A solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization

Abstract

This invention discloses a solvent-free hydrophobic soil modification method based on temperature control and multi-stage homogenization. In the soil modification process, a solvent-free molten stearic acid direct impregnation modification method is adopted, without introducing organic dispersion media, which effectively reduces the safety risks and process interference caused by dispersion media, and reduces the influence of dispersion media on the soil modification process and the final coating state. Furthermore, by constructing a temperature-controlled multi-stage homogenization process, this invention enables stearic acid to achieve effective spreading, redistribution and stable fixation under solvent-free conditions, improving the problems of local enrichment, adhesion and agglomeration and uneven coating.

Description

Technical Field

[0001] This invention belongs to the field of soil hydrophobic modification technology, specifically a solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization. Background Technology

[0002] Collapsible loess and other unsaturated soils are prone to structural deterioration, strength reduction, and additional deformation under the infiltration of water, which in turn adversely affects the safety and stability of foundations, slopes, and related geotechnical engineering structures. Using fatty acids or other hydrophobic components to modify soil or granular materials for hydrophobicity is a common technical means to solve the problem of water infiltration in soil.

[0003] However, existing technical solutions generally have the following shortcomings: First, they rely heavily on the application of organic solvents, emulsions, or other dispersion media to assist the modifier, resulting in a relatively cumbersome process flow; second, the introduction of dispersion media increases the requirements for volatilization control, safety management, and process stability; third, without the use of dispersion media, the molten hydrophobic components are prone to local enrichment, agglomeration, and uneven coating in the soil particle system, making it difficult to simultaneously achieve the process simplification advantages of solvent-free modification and the technical requirements of uniform modification. Summary of the Invention

[0004] The purpose of this invention is to provide a solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides the following technical solution: a solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization, comprising the following steps: S1: Place the soil to be modified, as well as the mixing equipment, grinding equipment, and sample container in an oven for preheating treatment, while heating the stearic acid to a molten state. S2: Take out the preheated soil to be modified, mixing equipment and molten stearic acid, and add the molten stearic acid to the soil to be modified under continuous stirring to obtain the initial mixed modified soil; S3: After grinding the initial modified soil in a grinding pan, it is sieved. The unsieved portion is ground again, and the sieved portion is mixed with the ground soil to obtain homogenized modified soil. S4: Place the homogenized modified soil in an oven and heat it at 105℃~110℃ for 3 hours. After heating and curing, take it out and stir it thoroughly once. Then continue to heat and cure for another 3 hours to obtain hydrophobic modified soil.

[0006] Furthermore, in step S1, the amount of stearic acid doped is 1% to 5% of the mass of the soil to be modified.

[0007] Furthermore, in step S1, the preheating temperature of the mixing apparatus, grinding apparatus, and sample container is 75℃-80℃ to reduce the possibility of local condensation and adhesion enrichment when molten stearic acid comes into contact with the low-temperature surface of the apparatus.

[0008] Furthermore, in step S1, the preheating temperature of the soil to be modified is 105°C to remove excess moisture from the soil.

[0009] Furthermore, in step S2, the stearic acid is heated to 80℃~105℃ and kept in a molten state, and then added to the soil to be modified in 2~3 portions within 60s. After the stearic acid is added, the mixture is stirred rapidly for 180s.

[0010] Furthermore, in step S3, the sieve used for screening is consistent with the sieve grade used for controlling the initial particle size of the soil to be modified.

[0011] Compared with the prior art, the beneficial effects of the present invention are: 1. This invention does not introduce organic dispersion media during the application of hydrophobic agents, thus reducing the safety risks and process interference caused by dispersion media; 2. This invention employs a solvent-free molten stearic acid direct impregnation modification route, reducing the influence of the dispersion medium on the modification process and the final coating state; 3. This invention improves the problems of local enrichment, agglomeration and uneven coating by constructing a temperature-controlled multi-stage homogenization process, which enables stearic acid to be effectively spread, redistributed and stably fixed under solvent-free conditions. Attached Figure Description

[0012] Figure 1 This is a diagram of the segmented drip infiltration test of hydrophobic modified soil provided in an embodiment of the present invention; Figure 2 This is a graph showing the relationship between the amount of stearic acid added and the apparent contact angle of the hydrophobically modified soil, as provided in the embodiments of the present invention. Figure 3 This is a graph showing the relationship between the amount of stearic acid added and the collapsibility coefficient of hydrophobically modified soil provided in the embodiments of the present invention. Detailed Implementation

[0013] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0014] Please see Figures 1-3This invention provides a technical solution: a solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization, comprising the following steps: S1: Preheating, dehumidification, and molten activation: The soil to be modified, along with mixing, grinding, and sample-holding containers, are placed in an oven for preheating treatment, while stearic acid is heated to a molten state. The amount of stearic acid added is 1% to 5% of the mass of the soil to be modified. The preheating temperature of the mixing, grinding, and sample-holding containers is 75℃-80℃ to reduce the possibility of local condensation and adhesion enrichment when the molten stearic acid comes into contact with the low-temperature surface of the containers. The preheating temperature of the soil to be modified is 105℃ to remove excess moisture from the soil. By preheating the soil to be modified and related containers separately, the local condensation and adhesion enrichment caused by temperature difference during the application of molten stearic acid are reduced, and the influence of excess moisture in the undisturbed soil on the subsequent modification process is reduced.

[0015] S2: Staged impregnation and primary homogenization: Take out the preheated soil to be modified, mixing equipment, and molten stearic acid. Heat the stearic acid to 80℃~105℃ and keep it in a molten state. Under continuous stirring, add the molten stearic acid to the soil to be modified in 2~3 portions within 60s. After the stearic acid is added, continue to mix rapidly for 180s to obtain the initial mixed modified soil. In this step, the molten stearic acid is not pre-dispersed with ethanol or other organic solvents and is directly applied to the soil particle system as a hydrophobic modifying component. Primary homogenization is formed by staged addition and rapid mixing, so that the molten stearic acid can achieve initial spreading and initial coating within a larger particle range.

[0016] S3: Grinding, deagglomeration, and secondary homogenization: The initially mixed modified soil is placed in a grinding pan and ground thoroughly, then sieved. The unsieved portion is ground again, and the soil after the second grinding is mixed with the sieved portion to obtain homogenized modified soil. The sieve used for sieving is consistent with the sieve grade used for controlling the initial particle size of the soil to be modified.

[0017] S4: Heat curing and three-stage homogenization: The homogenized modified soil is placed in an oven and heated at 105℃~110℃ for 3 hours. After heating and curing, it is taken out and stirred thoroughly once, and then heated and cured for another 3 hours to obtain hydrophobic modified soil. In this step, the heat curing causes stearic acid to migrate, spread, rearrange and gradually fix on the particle surface. The process of taking out and stirring and homogenizing again in the middle of the curing process forms a three-stage homogenization to reduce the local re-aggregation and uneven rearrangement caused by long-term static conditions, and to promote the further stable fixation of stearic acid on the particle surface.

[0018] In this embodiment, temperature control employs a differentiated setting method based on different working conditions, and is applied throughout the preheating treatment, melt impregnation, and heat curing processes. Specifically, mixing equipment, grinding equipment, and sample containers are preheated at 75℃-80℃ to reduce the possibility of local condensation and adhesion accumulation when molten stearic acid comes into contact with the low-temperature surfaces of the equipment. The soil to be modified is preheated at 105℃ to remove excess moisture and facilitate subsequent moisture content control. The homogenized modified soil is heat-cured at 105℃~110℃ to maintain the modified soil at a low moisture content and promote further migration, spreading, and stable fixation of stearic acid on the surface of soil particles. Through the above-mentioned differentiated temperature control based on working conditions, stearic acid is kept in a state adapted to the process requirements during application, migration, and fixation, and the probability of local condensation, local accumulation, and uneven coating is reduced.

[0019] The graded homogenization process employs a phased, progressive approach, spanning the entire process from the addition of molten stearic acid, grinding, sieving, backmixing, and curing re-mixing. Primary homogenization involves multiple additions and rapid mixing to prevent excessively high local concentrations caused by a single, concentrated addition of molten stearic acid. Secondary homogenization involves grinding to deagglomerate, sieving feedback, and backmixing to break up localized aggregates and correct uneven particle distribution. Tertiary homogenization is achieved through re-mixing during curing to reduce localized re-agglomeration and rearrangement issues that occur under prolonged static conditions. This phased, graded homogenization process gradually improves the distribution of stearic acid on the soil particle surface and enhances the continuity and stability of the coating layer.

[0020] In this embodiment, the obtained modified soil was tested, and the test process and results are as follows: Take 500 g of soil to be modified, and weigh out stearic acid equivalent to 1%, 2%, 3%, 4% and 5% of the mass of the soil to be modified, respectively, and prepare hydrophobic modified soil samples with the corresponding amount of stearic acid added according to the method described in the example; at the same time, use natural soil without added stearic acid as a control group.

[0021] like Figure 1 As shown: A segmented drip infiltration test was conducted on each group of samples to verify the uniformity of soil hydrophobic modification at different locations; simultaneously, the apparent contact angle of water droplets on the sample surface was measured, and the results are as follows. Figure 2 As shown. By Figure 1 It can be seen that the hydrophobic modified soil prepared by the solvent-free molten stearic acid impregnation and temperature-controlled multi-stage homogenization process described in this invention exhibits basically consistent drip infiltration behavior in each compartment, indicating that the sample has good modification uniformity. Figure 2 It can be seen that as the amount of stearic acid added increases from 1% to 5%, the apparent contact angle of the sample gradually increases, indicating that the hydrophobicity gradually improves; when the amount of stearic acid added is 5%, the apparent contact angle reaches 146.9°, and the improved soil has excellent hydrophobicity.

[0022] The collapsibility coefficient of each group of samples was further tested, and the results are as follows: Figure 3 As shown, the collapsibility coefficient of the natural soil is 0.1125; as the amount of stearic acid added increases from 1% to 5%, the collapsibility coefficient of the hydrophobic modified soil gradually decreases, indicating that the soil collapsibility gradually weakens; when the amount of stearic acid added is 5%, the collapsibility coefficient drops to 0.012.

[0023] The above test results show that the solvent-free molten stearic acid impregnation modification route adopted in this invention can achieve effective hydrophobic modification without introducing organic dispersion media. The temperature-controlled multi-stage homogenization process further improves the uniformity of distribution and coating stability of molten stearic acid on the surface of soil particles, so that the modified soil exhibits both high hydrophobicity and low collapsibility.

[0024] Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization, characterized in that, Includes the following steps: S1: Place the soil to be modified, as well as the mixing equipment, grinding equipment, and sample container in an oven for preheating treatment, while heating the stearic acid to a molten state. S2: Take out the preheated soil to be modified, mixing equipment and molten stearic acid, and add the molten stearic acid to the soil to be modified under continuous stirring to obtain the initial mixed modified soil; S3: After grinding the initial modified soil in a grinding pan, it is sieved. The unsieved portion is ground again, and the sieved portion is mixed with the ground soil to obtain homogenized modified soil. S4: Place the homogenized modified soil in an oven and heat it at 105℃~110℃ for 3 hours. After heating and curing, take it out and stir it thoroughly once. Then continue to heat and cure for another 3 hours to obtain hydrophobic modified soil.

2. The solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization according to claim 1, characterized in that, In step S1, the amount of stearic acid added is 1% to 5% of the mass of the soil to be modified.

3. The solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization according to claim 1, characterized in that, In step S1, the preheating temperature of the mixing apparatus, grinding apparatus, and sample container is 75℃-80℃ to reduce the possibility of local condensation and adhesion enrichment when molten stearic acid comes into contact with the low-temperature surface of the apparatus.

4. The solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization according to claim 1, characterized in that, In step S1, the preheating temperature of the soil to be modified is 105°C to remove excess moisture from the soil.

5. The solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization according to claim 1, characterized in that, In step S2, the stearic acid is heated to 80℃~105℃ and kept in a molten state. It is then added to the soil to be modified in 2~3 portions within 60s, and after the stearic acid is added, the mixture is rapidly stirred for 180s.

6. The solvent-free soil hydrophobic modification method based on temperature control and multi-stage homogenization according to claim 1, characterized in that, In step S3, the sieve used for screening is the same as the sieve grade used for controlling the initial particle size of the soil to be modified.

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