Low-carbon soft soil curing agent as well as preparation method and application thereof

Abstract

The invention discloses a low-carbon soft soil curing agent as well as a preparation method and application thereof, and belongs to the technical field of soft soil curing. The low-carbon soft soil curing agent mainly comprises the following raw material components in parts by mass: 200-300 parts of cement, 100-200 parts of fly ash, 200 parts of mineral powder, 200 parts of metallurgical steel slag, 100-200 parts of gypsum, 10-30 parts of modified waste polyacrylonitrile fibers and 30-50 parts of a water-resistant acrylate copolymer, wherein the modified waste polyacrylonitrile fiber is obtained by aminating waste polyacrylonitrile, reacting the aminated waste polyacrylonitrile with 2-[dodecylthio (thiocarbonyl) thio]-2-methyl propionic acid, and then grafting 1-vinyl imidazole through RAFT (Reversible Addition-Fragmentation Chain Transfer) polymerization reaction; the water-resistant acrylate copolymer is obtained by carrying out copolymerization on butyl acrylate, styrene, glycidyl methacrylate, vinyl triisopropyl silane, 3-(methacryloyloxy) propyl trimethoxy silane, aluminum acrylate and 1, 3-propenylsultone, and the water-resistant acrylate copolymer is obtained by carrying out copolymerization on the butyl acrylate, the styrene, the glycidyl methacrylate, the vinyl triisopropyl silane, the 3-(methacryloyloxy) propyl trimethoxy silane, the aluminum acrylate and the 1, 3-propenylsultone; the doping amount of the prepared low-carbon soft soil curing agent is 7-25% of the mass of soft soil.

Description

Technical Field

[0001] The invention relates to a low-carbon soft soil solidifying agent and a preparation method and application thereof. Background Art

[0002] In civil engineering construction, soft soil treatment is a critical and challenging issue. Soft soil typically has high water content, high compressibility, and low strength. This necessitates reinforcement of the soft soil to improve its bearing capacity and stability when constructing on it. Soil stabilizers, as an effective soft soil reinforcement material, are widely used in soft soil treatment projects.

[0003] Traditional soil stabilizers mainly include ordinary Portland cement, blast furnace slag cement, low-carbon solid waste cement, lime, etc. In actual engineering applications, it is necessary to carefully select the appropriate soil stabilizer based on multiple requirements such as the strength, durability, impermeability, and environmental impact of the stabilized soil structure.

[0004] However, traditional soil solidifiers have certain limitations in their application. Different types of soil solidified with a solidifier produce different hydration products. This is because the soil structure and chemical properties vary, and soil particles can participate in or affect the hydration and hardening reaction of the solidifier. Moreover, for some special engineering situations, traditional solidifiers are difficult to meet the project requirements. For example, when a foundation reinforcement mixing pile project encounters a liquefied sand layer, a full water environment, or a water pressure difference in groundwater flow, the cement-soil mixing pile often fails to form or has poor pile formation.

[0005] Admixtures play a crucial role in soil consolidation projects. They can adjust the fluidity, durability, workability, and setting time of the soil being consolidated. These properties allow for customized curing agent designs. By incorporating certain soil components into the crosslinking process, the soil is formed into a novel crosslinked network structure. Furthermore, functional admixtures can be added to tailor the engineering properties of the curing agent based on the specific characteristics of the soil or silt being consolidated. For example, during winter construction in northern China, adding antifreeze and early-strengthening admixtures can enhance the frost resistance of the consolidated soil, meeting the requirements of winter construction projects. When the moisture content of soil silt is high, the use of fast-absorbing, rapid-setting, and accelerating admixtures can rapidly reduce the silt's moisture content and rapidly transition the consolidated soil from a fluid state to a hard-plastic state, thereby stabilizing the consolidated mass.

[0006] In addition, the disposal of waste polyacrylonitrile fiber is also a practical issue. Currently, there is a large amount of waste polyacrylonitrile fiber accumulated. If it can be properly utilized, it will not only solve the waste disposal problem, but also bring benefits to the improvement of material performance.

[0007] In order to solve the above problems, the applicant has developed a low-carbon soft soil solidifier and its preparation method; this solidifier can achieve the requirements of good consolidation effect of the same-age mixing pile solidified soil, fast molding, high test block strength, good impermeability, good water stability, and good anti-freeze-thaw effect, so as to meet the needs of soft soil treatment in different engineering environments, while achieving effective resource utilization and environmental protection. Summary of the Invention

[0008] The purpose of the present invention is to provide a low-carbon soft soil solidifying agent and a preparation method and application thereof, so as to solve the technical problems mentioned in the above background technology.

[0009] The technical solution for achieving the purpose of the present invention is:

[0010] In the first aspect, the present invention provides a low-carbon soft soil solidifying agent, the raw material components of which, calculated by mass fraction, mainly include 200-300 parts by mass of cement, 100-200 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical slag, 100-200 parts by mass of gypsum, 10-30 parts by mass of modified waste polyacrylonitrile fiber, and 30-50 parts by mass of water-resistant acrylic copolymer.

[0011] Furthermore, the modified waste polyacrylonitrile fiber is obtained by aminating waste polyacrylonitrile fiber and reacting it with 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, and then grafting 1-vinylimidazole through RAFT polymerization.

[0012] Furthermore, the water-resistant acrylate copolymer is obtained by copolymerizing butyl acrylate, styrene, glycidyl methacrylate, vinyl triisopropyl silane, 3-(methacryloyloxy)propyl trimethoxy silane, aluminum acrylate, and 1,3-propylene sultone.

[0013] In a second aspect, the present invention provides a method for preparing a low-carbon soft soil solidifying agent, comprising the following preparation steps:

[0014] (1) Weighing and mixing the raw materials according to the weight fractions of each raw material component described in the first aspect;

[0015] (2) the modified waste polyacrylonitrile fiber, the water-resistant acrylic copolymer, and 500-700 parts by mass of acetonitrile weighed in step (1) were stirred and uniformly dispersed, followed by reaction at 80° C. for 11-13 hours, and the acetonitrile was removed by rotary evaporation to obtain a mixture A;

[0016] (3) Mixing the cement, fly ash, mineral powder gypsum, and metallurgical slag weighed in step (1) to obtain a mixture B;

[0017] (4) Mixing material A and material B to obtain a low-carbon soft soil solidifying agent.

[0018] Furthermore, the preparation steps of the modified waste polyacrylonitrile fiber are as follows:

[0019] 0.02-0.04 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.03-0.05 parts by mass of azobisisobutyronitrile, 0.04-0.06 parts by mass of 1-vinylimidazole, 0.06-0.08 parts by mass of butyl methacrylate and 5.5-6.5 parts by mass of methanol are mixed and ultrasonically treated for 4-6 minutes. Then, 0.1 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid-modified polyacrylonitrile fiber is immersed in it, and ultrasonic treatment is continued for 4-6 minutes. Then, the mixture is reacted at 68-72°C under ice bath and nitrogen protection for 23-25 ​​hours. After the reaction is completed, the fiber is washed with methanol and acetone 2-4 times and dried at 60°C for 9-11 hours to obtain modified waste polyacrylonitrile fiber.

[0020] Furthermore, the preparation steps of the 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber are as follows: 8 to 9 parts by mass of ethylenediamine and 5 parts by mass of deionized water are added to a reactor and preheated to 115 to 125° C., 1 part by mass of dry waste polyacrylonitrile fiber is added and stirred for 4 hours, the fiber is filtered and collected, and the fiber is washed with deionized water at 70 to 80° C. until the pH value of the washing liquid reaches 7, and then vacuum dried at 58 to 62° C. for 8 to 10 hours to obtain aminated polyacrylonitrile fiber; 0.15 parts by mass of aminated polyacrylonitrile fiber is immersed in 4 to 5 parts by mass of acetonitrile solution, then add 0.25 to 0.35 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.055 to 0.065 parts by mass of 4-dimethylaminopyridine and 0.36 to 0.4 parts by mass of N, N'-dicyclohexylcarbodiimide, stir at room temperature for 1.5 to 2.5 hours, then heat to 35 to 45 ° C, stir and react for 9 to 11 hours, then wash with acetonitrile and vacuum dry at 58 to 62 ° C overnight to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber.

[0021] Furthermore, the methyl acrylate content in the waste polyacrylonitrile fiber is 5-15%.

[0022] Furthermore, the length of the waste polyacrylonitrile fiber is 5 to 10 mm.

[0023] The reaction process of modifying waste polyacrylonitrile fiber is as follows:

[0024]

[0025] Furthermore, the preparation steps of the water-resistant acrylate copolymer are as follows: butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone are mixed to obtain 23 to 24 parts by mass of a mixed monomer, and then the mixed monomer is added dropwise to 60 to 70 parts by mass of deionized water containing 0.35 to 0.37 parts by mass of an emulsifier and 0.67 to 0.68 parts by mass of a pH adjuster, and then dispersed for 5 minutes using a homogenizer to emulsify it to obtain a stable pre-emulsion; 1 / 3 of the pre-emulsion and deionized water are added to a reactor, stirred and heated to 55 to 65°C, 1 / 3 of an initiator ammonium persulfate aqueous solution is added, and the stirring is continued and the temperature is raised to 80 to 90°C, and the mixture is heated to 40°C. During the warming period, when the temperature reaches 75-78° C., the remaining pre-emulsion and the ammonium persulfate aqueous solution are added, wherein the ammonium persulfate aqueous solution is dripped after the pre-emulsion, and the dripping time is 2-3 hours. When the total amount of the remaining pre-emulsion added exceeds 2 / 3, 0.4-0.5 parts by weight of vinyltriisopropylsilane and 0.4-0.5 parts by weight of 3-(methacryloyloxy)propyltrimethoxysilane are started to be dripped, and the initiator aqueous solution is dripped after the organosiloxane. After the initiator aqueous solution is added, the temperature is raised to 85-95° C. and the reaction is continued for 25-35 minutes, then the temperature is lowered to 65-75° C. and kept warm for 25-35 minutes, cooled, filtered, and discharged to obtain a water-resistant acrylate copolymer.

[0026] The reaction process of water-resistant acrylate copolymer is as follows:

[0027]

[0028] Furthermore, the mass ratio of butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone is 50:2-4:5-7:11-13:2-4; the DNS-B6 and ANPEO in the emulsifier are 10 The mass ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 2:1; the mass volume ratio of ammonium persulfate to deionized water is 9 to 11:100, and the amount of ammonium persulfate aqueous solution added is 0.08 to 0.09 parts by mass.

[0029] In a third aspect, a method for using the low-carbon soft soil curing agent according to the first aspect is provided, wherein the curing agent is added to the soft soil to be cured and mixed evenly, wherein the amount of the curing agent added is 7% to 25% of the mass of the soft soil.

[0030] By adopting the above technical solution, the present invention has the following beneficial effects:

[0031] (1) The low-carbon soft soil solidifying agent of the present invention mainly comprises, by mass fraction, 200-300 parts by mass of cement, 100-200 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical steel slag, 100-200 parts by mass of gypsum, 10-30 parts by mass of modified waste polyacrylonitrile fiber, and 30-50 parts by mass of water-resistant acrylic copolymer. By adopting the water-resistant acrylic copolymer that does not disperse underwater for modification, the low-carbon soft soil solidifying agent has good consolidation effect, fast forming, high test block strength, good impermeability, good water stability, and good freeze-thaw resistance effect compared with the solidified soil of the same-age mixing pile.

[0032] (2) The present invention introduces modified waste polyacrylonitrile fibers, which can significantly improve the road performance of solidified soil through a physical-chemical synergistic mechanism: polyacrylonitrile fibers bridge soil microcracks through a three-dimensional network structure, forming friction bites and mechanical interlocking effects with soil particles, effectively inhibiting the expansion of through-cracks; furthermore, polyacrylonitrile fibers absorb energy and evenly disperse stress when the soil is subjected to stress, so that the material failure mode changes from brittle to plastic, thereby improving toughness; at the same time, the fiber network blocks the moisture migration path and restrains frost heave deformation, thereby improving water stability and frost resistance, and by limiting the shrinkage displacement of soil particles, both the dry shrinkage coefficient and the temperature shrinkage coefficient are reduced, which can alleviate the risk of base cracking.

[0033] (3) The water-resistant acrylic copolymer of the present invention is obtained by copolymerization of butyl acrylate, styrene, glycidyl methacrylate, vinyl triisopropyl silane, 3-(methacryloyloxy)propyl trimethoxy silane, aluminum acrylate, and 1,3-propylene sultone. The water resistance of the acrylic copolymer is enhanced by introducing polystyrene. The polymer main chain forms a high-strength cross-linked network, which wraps soil particles through physical entanglement, fills pores, and enhances the density and compressive strength of the soil. The active monomer glycidyl methacrylate undergoes a cross-linking reaction with the hydroxyl group in the soil particles or the carboxyl group of humic acid through the epoxy group to form a chemical bond, which further improves the strength. The hydrophobic siloxane segments of triisopropylsilane and 3-(methacryloyloxy)propyltrimethoxysilane organosilicon monomers form a low surface energy barrier on the soil surface, significantly increasing the contact angle, preventing water penetration, and improving scour resistance; aluminum acrylate can synergistically enhance the soil surface by interacting with cement, fly ash, mineral powder, metallurgical slag, and gypsum to generate gel substances such as hydrated calcium silicate, hydrated calcium aluminate, and sodium aluminosilicate hydrate through hydration reactions. The generated gelling components cross-complex to form a spatial network structure, strengthening the connection between soil particles, filling the gaps inside the soil, and at the same time converting the free water in the soil into bound water, changing the soil properties, and promoting the formation of a stable and dense soil structure.

[0034] (4) The present invention premixes the modified waste polyacrylonitrile fiber with the water-resistant acrylate copolymer, and the imidazole on the modified waste polyacrylonitrile fiber reacts with the sultone of the water-resistant acrylate copolymer to form a sulfonate and an imidazole salt. The double layer is stabilized by ion exchange, which reduces soil water absorption and swelling, further improving the water stability and freeze-thaw resistance of the solidified soil.

[0035] Part of the reaction process is as follows:

[0036] DETAILED DESCRIPTION

[0037] In order to better understand the above technical solution, the above technical solution will be described in detail below in conjunction with specific implementation methods.

[0038] Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative work shall fall within the scope of protection of the present invention.

[0039] The following examples are only used to more clearly illustrate the technical solutions of the present invention and are not intended to limit the scope of protection of the present invention.

[0040] The raw material parameters of the examples and comparative examples of the present invention are as follows:

[0041] The cement used is PO 42.5 grade ordinary Portland cement with a loss on ignition of 4.16%, sulfur trioxide 2.87%, magnesium oxide 3.14%, chloride ion 0.016%, initial setting time 190min, final setting time 260min, 3d compressive strength 28.1MPa, flexural strength 5.8MPa, 28d compressive strength 52.4MPa, flexural strength 8.9MPa.

[0042] Fly ash composition: 51.14% silicon dioxide, 26.65% aluminum oxide, 10.62% iron oxide, 5.36% calcium oxide, and 2.29% sulfur trioxide.

[0043] The specific surface area of ​​metallurgical steel slag is 450~580m 2 / kg, the specific surface area of ​​the mineral powder is 500-600m 2 / kg.

[0044] Sodium bicarbonate was used as the pH adjuster.

[0045] (Example 1)

[0046] A method for preparing a low-carbon soft soil solidifying agent comprises the following steps:

[0047] (1) Weigh and prepare the following ingredients according to the mass fraction of each raw material component: 200 parts by mass of cement, 200 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical slag, 100 parts by mass of gypsum, 10 parts by mass of modified waste polyacrylonitrile fiber, and 50 parts by mass of water-resistant acrylic copolymer;

[0048] (2) The modified waste polyacrylonitrile fiber, the water-resistant acrylic copolymer, and 500 parts by mass of acetonitrile weighed in step (1) were stirred and dispersed uniformly, followed by reaction at 80° C. for 11 hours. After the reaction was completed, the acetonitrile was removed by rotary evaporation to obtain a mixture A;

[0049] (3) Mixing the cement, fly ash, mineral powder gypsum, and metallurgical slag weighed in step (1) to obtain a mixture B;

[0050] (4) Mixing material A and material B to obtain a low-carbon soft soil solidifying agent.

[0051] The preparation steps of the modified waste polyacrylonitrile fiber are as follows:

[0052] 0.02 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.03 parts by mass of azobisisobutyronitrile, 0.04 parts by mass of 1-vinylimidazole, 0.06 parts by mass of butyl methacrylate and 5.5 parts by mass of methanol were mixed and ultrasonically treated for 4 minutes. Then, 0.1 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid-modified polyacrylonitrile fiber was immersed in it and ultrasonically treated for 4 minutes. Then, the fiber was reacted at 68°C for 23 hours under ice bath and nitrogen protection. After the reaction was completed, the fiber was washed twice with methanol and acetone and dried at 60°C for 9 hours to obtain modified waste polyacrylonitrile fiber.

[0053] The preparation steps of the 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber are as follows: 8 parts by mass of ethylenediamine and 5 parts by mass of deionized water are added to a reactor and preheated to 115° C., 1 part by mass of dry waste polyacrylonitrile fiber is added, stirred and reacted for 4 hours, filtered and collected, and the fiber is washed with deionized water at 70° C. until the pH value of the washing solution is 7, and then vacuum dried at 58° C. for 8 hours to obtain aminated polyacrylonitrile fiber; 0.15 parts by mass of aminated polypropylene are added; The nitrile fiber was immersed in 4 parts by mass of acetonitrile solution, and then 0.25 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.055 parts by mass of 4-dimethylaminopyridine and 0.36 parts by mass of N,N'-dicyclohexylcarbodiimide were added. After stirring at room temperature for 1.5 hours, the temperature was raised to 35°C and stirred for 9 hours. The reaction was then washed with acetonitrile and vacuum dried at 58°C overnight to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber.

[0054] The length of the waste polyacrylonitrile fiber is 5 mm.

[0055] The preparation steps of the water-resistant acrylate copolymer are as follows: butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone are mixed to obtain 23 parts by mass of a mixed monomer, and the mixed monomer is then added dropwise to 60 parts by mass of deionized water containing 0.35 parts by mass of an emulsifier and 0.67 parts by mass of a pH adjuster, and then dispersed for 5 minutes using a homogenizer to emulsify the mixture to obtain a stable pre-emulsion; 1 / 3 of the pre-emulsion and 15 parts by mass of deionized water are added to a reactor, stirred and heated to 55° C., 1 / 3 of an initiator ammonium persulfate aqueous solution is added, and the mixture is continued to be stirred and heated to 80° C. During the heating period, when the temperature reaches 75° C., the remaining pre-emulsion and the ammonium persulfate aqueous solution are added, wherein the ammonium persulfate aqueous solution is dripped after the pre-emulsion, and the dripping time is 2 hours. When the total amount of the remaining pre-emulsion added exceeds 2 / 3, 0.4 parts by mass of vinyl triisopropyl silane and 0.4 parts by mass of 3-(methacryloyloxy)propyl trimethoxy silane are started to be dripped, and the initiator aqueous solution is dripped after the organosiloxane; after the initiator aqueous solution is added, the temperature is raised to 85° C. and the reaction is continued for 25 minutes, then the temperature is lowered to 65° C. and kept warm for 25 minutes, cooled, filtered, and discharged to obtain a water-resistant acrylate copolymer.

[0056] The mass ratio of butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone is 50:2:5:11:2; the DNS-B6 and ANPEO in the emulsifier are 10 The mass ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 2:1; the mass volume ratio of ammonium persulfate to deionized water is 9:100, and the amount of ammonium persulfate aqueous solution added in parts by mass is 0.08 parts by mass.

[0057] When in use, add the curing agent to the soft soil to be cured and mix evenly. The amount of curing agent added is 15% of the mass of the soft soil.

[0058] (Example 2)

[0059] A method for preparing a low-carbon soft soil solidifying agent comprises the following steps:

[0060] (1) Weighing and mixing the raw materials according to the mass fraction of each component: 250 parts by mass of cement, 150 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical slag, 150 parts by mass of gypsum, 20 parts by mass of modified waste polyacrylonitrile fiber, and 40 parts by mass of water-resistant acrylic copolymer;

[0061] (2) The modified waste polyacrylonitrile fiber, the water-resistant acrylic copolymer, and 600 parts by mass of acetonitrile weighed in step (1) were stirred and dispersed uniformly, followed by reaction at 80° C. for 12 h. After the reaction was completed, the acetonitrile was removed by rotary evaporation to obtain a mixture A;

[0062] (3) Mixing the cement, fly ash, mineral powder gypsum, and metallurgical slag weighed in step (1) to obtain a mixture B;

[0063] (4) Mixing material A and material B to obtain a low-carbon soft soil solidifying agent.

[0064] The preparation steps of the modified waste polyacrylonitrile fiber are as follows:

[0065] 0.03 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.04 parts by mass of azobisisobutyronitrile, 0.05 parts by mass of 1-vinylimidazole, 0.07 parts by mass of butyl methacrylate and 6 parts by mass of methanol were mixed and ultrasonically treated for 5 minutes. Then, 0.1 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid-modified polyacrylonitrile fiber was immersed in it and ultrasonically treated for 5 minutes. Then, the fiber was reacted at 70°C for 24 hours under ice bath and nitrogen protection. After the reaction was completed, the fiber was washed three times with methanol and acetone and dried at 60°C for 10 hours to obtain modified waste polyacrylonitrile fiber.

[0066] The preparation steps of the 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber are as follows: 8.5 parts by mass of ethylenediamine and 5 parts by mass of deionized water are added into a reactor and preheated to 120° C., 1 part by mass of dry waste polyacrylonitrile fiber is added and stirred for reaction for 4 hours, the fiber is filtered and collected, the fiber is washed with deionized water at 75° C. until the pH value of the washing liquid is 7, and then vacuum dried at 60° C. for 9 hours to obtain aminated polyacrylonitrile fiber; 0.15 parts by mass of aminated polyacrylonitrile is added and stirred for reaction for 4 hours. Acrylonitrile fiber was immersed in 4.5 parts by mass of acetonitrile solution, and then 0.3 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.06 parts by mass of 4-dimethylaminopyridine and 0.38 parts by mass of N,N'-dicyclohexylcarbodiimide were added. After stirring at room temperature for 2 hours, the temperature was raised to 40°C and stirred for 10 hours. The reaction was then washed with acetonitrile and vacuum dried at 60°C overnight to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber.

[0067] The length of the waste polyacrylonitrile fiber is 8 mm.

[0068] The preparation steps of the water-resistant acrylate copolymer are as follows: butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone are mixed to obtain 23.5 parts by mass of a mixed monomer, and the mixed monomer is then added dropwise to 65 parts by mass of deionized water containing 0.36 parts by mass of an emulsifier and 0.675 parts by mass of a pH adjuster, and then dispersed for 5 minutes using a homogenizer to emulsify the mixture to obtain a stable pre-emulsion; 1 / 3 of the pre-emulsion and 15 parts by mass of deionized water are added to a reactor, stirred and heated to 60° C., 1 / 3 of an initiator ammonium persulfate aqueous solution is added, and the mixture is continued to be stirred and heated to 85° C. During the heating period, when the temperature reaches 75° C., the remaining pre-emulsion and the ammonium persulfate aqueous solution are added, wherein the ammonium persulfate aqueous solution is dripped after the pre-emulsion, and the dripping time is 2.5 hours. When the total amount of the remaining pre-emulsion added exceeds 2 / 3, 0.45 parts by mass of vinyl triisopropyl silane and 0.45 parts by mass of 3-(methacryloyloxy)propyl trimethoxy silane are started to be dripped, and the initiator aqueous solution is dripped after the organosiloxane; after the initiator aqueous solution is added, the temperature is raised to 90° C. and the reaction is continued for 30 minutes, then the temperature is lowered to 70° C. and kept warm for 30 minutes, cooled, filtered, and discharged to obtain a water-resistant acrylate copolymer.

[0069] The mass ratio of butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone is 50:3:6:12:3; the DNS-B6 and ANPEO in the emulsifier are 10 The mass ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 2:1; the mass volume ratio of ammonium persulfate to deionized water is 10:100, and the amount of ammonium persulfate aqueous solution added in parts by mass is 0.085 parts by mass.

[0070] When in use, add the curing agent to the soft soil to be cured and mix evenly. The amount of curing agent added is 15% of the mass of the soft soil.

[0071] (Example 3)

[0072] A method for preparing a low-carbon soft soil solidifying agent comprises the following steps:

[0073] (1) Weighing and mixing the raw materials according to the mass fraction of each component: 300 parts by mass of cement, 100 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical slag, 200 parts by mass of gypsum, 30 parts by mass of modified waste polyacrylonitrile fiber, and 30 parts by mass of water-resistant acrylic copolymer;

[0074] (2) The modified waste polyacrylonitrile fiber, the water-resistant acrylic copolymer, and 700 parts by mass of acetonitrile weighed in step (1) were stirred and dispersed uniformly, followed by reaction at 80° C. for 13 h. After the reaction was completed, the acetonitrile was removed by rotary evaporation to obtain a mixture A;

[0075] (3) Mixing the cement, fly ash, mineral powder gypsum, and metallurgical slag weighed in step (1) to obtain a mixture B;

[0076] (4) Mixing material A and material B to obtain a low-carbon soft soil solidifying agent.

[0077] The preparation steps of the modified waste polyacrylonitrile fiber are as follows:

[0078] 0.04 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.05 parts by mass of azobisisobutyronitrile, 0.06 parts by mass of 1-vinylimidazole, 0.08 parts by mass of butyl methacrylate and 6.5 parts by mass of methanol were mixed and ultrasonically treated for 6 minutes. Then, 0.1 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid-modified polyacrylonitrile fiber was immersed in it and ultrasonically treated for 6 minutes. Then, the fiber was reacted at 72°C under ice bath and nitrogen protection for 25 hours. After the reaction was completed, the fiber was washed 4 times with methanol and acetone and dried at 60°C for 11 hours to obtain modified waste polyacrylonitrile fiber.

[0079] The preparation steps of the 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber are as follows: 9 parts by mass of ethylenediamine and 5 parts by mass of deionized water are added into a reactor and preheated to 125° C., 1 part by mass of dry waste polyacrylonitrile fiber is added and stirred for reaction for 4 hours, the fiber is filtered and collected, the fiber is washed with deionized water at 80° C. until the pH value of the washing liquid is 7, and then vacuum dried at 62° C. for 10 hours to obtain aminated polyacrylonitrile fiber; 0.15 parts by mass of aminated polyacrylonitrile is added and the mixture is stirred for reaction for 4 hours. The polyacrylonitrile fiber was immersed in 5 parts by mass of acetonitrile solution, and then 0.35 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.065 parts by mass of 4-dimethylaminopyridine and 0.4 parts by mass of N,N'-dicyclohexylcarbodiimide were added. After stirring at room temperature for 2.5 hours, the temperature was raised to 45°C and stirred for 11 hours. The reaction was then washed with acetonitrile and vacuum dried at 62°C overnight to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber.

[0080] The length of the waste polyacrylonitrile fiber is 10 mm.

[0081] The preparation steps of the water-resistant acrylate copolymer are as follows: butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone are mixed to obtain 24 parts by mass of a mixed monomer, and the mixed monomer is then added dropwise to 70 parts by mass of deionized water containing 0.37 parts by mass of an emulsifier and 0.68 parts by mass of a pH adjuster, and then dispersed for 5 minutes using a homogenizer to emulsify the mixture to obtain a stable pre-emulsion; 1 / 3 of the pre-emulsion and 15 parts by mass of deionized water are added to a reactor, stirred and heated to 65° C., 1 / 3 of an initiator ammonium persulfate aqueous solution is added, and the mixture is continued to be stirred and heated to 90° C. During the heating period, when the temperature reaches 78° C., the remaining pre-emulsion and the ammonium persulfate aqueous solution are added, wherein the ammonium persulfate aqueous solution is dripped after the pre-emulsion, and the dripping time is 3 hours. When the total amount of the remaining pre-emulsion added exceeds 2 / 3, 0.5 parts by mass of vinyl triisopropyl silane and 0.5 parts by mass of 3-(methacryloyloxy)propyl trimethoxy silane are started to be dripped, and the initiator aqueous solution is dripped after the organosiloxane; after the initiator aqueous solution is added, the temperature is raised to 95° C. and the reaction is continued for 35 minutes, then the temperature is lowered to 75° C. and kept warm for 35 minutes, cooled, filtered, and discharged to obtain a water-resistant acrylate copolymer.

[0082] The mass ratio of butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone is 50:4:7:13:4; the DNS-B6 and ANPEO in the emulsifier are 10 The mass ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 2:1; the mass volume ratio of ammonium persulfate to deionized water is 11:100, and the amount of ammonium persulfate aqueous solution added in parts by mass is 0.09 parts by mass.

[0083] When in use, add the curing agent to the soft soil to be cured and mix evenly. The amount of curing agent added is 15% of the mass of the soft soil.

[0084] (Example 4)

[0085] The only difference between Example 4 and Comparative Example 2 is that the amount of curing agent added is 7% of the mass of the soft soil, and the other components are the same as those in Example 2.

[0086] (Example 5)

[0087] The only difference between Example 5 and Comparative Example 2 is that the amount of curing agent added is 25% of the mass of the soft soil, and the other components are the same as those in Example 2.

[0088] (Comparative Example 1)

[0089] The difference between Comparative Example 1 and Example 2 is that the raw material components include: 250 parts by mass of cement, 150 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical steel slag, 150 parts by mass of gypsum, 20 parts by mass of waste polyacrylonitrile fiber, and 40 parts by mass of water-resistant acrylic copolymer, and the remaining components are the same as in Example 2.

[0090] (Comparative Example 2)

[0091] The difference between Comparative Example 2 and Example 2 is that the raw material components include: 250 parts by mass of cement, 150 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical slag, 150 parts by mass of gypsum, and 20 parts by mass of modified waste polyacrylonitrile fiber, and the remaining components are the same as those in Example 2.

[0092] (Comparative Example 3)

[0093] The difference between Comparative Example 3 and Example 2 is that the water-resistant acrylate copolymer is obtained by copolymerizing only butyl acrylate, styrene, and acrylic acid, and the other components are the same as those in Example 2.

[0094] (Effect Example)

[0095] Take soft soil samples, as well as the soft soil curing agents in Examples 1 to 5 and Comparative Examples 1 to 3, add water to prepare a slurry with a water content of 55 wt%, then mix the slurry according to the weight ratio of the soft soil curing agent to the soft soil in the corresponding examples and comparative examples, and mold it into a 70.7 mm × 70.7 mm × 70.7 mm cubic test mold. After curing for 3 days, 7 days, and 28 days, the unconfined compressive strength is tested (see "Cement-Soil Mix Design Code" JGJ / T 233-2011);

[0096] The unconfined compressive strength of the solidified soft soil specimens cured for 27 days was tested by immersing them in water for 24 hours. The water stability coefficient = unconfined compressive strength of the immersed specimens / unconfined compressive strength of the normally cured specimens.

[0097] The number of freeze-thaw cycles is designed to be 5 times, one freeze-thaw cycle is 24 hours, the freezing time is 8 hours, and the thawing time is 16 hours. The solidified soft soil specimens that have undergone standard curing for 28 days and soaked in water for the last 1 day are placed in a low-temperature box for freezing. The temperature of the low-temperature box is set to -18°C. After freezing for 8 hours, they are placed in room temperature water for thawing for 16 hours. When the freeze-thaw cycle reaches the designed cycle period, the specimen is subjected to an unconfined compressive strength test; the compressive strength loss of the specimen after the freeze-thaw cycle (%) = the compressive strength of the specimen after the freeze-thaw cycle / the unconfined compressive strength of the normally cured specimen.

[0098] Table 1 below shows the test results:

[0099] Table 1

[0100]

[0101] From the above Table 1, it can be seen that the soft soil cured by the soft soil stabilizer in Examples 1-5 and Comparative Examples 1-3 has high strength, good water stability and good freeze-thaw cycle performance.

[0102] The difference between Comparative Example 1 and Example 2 is that the waste polyacrylonitrile fiber is not modified, and the cured soft soil has low strength, weak water stability and weak freeze-thaw cycle performance.

[0103] The difference between Comparative Example 2 and Example 2 is that the soft soil stabilizer does not add water-resistant acrylate copolymer, and the cured soft soil has low strength, weak water stability and weak freeze-thaw cycle performance.

[0104] The difference between Comparative Example 3 and Example 2 is that the water-resistant acrylate copolymer is only obtained by copolymerization of butyl acrylate, styrene and acrylic acid, and the cured soft soil has low strength, weak water stability and weak freeze-thaw cycle performance.

[0105] The above specific embodiments further illustrate the purpose, technical solutions and beneficial effects of the present application. It should be understood that the above description is only for specific embodiments of the present application and is not intended to limit the present application. 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 low-carbon soft soil solidifying agent, characterized in that: Calculated by mass fraction, the raw material components mainly include 200-300 parts by mass of cement, 100-200 parts by mass of fly ash, 200 parts by mass of mineral powder, 200 parts by mass of metallurgical steel slag, 100-200 parts by mass of gypsum, 10-30 parts by mass of modified waste polyacrylonitrile fiber, and 30-50 parts by mass of water-resistant acrylic copolymer.

2. The low-carbon soft soil curing agent according to claim 1, characterized in that The modified waste polyacrylonitrile fiber is obtained by aminating waste polyacrylonitrile fiber and reacting it with 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, and then grafting 1-vinylimidazole through RAFT polymerization.

3. The low-carbon soft soil curing agent according to claim 1, characterized in that The water-resistant acrylic ester copolymer is obtained by copolymerizing butyl acrylate, styrene, glycidyl methacrylate, vinyl triisopropyl silane, 3-(methacryloyloxy)propyl trimethoxy silane, aluminum acrylate and 1,3-propylene sultone.

4. A method for preparing a low-carbon soft soil solidifying agent, characterized in that: The method comprises the following preparation steps: (1) Weighing and mixing the raw materials according to the mass fraction of each raw material component of claim 1; (2) the modified waste polyacrylonitrile fiber, the water-resistant acrylic copolymer, and 500-700 parts by mass of acetonitrile weighed in step (1) were stirred and uniformly dispersed, followed by reaction at 80° C. for 11-13 hours, and the acetonitrile was removed by rotary evaporation to obtain a mixture A; (3) Mixing the cement, fly ash, mineral powder gypsum, and metallurgical slag weighed in step (1) to obtain a mixture B; (4) Mixing material A and material B to obtain a low-carbon soft soil solidifying agent.

5. The method for preparing a low-carbon soft soil curing agent according to claim 4, characterized in that: The preparation steps of the modified waste polyacrylonitrile fiber are as follows: 0.02-0.04 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.03-0.05 parts by mass of azobisisobutyronitrile, 0.04-0.06 parts by mass of 1-vinylimidazole, 0.06-0.08 parts by mass of butyl methacrylate and 5.5-6.5 parts by mass of methanol are mixed and ultrasonically treated for 4-6 minutes. Then, 0.1 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid-modified polyacrylonitrile fiber is immersed in it, and ultrasonic treatment is continued for 4-6 minutes. Then, the mixture is reacted at 68-72°C under ice bath and nitrogen protection for 23-25 ​​hours. After the reaction is completed, the fiber is washed with methanol and acetone 2-4 times and dried at 60°C for 9-11 hours to obtain modified waste polyacrylonitrile fiber.

6. The method for preparing a low-carbon soft soil curing agent according to claim 5, characterized in that: The preparation steps of the 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber are as follows: 8 to 9 parts by mass of ethylenediamine and 5 parts by mass of deionized water are added to a reactor and preheated to 115 to 125° C., 1 part by mass of dry waste polyacrylonitrile fiber is added, stirred and reacted for 4 hours, filtered and collected, washed with deionized water at 70 to 80° C. until the pH value of the washing solution is 7, and then vacuum dried at 58 to 62° C. for 8 to 10 hours to obtain aminated polyacrylonitrile fiber; 0.15 parts by mass of the aminated polyacrylonitrile fiber is immersed in 4 to 5 parts by mass of acetonitrile solution, then add 0.25-0.35 parts by mass of 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid, 0.055-0.065 parts by mass of 4-dimethylaminopyridine and 0.36-0.4 parts by mass of N,N'-dicyclohexylcarbodiimide, stir at room temperature for 1.5-2.5 hours, then heat to 35-45°C, stir and react for 9-11 hours, then wash with acetonitrile and vacuum dry at 58-62°C overnight to obtain 2-[dodecylthio(thiocarbonyl)thio]-2-methylpropionic acid modified polyacrylonitrile fiber.

7. The method for preparing a low-carbon soft soil curing agent according to claim 6, characterized in that: The length of the waste polyacrylonitrile fiber is 5 to 10 mm.

8. The method for preparing a low-carbon soft soil curing agent according to claim 4, characterized in that: The preparation steps of the water-resistant acrylate copolymer are as follows: butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate, and 1,3-propylene sultone are mixed to obtain 23 to 24 parts by mass of a mixed monomer, and then the mixed monomer is added dropwise to 60 to 70 parts by mass of deionized water containing 0.35 to 0.37 parts by mass of an emulsifier and 0.67 to 0.68 parts by mass of a pH regulator, and then dispersed for 5 minutes using a homogenizer to emulsify the mixture to obtain a stable pre-emulsion; 1 / 3 of the pre-emulsion and deionized water are added to a reactor, stirred and heated to 55 to 65° C., 1 / 3 of an initiator ammonium persulfate aqueous solution is added, and the mixture is stirred and heated to 80 to 90° C. During the heating period, When the temperature reaches 75-78° C., the remaining pre-emulsion and the ammonium persulfate aqueous solution are added, wherein the ammonium persulfate aqueous solution is dripped after the pre-emulsion, and the dripping time is 2-3 hours. When the total amount of the remaining pre-emulsion dripped exceeds 2 / 3, 0.4-0.5 parts by weight of vinyl triisopropyl silane and 0.4-0.5 parts by weight of 3-(methacryloyloxy)propyl trimethoxy silane are started to be dripped, and the initiator aqueous solution is dripped after the organosiloxane. After the initiator aqueous solution is dripped, the temperature is raised to 85-95° C. and the reaction is continued for 25-35 minutes, then the temperature is lowered to 65-75° C. and kept warm for 25-35 minutes, cooled, filtered, and discharged to obtain a water-resistant acrylate copolymer.

9. The method for preparing a low-carbon soft soil curing agent according to claim 8, characterized in that: The mass ratio of butyl acrylate, styrene, glycidyl methacrylate, aluminum acrylate and 1,3-propylene sultone is 50:2-4:5-7:11-13:2-4; the DNS-B6 and ANPEO in the emulsifier are 10 the mass volume ratio of ammonium persulfate to deionized water in the ammonium persulfate aqueous solution is 9 to 11:100, and the amount of ammonium persulfate aqueous solution added is 0.08 to 0.09 parts by mass.

10. A method for using the low-carbon soft soil solidifying agent according to any one of claims 1 to 3, characterized in that: Add the curing agent into the soft soil to be cured and mix evenly. The amount of curing agent added is 7% to 25% of the mass of the soft soil.

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