Dry-wet cycle resistant composite soil stabilizer and preparation method thereof

Abstract

The invention provides a dry-wet cycle resistant composite soil stabilizer and a preparation method thereof. The curing agent is prepared from the following raw materials in parts by weight: 5 to 10 parts of polyacrylamide, 20 to 30 parts of cyclodextrin star derivative, 5 to 10 parts of polyvinyl alcohol, 5 to 8 parts of inorganic salt, 5 to 8 parts of sodium silicate, 10 to 15 parts of waterborne epoxy resin emulsion, 1 to 3 parts of polyoxypropylene triamine and water; the use amount of the water enables the solid content of the dry-wet cycle resistant composite soil stabilizer to be 25-60wt%; the cyclodextrin star derivative is prepared by carrying out esterification reaction on carboxymethyl-beta-cyclodextrin and methoxypolyethylene glycol according to the molar ratio of carboxyl to hydroxyl of 1: (1.1-1.2) under the action of a base catalyst; and the weight-average molecular weight of polyethylene glycol monomethyl ether is 1000 to 1500 g / mol. A plurality of grafting chains of the cyclodextrin star-shaped derivative disperse expansion and shrinkage stress of soil to different directions in the dry-wet cycle process, so that damage to a molecular structure due to stress concentration is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of soil solidifying agents, and in particular 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, soil stabilizers are a new type of green building material, which is widely used due to its remarkable effect in improving soil engineering properties. Due to the low strength and poor stability of natural soil, it is usually difficult to meet engineering needs. Soil stabilizers can significantly improve the strength, bearing capacity and durability of soil through physical, chemical and biological effects, which is crucial for application scenarios such as road engineering, foundation treatment and slope reinforcement engineering.

[0003] Soil stabilizer is a soil hardener that can directly bond the surface of soil particles in the soil at room temperature or react with clay minerals to form cementitious substances. Its essence is to change the surface hydrophobicity and lubricity of the soil so that the soil can be compacted, reduce the channels for water in and out, and continuously improve the strength and water stability. Soil stabilizers can be divided into inorganic, organic, bio-enzyme, composite stabilizers, etc. according to their main components. Composite stabilizers are a new type of solidifying material formed by combining organic and inorganic materials in a certain proportion. Composite curing agents can give full play to the advantages of organic materials and have the advantage of achieving effective modification of soil. At the same time, they can also well avoid the damage caused by poor water stability and poor shrinkage of the structure when using only inorganic materials, so that it can meet the requirements of engineering application technical conditions. In recent years, it has received extensive attention from research and development personnel. For example, patent CN115044382B discloses a soil curing agent, cured soil and its application. The soil curing agent includes 15-20 parts of modified water glass, 10-20 parts of sulfonated oil, 3-5 parts of oleamide, 5-8 parts of triisopropanolamine, 1-2 parts of inorganic salt, 1-3 parts of expansion agent, 2-3 parts of pore sealing agent and 40-60 parts of water. Patent CN101597496B discloses a cement-based soil solidifier and its preparation and application. The prepared soil solidifier is made of the following raw materials and their mass percentages: sodium sulfate: 10%-40%, sodium tripolyphosphate: 2%-6%, carbodiamide: 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%, sodium methyl silicate 2%-8%, and the sum of the percentages of the above raw materials is 100%. Patent CN113149592B discloses an early-strength soil curing agent, a preparation method and an application thereof. The early-strength soil curing agent comprises: 40-80 parts of isocyanate-modified polyvinyl alcohol emulsion; 10-40 parts of anionic surfactant; 3-10 parts of water glass; 3-10 parts of salt compound; 1-5 parts of phenol butanol; 0.5-2 parts of pore sealer; and 10-30 parts of water.

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

[0005] In order 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 large molecular size and is star-shaped. Multiple grafted chains can disperse the expansion and contraction stress of the soil during the dry-wet cycle to different directions, thereby avoiding stress concentration and destroying the molecular structure; in addition, by utilizing the adsorption and intercalation effect of the soil on the grafted chain of the cyclodextrin star derivative - polyvinyl alcohol monomethyl ether, the microscopic pore area of ​​the soil can be significantly reduced, the entry and discharge of water during the dry-wet cycle can be reduced, and the resistance to dry-wet cycles can be further improved; the water-based epoxy resin emulsion has good bonding properties, and can cooperate with the cyclodextrin star derivative to maintain the relative position between particles when the soil shrinks and expands, thereby keeping the soil structure intact.

[0006] In order to achieve the above purpose, the following technical solutions are adopted: A composite soil solidifier resistant to wet-dry cycles 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 is such that the solid content of the composite soil solidifier resistant to wet-dry cycles is 25-60wt%, preferably 40-60wt%; 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 at 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.

[0007] The average degree of substitution DS of the carboxymethyl-β-cyclodextrin is 0.9-1.2, and the average degree of substitution DS represents the average number of substituted hydroxyl groups on each glucose molecule unit.

[0008] 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.

[0009] The amount of the base catalyst is 1-2wt% 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 150-200°C for 12-24h.

[0010] The waterborne epoxy resin emulsion has a solid content of 40-50 wt % and an epoxy value of 0.20-0.25 mol / 100 g.

[0011] 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.

[0012] The polyacrylamide is anionic polyacrylamide with a weight average molecular weight of 8-10 million g / mol.

[0013] The weight average molecular weight of the polyvinyl alcohol is 30,000-60,000 g / mol.

[0014] 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.

[0015] The modulus of the sodium silicate is 2.0-2.4.

[0016] The present invention also provides a method for preparing the above-mentioned anti-dry-wet cycle composite soil solidifying agent, comprising the following steps: 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.

[0017] The temperature is raised to 30-50°C.

[0018] An application of a composite soil solidifying agent resistant to dry-wet cycles comprises the following steps: Mix the cementitious material and soil evenly, add the above-mentioned anti-dry-wet cycle composite soil solidifier 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.

[0019] The soil has a moisture content of 5-60% (preferably 20-30wt%), 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 <2μm. The cementitious 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-wet 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%, preferably 16-20wt%.

[0020] Compared with the prior art, the present invention has the following beneficial effects: The composite soil solidifying agent of the present invention contains a cyclodextrin star derivative grafted with polyvinyl alcohol monomethyl ether, which has a large molecular size and is in a star shape. Multiple grafted chains can disperse the expansion and contraction stress of the soil in the process of dry-wet cycles to different directions, thereby avoiding stress concentration and destroying the molecular structure. In addition, by utilizing the adsorption and intercalation effect of the soil on the grafted chain of the cyclodextrin star derivative - polyvinyl alcohol monomethyl ether, the microscopic pore area of ​​the soil can be significantly reduced, the entry and discharge of water in the process of dry-wet cycles can be reduced, and the anti-dry-wet cycle ability can be further improved. The water-based epoxy resin emulsion has good bonding performance, and can cooperate with the cyclodextrin star derivative to maintain the relative position between particles when the soil shrinks and expands, thereby keeping the soil structure intact. DETAILED DESCRIPTION

[0021] The present invention will be further described below in conjunction with specific embodiments, but is not limited to the contents of the specification. Unless otherwise specified, the "parts" described in the embodiments of the present invention are all parts by weight. The reagents used are all commercially available reagents in the art.

[0022] The weight average molecular weight of polyethylene glycol monomethyl ether is 1000, the product number is E080823, and it was purchased from Anaiji Chemical.

[0023] The weight average molecular weight of polyethylene glycol monomethyl ether is 1500, the number is E082458, and it was purchased from Anaiji Chemical.

[0024] The weight average molecular weight of polyethylene glycol monomethyl ether is 750, the number is E080730, and it was purchased from Anaiji Chemical.

[0025] The weight average molecular weight of polyethylene glycol monomethyl ether is 2000, the product number is E080731, and it was purchased from Anaiji Chemical.

[0026] Waterborne epoxy resin emulsion HyPer WE 1051, with a solid content of 50% and an epoxy value of 0.25 mol / 100 g, was purchased from Wuhan Hyperbranched Resin Technology Co., Ltd.

[0027] The soil moisture content is 22.8%, the liquid limit is 49.0%, the plastic limit is 22.8%, the clay content with an average particle size of less than 2μm is 23.94%, Zhaoquan Town section of Shiheng Expressway.

[0028] The weight average molecular weight of polyvinyl alcohol is 35,000 g / mol, product number ZZS-PVOH-Mw-35K, purchased from Shanghai Zhenzhun Biotechnology Co., Ltd.

[0029] Anionic polyacrylamide was purchased from Henan Kaijie Water Treatment Co., Ltd. with a weight-average molecular weight of 10 million g / mol.

[0030] 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.

[0031] The average degree of substitution DS of carboxymethyl-β-cyclodextrin was 0.9 and it was purchased from Shandong Binzhou Zhiyuan Biological Co., Ltd.

[0032] Example 1 1) 1 mol of carboxymethyl-β-cyclodextrin, 6.93 mol of polyethylene glycol monomethyl ether with a weight average molecular weight of 1500, and the mass of carboxymethyl-β-cyclodextrin and polyethylene glycol monomethyl ether and 2 wt % of sodium hydroxide are added to a reactor and mixed evenly. The temperature is raised to 180° C. for esterification reaction for 12 h. During the reaction, N2 is introduced for protection and to remove the water generated by the reaction to promote the esterification. After the reaction is completed, impurities are removed by reduced pressure distillation to obtain a cyclodextrin star derivative.

[0033] 2) Add 118.5 kg of water (solid content 40%) to the reactor and heat it to 50°C, add 4 kg of calcium sulfate, 4 kg of calcium chloride, and 8 kg of sodium silicate and mix evenly, add 10 kg of anionic polyacrylamide, 30 kg of cyclodextrin star derivative, 5 kg of polyvinyl alcohol, and 3 kg of polyoxypropylene triamine T403 and mix evenly, and finally add 15 kg of water-based epoxy resin emulsion HyPer WE 1051 and mix evenly to obtain a composite soil solidifier that is resistant to dry-wet cycles.

[0034] 3) Mix 15kg of silicate cement with a strength grade of 42.5 with 100kg of soil, add 0.3kg of the above-mentioned anti-dry-wet cycle composite soil solidifier and mix evenly, add water to adjust the moisture content of the mixed soil to 20wt%, then spread it on the surface and compact it with a roller.

[0035] Example 2 The rest is the same as Example 1, except that in step 1), an equimolar amount of polyethylene glycol monomethyl ether with a weight average molecular weight of 1000 is used to replace polyethylene glycol monomethyl ether with a weight average molecular weight of 1500.

[0036] Example 3 The rest is the same as Example 1, except that in step 2), the amount of cyclodextrin star derivative is 20 kg, and the initial amount of water in the reactor is adjusted accordingly to make the solid content 40%.

[0037] Example 4 The rest is the same as Example 1, except that in step 2), the amount of water-based epoxy resin emulsion HyPer WE 1051 used is 10 kg.

[0038] Example 5 The rest is the same as Example 1, except that in step 3), the amount of the anti-dry-wet cycle composite soil solidifying agent is 0.1 kg.

[0039] Example 6 1) 1 mol of carboxymethyl-β-cyclodextrin, 7.56 mol of polyethylene glycol monomethyl ether with a weight average molecular weight of 1000, and the mass of carboxymethyl-β-cyclodextrin and polyethylene glycol monomethyl ether and 2 wt % of sodium hydroxide are added to a reactor and mixed evenly. The temperature is raised to 180° C. for esterification reaction for 12 h. During the reaction, N2 is introduced for protection and to remove the water generated by the reaction to promote the esterification. After the reaction is completed, impurities are removed by reduced pressure distillation to obtain a cyclodextrin star derivative.

[0040] 2) Add 100.5 kg of water (solid content 40%) to the reactor and heat it to 50°C, add 4 kg of calcium sulfate, 4 kg of calcium chloride, and 8 kg of sodium silicate and mix evenly, add 10 kg of anionic polyacrylamide, 20 kg of cyclodextrin star derivatives, 5 kg of polyvinyl alcohol, and 1 kg of polyoxypropylene triamine T403 and mix evenly, and finally add 15 kg of water-based epoxy resin emulsion HyPer WE 1051 and mix evenly to obtain a composite soil curing agent that is resistant to dry-wet cycles.

[0041] 3) Mix 10kg of silicate cement with a strength grade of 42.5 with 100kg of soil, add 0.3kg of the above-mentioned anti-dry-wet cycle composite soil solidifier and mix evenly, add water to adjust the moisture content of the mixed soil to 20wt%, and then spread it on the surface and compact it with a roller.

[0042] Comparative Example 1 The rest is the same as Example 1, except that step 1 is omitted, and step 2) an anionic polyacrylamide of equal mass is used to replace the cyclodextrin star derivative.

[0043] Comparative Example 2 The rest is the same as Example 1, except that in step 1), an equimolar amount of polyethylene glycol monomethyl ether with a weight average molecular weight of 750 is used to replace polyethylene glycol monomethyl ether with a weight average molecular weight of 1500.

[0044] Comparative Example 3 The rest is the same as Example 1, except that in step 1), an equimolar amount of polyethylene glycol monomethyl ether with a weight average molecular weight of 2000 is used to replace polyethylene glycol monomethyl ether with a weight average molecular weight of 1500.

[0045] The solidified soil prepared in the above examples and comparative examples was subjected to the following performance tests after standard curing for 28 days: Unconfined compressive strength: tested in accordance with standard CJ / T486-2015 Soil Stabilization Admixtures.

[0046] 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.

[0047] 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.

[0048] Table 1 Project test results .

[0049] 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.

[0050] 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 weight average molecular weight of the polyethylene glycol monomethyl ether is 1000-1500g / mol.

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 waterborne epoxy resin emulsion has a solid content of 40-50 wt % and an epoxy value of 0.20-0.25 mol / 100 g; the polyoxypropylene triamine has a weight average molecular weight of 300-500 g / mol and an amine value of 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%.