Green low-carbon cementing material for roadbed and preparation method of green low-carbon cementing material

Abstract

The invention discloses a green low-carbon cementing material for a roadbed and a preparation method of the green low-carbon cementing material, and belongs to the technical field of low-carbon cementing materials, and the green low-carbon cementing material comprises the following components in parts by weight: 40-50 parts of superfine slag powder, 25-35 parts of self-made functionalized fly ash, 15-25 parts of steel slag powder, 8-15 parts of desulfurized gypsum and 2-4 parts of modified basalt fiber. According to the self-made functional fly ash in the cementing material, the surface inertia of the fly ash is broken through alkali activation, and a large amount of solid waste is applied to the roadbed material which is also widely applied, so that the environmental problem caused by accumulation of the solid waste can be solved, the solid waste is utilized, and the utilization rate of the solid waste is improved. The method also conforms to the green, cyclic and sustainable strategic development direction, and has huge market potential.

Description

Technical Field

[0001] The present invention belongs to the technical field of low-carbon cementitious materials, and specifically relates to a green low-carbon cementitious material for roadbed and a preparation method thereof. Background Art

[0002] Traditional road concrete often uses Portland cement as the primary binder. The large amounts of Portland cement used not only increase road concrete production costs but also result in significant carbon emissions, hindering the green and sustainable development of the building materials industry. Furthermore, the accumulation of various industrial solid wastes poses significant environmental challenges. Currently, attempts are underway to partially or completely replace raw materials for road base materials, such as natural soil and stone and cementitious materials, with industrial solid waste, offering an effective means of large-scale solid waste management.

[0003] Prior art includes a Chinese invention patent with application number CN202510000303.1, which discloses a low-carbon cementitious material for preparing a highway roadbed and a preparation method thereof, comprising the following steps: Step S1: weighing 100-120 parts of mineral powder, by weight, adding them to 450-500 parts of anhydrous ethanol, and ultrasonically dispersing them for 1-2 hours to obtain a suspension; adding 20-25 parts of DL-alanine to the suspension, heating it to 75-80°C and stirring it for 0.5-1 hour, filtering it, washing it, and drying it to obtain an amination mineral powder; Step S2: adding 40-70 parts of amination mineral powder, 10-30 parts of fly ash, and 5-20 parts of gypsum, by weight, to 100-140 parts of deionized water for a first stirring treatment, and then adding 2-15 parts of red mud for a second stirring treatment to obtain a low-carbon cementitious material for preparing a highway roadbed.

[0004] The aforementioned existing technologies utilize a significant amount of solid waste, which aligns with green, circular, and sustainable strategic development. They also demonstrate excellent compressive and flexural strength in basic mechanical performance evaluations, and are adequate for highway roadbed applications. However, when applied to more complex roadbeds, the durability and impact resistance of these technologies still have significant room for improvement. Furthermore, as roadbed materials, superior freeze-thaw resistance and impact resistance can also extend their useful life.

[0005] Therefore, in order to fill the technical gap in the market, the present application provides a green and low-carbon cementitious material for roadbed and a preparation method thereof to solve the above technical problems. Summary of the Invention

[0006] In order to solve the defects existing in the above technical solutions, the purpose of the present invention is to provide a green and low-carbon cementitious material for roadbed and a preparation method thereof; the purpose of the present invention can be achieved by the following technical solution: A green and low-carbon cementitious material for roadbed, calculated by weight, is composed as follows: 40-50 parts of slag powder, 25-35 parts of homemade functionalized fly ash, 15-25 parts of steel slag powder, 8-15 parts of desulfurized gypsum, and 2-4 parts of modified basalt fiber.

[0007] The slag powder is S95 grade granulated blast furnace slag powder; The steel slag powder is a powder obtained by grinding steel slag in a ball mill, and the specific surface area of ​​the steel slag powder is 450 to 650 m 2 / kg, alkalinity greater than 1.8; The specific surface area of ​​the desulfurized gypsum is ≥450m 2 / kg; The P2O5 content of the desulfurized gypsum is 0.6-0.8wt%; The desulfurization gypsum meets the requirements of GB / T23456-2009 standard.

[0008] The modified basalt fiber preparation method comprises the following steps: taking basalt fiber and placing it in a reaction container; adding a sodium hydroxide aqueous solution to completely immerse the fiber; stirring at a low speed, heating to 80° C., and reacting at a constant temperature for 2 hours; stopping heating after the reaction is completed, draining the alkali solution, and repeatedly rinsing the fiber with deionized water until the pH value of the washed water reaches 7.0±0.2; air-drying the washed fiber to obtain surface-activated dry basalt fiber; taking the dried activated basalt fiber and immersing it in a sodium alginate aqueous solution; stirring at a low speed at room temperature, and then rinsing the fiber. After stirring for 1 hour, the fibers were fished out and the excess sodium alginate aqueous solution was discarded by centrifuge to obtain wet fibers with sodium alginate aqueous solution; the fibers were then immersed in a calcium chloride aqueous solution; the fibers were continuously stirred for 4 hours at a constant temperature of 25°C; after the reaction, the fibers were fished out and initially drained, and the cross-linked fibers were then rinsed with a large amount of deionized water for 3-5 times until no chloride ion precipitation was detected in the washing water using a silver nitrate solution; the washed fibers were centrifuged and dehydrated, and then dried to obtain modified basalt fibers.

[0009] Furthermore, the concentration of the sodium hydroxide aqueous solution is 1.0 mol / L; Furthermore, the concentration of the sodium alginate aqueous solution is 2.0% (w / v); Furthermore, the concentration of the calcium chloride aqueous solution is 2.0% (w / v).

[0010] The method for preparing the homemade functionalized fly ash comprises the following steps: taking fly ash and sodium hydroxide particles, placing them in a mortar, grinding and mixing them thoroughly, transferring them to a crucible, placing them in a muffle furnace, and calcining them for 1 hour; after the mixture cools, taking it out and grinding it with a grinder, and passing it through a 200-mesh sieve; then repeatedly washing it with a large amount of deionized water until the pH value of the filtrate is neutral, and then drying the final product in an oven at 105° C. for 12 hours to prepare alkali-activated fly ash; taking the prepared alkali-activated fly ash; placing it in a reactor, adding deionized water, and stirring to form a uniform suspension; and maintaining the temperature at 90° C.; adding MgCl2 solution and NaOH solution dropwise; after the addition is completed, maintaining the temperature at 90° C. and continuing the reaction for 90 minutes; and then passing the reaction product through a filtration oven. The obtained Mg(OH)2-coated fly ash was filtered and washed with a large amount of deionized water until neutral, and then dried at 105°C for 12 hours to obtain Mg(OH)2-coated modified fly ash; the prepared Mg(OH)2-coated fly ash was placed in a high-speed heating mixer and preheated to 110°C at 1000 rpm; N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was evenly sprayed into the high-speed rotating powder through an atomizing nozzle; high-speed mixing was continued at 110°C for 20 minutes to allow the methoxy end of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane to undergo sufficient dealcoholization condensation reaction with the hydroxyl group on the surface of Mg(OH)2; and the material was discharged after cooling to room temperature to obtain the final component homemade functional fly ash.

[0011] Furthermore, the calcination temperature of the muffle furnace is 700 degrees Celsius.

[0012] Furthermore, during the preparation of the homemade functionalized fly ash, the MgCl2 solution and the NaOH solution need to be added slowly and synchronously to the suspension, and while adding, they need to be continuously fine-tuned with dilute hydrochloric acid or dilute NaOH to keep the pH value of the reaction system at 10.

[0013] A green and low-carbon cementitious material for roadbed and a preparation method thereof: homemade functionalized fly ash, slag powder, steel slag powder and desulfurized gypsum are added together according to a proportion into a dry powder mixer, and stirred at a low speed for 3-5 minutes to fully mix them; finally, modified basalt fiber is added into the mixer, and stirred at a low speed for 2-3 minutes to ensure that the fiber is evenly distributed in the powder and to avoid agglomeration, thereby preparing a green and low-carbon cementitious material for roadbed.

[0014] The present invention has the beneficial effects: 1. The modified basalt fiber in the cementitious material of the present application forms a strong calcium alginate gel layer on the basalt fiber through the use of sodium alginate and calcium chloride. This transforms the originally hydrophobic and inert fiber surface into a fiber surface rich in carboxyl and hydroxyl groups. This greatly improves the dispersibility of the basalt fiber in the cementitious material, prevents fiber agglomeration, and can enhance the microstructural strength of the prepared roadbed material. 2. The self-made functionalized fly ash in the cementitious material of this application has its surface inertness removed by alkali activation, and is coated with a layer of Mg(OH)2. It is also grafted with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, which has a propyl group and a diamino functional group at its end. The two amino groups are connected by a relatively flexible ethylene group, allowing a certain degree of rotation and stretching between the two amino groups. When the interface is subjected to shear stress, the energy can be dissipated through the torsion and deformation of the molecular chain itself, thereby making the cementitious material have better toughness. 3. The modified basalt fibers in the present cementitious material have carboxyl and hydroxyl groups on their surfaces, while the self-functionalized fly ash has hydroxyl and amino groups on its surface. Under the action of water molecules, a multi-dimensional hydrogen bond network composed of a variety of strong and weak hydrogen bonds is formed at the microscopic interface between the fibers and the fly ash. When microcracks are generated in the material under stress, the large number of hydrogen bonds can efficiently dissipate the crack expansion energy, resulting in superior fracture toughness, impact resistance, and fatigue life of the material, making it more suitable for use as a roadbed material. 4. The cementitious material of the present application, as a roadbed material, contains a large number of hydroxyl and carboxyl groups in its components. During application, it will strongly combine with pore water molecules through hydrogen bonding, converting most of the free water into bound water. This greatly lowers the freezing point of the pore water and inhibits the formation of destructive ice crystals. This allows the roadbed material containing the cementitious material of the present application to maintain structural integrity and stable performance even under repeated freeze-thaw cycles, exhibiting excellent freeze-thaw resistance and thus excellent durability. 5. The cementitious material of this application utilizes a large amount of solid waste. Applying it to the roadbed material, which is also widely used, can not only solve the environmental problems caused by the accumulation of these solid wastes, but also utilize them in accordance with the green, circular and sustainable strategic development direction, and has huge market potential. DETAILED DESCRIPTION

[0015] To make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with Examples. The illustrative embodiments of the present invention and their description are only used to explain the present invention and are not intended to limit the present invention. In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each smaller range between the intermediate value within any stated value or stated range and any other stated value or intermediate value within the range is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded within the scope.

[0016] Unless otherwise indicated, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art. Although only preferred methods and materials are described herein, any methods and materials similar or equivalent to those described herein may also be used in the practice or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials associated with the documents. In the event of any conflict with any incorporated document, the contents of this specification shall prevail.

[0017] It will be apparent to those skilled in the art that various modifications and variations may be made to the specific embodiments described herein without departing from the scope or spirit of the invention. Other embodiments will be apparent to those skilled in the art from the description of the invention. The description and examples are intended to be exemplary only.

[0018] The words “include,” “including,” “have,” “contain,” etc. used in this document are open-ended terms, meaning including but not limited to.

[0019] The "parts" indicated in the following examples are all parts by weight.

[0020] Example 1 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 40 parts of slag powder, 25 parts of homemade functionalized fly ash, 15 parts of steel slag powder, 8 parts of desulfurized gypsum, and 2 parts of modified basalt fiber.

[0021] The slag powder is S95 grade granulated blast furnace slag powder; The steel slag powder is a powder obtained by grinding steel slag in a ball mill, and the specific surface area of ​​the steel slag powder is 450-650m 2 / kg, alkalinity greater than 1.8; The specific surface area of ​​the desulfurized gypsum is ≥450m 2 / kg; the P2O5 content of the desulfurized gypsum is 0.6-0.8wt%; In specific applications, the desulfurization gypsum meets the requirements of GB / T23456-2018 standard.

[0022] The modified basalt fiber preparation method comprises the following steps: weighing 50 g of basalt fiber and placing it in a reaction vessel; adding 400 mL of a 1.0 mol / L sodium hydroxide aqueous solution to ensure that the fiber is completely immersed; stirring at a low speed of 60 rpm, heating to 80° C., and reacting at this constant temperature for 2 hours; after the reaction is completed, stopping heating, draining the alkali solution, and repeatedly rinsing the fiber with deionized water until the pH value of the washing water reaches 7.0±0.2; transferring the washed fiber to an oven and drying it with forced air at 80° C. for 12 hours to prepare surface-activated dry basalt fiber; Immerse 50g of dry activated basalt fiber in 1L of 2.0% (w / v) sodium alginate aqueous solution; stir at 30rpm for 1 hour at room temperature to ensure that all fibers are fully and evenly wetted by the sodium alginate aqueous solution; remove the fiber and remove the excess sodium alginate aqueous solution through a centrifuge, so that 50g of basalt fiber absorbs 50g of sodium alginate aqueous solution; bring the total fiber weight to 100g; immediately immerse the 100g wet fiber with the sodium alginate aqueous solution in 2L of 2.0% (w / v) calcium chloride aqueous solution; stir at 60rpm for 4 hours at a constant temperature of 25℃; during this process, the sodium alginate on the fiber surface reacts with Ca²⁺ to form a water-insoluble calcium alginate gel layer; After the reaction is completed, the fibers are fished out and initially drained, and then the cross-linked fibers are rinsed with a large amount of deionized water for 3-5 times until no chloride ion precipitation is detected in the washing water using a silver nitrate solution. Finally, the washed fibers are centrifuged and dehydrated, and then placed in a vacuum oven at 60°C and dried for 24 hours to obtain modified basalt fibers.

[0023] In a specific implementation, the diameter of the monofilament of the basalt fiber is 9 μm to 15 μm, and the length is 2 cm to 4 cm.

[0024] The method for preparing the homemade functionalized fly ash comprises the following steps: weighing 100 g of fly ash and 80 g of sodium hydroxide particles, placing them in a mortar, and thoroughly grinding and mixing them. The uniformly mixed powder is then transferred to a high-temperature resistant ceramic crucible, placed in a muffle furnace, and calcined at 700° C. for 1 hour. After the mixture cools, it is taken out and ground into a fine powder using a grinder and passed through a 200-mesh sieve. The mixture is then repeatedly washed with a large amount of deionized water until the pH value of the filtrate is neutral. The final product is then dried in an oven at 105° C. for 12 hours to prepare alkali-activated fly ash. Take 50g of the prepared alkali-activated fly ash; place it in a reactor with a stirring and constant temperature jacket, add 2000ml of deionized water, and form a uniform suspension under stirring at 300rpm; heat the fly ash suspension in the reactor and keep the temperature at 90℃; add a total of 508ml of 0.4mol / L MgCl2 solution and 400ml of 0.6mol / L NaOH solution within 30min; during the preparation process, the MgCl2 solution and the NaOH solution need to be added slowly and synchronously to the suspension, and while adding, continuously fine-tune with dilute hydrochloric acid or dilute NaOH to keep the pH value of the reaction system at 10; after the addition is completed, maintain the constant temperature reaction at 90℃ for 90 minutes; then filter the reaction product, wash it with a large amount of deionized water until it is neutral, and then dry it at 105℃ for 12 hours to prepare Mg(OH)2-coated modified fly ash; The prepared Mg(OH)2-coated fly ash was placed in a high-speed heating mixer and preheated to 110°C at 1000 rpm; N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was evenly sprayed into the high-speed rotating powder through an atomizing nozzle; high-speed mixing was continued at 110°C for 20 minutes to allow the methoxy end of N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane to undergo sufficient dealcoholization condensation reaction with the hydroxyl group on the surface of Mg(OH)2; finally, the material was cooled to room temperature and discharged to obtain the final component of the homemade functionalized fly ash.

[0025] During specific implementation, the N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was purchased from Hubei New Blue Sky New Materials Co., Ltd.

[0026] A method for preparing a green and low-carbon cementitious material for roadbed comprises the following steps: adding homemade functionalized fly ash, slag powder, steel slag powder and desulfurized gypsum according to a proportion into a dry powder mixer, stirring at a low speed for 3-5 minutes to fully mix them; finally, adding modified basalt fiber into the mixer, stirring at a low speed for 2-3 minutes to ensure that the fiber is evenly distributed in the powder and to avoid agglomeration, thereby preparing a green and low-carbon cementitious material for roadbed.

[0027] Example 2 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 42 parts of slag powder, 27 parts of homemade functionalized fly ash, 17 parts of steel slag powder, 9 parts of desulfurized gypsum, and 3 parts of modified basalt fiber.

[0028] Among them, the preparation method of the homemade functionalized fly ash, the preparation method of the modified basalt fiber, and the preparation method of the green low-carbon cementitious material for roadbed in Example 2 are all consistent with those in Example 1.

[0029] Example 3 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 45 parts of slag powder, 29 parts of homemade functionalized fly ash, 19 parts of steel slag powder, 10 parts of desulfurized gypsum, and 3 parts of modified basalt fiber.

[0030] Among them, the preparation method of the homemade functionalized fly ash, the preparation method of the modified basalt fiber, and the preparation method of the green low-carbon cementitious material for roadbed in Example 3 are all consistent with those in Example 1.

[0031] Example 4 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, 32 parts of homemade functionalized fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

[0032] Among them, the preparation method of the homemade functionalized fly ash, the preparation method of the modified basalt fiber, and the preparation method of the green low-carbon cementitious material for roadbed in Example 4 are all consistent with those in Example 1.

[0033] Example 5 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 50 parts of slag powder, 35 parts of homemade functionalized fly ash, 25 parts of steel slag powder, 15 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

[0034] Among them, the preparation method of the homemade functionalized fly ash, the preparation method of the modified basalt fiber, and the preparation method of the green low-carbon cementitious material for roadbed in Example 5 are all consistent with those in Example 1.

[0035] Comparative Example 1 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, 32 parts of homemade functionalized fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of basalt fiber.

[0036] The difference between Comparative Example 1 and Example 4 is that the modification operation on the basalt fiber is omitted, and instead the commercially available product is directly applied to the green and low-carbon cementitious material for roadbed.

[0037] Comparative Example 2 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, 32 parts of fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

[0038] The difference between Comparative Example 2 and Example 4 is that the functional modification operation on fly ash is omitted, and instead the commercially available fly ash product is directly applied to the green and low-carbon cementitious material for roadbed.

[0039] Comparative Example 3 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, 32 parts of fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of basalt fiber.

[0040] The difference between Comparative Example 2 and Example 4 is that the functional modification operation on fly ash and the modification operation on basalt fiber are omitted, and instead the corresponding commercially available products are directly applied to the green and low-carbon cementitious materials for roadbed.

[0041] Comparative Example 4 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, homemade functionalized fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

[0042] The difference between Comparative Example 4 and Example 4 is that, in the functional modification operation of fly ash, the silane coupling agent sprayed from the atomizing nozzle is specifically an equal amount of γ-aminopropyltriethoxysilane.

[0043] Comparative Example 5 A green low-carbon cementitious material for roadbed is composed of the following components by weight: 48 parts of slag powder, homemade functionalized fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

[0044] The difference between Comparative Example 4 and Example 4 is that, in the functional modification operation of fly ash, the operation of spraying the silane coupling agent from the atomizing nozzle is not performed, but the modified fly ash coated with Mg(OH)2 is directly used in the green low-carbon cementitious material for roadbed.

[0045] The experimental concrete formula includes, by weight, 100 parts of cementitious material, 135 parts of fine aggregate, 195 parts of coarse aggregate, 1.5 parts of polycarboxylate water reducer, and 32 parts of water; the coarse aggregate is 5-15 mm continuously graded crushed stone; and the fine aggregate is machine-made sand.

[0046] The test concrete was prepared by placing the cementitious materials prepared in Examples 1-5 and Comparative Examples 1-5 into a mixer, adding fine aggregate and coarse aggregate into the mixer together, and slowly stirring for 3-5 minutes so that the surfaces of the coarse and fine aggregates were evenly coated with the cementitious material; then, a polycarboxylate water-reducing agent was dissolved in water, the mixer was turned on, and the polycarboxylate water-reducing agent aqueous solution was slowly and evenly added to the mixture. After all the mixture was added, it was rapidly stirred for 3-5 minutes until a uniform, non-segregated, and fluid concrete mixture was formed. The mixture was then poured into a test mold, vibrated to compactness, and then subjected to standard curing. After curing, the following performance tests were performed.

[0047] Test example Compressive strength test: refer to the "Standard for Test Methods of Ordinary Concrete Mixture Properties" to conduct compressive strength tests on the prepared test concrete, and calculate the 7d and 28d compressive strengths; Freeze-thaw resistance test: Refer to the slow freezing test conditions in the standard GB / T 50082-2009 "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete". After 75 freeze-thaw cycles, re-test the compressive strength and record the compressive strength retention rate; Impact resistance test: Referring to the ACI 544.2R-89 concrete impact compression test method, a drop hammer impact test apparatus was used for impact resistance testing. The test specimens were standard specimens (Φ150×64mm) that had undergone 28 days of standard curing. The hammer had a mass of 4.5kg, a drop height of 457mm, a force-transmitting ball diameter of 64mm, and a distance of 5mm between the four baffles and the specimen. During the test, the hammer fell freely, and the number of initial crack impacts (n1) was recorded. The test continued, and the specimen expanded in volume after the initial crack. When the specimen came into contact with any three of the four baffles, the specimen was considered to have failed, and the number of failure impacts (n2) was recorded. The performance test results are shown in Table 1: Table 1: Comprehensive performance analysis: Comparative Example 3 uses unmodified basalt fiber and fly ash, which has the worst performance, including compression resistance, freeze-thaw resistance, and impact resistance. However, in terms of impact resistance and freeze-thaw resistance, Comparative Examples 1 and 2 have certain performance advantages over Comparative Examples 3 and 4. The possible reason is that the modified basalt fiber in the cementitious material of the present application forms a strong calcium alginate gel layer on the basalt fiber through sodium alginate and calcium chloride, which makes the originally hydrophobic and inert fiber surface become a fiber surface rich in carboxyl and hydroxyl groups, greatly improving the dispersibility of the basalt fiber in the cementitious material. It prevents fiber agglomeration and can improve the microstructural strength of the prepared roadbed material; the homemade functionalized fly ash breaks the surface inertness of the fly ash through alkali activation, and is coated with a layer of Mg(OH)2 on its surface. It is also grafted with N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane, which has a propyl group and a double amino functional group at its end. The two amino groups are connected by a relatively flexible ethylene group, which allows a certain degree of rotation and stretching between the two amino groups; when the interface is subjected to shear stress, it can dissipate part of the energy through the twisting and deformation of its own molecular chain, thereby making the cementitious material have better toughness.

[0048] Comparative Example 4 differs from Example 4 only in that, during the functionalization modification of the fly ash, the silane coupling agent sprayed from the atomizing nozzle is an equal amount of γ-aminopropyltriethoxysilane. While this silane coupling agent can act as a grafting agent when grafted onto the fly ash surface and connected to the matrix or fiber, its shorter molecular structure tends to be more rigid. When the material is impacted or microcracks form, it cannot effectively dissipate energy. Instead, its inherent rigidity causes stress concentration at the interface, becoming a new source of microcracks. This direct transfer of stress accelerates failure. Comparative Example 5, which does not incorporate any silane coupling agent, exhibits slightly better freeze-thaw and impact resistance than Comparative Example 4. This performance degradation may be due to the grafting of γ-aminopropyltriethoxysilane in Comparative Example 4.

[0049] Furthermore, Examples 1-5 also confirm that as long as the surface of the specific modified basalt fiber in the cementitious material of the present application has carboxyl and hydroxyl groups, and the surface of the specific homemade functionalized fly ash has hydroxyl and amino groups, under the action of water molecules, a multiple three-dimensional hydrogen bond network interwoven by a variety of strong and weak hydrogen bonds is formed at the interface between the microscopic fiber and the fly ash. When microcracks are generated in the material under stress, a large number of hydrogen bonds can efficiently dissipate the energy of crack expansion, which makes the fracture toughness, impact resistance and fatigue life of the material more excellent, and more suitable for application in roadbed materials.

[0050] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the scope of protection of the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A green low-carbon cementitious material for roadbed, characterized in that: The composition is as follows by weight: 40-50 parts of slag powder, 25-35 parts of homemade functionalized fly ash, 15-25 parts of steel slag powder, 8-15 parts of desulfurized gypsum, and 2-4 parts of modified basalt fiber.

2. A green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The ingredients include, by weight: 48 parts of slag powder, 32 parts of homemade functionalized fly ash, 22 parts of steel slag powder, 12 parts of desulfurized gypsum, and 4 parts of modified basalt fiber.

3. The green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The slag powder is S95 grade granulated blast furnace slag powder.

4. The green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The steel slag powder is a powder obtained by grinding steel slag in a ball mill, and the specific surface area of ​​the steel slag powder is 450-650m 2 / kg, alkalinity greater than 1.

8.

5. The green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The specific surface area of ​​the desulfurized gypsum is ≥450m 2 / kg; the P2O5 content of the desulfurization gypsum is 0.6~0.8wt%.

6. The green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The modified basalt fiber preparation method comprises the following steps: taking basalt fiber and placing it in a reaction container; adding a sodium hydroxide aqueous solution to completely immerse the fiber; stirring at a low speed, heating to 80° C., and reacting at a constant temperature for 2 hours; stopping heating after the reaction is completed, draining the alkali solution, and repeatedly rinsing the fiber with deionized water until the pH value of the washed water reaches 7.0±0.2; air-drying the washed fiber to obtain surface-activated dry basalt fiber; taking the dried activated basalt fiber and immersing it in a sodium alginate aqueous solution; stirring at a low speed at room temperature, and then rinsing the fiber. After stirring for 1 hour, the fibers were fished out and the excess sodium alginate aqueous solution was discarded by centrifuge to obtain wet fibers with sodium alginate aqueous solution; the fibers were then immersed in a calcium chloride aqueous solution; the fibers were continuously stirred for 4 hours at a constant temperature of 25°C; after the reaction, the fibers were fished out and initially drained, and the cross-linked fibers were then rinsed with a large amount of deionized water for 3-5 times until no chloride ion precipitation was detected in the washing water using a silver nitrate solution; the washed fibers were centrifuged and dehydrated, and then dried to obtain modified basalt fibers.

7. The green low-carbon cementitious material for roadbed according to claim 1, characterized in that: The method for preparing the homemade functionalized fly ash comprises the following steps: taking fly ash and NaOH particles, placing them in a mortar, grinding and mixing them thoroughly, transferring them to a crucible, placing them in a muffle furnace, and calcining them for 1 hour; after the mixture cools, taking it out and grinding it with a grinder, and passing it through a 200-mesh sieve; then repeatedly washing it with a large amount of deionized water until the pH value of the filtrate is neutral, and then drying the final product in an oven at 105° C. for 12 hours to prepare alkali-activated fly ash; taking the prepared alkali-activated fly ash, placing it in a reactor, adding deionized water, and stirring to form a uniform suspension; and maintaining the temperature at 90° C.; adding MgCl2 solution and NaOH solution dropwise; and after the addition is complete. After that, the constant temperature reaction was continued at 90°C for 90 minutes; the reaction product was then filtered and washed with a large amount of deionized water until neutral, and then dried at 105°C for 12 hours to prepare Mg(OH)2-coated modified fly ash; the prepared Mg(OH)2-coated fly ash was taken and placed in a high-speed heating mixer, and preheated to 110°C at 1000rpm; N-β-(aminoethyl)-γ-aminopropyltrimethoxysilane was evenly sprayed into the high-speed rotating powder through an atomizing nozzle; high-speed mixing was continued at 110°C for 20 minutes, and finally the material was cooled to room temperature and discharged to prepare the homemade functionalized fly ash.

8. The green low-carbon cementitious material for roadbed according to claim 7, characterized in that: The calcination temperature of the muffle furnace is 700 degrees Celsius.

9. The green low-carbon cementitious material for roadbed according to claim 7, characterized in that: During the preparation of the homemade functionalized fly ash, the MgCl2 solution and the NaOH solution need to be added slowly and synchronously to the suspension; and while adding, dilute hydrochloric acid or dilute NaOH is used to continuously fine-tune the pH value of the reaction system so that the pH value is always maintained at 10.

10. A method for preparing a green low-carbon cementitious material for roadbed according to any one of claims 1 to 8, characterized in that: The preparation method comprises the following steps: adding homemade functionalized fly ash, slag powder, steel slag powder and desulfurized gypsum according to a proportion into a dry powder mixer, stirring at a low speed for 3-5 minutes to fully mix them; finally, adding modified basalt fiber into the mixer, stirring at a low speed for 2-3 minutes to ensure that the fiber is evenly distributed in the powder and to avoid agglomeration, thereby preparing a green and low-carbon cementitious material for roadbed.

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