High-strength concrete material based on alkali-activated cementing material and preparation method of high-strength concrete material

Abstract

The invention discloses a high-strength concrete material based on an alkali-activated cementing material and a preparation method of the high-strength concrete material. The high-strength concrete material is prepared from mixing water, the cementing material, aggregate and an additive, and the cementing material is composed of fly ash and reference cement; the mixing water adopts mine water; coal gangue is adopted as the aggregate; according to the invention, an optimal formula is obtained through a contrast experiment by adopting a plurality of selectable additives, so that the mechanical property of the test block is remarkably improved, and a dual-curing mechanism of physical sealing and chemical combination is realized.

Description

Technical Field

[0001] This invention belongs to the field of concrete materials technology, specifically high-strength concrete materials based on alkali-activated cementitious materials and their preparation methods. Background Technology

[0002] Alkali-activated cementitious materials are a new type of low-carbon cementitious material. They use industrial waste residue as the main raw material, have a convenient preparation process, low CO2 emissions, and excellent mechanical and durability properties, making them one of the important auxiliary cementitious materials. Traditional high-strength concrete usually uses ordinary silicate cement as the main cementitious material, but cement production has high energy consumption and large carbon emissions. Alkali-activated cementitious materials, as a potential low-environmental-impact alternative, utilize alkaline activators to activate the potential activity of aluminosilicate solid wastes such as fly ash, forming a gel structure with aluminosilicate networks as the main body, and have received extensive research.

[0003] However, existing alkaline activation techniques still have significant limitations in this specific application scenario: although commonly used strong alkaline activators (such as sodium hydroxide) can effectively dissolve the silica-alumina phase, the early strength development of the gel structure is slow, and the targeted curing ability for complex ion coexistence systems is weak; the activation system is relatively simple, making it difficult to simultaneously optimize the mechanical properties, workability, and specific chemical fixation efficiency of SO4²⁻ and Cl⁻ of the material.

[0004] Therefore, it is necessary to provide high-strength concrete materials based on alkali-activated cementitious materials and their preparation methods to solve the problems mentioned in the background art. Summary of the Invention

[0005] To achieve the above objectives, the present invention provides the following technical solution: a high-strength concrete material based on alkali-activated cementitious material, wherein the high-strength concrete material is made of mixing water, cementitious material, aggregate, and admixture, and wherein the cementitious material is composed of fly ash and reference cement.

[0006] The mixing water is mine water;

[0007] The aggregate used is coal gangue;

[0008] The additive is any one of the following: industrial water glass, industrial water glass and calcium oxide composite activator, sodium hydroxide, sodium hydroxide and calcium oxide composite activator, sodium carbonate, sodium carbonate and calcium oxide composite activator;

[0009] The mass proportions of each component in the high-strength concrete material are as follows: fly ash 30%~40%, reference cement 10%~18%, coal gangue 30%~40%, admixtures 4%~12%, and mine water accounting for 0.4~0.6% of the total mass of the cementitious material.

[0010] Furthermore, as a preferred embodiment, the ratio of the mixing water to the cementitious material and aggregate is 0.5:1.

[0011] Furthermore, as a preferred embodiment, the fly ash and coal gangue are pre-treated, crushed, and then screened to a particle size of ≤5mm;

[0012] The ratio of fly ash, reference cement and coal gangue is 2.5:1:2.5.

[0013] Furthermore, as a preferred embodiment, the industrial water glass in the additive comprises 27.3% SiO2, 8.6% Na2O, and 64.1% H2O;

[0014] The mass ratio of industrial water glass and calcium oxide composite activator in the admixture is 1:1;

[0015] The mass ratio of sodium hydroxide and calcium oxide composite activator in the admixture is 1:1;

[0016] The mass ratio of sodium carbonate and calcium oxide composite activator in the admixture is 1:1.

[0017] Furthermore, as a preferred method, a method for preparing high-strength concrete materials based on alkali-activated cementitious materials is preferred.

[0018] It includes the following steps:

[0019] S1. Material pretreatment: After crushing, coal gangue and fly ash are screened to a particle size ≤5mm, dried at 105℃ for 24h, and stored in a sealed container; The mass ratio of fly ash, cement, and coal gangue is optimized by controlling variables to achieve a ratio of fly ash, reference cement, and coal gangue of 2.5:1:2.5.

[0020] S2. Pour fly ash, cement, and coal gangue into a cement paste mixer in proportion and dry mix until uniform; adjust the admixture to a pH close to that of the mixing water, slowly add the mixing water and admixture, select automatic mixing, form a uniform paste, and ensure that the ratio of mixing water to cementitious materials and aggregates is 0.5:1.

[0021] S3. Pour the slurry into the mold, let it stand for 24 hours, and then demold.

[0022] S4. Place the concrete material in a constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of ≥95% for 28 days.

[0023] Compared with the prior art, the beneficial effects of the present invention are:

[0024] In this invention, fly ash and reference cement are used as the main cementing materials, coal gangue is added as aggregate (particle size ≤ 5mm), and mine water is selected as the mixing water. The experiment uses a variety of selectable admixtures to obtain the optimal formula through comparative experiments, which significantly improves the mechanical properties of the test blocks and realizes a dual curing mechanism of physical sealing and chemical bonding. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the average compressive strength results in the preliminary experiments of this invention;

[0026] Figure 2 This is a schematic diagram of the average compressive strength of the control experiment in this invention;

[0027] Figure 3 This is a schematic diagram of the blank group XRD test in this invention;

[0028] Figure 4 This is a schematic diagram of the XRD test of the admixture group in this invention;

[0029] Figure 5 This is a schematic diagram of chloride ion precipitation in the control experiment of this invention;

[0030] Figure 6 This is a schematic diagram of the control experiment data for sulfate ion precipitation in the present invention;

[0031] Figure 7 This is a schematic diagram of the curing test block in this invention;

[0032] Figure 8 This is a schematic diagram of the soaking test block in this invention;

[0033] Figure 9 This is a schematic diagram showing the average compressive strength of the specimen with admixture a added in this invention;

[0034] Figure 10 This is a schematic diagram showing the average compressive strength of the specimen with admixture b added in this invention;

[0035] Figure 11 This is a schematic diagram showing the average compressive strength of the specimen with admixture c added in this invention;

[0036] Figure 12 This is a schematic diagram showing the average compressive strength of the specimen with admixture d in this invention;

[0037] Figure 13 This is a schematic diagram showing the average compressive strength of the specimen with admixture e added in this invention;

[0038] Figure 14 This is a schematic diagram showing the average compressive strength of the specimen with admixture f added in this invention;

[0039] Figure 15This is a schematic diagram showing the mass of Cl⁻ leaching and precipitation in this invention;

[0040] Figure 16 This is a schematic diagram showing the precipitation mass of SO4²⁻ during immersion in this invention; Detailed Implementation

[0041] In this embodiment of the invention, a high-strength concrete material based on alkali-activated cementitious material is prepared by mixing water, cementitious material, aggregate, and admixtures, wherein the cementitious material is composed of fly ash (Xuejiawan Power Plant, Fugu County) and reference cement.

[0042] The mixing water used is mine water (Yulin Dahaize Coal Mine).

[0043] The aggregate (particle size ≤ 5mm) is coal gangue (Yulin Yuandatan Coal Mine).

[0044] The additive is any one of the following: industrial water glass, industrial water glass and calcium oxide composite activator, sodium hydroxide, sodium hydroxide and calcium oxide composite activator, sodium carbonate, sodium carbonate and calcium oxide composite activator;

[0045] The mass proportions of the components of the high-strength concrete material are as follows: fly ash 30%~40%, reference cement 10%~18%, coal gangue 30%~40%, admixture 4%~12%, and mine water accounting for 0.4~0.6% of the total mass of the cementitious material. That is to say, the mass of the mixing water (mine water) used accounts for 40% to 60% of the total mass of the cementitious material (fly ash + cement). For example: fly ash: 35%, cement: 14%, coal gangue aggregate: 35%, alkali activator: 8% (the total of the above four dry materials is 35+14+35+8 = 92%, and the remaining 8% is reserved space for water consumption in the design).

[0046] Table 1 lists the concentrations of the main ions in the mine water of Yulin Dahaize Coal Mine; Table 2 lists the main chemical composition of the fly ash from Xuejiawan Power Plant in Fugu County; Table 3 lists the main chemical composition of the cement used.

[0047] Table 1. Main chemical composition of mine water in Yulin Dahaize Coal Mine

[0048] Table 2. Main Chemical Composition of Fly Ash from Guojiawan Power Plant in Fugu County

[0049] Table 3 Main Chemical Composition of Standard Cement

[0050] In this embodiment, the mixing water to cementitious material and aggregate ratio is 0.5:1.

[0051] In a preferred embodiment, the fly ash and coal gangue are pre-treated, crushed, and then screened to a particle size ≤5mm;

[0052] The ratio of fly ash, reference cement and coal gangue is 2.5:1:2.5.

[0053] The experiment employed a preliminary approach, firstly pre-treating the materials. After crushing, both coal gangue and fly ash were sieved to a particle size ≤5mm, dried at 105℃ for 24 hours, and then stored in a sealed container. Mine water, fly ash, ordinary Portland cement, and coal gangue were used in fixed proportions (by mass).

[0054] Under the condition of maintaining the mass ratio of mine water: cementitious material + aggregate = 0.5:1, a preliminary experiment was carried out to meet the technical performance (compressive strength) of mine filling engineering. The mass ratio of fly ash, cement and coal gangue was optimized by controlling the variable method to minimize the cement content, and at the same time provide a stable benchmark ratio for subsequent proportioning experiments and soaking experiments.

[0055] Five gradient mix ratios were set up with fly ash:cement:coal gangue mass ratio (as shown in Table 2). When preparing test blocks, fly ash, cement and coal gangue were poured into a cement paste mixer (model: NJ-160A) in proportion and dry-mixed until uniform. Water glass was adjusted to a pH close to that of mine water, and the mine water and water glass solution were slowly added. Automatic stirring was selected to form a uniform paste.

[0056] The slurry was poured into a 40×40×40mm³ mold, allowed to stand for 24 hours, and then demolded. The molded blocks were marked, with 9 blocks per group, for 3-day, 7-day, and 28-day compressive strength tests. After demolding, the blocks were placed in a constant temperature and humidity curing chamber at 20±1℃ and relative humidity ≥95% for 28 days.

[0057] Check temperature and humidity daily. Record the maximum compressive pressure using a pressure testing machine (model: WAW-600) and take the average value of three test blocks.

[0058] Average compressive strength results refer to Figure 1 As shown;

[0059] Table 4 Experimental material ratio scheme (mass ratio)

[0060] Depend on Figure 1 It can be seen that, with a 28-day compressive strength ≥3MPa as the performance standard, mix ratio B meets the performance requirements under the condition of the lowest cement content as a percentage of cementitious materials. Therefore, the mass ratio of fly ash:cement:coal gangue = 2.5:1:2.5 will be used for subsequent experiments.

[0061] In this embodiment, the industrial water glass in the additive consists of 27.3% SiO2, 8.6% Na2O, and 64.1% H2O;

[0062] The mass ratio of industrial water glass and calcium oxide composite activator in the admixture is 1:1;

[0063] The mass ratio of sodium hydroxide and calcium oxide composite activator in the admixture is 1:1;

[0064] The mass ratio of sodium carbonate and calcium oxide composite activator in the admixture is 1:1.

[0065] Specifically, a control experiment was conducted, maintaining the same experimental conditions as the preliminary experiment. Under the mass ratio of mine water:cementing material + aggregate = 0.5:1 and fly ash:cement:coal gangue = 2.5:1:2.5, a blank control group without admixtures and an experimental group with water glass were set up. The compressive strength of the test blocks, the formation law of hydration products, and the solidification effect on Cl⁻ and SO₄²⁻ in mine water were compared between the two groups to clarify the influence of admixtures on the performance and ion solidification ability of the fly ash-cement-coal gangue cementitious system.

[0066] Test blocks were prepared and cured using the same methods as in the preliminary experiment. The admixture group had a water glass content of 4.8% (percentage of total material mass), with other conditions remaining unchanged. Twelve test blocks were prepared for each group. The following experiments were conducted: ① The compressive strength of each group of test blocks was measured at 3 days, 7 days, and 28 days; ② XRD testing was used to detect the formation of hydration products at 3 days, 7 days, and 28 days; ③ Immersion experiment: Test blocks and deionized water were placed in a glass jar sterilized at a mass ratio of 1:5 and kept in a constant temperature (20±1℃), constant humidity, and light-protected environment. After immersion for 7 days and 28 days, the supernatant was taken to determine the concentrations of Cl⁻ and SO₄²⁻, and the ion solidification rate was calculated (solidification rate = (1 - ion concentration of immersion solution × volume of immersion solution / initial total ion content in test block) × 100%). The experimental results are as follows: Figure 2-6 As shown;

[0067] The experimental data above show that the compressive strength of the admixture group specimens was significantly higher than that of the blank group specimens without admixtures. XRD image analysis revealed that at 28 days, the admixture group contained the curing product Aft of SO4²⁻, as well as Cl⁻. - The solidified product Friedel salt was detected in the control group, while no corresponding hydration products were detected in the blank group; immersion experiments showed that after 28 days, the blank group sample was less resistant to SO4²⁻ and Cl⁻. - The curing rates were 60.35% and 49.85%, respectively. The additive group test blocks showed good resistance to SO4²⁻ and Cl⁻. - The curing rates were 69.91% and 65.10%, respectively.

[0068] The addition of additives significantly improved the mechanical properties of the test block; at the same time, it achieved a dual solidification mechanism of physical sealing and chemical bonding. The dense hydration products reduced permeation and fixed the two ions in the form of insoluble substances, while the blank group relied only on physical encapsulation and a small amount of physical adsorption, and the long-term ions were easily re-dissolved.

[0069] In the admixture proportioning experiment, preliminary experiments determined the following mass ratios as the optimal mix design: mine water: cementitious material + aggregate = 0.5:1, and fly ash: cement: coal gangue = 2.5:1:2.5. Control group experiments confirmed that the addition of admixtures improved the mechanical properties and solidification ion capacity of the test blocks. Now, using the admixture dosage (percentage of total material mass) and type as variables, and keeping the experimental conditions constant, test blocks were prepared according to Table 3, with 9 blocks per group, for compressive strength testing and XRD testing. Based on the mold volume and material density, the required mass of each material for preparing each test block was calculated, as shown in Table 4. The proportions of each ratio to the total material mass were: ratio 1: 9.6%, ratio 2: 4.8%, and ratio 3: 2.4%.

[0070] Table 5 Admixture Proportioning Scheme

[0071] Table 6 Experimental Material Proportions

[0072] After demolding, the test blocks were placed in a constant temperature and humidity curing chamber at (20±1)℃ and relative humidity ≥95% for 28 days. Temperature and humidity were checked daily. Six groups of test blocks, with 12 blocks per group, were subjected to XRD and compressive strength tests at 3, 7, and 28 days. The formation of hydration products was also assessed. Hydration was terminated with ethanol before XRD testing. The maximum compressive pressure was recorded using a pressure testing machine (model: WAW-600), and the average value of three test blocks was taken.

[0073] Immersion precipitation test: Using the ratio with the highest compressive strength, ensuring the raw materials remain unchanged, prepare new test blocks. After curing until complete solidification, conduct an immersion test. Immerse the cured test blocks with deionized water at a mass ratio of 1:5 in a high-temperature sterilized glass jar. Take samples every 3, 7, and 28 days to determine the concentrations of Cl⁻ and SO₄²⁻. Provide a constant temperature, constant humidity, and light-protected environment during immersion. The cured and immersion test blocks are as follows... Figure 7 and Figure 8 As shown;

[0074] The statistical experimental results, including the maximum load pressure, are shown in Tables 7-9, and the average load pressure is shown in Tables 9-9. Figures 9-14 As shown;

[0075] Table 7 Maximum Load Pressure of Mix Ratio 1

[0076] Table 8 Maximum Load Pressure of Mix Ratio 2

[0077] Table 9 Maximum Load Pressure of Mix Ratio 3

[0078] The compressive strength test results of admixture a are as follows: Figure 9 As shown. The results indicate that at 7D, the internal reactions were uneven, and the intensity within each group varied significantly. The presence of excess Na in the 1a formulation was also significant. + This may have interfered with the stability of the hydration products, leading to a loose local structure in the early-formed gel; the 2a ratio exhibited the highest strength, with a suitable activator ensuring sufficient reaction of the active components (SiO2, Al2O3) while avoiding excessive Na. + Interference from the alkaline activator promotes the uniform formation of CSH gel and ettringite (AFt), resulting in a dense microstructure. Formula 3a exhibits the lowest strength; insufficient alkaline activator leads to a slow reaction, fewer hydration products, excessively high porosity, and low strength. At 28 days, the internal reaction is essentially complete; formula 1a shows the lowest strength, as an excessively rapid early reaction may result in microcracks and excessive Na. + The influence of the fly ash weakened the long-term strength, resulting in the strength of ratio 1a being lower than that of the other two groups. The strengths of ratios 2a and 3a were roughly equivalent. During the reaction process of ratio 2a, amorphous gel may have been generated, forming local closed pores and hindering the later hydration. Although ratio 3a had insufficient early alkali activation and fewer hydration products, the pozzolanic reaction of fly ash is long-term. In the continuous and slow process, the unreacted active components continued to react slowly, filling the pores and increasing the density. Finally, the strength gradually approached that of ratio 2a.

[0079] The compressive strength test results of admixture b are as follows: Figure 10 As shown in the figure. According to the proportion experiment a, proportion 1b (2b) is equivalent to adding 4.8% (2.4%) calcium oxide to proportion 2a (3a). The experimental results show that the strength of the specimen with added calcium oxide is significantly enhanced. Calcium oxide can provide Ca²⁺ to the system, promoting the formation of stronger CASH gel, rather than pure geopolymer NASH gel; at the same time, it reacts with water glass to form more complex gel products; and generates more OH. - This method can dissolve the active SiO2 and Al2O3 in fly ash more quickly, while the hydration releases heat, raising the system temperature and accelerating the early reaction. The early strength increased by 57% and 100%, respectively. Due to the low content of only 1.2% industrial water glass in formulation 3b, the fly ash dissolves slowly, the system temperature rises slowly, the initial activation strength is insufficient, but the later strength is improved, proving the long-term nature of the fly ash pozzolanic reaction.

[0080] The compressive strength test results of the product with additive c are as follows: Figure 11 As shown in the figure, compared with additive a, the two alkaline activators Na + With comparable content, sodium hydroxide is significantly more alkaline than water glass. While hydroxide ions can facilitate the separation of silicon and aluminum in fly ash, they cannot provide silicate ions, thus failing to directly participate as reactants in constructing the three-dimensional Si-O-Al network framework of geopolymers. Furthermore, its alkali-activated effect is considerably weaker than that of water glass. Within the same group, as the NaOH content decreased, the compressive strength of the test blocks gradually increased. The excessively alkaline environment of the 1c ratio and the large amount of heat released during sodium hydroxide hydration led to an excessively rapid dissolution rate of the silicon and aluminum raw materials. The large amount of dissolved ions in a short time did not have time to arrange themselves in an orderly manner and gel, rapidly generating a large number of amorphous products or early products with fine grains. Simultaneously, a large amount of Na... + Despite the competition for Cl⁻ adsorption sites, a large amount of free Cl⁻ and SO₄²⁻ remain in the test block, resulting in the lowest average strength of the early reaction 7D among all formulations, at only 0.1 MPa. Compared to 2c and 1c, formulation 3c, with its more moderate alkaline and low-sodium environment, achieved the highest average compressive strength.

[0081] The compressive strength test results of the product with additive d are as follows: Figure 12 As shown, the addition of CaO does not cause a sharp spike in pH like NaOH, but rather provides a relatively stable and continuous highly alkaline environment, which is conducive to the smooth and orderly progress of the reaction, forming a more uniform and dense microstructure. Compared with additive c, the compressive strength is significantly improved. The formation of ettringite is the most effective way to chemically solidify sulfate ions. The necessary conditions for the formation of ettringite are sufficient Ca²⁺, Al³⁺, and SO₄²⁻ as well as a highly alkaline environment. The addition of CaO not only enhances the compressive strength of the specimen but also improves the ability to solidify harmful ions.

[0082] The compressive strength test results of admixtures e and f are as follows: Figure 13 , Figure 14As shown, Na2CO3 is a mild alkaline activator, with an activation efficiency lower than that of strongly alkaline NaOH and water glass. Its reaction is slower and it introduces competitive carbonate ions. Sodium carbonate hydrolysis provides OH⁻, but its alkalinity is much weaker than that of NaOH or water glass. This results in a slower rate of dissolution of the silicon and aluminum phases in fly ash glass, leading to insufficient early hydration reactions, low gel product (CSH, CASH) formation, and extremely low early strength. CO3²⁻ competes with SO4²⁻ and Cl⁻ for anion sites in ettringite (AFt) or Friedel salt to form carbon-type ettringite (Ca6[Al(OH)6]2⋅CO3⋅26H2O) or calcium monocarbonate (Mc) with poor stability and low strength [see equations (10), (12)]. Even if sulfate ettringite is formed, CO3²⁻ can easily convert it into carbonaceous ettringite [see equation (11)], reducing the system's ability to chemically solidify SO4²⁻ and potentially weakening the structure. After adding CaO, the Ca²⁺ provided by CaO will preferentially combine with CO3²⁻ to form calcium carbonate (CaCO3). This process effectively consumes the free CO3²⁻ in the system, greatly reducing its interference with the main reaction of aluminosilicates and the solidification reaction of sulfates. The generated CaCO3 microcrystals can fill the pores as micro-aggregates, making the structure more compact and contributing to the later strength development. Overall, among all additives, e and f have the best performance in the middle and lower range. Their strength is far better than the worst pure NaOH system (c, d), but significantly weaker than the best water glass + CaO system (a, b).

[0083] In summary, test blocks were re-prepared using the 1b and 2b ratios, which showed the best average compressive strength, and immersed in the solution for testing. Simultaneously, test blocks were prepared and immersed in the 2a and 3a ratios (equivalent to 1b and 2b without CaO, respectively) for comparison. The immersion test results are shown in Table 7, and the average ionic mass is as follows: Figures 8-9 As shown. Ion mass is expressed as the ion mass (m) of the mine water used in a single test block. 离子 =V 矿井水（单个试块） ×C 离子 ).

[0084] Table 10 Immersion Experiment Data

[0085] Depend on Figure 15 , 16 As can be seen from the data in Table 10, during 7D immersion, Cl - Both the concentration of SO4²⁻ and the concentration of Cl⁻ decreased significantly. After immersion for 7 days, the effects of various proportions of the cementitious materials on Cl⁻ were observed. - The curing rate is 45%~55%, and the curing rate for SO4²⁻ is 64%~83%; after immersion for 28 days, the curing rate of each proportion of the cementitious material for Cl- The curing rate ranges from 56% to 73%, and for SO4²⁻, it ranges from 64% to 87%. [Cure rate = m(cured mass of a single specimen) / m(total mass of salt ions in a single specimen)]

[0086] Based on the analysis of mechanism and curing rate, tricalcium aluminate (C3A) in the alkali-activated material preferentially reacts with SO4²⁻ to form ettringite (AFt), rapidly consuming a large amount of aluminum and calcium sources. Reaction (3) occurs, and high concentrations of SO4²⁻ (3918 mg / L) accelerate this reaction. Within 7 days, the amount of AFt generated approaches saturation, while being limited by chemical dynamic equilibrium and physical adsorption: AFt is stable at pH > 11.5, with a solubility of less than 0.02 g / L. The addition of calcium oxide can lower the pH of the system, maintain the stability of the cured product, and simultaneously facilitate the reaction of Ca. 2+ +2HCO3 - →CaCO3 + CO2 + H2O, reduces negative charge and enhances the reaction with SO4²⁻ and Cl⁻. - Electrostatic adsorption; the early-formed AFt and CSH gel fill the pores, hindering the migration of the remaining SO4²⁻. This results in the SO4²⁻ concentration remaining essentially unchanged in the later stages. The remaining gelling material after reacting with SO4²⁻ continues to react with Cl⁻. - The reaction produces Friedel salt, and reaction (6) occurs; because SO4²⁻ preferentially consumes the aluminum source (fly ash Al2O3=31.7%), the initial Cl... - The fixation process is slow, and the addition of water glass introduces a large amount of Na. + Na + Will and Cl - Competition for adsorption sites resulted in a low curing rate. Adding calcium oxide improved the yield of Friedel salt. The final product formed was an Aft-based framework, a CSH-based matrix, and Friedel salt filling the pores.

[0087] In the test block with additive a, SO4²⁻ and Cl⁻ reacted to 28D. - The solidification, i.e., reaction amounts, were 1149.62 mg and 37.10 mg, respectively. Correspondingly, the amounts of aluminum compounds consumed were 407.15 mg and 99.3 mg, respectively, which were less than 1% of the provided amount of aluminum compounds. This shows that although a certain amount of ions were solidified by using a single chemical activation, the utilization rate of aluminum compounds was extremely low. This indicates that fly ash is difficult to activate to a highly active state, thus making it impossible to achieve a higher ion solidification rate.

[0088] The preparation method of high-strength concrete material based on alkali-activated cementitious materials includes the following steps:

[0089] S1. Material pretreatment: After crushing, coal gangue and fly ash are screened to a particle size ≤5mm, dried at 105℃ for 24h, and stored in a sealed container; The mass ratio of fly ash, cement, and coal gangue is optimized by controlling variables to achieve a ratio of fly ash, reference cement, and coal gangue of 2.5:1:2.5.

[0090] S2. Pour fly ash, cement, and coal gangue into a cement paste mixer in proportion and dry mix until uniform; adjust the admixture to a pH close to that of the mixing water, slowly add the mixing water and admixture, select automatic mixing, form a uniform paste, and ensure that the ratio of mixing water to cementitious materials and aggregates is 0.5:1.

[0091] S3. Pour the slurry into the mold, let it stand for 24 hours, and then demold.

[0092] S4. Place the concrete material in a constant temperature and humidity curing chamber at a temperature of (20±1)℃ and a relative humidity of ≥95% for 28 days.

[0093] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A high-strength concrete material based on alkali-activated cementitious materials, characterized in that: High-strength concrete is made from mixing water, cementitious materials, aggregates, and admixtures, wherein the cementitious materials consist of fly ash and reference cement. The mixing water is mine water; The aggregate used is coal gangue; The additive is any one of the following: industrial water glass, industrial water glass and calcium oxide composite activator, sodium hydroxide, sodium hydroxide and calcium oxide composite activator, sodium carbonate, sodium carbonate and calcium oxide composite activator; The mass proportions of each component in the high-strength concrete material are as follows: fly ash 30%~40%, reference cement 10%~18%, coal gangue 30%~40%, admixtures 4%~12%, and mine water accounting for 0.4~0.6% of the total mass of the cementitious material.

2. The high-strength concrete material based on alkali-activated cementitious materials according to claim 1, characterized in that: The mixing ratio of water to cementitious materials and aggregates is 0.5:

1.

3. The high-strength concrete material based on alkali-activated cementitious materials according to claim 1, characterized in that: The fly ash and coal gangue are pre-treated, crushed, and then screened to a particle size of ≤5mm; The ratio of fly ash, reference cement and coal gangue is 2.5:1:2.

5.

4. The high-strength concrete material based on alkali-activated cementitious materials according to claim 1, characterized in that: The industrial water glass in the additive consists of 27.3% SiO2, 8.6% Na2O, and 64.1% H2O; The mass ratio of industrial water glass and calcium oxide composite activator in the admixture is 1:1; The mass ratio of sodium hydroxide and calcium oxide composite activator in the admixture is 1:1; The mass ratio of sodium carbonate and calcium oxide composite activator in the admixture is 1:

1.

5. A method for preparing high-strength concrete materials based on alkali-activated cementitious materials, characterized in that, It includes the following steps: S1. Material pretreatment: After crushing, coal gangue and fly ash are screened to a particle size ≤5mm, dried at 105℃ for 24h, and stored in a sealed container. The mass ratio of fly ash, cement, and coal gangue was optimized by controlling the variable method, so that the ratio of fly ash, reference cement, and coal gangue was 2.5:1:2.

5. S2. Pour fly ash, cement, and coal gangue into a cement paste mixer in proportion and dry mix until uniform; adjust the admixture to a pH close to that of the mixing water, slowly add the mixing water and admixture, select automatic mixing, form a uniform paste, and ensure that the ratio of mixing water to cementitious materials and aggregates is 0.5:

1. S3. Pour the slurry into the mold, let it stand for 24 hours, and then demold. S4. Place the concrete material in a constant temperature and humidity curing chamber at a temperature of 20±1℃ and a relative humidity of ≥95% for 28 days.

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