An anti-freezing and thawing composite soil stabilizer, its preparation method and construction technology

Abstract

The present invention relates to an anti-freezing and thawing composite soil stabilizer, its preparation method and construction technology. The anti-freezing and thawing composite soil stabilizer comprises the following raw materials in parts by mass: 40-50 parts of a cement-based gelling material, 8-12 parts of industrial waste residue, 3-5 parts of an activator, 10-15 parts of a polyacrylamide derivative, 1-2 parts of a low molecular weight polyamide, and 20-25 parts of an aqueous epoxy resin emulsion; the polyacrylamide derivative is obtained by copolymerizing an amino-containing alkenyl imidazolium salt, an acrylamide monomer and an alkenyl polyether monomer in a molar ratio of (1-1.5):1:(0.2-0.4). In the present invention, the polyacrylamide derivative obtained by copolymerizing the amino-containing alkenyl imidazolium salt, the acrylamide monomer and the alkenyl polyether monomer in a certain molar ratio is added as one of the components of the soil stabilizer to the soil to be solidified, which can significantly improve the anti-freezing and thawing performance of the soil.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil stabilizers, and particularly relates to an anti-freezing and thawing composite soil stabilizer, a preparation method thereof and a construction process. Background Art

[0002] A soil stabilizer, namely a soil solidifying admixture, is an admixture that is added to soil and can undergo physical (or chemical) reactions with inorganic binders, soil, and water at normal temperature to improve the engineering properties of the soil. Soil stabilizers are widely used in road engineering, foundation treatment, and slope reinforcement projects due to their remarkable effects in enhancing the engineering properties of soil.

[0003] Soil stabilizers can be classified into inorganic, organic, ionic, bio-enzyme, composite, etc. according to their main components and action mechanisms. Among them, the composite stabilizer is a new type of solidifying material formed by mixing organic materials and inorganic materials in a certain proportion. Organic soil stabilizers generally have good water stability, but their strength is generally not high; inorganic soil stabilizers generally have poor water stability; the composite stabilizer combines the advantages of organic materials and inorganic materials, so the composite stabilizer has received extensive attention from researchers in recent years. Patent CN118930172A discloses a composite soil stabilizer, a preparation method thereof and an application. The components of the composite soil stabilizer include acrylate microemulsion, triphenylvinylphenol polyoxyethylene ether sulfonate, cement, fly ash, and nano-silica. Among them, the mass ratio of acrylate microemulsion, triphenylvinylphenol polyoxyethylene ether sulfonate, cement, fly ash, and nano-silica is 8:2:2:3:1; this composite soil stabilizer can solidify soil in a relatively short time and has the characteristics of high compressive strength and good waterproof performance. Patent CN101597496B discloses a cement-based soil stabilizer, a preparation method thereof and an application. The soil stabilizer is made of the following raw materials and their mass percentages: sodium sulfate: 10%-40%, sodium tripolyphosphate: 2%-6%, carbamide: 2%-5%, polyacrylamide: 2%-8%, sodium dodecyl sulfate emulsifier: 1%-5%, triethanolamine: 2%-10%, sodium silicate: 10%-60%, sodium hydroxide: 4%-12%, sodium carbonate: 2%-15%, potassium hydroxide 2%-6%, methyl sodium silicate 2%-8%, and the sum of the percentages of the above raw materials is 100%; this soil stabilizer can fully stimulate various physical, chemical, and physico-chemical reactions between cement and soil, greatly improving the engineering properties of cement soil, increasing its strength, reducing its dry shrinkage, and enhancing its durability.

[0004] The soil stabilizer prepared by the above patent improves the strength, waterproof performance and dry shrinkage performance of the soil. However, in the central and northern regions of China, the usage environment of the solidified soil is generally relatively harsh, with large temperature changes in the four-season cycle. The solidified soil generally has poor freeze-thaw cycle resistance, resulting in a short service life of the ground. Therefore, it is necessary to improve the freeze-thaw cycle resistance of the soil stabilizer. Summary of the Invention

[0005] In view of the problem that the freeze-thaw cycle resistance of the existing soil stabilizer remains to be improved and the scope of application areas is limited, the present invention provides an anti-freeze-thaw composite soil stabilizer, which can significantly improve the freeze-thaw resistance of the solidified soil while having good water stability and strength.

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

[0007] An anti-freeze-thaw composite soil stabilizer, comprising the following raw materials in parts by mass:

[0008] Cement-based cementitious material 40 - 50 parts,

[0009] Industrial waste residue 8 - 12 parts,

[0010] Activator 3 - 5 parts,

[0011] Polyacrylamide derivative 10 - 15 parts,

[0012] Low molecular weight polyamide 1 - 2 parts,

[0013] Waterborne epoxy resin emulsion 20 - 25 parts;

[0014] The polyacrylamide derivative is copolymerized from an amino-containing vinyl imidazolium salt, an acrylamide monomer, and a vinyl polyether monomer in a molar ratio of (1 - 1.5):1:(0.2 - 0.4); the weight-average molecular weight of the polyacrylamide derivative is 200000 - 300000 g / mol.

[0015] The inventor unexpectedly found that adding a self-made polyacrylamide derivative to the composite soil stabilizer of the present invention, which is copolymerized from an alkenyl imidazole salt containing an amino group, an acrylamide monomer, and an alkenyl polyether monomer in a certain molar ratio, as one of the components of the soil stabilizer to the soil to be solidified can significantly improve the freeze-thaw resistance of the soil. The possible reasons are as follows. On the one hand, the alkenyl imidazole salt containing an amino group is an ionic liquid containing an imidazole group and has good temperature stability. At the same time, when the polyacrylamide derivative obtained by copolymerization is added to the soil, the charge ions inside it undergo ion exchange with the adsorption on the surface of soil particles, thereby reducing the repulsive force between soil particles and making the soil particles easier to approach. On the other hand, the amino active group from the alkenyl imidazole salt containing an amino group and the amide group from the acrylic monomer in the polyacrylamide derivative can both undergo cross-linking reactions with epoxy resin to form a network structure. In addition, the polyether in the alkenyl polyether monomer has good chain segment mobility, making the copolymerized polyacrylamide derivative have a relatively large molecular size and a multi-branched structure, which can disperse the expansion and contraction stresses during the freeze-thaw cycle and avoid stress concentration. The three monomers cooperate synergistically, but it is necessary to control the alkenyl imidazole salt containing an amino group, the acrylamide monomer, and the alkenyl polyether monomer within a suitable proportion range to ensure good freeze-thaw cycle resistance, water stability, and strength at the same time.

[0016] Preferably, the polyacrylamide derivative is copolymerized from an alkenyl imidazole salt containing an amino group, an acrylamide monomer, and an alkenyl polyether monomer in a molar ratio of (1.2 - 1.5):1:(0.2 - 0.3).

[0017] Further, the alkenyl imidazole salt containing an amino group is selected from at least one of 1-vinyl-3-aminopropylimidazole tetrafluoroborate, 1-allyl-3-aminopropylimidazole tetrafluoroborate, and 1-vinyl-3-aminopropylimidazole chloride; the acrylamide monomer is selected from at least one of acrylamide and N-isopropylacrylamide; the alkenyl polyether monomer is selected from at least one of methylallyl polyethylene glycol ether, methylbutenyl polyethylene glycol ether, and ethylene glycol mono vinyl polyethylene glycol ether, and the number average molecular weight of the polyethylene glycol segment is 400 - 800.

[0018] Further, the polyacrylamide derivative is prepared by a method including the following steps: dissolving the alkenyl imidazole salt containing an amino group, the acrylamide monomer, the alkenyl polyether monomer, and an initiator in water to form a mixed solution, then carrying out a copolymerization reaction at 50 - 70 °C for 6 - 12 h, and cooling to obtain a suspension; then carrying out vacuum distillation to obtain the polyacrylamide derivative.

[0019] Further, the initiator is at least one of potassium persulfate, ammonium persulfate, and hydrogen peroxide, and the dosage of the initiator is 1-3% of the total mass of the amino-group-containing vinyl imidazolium salt, acrylamide monomer, and vinyl polyether monomer. The dosage of the initiator affects the molecular weight of the polyacrylamide derivative. In the present invention, the dosage of the initiator is higher than that in the general case of preparing linear polyacrylamide, aiming to control the molecular weight of the polyacrylamide derivative not to be too high, as an overly high molecular weight will reduce its solubility.

[0020] Further, the cement-based gelling material is a compound of cement, lime, and fly ash in a mass ratio of 1:(0-0.25):(0-0.2); the cement is Portland cement with a grade strength of 42.5-62.5; the specific surface area of the fly ash is 500-700 m 2 / kg.

[0021] Further, the industrial waste residue is at least one of steel slag, blast furnace slag, and slag, and its particle size is 20-50 μm.

[0022] Further, the activator is selected from at least one of magnesium chloride, magnesium oxide, sodium silicate, sodium chloride, and calcium chloride.

[0023] Further, the molecular weight of the low molecular weight polyamide is 600-1500. For example, 200 low molecular weight polyamide, 203 low molecular weight polyamide, 300 low molecular weight polyamide, 650 low molecular weight polyamide, 651 low molecular weight polyamide.

[0024] Further, the solid content of the waterborne epoxy resin emulsion is 40-50%, and the epoxy value is 0.20-0.25 mol / 100 g.

[0025] The present invention also provides a preparation method of the above-mentioned freeze-thaw resistant composite soil stabilizer, including the following steps: mixing the cement-based gelling material, industrial waste residue, and activator to obtain a mixed dry material; mixing the polyacrylamide derivative, low molecular weight polyamide, and waterborne epoxy resin emulsion to obtain a mixed liquid; when in use, mixing the mixed dry material with the mixed liquid to obtain the freeze-thaw resistant composite soil stabilizer.

[0026] The present invention also provides a construction process of the above-mentioned freeze-thaw resistant composite soil stabilizer, including the following steps:

[0027] a) Construction layout and excavation of foundation pit: Conduct construction survey and layout according to the construction drawings, and then excavate the foundation pit;

[0028] b) Mixing: Mix the freeze-thaw resistant composite soil stabilizer evenly with the soil to be solidified to obtain a mixed soil, and then add water to adjust the moisture content of the mixed soil. The dosage of the freeze-thaw resistant composite soil stabilizer is 8-15 wt% of the soil to be solidified;

[0029] c) Compaction: Initially compact the mixed soil until it takes shape, and then roll it after leveling.

[0030] d) Curing: Immediately cure after compaction is completed, and the curing period is ≥ 7 days.

[0031] Furthermore, in step b), the water content of the soil to be solidified is 5 - 30 wt%, the liquid limit is 40 - 50%, the plastic limit is 18 - 30%, and the clay content with an average particle size < 2 μm is 20 - 30%; the water content of the mixed soil is 10 - 20 wt%.

[0032] Furthermore, in step c), the initial compaction is carried out by a 10 - 15 ton roller with static pressure for 1 - 2 passes; the rolling is carried out by a 15 - 20 ton roller with strong vibration for 2 - 4 passes; the speed of the 10 - 15 ton roller is 1 - 2 km / h, and the speed of the 15 - 20 ton roller is 2 - 4 km / h.

[0033] The curing in step (d) can adopt methods such as watering curing, film covering curing, geotextile covering curing, etc., and an appropriate method should be selected in combination with the actual engineering situation.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] 1. The composite soil stabilizer of the present invention contains a polyacrylamide derivative, which is copolymerized from an amino - containing vinyl imidazolium salt, an acrylamide - type monomer, and a vinyl polyether monomer in a certain molar ratio. The amino - containing vinyl imidazolium salt is an imidazole - containing ionic liquid with good temperature stability; at the same time, the polyacrylamine derivative obtained by its copolymerization also has the characteristics of ionic liquid. When it is added to the soil, the charge ions inside it perform ion exchange with the adsorption on the surface of soil particles, thereby reducing the repulsive force between soil particles and making the soil particles easier to approach. Moreover, the amino active groups and amide groups in the polyacrylamine derivative can both cross - link with epoxy resin to form a network structure. In addition, the polyether in the vinyl polyether monomer has good chain segment mobility, making the copolymerized polyacrylamide derivative have a large molecular size and a multi - branched structure. This structure can disperse the expansion and contraction stresses during the freeze - thaw cycle and avoid stress concentration. In summary, the copolymerized polyacrylamide derivative, as one of the components of the soil stabilizer, is added to the soil to be solidified, which can significantly improve the freeze - thaw resistance of the soil.

[0036] 2. The composite soil stabilizer of the present invention is a composite of an organic - inorganic soil stabilizer, combining the advantages of organic soil stabilizers and inorganic soil stabilizers, and has good water stability and strength while significantly improving the freeze - thaw resistance of the soil. Specific Embodiments

[0037] The present invention will be further described below in conjunction with specific embodiments, but it is not limited to the content in the specification. Unless otherwise specified, "parts" in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0038] The methyl allyl polyethylene glycol ether is selected from Aladdin, and the number average molecular weight of the polyethylene glycol segment is 600.

[0039] The portland cement of grade 42.5 is purchased from Xiaogan Phoenix Cement Co., Ltd.

[0040] The fly ash is class I fly ash with a specific surface area of 580 m 2 / kg.

[0041] The converter steel slag comes from Taiyuan Iron and Steel Group Co., Ltd., and the average particle size is about 42 μm.

[0042] The waterborne epoxy resin emulsion HyPer WE 1051 with a solid content of 50% and an epoxy value of 0.25 mol / 100 g is purchased from Wuhan Hyperbranched Resin Technology Co., Ltd.

[0043] The 650 low molecular weight polyamide is purchased from Wuxi Changgan Chemical Co., Ltd.

[0044] The anionic polyacrylamide is purchased from Henan Kaijie Water Treatment Co., Ltd., and the weight average molecular weight is 5 million g / mol.

[0045] The soil to be cured comes from the Meishan section of the Liuan-Wuwei Expressway, with a water content of 23.5%, a liquid limit of 47.2%, a plastic limit of 19.2%, and a clay content with an average particle size < 2 μm of 25.7%.

[0046] Example 1

[0047] 1) Prepare a mixture of 1-vinyl-3-aminopropylimidazole tetrafluoroborate, N-isopropylacrylamide, and methyl allyl polyethylene glycol ether in a molar ratio of 1:1:0.2, and then dissolve it together with 2% of the initiator potassium persulfate based on the total mass of the mixture in pure water to form a mixed solution; then stir and react at 60 °C for 6 h, cool to room temperature to obtain a suspension; finally, remove impurities by vacuum distillation of the suspension to obtain a polyacrylamide derivative, and its weight average molecular weight measured by gel permeation chromatography (GPC) is 208000 g / mol;

[0048] 2) Mix 40 kg of portland cement of grade 42.5, 8 kg of converter steel slag and 3 kg of calcium chloride evenly in a mixer to obtain a mixed dry material; mix 10 kg of the polyacrylamide derivative prepared in step 1), 1 kg of 650 low-molecular-weight polyamide and 20 kg of waterborne epoxy resin emulsion evenly in a mixing barrel to obtain a mixed liquid; finally, add the mixed liquid into the mixer and mix it evenly with the mixed dry material to obtain an anti-freezing and thawing composite soil stabilizer;

[0049] 3) Use a road mixer to mix 8 kg of the above anti-freezing and thawing composite soil stabilizer with 100 kg of the soil to be solidified evenly, add water to adjust the moisture content of the mixed soil to 15%, and then spread it on the road surface and compact it twice with a 10-ton steel wheel roller, scrape it flat, and strongly vibrate and roll it three times with a 20-ton steel wheel roller.

[0050] Example 2

[0051] The rest is the same as in Example 1, except that: in step 1), the molar ratio of 1-vinyl-3-aminopropylimidazole tetrafluoroborate, N-isopropylacrylamide, and methallyl polyethylene glycol ether is 1.2:1:0.3. The polyacrylamide derivative prepared in step 1) has a weight-average molecular weight of 226,000 g / mol measured by gel permeation chromatography (GPC).

[0052] Example 3

[0053] The rest is the same as in Example 1, except that: in step 1), the molar ratio of 1-vinyl-3-aminopropylimidazole tetrafluoroborate, N-isopropylacrylamide, and methallyl polyethylene glycol ether is 1.5:1:0.3. The polyacrylamide derivative prepared in step 1) has a weight-average molecular weight of 285,000 g / mol measured by gel permeation chromatography (GPC).

[0054] Example 4

[0055] The rest is the same as in Example 1, except that: in step 1), the molar ratio of 1-vinyl-3-aminopropylimidazole tetrafluoroborate, N-isopropylacrylamide, and methallyl polyethylene glycol ether is 1.5:1:0.4. The polyacrylamide derivative prepared in step 1) has a weight-average molecular weight of 262,000 g / mol measured by gel permeation chromatography (GPC).

[0056] Example 5

[0057] The rest is the same as Example 1, except that: in step 2), 40 kg of cement-based cementitious material with a total mass of 40 kg obtained by compounding 27.6 kg of silicate cement, 6.9 kg of lime and 5.5 kg of fly ash (i.e., silicate cement, lime and fly ash are in a mass ratio of 1:0.25:0.2) is used to replace 40 kg of silicate cement; and the amount of polyacrylamide derivative used is 15 kg.

[0058] Example 6

[0059] The rest is the same as Example 1, except that: in step 2), the amount of grade 42.5 silicate cement is 50 kg, the amount of converter slag is 12 kg, the amount of calcium chloride is 5 kg, the amount of polyacrylamide derivative is 18 kg, the amount of 650 low molecular weight polyamide is 2 kg, and the amount of water-based epoxy resin emulsion is 25 kg.

[0060] Comparative Example 1

[0061] The rest is the same as Example 1, except that: step 1 is omitted, and in step 2), an anionic polyacrylamide of equal mass is used to replace the polyacrylamide derivative.

[0062] Comparative Example 2

[0063] The rest is the same as Example 1, except that in step 1), the molar ratio of 1-vinyl-3-aminopropyl imidazole tetrafluoroborate, N-isopropylacrylamide, and methyl allyl polyethylene glycol ether is 0.5:1:0.5.

[0064] Testing and analysis

[0065] The solidified soil samples prepared in the above embodiments and comparative examples were placed in a standard curing room at a temperature of 20±2°C and a relative humidity of more than 95% for a certain number of days and then subjected to the following performance tests:

[0066] Unconfined compressive strength: The soil samples were tested after 28 days of standard curing according to standard CJ / T486-2015.

[0067] Freeze-thaw resistance test: Soak the soil after standard curing for 28 days in water (20±2℃) for 24 hours, freeze it in a refrigerator at -18℃ for 24 hours, take it out and place it in a constant temperature box at 20℃ for 24 hours, which is recorded as one freeze-thaw cycle. Repeat this cycle for 5 times, retest the unconfined compressive strength, and calculate the strength retention rate.

[0068] Water stability coefficient: It characterizes the water resistance of solidified soil. A high water stability coefficient means that the solidified soil is not easy to soften, deform or crack when encountering water or in a humid environment, and can maintain good stability. The cured soil specimens are tested according to the standard CJ / T 486-2015. The soil is cured for 7 days, and the cured specimens are immersed in water for 24 hours, with the water temperature maintained at 20±2°C. Record the maximum pressure value when the specimen breaks. Water stability coefficient = 。

[0069] The test results of the above performances are shown in Table 1.

[0070] Table 1 Performance Test

[0071] 。

[0072] It can be seen from the performance test results in Table 1 that the composite soil stabilizer of the present invention can effectively improve the freeze-thaw resistance of the soil, and at the same time has good water stability and high strength.

[0073] The above detailed description is a specific description of one of the feasible embodiments of the present invention. This embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or change without departing from the present invention shall be included within the scope of the technical solution of the present invention.

Claims

1. A freeze-thaw resistant composite soil solidifier, characterized in that: The invention comprises the following raw materials in parts by weight: 40~50 parts of cement-based cementitious materials, 8~12 parts of industrial waste residue, 3~5 parts of stimulant, 10-15 parts of polyacrylamide derivatives, 1~2 parts of low molecular weight polyamide, 20-25 parts of water-based epoxy resin emulsion; The polyacrylamide derivative is obtained by copolymerizing an amino-containing alkenyl imidazole salt, an acrylamide monomer, and an alkenyl polyether monomer in a molar ratio of (1-1.5):1:(0.2-0.4); the weight average molecular weight of the polyacrylamide derivative is 200000-300000 g / mol.

2. The freeze-thaw resistant composite soil solidifier according to claim 1, characterized in that: The polyacrylamide derivative is obtained by copolymerizing an amino-containing alkenyl imidazole salt, an acrylamide monomer, and an alkenyl polyether monomer in a molar ratio of (1.2-1.5):1:(0.2-0.3).

3. The freeze-thaw resistant composite soil solidifier according to claim 1, characterized in that: The amino-containing alkenyl imidazole salt is selected from at least one of 1-vinyl-3-aminopropyl imidazole tetrafluoroborate, 1-allyl-3-aminopropyl imidazole tetrafluoroborate, and 1-vinyl-3-aminopropyl imidazole chloride; the acrylamide monomer is selected from at least one of acrylamide and N-isopropyl acrylamide; the alkenyl polyether monomer is selected from at least one of methyl allyl polyethylene glycol ether, methyl butyl polyethylene glycol ether, and ethylene glycol monovinyl polyethylene glycol ether, wherein the number average molecular weight of the polyethylene glycol segment is 400-800.

4. The freeze-thaw resistant composite soil solidifier according to claim 1, characterized in that: The polyacrylamide derivative is prepared by a method comprising the following steps: dissolving an amino-containing alkenyl imidazole salt, an acrylamide monomer, an alkenyl polyether monomer and an initiator in water to form a mixed solution, and then copolymerizing at 50-70° C. for 6-12 hours to obtain the polyacrylamide derivative.

5. The freeze-thaw resistant composite soil solidifier according to claim 4, characterized in that: The initiator is at least one of potassium persulfate, ammonium persulfate and hydrogen peroxide, and the amount of the initiator is 1-3% of the total mass of the amino-containing alkenyl imidazole salt, acrylamide monomer and alkenyl polyether monomer.

6. The freeze-thaw resistant composite soil solidifier according to claim 1, characterized in that: The cement-based cementitious material is a compound of cement, lime and fly ash in a mass ratio of 1: (0-0.25): (0-0.2); the cement is silicate cement with a grade strength of 42.5-62.5; the specific surface area of ​​the fly ash is 500-700m 2 / kg.

7. The freeze-thaw resistant composite soil solidifier according to claim 1, characterized in that: The industrial waste slag is selected from at least one of steel slag, blast furnace slag and slag, and has a particle size of 20 to 50 μm; and / or The activator is selected from at least one of magnesium chloride, magnesium oxide, sodium silicate, sodium chloride and calcium chloride; and / or The molecular weight of the low molecular weight polyamide is 600-1500; and / or The waterborne epoxy resin emulsion has a solid content of 40-50% and an epoxy value of 0.20-0.25 mol / 100g.

8. The method for preparing the freeze-thaw resistant composite soil solidifying agent according to any one of claims 1 to 7, characterized in that: The following steps are involved: The cement-based cementitious material, industrial waste residue and activator are mixed to obtain a mixed dry material; the polyacrylamide derivative, low molecular weight polyamide and water-based epoxy resin emulsion are mixed to obtain a mixed liquid; when using, the mixed dry material and the mixed liquid are mixed evenly to obtain a freeze-thaw resistant composite soil solidifier.

9. The construction process of the freeze-thaw resistant composite soil solidifier according to any one of claims 1 to 7, characterized in that: The following steps are involved: a) Construction layout and foundation pit excavation: Construction measurement and layout are carried out according to the construction drawings, and then the foundation pit is excavated; b) Mixing: The freeze-thaw-resistant composite soil solidifying agent is mixed evenly with the soil to be solidified to obtain mixed soil, and then water is added to adjust the moisture content of the mixed soil. The amount of the freeze-thaw-resistant composite soil solidifying agent is 8-15wt% of the soil to be solidified; c) Compaction: Compact the mixed soil until it is formed, then roll it after leveling; d) Curing: Curing should be done immediately after compaction is completed, and the curing period should be ≥ 7 days.

10. The construction process of the freeze-thaw resistant composite soil solidifier according to claim 9, characterized in that: In step b), the moisture content of the soil to be solidified is 5-30wt%, the liquid limit is 40-50%, the plastic limit is 18-30%, and the clay content with an average particle size of less than 2 μm is 20-30%; the moisture content of the mixed soil is 10-20wt%.