A modified expansive soil and its preparation method and application

Abstract

The present invention discloses a modified expansive soil and a preparation method and application thereof, and belongs to the technical field of soil solidification. The modified expansive soil is composed of the following components in parts by weight: 100 parts by weight of expansive soil; 0-8 parts by weight of phosphoric acid aqueous solution, 0.5-5 parts by weight of sulfonated acetone formaldehyde polycondensate; water; wherein the amount of water used is equal to the amount of water at the optimum moisture content minus the content of water in the phosphoric acid aqueous solution; the concentration of the phosphoric acid aqueous solution is 85.54wt%. The present invention can greatly improve the unconfined compressive strength of soil by selecting sulfonated acetone formaldehyde polycondensate and phosphoric acid aqueous solution as curing agents.

Description

Technical Field

[0001] The invention relates to the technical field of soil solidification, in particular to a modified expansive soil and a preparation method and application thereof. Background Art

[0002] Expansive soil is widely distributed in my country. It has the characteristics of swelling when absorbing water, shrinking when losing water, repeated swelling and shrinking deformation, attenuation of bearing capacity when immersed in water, and development of shrinkage cracks, posing a great hazard to road projects.

[0003] As a new type of green building material, soil solidifier is increasingly valued in the field of civil engineering. This material is mixed with soil and consolidates soil particles by physical, chemical or biological effects, significantly improving the engineering properties of soil, such as strength, stability and durability. Therefore, soil solidifier has been widely used in foundation treatment, road engineering, water conservancy and other fields. However, since expansive soil has a high water content and a high liquid limit in its natural state, the existing technology mainly uses fly ash, cement, etc. to solidify expansive soil, and other mineral materials or inorganic salts need to be added, such as CN113121134A, CN112811861A, etc., and the amount of raw materials is large and the cost is high. Summary of the invention

[0004] In order to solve the problems existing in the prior art, the present invention provides a modified expansive soil and a preparation method and application thereof; the present invention adopts sulfonated acetone formaldehyde condensation product and phosphoric acid as curing agents, and the unconfined compressive strength of the prepared modified expansive soil is greatly improved.

[0005] In order to solve the above technical problems, the present invention provides the following technical solutions:

[0006] In one aspect, the present invention provides a modified expansive soil, which is composed of the following components in parts by weight: 100 parts by weight of expansive soil; 6-8 parts by weight of phosphoric acid aqueous solution, 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate; water, wherein the amount of water used = the amount of water at the optimal water content - the water content in the phosphoric acid aqueous solution;

[0007] The concentration of the phosphoric acid aqueous solution is 85.54 wt %.

[0008] Preferably, the expansive soil has a plastic limit of 24.2%, a liquid limit of 112.2%, a free expansion rate of 105%, an optimum moisture content of 26.0% and a maximum dry density of 1.47 g / cm 3 .

[0009] On the other hand, the present invention also provides a method for preparing the modified expansive soil, comprising:

[0010] 1) Determine the optimum moisture content of mixed expansive soil (100 parts by weight of expansive soil; 6-8 parts by weight of phosphoric acid aqueous solution, 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate, and water (five points at intervals of 2% near the plastic limit)) by a light compaction test in accordance with the Highway Geotechnical Test Code JTG3430-2020;

[0011] 2) dissolving the sulfonated acetone formaldehyde polycondensate in water, and adding water according to the water content of the determined optimum water content minus the water content in the phosphoric acid aqueous solution;

[0012] 3) Add phosphoric acid aqueous solution to step 2), mix well and then add to the expansive soil, stir well and it is ready for use.

[0013] On the other hand, the present invention also provides an application of the modified expansive soil for use in the subbase or base layer of a highway.

[0014] Compared with the prior art, the present invention has the following beneficial effects:

[0015] The present invention selects phosphoric acid and water to be fully mixed, then adds sulfonated acetone formaldehyde condensate and stirs evenly, adds it to soil, stirs evenly, and can greatly improve the unconfined compressive strength of the soil, especially for soil containing a certain amount of bentonite. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 This is a compaction test data diagram of Example 1 of the present invention;

[0017] Figure 2 This is a compaction test data diagram of Comparative Example 2 of the present invention;

[0018] Figure 3 This is a compaction test data diagram of Comparative Example 9 of the present invention;

[0019] Figure 4 This is a compaction test data diagram of Comparative Example 20 of the present invention;

[0020] Figure 5 The unconfined compressive strength diagram of sodium-based bentonite reinforced with different amounts of SAF

[0021] Figure 6 The unconfined compressive strength diagram of sodium bentonite reinforced with different amounts of phosphoric acid aqueous solution;

[0022] Figure 7 This is the unconfined compressive strength diagram of sodium bentonite reinforced with 0.8% SAF and different amounts of phosphoric acid aqueous solution. DETAILED DESCRIPTION

[0023] In order to make the technical problems to be solved, technical solutions and advantages of the present invention more clear, a detailed description will be given below with reference to the accompanying drawings and specific embodiments.

[0024] In the present invention, the materials and reagents used are not specifically stated and can be obtained from commercial sources. The concentration of the phosphoric acid aqueous solution is 85.54wt%. Sulfonated acetone formaldehyde polycondensate was purchased from Chengdu Chuanfeng Chemical Engineering Co., Ltd.; the expansive soil used in the present invention is sodium bentonite, purchased from Zhan Teng Mineral Products Processing Plant, Lingshou County, Hebei Province, among which the particle size>0.075mm accounts for 10.89wt%, the particle size 0.005-0.075 mm accounts for 40.50 wt%, and the particle size <0.005 mm accounts for 48.61wt%.

[0025] The present invention provides a modified expansive soil and a preparation method and application thereof, and specific embodiments are as follows.

[0026] Example 1

[0027] A modified expansive soil is composed of the following components in parts by weight: 100 parts by weight of sodium bentonite; 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate (SAF); 8 parts by weight of phosphoric acid aqueous solution (PA) and 24.25 parts by weight of water.

[0028] The method for preparing the modified expansive soil for roadbed comprises:

[0029] 1) According to the light compaction test in "Highway Geotechnical Test Code" JTG3430-2020, the results are as follows Figure 1 As shown, the optimal moisture content of the mixed expansive soil (100 parts by weight of sodium bentonite; 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate (SAF); 8 parts by weight of phosphoric acid aqueous solution (PA), and water (five points were selected at intervals of 2% near the plastic limit)) was determined to be 25.41%;

[0030] 2) dissolving the sulfonated acetone formaldehyde polycondensate in water, and adding 24.25 parts by weight of water according to the water content of 25.41 parts by weight of the determined optimal water content minus the amount of water in the phosphoric acid aqueous solution (1.16 parts by weight);

[0031] 3) Add phosphoric acid aqueous solution to step 2), mix well and then add to sodium bentonite, stir well and then use.

[0032] Example 2

[0033] A modified expansive soil, composed of the following components in parts by weight: 100 parts by weight of sodium bentonite; 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate (SAF); 6 parts by weight of phosphoric acid aqueous solution (PA); and 26.33 parts by weight of water;

[0034] The preparation method is the same as that of Example 1, and the optimum moisture content is 24.2%.

[0035] In order to further illustrate the beneficial effects of the present invention, the following comparative example was constructed.

[0036] Comparative Examples 1-20

[0037] The dosage of each substance in Comparative Examples 1-20 is shown in Table 1, and the optimum moisture content is determined by compaction test. The compaction test data of Comparative Example 2 is shown in Table Figure 2 ; Comparative Example 9 compaction test data see Figure 3 ; Comparative Example 20 compaction test data see Figure 4 ; Then determine the amount of water to be added. The preparation method is the same as in Example 1.

[0038] Table 1

[0039]

[0040] The inventors used different amounts of substances in different embodiments and comparative examples, first mechanically stirred and mixed the curing agent and low liquid limit clay evenly, then added water, and mixed evenly again; then sealed with plastic wrap, stored for 12 hours, and then used a compression mold-demolding integrated machine to make a sample with a length of 100 mm and a diameter of 50 mm, and then carried out unconfined compressive strength, direct shear, shrinkage and expansion test specimens, and tested them. The specific process is as follows.

[0041] Unconfined compressive strength test

[0042] The test process was carried out using an unconfined compression apparatus model YAW-300D / 10D.

[0043] How to do it:

[0044] (1) Sample preparation: The material that has been simmered for 12 h is made into a sample with a length of 100 mm and a diameter of 50 mm using a press-molding and demolding machine, and the height is measured and the weight is weighed;

[0045] (2) Curing: All samples were cured in a standard curing box for 7 days at a temperature of 20 ± 2 °C and a relative humidity of 95 ± 3%.

[0046] (3) Test: The unconfined compressive strength machine parameters were adjusted to a loading speed of 1 mm / min. The procedure was based on the "Unconfined Compressive Strength Test for Inorganic Bonded Materials in Highway Engineering" [JTG E51-2009]. The test was conducted after the sample surface was scraped flat, the height was measured, and the mass was weighed. The results are shown in Tables 2-5 and Figure 5-7 In the figure, the dosage of phosphoric acid aqueous solution is the weight ratio of phosphoric acid aqueous solution to expansive soil; the dosage of SAF is the weight ratio of SAF to expansive soil.

[0047] Table 2

[0048]

[0049] It can be seen from Table 2 that the specific content of phosphoric acid aqueous solution and the specific content of SAF used as curing agent in the present invention can significantly improve the unconfined compressive strength of sodium bentonite.

[0050] Table 3

[0051]

[0052] From Table 3 and Figure 5 It can be seen that pure SAF can improve the unconfined compressive strength of sodium bentonite to a certain extent, but with the increase of SAF addition, the unconfined compressive strength first increases and then decreases, and the optimal dosage is 0.8% of the mass of sodium bentonite.

[0053] Table 4

[0054]

[0055] From Table 4 and Figure 6 It can be seen that simple phosphoric acid aqueous solution can also improve the unconfined compressive strength of sodium bentonite to a certain extent, but with the increase of the amount of phosphoric acid aqueous solution added, the unconfined compressive strength first increases and then decreases. The optimal dosage is 2-3% of the mass of sodium bentonite.

[0056] Table 5

[0057]

[0058] From Table 5 and Figure 7 It can be seen that the performance of the modified expansive soil prepared by the synergistic effect of different amounts of phosphoric acid aqueous solution and SAF is different. Although the optimal amount of phosphoric acid aqueous solution when used alone is 2-3% of the mass of sodium bentonite, when used in combination with SAF, the performance of the modified expansive soil prepared is the best when the amount of phosphoric acid aqueous solution is 6%-8%.

[0059] In summary, the present invention adopts sulfonated acetone formaldehyde condensation product and phosphoric acid as curing agents, and the unconfined compressive strength of the prepared modified expansive soil is greatly improved.

[0060] The above is a preferred embodiment of the present invention. For ordinary technicians in this technical field, making several improvements and modifications without departing from the principles of the present invention should also be regarded as within the protection scope of the present invention.

Claims

1. A modified expansive soil, characterized in that: The invention is composed of the following components in parts by weight: 100 parts by weight of expansive soil; 6-8 parts by weight of phosphoric acid aqueous solution, 0.8 parts by weight of sulfonated acetone formaldehyde polycondensate; and water, wherein the amount of water used is equal to the amount of water at the optimum water content minus the water content in the phosphoric acid aqueous solution. The concentration of the phosphoric acid aqueous solution is 85.54wt%; The expansive soil is sodium-based bentonite.

2. The method for preparing the modified expansive soil according to claim 1, characterized in that: include: 1) Determine the optimum moisture content of modified expansive soil by light compaction test in accordance with the Highway Geotechnical Test Code JTG3430-2020; 2) dissolving the sulfonated acetone formaldehyde polycondensate in water, the amount of water used being equal to the amount of water at the optimum water content minus the water content in the phosphoric acid aqueous solution; 3) Add phosphoric acid aqueous solution to step 2), mix well and then add to the expansive soil, stir well and it is ready for use.

3. The use of the modified expansive soil according to claim 1, characterized in that: Used for subbase or base layer of highway.

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