Basalt fiber-multiple solid waste synergistic modified cement soil

Abstract

The application relates to the technical field of building materials, and discloses a basalt fiber-multiple solid waste synergistically modified cement soil. The dispersibility of basalt fiber in the cement soil is improved by surface grafting modification of the basalt fiber, and the synergistic effect of the two of the chemical cementation filling of multiple solid wastes and the physical reinforcement bridging of the basalt fiber is utilized, so that the comprehensive performance of the cement soil is optimized, and the cement soil is suitable for rock-soil engineering scenes such as water conservancy engineering seepage prevention, roadbed reinforcement, foundation pit water resistance, pollution site blocking and the like.

Description

Technical Field

[0001] This invention relates to the field of building materials technology, specifically to a basalt fiber-multi-element solid waste synergistic improvement method for cement soil. Background Technology

[0002] Cement-soil is widely used in small and medium-sized projects and emergency projects due to its readily available raw materials, convenient construction, and low cost. However, traditional cement-soil has inherent defects: it is brittle and has poor crack resistance, and is prone to brittle failure without warning under complex stress or environmental conditions. Cement production has high energy consumption and large carbon emissions. The production of 1 ton of cement consumes about 1.5 tons of non-renewable resources and emits 1.02 tons of CO2.

[0003] Solid wastes such as municipal solid waste incineration slag, fly ash, and desulfurization gypsum are rich in active components such as SiO2, Al2O3, and CaO, and have potential cementitious activity. However, when a single solid waste is mixed into cement soil, it is difficult to balance strength, toughness, and impermeability, and structural defects are easily caused by uneven hydration reactions.

[0004] In existing technologies, fiber reinforcement can improve the toughness of cement-soil through bridging, but these are mostly binary composite systems of fiber and cement. Multi-component solid waste remediation focuses on chemical bonding and pore filling, and systematic research on the synergistic effect of these two methods is still lacking. Furthermore, existing mix design often suffers from deviations in raw material dosage, making it difficult to meet the performance stability requirements of engineering projects. Therefore, it is necessary to provide a basalt fiber-multi-component solid waste synergistically modified cement-soil with impermeability and crack resistance, suitable for geotechnical engineering scenarios such as seepage prevention in water conservancy projects, roadbed reinforcement, foundation pit impoundment, and contaminated site containment. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and provide a basalt fiber-multi-element solid waste synergistic improvement method for cement-soil. By surface grafting modification of basalt fibers, the dispersibility of basalt fibers in cement-soil is improved. At the same time, by utilizing the synergistic effect of chemical cementing filling by multi-element solid waste and physical reinforcement bridging by basalt fibers, the comprehensive performance of cement-soil is optimized, making it suitable for geotechnical engineering scenarios such as seepage prevention in water conservancy projects, roadbed reinforcement, foundation pit waterproofing, and contaminated site isolation.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0007] A method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil includes the following steps:

[0008] Step (1): Mix alkali lignin, sodium sulfite, and NaOH aqueous solution evenly, react, adjust the pH to neutral after the reaction is complete, centrifuge, wash, and dry to obtain modified lignin;

[0009] Modified lignin and epichlorohydrin were mixed and reacted. After the reaction was completed, chloromethoxy polyethylene glycol was added and the reaction was continued. After the reaction was completed, the mixture was cooled, precipitated, filtered, washed, and dried to obtain lignin-based epoxy resin.

[0010] Step (2): Dilute the epoxy resin, add toluene diisocyanate and dibutyltin dilaurate, stir and react. After the reaction is complete, heat up, add 2,2-dimethylolpropionic acid, continue stirring and react. After the reaction is complete, cool down, neutralize, add water to emulsify, and obtain waterborne epoxy resin.

[0011] A lignin-based epoxy resin, an aqueous epoxy resin, and water are mixed and ultrasonically dispersed to obtain an epoxy resin wetting agent.

[0012] Step (3): Place the basalt fiber in an aqueous solution of hexadecyltrimethylammonium bromide, soak it, add tetraethyl silicate / ethanol solution, react, remove it after the reaction is complete, wash it, and obtain the intermediate product;

[0013] γ-aminopropyltriethoxysilane, water, and ethanol were mixed, allowed to stand, an intermediate product was added, the mixture was soaked, removed, and dried to obtain KH550 modified basalt fiber.

[0014] KH550 modified basalt fiber was placed in an epoxy resin impregnating agent, ultrasonically dispersed, reacted, removed, cured, washed, and dried to obtain modified basalt fiber.

[0015] Step (4): Mix the cementitious material, bentonite, and clay, add the modified basalt fiber, and continue to dry mix until uniform; add water and continue to mix to obtain the mixture;

[0016] Step (5): Pour the mixture into the mold, let it stand and demold to obtain the specimen; cure the specimen to obtain basalt fiber-multi-element solid waste synergistic improved cement soil.

[0017] Preferably, in step (1), when preparing modified lignin, the concentration of NaOH aqueous solution is 8-10wt%; the ratio of alkali lignin, sodium sulfite, and NaOH aqueous solution is 0.3g:(0.6g-2.4g):(40mL-50mL); the reaction conditions are: reaction at 70-90℃ for 0.5-2h.

[0018] Preferably, in step (1), when preparing lignin-based epoxy resin, the mass ratio of modified lignin, epichlorohydrin, and chloromethoxy polyethylene glycol is 0.1:(0.1-0.25):(0.1-0.25); the reaction and continued reaction conditions are: reaction at pH 10-12 and temperature 70-80℃ for 3-4 hours.

[0019] Preferably, in step (2): the molar ratio of epoxy resin, toluene diisocyanate, and 2,2-dimethylolpropionic acid is (1-2):0.5:0.5; the amount of dibutyltin dilaurate added is 0.01-0.1wt% of the amount of toluene diisocyanate added; the reaction conditions are: stirring at room temperature for 1-2 hours; the reaction conditions for continued reaction are: stirring at 50-60°C for 3-4 hours; the solid content of the waterborne epoxy resin is 20-40wt%; and the mass ratio of lignin-based epoxy resin, waterborne epoxy resin, and water is (5-10):(5-10):(80-90).

[0020] Preferably, in step (3), when preparing the intermediate product: the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 1-2 wt%; the concentration of tetraethyl silicate in the tetraethyl silicate / ethanol solution is 15-30 wt%; the ratio of basalt fiber, hexadecyltrimethylammonium bromide aqueous solution, and tetraethyl silicate / ethanol solution is 1 g:(20 mL-50 mL):(20 mL-50 mL); the soaking conditions are: soaking at 50-60℃ for 1-2 h; the reaction conditions are: reacting at pH 10-12 and 50-60℃ for 10-20 h.

[0021] Preferably, in step (3), when preparing KH550 modified basalt fiber, the mass ratio of γ-aminopropyltriethoxysilane, water, ethanol and intermediate product is (0.1-1):(25-30):(25-30):1; the soaking conditions are: soaking at room temperature for 30-60 minutes.

[0022] Preferably, in step (3), when preparing modified basalt fiber, the mass ratio of KH550 modified basalt fiber to epoxy resin impregnator is 1:(50-100); the reaction conditions are: reacting at 50-70℃ for 2-4 hours; and the curing conditions are: curing at 90-100℃ for 2-3 hours.

[0023] Preferably, in step (4): the cementitious material is prepared by mixing cement, fly ash, slag and desulfurized gypsum; in the cementitious material, the mass ratio of cement to slag is (6-9):(1-4), the amount of fly ash in the cementitious material is 10-30wt%, and the amount of desulfurized gypsum in the cementitious material is 6-18wt%; the mass ratio of cementitious material, bentonite, clay and modified basalt fiber is 15:6:100:(0.5-1.5); the water content of the mixture is 47.76-48.15%, and the slump is 180-220mm.

[0024] Preferably, in step (5), the curing conditions are: curing for 28 days at a temperature of 20℃±5℃ and a humidity of ≥95%.

[0025] Preferably, a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil as described above is used to prepare basalt fiber-multi-element solid waste synergistically modified cement soil.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] 1. This invention improves the dispersibility of basalt fibers in cement-soil by surface grafting modification of basalt fibers. At the same time, it utilizes the synergistic effect of chemical cementation filling of multi-component solid waste and physical reinforcement bridging of basalt fibers to optimize the comprehensive performance of cement-soil. It is suitable for geotechnical engineering scenarios such as seepage prevention in water conservancy projects, roadbed reinforcement, foundation pit water isolation, and contaminated site isolation.

[0028] 2. This invention uses sodium sulfite to modify lignin and then performs an etherification reaction to introduce hydrophilic polyether segments and epoxy functional groups into the lignin, thus preparing a lignin-based epoxy resin. Then, by reacting the isocyanate groups of toluene diisocyanate with the hydroxyl groups of the epoxy resin, waterborne polyurethane segments are introduced into the epoxy resin, further improving its flexibility and hydrophilicity, resulting in a waterborne epoxy resin. By compounding the lignin-based epoxy resin with the waterborne epoxy resin, the resulting epoxy resin wetting agent can, on the one hand, chemically bond the epoxy resin to KH550 modified basalt fibers through the ring-opening reaction of epoxy and amino groups; on the other hand, it can improve the dispersibility of basalt fibers in the cement matrix through hydrophilic groups and polyether segments, thereby improving interfacial adhesion performance.

[0029] This invention adds modified basalt fibers to cement-soil, which can improve the overall performance of cement-soil from three aspects: three-dimensional network constraint, crack bridging and propagation inhibition, and interface optimization. Specifically, the uniformly dispersed basalt fibers form a three-dimensional spatial network in the cement-soil, constraining the relative displacement of soil particles and solid waste particles, thus improving the overall integrity of the material. When the cement-soil is subjected to load and microcracks are generated, the fibers cross the cracks through interfacial friction and adhesion, transferring stress and altering the crack propagation path, extending the crack propagation distance, and transforming brittle failure into ductile failure. The modified basalt fibers have hydrophilic groups on their surface and an increased specific surface area, allowing them to bond tightly with the cementitious material, thus improving the bond strength between the fiber and the matrix interface.

[0030] 3. This invention uses cement, fly ash, slag, and desulfurized gypsum as cementing materials, which are mixed with bentonite, clay, modified basalt fiber, and water, and then cured to form cement soil. Among them, the active SiO2 and Al2O3 in slag and fly ash react with the cement hydration product Ca(OH)2 to produce a large amount of CSH gel. The gel fills the soil pores, making the microstructure denser, while delaying the release of hydration heat and avoiding the appearance of early microcracks. This reflects the synergistic cementing and filling effect of multiple solid wastes.

[0031] Desulfurized gypsum, acting as a sulfate activator, reacts with cement hydration product Al(OH)4 in an alkaline environment (pH≥10). - The combination produces ettringite (AFt). The micro-expansion effect of ettringite can fill the tiny pores and regulate the hydration rate, making the cementitious products (CSH and AFt) more evenly distributed in the matrix and improving the strength of the interfacial transition zone. This reflects the hydration regulation effect of desulfurized gypsum.

[0032] Sodium-based bentonite expands by absorbing water to form a colloid that encapsulates soil and solid waste particles, improving the workability of the mixture. At the same time, sodium-based bentonite forms a "water buffer layer" in the matrix, slowly releasing water to promote the later hydration of cement. This demonstrates the workability optimization effect of bentonite.

[0033] 4. This invention reduces the porosity of cement-soil by utilizing the bonding and filling effects of multi-component solid waste, optimizes the interfacial contact environment between fibers and the matrix, and improves fiber bridging efficiency. Conversely, the reinforcement and bridging effects of fibers compensate for the insufficient toughness of the multi-component solid waste bonding system. The two work together to improve the strength, toughness, and impermeability of cement-soil, solving the shortcomings of using a single improvement system to improve cement-soil. Attached Figure Description

[0034] Figure 1 These are actual images of the basalt fiber-multi-element solid waste synergistically improved cement soil prepared in Example 9 of the present invention. In the figures, (a) and (b) are actual images of the cement soil specimen before demolding, and (c) and (d) are actual images of the cement soil specimen after demolding.

[0035] Figure 2 These are bar charts and line graphs of the 7-day compressive strength and 28-day compressive strength of cement-soil prepared in Examples 4-9 and Comparative Examples 1-3 of this invention. Detailed Implementation

[0036] The present invention will be further illustrated below through specific embodiments. The following embodiments are specific implementations of the present invention, but the implementation of the present invention is not limited to the following embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and are included within the protection scope of the present invention.

[0037] Example 1

[0038] This embodiment discloses a method for preparing modified basalt fibers, including the following steps:

[0039] Step (1): Mix 0.3g alkali lignin, 1.2g sodium sulfite and 40mL of 10wt% NaOH aqueous solution evenly, react at 85℃ for 1h, after the reaction is completed, add 1wt% HCl aqueous solution to adjust the pH value to 7, centrifuge to collect the precipitate, wash with water, and dry at 40℃ for 12h to obtain modified lignin.

[0040] 0.1 g of modified lignin and 0.2 g of epichlorohydrin were mixed at 60 °C for 1 h, the pH was adjusted to 11, and the temperature was raised to 80 °C for 3 h. After the reaction was completed, 0.1 g of chloromethoxy polyethylene glycol was added, and the reaction was continued at pH 11 and 80 °C for 3 h. After the reaction was completed, the mixture was cooled to room temperature, n-hexane was added, the mixture was allowed to stand to precipitate, filtered, washed with ethanol, and dried at 40 °C for 12 h to obtain lignin-based epoxy resin.

[0041] Step (2): Dilute epoxy resin E51 with acetone, add toluene diisocyanate and dibutyltin dilaurate, stir and react at room temperature for 1.5 h. After the reaction is completed, heat to 60°C, add 2,2-dimethylolpropionic acid, continue stirring for 3.5 h. After the reaction is completed, cool to 50°C, add triethylamine to neutralize to neutral, add water and stir to emulsify, to obtain waterborne epoxy resin with a solid content of 30 wt%.

[0042] The molar ratio of epoxy resin E51, toluene diisocyanate, and 2,2-dimethylolpropionic acid is 1:0.5:0.5; the amount of dibutyltin dilaurate added is 0.05 wt% of the amount of toluene diisocyanate added.

[0043] Mix 10g of lignin-based epoxy resin, 10g of waterborne epoxy resin and 80g of water, and disperse evenly by ultrasonication to obtain epoxy resin wetting agent.

[0044] Step (3): Place 1g of basalt fiber with a length of 3mm in 50mL of 2wt% hexadecyltrimethylammonium bromide aqueous solution and soak it at 60℃ for 1h. Add 50mL of 20wt% tetraethyl silicate / ethanol solution, adjust the pH to 11, and react at 60℃ for 12h. After the reaction is completed, take it out and wash it with ethanol to obtain the intermediate product.

[0045] Mix 1g of γ-aminopropyltriethoxysilane, 25g of water, and 25g of ethanol, let stand for hydrolysis for 30min, add 1g of intermediate product, soak at room temperature for 30min, take out, and dry at 110℃ for 2h to obtain KH550 modified basalt fiber.

[0046] 1g of KH550 modified basalt fiber was placed in 50g of epoxy resin impregnating agent, ultrasonically dispersed for 30min, and then heated to 60℃ for 3h. After the reaction was completed, it was taken out and cured at 100℃ for 2h. It was then washed with acetone and dried at 60℃ for 12h to obtain modified basalt fiber.

[0047] Example 2

[0048] The difference from Example 1 is that "basalt fiber with a length of 3 mm" is replaced with "basalt fiber with a length of 6 mm", while other parameters and conditions are the same as in Example 1.

[0049] Example 3

[0050] The difference from Example 1 is that "basalt fiber with a length of 3 mm" is replaced with "basalt fiber with a length of 9 mm", while other parameters and conditions are the same as in Example 1.

[0051] Example 4

[0052] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0053] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 30g of the modified basalt fiber prepared in Example 1 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0054] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0055] Step (2): Pour the mixture into a 150mm×150mm×150mm cubic mold in two layers (clean and free of oil, with the inner wall coated with a 1:1 ratio of machine oil and grease as a release agent). Vibrate each layer for 40 seconds using a 50Hz vibrating table to remove air bubbles. Smooth the surface of the mold, cover with plastic wrap, and let it stand for 24 hours before demolding to obtain the specimen.

[0056] Step (3): Place the specimen in a standard curing room, control the temperature at 20℃±2℃ and the humidity at 95%, and cure for 7 days and 28 days; replenish water once a day during the curing period to avoid water loss from the surface of the specimen; after curing, basalt fiber-multi-element solid waste synergistic modified cement soil is obtained.

[0057] Example 5

[0058] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0059] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 60g of the modified basalt fiber prepared in Example 1 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0060] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0061] Step (2): The mixture is molded and cured to obtain basalt fiber-multi-element solid waste synergistic improved cement soil;

[0062] The parameters and conditions for molding and curing are the same as in Example 4.

[0063] Example 6

[0064] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0065] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 30g of the modified basalt fiber prepared in Example 2 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0066] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0067] Step (2): The mixture is molded and cured to obtain basalt fiber-multi-element solid waste synergistic improved cement soil;

[0068] The parameters and conditions for molding and curing are the same as in Example 4.

[0069] Example 7

[0070] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0071] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 60g of the modified basalt fiber prepared in Example 2 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0072] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0073] Step (2): The mixture is molded and cured to obtain basalt fiber-multi-element solid waste synergistic improved cement soil;

[0074] The parameters and conditions for molding and curing are the same as in Example 4.

[0075] Example 8

[0076] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0077] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 30g of the modified basalt fiber prepared in Example 3 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0078] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0079] Step (2): The mixture is molded and cured to obtain basalt fiber-multi-element solid waste synergistic improved cement soil;

[0080] The parameters and conditions for molding and curing are the same as in Example 4.

[0081] Example 9

[0082] This embodiment discloses a method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, including the following steps:

[0083] Step (1): Pour 418.5g of cement, 180g of fly ash, 162g of desulfurized gypsum, 139.5g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and stir at 150r / min for 70s. Add 60g of the modified basalt fiber prepared in Example 3 and continue to dry mix at 120r / min for 30s until the mixture is uniform.

[0084] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 150 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0085] Step (2): The mixture is molded and cured to obtain basalt fiber-multi-element solid waste synergistic improved cement soil;

[0086] The parameters and conditions for molding and curing are the same as in Example 4.

[0087] Comparative Example 1

[0088] This comparative example discloses a method for preparing cement-soil, including the following steps:

[0089] Step (1): Pour 900g of cement, 360g of bentonite, and 6000g of clay into a forced mixer and mix at 150r / min for 70s until evenly mixed.

[0090] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 130 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0091] Step (2): The mixture is molded and cured to obtain cement soil;

[0092] The parameters and conditions for molding and curing are the same as in Example 4.

[0093] Comparative Example 2

[0094] This comparative example discloses a method for preparing cement-modified soil through synergistic modification of multiple solid wastes, comprising the following steps:

[0095] Step (1): Pour 680.4g of cement, 90g of fly ash, 54g of desulfurized gypsum, 75.6g of slag, 360g of bentonite, and 6000g of clay into a forced mixer and mix at 150r / min for 70s until evenly mixed.

[0096] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 130 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0097] Step (2): The mixture is molded and cured to obtain cement soil synergistically improved by multiple solid wastes;

[0098] The parameters and conditions for molding and curing are the same as in Example 4.

[0099] Comparative Example 3

[0100] This comparative example discloses a method for preparing cement-modified soil through synergistic modification of multiple solid wastes, comprising the following steps:

[0101] Step (1): Pour 418.5g cement, 180g fly ash, 162g desulfurized gypsum, 139.5g slag, 360g bentonite, and 6000g clay into a forced mixer and mix at 150r / min for 70s until evenly mixed.

[0102] Under stirring conditions of 150 r / min, 3510 g of water was slowly added to the mixer at a water addition rate of 50 mL / s and stirred for 130 s. During the stirring process, the state of the mixture was observed to ensure that a uniform paste-like mixture without segregation was formed.

[0103] Step (2): The mixture is molded and cured to obtain cement soil synergistically improved by multiple solid wastes;

[0104] The parameters and conditions for molding and curing are the same as in Example 4.

[0105] In the above examples and comparative examples: KH550 is γ-aminopropyltriethoxysilane; the molecular weight of chloromethoxy polyethylene glycol (mPEG-Cl) is 1000; the cement is P conforming to the GB175-2023 standard for general-purpose Portland cement. O42.5 cement, sieved through a 45μm square-hole sieve before use; slag from municipal solid waste incineration furnace, with a continuous particle size distribution of 0.05mm-0.5mm, screened to remove impurities, and a moisture content ≤1%; fly ash with a particle size ≥300 mesh, conforming to GB / T1596-2017 "Fly Ash for Cement and Concrete" standard, and an active SiO2 content ≥40%; sieved through a 45μm square-hole sieve before use; desulfurized gypsum with a particle size of 0.05mm-0.1mm, purity ≥90%, dried to remove free moisture; sieved through a 45μm square-hole sieve before use; bentonite is sodium-based bentonite, with an alkalinity coefficient ≥1 and a specific surface area ≥20m² / g; clay is mainly composed of silt and silty clay, containing a small amount of plant roots, with a density of 18.1g / cm³. 3It has a liquid limit of 37.20%, a plastic limit of 18.02%, and a natural moisture content of 30%-35.8%. According to GB / T50145-2007 "Engineering Classification Standard for Soil", it belongs to low liquid limit clay. The basalt fiber has a fiber length of 3mm-9mm, a tensile strength ≥3000MPa, and an elastic modulus of 70-90GPa. The pH value of the water is 7.0-7.5.

[0106] Experimental data characterization and performance testing

[0107] The cement-soil prepared in Examples 4-9 and Comparative Examples 1-3 were subjected to comprehensive performance tests. Specific test results are shown in Table 1.

[0108] Table 1

[0109]

[0110] The tests for each index in Table 1 were conducted according to the following standards: Compressive strength was tested according to GB / T50081-2019 "Standard for Test Methods of Physical and Mechanical Properties of Concrete", using a YES-S1000KN digital display hydraulic pressure testing machine, with a uniform loading rate of 0.05-0.1MPa / s, recording the failure load, and calculating the cubic compressive strength; Permeability coefficient was tested according to JGJ / T291-2012 "Technical Specification for Construction of Cast-in-Place Plastic Concrete Impermeable Core Wall", using a TSY-10 triaxial testing system to conduct flexible wall permeability tests and determine the 28-day permeability coefficient; Brittleness index was calculated by obtaining the stress-strain curve from the compressive strength test (the product of the strain corresponding to the peak load and the average stress before the peak load), quantitatively evaluating the material ductility.

[0111] As can be seen from the results in Table 1, when the mass ratio of cement to slag is 7.5:2.5, the slag can play a cementing role while avoiding interface defects caused by excessive slag, thus improving both strength and impermeability. When the fly ash content is 20%, the reaction of active SiO2, Al2O3 and cement hydration product Ca(OH)2 produces the most CSH gel. When the desulfurized gypsum content is 18%, the generated ettringite (AFt) has the best micro-expansion effect, filling pores and reducing the permeability coefficient.

[0112] As shown in Table 1, after 28 days of curing, compared with the fiber-free comparative examples (Examples 4-9), the compressive strength of the cement-soil was improved, the permeability coefficient was reduced, and the brittleness index decreased, achieving a synergistic effect of physical reinforcement and chemical bonding. When the fiber content was 0.5%-1.0%, the compressive strength of the cement-soil increased, the permeability coefficient decreased, and the brittleness was improved, with 1.0% content being optimal. When the fiber length was 3mm-9mm, the compressive strength gradually increased and the permeability coefficient decreased, with 9mm length providing the best bridging and support effect. In summary, the addition of modified basalt fiber significantly improved the comprehensive performance of cement-soil.

[0113] It should be noted that the embodiments described above are only for explaining the present invention and do not constitute any limitation on the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory terms, not limiting terms. Modifications can be made to the present invention within the scope of the claims, and revisions can be made to the present invention without departing from the scope and spirit of the present invention. Although the present invention described herein relates to specific methods, materials, and embodiments, it does not mean that the present invention is limited to the specific examples disclosed herein; on the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil, characterized in that, Includes the following steps: Step (1): Basalt fiber is placed in an aqueous solution of hexadecyltrimethylammonium bromide, soaked, and tetraethyl silicate / ethanol solution is added. After the reaction is completed, the fiber is removed, washed, and the intermediate product is obtained. γ-aminopropyltriethoxysilane, water, and ethanol were mixed, allowed to stand, an intermediate product was added, the mixture was soaked, removed, and dried to obtain KH550 modified basalt fiber. Step (2): Place KH550 modified basalt fiber in epoxy resin impregnating agent, disperse it ultrasonically, react it, take it out after the reaction is completed, cure it, wash it, dry it, and obtain modified basalt fiber. The epoxy resin wetting agent is prepared by the following steps: S1. Mix alkali lignin, sodium sulfite, and NaOH aqueous solution evenly, react, adjust the pH to neutral after the reaction is complete, centrifuge, wash, and dry to obtain modified lignin. S2. Mix modified lignin and epichlorohydrin and react. After the reaction is complete, add chloromethoxy polyethylene glycol and continue the reaction. After the reaction is complete, cool, precipitate, filter, wash and dry to obtain lignin-based epoxy resin. S3. Dilute the epoxy resin, add toluene diisocyanate and dibutyltin dilaurate, stir and react. After the reaction is complete, heat up, add 2,2-dimethylolpropionic acid, continue stirring and react. After the reaction is complete, cool down, neutralize, add water to emulsify, and obtain waterborne epoxy resin. A lignin-based epoxy resin, an aqueous epoxy resin, and water are mixed and ultrasonically dispersed to obtain an epoxy resin wetting agent. Step (3): Mix the cementitious material, bentonite, and clay, add the modified basalt fiber, and continue to dry mix until uniform; add water and continue to mix to obtain the mixture; Step (4): Pour the mixture into the mold, let it stand and demold to obtain the specimen; cure the specimen to obtain basalt fiber-multi-element solid waste synergistic improved cement soil.

2. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (1), when preparing the intermediate product: the concentration of the hexadecyltrimethylammonium bromide aqueous solution is 1-2wt%; the concentration of tetraethyl silicate in the tetraethyl silicate / ethanol solution is 15-30wt%; the ratio of basalt fiber, hexadecyltrimethylammonium bromide aqueous solution, and tetraethyl silicate / ethanol solution is 1g:(20mL-50mL):(20mL-50mL); the soaking conditions are: soaking at 50-60℃ for 1-2h; the reaction conditions are: reacting at pH 10-12 and 50-60℃ for 10-20h.

3. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (1), when preparing KH550 modified basalt fiber, the mass ratio of γ-aminopropyltriethoxysilane, water, ethanol and intermediate product is (0.1-1):(25-30):(25-30):1; the soaking conditions are: soaking at room temperature for 30-60 minutes.

4. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (2), when preparing the epoxy resin impregnating agent, the concentration of NaOH aqueous solution in S1 is 8-10wt%; the ratio of alkali lignin, sodium sulfite, and NaOH aqueous solution is 0.3g:(0.6g-2.4g):(40mL-50mL); the reaction conditions are: reacting at 70-90℃ for 0.5-2h.

5. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (2), when preparing the epoxy resin impregnating agent, the mass ratio of modified lignin, epichlorohydrin, and chloromethoxy polyethylene glycol in S2 is 0.1:(0.1-0.25):(0.1-0.25); the reaction and continued reaction conditions are: reacting at a pH of 10-12 and a temperature of 70-80℃ for 3-4 hours.

6. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (2), when preparing the epoxy resin impregnating agent, in S3: the molar ratio of epoxy resin, toluene diisocyanate, and 2,2-dimethylolpropionic acid is (1-2):0.5:0.5; the amount of dibutyltin dilaurate added is 0.01-0.1wt% of the amount of toluene diisocyanate added; the reaction conditions are: stirring at room temperature for 1-2 hours; the reaction conditions for continued reaction are: stirring at 50-60℃ for 3-4 hours; the solid content of the waterborne epoxy resin is 20-40wt%; the mass ratio of lignin-based epoxy resin, waterborne epoxy resin, and water is (5-10):(5-10):(80-90).

7. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (2), the mass ratio of KH550 modified basalt fiber to epoxy resin impregnator is 1:(50-100); the reaction conditions are: reacting at 50-70℃ for 2-4 hours; and the curing conditions are: curing at 90-100℃ for 2-3 hours.

8. The method for preparing basalt fiber-multi-element solid waste synergistically improved cement soil according to claim 1, characterized in that, In step (3): the cementitious material is prepared by mixing cement, fly ash, slag and desulfurized gypsum; in the cementitious material, the mass ratio of cement to slag is (6-9):(1-4), the amount of fly ash in the cementitious material is 10-30wt%, and the amount of desulfurized gypsum in the cementitious material is 6-18wt%; the mass ratio of cementitious material, bentonite, clay and modified basalt fiber is 15:6:100:(0.5-1.5); the water content of the mixture is 47.76-48.15%, and the slump is 180-220mm.

9. A method for preparing basalt fiber-multi-element solid waste synergistically modified cement soil according to any one of claims 1-8, wherein the basalt fiber-multi-element solid waste synergistically modified cement soil is prepared.

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