SiO2 and Al2O3 is >85%, and the silicon-aluminum ratio is 2.05.

[0085] The mineral powder contains a large amount of active CaO, SiO2 and Al2O3, with the mass fraction of CaO usually >40% and the total mass fraction of SiO2 and Al2O3 >35%. Its activity is S105 grade and the average particle size is 13.58μm.

[0086] The NaOH is commercially available granular NaOH with a purity ≥99%. The sodium silicate solution is commercially available industrial-grade liquid water glass with a modulus (ratio of molar silica to sodium oxide) of 3.3, a solid content of 34.9%, and a Baumé degree of 39.5. The modulus range of the modified sodium silicate solution prepared by mixing the two is 1.0-2.0.

[0087] The sunflower stalk ash contains K2O mass fraction >30%, CaO and SiO2 total mass fraction >30%, and the average particle size after grinding is 6.58μm.

[0088] The corn stalk ash contains K2O mass fraction >10%, and the total mass fraction of CaO, SiO2 and Al2O3 >50%. The average particle size after grinding is 19.47μm.

[0089] The shrinkage reducer is a commercially available industrial-grade white powder with an active ingredient content of ≥99%.

[0090] ① Coal-based solid waste precursor: 30% calcined coal gangue powder, 30%-40% fly ash and slag, 20% coal gasification ash, and 10%-20% mineral powder; ② Composite alkali activator: 4%-12% modified sodium silicate solution (as a precursor), 8%-16% sunflower stalk ash (as a precursor), and 5%-11% corn stalk ash (as a precursor); ③ Mixing aqueous solution: 60% water (as a precursor) and 0.05%-0.2% shrinkage reducer (as a precursor).

[0091] The coal-based solid waste-based cementitious material is characterized by the following steps in its preparation method:

[0092] (1) The raw coal gangue is crushed, screened, ground, and mechanically activated to a specific surface area > 300 m². 2 / kg, and then calcined in a muffle furnace at 650℃ for 2 hours to obtain calcined coal gangue powder for later use;

[0093] (2) The calcined coal gangue powder, fly ash and slag, coal gasification ash and mineral powder are mixed in a specific mass percentage to prepare a precursor of coal-based solid waste cementitious material for later use.

[0094] (3) Prepare the modified sodium silicate solution in the composite alkali activator by mixing NaOH reagent with silicate solution according to the mass calculation to obtain a modified sodium silicate solution with a modulus range of 1.0-2.0, seal and place for 24 hours for later use, so as to further improve the activation effect of the composite alkali activator.

[0095] (4) The modified sodium silicate solution, sunflower stalk ash and corn stalk ash are mixed in a specific mass percentage to prepare a composite alkali activator for coal-based solid waste cementitious materials for later use.

[0096] (5) Stir the shrinkage reducing agent with water until uniform to obtain a mixed aqueous solution for later use;

[0097] (6) When preparing coal-based solid waste-based cementitious materials, first put the precursor into a cement mortar mixer and stir at 50 rpm / min for 60 s. After stirring evenly, add the composite alkali activator and the mixing aqueous solution and stir at 50 rpm / min for 60 s. Then stir at 100-200 rpm / min for no less than 3 minutes until the mixture is evenly mixed to obtain the sample. The liquid-solid ratio of the material system composed of the precursor, composite alkali activator and mixing aqueous solution is 0.6.

[0098] (7) The prepared sample is poured into a corresponding mold of 4cm×4cm×16cm and placed in a constant temperature and humidity standard curing box (20℃±0.5℃, RH≥95%) for curing for 3 to 28 days to obtain the coal-based solid waste cementitious material stone body of the present invention.

[0099] Example 1

[0100] This embodiment provides a coal-based solid waste-based cementitious material, which consists of a precursor, a composite alkali activator, and a mixing aqueous solution. The precursor includes calcined coal gangue powder, fly ash, slag, coal gasification ash, and mineral powder. The composite alkali activator includes modified sodium silicate solution, sunflower stalk ash, and corn stalk ash. The mixing aqueous solution includes water and a shrinkage reducing agent. The precursor is composed of the following materials in corresponding mass fractions:

[0101] Calcined coal gangue powder: 30%

[0102] Coal gasification ash residue: 20%

[0103] Mineral powder: 10%

[0104] Fly ash and slag: 40%

[0105] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0106] Modified sodium silicate solution: 8% (as a percentage of the precursor)

[0107] Sunflower stalk ash: 8% (of the precursors)

[0108] Corn stalk ash: 11% (of the precursors)

[0109] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions.

[0110] Water: 60% (of the precursor)

[0111] Shrinkage reducing agent: 0.15% (percentage of precursor)

[0112] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0113] Example 2

[0114] This embodiment provides yet another coal-based solid waste-based cementitious material, composed of a precursor, a composite alkali activator, and a mixing aqueous solution, characterized in that the precursor is composed of the following materials in corresponding mass fractions:

[0115] Calcined coal gangue powder: 30%

[0116] Coal gasification ash residue: 20%

[0117] Mineral powder: 10%

[0118] Fly ash and slag: 40%

[0119] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0120] Modified sodium silicate solution: 4% (as a percentage of the precursor)

[0121] Sunflower stalk ash: 12% (of the precursors)

[0122] Corn stalk ash: 8% (of the precursors)

[0123] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions:

[0124] Water: 60% (of the precursor)

[0125] Shrinkage reducing agent: 0.05% (percentage of precursor)

[0126] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0127] Example 3

[0128] This embodiment provides yet another coal-based solid waste-based cementitious material, composed of a precursor, a composite alkali activator, and a mixing aqueous solution, characterized in that the precursor is composed of the following materials in corresponding mass fractions:

[0129] Calcined coal gangue powder: 30%

[0130] Coal gasification ash residue: 20%

[0131] Mineral powder: 15%

[0132] Fly ash and slag: 35%

[0133] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0134] Modified sodium silicate solution: 8% (as a percentage of the precursor)

[0135] Sunflower stalk ash: 16% (of the precursors)

[0136] Corn stalk ash: 5% (as a precursor)

[0137] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions:

[0138] Water: 60% (of the precursor)

[0139] Shrinkage reducing agent: 0.10% (percentage of precursor)

[0140] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0141] Example 4

[0142] This embodiment provides yet another coal-based solid waste-based cementitious material, composed of a precursor, a composite alkali activator, and a mixing aqueous solution, characterized in that the precursor is composed of the following materials in corresponding mass fractions:

[0143] Calcined coal gangue powder: 30%

[0144] Coal gasification ash residue: 20%

[0145] Mineral powder: 15%

[0146] Fly ash and slag: 35%

[0147] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0148] Modified sodium silicate solution: 12% (as a percentage of the precursor)

[0149] Sunflower stalk ash: 16% (of the precursors)

[0150] Corn stalk ash: 11% (of the precursors)

[0151] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions:

[0152] Water: 60% (of the precursor)

[0153] Shrinkage reducing agent: 0.20% (percentage of precursor)

[0154] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0155] Example 5

[0156] This embodiment provides yet another coal-based solid waste-based cementitious material, composed of a precursor, a composite alkali activator, and a mixing aqueous solution, characterized in that the precursor is composed of the following materials in corresponding mass fractions:

[0157] Calcined coal gangue powder: 30%

[0158] Coal gasification ash residue: 20%

[0159] Mineral powder: 20%

[0160] Fly ash and slag: 30%

[0161] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0162] Modified sodium silicate solution: 4% (as a percentage of the precursor)

[0163] Sunflower stalk ash: 8% (of the precursors)

[0164] Corn stalk ash: 5% (as a precursor)

[0165] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions:

[0166] Water: 60% (of the precursor)

[0167] Shrinkage reducing agent: 0.15% (percentage of precursor)

[0168] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0169] Example 6

[0170] This embodiment provides yet another coal-based solid waste-based cementitious material, composed of a precursor, a composite alkali activator, and a mixing aqueous solution, characterized in that the precursor is composed of the following materials in corresponding mass fractions:

[0171] Calcined coal gangue powder: 30%

[0172] Coal gasification ash residue: 20%

[0173] Mineral powder: 20%

[0174] Fly ash and slag: 30%

[0175] The composite alkali activator is composed of the following materials in corresponding mass fractions:

[0176] Modified sodium silicate solution: 12% (as a percentage of the precursor)

[0177] Sunflower stalk ash: 12% (of the precursors)

[0178] Corn stalk ash: 8% (of the precursors)

[0179] The mixing aqueous solution is composed of the following materials in the corresponding mass fractions:

[0180] Water: 60% (of the precursor)

[0181] Shrinkage reducing agent: 0.10% (percentage of precursor)

[0182] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a coal-based solid waste-based cementitious material, and conduct performance tests according to the corresponding standards.

[0183] The mix proportions of the coal-based solid waste-based cementitious materials in Examples 1-6 are also shown in Table 1. The performance test results of the coal-based solid waste-based cementitious materials in Examples 1-6 are shown in Table 2.

[0184] Table 1. Mix proportions of coal-based solid waste-based cementitious materials in Examples 1-6

[0185]

[0186] Table 2 Performance test results of coal-based solid waste-based cementitious materials in Examples 1-6

[0187]

[0188] As can be seen from Tables 1 and 2, when comparing the groups of Examples 1 and 2, Examples 3 and 4, and Examples 5 and 6, the preparation conditions and steps were the same, and the precursor ratio and water dosage were also exactly the same. However, the slurry fluidity, initial setting time, and final setting time were smaller and shorter in the examples with higher content of composite alkali activator. This is mainly because the higher the content of composite alkali activator, the more fully the potential activity of the precursor is activated, and the easier it is to generate more gel, thereby reducing the slurry fluidity and shortening the initial and final setting times. At the same time, with the increase of the content of composite alkali activator and shrinkage reducer, the combined effect of the two reduces the porosity of the coal-based solid waste-based cementitious material.

[0189] The preparation conditions and steps were the same for all groups, including Example 1 and Example 2, Example 3 and Example 4, and Example 5 and Example 6. The precursor ratio and water dosage were also exactly the same. However, the slight change in the shrinkage-reducing agent in the mixing aqueous solution caused a significant change in the shrinkage rate of the material. The rule was that the higher the shrinkage-reducing agent content, the smaller the shrinkage rate.

[0190] Comparisons were made between Example 1 and Example 2, Example 3 and Example 4, Example 5 and Example 6, as well as between groups. The preparation conditions and steps were the same. It can be clearly seen that with the increase of mineral powder and composite alkali activator content, the 3-day and 28-day compressive strength of the coal-based solid waste cementitious material stone body increased. Mineral powder is a high-calcium mineral, and the composite alkali activator is better at activating its activity than other low-calcium silica-alumina mixtures. Therefore, the 3-day and 28-day compressive strength of the coal-based solid waste cementitious material stone body increased with the increase of mineral powder and composite alkali activator content.

[0191] The comparison between Examples 1 and 2, Examples 3 and 4, and Examples 5 and 6 showed that as the total content of sunflower stalk ash and corn stalk ash increased, the flexural-compression ratio of the coal-based solid waste cementitious material also increased.

[0192] In the following six examples of derived high-performance concrete, the raw materials and their properties are as follows:

[0193] The coal-based solid waste-based cementitious materials used in Examples 7-12 possess the characteristics described in the corresponding Examples 1-6.

[0194] Manufactured sand is sand produced by a sand making machine, with a particle size range of 0.15mm-2.36mm; coal gangue coarse aggregate is aggregate obtained after coal gangue has been crushed, screened, and impurities removed, with a particle size range of 4.75-16mm; fine stone coarse aggregate has a particle size range of 5mm-15mm.

[0195] The polycarboxylate superplasticizer is a commercially available industrial-grade white powder with a solid content ≥98% and a water reduction rate of 36.2%; calcium chloride and sodium sulfate are commercially available industrial-grade white powders with an effective ingredient content of not less than 99%; calcium formate is a commercially available industrial-grade white crystalline powder with an effective ingredient content ≥99.8%.

[0196] ① Coal-based solid waste-based cementitious materials (accounting for 25%-35% of the total); ② Aggregates (accounting for 63%-74% of the total): 30% manufactured sand, 30% coal gangue coarse aggregate, and 40% fine stone coarse aggregate; ③ Admixtures (accounting for 1%-2% of the total): 20%-40% polycarboxylate superplasticizer (accounting for aggregate), 20% calcium formate (accounting for aggregate), and 40%-60% calcium chloride and sodium sulfate (accounting for aggregate).

[0197] The derived high-performance concrete is characterized by the following steps in its preparation method:

[0198] (1) Based on the preparation methods and steps of the coal-based solid waste-based cementitious materials in Examples 1-6 above, the coal-based solid waste-based cementitious materials of Examples 1-6 are obtained for later use;

[0199] (2) The manufactured sand, coal gangue coarse aggregate and fine stone coarse aggregate are mixed according to a specific mass percentage to obtain aggregate for high-performance concrete for later use.

[0200] (3) The polycarboxylate superplasticizer, calcium formate, calcium chloride and sodium sulfate are mixed in a specific mass percentage to prepare an admixture for high-performance concrete.

[0201] (4) Mix the coal-based solid waste-based cementitious materials of Examples 1-6 with the corresponding aggregates and admixtures evenly to obtain the high-performance concrete samples derived from Examples 7-12.

[0202] Example 7

[0203] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 1. Its characteristic is that the coal-based solid waste-based cementitious material of Example 1 is composed of the following materials in corresponding mass fractions.

[0204] Example 1: Coal-based solid waste-based cementitious material: 25% (of the total)

[0205] The aggregate is composed of the following materials in the corresponding mass fractions:

[0206] Manufactured sand: 22.05% (of the total)

[0207] Coal gangue coarse aggregate: 22.05% (of the total)

[0208] Fine stone coarse aggregate: 29.4% (of the total)

[0209] The admixture is composed of the following materials in the corresponding mass fractions:

[0210] Polycarboxylate superplasticizer: 0.3% (of total)

[0211] Calcium chloride and sodium sulfate: 0.9% (of the total)

[0212] Calcium formate: 0.3% (of total)

[0213] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0214] Example 8

[0215] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 2. Its characteristic is that the coal-based solid waste-based cementitious material of Example 2 is composed of the following materials in corresponding mass fractions.

[0216] Example 2: Coal-based solid waste-based cementitious materials: 25% (of the total)

[0217] The aggregate is composed of the following materials in the corresponding mass fractions:

[0218] Manufactured sand: 21.9% (of the total)

[0219] Coal gangue coarse aggregate: 21.9% (of the total)

[0220] Fine stone coarse aggregate: 29.2% (of the total)

[0221] The admixture is composed of the following materials in the corresponding mass fractions:

[0222] Polycarboxylate superplasticizer: 0.6% (of total)

[0223] Calcium chloride and sodium sulfate: 1.0% (of total)

[0224] Calcium formate: 0.4% (of total)

[0225] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0226] Example 9

[0227] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 3. Its characteristic is that the coal-based solid waste-based cementitious material of Example 3 is composed of the following materials in corresponding mass fractions.

[0228] Example 3: Coal-based solid waste-based cementitious material: 30% (of the total)

[0229] The aggregate is composed of the following materials in the corresponding mass fractions:

[0230] Manufactured sand: 20.7% (of the total)

[0231] Coal gangue coarse aggregate: 20.7% (of the total)

[0232] Fine stone coarse aggregate: 27.6% (of the total)

[0233] The admixture is composed of the following materials in the corresponding mass fractions:

[0234] Polycarboxylate superplasticizer: 0.4% (of total)

[0235] Calcium chloride and sodium sulfate: 0.4% (of the total)

[0236] Calcium formate: 0.2% (of total)

[0237] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0238] Example 10

[0239] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 4. Its characteristic is that the coal-based solid waste-based cementitious material of Example 4 is composed of the following materials in corresponding mass fractions.

[0240] Example 4: Coal-based solid waste-based cementitious material: 30% (of the total)

[0241] The aggregate is composed of the following materials in the corresponding mass fractions:

[0242] Manufactured sand: 22.55% (of the total)

[0243] Coal gangue coarse aggregate: 22.55% (of the total)

[0244] Fine stone coarse aggregate: 27.4% (of the total)

[0245] The admixture is composed of the following materials in the corresponding mass fractions:

[0246] Polycarboxylate superplasticizer: 0.45% (of total)

[0247] Calcium chloride and sodium sulfate: 0.75% (of the total)

[0248] Calcium formate: 0.3% (of total)

[0249] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0250] Example 11

[0251] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 5. Its characteristic is that the coal-based solid waste-based cementitious material of Example 5 is composed of the following materials in corresponding mass fractions.

[0252] Example 5: Coal-based solid waste-based cementitious material: 35% (of the total)

[0253] The aggregate is composed of the following materials in the corresponding mass fractions:

[0254] Manufactured sand: 19.2% (of the total)

[0255] Coal gangue coarse aggregate: 19.2% (of the total)

[0256] Fine stone coarse aggregate: 25.6% (of the total)

[0257] The admixture is composed of the following materials in the corresponding mass fractions:

[0258] Polycarboxylate superplasticizer: 0.2% (of total)

[0259] Calcium chloride and sodium sulfate: 0.6% (of total)

[0260] Calcium formate: 0.2% (of total)

[0261] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0262] Example 12

[0263] The derived high-performance concrete provided in this embodiment is composed of the coal-based solid waste-based cementitious material, aggregate, and admixtures described in Example 6. Its characteristic is that the coal-based solid waste-based cementitious material of Example 6 is composed of the following materials in corresponding mass fractions.

[0264] Example 6: Coal-based solid waste-based cementitious material: 35% (of the total)

[0265] The aggregate is composed of the following materials in the corresponding mass fractions:

[0266] Manufactured sand: 18.9% (of the total)

[0267] Coal gangue coarse aggregate: 18.9% (of the total)

[0268] Fine stone coarse aggregate: 25.2% (of the total)

[0269] The admixture is composed of the following materials in the corresponding mass fractions:

[0270] Polycarboxylate superplasticizer: 0.8% (of total)

[0271] Calcium chloride and sodium sulfate: 0.8% (of the total)

[0272] Calcium formate: 0.4% (of total)

[0273] Weigh each component according to this ratio and set aside. Then, mix all components according to the steps described in the preparation method above to obtain a derivative high-performance concrete, and conduct performance tests according to the corresponding standards.

[0274] The mix proportions of the high-performance concrete derived from Examples 7-12 are also shown in Table 3. The performance test results of the high-performance concrete derived from Examples 7-12 are shown in Table 4.

[0275] Table 3. Mix proportions of the derived high-performance concrete from Examples 7-12

[0276]

[0277] Table 4 Performance test results of the derived high-performance concrete in Examples 7-12

[0278]

[0279]

[0280] As can be seen from Tables 3 and 4, when comparing the groups of Examples 7 and 8, Examples 9 and 10, Examples 11 and 12, as well as between groups, the preparation conditions and steps were the same. The slump of the derived high-performance concrete material increased with the increase of polycarboxylate superplasticizer content, while it gradually decreased with the increase of coal-based solid waste cementitious material content.

[0281] Comparisons were made between the groups in Examples 7 and 8, Examples 9 and 10, Examples 11 and 12, as well as between the groups. The preparation conditions and steps were the same. The initial setting time and final setting time of the derived high-performance concrete material showed a significant shortening trend with the increase of the content of composite alkali activator in the coal-based solid waste cementitious material. This is mainly because the composite alkali activator promotes the formation of gels inside the material, which is beneficial to shortening the setting time. At the same time, the increase of calcium chloride, sodium sulfate and calcium formate also helps to shorten the setting time of the material.

[0282] Comparisons were made between the groups in Examples 7 and 8, Examples 9 and 10, Examples 11 and 12, as well as between the groups. The preparation conditions and steps were the same. The 24-hour compressive strength and 28-day compressive strength of the derived high-performance concrete gradually increased with the increase of the content of composite alkali activator and mineral powder in the coal-based solid waste-based cementitious material. The mineral powder is a high-calcium mineral, and the composite alkali activator is better at activating its activity than other low-calcium silica-alumina mixtures. Therefore, the 24-hour compressive strength and 28-day compressive strength of the derived high-performance concrete gradually increased to a certain extent with the increase of the content of composite alkali activator and mineral powder in the coal-based solid waste-based cementitious material.

[0283] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., 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 coal-based solid waste-based cementitious material, characterized in that, The raw materials for the gelling material consist of a precursor, a composite alkali activator, and a mixing aqueous solution. The precursor consists of the following raw materials in the corresponding mass fractions: Calcined coal gangue powder: 30% Fly ash and slag: 30%-40% Coal gasification ash residue: 20% Mineral powder: 10%-20% The composite alkali activator comprises modified sodium silicate solution, sunflower stalk ash, and corn stalk ash, and its dosage as a percentage of the precursor's mass is: Modified sodium silicate solution: 4%-12% Sunflower stalk ash: 8%-16% Corn stalk ash: 5%-11% The mixing aqueous solution comprises water and a shrinkage-reducing agent, the amount of which, as a percentage of the mass of the precursor, is: Water: 60% Shrinkage reducing agent: 0.05%-0.2%; The calcined coal gangue powder is obtained by mechanically activating raw coal gangue. The activation method is as follows: the raw coal gangue is crushed and ground, and then calcined at high temperature. The specific surface area of ​​the calcined coal gangue powder is >300m². 2 / kg, with a total mass fraction of SiO2 and Al2O3 >80%, is calcined at a temperature of 640~660℃ for 1~3 hours to obtain calcined coal gangue powder.

2. The coal-based solid waste-based cementitious material as described in claim 1, characterized in that, The fly ash is secondary fly ash, with a residue of no more than 25% on a 45μm square mesh sieve and a total mass fraction of SiO2 and Al2O3 > 75%. Alternatively, the slag, after grinding, has a particle size of 42~48μm and a total mass fraction of SiO2 and Al2O3 >85%; Alternatively, the coal gasification ash residue, after grinding, has a particle size of 32~40μm, and the total mass fraction of SiO2, Al2O3 and CaO is >60%; Alternatively, the mineral powder has an activity level of S105, an average particle size of 10~16μm, a CaO mass fraction >40%, and a total SiO2 and Al2O3 mass fraction >35%.

3. The coal-based solid waste-based cementitious material as described in claim 1, characterized in that, The modified sodium silicate solution is prepared by mixing NaOH and sodium silicate solution, and the modulus ranges from 1.0 to 2.

0. Alternatively, the sunflower stalk ash, after being ground, has a particle size of 5-8 μm, a K2O mass fraction >30%, and a total CaO and SiO2 mass fraction >30%. Alternatively, the corn stalk ash, after being ground, has a particle size of 17-20 μm, a K2O mass fraction of >10%, and a total mass fraction of CaO, SiO2 and Al2O3 of >50%.

4. The coal-based solid waste-based cementitious material as described in claim 1, characterized in that, The shrinkage reducing agent used in the mixing aqueous solution is a commercially available industrial-grade white powder with an effective ingredient content of ≥99%.

5. The method for preparing the coal-based solid waste-based cementitious material according to any one of claims 1-4, characterized in that, Includes the following steps: The precursor, composite alkali activator, and mixing aqueous solution were prepared separately. The precursor was stirred at 30-60 rpm until homogeneous. Then, the composite alkali activator and mixing aqueous solution were added and stirred at 30-60 rpm for 50-70 seconds. The mixture was then stirred at 100-200 rpm for at least 3 minutes until homogeneous to obtain the sample. The prepared sample was poured into the corresponding mold and placed in a constant temperature and humidity standard curing chamber for 3 to 28 days to obtain the final product. The precursor is prepared as follows: (1) The raw coal gangue is crushed, screened, ground, and mechanically activated to a specific surface area > 300 m². 2 / kg, calcined at 640~660℃ for 1~3 hours to obtain calcined coal gangue powder for later use; (2) The calcined coal gangue powder, fly ash and slag, coal gasification ash and mineral powder are mixed according to the mass percentage to prepare a precursor of coal-based solid waste cementitious material for later use. The compound alkali activator is prepared as follows: (1) Prepare a modified sodium silicate solution with a modulus range of 1.0-2.0, seal it and let it stand for 20-26 hours before use; (2) The modified sodium silicate solution, sunflower stalk ash and corn stalk ash are mixed according to the mass percentage to prepare a composite alkali activator for coal-based solid waste cementitious materials for later use; The mixing aqueous solution is prepared as follows: the shrinkage reducing agent is stirred evenly with water to obtain a mixing aqueous solution for later use.

6. The preparation method of the coal-based solid waste-based cementitious material as described in claim 5, characterized in that, The liquid-to-solid ratio of the material system consisting of the precursor, the composite alkali activator, and the mixing aqueous solution is 0.

6. Alternatively, the curing parameters in the constant temperature and humidity standard curing chamber are 20℃±0.5℃ and RH≥95%.

7. A derivative high-performance concrete, characterized in that, Composed of the coal-based solid waste-based cementitious material, aggregate, and admixture as described in any one of claims 1-4, with the following mass fractions of each raw material: Coal-based solid waste-based cementitious materials: 25%-35% Aggregate: 63%-74% Admixture: 1%-2% The aggregate includes fine aggregate and coarse aggregate. The fine aggregate is manufactured sand, and the coarse aggregate is coarse coal gangue aggregate and fine stone coarse aggregate. The proportion of the coarse aggregate to the total mass of the aggregate is as follows: Manufactured sand: 30% Gangue coarse aggregate: 30% Fine stone and coarse aggregate: 40% The admixtures include polycarboxylate superplasticizers and early-strength agents. The early-strength agents include calcium chloride, sodium sulfate, and calcium formate, and their dosage as a percentage of the mass of the aggregate is: Polycarboxylate superplasticizer: 20%-40% Calcium chloride and sodium sulfate: 40%-60% Calcium formate: 20%.

8. The derived high-performance concrete as described in claim 7, characterized in that, The manufactured sand is sand processed by a sand making machine, with a particle size range of 0.15mm-2.36mm; Alternatively, the coarse aggregate of coal gangue is the aggregate obtained after crushing, screening and removing impurities from coal gangue, with a particle size range of 4.75-16mm; Alternatively, the particle size range of the fine stone coarse aggregate is 5mm-15mm.

9. The derived high-performance concrete as described in claim 7, characterized in that, The polycarboxylate superplasticizer is a commercially available industrial-grade white powder with a solid content ≥98% and a water reduction rate of 36.2%. Alternatively, the calcium chloride and sodium sulfate mentioned are commercially available industrial-grade white powders with an effective content of not less than 99%; Alternatively, the calcium formate is a commercially available industrial-grade white crystalline powder with an effective content of ≥99.8%.

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