Composite curing agent, preparation method and application thereof

Abstract

The application belongs to the technical field of curing agents, and particularly relates to a composite curing agent and a preparation method and application thereof. The composite curing agent comprises the following raw materials in parts by weight: gravel 40-50 parts, cement 20-30 parts, quicklime 5-10 parts, activator 4-10 parts, modified bentonite 3-8 parts, and anti-cracking agent 0.3-0.5 parts. The preparation process of the modified bentonite is as follows: (1) the pretreated bentonite is added into an ethanol aqueous solution, then KH570 is added, and the mixture is stirred and reacted under heating to obtain pre-modified bentonite; (2) the pre-modified bentonite is taken and added into N,N-dimethylformamide, then diallyl malate and an initiator are added, and the mixture is heated and reacted to obtain the modified bentonite. The composite curing agent can significantly improve the mechanical properties and anti-cracking durability of the cured soil body.

Description

Technical Field

[0001] This invention belongs to the field of curing agent technology, specifically relating to a composite curing agent, its preparation method, and its application. Background Technology

[0002] Using construction waste soil as roadbed filling material is one of the effective ways to dispose of construction waste. However, construction waste soil usually has undesirable engineering characteristics such as high water content, low bearing capacity, and easy deformation, making it difficult to directly meet the technical requirements of roadbed for strength, stability, and durability. To improve its engineering performance, researchers have proposed using solidifying agents to improve the waste soil. Through the hydration reaction, ion exchange, and filling effect of the solidifying agent, the compaction and mechanical strength of the soil can be effectively improved.

[0003] Existing curing agents are mostly based on inorganic cementitious materials such as cement and lime. Although they can improve the strength of soil to a certain extent, they still have the following shortcomings: First, the early strength development of the cured soil is slow and the tendency to crack is obvious; second, they have poor adaptability to abandoned soil with high moisture content or containing organic matter, and the curing effect is unstable; third, they lack systematic optimization of the bonding force between soil particles, making it difficult to give full play to the overall effectiveness of the curing agent.

[0004] In recent years, the theory of soil surface energy has provided new insights for the design of curing agents. This theory posits that the interaction forces between soil particles are closely related to their surface energy. By introducing modified materials with high reactivity and adsorption capabilities, the interfacial bonding forces between particles can be enhanced, thereby improving the compressive strength and deformation resistance of the cured soil. Simultaneously, introducing reinforcing components such as crack-resistant fibers into the curing system is also an important means of suppressing shrinkage cracks and improving durability.

[0005] Therefore, developing a composite curing agent that combines high strength, crack resistance, and good adaptability is of great practical significance for promoting the efficient resource utilization of construction waste in roadbed engineering. Summary of the Invention

[0006] In order to overcome the shortcomings of the prior art, the first objective of the present invention is to provide a composite curing agent that can significantly improve the mechanical properties and crack resistance and durability of the cured soil.

[0007] The second objective of this invention is to provide a simple method for preparing a composite curing agent.

[0008] The third objective of this invention is to provide a composite curing agent with broad application prospects.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A composite curing agent comprises the following raw materials in parts by weight: 40-50 parts crushed stone, 20-30 parts cement, 5-10 parts quicklime, 4-10 parts activator, 3-8 parts modified bentonite, and 0.3-0.5 parts crack-resistant agent;

[0011] The preparation process of the modified bentonite is as follows:

[0012] (1) Add the pretreated bentonite to an ethanol aqueous solution, then add KH570, and stir the reaction under heating conditions to obtain pre-modified bentonite;

[0013] (2) Take the pre-modified bentonite and add it to N,N-dimethylformamide, then add diallyl malate and an initiator, heat and react to obtain the modified bentonite.

[0014] Furthermore, in step (2), the mass ratio of the pre-modified bentonite, diallyl malate, and initiator is 1:(0.1-0.2):(0.005-0.01); the initiator is azobisisobutyronitrile; the heating temperature is 80-90℃, and the reaction time is 3-5h.

[0015] Furthermore, in step (1), the mass ratio of the pretreated bentonite to KH570 is 1:(0.1-0.2); the heating and stirring reaction temperature is 60-70℃, and the time is 1-2h.

[0016] Furthermore, the pretreated bentonite is as follows:

[0017] With a mass ratio of chitosan to bentonite of 1:(2-3), bentonite and chitosan were added to deionized water, ball-milled, and dried to obtain the pretreated bentonite.

[0018] Furthermore, the preparation process of the crack-resistant agent is as follows:

[0019] Pretreated corn stalk fiber was added to N-methylpyrrolidone, and then sodium 2-bromoethylsulfonate and potassium carbonate were added to react and obtain the crack-resistant agent.

[0020] Furthermore, the mass ratio of the pretreated corn stalk fiber, sodium 2-bromoethylsulfonate, and potassium carbonate is 1:(0.3-0.5):(0.02-0.04); the reaction temperature is 70-80℃, and the reaction time is 4-6h.

[0021] Furthermore, the method for preparing the pretreated corn stalk fiber is as follows:

[0022] Corn stalk fiber is added to sodium hydroxide solution, soaked, washed, filtered, and dried to obtain the pretreated corn stalk fiber.

[0023] Furthermore, the activator is composed of water glass and sodium carbonate in a mass ratio of 1:(0.3-0.5).

[0024] The preparation method of the above-mentioned composite curing agent includes the following steps:

[0025] Simply mix crushed stone, cement, quicklime, modified bentonite, and crack-resistant agent, then add an activator.

[0026] The above-mentioned composite curing agent is used in soil solidification.

[0027] The beneficial technical effects of this invention are as follows:

[0028] 1. This invention provides a curing agent made from crushed stone, cement, quicklime, modified bentonite, crack-resistant agent, and activator, which can significantly improve the mechanical properties and crack resistance and durability of the cured soil.

[0029] 2. This invention improves the mechanical properties of solidified soil by adding modified bentonite. Specifically, the invention first uses chitosan intercalation modification and ball milling pretreatment to effectively increase the interlayer spacing of bentonite, improving its dispersion uniformity and surface reactivity. Then, silane coupling agent KH570 is used to modify the surface of the pretreated bentonite, introducing polymerizable double bond active sites on its surface. Next, diallyl malate is used as a crosslinking modifying monomer, and under the initiation of azobisisobutyronitrile (AIBN), it undergoes a free radical graft copolymerization reaction with the double bonds on the bentonite surface, forming an organic crosslinked layer on the bentonite surface. This facilitates water loss during the solidification process, reduces internal voids, increases solidification density, and improves mechanical strength. Simultaneously, it has a good adsorption and stabilizing effect on metal ions in the soil, improving the binding force of soil particles and achieving high-strength solidification of construction waste soil.

[0030] 3. This invention improves the mechanical properties and crack resistance of solidified soil by adding an anti-crack agent. Specifically, corn stalk fibers are alkali-activated and covalently grafted with sodium 2-bromoethylsulfonate, introducing stable sulfonic acid groups on the fiber surface. These groups act as a fiber phase, inhibiting cracking and toughening, thus increasing the unconfined compressive strength of the soil. Stable sulfonic acid ether bonds are formed on the fiber surface, significantly improving alkali resistance. This resists the erosion of the alkaline environment generated during cement hydration, preventing fiber degradation and breakage in the solidified soil, and significantly enhancing the mechanical properties and crack resistance of the solidified soil. Attached Figure Description

[0031] Figure 1 This is a SEM image of the modified bentonite prepared in Example 1;

[0032] Figure 2 This is a SEM image of the crack-resistant agent prepared in Example 4. Detailed Implementation

[0033] The following is a further detailed description of the present invention in conjunction with specific preferred embodiments, and it should not be construed that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, various simple deductions or substitutions can be made without departing from the concept of the present invention, and all such modifications and substitutions should be considered within the scope of protection of the present invention. Specific conditions not specified in the embodiments are performed according to conventional conditions or conditions recommended by the manufacturer. Unless otherwise specified, all reagents or instruments used are conventional products obtained through commercial channels.

[0034] In the examples, the average particle size of the crushed stone is 5-10 mm; the cement is P.O42.5 ordinary Portland cement; the average particle size of the quicklime is 45-200 μm; and the average diameter of the corn stalk fiber is 0.1-0.3 mm.

[0035] Example 1

[0036] Example 1 provides a modified bentonite, prepared by the following method:

[0037] (1) Bentonite and chitosan were added to deionized water at a mass ratio of 1:2.5, stirred at 360 rpm for 40 min, and then ball-milled at 400 rpm for 10 h. The pretreated bentonite was dried at 60 °C. The pretreated bentonite was added to a 75% ethanol aqueous solution at a mass ratio of 1:0.15, and then KH570 was added. The mixture was reacted at 65 °C for 1.5 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the pre-modified bentonite.

[0038] (2) Using pre-modified bentonite, diallyl malate, and azobisisobutyronitrile in a mass ratio of 1:0.15:0.007, the pre-modified bentonite was added to N,N-dimethylformamide (DMF), followed by diallyl malate and azobisisobutyronitrile. The mixture was reacted at 85°C for 4 hours. After the reaction was complete, the mixture was filtered, washed, and dried to obtain the modified bentonite. See the SEM image of the modified bentonite for details. Figure 1 .

[0039] Example 2

[0040] Example 2 provides a modified bentonite, prepared by the following method:

[0041] (1) Bentonite and chitosan were added to deionized water at a mass ratio of 1:2, stirred at 360 rpm for 40 min, and then ball-milled at 400 rpm for 10 h. The pretreated bentonite was dried at 60 °C. The pretreated bentonite was added to a 75% ethanol aqueous solution at a mass ratio of 1:0.1, and then KH570 was added. The mixture was reacted at 60 °C for 2 h. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the premodified bentonite.

[0042] (2) With a mass ratio of 1:0.1:0.005, pre-modified bentonite, diallyl malate, and azobisisobutyronitrile were added to DMF, diallyl malate and azobisisobutyronitrile were added, and the mixture was reacted at 80°C for 5 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified bentonite.

[0043] Example 3

[0044] Example 3 provides a modified bentonite, prepared by the following method:

[0045] (1) Bentonite and chitosan were added to deionized water at a mass ratio of 1:3, stirred at 360 rpm for 40 min, and then ball-milled at 400 rpm for 10 h. The pretreated bentonite was dried at 60 °C. The pretreated bentonite was added to a 75% ethanol aqueous solution at a mass ratio of 1:0.2, and then KH570 was added. The mixture was reacted at 70 °C for 1 h. After the reaction was completed, the mixture was filtered, washed and dried to obtain the premodified bentonite.

[0046] (2) With a mass ratio of 1:0.2:0.01, pre-modified bentonite, diallyl malate, and azobisisobutyronitrile were added to DMF, diallyl malate and azobisisobutyronitrile were added, and the mixture was reacted at 90°C for 3 hours. After the reaction was completed, the mixture was filtered, washed, and dried to obtain the modified bentonite.

[0047] Example 4

[0048] Example 4 provides a crack-resistant agent, the preparation process of which is as follows:

[0049] Corn stalk fiber was soaked in a 5 wt% sodium hydroxide solution for 8 hours, washed with hydrochloric acid solution until the pH was neutral, filtered, and dried to obtain the pretreated corn stalk fiber. The pretreated corn stalk fiber, sodium 2-bromoethylsulfonate, and potassium carbonate were added to N-methylpyrrolidone in a mass ratio of 1:0.4:0.03, followed by the addition of sodium 2-bromoethylsulfonate and potassium carbonate. The mixture was reacted at 75°C for 5 hours. After the reaction was complete, it was filtered and dried to obtain the crack-resistant agent. SEM images of the crack-resistant agent are shown below. Figure 2 .

[0050] Example 5

[0051] Example 5 provides a crack-resistant agent, the preparation process of which is as follows:

[0052] Corn stalk fiber was added to a 5 wt% sodium hydroxide solution and soaked for 8 hours. It was then washed with hydrochloric acid solution until the pH was neutral, filtered, and dried to obtain the pretreated corn stalk fiber. The pretreated corn stalk fiber, sodium 2-bromoethylsulfonate, and potassium carbonate were added to N-methylpyrrolidone in a mass ratio of 1:0.3:0.02. Then, sodium 2-bromoethylsulfonate and potassium carbonate were added, and the mixture was reacted at 70°C for 6 hours. After the reaction was completed, the mixture was filtered and dried to obtain the crack-resistant agent.

[0053] Example 6

[0054] Example 6 provides a crack-resistant agent, the preparation process of which is as follows:

[0055] Corn stalk fiber was added to a 5 wt% sodium hydroxide solution and soaked for 8 hours. It was then washed with hydrochloric acid solution until the pH was neutral, filtered, and dried to obtain the pretreated corn stalk fiber. The pretreated corn stalk fiber, sodium 2-bromoethylsulfonate, and potassium carbonate were added to N-methylpyrrolidone in a mass ratio of 1:0.5:0.04. Then, sodium 2-bromoethylsulfonate and potassium carbonate were added, and the mixture was reacted at 80°C for 4 hours. After the reaction was completed, the mixture was filtered and dried to obtain the crack-resistant agent.

[0056] Example 7

[0057] Example 7 provides a composite curing agent comprising the following raw materials in parts by weight: 44 parts crushed stone, 27 parts cement, 8 parts quicklime, 9 parts activator, 6 parts modified bentonite from Example 1, and 0.4 parts crack-resistant agent from Example 4.

[0058] Example 7 also provides a method for preparing the above-mentioned composite curing agent, comprising the following steps:

[0059] Mix the crushed stone, cement, quicklime, modified bentonite, and crack-resistant agent for 15 minutes, then add the activator and continue mixing for 30 minutes.

[0060] Example 8

[0061] Example 8 provides a composite curing agent comprising the following raw materials in parts by weight: 40 parts crushed stone, 20 parts cement, 5 parts quicklime, 4 parts activator, 3 parts modified bentonite from Example 2, and 0.3 parts crack-resistant agent from Example 5.

[0062] Example 8 also provides a method for preparing the above-mentioned composite curing agent, comprising the following steps:

[0063] Mix the crushed stone, cement, quicklime, modified bentonite, and crack-resistant agent for 15 minutes, then add the activator and continue mixing for 30 minutes.

[0064] Example 9

[0065] Example 9 provides a composite curing agent comprising the following raw materials in parts by weight: 50 parts crushed stone, 30 parts cement, 10 parts quicklime, 10 parts activator, 8 parts modified bentonite from Example 3, and 0.5 parts crack-resistant agent from Example 6.

[0066] Example 9 also provides a method for preparing the above-mentioned composite curing agent, comprising the following steps:

[0067] Mix the crushed stone, cement, quicklime, modified bentonite, and crack-resistant agent for 15 minutes, then add the activator and continue mixing for 30 minutes.

[0068] Comparative Example 1

[0069] The difference between Comparative Example 1 and Example 7 is that pre-modified bentonite is used instead of the modified bentonite in Example 1, and the preparation method of the pre-modified bentonite is the same as that in Example 1.

[0070] Comparative Example 2

[0071] The difference between Comparative Example 2 and Example 7 is that a mixture of pre-modified bentonite and diallyl malate was used instead of the modified bentonite in Example 1, and the ratio of pre-modified bentonite to diallyl malate was the same as in Example 1.

[0072] Comparative Example 3

[0073] The difference between Comparative Example 3 and Example 7 is that corn stalk fiber was used instead of the crack-resistant agent in Example 4.

[0074] Example of effect

[0075] The soil samples used in the experiment were taken from a construction site. The soil samples were dried, crushed, and sieved through a 4.75mm sieve. Basic physical properties were tested according to the "Specifications for Geotechnical Testing of Highways JTGE40-2007," and the results are shown in Table 1. A curing agent (based on the examples or comparative examples) was added to the soil samples at an 8wt% concentration to form 50mm × 50mm cylindrical specimens. These specimens were statically compacted at the optimum moisture content, achieving a compaction degree of 95%. Curing was performed for 7 days and 28 days according to the standard of JTG 3441-2024 "Specifications for Testing Inorganic Binder Stabilized Materials in Highway Engineering." The samples from the same group were divided into two subgroups. One subgroup's samples were soaked in water one day in advance, and their unconfined compressive strength was tested after 24 hours. The other subgroup's samples were cured according to standard conditions until the desired age, and their unconfined compressive strength was then tested. The axial strain rate was controlled at 1mm / min, and the results are shown in Table 2.

[0076] Crack resistance and durability test: After standard curing for 28 days, the test sample was soaked in water (20±2℃) for 24 hours, then frozen in a refrigerator at -18℃ for 24 hours, and then placed in a constant temperature chamber at 20℃ for 24 hours. This was recorded as one freeze-thaw cycle. This cycle was repeated 10 times. The unconfined compressive strength was retested, and the strength retention rate was calculated. The results are shown in Table 2.

[0077] Table 1

[0078]

[0079] Table 2

[0080]

[0081] As can be seen from Table 2, the curing agent obtained in the examples can significantly improve the mechanical properties and crack resistance and durability of the cured soil.

[0082] Compared with Comparative Examples 1-2, the curing agent obtained in Example 1 can improve the mechanical properties of the cured soil. The above experimental results show that modified bentonite can improve the mechanical properties of cured soil. Specifically, the present invention first uses chitosan intercalation modification and ball milling pretreatment to effectively increase the interlayer spacing of bentonite, improve its dispersion uniformity and surface reactivity; the pretreated bentonite is surface modified with silane coupling agent KH570 to introduce polymerizable double bond active sites on its surface, and then diallyl malate is used as a crosslinking modification monomer to undergo free radical graft copolymerization reaction with the double bonds on the bentonite surface under the initiation of azobisisobutyronitrile, forming an organic crosslinked layer on the bentonite surface. This is beneficial to the water loss of the soil during the curing process, reduces internal voids, increases the curing density, and improves mechanical strength. At the same time, it has a good adsorption and stabilizing effect on metal ions in the soil, improves the binding force of soil particles, and achieves high-strength curing of construction waste soil.

[0083] Compared with Comparative Example 3, the curing agent obtained in Example 1 can improve the mechanical properties and crack resistance durability of the solidified soil. The above experimental results demonstrate that the crack-resistant agent can improve the mechanical properties and crack resistance durability of the solidified soil. Specifically, corn stalk fibers are alkali-activated and covalently grafted with sodium 2-bromoethylsulfonate, introducing stable sulfonic acid groups on the fiber surface. These groups act as a fiber phase, inhibiting cracking and toughening, thus improving the unconfined compressive strength of the soil. Stable sulfonic acid ether bonds are formed on the fiber surface, significantly improving alkali resistance. This resists the erosion of the alkaline environment generated during cement hydration, preventing fiber degradation and breakage in the solidified soil, and significantly improving the mechanical properties and crack resistance durability of the solidified soil.

[0084] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. The basic principles and main features of the present invention have been described above with specific implementation schemes. Based on the present invention, some modifications or substitutions can be made, but these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of protection claimed by the present invention.

Claims

1. A composite curing agent, characterized in that, The raw materials include the following parts by weight: 40-50 parts crushed stone, 20-30 parts cement, 5-10 parts quicklime, 4-10 parts activator, 3-8 parts modified bentonite, and 0.3-0.5 parts crack-resistant agent; The preparation process of the modified bentonite is as follows: (1) Add the pretreated bentonite to an ethanol aqueous solution, then add KH570, and stir the reaction under heating conditions to obtain pre-modified bentonite; (2) Take the pre-modified bentonite and add it to N,N-dimethylformamide, then add diallyl malate and an initiator, heat and react to obtain the modified bentonite; The preparation process of the crack-resistant agent is as follows: Pretreated corn stalk fiber was added to N-methylpyrrolidone, and then sodium 2-bromoethylsulfonate and potassium carbonate were added to react and obtain the crack-resistant agent.

2. The composite curing agent as described in claim 1, characterized in that, In step (2), the mass ratio of the pre-modified bentonite, diallyl malate, and initiator is 1:(0.1-0.2):(0.005-0.01); the initiator is azobisisobutyronitrile; the heating reaction temperature is 80-90℃ and the time is 3-5h.

3. The composite curing agent as described in claim 1, characterized in that, In step (1), the mass ratio of the pretreated bentonite to KH570 is 1:(0.1-0.2); the heating temperature is 60-70℃, and the reaction time is 1-2h.

4. The composite curing agent as described in claim 3, characterized in that, The pretreated bentonite is as follows: With a mass ratio of chitosan to bentonite of 1:(2-3), bentonite and chitosan were added to deionized water, ball-milled, and dried to obtain the pretreated bentonite.

5. The composite curing agent as described in claim 1, characterized in that, The mass ratio of the pretreated corn stalk fiber, sodium 2-bromoethylsulfonate, and potassium carbonate is 1:(0.3-0.5):(0.02-0.04); the reaction temperature is 70-80℃ and the reaction time is 4-6h.

6. The composite curing agent as described in claim 5, characterized in that, The method for preparing the pretreated corn stalk fiber is as follows: Corn stalk fiber was added to a sodium hydroxide solution, soaked, washed, filtered, and dried to obtain the pretreated corn stalk fiber.

7. The composite curing agent as described in claim 1, characterized in that, The activator is composed of water glass and sodium carbonate in a mass ratio of 1:(0.3-0.5).

8. A method for preparing a composite curing agent as described in any one of claims 1-7, characterized in that, Includes the following steps: Simply mix crushed stone, cement, quicklime, modified bentonite, and crack-resistant agent, then add an activator.

9. An application of the composite curing agent as described in any one of claims 1-7, characterized in that, Application in soil solidification.

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