Modified granite weathered material for highway subbase and preparation method thereof

Abstract

The present invention relates to the field of roadbed filler technology, and more particularly to a modified weathered granite material for highway subbases and a preparation method thereof. The material comprises the following raw materials, by mass percentage: 78-85% weathered granite material, 4-6% ordinary Portland cement, 8-12% fly ash, 0.5-1% composite curing agent, 2-3% composite modifier, and the balance being water. By incorporating the weathered granite material and fly ash, the present invention achieves efficient utilization of industrial solid waste, conforming to the concept of green and low-carbon engineering construction, improving the mechanical properties, water resistance, and freeze-thaw resistance of the weathered granite material, and meeting the requirements of highway subbases for high load-bearing capacity, low deformation, and long service life.

Description

Technical Field

[0001] The invention relates to the technical field of roadbed fillers, in particular to a modified weathered granite material for a highway subbase and a preparation method thereof. Background Art

[0002] Weathered granite is a secondary, loose accumulation of granite parent rock formed by long-term geological processes. In highway engineering, this material has long been used for low-grade roadbed fill due to its local availability and low cost. In terms of its mineral composition, weathered granite is primarily composed of quartz, feldspar, and secondary clay minerals (such as montmorillonite and illite). Clay minerals, due to their layered structure and cation exchange capacity, are key factors influencing the engineering performance of weathered granite. Montmorillonite has an extremely high lattice expansion, allowing it to absorb large quantities of water molecules between its layers when exposed to water, resulting in a volume expansion rate of several times. While illite has a relatively low expansion, its lamellar structure is susceptible to slip under shear stress, significantly reducing interparticle cohesion. This results in unmodified weathered granite exhibiting a naturally high porosity, low density, and loose structure, with predominantly point-to-point contact between particles and weak cohesion.

[0003] Patent publication number CN114717884A discloses a fully weathered granite sedimentary soil roadbed and its construction method. This method utilizes a combination of weathered granite soil and recycled construction waste. After the weathered soil is spread and compacted, the base layer is then covered with crushed construction waste to form a transition layer. A graded filler mixed with a curing agent is then mixed and spread in layers, compacted using a combination of static pressure and vibration. The resulting granite sedimentary soil roadbed not only solidifies quickly but also fully utilizes the recycling of construction waste.

[0004] However, due to the high clay mineral content in weathered materials, they easily swell and soften when exposed to water, and shrink and crack under dry conditions. As a result, their mechanical strength, water stability, and deformation resistance are insufficient to meet the load-bearing requirements of high-grade highway subbases. Furthermore, the particle size distribution of unmodified weathered materials is highly discrete, making them prone to localized loosening or excessive crushing during compaction, further restricting their large-scale application in highway structural layers. Summary of the Invention

[0005] In order to solve the problems mentioned in the above background technology, the present invention provides a modified weathered granite material for highway subbase and a preparation method thereof.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A modified weathered granite material for highway subbase comprises the following raw materials by mass percentage: 78-85% weathered granite material, 4-6% ordinary Portland cement, 8-12% fly ash, 0.5-1% composite curing agent, 2-3% composite modifier, and the balance is water.

[0008] Furthermore, the fly ash adopts secondary fly ash or tertiary fly ash.

[0009] Furthermore, the composite curing agent includes the following raw materials by mass percentage: 48-57% lime, 15-17% sodium sulfate, 20-23% water glass and 8-12% acrylate powder.

[0010] Furthermore, the composite modifier comprises the following steps to prepare:

[0011] S1. Add silane coupling agent to anhydrous ethanol, stir until completely transparent, and adjust the pH value to 4.5-5.5 to obtain a silane solution;

[0012] S2. Sodium lauryl sulfate is added to deionized water and stirred until a uniform micelle system is formed to obtain a micelle solution, which is transferred to a reactor for standby use. Vinyl carbazole is added to anhydrous ethanol and ultrasonically treated for 10-15 minutes to obtain a vinyl carbazole solution. The vinyl carbazole solution is slowly injected into the micelle solution. Part of ammonium persulfate and tetramethylethylenediamine are first added, stirred for 10-20 minutes, and then nitrogen is introduced for deoxygenation for 30-40 minutes. The remaining ammonium persulfate and silane solution are added, and a constant temperature water bath is placed. The reaction is stirred for 4-6 hours, washed, and dried to obtain a composite modifier.

[0013] Furthermore, in step S1, the mass ratio of the silane coupling agent to anhydrous ethanol is (1-1.2): (200-210).

[0014] Furthermore, the silane coupling agent in step S1 includes one of KH-550, KH-560, KH-570, KH-792 and KH-590.

[0015] Furthermore, in step S2, the mass ratio of sodium lauryl sulfate and deionized water is (1-1.5): (23-25), the mass ratio of vinyl carbazole and anhydrous ethanol is (1-1.1): (5.8-6), and the mass ratio of vinyl carbazole solution, micellar solution, ammonium persulfate, tetramethylethylenediamine and silane solution is (72-74): (200-210): (1-1.1): (0.2-0.4): 300, wherein the amount of ammonium persulfate added for the first time is 30-40wt%, and the amount of ammonium persulfate added for the second time is 60-70wt%.

[0016] Furthermore, in step S2, the frequency of the ultrasonic treatment is 40-50 kHz, the power is 100-200 W, the temperature during the ultrasonic treatment is 50-55° C., the temperature of the constant temperature water bath is 38-42° C., and the stirring speed is 100-200 rpm.

[0017] According to another aspect of the present invention, there is provided a method for preparing the modified weathered granite material for the highway subbase, comprising the following steps:

[0018] Ordinary Portland cement and fly ash are mixed in a dry state in proportion for 1-2 minutes to obtain a premix. The premix, composite curing agent and composite modifier are added to the granite weathered material in sequence and stirred for 2-3 minutes. Water is added and wet-mixed for 5-6 minutes until the mixture becomes homogeneous granular, thereby obtaining a modified granite weathered material for highway subbase.

[0019] Beneficial effects of the present invention:

[0020] 1. In the technical solution of the present invention, during the preparation process, the silane coupling agent hydrolyzes under acidic conditions to form active silanol groups, which undergo condensation reactions with hydroxyl groups on the surface of the weathered granite material to build a stable covalent bond network. At the same time, the vinyl carbazole polymer side chains are embedded in the pores of the cement hydration product through nanoscale mechanical interlocking, reducing the insufficient strength of traditional materials caused by weak interfacial bonding, enabling the base material to withstand higher loads and reducing structural damage during long-term service.

[0021] 2. In this technical solution, the rigid backbone of vinyl carbazole forms a three-dimensional network through π-π stacking, forcing crack paths to deflect when subjected to stress. The chemical bonds in the silane crosslinking layer preferentially break and reform in areas of stress concentration, slowing crack propagation through energy dissipation. This approach is particularly suitable for base structures subjected to frequent traffic loads, significantly reducing the risk of fatigue damage accumulation.

[0022] 3. In this technical solution, the chemical bonding between the silane layer and calcium ions forms a dense, waterproof structure, blocking water penetration pathways. The hydrophobic carbazole rings in the polymer core further reduce capillary water absorption. Furthermore, residual surfactant components induce the formation of nanoscale gelled products, filling microscopic pores. This reduces the durability degradation of traditional materials caused by freeze-thaw cycles and salt corrosion, extending the service life of the base layer in harsh environments such as damp and cold.

[0023] 4. In the technical solution of the present invention, the hydrogen bonding between the outer silanol groups and the cement paste accelerates the hydration reaction and shortens the setting time; the surfactant molecules are adsorbed on the surface of the fly ash particles and prevent agglomeration through electrostatic repulsion, so that the components can quickly form a homogeneous aggregate structure during the mixing process, solving the problems of construction segregation and insufficient compaction caused by uneven dispersion of components in traditional modified materials, and is particularly suitable for large-scale mechanized paving operations. DETAILED DESCRIPTION

[0024] The following will clearly and completely describe the technical solutions of the present invention in conjunction with the embodiments of the present invention. Obviously, the embodiments described are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts shall fall within the scope of protection of the present invention.

[0025] Unless otherwise specified, the raw materials used in the present invention are all conventional products purchased from the market.

[0026] Preparation Example 1

[0027] The composite modifier is prepared by the following steps:

[0028] S1. Add 10 g of KH-570 to 2000 g of anhydrous ethanol, stir at 200 rpm until completely transparent, and add glacial acetic acid to adjust the pH to 4.5 to obtain a silane solution;

[0029] S2. 10g of sodium lauryl sulfate was added to 230g of deionized water and stirred at a speed of 100rpm to form a uniform micellar system to obtain a micellar solution, which was transferred to a reactor for standby use. 10g of vinyl carbazole was added to 58g of anhydrous ethanol preheated to 50°C and ultrasonically treated at 50°C for 10min. The frequency of the ultrasonic treatment was 40kHz and the power was 100W to obtain a vinyl carbazole solution. 72g of vinyl carbazole solution was slowly injected into 200g of micellar solution. 0.3g of ammonium persulfate and 0.2g of tetramethylethylenediamine were first added. After stirring for 10min, nitrogen was introduced for deoxygenation for 30min at a flow rate of 0.5L / min. 0.7g of ammonium persulfate was added, and 300g of silane solution was added. The mixture was heated in a constant temperature water bath at 38°C and stirred at a speed of 100rpm for 4h. After the reaction was completed, the mixture was immediately cooled to 5°C with an ice-water bath, washed 3 times with deionized water, and dried to constant weight at 60°C to obtain a composite modifier.

[0030] Preparation Example 2

[0031] The composite modifier is prepared by the following steps:

[0032] S1. Add 10.5 g of KH-550 to 2050 g of anhydrous ethanol, stir at 250 rpm until completely transparent, and add glacial acetic acid to adjust the pH to 5 to obtain a silane solution;

[0033] S2, 12.5g sodium lauryl sulfate was added to 240g deionized water, and stirred at a speed of 150rpm to form a uniform micellar system to obtain a micellar solution, which was transferred to a reactor for standby use, 10.5g vinyl carbazole was added to 59g anhydrous ethanol preheated to 50°C, and ultrasonicated at 52°C for 12min. The frequency of the ultrasonication was 45kHz and the power was 150W to obtain a vinyl carbazole solution. 73g vinyl carbazole solution was slowly injected into 205g micellar solution, 0.32g ammonium persulfate and 0.3g tetramethylethylenediamine were first added, and after stirring for 15min, nitrogen was introduced for deoxygenation for 35min at a flow rate of 0.5L / min, 0.68g ammonium persulfate was added, 300g silane solution was added, and a constant temperature water bath was placed at 40°C, and the reaction was stirred at a speed of 150rpm for 5h. After the reaction was completed, the temperature was immediately lowered to 5°C with an ice water bath, washed 3 times with deionized water, and dried to constant weight at 60°C to obtain a composite modifier.

[0034] Preparation Example 3

[0035] The composite modifier is prepared by the following steps:

[0036] S1. Add 11 g of KH-560 to 2100 g of anhydrous ethanol, stir at 300 rpm until completely transparent, and add glacial acetic acid to adjust the pH to 5.5 to obtain a silane solution;

[0037] S2, 15g sodium lauryl sulfate was added to 250g deionized water, and stirred at a speed of 200rpm to form a uniform micellar system to obtain a micellar solution, which was transferred to a reactor for standby use, 11g vinyl carbazole was added to 60g anhydrous ethanol preheated to 50°C, and ultrasonicated at 55°C for 15min. The frequency of the ultrasonication was 50kHz and the power was 200W to obtain a vinyl carbazole solution. 74g vinyl carbazole solution was slowly injected into 210g micellar solution, 0.44g ammonium persulfate and 0.4g tetramethylethylenediamine were first added, and after stirring for 20min, nitrogen was introduced for deoxygenation for 40min at a flow rate of 0.5L / min, 0.66g ammonium persulfate was added, 300g silane solution was added, and a constant temperature water bath was placed at 42°C, and the reaction was stirred at a speed of 200rpm for 4-6h. After the reaction was completed, the temperature was immediately lowered to below 10°C with an ice-water bath, washed 3 times with deionized water, and dried to constant weight at 60°C to obtain a composite modifier.

[0038] Example 1

[0039] A method for preparing modified weathered granite material for highway subbase comprises the following steps:

[0040] 6% ordinary Portland cement and 12% secondary fly ash were mixed in a dry state for 3 minutes in proportion to obtain a premix. The premix, 3% of the composite modifier prepared in Preparation Example 1, and 1% of a composite curing agent were added in sequence to 78% of the weathered granite material. The composite curing agent included 57% of lime, 15% of sodium sulfate, 20% of water glass, and 8% of acrylic ester powder. The mixture was dry-mixed for 2 minutes, supplemented with water, and wet-mixed for 5 minutes until the mixture was in a homogeneous granular state, thereby obtaining a modified weathered granite material for a highway subbase.

[0041] Example 2

[0042] A method for preparing modified weathered granite material for highway subbase comprises the following steps:

[0043] 5% ordinary Portland cement and 10% secondary fly ash were mixed in a dry state for 4 minutes in proportion to obtain a premix. The premix, 2.5% of the composite modifier prepared in Preparation Example 2, and 0.5% of a composite curing agent were added in sequence to 82% of the weathered granite material. The composite curing agent included 52% of lime, 16% of sodium sulfate, 22% of water glass, and 10% of acrylic ester powder. The mixture was dry-mixed for 2.5 minutes, supplemented with water, and wet-mixed for 5.5 minutes until the mixture was in a homogeneous granular state, thereby obtaining a modified weathered granite material for a highway subbase.

[0044] Example 3

[0045] A method for preparing modified weathered granite material for highway subbase comprises the following steps:

[0046] 4% ordinary Portland cement and 8% grade tertiary fly ash were mixed in a dry state for 5 minutes in proportion to obtain a premix. The premix, 2% of the composite modifier prepared in Preparation Example 3, and 1% of a composite curing agent were added in sequence to 85% of the weathered granite material. The composite curing agent included 48% of lime, 17% of sodium sulfate, 23% of water glass, and 12% of acrylic ester powder. The mixture was dry-mixed for 3 minutes, supplemented with water, and wet-mixed for 6 minutes until the mixture was in a homogeneous granular state, thereby obtaining a modified weathered granite material for a highway subbase.

[0047] Comparative Example 1

[0048] The difference between this comparative example and Preparation Example 1 is that no silane coupling agent is added, and the remaining steps are the same as Preparation Example 1.

[0049] Comparative Example 2

[0050] The difference between this comparative example and Preparation Example 2 is that sodium lauryl sulfate is not added, and the remaining steps are the same as those in Preparation Example 2.

[0051] Comparative Example 3

[0052] The difference between this comparative example and Preparation Example 3 is that vinyl carbazole is not added, and the remaining steps are the same as those in Preparation Example 3.

[0053] Comparative Example 4

[0054] The difference between this comparative example and Example 1 is that the composite modifier prepared in Comparative Example 1 is used, and the remaining steps are the same as those in Example 1.

[0055] Comparative Example 5

[0056] The difference between this comparative example and Example 2 is that the composite modifier prepared in Comparative Example 2 is used, and the remaining steps are the same as those in Example 2.

[0057] Comparative Example 6

[0058] The difference between this comparative example and Example 3 is that the composite modifier prepared in Comparative Example 3 is used, and the remaining steps are the same as those in Example 3.

[0059] Comparative Example 7

[0060] The difference between this comparative example and Example 1 is that no composite modifier is added, and the remaining steps are the same as those in Example 1.

[0061] With reference to JTG E51-2009, "Test Procedure for Stabilized Inorganic Binders for Highway Engineering," and GB / T 50082-2024, "Standard for Test Methods for Long-Term Performance and Durability of Concrete," six φ150×150 mm cylindrical specimens, each cured for 28 days, were prepared for Examples 1-3 and Comparative Examples 4-7. The specimens were immersed in 20±2°C water for 24 hours until saturated, with the water level 20 mm above the specimen. The specimens were removed, their surface moisture wiped with a damp cloth, and their initial mass (m0) was measured. All specimens were placed upright in a freezer set to -18±2°C for 4 hours. After holding for 4 hours, they were quickly transferred to a 20±2°C thawing water tank within 5 minutes. The specimens were completely immersed in water for 4 hours, with each cycle considered one. After 10 cycles, the sample was placed in a 105°C oven and dried to constant weight. The final mass (m1) was weighed and the mass loss rate (%) was calculated. The mass loss rate = (m0-m1) / m0×100%. The results are shown in Table 1:

[0062] Table 1. Freeze-thaw cycle test results of Examples 1-3 and Comparative Examples 4-7

[0063]

[0064] The mixtures prepared in Examples 1-3 and 4-7 were loaded into the test mold in three layers. Each layer was vibrated for 60 seconds using a vibratory compactor. After forming, the mixtures were allowed to stand for 24 hours, demolded, and placed in a standard curing room (temperature 20±2°C, relative humidity ≥95%) for 28 days. Six Φ50mm×50mm cylindrical specimens prepared and cured for 28 days were prepared for Examples 1-3 and Comparative Examples 4-7, respectively. Unconfined compressive strength tests were performed at a loading rate of 1mm / min and a test temperature of 20±2°C. The peak load (kN) was recorded and the UCS was calculated. 干 (MPa), UCS=peak load / (specimen cross-sectional area×1000), the specimen cross-sectional area is calculated based on a diameter of 50mm. Prepare the specimen in the same way and immerse it completely in a constant temperature water bath at 20±2℃ for 48 hours. After immersion, remove the specimen, wipe off the surface moisture with a wet cloth, and immediately conduct a strength test to test the UCS after immersion. 湿 , calculate the strength loss rate, strength loss rate = loss rate (%) = (UCS 干 -UCS 湿 ) / UCS 干 ×100%. The results are shown in Table 2:

[0065] Table 2. Unconfined compressive strength results of Examples 1-3 and Comparative Examples 4-7

[0066]

[0067] As shown in Table 1, the mass loss rates of Examples 1-3 are relatively low, at 0.9±0.2%, 1.2±0.3%, and 1.3±0.4%, respectively, indicating good freeze-thaw resistance. The mass loss rates of Comparative Examples 4-7 are significantly higher than those of the Examples, with Comparative Example 7 having the highest mass loss rate of 6.7±0.9%. The mass loss rates of Comparative Examples 4-6 range from 3.2±0.5% to 4.5±0.6%, indicating that the composite modifier plays an important role in improving the freeze-thaw resistance of the material, and that the silane coupling agent, sodium lauryl sulfate, and vinyl carbazole play a synergistic role in the composite modifier, jointly improving the freeze-thaw resistance of the material.

[0068] As shown in Table 2, the UCS dry (unconfined compressive strength) of Examples 1-3 is relatively high, at 6.8±0.4 MPa, 7.1±0.3 MPa, and 6.5±0.5 MPa, respectively, and the strength loss rate after immersion in water is relatively low, at 8.8%, 8.5%, and 9.2%, respectively, indicating that they have good mechanical properties and water resistance. The UCS dry of Comparative Examples 4-7 is significantly lower than that of the Examples. Comparative Example 7 has the lowest UCS dry, at 2.9±0.1 MPa, and the highest strength loss rate, at 34.5%. The UCS dry of Comparative Examples 4-6 is 3.5±0.3 MPa, 4.0±0.2 MPa, and 3.8±0.4 MPa, respectively, and the strength loss rate is 25.7%, 27.5%, 28.9%, and 34.5%, respectively, indicating that the composite modifier has a significant effect on improving the mechanical properties and water resistance of the material.

[0069] The silane coupling agent acts as a bridge within the composite modifier. The siloxane groups in its molecular structure may chemically bond with the surface of the weathered granite material, while the vinyl groups may react with vinyl carbazole, strengthening interfacial bonding and reducing material damage caused by water migration and ice crystal expansion during freeze-thaw cycles, thereby reducing mass loss. Sodium dodecyl sulfate, acting as a surfactant, forms a uniform micellar system within the micellar solution, providing a favorable microenvironment for the polymerization of vinyl carbazole and promoting its uniform dispersion and polymerization within the micelles. The resulting polymer cross-links with the silane solution, enhancing the overall performance of the composite modifier and improving its freeze-thaw resistance. Vinyl carbazole introduces a unique chemical structure and properties to the composite modifier. The resulting polymer fills the material's internal pores, increasing its density and reducing water penetration channels. This reduces damage caused by water freezing and expansion during freeze-thaw cycles, thereby improving its freeze-thaw resistance. Furthermore, the addition of vinyl carbazole enhances the composite modifier's compatibility with other materials and improves its unconfined compressive strength.

[0070] The omission of silane coupling agent, sodium lauryl sulfate, or vinyl carbazole in Comparative Examples 1-3 resulted in a decrease in the performance of the composite modifier. Consequently, the resulting materials exhibited a significant increase in mass loss, decreased unconfined compressive strength, and increased strength loss during freeze-thaw cycling. In the absence of these key components, the composite modifier failed to exert its synergistic effects, impacting the overall performance of the material. Comparative Example 7 exhibited the highest mass loss, the lowest unconfined compressive strength, and the highest strength loss, demonstrating that the composite modifier played a key role in improving the material's performance. Its components collaborated to enhance both the material's freeze-thaw resistance and mechanical properties.

[0071] In summary, the freeze-thaw resistance and mechanical properties of modified granite weathered material for highway subbase were significantly improved through the synergistic effect of the silane coupling agent, sodium dodecyl sulfate and vinyl carbazole in the composite modifier.

[0072] Throughout the specification, reference to terms such as "Preparation," "Example," or "Examples" indicates that the specific features, structures, materials, or characteristics described in conjunction with that embodiment or preparation are included in at least one embodiment or preparation of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or preparation. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or preparations.

[0073] The above description is only a preferred specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any technician familiar with the technical field, within the technical scope disclosed by the present invention, who makes equivalent replacements or changes based on the technical solution and inventive concept of the present invention, should be covered by the scope of protection of the present invention.

Claims

1. A modified weathered granite material for highway subbase, characterized in that: The following raw materials are included by mass percentage: Weathered granite material 78-85%, ordinary Portland cement 4-6%, fly ash 8-12%, composite curing agent 0.5-1%, composite modifier 2-3%, and the balance is water; Wherein, the composite modifier comprises the following steps to be prepared: S1. Add silane coupling agent to anhydrous ethanol, stir until completely transparent, and adjust the pH value to 4.5-5.5 to obtain a silane solution; S2. Sodium lauryl sulfate is added to deionized water and stirred until a uniform micelle system is formed to obtain a micelle solution, which is transferred to a reactor for standby use. Vinyl carbazole is added to anhydrous ethanol and ultrasonically treated for 10-15 minutes to obtain a vinyl carbazole solution. The vinyl carbazole solution is injected into the micelle solution, and part of ammonium persulfate and tetramethylethylenediamine are added first. After stirring for 10-20 minutes, nitrogen is introduced for deoxygenation for 30-40 minutes. The remaining ammonium persulfate and silane solution are then added, and the mixture is placed in a constant temperature water bath and stirred for 4-6 hours. The mixture is washed and dried to obtain a composite modifier.

2. The modified weathered granite material for highway subbase according to claim 1, characterized in that: The composite curing agent comprises the following raw materials by mass percentage: 48-57% of lime, 15-17% of sodium sulfate, 20-23% of water glass and 8-12% of acrylate powder.

3. The modified weathered granite material for highway subbase according to claim 1, characterized in that: The mass ratio of the silane coupling agent to anhydrous ethanol in step S1 is (1-1.2): (200-210).

4. The modified weathered granite material for highway subbase according to claim 1, characterized in that: The silane coupling agent in step S1 includes one of KH-550, KH-560, KH-570, KH-792 and KH-590.

5. The modified weathered granite material for highway subbase according to claim 1, characterized in that: In step S2, the mass ratio of sodium lauryl sulfate and deionized water is (1-1.5): (23-25), the mass ratio of vinyl carbazole and anhydrous ethanol is (1-1.1): (5.8-6), and the mass ratio of vinyl carbazole solution, micellar solution, ammonium persulfate, tetramethylethylenediamine and silane solution is (72-74): (200-210): (1-1.1): (0.2-0.4): 300, wherein the amount of ammonium persulfate added for the first time is 30-40wt%, and the amount of ammonium persulfate added for the second time is 60-70wt%.

6. The modified weathered granite material for highway subbase according to claim 1, characterized in that: The frequency of the ultrasonic treatment in step S2 is 40-50 kHz, the power is 100-200 W, the temperature during the ultrasonic treatment is 50-55° C., the temperature of the constant temperature water bath is 38-42° C., and the stirring speed is 100-200 rpm.

7. A method for preparing the modified weathered granite material for highway subbase according to any one of claims 1 to 6, characterized in that: The following steps are involved: Ordinary Portland cement and fly ash are mixed in a dry state in proportion for 1-2 minutes to obtain a premix. The premix, composite curing agent and composite modifier are added to the granite weathered material in sequence and stirred for 2-3 minutes. Water is added and wet-mixed for 5-6 minutes until the mixture becomes homogeneous granular, thereby obtaining a modified granite weathered material for highway subbase.

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