A nanomaterial-based anti-frost-cracking saline soil curing agent and a preparation method thereof

Abstract

The application discloses an anti-frost-cracking saline soil solidifying agent based on nanomaterials and a preparation method thereof, and relates to the technical field of soil solidifying agents. The preparation method comprises the following steps: uniformly stirring and mixing cement and basalt fibers to obtain premix; adding silica fume, nanosilica and polyacrylamide into the premix, and continuously stirring and mixing to obtain the anti-frost-cracking saline soil solidifying agent based on nanomaterials. The silica fume and nanosilica can effectively fill the gaps between cement particles, reduce porosity and improve the compactness of the solidified soil. After the nanosilica is hydrophobically modified by polydimethylsiloxane, a hydrophobic network is formed in the material, further hindering water penetration. Meanwhile, the tendon solidification of the basalt fibers and the space netting reinforced structure constructed by the polyacrylamide enhance the anti-cracking performance of the soil.

Description

Technical Field

[0001] The present invention relates to the technical field of soil solidifiers, in particular to a nanomaterial-based anti-freeze cracking saline soil solidifier and a preparation method thereof. Background Art

[0002] Northeast my country is home to extensive saline soils, a region characterized by a unique climate and characterized by seasonally frozen ground. The unfavorable engineering properties of saline soils, such as frost heave and solution, pose significant challenges to local canal construction. In winter, water in the soil freezes, forming ice crystals that expand in volume. The solubility of salt in saline soil decreases at low temperatures, and crystallization further exacerbates soil expansion, leading to frost heave and deformation of canals. In spring, as temperatures rise and the permafrost thaws, saline soils solute due to water migration and salt dissolution. This series of problems has severely damaged numerous canals, compromising their structural integrity and reducing their water transport capacity. According to statistics, some canal projects in Northeast China require extensive repairs every three to five years due to saline soils. Maintenance costs are rising annually, significantly impacting the development of related industries such as agricultural irrigation and hydropower generation.

[0003] To address the adverse effects of saline soil on canal engineering, solidification technology has become an important tool. This technology adds specific cementitious materials to saline soil, modifying its physical and chemical properties, enhancing its strength and stability and suppressing phenomena like frost heave and dissolution. With technological advancements, saline soil improvement technologies are constantly emerging. For example, patent CN201710176059.X uses cement, blast furnace slag, and other materials to prepare a solidifying agent for addressing engineering problems associated with saline soil roadbed fills. Patent CN201410111644.8 utilizes a mixture of high-alumina cement and other materials to create a solidifying agent for hardening saline silt soil. These technologies have significantly improved the engineering performance of saline soil and possess significant practical value.

[0004] However, the unique seasonal freezing climate of Northeast China places higher demands on saline soil stabilizers. Existing stabilizers lack resistance to frost cracking and water penetration. Repeated freeze-thaw cycles can easily lead to microcracks within traditional stabilizers. These cracks expand over time, damaging the soil structure and significantly reducing its strength. Furthermore, their poor water penetration resistance allows moisture to easily penetrate the soil, exacerbating frost heave damage. Summary of the Invention

[0005] The purpose of the present invention is to provide a nanomaterial-based anti-freeze cracking saline soil solidifier and a preparation method thereof, so as to solve the technical problem that the solidifier proposed in the above background technology has insufficient anti-freeze cracking performance and water penetration resistance.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following components in parts by weight:

[0008] 70-87 parts of cement, 10-20 parts of silica fume, 1-3 parts of nano-silicon dioxide, 1-3 parts of basalt fiber, and 1-4 parts of polyacrylamide.

[0009] In the technical solution of the present invention, cement is used as the basic cementitious material, providing the basic strength framework of the solidified soil. The hydration products formed during the hydration process are interwoven with each other, initially building the overall structure of the soil. The silica fume used is an industrial waste produced by ferroalloys during the smelting of ferrosilicon and industrial silicon. It is not only low-cost but also has extremely fine particles. It can effectively fill the gaps between cement particles, reduce porosity, and increase the density of the solidified soil. It can also react with the Ca(OH)2 produced by cement hydration to form CSH gel, optimize the pore structure of the slurry, reduce the Ca(OH)2 content, refine the crystals and weaken their orientation, improve the strength and durability of the solidified soil, and thus enhance its resistance to frost cracking and water penetration. Basalt fiber has a reinforcing effect in the soil, significantly improving the compressive and frost cracking resistance of the solidified soil. Polyacrylamide is a white granular soil structure improver with good flocculation properties and is green and environmentally friendly. It reacts with cement to form a water film to promote cement hydration. The spatial network structure constructed in the soil plays a reinforcing role, involving microparticles and enhancing the soil's resistance to cracking.

[0010] The average particle size of nano-silica is between 10-100nm. After special surface activation treatment, the volcanic ash is highly active and can significantly accelerate the hydration process of cement, enrich the microstructure of the hydration product, further fill the tiny pores in the cement mixture, refine the overall mixture structure, improve the comprehensive performance of the material, and greatly enhance the water penetration resistance of the solidified soil.

[0011] Preferably, the cement is 425# cement.

[0012] Preferably, the nano-silicon dioxide is modified, comprising the following steps:

[0013] S1, adding nano-silica to toluene and uniformly dispersing it by ultrasonic oscillation to obtain a nano-silica suspension;

[0014] S2, adding polydimethylsiloxane to the nano-silica suspension, then adding dibutyltin dilaurate catalyst, stirring and dispersing uniformly, stirring and reacting under heating conditions, centrifuging, washing and drying to obtain hydrophobically modified nano-silica;

[0015] S3, mixing ethanol and water to obtain a mixed solution, adjusting the pH to be acidic, and then adding gamma-glycidoxypropyltrimethoxysilane into the mixed solution, and hydrolyzing by heating and stirring to obtain a gamma-glycidoxypropyltrimethoxysilane hydrolysate;

[0016] S4, adding hydrophobic modified nano-silica into the gamma-glycidoxypropyltrimethoxysilane hydrolysate, and reacting by heating and stirring, and then centrifuging, washing and drying to obtain the product.

[0017] In the technical scheme of the present application, the water permeability resistance of saline soil is improved from two aspects. On the one hand, the fine size structure of silica ash and nano-silica is used to fill the voids between cement particles, reduce porosity and improve the density of solidified soil. On the other hand, the hydrophobic polydimethylsiloxane is used to graft nano-silica to improve the hydrophobic properties of the surface of nano-silica, thereby forming a hydrophobic network inside the material to hinder the penetration of water. Through the synergistic effect of the two aspects, the saline soil has excellent water permeability resistance.

[0018] As described above, the hydrophobic polydimethylsiloxane is used to graft nano-silica to improve the hydrophobic properties of the surface of nano-silica. However, through experiments, it is found that grafting polydimethylsiloxane on nano-silica will cause the early strength of saline soil to decrease. Through in-depth research by the present application team, the reason for this problem is that polydimethylsiloxane has low surface energy and flexible molecular chain structure. In the early stage of solidification, the flexible molecular chain will weaken the chemical bond connection between the cement hydration products, interfere with the normal hydration and hardening process of cement, and the C-S-H gel formed by cement hydration is the key source of early strength of solidified soil. The presence of polydimethylsiloxane will hinder the ordered growth and crosslinking of the gel, so that the internal structure of the solidified soil is loose in the early stage, leading to slow growth of early strength, and further causing the early strength to decrease. To solve this problem, the present application team further treats the hydrophobic modified nano-silica by grafting gamma-glycidoxypropyltrimethoxysilane on the surface of the hydrophobic modified nano-silica. The surface of the grafted hydrophobic nano-silica has active groups such as epoxy groups. The epoxy group can undergo ring-opening reaction in an alkaline cement hydration environment. A large amount of calcium hydroxide is generated during cement hydration, making the system alkaline. Under alkaline conditions, the epoxy group undergoes ring-opening to form hydroxyl groups, further increasing the number of hydroxyl groups on the surface of nano-silica. These newly added hydroxyl groups can strongly chemisorb calcium ions generated during cement hydration, promoting the dispersion of cement particles and accelerating the hydration process of cement. At the same time, the hydroxyl groups can also participate in the formation process of cement hydration product C-S-H gel, react with silicate ions, etc., promote the growth and crosslinking of C-S-H gel, and thus improve the early strength of saline soil.

[0019] Preferably, in step S2, the mass ratio of nano-silica to polydimethylsiloxane is 5:0.5-2.

[0020] Preferably, in step S2, the heating temperature is 80-85° C., and the stirring reaction time is 10-12 h.

[0021] Preferably, in step S3, the pH is adjusted to 4-5.

[0022] Preferably, in step S3, the heating temperature is 50-60° C. and the hydrolysis time is 2-3 h.

[0023] Preferably, in step S4, the heating temperature is 65° C. and the reaction time is 12 h.

[0024] Preferably, in step S4, the mass ratio of hydrophobically modified nano-silica to γ-glycidyloxypropyltrimethoxysilane is 10:1-4.

[0025] To improve the early strength of saline soil, the present invention requires that a sufficient amount of γ-glycidoxypropyltrimethoxysilane be grafted onto the surface of the hydrophobically modified nanosilica. Therefore, the present invention controls the mass ratio of the hydrophobically modified nanosilica to γ-glycidoxypropyltrimethoxysilane to be less than 10 / 1. However, an excessive amount of γ-glycidoxypropyltrimethoxysilane can reduce the saline soil's resistance to water penetration. Therefore, the present invention also controls the mass ratio of the hydrophobically modified nanosilica to γ-glycidoxypropyltrimethoxysilane to be greater than 10 / 4.

[0026] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0027] Cement and basalt fiber are stirred and mixed evenly to obtain a premix; silica fume, nano silicon dioxide and polyacrylamide are added to the premix, and the mixture is stirred and mixed evenly to obtain a nanomaterial-based anti-freeze cracking saline soil curing agent.

[0028] Compared with the prior art, the present invention has the following beneficial effects:

[0029] 1. Silica fume and nano-silica effectively fill the gaps between cement particles, reducing porosity and increasing the density of the solidified soil. After being hydrophobically modified with polydimethylsiloxane, nano-silica forms a hydrophobic network within the material, further hindering water penetration. Simultaneously, the reinforcing effect of basalt fiber and the spatial network reinforcement structure created by polyacrylamide enhance the soil's resistance to cracking.

[0030] 2. The silica fume used in the curing agent is an industrial waste from ferroalloy smelting. It is widely available and inexpensive. Applying it to the curing agent realizes the resource utilization of industrial waste and reduces production costs.

[0031] 3. Addressing the issue of reduced early strength in saline soils caused by the grafting of polydimethylsiloxane onto nanosilica, this present invention successfully addresses this problem by grafting γ-glycidoxypropyltrimethoxysilane onto the surface of hydrophobically modified nanosilica. The grafted active groups ring-open in the alkaline environment of cement hydration to form hydroxyl groups, promoting cement particle dispersion and hydration, participating in CS-H gel formation, and improving early strength. Furthermore, the rational control of the grafting agent ratio ensures that the improved early strength is achieved without compromising the water penetration resistance of the curing agent, achieving a good balance between early strength and water penetration resistance in saline soils. DETAILED DESCRIPTION

[0032] The following is a clear and complete description of the technical solutions in the embodiments of the present invention. Obviously, the implementation regulations 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 are within the scope of protection of the present invention.

[0033] In a specific embodiment, the raw material specifications used in the present invention are as follows:

[0034] Cement, 425# cement, specific surface area 300-400m² / kg; silica fume, waste material from ferrosilicon and industrial silicon smelting, SiO2 content >85%, average particle size: 0.1-0.3μm, mainly amorphous silica, also containing small amounts of aluminum oxide (content 2-5%), calcium oxide (content 1-3%), magnesium oxide (content 0.5-2%), and iron oxide (content 0.5-3%); nano-silica, particle size 10-100nm; basalt fiber, length 3-6mm, diameter 9-13μm; polyacrylamide, ionic, molecular weight 10-15 million.

[0035] Example 1

[0036] A nanomaterial-based anti-freeze cracking saline soil solidifier, comprising the following components in parts by weight:

[0037] 85 parts of cement (425#), 18 parts of silica fume, 2.5 parts of nano-silicon dioxide, 2.5 parts of basalt fiber, and 3 parts of polyacrylamide.

[0038] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0039] The cement and basalt fiber were placed in a mixing container, and stirred at a speed of 500 r / min for 5 minutes using a powerful stirrer to uniformly mix the cement and basalt fiber to obtain a premix.

[0040] Silica fume, nano-silica and polyacrylamide were added to the premix, and the mixture was stirred at a speed of 800 r / min for 10 minutes using a powerful stirrer to ensure that all the components were fully mixed to obtain a nanomaterial-based anti-freeze cracking saline soil solidifier.

[0041] Example 2

[0042] A nanomaterial-based anti-freeze cracking saline soil solidifier, comprising the following components in parts by weight:

[0043] 85 parts of cement (425#), 18 parts of silica fume, 2.5 parts of modified nano-silica, 2.5 parts of basalt fiber, and 3 parts of polyacrylamide.

[0044] Preparation of modified nano-silica:

[0045] Step S1: Weigh 5 g of nano-silica and slowly add it to a beaker containing 500 mL of toluene. Place the beaker on an ultrasonic oscillator and ultrasonically oscillate for 30 minutes to uniformly disperse the nano-silica in the toluene to obtain a nano-silica suspension.

[0046] Step S2: Slowly add 1.5g of polydimethylsiloxane to the nanosilica suspension, followed by a small amount of dibutyltin dilaurate catalyst. Place the beaker on a magnetic stirrer and stir evenly. Then, place it in a constant temperature water bath at 83°C and stir for 10 hours. After the reaction is complete, transfer the reaction solution to a centrifuge tube and centrifuge it at 8000 rpm for 10 minutes. Discard the supernatant. Wash the precipitate three times with toluene, centrifuging it after each wash. Finally, place the precipitate in an oven and dry it at 60°C for 8 hours to obtain hydrophobically modified nanosilica.

[0047] Step S3: Pour 100 mL of ethanol and 10 mL of deionized water into a three-necked flask and mix thoroughly. Adjust the pH of the mixed solution to 4.5 with acetic acid. Then, slowly add 3 g of γ-glycidyloxypropyltrimethoxysilane to the mixed solution. Place the three-necked flask in a constant temperature water bath at 55°C and stir for 2.5 hours to hydrolyze the solution, yielding a γ-glycidyloxypropyltrimethoxysilane hydrolyzate.

[0048] Step S4: 10 g of hydrophobically modified nanosilica was added to the hydrolyzed solution of γ-glycidyloxypropyltrimethoxysilane. After stirring evenly on a magnetic stirrer, the mixture was placed in a constant temperature water bath at 65°C and stirred for 12 hours. After the reaction, the reaction solution was centrifuged, and the precipitate was washed three times with ethanol, centrifuging again after each wash. Finally, the precipitate was dried in an oven at 60°C for 8 hours to obtain the modified nanosilica.

[0049] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0050] The cement and basalt fiber were placed in a mixing container, and stirred at a speed of 500 r / min for 5 minutes using a powerful stirrer to uniformly mix the cement and basalt fiber to obtain a premix.

[0051] Silica fume, nano-silica and polyacrylamide were added to the premix, and the mixture was stirred at a speed of 800 r / min for 10 minutes using a powerful stirrer to ensure that all the components were fully mixed to obtain a nanomaterial-based anti-freeze cracking saline soil solidifier.

[0052] Example 3

[0053] A nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following components in parts by weight:

[0054] 80 parts of cement (425#), 15 parts of silica fume, 2 parts of modified nano-silica, 2 parts of basalt fiber, and 2.5 parts of polyacrylamide.

[0055] Preparation of modified nano-silica:

[0056] Step S1: Weigh 5 g of nano-silica and slowly add it to a beaker containing 500 mL of toluene. Place the beaker on an ultrasonic oscillator and ultrasonically oscillate for 30 minutes to uniformly disperse the nano-silica in the toluene to obtain a nano-silica suspension.

[0057] Step S2: Slowly add 1g of polydimethylsiloxane to the nanosilica suspension, followed by a small amount of dibutyltin dilaurate catalyst. Place the beaker on a magnetic stirrer and stir evenly. Then, place it in a constant temperature water bath at 83°C and stir for 11 hours. After the reaction is complete, transfer the reaction solution to a centrifuge tube and centrifuge it at 8000 rpm for 10 minutes. Discard the supernatant. Wash the precipitate three times with toluene, centrifuging it after each wash. Finally, place the precipitate in an oven and dry it at 60°C for 8 hours to obtain hydrophobically modified nanosilica.

[0058] Step S3: Pour 100 mL of ethanol and 10 mL of deionized water into a three-necked flask and mix thoroughly. Adjust the pH of the mixed solution to 4.5 with acetic acid. Then, slowly add 2 g of γ-glycidyloxypropyltrimethoxysilane to the mixed solution. Place the three-necked flask in a constant temperature water bath at 55°C and stir for 2.5 hours to hydrolyze the solution, yielding a γ-glycidyloxypropyltrimethoxysilane hydrolyzate.

[0059] Step S4: 10 g of hydrophobically modified nanosilica was added to the hydrolyzed solution of γ-glycidyloxypropyltrimethoxysilane. After stirring evenly on a magnetic stirrer, the mixture was placed in a constant temperature water bath at 65°C and stirred for 12 hours. After the reaction, the reaction solution was centrifuged, and the precipitate was washed three times with ethanol, centrifuging again after each wash. Finally, the precipitate was dried in an oven at 60°C for 8 hours to obtain the modified nanosilica.

[0060] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0061] The cement and basalt fiber were placed in a mixing container, and stirred at a speed of 500 r / min for 5 minutes using a powerful stirrer to uniformly mix the cement and basalt fiber to obtain a premix.

[0062] Silica fume, nano-silica and polyacrylamide were added to the premix, and the mixture was stirred at a speed of 800 r / min for 10 minutes using a powerful stirrer to ensure that all the components were fully mixed to obtain a nanomaterial-based anti-freeze cracking saline soil solidifier.

[0063] Example 4

[0064] A nanomaterial-based anti-freeze cracking saline soil solidifier, comprising the following components in parts by weight:

[0065] 87 parts of cement (425#), 20 parts of silica fume, 3 parts of modified nano-silica, 3 parts of basalt fiber, and 4 parts of polyacrylamide.

[0066] Preparation of modified nano-silica:

[0067] Step S1: Weigh 5 g of nano-silica and slowly add it to a beaker containing 500 mL of toluene. Place the beaker on an ultrasonic oscillator and ultrasonically oscillate for 30 minutes to uniformly disperse the nano-silica in the toluene to obtain a nano-silica suspension.

[0068] Step S2: Slowly add 2g of polydimethylsiloxane to the nanosilica suspension, followed by a small amount of dibutyltin dilaurate catalyst. Place the beaker on a magnetic stirrer and stir evenly. Then, place it in a constant temperature water bath at 85°C and stir for 12 hours. After the reaction is complete, transfer the reaction solution to a centrifuge tube and centrifuge it at 8000 rpm for 10 minutes. Discard the supernatant. Wash the precipitate three times with toluene, centrifuging again after each wash. Finally, place the precipitate in an oven and dry it at 60°C for 8 hours to obtain hydrophobically modified nanosilica.

[0069] Step S3: Pour 100 mL of ethanol and 10 mL of deionized water into a three-necked flask and mix thoroughly. Adjust the pH of the mixed solution to 5 with acetic acid. Then, slowly add 4 g of γ-glycidyloxypropyltrimethoxysilane to the mixed solution. Place the three-necked flask in a constant temperature water bath at 60°C and stir for 3 hours to hydrolyze the solution, obtaining a γ-glycidyloxypropyltrimethoxysilane hydrolyzate.

[0070] Step S4: 10 g of hydrophobically modified nanosilica was added to the hydrolyzed solution of γ-glycidyloxypropyltrimethoxysilane. After stirring evenly on a magnetic stirrer, the mixture was placed in a constant temperature water bath at 65°C and stirred for 12 hours. After the reaction, the reaction solution was centrifuged, and the precipitate was washed three times with ethanol, centrifuging again after each wash. Finally, the precipitate was dried in an oven at 60°C for 8 hours to obtain the modified nanosilica.

[0071] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0072] The cement and basalt fiber were placed in a mixing container, and stirred at a speed of 500 r / min for 5 minutes using a powerful stirrer to uniformly mix the cement and basalt fiber to obtain a premix.

[0073] Silica fume, nano-silica and polyacrylamide were added to the premix, and the mixture was stirred at a speed of 800 r / min for 10 minutes using a powerful stirrer to ensure that all the components were fully mixed to obtain a nanomaterial-based anti-freeze cracking saline soil solidifier.

[0074] Example 5

[0075] A nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following components in parts by weight:

[0076] 70 parts of cement (425#), 10 parts of silica fume, 1 part of modified nano-silica, 1 part of basalt fiber, and 1 part of polyacrylamide.

[0077] Preparation of modified nano-silica:

[0078] Step S1: Weigh 5 g of nano-silica and slowly add it to a beaker containing 500 mL of toluene. Place the beaker on an ultrasonic oscillator and ultrasonically oscillate for 30 minutes to uniformly disperse the nano-silica in the toluene to obtain a nano-silica suspension.

[0079] Step S2: Slowly add 0.5g of polydimethylsiloxane to the nanosilica suspension, followed by a small amount of dibutyltin dilaurate catalyst. Place the beaker on a magnetic stirrer and stir evenly. Then, place it in a constant temperature water bath at 80°C and stir for 10 hours. After the reaction is complete, transfer the reaction solution to a centrifuge tube and centrifuge it at 8000 rpm for 10 minutes. Discard the supernatant. Wash the precipitate three times with toluene, centrifuging it after each wash. Finally, place the precipitate in an oven and dry it at 60°C for 8 hours to obtain hydrophobically modified nanosilica.

[0080] Step S3: Pour 100 mL of ethanol and 10 mL of deionized water into a three-necked flask and mix thoroughly. Adjust the pH of the mixed solution to 4 with acetic acid. Then, slowly add 1 g of γ-glycidyloxypropyltrimethoxysilane to the mixed solution. Place the three-necked flask in a constant temperature water bath at 50°C and stir for 2 hours to hydrolyze the solution, obtaining a γ-glycidyloxypropyltrimethoxysilane hydrolyzate.

[0081] Step S4: 10 g of hydrophobically modified nanosilica was added to the hydrolyzed solution of γ-glycidyloxypropyltrimethoxysilane. After stirring evenly on a magnetic stirrer, the mixture was placed in a constant temperature water bath at 65°C and stirred for 12 hours. After the reaction, the reaction solution was centrifuged, and the precipitate was washed three times with ethanol, centrifuging again after each wash. Finally, the precipitate was dried in an oven at 60°C for 8 hours to obtain the modified nanosilica.

[0082] A method for preparing a nanomaterial-based anti-freeze cracking saline soil solidifier comprises the following steps:

[0083] The cement and basalt fiber were placed in a mixing container, and stirred at a speed of 500 r / min for 5 minutes using a powerful stirrer to uniformly mix the cement and basalt fiber to obtain a premix.

[0084] Silica fume, nano-silica and polyacrylamide were added to the premix, and the mixture was stirred at a speed of 800 r / min for 10 minutes using a powerful stirrer to ensure that all the components were fully mixed to obtain a nanomaterial-based anti-freeze cracking saline soil solidifier.

[0085] Comparative Example 1

[0086] The difference between Comparative Example 1 and Example 1 is that nano-silicon oxide is not added to the curing agent, and the other steps are the same.

[0087] Comparative Example 2

[0088] The difference between Comparative Example 2 and Example 2 is that γ-glycidyloxypropyltrimethoxysilane is not used for grafting treatment of hydrophobically modified nano-silica, and the other steps are the same.

[0089] Comparative Example 3

[0090] The difference between Comparative Example 3 and Example 4 is that the mass ratio of hydrophobically modified nano-silica to γ-glycidyloxypropyltrimethoxysilane is 10:5, and the other steps are the same.

[0091] Comparative Example 4

[0092] The difference between Comparative Example 4 and Example 4 is that the mass ratio of hydrophobically modified nano-silica to γ-glycidyloxypropyltrimethoxysilane is 10:6, and the other steps are the same.

[0093] Performance testing:

[0094] 1. Anti-freeze cracking performance test:

[0095] Frost crack resistance was tested using a slow freezing method. According to the "Standard for Test Methods for Long-term Performance and Durability of Ordinary Concrete" (GB / T 50082-2009), the curing agents prepared in each example and comparative example were uniformly mixed with saline soil at a mass ratio of 15% to form cubic specimens measuring 100 mm × 100 mm × 100 mm. Ten specimens were prepared for each group. After 28 days of standard curing, the specimens were placed in a freezer and cooled to -20°C at a rate of 2°C / h. The specimens were held at this temperature for 4 hours. They were then removed from the freezer and placed in 20°C water, where they were thawed at a rate of 3°C / h and held for 4 hours. This constituted one freeze-thaw cycle. After seven freeze-thaw cycles, the compressive strength of the specimens was measured using a pressure testing machine. The ratio of the compressive strength after the freeze-thaw cycle to the compressive strength before the freeze-thaw cycle was calculated. A higher ratio indicates better frost crack resistance for the curing agent. The results are shown in Table 1.

[0096] 2. Water penetration resistance test:

[0097] The water permeability resistance test was performed according to the water penetration height method in the Standard for Testing Durability and Long-term Performance of Ordinary Concrete (GB / T 50082-2009). The solidifying agent prepared in each example and the comparative example was mixed with the saline soil at a mass ratio of 20% to prepare a circular truncated cone-shaped test piece with a diameter of 175 mm and a height of 150 mm. Six test pieces were prepared for each group. After standard curing for 28 days, the test pieces were installed on a concrete permeameter, a water pressure of 0.8 MPa was applied, and after 24 hours of constant pressure, the test pieces were removed and split along the longitudinal section. The water penetration height of the inner surface of the test piece was measured with a steel ruler to an accuracy of 1 mm. The average value of the water penetration height of the six test pieces was calculated. The smaller the water penetration height, the better the water permeability resistance of the solidifying agent. The calculation results are shown in Table 1.

[0098] 3. Early strength test:

[0099] According to the unconfined compressive strength test method in the Mixing Proportion Design Specification for Cement Soil (JGJ / T 233-2011), the solidifying agent prepared in each example and the comparative example was mixed with the saline soil at a mass ratio of 10% to prepare a cylindrical test piece with a diameter of 50 mm and a height of 100 mm. Six test pieces were prepared for each group. The test pieces were cured under standard curing conditions of a temperature of 20±2℃ and a relative humidity of greater than 95% for 1 day and 3 days, respectively. Then, the compressive strength of the test pieces was measured using an unconfined pressure testing machine. The test results are shown in Table 1.

[0100] Table 1:

[0101]

[0102] Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features, and any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A nanomaterial-based anti-freeze cracking saline soil solidifier, characterized in that: Comprise the following components by weight: 70-87 parts of cement, 10-20 parts of silica fume, 1-3 parts of nano-silicon dioxide, 1-3 parts of basalt fiber, 1-4 parts of polyacrylamide; The nano-silicon dioxide is modified, comprising the following steps: S1, adding nano-silica to toluene and uniformly dispersing it by ultrasonic oscillation to obtain a nano-silica suspension; S2, adding polydimethylsiloxane to the nano-silica suspension, then adding dibutyltin dilaurate catalyst, stirring and dispersing uniformly, stirring and reacting under heating conditions, centrifuging, washing and drying to obtain hydrophobically modified nano-silica; S3, mixing ethanol and water to obtain a mixed solution, adjusting the pH to acidic, then adding γ-glycidyloxypropyltrimethoxysilane to the mixed solution, heating and stirring to hydrolyze, to obtain a γ-glycidyloxypropyltrimethoxysilane hydrolyzate; S4. Adding hydrophobically modified nano-silica to the hydrolyzed solution of γ-glycidyloxypropyltrimethoxysilane, heating and stirring to react, and then centrifuging, washing and drying to obtain the product.

2. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: The cement is 425# cement.

3. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: In the step S2, the mass ratio of nano-silica to polydimethylsiloxane is 5:0.5-2.

4. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: In step S2, the heating temperature is 80-85° C., and the stirring reaction time is 10-12 h.

5. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: In step S3, the pH is adjusted to 4-5.

6. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: In step S3, the heating temperature is 50-60° C., and the hydrolysis time is 2-3 hours.

7. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 1, characterized in that: In step S4, the heating temperature is 65° C. and the reaction time is 12 h.

8. The nanomaterial-based anti-freeze cracking saline soil solidifier according to claim 7, characterized in that: In the step S4, the mass ratio of the hydrophobically modified nano-silica to γ-glycidyloxypropyltrimethoxysilane is 10:1-4.

9. A method for preparing the nanomaterial-based anti-freeze cracking saline soil solidifying agent according to any one of claims 1 to 8, characterized in that: The following steps are involved: Cement and basalt fiber are stirred and mixed evenly to obtain a premix; silica fume, nano silicon dioxide and polyacrylamide are added to the premix, and the mixture is stirred and mixed evenly to obtain a nanomaterial-based anti-freeze cracking saline soil curing agent.

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