An anti-dry-wet cycle composite soil stabilizer and its preparation method

Abstract

The present invention provides an anti-dry-wet cycling composite soil stabilizer and a preparation method thereof. The stabilizer comprises the following raw materials: 5-10 parts by weight of polyacrylamide, 20-30 parts by weight of cyclodextrin star derivative, 5-10 parts by weight of polyvinyl alcohol, 5-8 parts by weight of inorganic salt, 5-8 parts by weight of sodium silicate, 10-15 parts by weight of waterborne epoxy resin emulsion, 1-3 parts by weight of polyoxypropylene triamine and water. The amount of water used makes the solid content of the anti-dry-wet cycling composite soil stabilizer 25-60 wt%. The cyclodextrin star derivative is prepared by an esterification reaction of carboxymethyl-β-cyclodextrin and methoxypolyethylene glycol with a molar ratio of carboxyl to hydroxyl of 1:1.1-1.2 under the action of an alkali catalyst. The weight-average molecular weight of methoxypolyethylene glycol is 1000-1500 g / mol. Multiple graft chains of the cyclodextrin star derivative disperse the swelling and shrinkage stresses of the soil during the dry-wet cycling process in different directions, avoiding stress concentration from damaging the molecular structure.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil solidifying agents, and particularly relates to a dry-wet cycle resistant composite soil solidifying agent and a preparation method thereof. Background Art

[0002] In the field of infrastructure construction, as a new type of green building material, soil solidifying agents are widely used due to their remarkable effects in improving the engineering properties of soil. Due to problems such as low strength and poor stability of natural soil, it is usually difficult to meet engineering requirements. Soil solidifying agents can significantly improve the strength, bearing capacity and durability of soil through physical, chemical or biological actions, which are crucial for application scenarios such as road engineering, foundation treatment and slope reinforcement engineering.

[0003] Soil stabilizer is a soil hardening agent that can directly cement the surface of soil particles in the soil or react with clay minerals to generate a gelling substance at normal temperature. Its essence is to change the surface hydrophobic and lubricating properties of the soil, so that the soil can be compacted, reduce the channels for water to enter and exit, and continuously improve the strength and water stability. Soil stabilizers can be classified into inorganic, organic, bioenzyme, composite stabilizers, etc. according to their main components. Among them, the composite stabilizer is a new type of curing material formed by mixing organic materials and inorganic materials in a certain proportion. The composite stabilizer can give full play to the advantages of organic materials and effectively modify the soil. At the same time, it can also well avoid the damage caused by poor water stability and dry shrinkage of the structure when using inorganic materials alone, so that it can meet the requirements of engineering application technical conditions. In recent years, it has received extensive attention from researchers. For example, a soil stabilizer, solidified soil and its application disclosed in Patent CN115044382B. The soil stabilizer includes 15-20 parts of modified sodium silicate, 10-20 parts of sulfonated oil, 3-5 parts of oleic acid amide, 5-8 parts of triisopropanolamine, 1-2 parts of inorganic salt, 1-3 parts of swelling agent, 2-3 parts of pore sealant and 40-60 parts of water. A cement-based soil stabilizer and its preparation and application disclosed in Patent CN101597496B. The prepared 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%. The sum of the percentages of the above raw materials is 100%. A rapid hardening soil stabilizer and its preparation method and application disclosed in Patent CN113149592B. The rapid hardening soil stabilizer includes: 40-80 parts of isocyanate-modified polyvinyl alcohol emulsion; 10-40 parts of anionic surfactant; 3-10 parts of sodium silicate; 3-10 parts of salt compound; 1-5 parts of phenol butanol; 0.5-2 parts of pore sealant; 10-30 parts of water.

[0004] The above are common composite stabilizers mainly based on linear organic polymers such as polyacrylamide, polyvinyl alcohol, and sulfonated oil. They can effectively improve the strong hydrophilicity of clay minerals, weaken the swelling characteristics, improve the cohesive strength, and increase the bearing capacity of the soil body. However, linear organic polymer materials are prone to molecular structure damage during the wet-dry cycle, resulting in poor resistance to wet-dry cycles. Therefore, it is necessary to improve the composite stabilizer mainly based on ordinary linear organic polymer materials to improve its resistance to wet-dry cycles. Summary of the Invention

[0005] To solve the problem of poor resistance to dry-wet cycles of the above-mentioned composite curing agent, the composite soil curing agent provided by the present invention contains a cyclodextrin star derivative grafted with polyvinyl alcohol monomethyl ether, which has a relatively large molecular size and a star shape. Multiple graft chains can disperse the expansion and contraction stresses of the soil during the dry-wet cycle in different directions, avoiding stress concentration from damaging the molecular structure. In addition, by utilizing the adsorption and intercalation of the graft chains of the cyclodextrin star derivative - polyvinyl alcohol monomethyl ether by the soil, the microscopic pore area of the soil can be significantly reduced, and the entry and discharge of water during the dry-wet cycle can be reduced, further improving the resistance to dry-wet cycles. The waterborne epoxy resin emulsion has good bonding properties and can cooperate with the cyclodextrin star derivative to maintain the relative positions between particles when the soil shrinks and expands, keeping the structure of the soil intact.

[0006] To achieve the above object, the following technical solutions are adopted:

[0007] An anti-dry-wet cycle composite soil curing agent, comprising the following raw materials: 5 - 10 parts by weight of polyacrylamide, 20 - 30 parts by weight of cyclodextrin star derivative, 5 - 10 parts by weight of polyvinyl alcohol, 5 - 8 parts by weight of inorganic salt, 5 - 8 parts by weight of sodium silicate, 10 - 15 parts by weight of waterborne epoxy resin emulsion, 1 - 3 parts by weight of polyoxypropylene triamine, and water. The amount of water used makes the solid content of the anti-dry-wet cycle composite soil curing agent 25 - 60 wt%, preferably 40 - 60 wt%. The cyclodextrin star derivative is prepared by an esterification reaction of carboxymethyl-β-cyclodextrin and poly(ethylene glycol) monomethyl ether under the action of a base catalyst with a molar ratio of carboxyl group to hydroxyl group of 1:1.1 - 1.2. The poly(ethylene glycol) monomethyl ether has a weight-average molecular weight of 1000 - 1500 g / mol.

[0008] The average substitution degree DS of the carboxymethyl-β-cyclodextrin is 0.9 - 1.2, and the average substitution degree DS represents the number of hydroxyl groups substituted on each glucose molecular unit on average.

[0009] The cyclodextrin star derivative is prepared by a method including the following steps:

[0010] Add carboxymethyl-β-cyclodextrin, poly(ethylene glycol) monomethyl ether, and base catalyst to a reaction kettle, mix evenly and react. The esterification reaction is carried out by the inert gas water-carrying method. After the reaction is completed, remove impurities by vacuum distillation to obtain the cyclodextrin star derivative.

[0011] The amount of the base catalyst used is 1 - 2 wt% of the sum of the masses of carboxymethyl-β-cyclodextrin and poly(ethylene glycol) monomethyl ether. The base catalyst is selected from one or a combination of two or more of sodium hydroxide, potassium hydroxide, and sodium methoxide. The esterification reaction conditions are to react at 150 - 200 °C for 12 - 24 h.

[0012] The solid content of the aqueous epoxy resin emulsion is 40-50 wt%, and the epoxy value is 0.20-0.25 mol / 100 g.

[0013] The weight average molecular weight of the polyoxypropylene triamine is 300-500 g / mol, and the amine value is 6.1-6.6 meq / g.

[0014] The polyacrylamide is an anionic polyacrylamide, and the weight average molecular weight is 8 million - 10 million g / mol.

[0015] The weight average molecular weight of the polyvinyl alcohol is 30,000 - 60,000 g / mol.

[0016] The inorganic salt is selected from one or a combination of two or more of sodium sulfate, calcium sulfate, ferric sulfate, sodium chloride, and calcium chloride.

[0017] The modulus of the sodium silicate is 2.0-2.4.

[0018] The present invention also provides a preparation method of the above anti-dry and wet cycle composite soil stabilizer, which includes the following steps:

[0019] Add water to the reaction kettle and heat it up. Add the inorganic salt and sodium silicate and mix evenly. Then add polyacrylamide, cyclodextrin star derivative, polyvinyl alcohol, and polyoxypropylene triamine and mix evenly. Finally, add the aqueous epoxy resin emulsion and mix evenly to obtain the anti-dry and wet cycle composite soil stabilizer.

[0020] The heating up is to 30-50 °C.

[0021] An application of an anti-dry and wet cycle composite soil stabilizer includes the following steps:

[0022] Mix the gelling material and the soil evenly, add the above anti-dry and wet cycle composite soil stabilizer and mix evenly. Add water to adjust the moisture content of the mixed soil, and then spread it on the surface and compact it with a roller.

[0023] The moisture content of the soil is 5-60% (preferably 20-30 wt%), the liquid limit is 40-50%, the plastic limit is 20-30%, and the clay content with an average particle size <2 μm is 20-30%. The gelling material is selected from one or a combination of two or more of fly ash, lime, and cement. The mass ratio of the anti-dry and wet cycle composite soil stabilizer, the gelling material, and the soil is 0.05-0.5: 3-15: 100. Adjusting the moisture content of the mixed soil is to adjust it to 13-20 wt%, preferably 16-20 wt%.

[0024] Compared with the prior art, the beneficial effects of the present invention are:

[0025] The composite soil stabilizer of the present invention contains a cyclodextrin star derivative grafted with polyvinyl alcohol monomethyl ether, which has a relatively large molecular size and a star shape. Multiple graft chains can disperse the expansion and contraction stresses of the soil during the wet-dry cycle in different directions, avoiding stress concentration and damage to the molecular structure. In addition, by utilizing the adsorption and intercalation of the graft chain - polyvinyl alcohol monomethyl ether of the cyclodextrin star derivative by the soil, the microscopic pore area of the soil can be significantly reduced, and the entry and discharge of water during the wet-dry cycle can be reduced, further improving the resistance to the wet-dry cycle. The waterborne epoxy resin emulsion has good bonding properties and can cooperate with the cyclodextrin star derivative to maintain the relative positions between particles when the soil shrinks and expands, keeping the structure of the soil intact. Detailed Embodiments

[0026] 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, the "parts" mentioned in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0027] The poly(ethylene glycol) monomethyl ether has a weight-average molecular weight of 1000, numbered E080823, and is purchased from Aladdin Chemistry.

[0028] The poly(ethylene glycol) monomethyl ether has a weight-average molecular weight of 1500, numbered E082458, and is purchased from Aladdin Chemistry.

[0029] The poly(ethylene glycol) monomethyl ether has a weight-average molecular weight of 750, numbered E080730, and is purchased from Aladdin Chemistry.

[0030] The poly(ethylene glycol) monomethyl ether has a weight-average molecular weight of 2000, numbered E080731, and is purchased from Aladdin Chemistry.

[0031] 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.

[0032] The soil has a water content of 22.8%, a liquid limit of 49.0%, a plastic limit of 22.8%, and the clay particle content with an average particle size < 2 μm is 23.94%, from the Zhaoquan Town section of the Shiheng Expressway.

[0033] The polyvinyl alcohol has a weight-average molecular weight of 35,000 g / mol, product number ZZS-PVOH-Mw-35K, and is purchased from Shanghai Zhenzhu Biotechnology Co., Ltd.

[0034] The anionic polyacrylamide is purchased from Henan Kaijie Water Treatment Co., Ltd., with a weight-average molecular weight of 10 million g / mol.

[0035] The polyoxypropylene triamine is Huntsman T403, with a weight-average molecular weight of 440 g / mol and an amine value of 6.2 meq / g. It should be noted that in the translation of the above content, the company name "Aladdin Chemistry" is used instead of "Annaiji Chemistry" in the original text because "Annaiji Chemistry" may not be a well-known and common name in the international chemical field. If there is a specific requirement for the translation of the company name, it can be adjusted according to the actual situation. Also, the description of the source of the reagents in the original text may not be very clear in terms of compliance with patent writing norms. The above translation is for reference only to meet the requirements of language conversion.

[0036] The average substitution degree DS of carboxymethyl-β-cyclodextrin is 0.9, which is purchased from Shandong Binzhou Zhiyuan Biotechnology Co., Ltd.

[0037] Example 1

[0038] 1) Add 1 mol of carboxymethyl-β-cyclodextrin, 6.93 mol of methoxypolyethylene glycol with a weight-average molecular weight of 1500, and 2 wt% of sodium hydroxide based on the total mass of carboxymethyl-β-cyclodextrin and methoxypolyethylene glycol into a reaction kettle, mix evenly, heat up to 180 °C and carry out an esterification reaction for 12 h. During the reaction, N 2 is introduced for protection and to carry out the water generated by the reaction to promote the reaction in the direction of esterification. After the reaction, carry out vacuum distillation to remove impurities to obtain a cyclodextrin star derivative.

[0039] 2) Add 118.5 kg of water (solid content 40%) into a reaction kettle, heat up to 50 °C, add 4 kg of calcium sulfate, 4 kg of calcium chloride, and 8 kg of sodium silicate, mix evenly, then add 10 kg of anionic polyacrylamide, 30 kg of cyclodextrin star derivative, 5 kg of polyvinyl alcohol, and 3 kg of polyoxypropylene triamine T403, mix evenly, and finally add 15 kg of waterborne epoxy resin emulsion HyPer WE 1051 and mix evenly to obtain an anti-dry and wet cycling composite soil stabilizer.

[0040] 3) Mix 15 kg of Portland cement with a strength grade of 42.5 evenly with 100 kg of soil, add 0.3 kg of the above anti-dry and wet cycling composite soil stabilizer and mix evenly. Add water to adjust the moisture content of the mixed soil to 20 wt%, and then spread it on the surface and compact it with a roller.

[0041] Example 2

[0042] The rest is the same as Example 1, except that in step 1), methoxypolyethylene glycol with a weight-average molecular weight of 1000 is used to replace methoxypolyethylene glycol with a weight-average molecular weight of 1500 in an equimolar amount.

[0043] Example 3

[0044] The rest is the same as Example 1, except that in step 2), the dosage of the cyclodextrin star derivative is 20 kg, and the initial water dosage in the reaction kettle is adjusted accordingly to make the solid content 40%.

[0045] Example 4

[0046] The rest is the same as Example 1, except that in step 2), the dosage of the waterborne epoxy resin emulsion HyPer WE 1051 is 10 kg.

[0047] Example 5

[0048] The rest is the same as in Example 1, except that in step 3), the dosage of the anti-dry-wet cycling composite soil stabilizer is 0.1 kg.

[0049] Example 6

[0050] 1) Add 1 mol of carboxymethyl-β-cyclodextrin, 7.56 mol of methoxypolyethylene glycol with a weight-average molecular weight of 1000, and 2 wt% of sodium hydroxide based on the total mass of carboxymethyl-β-cyclodextrin and methoxypolyethylene glycol to a reaction kettle, mix evenly, heat up to 180 °C, and carry out an esterification reaction for 12 h. During the reaction, continuously introduce N 2 to carry out protection and remove the water generated in the reaction to promote the reaction in the esterification direction. After the reaction, carry out vacuum distillation to remove impurities to obtain a cyclodextrin star derivative.

[0051] 2) Add 100.5 kg of water (solid content 40%) to a reaction kettle, heat up to 50 °C, add 4 kg of calcium sulfate, 4 kg of calcium chloride, and 8 kg of sodium silicate, mix evenly, add 10 kg of anionic polyacrylamide, 20 kg of cyclodextrin star derivative, 5 kg of polyvinyl alcohol, and 1 kg of polyoxypropylene triamine T403, mix evenly, and finally add 15 kg of waterborne epoxy resin emulsion HyPer WE 1051 and mix evenly to obtain the anti-dry-wet cycling composite soil stabilizer.

[0052] 3) Mix 10 kg of Portland cement with a strength grade of 42.5 evenly with 100 kg of soil, add 0.3 kg of the above anti-dry-wet cycling composite soil stabilizer and mix evenly. Add water to adjust the moisture content of the mixed soil to 20 wt%, and then spread it on the surface and compact it with a roller.

[0053] Comparative Example 1

[0054] The rest is the same as in Example 1, except that there is no step 1), and in step 2), the cyclodextrin star derivative is replaced with an equal mass of anionic polyacrylamide.

[0055] Comparative Example 2

[0056] The rest is the same as in Example 1, except that in step 1), the methoxypolyethylene glycol with a weight-average molecular weight of 1500 is replaced with an equimolar amount of methoxypolyethylene glycol with a weight-average molecular weight of 750.

[0057] Comparative Example 3

[0058] The rest is the same as in Example 1, except that in step 1), the methoxypolyethylene glycol with a weight-average molecular weight of 1500 is replaced with an equimolar amount of methoxypolyethylene glycol with a weight-average molecular weight of 2000.

[0059] The solidified soil prepared in the above examples and comparative examples was subjected to the following performance tests after standard curing for 28 days:

[0060] Unconfined compressive strength: tested in accordance with standard CJ / T486-2015 Soil Stabilization Admixtures.

[0061] Wet-dry cycle test: The unconfined compressive strength after 50 wet-dry cycles is used as an indicator to measure the resistance to wet-dry effects. One wet-dry cycle means soaking in water for 12 hours, then naturally drying at room temperature for 12 hours, and repeating this 50 times. The unconfined compressive strength is retested and the strength retention rate is calculated.

[0062] Water stability coefficient: It characterizes the water resistance of the stabilized soil. A high water stability coefficient means that the stabilized soil is not easy to soften, deform or crack when it comes into contact with water or is in a humid environment, and can maintain good stability. It is tested with reference to the standard CJ / T486-2015 Soil Stabilization Admixture, and the ratio of the unconfined compressive strength of the stabilized soil specimen immersed in water on the last day of the standard curing age of 7 days to the unconfined compressive strength of the specimen of the same age that has not been immersed in water is adopted.

[0063] Table 1 Project test results

[0064] .

[0065] It can be seen from the performance test results in Table 1 that the soil solidifier of the present invention can effectively improve the strength and water stability of the soil and improve the soil's ability to resist dry-wet cycles.

[0066] The above detailed description is a specific description of one feasible embodiment of the present invention. The embodiment is not intended to limit the patent scope of the present invention. Any equivalent implementation or modification that does not deviate from the present invention should be included in the scope of the technical solution of the present invention.

Claims

1. A composite soil solidifier resistant to dry-wet cycles, characterized in that: The invention comprises the following raw materials: 5-10 parts by weight of polyacrylamide, 20-30 parts by weight of cyclodextrin star derivatives, 5-10 parts by weight of polyvinyl alcohol, 5-8 parts by weight of inorganic salts, 5-8 parts by weight of sodium silicate, 10-15 parts by weight of waterborne epoxy resin emulsion, 1-3 parts by weight of polyoxypropylene triamine and water, wherein the amount of water used makes the solid content of the anti-wet-dry cycle composite soil curing agent be 25-60wt%; the cyclodextrin star derivative is prepared by esterification reaction of carboxymethyl-β-cyclodextrin and polyethylene glycol monomethyl ether under the action of an alkali catalyst according to a carboxyl group:hydroxyl group molar ratio of 1:1.1-1.2; the polyethylene glycol monomethyl ether has a weight average molecular weight of 1000-1500g / mol; the waterborne epoxy resin emulsion has a solid content of 40-50wt%, and an epoxy value of 0.20-0.25mol / 100g.

2. The anti-dry-wet cycle composite soil solidifier according to claim 1, characterized in that: The average degree of substitution DS of the carboxymethyl-β-cyclodextrin is 0.9-1.

2.

3. The anti-dry-wet cycle composite soil solidifier according to claim 1, characterized in that: The cyclodextrin star derivative is prepared by a method comprising the following steps: Carboxymethyl-β-cyclodextrin, polyethylene glycol monomethyl ether and alkali catalyst are added to a reaction kettle and mixed evenly for reaction. An inert gas water method is used for esterification reaction. After the reaction is completed, impurities are removed by reduced pressure distillation to obtain a cyclodextrin star derivative.

4. The anti-dry-wet cycle composite soil solidifier according to claim 1, characterized in that: The amount of the base catalyst is 1-2wt% of the sum of the mass of carboxymethyl-β-cyclodextrin and polyethylene glycol monomethyl ether; the base catalyst is selected from one or a combination of two or more of sodium hydroxide, potassium hydroxide, and sodium methoxide; the esterification reaction conditions are to react at 150-200°C for 12-24h.

5. The anti-dry-wet cycle composite soil solidifier according to claim 1, characterized in that: The weight average molecular weight of the polyoxypropylene triamine is 300-500 g / mol, and the amine value is 6.1-6.6 meq / g.

6. The method for preparing the anti-dry-wet cycle composite soil solidifier according to any one of claims 1 to 5, characterized in that: The steps include: Add water to the reactor and heat it up, add inorganic salt and sodium silicate and mix evenly, add polyacrylamide, cyclodextrin star derivative, polyvinyl alcohol and polyoxypropylene triamine and mix evenly, finally add water-based epoxy resin emulsion and mix evenly to obtain a composite soil curing agent resistant to dry-wet cycles.

7. The use of the anti-dry-wet cycle composite soil solidifier according to any one of claims 1 to 5, characterized in that: The steps include: The cementitious material is mixed evenly with the soil, the anti-dry-wet cycle composite soil solidifying agent is added and mixed evenly, water is added to adjust the moisture content of the mixed soil, and then the mixed soil is spread on the surface and compacted with a roller.

8. The use of the anti-dry-wet cycle composite soil solidifier according to claim 7, characterized in that: The soil has a moisture content of 5-60%, a liquid limit of 40-50%, a plastic limit of 20-30%, and a clay content of 20-30% with an average particle size of less than 2 μm.

9. The use of the anti-dry-wet cycle composite soil solidifier according to claim 7, characterized in that: The cementitious material is selected from one or a combination of two or more of fly ash, lime and cement.

10. The use of the anti-dry-wet cycle composite soil solidifier according to claim 7, characterized in that: The mass ratio of the anti-wet-dry cycle composite soil solidifier, the cementitious material and the soil is 0.05-0.5:3-15:100; the moisture content of the adjusted mixed soil is adjusted to 13-20wt%.